.

This PR implements the proof-by-reflection infrastructure for embedding
semiring terms as ring ones.

.github/workflows/awaiting-mathlib.yml

@@ -10,11 +10,29 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Check awaiting-mathlib label
+        id: check-awaiting-mathlib-label
         if: github.event_name == 'pull_request'
         uses: actions/github-script@v7
         with:
           script: |
-            const { labels } = context.payload.pull_request;
-            if (labels.some(label => label.name == "awaiting-mathlib") && !labels.some(label => label.name == "builds-mathlib")) {
-              core.setFailed('PR is marked "awaiting-mathlib" but "builds-mathlib" label has not been applied yet by the bot');
+            const { labels, number: prNumber } = context.payload.pull_request;
+            const hasAwaiting = labels.some(label => label.name == "awaiting-mathlib");
+            const hasBreaks = labels.some(label => label.name == "breaks-mathlib");
+            const hasBuilds = labels.some(label => label.name == "builds-mathlib");
+
+            if (hasAwaiting && hasBreaks) {
+              core.setFailed('PR has both "awaiting-mathlib" and "breaks-mathlib" labels.');
+            } else if (hasAwaiting && !hasBreaks && !hasBuilds) {
+              core.info('PR is marked "awaiting-mathlib" but neither "breaks-mathlib" nor "builds-mathlib" labels are present.');
+              core.setOutput('awaiting', 'true');
             }
+      
+      - name: Wait for mathlib compatibility
+        if: github.event_name == 'pull_request' && steps.check-awaiting-mathlib-label.outputs.awaiting == 'true'
+        run: |
+          echo "::notice title=Awaiting mathlib::PR is marked 'awaiting-mathlib' but neither 'breaks-mathlib' nor 'builds-mathlib' labels are present."
+          echo "This check will remain in progress until the PR is updated with appropriate mathlib compatibility labels."
+          # Keep the job running indefinitely to show "in progress" status
+          while true; do
+            sleep 3600  # Sleep for 1 hour at a time
+          done

.github/workflows/build-template.yml

@@ -82,7 +82,7 @@ jobs:
       - name: CI Merge Checkout
         run: |
           git fetch --depth=1 origin ${{ github.sha }}
-          git checkout FETCH_HEAD flake.nix flake.lock script/prepare-*
+          git checkout FETCH_HEAD flake.nix flake.lock script/prepare-* tests/lean/run/importStructure.lean
         if: github.event_name == 'pull_request'
       # (needs to be after "Checkout" so files don't get overridden)
       - name: Setup emsdk
@@ -104,12 +104,12 @@ jobs:
           # NOTE: must be in sync with `save` below
           path: |
             .ccache
-            ${{ matrix.name == 'Linux Lake' && 'build/stage1/**/*.trace
-            build/stage1/**/*.olean
+            ${{ matrix.name == 'Linux Lake' && false && 'build/stage1/**/*.trace
+            build/stage1/**/*.olean*
             build/stage1/**/*.ilean
             build/stage1/**/*.c
             build/stage1/**/*.c.o*' || '' }}
-          key: ${{ matrix.name }}-build-v3-${{ github.event.pull_request.head.sha }}
+          key: ${{ matrix.name }}-build-v3-${{ github.sha }}
           # fall back to (latest) previous cache
           restore-keys: |
             ${{ matrix.name }}-build-v3
@@ -127,9 +127,12 @@ jobs:
           [ -d build ] || mkdir build
           cd build
           # arguments passed to `cmake`
-          # this also enables githash embedding into stage 1 library
-          OPTIONS=(-DCHECK_OLEAN_VERSION=ON)
-          OPTIONS+=(-DLEAN_EXTRA_MAKE_OPTS=-DwarningAsError=true)
+          OPTIONS=(-DLEAN_EXTRA_MAKE_OPTS=-DwarningAsError=true)
+          if [[ -n '${{ matrix.release }}' ]]; then
+            # this also enables githash embedding into stage 1 library, which prohibits reusing
+            # `.olean`s across commits, so we don't do it in the fast non-release CI
+            OPTIONS+=(-DCHECK_OLEAN_VERSION=ON)
+          fi
           if [[ -n '${{ matrix.cross_target }}' ]]; then
             # used by `prepare-llvm`
             export EXTRA_FLAGS=--target=${{ matrix.cross_target }}
@@ -193,7 +196,7 @@ jobs:
         run: |
           ulimit -c unlimited  # coredumps
           time ctest --preset ${{ matrix.CMAKE_PRESET || 'release' }} --test-dir build/stage1 -j$NPROC --output-junit test-results.xml ${{ matrix.CTEST_OPTIONS }}
-        if: (matrix.wasm || !matrix.cross) && (inputs.check-level >= 1 || matrix.name == 'Linux release')
+        if: (matrix.wasm || !matrix.cross) && (inputs.check-level >= 1 || matrix.test)
       - name: Test Summary
         uses: test-summary/action@v2
         with:
@@ -210,7 +213,7 @@ jobs:
       - name: Check Stage 3
         run: |
           make -C build -j$NPROC check-stage3
-        if: matrix.test-speedcenter
+        if: matrix.check-stage3
       - name: Test Speedcenter Benchmarks
         run: |
           # Necessary for some timing metrics but does not work on Namespace runners
@@ -224,7 +227,7 @@ jobs:
         run: |
           # clean rebuild in case of Makefile changes
           make -C build update-stage0 && rm -rf build/stage* && make -C build -j$NPROC
-        if: matrix.name == 'Linux' && inputs.check-level >= 1
+        if: matrix.check-rebootstrap
       - name: CCache stats
         if: always()
         run: ccache -s
@@ -242,8 +245,8 @@ jobs:
           # NOTE: must be in sync with `restore` above
           path: |
             .ccache
-            ${{ matrix.name == 'Linux Lake' && 'build/stage1/**/*.trace
-            build/stage1/**/*.olean
+            ${{ matrix.name == 'Linux Lake' && false && 'build/stage1/**/*.trace
+            build/stage1/**/*.olean*
             build/stage1/**/*.ilean
             build/stage1/**/*.c
             build/stage1/**/*.c.o*' || '' }}

.github/workflows/ci.yml

@@ -103,6 +103,13 @@ jobs:
             echo "Tag ${TAG_NAME} did not match SemVer regex."
           fi
 
+      - name: Check for custom releases (e.g., not in the main lean repository)
+        if: startsWith(github.ref, 'refs/tags/') && github.repository != 'leanprover/lean4'
+        id: set-release-custom
+        run: |
+          TAG_NAME="${GITHUB_REF##*/}"
+          echo "RELEASE_TAG=$TAG_NAME" >> "$GITHUB_OUTPUT"
+
       - name: Set check level
         id: set-level
         # We do not use github.event.pull_request.labels.*.name here because
@@ -111,7 +118,7 @@ jobs:
         run: |
           check_level=0
 
-          if [[ -n "${{ steps.set-nightly.outputs.nightly }}" || -n "${{ steps.set-release.outputs.RELEASE_TAG }}" ]]; then
+          if [[ -n "${{ steps.set-nightly.outputs.nightly }}" || -n "${{ steps.set-release.outputs.RELEASE_TAG }}" || -n "${{ steps.set-release-custom.outputs.RELEASE_TAG }}" ]]; then
             check_level=2
           elif [[ "${{ github.event_name }}" != "pull_request" ]]; then
             check_level=1
@@ -157,9 +164,15 @@ jobs:
               {
                 // portable release build: use channel with older glibc (2.26)
                 "name": "Linux release",
-                "os": large ? "nscloud-ubuntu-22.04-amd64-4x8" : "ubuntu-latest",
+                "os": large && level < 2 ? "nscloud-ubuntu-22.04-amd64-4x16" : "ubuntu-latest",
                 "release": true,
-                "check-level": 0,
+                // Special handling for release jobs. We want:
+                // 1. To run it in PRs so developrs get PR toolchains (so secondary is sufficient)
+                // 2. To skip it in merge queues as it takes longer than the
+                //    Linux lake build and adds little value in the merge queue
+                // 3. To run it in release (obviously)
+                "check-level": isPr ? 0 : 2,
+                "secondary": isPr,
                 "shell": "nix develop .#oldGlibc -c bash -euxo pipefail {0}",
                 "llvm-url": "https://github.com/leanprover/lean-llvm/releases/download/19.1.2/lean-llvm-x86_64-linux-gnu.tar.zst",
                 "prepare-llvm": "../script/prepare-llvm-linux.sh lean-llvm*",
@@ -169,21 +182,14 @@ jobs:
               },
               {
                 "name": "Linux Lake",
-                "os": large ? "nscloud-ubuntu-22.04-amd64-4x8" : "ubuntu-latest",
+                "os": large ? "nscloud-ubuntu-22.04-amd64-8x16" : "ubuntu-latest",
                 "check-level": 0,
-                // just a secondary build job for now until false positives can be excluded
-                "secondary": true,
-                "CMAKE_OPTIONS": "-DUSE_LAKE=ON",
-                // TODO: importStructure is not compatible with .olean caching
-                // TODO: why does scopedMacros fail?
-                "CTEST_OPTIONS": "-E 'scopedMacros|importStructure'"
-              },
-              {
-                "name": "Linux",
-                "os": large ? "nscloud-ubuntu-22.04-amd64-4x8" : "ubuntu-latest",
+                "test": true,
+                "check-rebootstrap": level >= 1,
                 "check-stage3": level >= 2,
-                "test-speedcenter": level >= 2,
-                "check-level": 1,
+                // NOTE: `test-speedcenter` currently seems to be broken on `ubuntu-latest`
+                "test-speedcenter": large && level >= 2,
+                "CMAKE_OPTIONS": "-DUSE_LAKE=ON",
               },
               {
                 "name": "Linux Reldebug",
@@ -216,7 +222,8 @@ jobs:
               },
               {
                 "name": "macOS aarch64",
-                "os": "macos-14",
+                // standard GH runner only comes with 7GB so use large runner if possible
+                "os": large ? "nscloud-macos-sonoma-arm64-6x14" : "macos-14",
                 "CMAKE_OPTIONS": "-DLEAN_INSTALL_SUFFIX=-darwin_aarch64",
                 "release": true,
                 "shell": "bash -euxo pipefail {0}",
@@ -224,11 +231,7 @@ jobs:
                 "prepare-llvm": "../script/prepare-llvm-macos.sh lean-llvm*",
                 "binary-check": "otool -L",
                 "tar": "gtar", // https://github.com/actions/runner-images/issues/2619
-                // Special handling for MacOS aarch64, we want:
-                // 1. To run it in PRs so Mac devs get PR toolchains (so secondary is sufficient)
-                // 2. To skip it in merge queues as it takes longer than the Linux build and adds
-                //    little value in the merge queue
-                // 3. To run it in release (obviously)
+                // See above for release job levels
                 "check-level": isPr ? 0 : 2,
                 "secondary": isPr,
               },
@@ -247,7 +250,7 @@ jobs:
               },
               {
                 "name": "Linux aarch64",
-                "os": "nscloud-ubuntu-22.04-arm64-4x8",
+                "os": "nscloud-ubuntu-22.04-arm64-4x16",
                 "CMAKE_OPTIONS": "-DLEAN_INSTALL_SUFFIX=-linux_aarch64",
                 "release": true,
                 "check-level": 2,
@@ -357,7 +360,7 @@ jobs:
         with:
           path: artifacts
       - name: Release
-        uses: softprops/action-gh-release@v2
+        uses: softprops/action-gh-release@da05d552573ad5aba039eaac05058a918a7bf631
         with:
           files: artifacts/*/*
           fail_on_unmatched_files: true
@@ -401,7 +404,7 @@ jobs:
           echo -e "\n*Full commit log*\n" >> diff.md
           git log --oneline "$last_tag"..HEAD | sed 's/^/* /' >> diff.md
       - name: Release Nightly
-        uses: softprops/action-gh-release@v2
+        uses: softprops/action-gh-release@da05d552573ad5aba039eaac05058a918a7bf631
         with:
           body_path: diff.md
           prerelease: true

.github/workflows/pr-release.yml

@@ -34,7 +34,7 @@ jobs:
       - name: Download artifact from the previous workflow.
         if: ${{ steps.workflow-info.outputs.pullRequestNumber != '' }}
         id: download-artifact
-        uses: dawidd6/action-download-artifact@v9 # https://github.com/marketplace/actions/download-workflow-artifact
+        uses: dawidd6/action-download-artifact@v10 # https://github.com/marketplace/actions/download-workflow-artifact
         with:
           run_id: ${{ github.event.workflow_run.id }}
           path: artifacts
@@ -48,19 +48,30 @@ jobs:
           git -C lean4.git remote add origin https://github.com/${{ github.repository_owner }}/lean4.git
           git -C lean4.git fetch -n origin master
           git -C lean4.git fetch -n origin "${{ steps.workflow-info.outputs.sourceHeadSha }}"
+          
+          # Create both the original tag and the SHA-suffixed tag
+          SHORT_SHA="${{ steps.workflow-info.outputs.sourceHeadSha }}"
+          SHORT_SHA="${SHORT_SHA:0:7}"
+          
+          # Export the short SHA for use in subsequent steps
+          echo "SHORT_SHA=${SHORT_SHA}" >> "$GITHUB_ENV"
+
           git -C lean4.git tag -f pr-release-${{ steps.workflow-info.outputs.pullRequestNumber }} "${{ steps.workflow-info.outputs.sourceHeadSha }}"
+          git -C lean4.git tag -f pr-release-${{ steps.workflow-info.outputs.pullRequestNumber }}-"${SHORT_SHA}" "${{ steps.workflow-info.outputs.sourceHeadSha }}"
+          
           git -C lean4.git remote add pr-releases https://foo:'${{ secrets.PR_RELEASES_TOKEN }}'@github.com/${{ github.repository_owner }}/lean4-pr-releases.git
           git -C lean4.git push -f pr-releases pr-release-${{ steps.workflow-info.outputs.pullRequestNumber }}
+          git -C lean4.git push -f pr-releases pr-release-${{ steps.workflow-info.outputs.pullRequestNumber }}-"${SHORT_SHA}"
       - name: Delete existing release if present
         if: ${{ steps.workflow-info.outputs.pullRequestNumber != '' }}
         run: |
-          # Try to delete any existing release for the current PR.
+          # Try to delete any existing release for the current PR (just the version without the SHA suffix).
           gh release delete --repo ${{ github.repository_owner }}/lean4-pr-releases pr-release-${{ steps.workflow-info.outputs.pullRequestNumber }} -y || true
         env:
           GH_TOKEN: ${{ secrets.PR_RELEASES_TOKEN }}
-      - name: Release
+      - name: Release (short format)
         if: ${{ steps.workflow-info.outputs.pullRequestNumber != '' }}
-        uses: softprops/action-gh-release@v2
+        uses: softprops/action-gh-release@da05d552573ad5aba039eaac05058a918a7bf631
         with:
           name: Release for PR ${{ steps.workflow-info.outputs.pullRequestNumber }}
           # There are coredumps files here as well, but all in deeper subdirectories.
@@ -73,7 +84,22 @@ jobs:
           # The token used here must have `workflow` privileges.
           GITHUB_TOKEN: ${{ secrets.PR_RELEASES_TOKEN }}
 
-      - name: Report release status
+      - name: Release (SHA-suffixed format)
+        if: ${{ steps.workflow-info.outputs.pullRequestNumber != '' }}
+        uses: softprops/action-gh-release@da05d552573ad5aba039eaac05058a918a7bf631
+        with:
+          name: Release for PR ${{ steps.workflow-info.outputs.pullRequestNumber }} (${{ steps.workflow-info.outputs.sourceHeadSha }})
+          # There are coredumps files here as well, but all in deeper subdirectories.
+          files: artifacts/*/*
+          fail_on_unmatched_files: true
+          draft: false
+          tag_name: pr-release-${{ steps.workflow-info.outputs.pullRequestNumber }}-${{ env.SHORT_SHA }}
+          repository: ${{ github.repository_owner }}/lean4-pr-releases
+        env:
+          # The token used here must have `workflow` privileges.
+          GITHUB_TOKEN: ${{ secrets.PR_RELEASES_TOKEN }}
+
+      - name: Report release status (short format)
         if: ${{ steps.workflow-info.outputs.pullRequestNumber != '' }}
         uses: actions/github-script@v7
         with:
@@ -87,6 +113,20 @@ jobs:
               description: "${{ github.repository_owner }}/lean4-pr-releases:pr-release-${{ steps.workflow-info.outputs.pullRequestNumber }}",
             });
 
+      - name: Report release status (SHA-suffixed format)
+        if: ${{ steps.workflow-info.outputs.pullRequestNumber != '' }}
+        uses: actions/github-script@v7
+        with:
+          script: |
+            await github.rest.repos.createCommitStatus({
+              owner: context.repo.owner,
+              repo: context.repo.repo,
+              sha: "${{ steps.workflow-info.outputs.sourceHeadSha }}",
+              state: "success",
+              context: "PR toolchain (SHA-suffixed)",
+              description: "${{ github.repository_owner }}/lean4-pr-releases:pr-release-${{ steps.workflow-info.outputs.pullRequestNumber }}-${{ env.SHORT_SHA }}",
+            });
+
       - name: Add label
         if: ${{ steps.workflow-info.outputs.pullRequestNumber != '' }}
         uses: actions/github-script@v7
@@ -282,16 +322,18 @@ jobs:
           if [ "$EXISTS" = "0" ]; then
             echo "Branch does not exist, creating it."
             git switch -c lean-pr-testing-${{ steps.workflow-info.outputs.pullRequestNumber }} "$BASE"
-            echo "leanprover/lean4-pr-releases:pr-release-${{ steps.workflow-info.outputs.pullRequestNumber }}" > lean-toolchain
+            echo "leanprover/lean4-pr-releases:pr-release-${{ steps.workflow-info.outputs.pullRequestNumber }}-${{ env.SHORT_SHA }}" > lean-toolchain
             git add lean-toolchain
             git commit -m "Update lean-toolchain for testing https://github.com/leanprover/lean4/pull/${{ steps.workflow-info.outputs.pullRequestNumber }}"
           else
-            echo "Branch already exists, pushing an empty commit."
+            echo "Branch already exists, updating lean-toolchain."
             git switch lean-pr-testing-${{ steps.workflow-info.outputs.pullRequestNumber }}
             # The Batteries `nightly-testing` or `nightly-testing-YYYY-MM-DD` branch may have moved since this branch was created, so merge their changes.
             # (This should no longer be possible once `nightly-testing-YYYY-MM-DD` is a tag, but it is still safe to merge.)
             git merge "$BASE" --strategy-option ours --no-commit --allow-unrelated-histories
-            git commit --allow-empty -m "Trigger CI for https://github.com/leanprover/lean4/pull/${{ steps.workflow-info.outputs.pullRequestNumber }}"
+            echo "leanprover/lean4-pr-releases:pr-release-${{ steps.workflow-info.outputs.pullRequestNumber }}-${{ env.SHORT_SHA }}" > lean-toolchain
+            git add lean-toolchain
+            git commit -m "Update lean-toolchain for https://github.com/leanprover/lean4/pull/${{ steps.workflow-info.outputs.pullRequestNumber }}"
           fi
 
       - name: Push changes
@@ -346,21 +388,23 @@ jobs:
           if [ "$EXISTS" = "0" ]; then
             echo "Branch does not exist, creating it."
             git switch -c lean-pr-testing-${{ steps.workflow-info.outputs.pullRequestNumber }} "$BASE"
-            echo "leanprover/lean4-pr-releases:pr-release-${{ steps.workflow-info.outputs.pullRequestNumber }}" > lean-toolchain
+            echo "leanprover/lean4-pr-releases:pr-release-${{ steps.workflow-info.outputs.pullRequestNumber }}-${{ env.SHORT_SHA }}" > lean-toolchain
             git add lean-toolchain
             sed -i 's,require "leanprover-community" / "batteries" @ git ".\+",require "leanprover-community" / "batteries" @ git "lean-pr-testing-${{ steps.workflow-info.outputs.pullRequestNumber }}",' lakefile.lean
             lake update batteries
             git add lakefile.lean lake-manifest.json
             git commit -m "Update lean-toolchain for testing https://github.com/leanprover/lean4/pull/${{ steps.workflow-info.outputs.pullRequestNumber }}"
           else
-            echo "Branch already exists, merging $BASE and bumping Batteries."
+            echo "Branch already exists, updating lean-toolchain and bumping Batteries."
             git switch lean-pr-testing-${{ steps.workflow-info.outputs.pullRequestNumber }}
             # The Mathlib `nightly-testing` branch or `nightly-testing-YYYY-MM-DD` tag may have moved since this branch was created, so merge their changes.
             # (This should no longer be possible once `nightly-testing-YYYY-MM-DD` is a tag, but it is still safe to merge.)
             git merge "$BASE" --strategy-option ours --no-commit --allow-unrelated-histories
+            echo "leanprover/lean4-pr-releases:pr-release-${{ steps.workflow-info.outputs.pullRequestNumber }}-${{ env.SHORT_SHA }}" > lean-toolchain
+            git add lean-toolchain
             lake update batteries
             git add lake-manifest.json
-            git commit --allow-empty -m "Trigger CI for https://github.com/leanprover/lean4/pull/${{ steps.workflow-info.outputs.pullRequestNumber }}"
+            git commit -m "Update lean-toolchain for https://github.com/leanprover/lean4/pull/${{ steps.workflow-info.outputs.pullRequestNumber }}"
           fi
 
       - name: Push changes

.github/workflows/update-stage0.yml

@@ -40,34 +40,24 @@ jobs:
       run: |
           git config --global user.name "Lean stage0 autoupdater"
           git config --global user.email "<>"
-    # Would be nice, but does not work yet:
-    # https://github.com/DeterminateSystems/magic-nix-cache/issues/39
-    # This action does not run that often and building runs in a few minutes, so ok for now
-    #- if: env.should_update_stage0 == 'yes'
-    #  uses: DeterminateSystems/magic-nix-cache-action@v2
-    - if: env.should_update_stage0 == 'yes'
-      name: Restore Build Cache
-      uses: actions/cache/restore@v4
-      with:
-        path: nix-store-cache
-        key: Nix Linux-nix-store-cache-${{ github.sha }}
-        # fall back to (latest) previous cache
-        restore-keys: |
-          Nix Linux-nix-store-cache
-    - if: env.should_update_stage0 == 'yes'
-      name: Further Set Up Nix Cache
-      shell: bash -euxo pipefail {0}
-      run: |
-        # Nix seems to mutate the cache, so make a copy
-        cp -r nix-store-cache nix-store-cache-copy || true
     - if: env.should_update_stage0 == 'yes'
       name: Install Nix
       uses: DeterminateSystems/nix-installer-action@main
-      with:
-        extra-conf: |
-          substituters = file://${{ github.workspace }}/nix-store-cache-copy?priority=10&trusted=true https://cache.nixos.org  
+    - name: Open Nix shell once
+      if: env.should_update_stage0 == 'yes'
+      run: true
+      shell: 'nix develop -c bash -euxo pipefail {0}'
+    - name: Set up NPROC
+      if: env.should_update_stage0 == 'yes'
+      run: |
+        echo "NPROC=$(nproc 2>/dev/null || sysctl -n hw.logicalcpu 2>/dev/null || echo 4)" >> $GITHUB_ENV
+      shell: 'nix develop -c bash -euxo pipefail {0}'
     - if: env.should_update_stage0 == 'yes'
-      run: nix run .#update-stage0-commit
+      run: cmake --preset release
+      shell: 'nix develop -c bash -euxo pipefail {0}'
+    - if: env.should_update_stage0 == 'yes'
+      run: make -j$NPROC -C build/release  update-stage0-commit
+      shell: 'nix develop -c bash -euxo pipefail {0}'
     - if: env.should_update_stage0 == 'yes'
       run: git show --stat
     - if: env.should_update_stage0 == 'yes' && github.event_name == 'push'

doc/dev/release_checklist.md

@@ -50,7 +50,7 @@ We'll use `v4.6.0` as the intended release version as a running example.
     - Re-running `script/release_checklist.py` will then create the tag `v4.6.0` from `master`/`main` and push it (unless `toolchain-tag: false` in the `release_repos.yml` file)
     - `script/release_checklist.py` will then merge the tag `v4.6.0` into the `stable` branch and push it (unless `stable-branch: false` in the `release_repos.yml` file).
   - Special notes on repositories with exceptional requirements:
-    - `doc-gen4` has addition dependencies which we do not update at each toolchain release, although occasionally these break and need to be updated manually.
+    - `doc-gen4` has additional dependencies which we do not update at each toolchain release, although occasionally these break and need to be updated manually.
     - `verso`:
       - The `subverso` dependency is unusual in that it needs to be compatible with _every_ Lean release simultaneously.
         Usually you don't need to do anything.
@@ -94,6 +94,8 @@ We'll use `v4.6.0` as the intended release version as a running example.
 
 This checklist walks you through creating the first release candidate for a version of Lean.
 
+For subsequent release candidates, the process is essentially the same, but we start out with the `releases/v4.7.0` branch already created.
+
 We'll use `v4.7.0-rc1` as the intended release version in this example.
 
 - Decide which nightly release you want to turn into a release candidate.
@@ -112,7 +114,7 @@ We'll use `v4.7.0-rc1` as the intended release version in this example.
     git fetch nightly tag nightly-2024-02-29
     git checkout nightly-2024-02-29
     git checkout -b releases/v4.7.0
-    git push --set-upstream origin releases/v4.18.0
+    git push --set-upstream origin releases/v4.7.0
     ```
 - In `src/CMakeLists.txt`,
   - verify that you see `set(LEAN_VERSION_MINOR 7)` (for whichever `7` is appropriate); this should already have been updated when the development cycle began.

script/bench.sh

@@ -0,0 +1,9 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+# We benchmark against stage 2 to test new optimizations.
+timeout -s KILL 1h time bash -c 'mkdir -p build/release; cd build/release; cmake ../.. && make -j$(nproc) stage2' 1>&2
+export PATH=$PWD/build/release/stage2/bin:$PATH
+cd tests/bench
+timeout -s KILL 1h time temci exec --config speedcenter.yaml --in speedcenter.exec.velcom.yaml 1>&2
+temci report run_output.yaml --reporter codespeed2

script/release_checklist.py

@@ -53,6 +53,23 @@ def tag_exists(repo_url, tag_name, github_token):
     matching_tags = response.json()
     return any(tag["ref"] == f"refs/tags/{tag_name}" for tag in matching_tags)
 
+def commit_hash_for_tag(repo_url, tag_name, github_token):
+    # Use /git/matching-refs/tags/ to get all matching tags
+    api_url = repo_url.replace("https://github.com/", "https://api.github.com/repos/") + f"/git/matching-refs/tags/{tag_name}"
+    headers = {'Authorization': f'token {github_token}'} if github_token else {}
+    response = requests.get(api_url, headers=headers)
+
+    if response.status_code != 200:
+        return False
+
+    # Check if any of the returned refs exactly match our tag
+    matching_tags = response.json()
+    matching_commits = [tag["object"]["sha"] for tag in matching_tags if tag["ref"] == f"refs/tags/{tag_name}"]
+    if len(matching_commits) != 1:
+        return None
+    else:
+        return matching_commits[0]
+
 def release_page_exists(repo_url, tag_name, github_token):
     api_url = repo_url.replace("https://github.com/", "https://api.github.com/repos/") + f"/releases/tags/{tag_name}"
     headers = {'Authorization': f'token {github_token}'} if github_token else {}
@@ -286,6 +303,14 @@ def main():
         lean4_success = False
     else:
         print(f"  ✅ Tag {toolchain} exists")
+        commit_hash = commit_hash_for_tag(lean_repo_url, toolchain, github_token)
+        SHORT_HASH_LENGTH = 7 # Lake abbreviates the Lean commit to 7 characters.
+        if commit_hash is None:
+            print(f"  ❌ Could not resolve tag {toolchain} to a commit.")
+            lean4_success = False
+        elif commit_hash[0] == '0' and commit_hash[:SHORT_HASH_LENGTH].isnumeric():
+            print(f"  ❌ Short commit hash {commit_hash[:SHORT_HASH_LENGTH]} is numeric and starts with 0, causing issues for version parsing. Try regenerating the last commit to get a new hash.")
+            lean4_success = False
 
     if not release_page_exists(lean_repo_url, toolchain, github_token):
         print(f"  ❌ Release page for {toolchain} does not exist")

script/release_steps.py

@@ -94,6 +94,7 @@ def generate_script(repo, version, config):
             "echo 'This repo has nightly-testing infrastructure'",
             f"git merge origin/bump/{version.split('-rc')[0]}",
             "echo 'Please resolve any conflicts.'",
+            "grep nightly-testing lakefile.* && echo 'Please ensure the lakefile does not include nightly-testing versions.'",
             ""
         ])
     if re.search(r'rc\d+$', version) and repo_name in ["verso", "reference-manual"]:

src/CMakeLists.txt

@@ -10,7 +10,7 @@ endif()
 include(ExternalProject)
 project(LEAN CXX C)
 set(LEAN_VERSION_MAJOR 4)
-set(LEAN_VERSION_MINOR 21)
+set(LEAN_VERSION_MINOR 22)
 set(LEAN_VERSION_PATCH 0)
 set(LEAN_VERSION_IS_RELEASE 0)  # This number is 1 in the release revision, and 0 otherwise.
 set(LEAN_SPECIAL_VERSION_DESC "" CACHE STRING "Additional version description like 'nightly-2018-03-11'")

src/Init.lean

@@ -37,6 +37,7 @@ import Init.Ext
 import Init.Omega
 import Init.MacroTrace
 import Init.Grind
+import Init.GrindInstances
 import Init.While
 import Init.Syntax
 import Init.Internal

src/Init/Coe.lean

@@ -7,6 +7,7 @@ module
 
 prelude
 import Init.Prelude
+meta import Init.Prelude
 set_option linter.missingDocs true -- keep it documented
 
 /-!

src/Init/Control/Basic.lean

@@ -49,7 +49,7 @@ abbrev forIn_eq_forin' := @forIn_eq_forIn'
 /--
 Extracts the value from a `ForInStep`, ignoring whether it is `ForInStep.done` or `ForInStep.yield`.
 -/
-def ForInStep.value (x : ForInStep α) : α :=
+@[expose] def ForInStep.value (x : ForInStep α) : α :=
   match x with
   | ForInStep.done b => b
   | ForInStep.yield b => b

src/Init/Control/Except.lean

@@ -136,7 +136,7 @@ may throw the corresponding exception.
 
 This is the inverse of `ExceptT.run`.
 -/
-@[always_inline, inline]
+@[always_inline, inline, expose]
 def ExceptT.mk {ε : Type u} {m : Type u → Type v} {α : Type u} (x : m (Except ε α)) : ExceptT ε m α := x
 
 /--
@@ -144,7 +144,7 @@ Use a monadic action that may throw an exception as an action that may return an
 
 This is the inverse of `ExceptT.mk`.
 -/
-@[always_inline, inline]
+@[always_inline, inline, expose]
 def ExceptT.run {ε : Type u} {m : Type u → Type v} {α : Type u} (x : ExceptT ε m α) : m (Except ε α) := x
 
 namespace ExceptT
@@ -154,14 +154,14 @@ variable {ε : Type u} {m : Type u → Type v} [Monad m]
 /--
 Returns the value `a` without throwing exceptions or having any other effect.
 -/
-@[always_inline, inline]
+@[always_inline, inline, expose]
 protected def pure {α : Type u} (a : α) : ExceptT ε m α :=
   ExceptT.mk <| pure (Except.ok a)
 
 /--
 Handles exceptions thrown by an action that can have no effects _other_ than throwing exceptions.
 -/
-@[always_inline, inline]
+@[always_inline, inline, expose]
 protected def bindCont {α β : Type u} (f : α → ExceptT ε m β) : Except ε α → m (Except ε β)
   | Except.ok a    => f a
   | Except.error e => pure (Except.error e)
@@ -170,14 +170,14 @@ protected def bindCont {α β : Type u} (f : α → ExceptT ε m β) : Except ε
 Sequences two actions that may throw exceptions. Typically used via `do`-notation or the `>>=`
 operator.
 -/
-@[always_inline, inline]
+@[always_inline, inline, expose]
 protected def bind {α β : Type u} (ma : ExceptT ε m α) (f : α → ExceptT ε m β) : ExceptT ε m β :=
   ExceptT.mk <| ma >>= ExceptT.bindCont f
 
 /--
 Transforms a successful computation's value using `f`. Typically used via the `<$>` operator.
 -/
-@[always_inline, inline]
+@[always_inline, inline, expose]
 protected def map {α β : Type u} (f : α → β) (x : ExceptT ε m α) : ExceptT ε m β :=
   ExceptT.mk <| x >>= fun a => match a with
     | (Except.ok a)    => pure <| Except.ok (f a)
@@ -186,7 +186,7 @@ protected def map {α β : Type u} (f : α → β) (x : ExceptT ε m α) : Excep
 /--
 Runs a computation from an underlying monad in the transformed monad with exceptions.
 -/
-@[always_inline, inline]
+@[always_inline, inline, expose]
 protected def lift {α : Type u} (t : m α) : ExceptT ε m α :=
   ExceptT.mk <| Except.ok <$> t
 
@@ -197,7 +197,7 @@ instance : MonadLift m (ExceptT ε m) := ⟨ExceptT.lift⟩
 /--
 Handles exceptions produced in the `ExceptT ε` transformer.
 -/
-@[always_inline, inline]
+@[always_inline, inline, expose]
 protected def tryCatch {α : Type u} (ma : ExceptT ε m α) (handle : ε → ExceptT ε m α) : ExceptT ε m α :=
   ExceptT.mk <| ma >>= fun res => match res with
    | Except.ok a    => pure (Except.ok a)

src/Init/Control/ExceptCps.lean

@@ -25,7 +25,7 @@ namespace ExceptCpsT
 /--
 Use a monadic action that may throw an exception as an action that may return an exception's value.
 -/
-@[always_inline, inline]
+@[always_inline, inline, expose]
 def run {ε α : Type u} [Monad m] (x : ExceptCpsT ε m α) : m (Except ε α) :=
   x _ (fun a => pure (Except.ok a)) (fun e => pure (Except.error e))
 
@@ -43,7 +43,7 @@ Returns the value of a computation, forgetting whether it was an exception or a
 
 This corresponds to early return.
 -/
-@[always_inline, inline]
+@[always_inline, inline, expose]
 def runCatch [Monad m] (x : ExceptCpsT α m α) : m α :=
   x α pure pure
 
@@ -63,7 +63,7 @@ instance : MonadExceptOf ε (ExceptCpsT ε m) where
 /--
 Run an action from the transformed monad in the exception monad.
 -/
-@[always_inline, inline]
+@[always_inline, inline, expose]
 def lift [Monad m] (x : m α) : ExceptCpsT ε m α :=
   fun _ k _ => x >>= k
 

src/Init/Control/Lawful.lean

@@ -9,3 +9,4 @@ prelude
 import Init.Control.Lawful.Basic
 import Init.Control.Lawful.Instances
 import Init.Control.Lawful.Lemmas
+import Init.Control.Lawful.MonadLift

src/Init/Control/Lawful/Basic.lean

@@ -6,6 +6,7 @@ Authors: Sebastian Ullrich, Leonardo de Moura, Mario Carneiro
 module
 
 prelude
+import Init.Ext
 import Init.SimpLemmas
 import Init.Meta
 
@@ -147,7 +148,7 @@ attribute [simp] pure_bind bind_assoc bind_pure_comp
 attribute [grind] pure_bind
 
 @[simp] theorem bind_pure [Monad m] [LawfulMonad m] (x : m α) : x >>= pure = x := by
-  show x >>= (fun a => pure (id a)) = x
+  change x >>= (fun a => pure (id a)) = x
   rw [bind_pure_comp, id_map]
 
 /--
@@ -241,13 +242,23 @@ theorem LawfulMonad.mk' (m : Type u → Type v) [Monad m]
 
 namespace Id
 
-@[simp] theorem map_eq (x : Id α) (f : α → β) : f <$> x = f x := rfl
-@[simp] theorem bind_eq (x : Id α) (f : α → id β) : x >>= f = f x := rfl
-@[simp] theorem pure_eq (a : α) : (pure a : Id α) = a := rfl
+@[ext] theorem ext {x y : Id α} (h : x.run = y.run) : x = y := h
 
 instance : LawfulMonad Id := by
   refine LawfulMonad.mk' _ ?_ ?_ ?_ <;> intros <;> rfl
 
+@[simp] theorem run_map (x : Id α) (f : α → β) : (f <$> x).run = f x.run := rfl
+@[simp] theorem run_bind (x : Id α) (f : α → Id β) : (x >>= f).run = (f x.run).run := rfl
+@[simp] theorem run_pure (a : α) : (pure a : Id α).run = a := rfl
+@[simp] theorem run_seqRight (x y : Id α) : (x *> y).run = y.run := rfl
+@[simp] theorem run_seqLeft (x y : Id α) : (x <* y).run = x.run := rfl
+@[simp] theorem run_seq (f : Id (α → β)) (x : Id α) : (f <*> x).run = f.run x.run := rfl
+
+-- These lemmas are bad as they abuse the defeq of `Id α` and `α`
+@[deprecated run_map (since := "2025-03-05")] theorem map_eq (x : Id α) (f : α → β) : f <$> x = f x := rfl
+@[deprecated run_bind (since := "2025-03-05")] theorem bind_eq (x : Id α) (f : α → id β) : x >>= f = f x := rfl
+@[deprecated run_pure (since := "2025-03-05")] theorem pure_eq (a : α) : (pure a : Id α) = a := rfl
+
 end Id
 
 /-! # Option -/

src/Init/Control/Lawful/Instances.lean

@@ -58,7 +58,7 @@ protected theorem bind_pure_comp [Monad m] (f : α → β) (x : ExceptT ε m α)
   intros; rfl
 
 protected theorem seqLeft_eq {α β ε : Type u} {m : Type u → Type v} [Monad m] [LawfulMonad m] (x : ExceptT ε m α) (y : ExceptT ε m β) : x <* y = const β <$> x <*> y := by
-  show (x >>= fun a => y >>= fun _ => pure a) = (const (α := α) β <$> x) >>= fun f => f <$> y
+  change (x >>= fun a => y >>= fun _ => pure a) = (const (α := α) β <$> x) >>= fun f => f <$> y
   rw [← ExceptT.bind_pure_comp]
   apply ext
   simp [run_bind]
@@ -70,7 +70,7 @@ protected theorem seqLeft_eq {α β ε : Type u} {m : Type u → Type v} [Monad
     cases b <;> simp [comp, Except.map, const]
 
 protected theorem seqRight_eq [Monad m] [LawfulMonad m] (x : ExceptT ε m α) (y : ExceptT ε m β) : x *> y = const α id <$> x <*> y := by
-  show (x >>= fun _ => y) = (const α id <$> x) >>= fun f => f <$> y
+  change (x >>= fun _ => y) = (const α id <$> x) >>= fun f => f <$> y
   rw [← ExceptT.bind_pure_comp]
   apply ext
   simp [run_bind]
@@ -206,15 +206,15 @@ theorem run_bind_lift {α σ : Type u} [Monad m] [LawfulMonad m] (x : m α) (f :
     (monadMap @f x : StateT σ m α).run s = monadMap @f (x.run s) := rfl
 
 @[simp] theorem run_seq {α β σ : Type u} [Monad m] [LawfulMonad m] (f : StateT σ m (α → β)) (x : StateT σ m α) (s : σ) : (f <*> x).run s = (f.run s >>= fun fs => (fun (p : α × σ) => (fs.1 p.1, p.2)) <$> x.run fs.2) := by
-  show (f >>= fun g => g <$> x).run s = _
+  change (f >>= fun g => g <$> x).run s = _
   simp
 
 @[simp] theorem run_seqRight [Monad m] (x : StateT σ m α) (y : StateT σ m β) (s : σ) : (x *> y).run s = (x.run s >>= fun p => y.run p.2) := by
-  show (x >>= fun _ => y).run s = _
+  change (x >>= fun _ => y).run s = _
   simp
 
 @[simp] theorem run_seqLeft {α β σ : Type u} [Monad m] (x : StateT σ m α) (y : StateT σ m β) (s : σ) : (x <* y).run s = (x.run s >>= fun p => y.run p.2 >>= fun p' => pure (p.1, p'.2)) := by
-  show (x >>= fun a => y >>= fun _ => pure a).run s = _
+  change (x >>= fun a => y >>= fun _ => pure a).run s = _
   simp
 
 theorem seqRight_eq [Monad m] [LawfulMonad m] (x : StateT σ m α) (y : StateT σ m β) : x *> y = const α id <$> x <*> y := by

src/Init/Control/Lawful/MonadLift.lean

@@ -0,0 +1,11 @@
+/-
+Copyright (c) 2025 Lean FRO, LLC. All rights reserved.
+Released under Apache 2.0 license as described in the file LICENSE.
+Authors: Paul Reichert
+-/
+module
+
+prelude
+import Init.Control.Lawful.MonadLift.Basic
+import Init.Control.Lawful.MonadLift.Lemmas
+import Init.Control.Lawful.MonadLift.Instances

src/Init/Control/Lawful/MonadLift/Basic.lean

@@ -0,0 +1,52 @@
+/-
+Copyright (c) 2025 Quang Dao. All rights reserved.
+Released under Apache 2.0 license as described in the file LICENSE.
+Authors: Quang Dao
+-/
+module
+
+prelude
+import Init.Control.Basic
+
+/-!
+# LawfulMonadLift and LawfulMonadLiftT
+
+This module provides classes asserting that `MonadLift` and `MonadLiftT` are lawful, which means
+that `monadLift` is compatible with `pure` and `bind`.
+-/
+
+section MonadLift
+
+/-- The `MonadLift` typeclass only contains the lifting operation. `LawfulMonadLift` further
+  asserts that lifting commutes with `pure` and `bind`:
+```
+monadLift (pure a) = pure a
+monadLift (ma >>= f) = monadLift ma >>= monadLift ∘ f
+```
+-/
+class LawfulMonadLift (m : semiOutParam (Type u → Type v)) (n : Type u → Type w)
+    [Monad m] [Monad n] [inst : MonadLift m n] : Prop where
+  /-- Lifting preserves `pure` -/
+  monadLift_pure {α : Type u} (a : α) : inst.monadLift (pure a) = pure a
+  /-- Lifting preserves `bind` -/
+  monadLift_bind {α β : Type u} (ma : m α) (f : α → m β) :
+    inst.monadLift (ma >>= f) = inst.monadLift ma >>= (fun x => inst.monadLift (f x))
+
+/-- The `MonadLiftT` typeclass only contains the transitive lifting operation.
+  `LawfulMonadLiftT` further asserts that lifting commutes with `pure` and `bind`:
+```
+monadLift (pure a) = pure a
+monadLift (ma >>= f) = monadLift ma >>= monadLift ∘ f
+```
+-/
+class LawfulMonadLiftT (m : Type u → Type v) (n : Type u → Type w) [Monad m] [Monad n]
+    [inst : MonadLiftT m n] : Prop where
+  /-- Lifting preserves `pure` -/
+  monadLift_pure {α : Type u} (a : α) : inst.monadLift (pure a) = pure a
+  /-- Lifting preserves `bind` -/
+  monadLift_bind {α β : Type u} (ma : m α) (f : α → m β) :
+    inst.monadLift (ma >>= f) = monadLift ma >>= (fun x => monadLift (f x))
+
+export LawfulMonadLiftT (monadLift_pure monadLift_bind)
+
+end MonadLift

src/Init/Control/Lawful/MonadLift/Instances.lean

@@ -0,0 +1,137 @@
+/-
+Copyright (c) 2025 Quang Dao. All rights reserved.
+Released under Apache 2.0 license as described in the file LICENSE.
+Authors: Quang Dao, Paul Reichert
+-/
+module
+
+prelude
+import all Init.Control.Option
+import all Init.Control.Except
+import all Init.Control.ExceptCps
+import all Init.Control.StateRef
+import all Init.Control.StateCps
+import Init.Control.Lawful.MonadLift.Lemmas
+import Init.Control.Lawful.Instances
+
+universe u v w x
+
+variable {m : Type u → Type v} {n : Type u → Type w} {o : Type u → Type x}
+
+variable (m n o) in
+instance [Monad m] [Monad n] [Monad o] [MonadLift n o] [MonadLiftT m n]
+    [LawfulMonadLift n o] [LawfulMonadLiftT m n] : LawfulMonadLiftT m o where
+  monadLift_pure := fun a => by
+    simp only [monadLift, LawfulMonadLift.monadLift_pure, liftM_pure]
+  monadLift_bind := fun ma f => by
+    simp only [monadLift, LawfulMonadLift.monadLift_bind, liftM_bind]
+
+variable (m) in
+instance [Monad m] : LawfulMonadLiftT m m where
+  monadLift_pure _ := rfl
+  monadLift_bind _ _ := rfl
+
+namespace StateT
+
+variable [Monad m] [LawfulMonad m]
+
+instance {σ : Type u} : LawfulMonadLift m (StateT σ m) where
+  monadLift_pure _ := by ext; simp [MonadLift.monadLift]
+  monadLift_bind _ _ := by ext; simp [MonadLift.monadLift]
+
+end StateT
+
+namespace ReaderT
+
+variable [Monad m]
+
+instance {ρ : Type u} : LawfulMonadLift m (ReaderT ρ m) where
+  monadLift_pure _ := rfl
+  monadLift_bind _ _ := rfl
+
+end ReaderT
+
+namespace OptionT
+
+variable [Monad m] [LawfulMonad m]
+
+@[simp]
+theorem lift_pure {α : Type u} (a : α) : OptionT.lift (pure a : m α) = pure a := by
+  simp only [OptionT.lift, OptionT.mk, bind_pure_comp, map_pure, pure, OptionT.pure]
+
+@[simp]
+theorem lift_bind {α β : Type u} (ma : m α) (f : α → m β) :
+    OptionT.lift (ma >>= f) = OptionT.lift ma >>= (fun a => OptionT.lift (f a)) := by
+  simp only [instMonad, OptionT.bind, OptionT.mk, OptionT.lift, bind_pure_comp, bind_map_left,
+    map_bind]
+
+instance : LawfulMonadLift m (OptionT m) where
+  monadLift_pure := lift_pure
+  monadLift_bind := lift_bind
+
+end OptionT
+
+namespace ExceptT
+
+variable [Monad m] [LawfulMonad m]
+
+@[simp]
+theorem lift_bind {α β ε : Type u} (ma : m α) (f : α → m β) :
+    ExceptT.lift (ε := ε) (ma >>= f) = ExceptT.lift ma >>= (fun a => ExceptT.lift (f a)) := by
+  simp only [instMonad, ExceptT.bind, mk, ExceptT.lift, bind_map_left, ExceptT.bindCont, map_bind]
+
+instance : LawfulMonadLift m (ExceptT ε m) where
+  monadLift_pure := lift_pure
+  monadLift_bind := lift_bind
+
+instance : LawfulMonadLift (Except ε) (ExceptT ε m) where
+  monadLift_pure _ := by
+    simp only [MonadLift.monadLift, mk, pure, Except.pure, ExceptT.pure]
+  monadLift_bind ma _ := by
+    simp only [instMonad, ExceptT.bind, mk, MonadLift.monadLift, pure_bind, ExceptT.bindCont,
+      Except.instMonad, Except.bind]
+    rcases ma with _ | _ <;> simp
+
+end ExceptT
+
+namespace StateRefT'
+
+instance {ω σ : Type} {m : Type → Type} [Monad m] : LawfulMonadLift m (StateRefT' ω σ m) where
+  monadLift_pure _ := by
+    simp only [MonadLift.monadLift, pure]
+    unfold StateRefT'.lift ReaderT.pure
+    simp only
+  monadLift_bind _ _ := by
+    simp only [MonadLift.monadLift, bind]
+    unfold StateRefT'.lift ReaderT.bind
+    simp only
+
+end StateRefT'
+
+namespace StateCpsT
+
+instance {σ : Type u} [Monad m] [LawfulMonad m] : LawfulMonadLift m (StateCpsT σ m) where
+  monadLift_pure _ := by
+    simp only [MonadLift.monadLift, pure]
+    unfold StateCpsT.lift
+    simp only [pure_bind]
+  monadLift_bind _ _ := by
+    simp only [MonadLift.monadLift, bind]
+    unfold StateCpsT.lift
+    simp only [bind_assoc]
+
+end StateCpsT
+
+namespace ExceptCpsT
+
+instance {ε : Type u} [Monad m] [LawfulMonad m] : LawfulMonadLift m (ExceptCpsT ε m) where
+  monadLift_pure _ := by
+    simp only [MonadLift.monadLift, pure]
+    unfold ExceptCpsT.lift
+    simp only [pure_bind]
+  monadLift_bind _ _ := by
+    simp only [MonadLift.monadLift, bind]
+    unfold ExceptCpsT.lift
+    simp only [bind_assoc]
+
+end ExceptCpsT

src/Init/Control/Lawful/MonadLift/Lemmas.lean

@@ -0,0 +1,63 @@
+/-
+Copyright (c) 2025 Quang Dao. All rights reserved.
+Released under Apache 2.0 license as described in the file LICENSE.
+Authors: Quang Dao
+-/
+module
+
+prelude
+import Init.Control.Lawful.Basic
+import Init.Control.Lawful.MonadLift.Basic
+
+universe u v w
+
+variable {m : Type u → Type v} {n : Type u → Type w} [Monad m] [Monad n] [MonadLiftT m n]
+  [LawfulMonadLiftT m n] {α β : Type u}
+
+theorem monadLift_map [LawfulMonad m] [LawfulMonad n] (f : α → β) (ma : m α) :
+    monadLift (f <$> ma) = f <$> (monadLift ma : n α) := by
+  rw [← bind_pure_comp, ← bind_pure_comp, monadLift_bind]
+  simp only [bind_pure_comp, monadLift_pure]
+
+theorem monadLift_seq [LawfulMonad m] [LawfulMonad n] (mf : m (α → β)) (ma : m α) :
+    monadLift (mf <*> ma) = monadLift mf <*> (monadLift ma : n α) := by
+  simp only [seq_eq_bind, monadLift_map, monadLift_bind]
+
+theorem monadLift_seqLeft [LawfulMonad m] [LawfulMonad n] (x : m α) (y : m β) :
+    monadLift (x <* y) = (monadLift x : n α) <* (monadLift y : n β) := by
+  simp only [seqLeft_eq, monadLift_map, monadLift_seq]
+
+theorem monadLift_seqRight [LawfulMonad m] [LawfulMonad n] (x : m α) (y : m β) :
+    monadLift (x *> y) = (monadLift x : n α) *> (monadLift y : n β) := by
+  simp only [seqRight_eq, monadLift_map, monadLift_seq]
+
+/-! We duplicate the theorems for `monadLift` to `liftM` since `rw` matches on syntax only. -/
+
+@[simp]
+theorem liftM_pure (a : α) : liftM (pure a : m α) = pure (f := n) a :=
+  monadLift_pure _
+
+@[simp]
+theorem liftM_bind (ma : m α) (f : α → m β) :
+    liftM (n := n) (ma >>= f) = liftM ma >>= (fun a => liftM (f a)) :=
+  monadLift_bind _ _
+
+@[simp]
+theorem liftM_map [LawfulMonad m] [LawfulMonad n] (f : α → β) (ma : m α) :
+    liftM (f <$> ma) = f <$> (liftM ma : n α) :=
+  monadLift_map _ _
+
+@[simp]
+theorem liftM_seq [LawfulMonad m] [LawfulMonad n] (mf : m (α → β)) (ma : m α) :
+    liftM (mf <*> ma) = liftM mf <*> (liftM ma : n α) :=
+  monadLift_seq _ _
+
+@[simp]
+theorem liftM_seqLeft [LawfulMonad m] [LawfulMonad n] (x : m α) (y : m β) :
+    liftM (x <* y) = (liftM x : n α) <* (liftM y : n β) :=
+  monadLift_seqLeft _ _
+
+@[simp]
+theorem liftM_seqRight [LawfulMonad m] [LawfulMonad n] (x : m α) (y : m β) :
+    liftM (x *> y) = (liftM x : n α) *> (liftM y : n β) :=
+  monadLift_seqRight _ _

src/Init/Control/State.lean

@@ -29,7 +29,7 @@ of a value and a state.
 Executes an action from a monad with added state in the underlying monad `m`. Given an initial
 state, it returns a value paired with the final state.
 -/
-@[always_inline, inline]
+@[always_inline, inline, expose]
 def StateT.run {σ : Type u} {m : Type u → Type v} {α : Type u} (x : StateT σ m α) (s : σ) : m (α × σ) :=
   x s
 
@@ -37,7 +37,7 @@ def StateT.run {σ : Type u} {m : Type u → Type v} {α : Type u} (x : StateT
 Executes an action from a monad with added state in the underlying monad `m`. Given an initial
 state, it returns a value, discarding the final state.
 -/
-@[always_inline, inline]
+@[always_inline, inline, expose]
 def StateT.run' {σ : Type u} {m : Type u → Type v} [Functor m] {α : Type u} (x : StateT σ m α) (s : σ) : m α :=
   (·.1) <$> x s
 
@@ -66,21 +66,21 @@ variable [Monad m] {α β : Type u}
 /--
 Returns the given value without modifying the state. Typically used via `Pure.pure`.
 -/
-@[always_inline, inline]
+@[always_inline, inline, expose]
 protected def pure (a : α) : StateT σ m α :=
   fun s => pure (a, s)
 
 /--
 Sequences two actions. Typically used via the `>>=` operator.
 -/
-@[always_inline, inline]
+@[always_inline, inline, expose]
 protected def bind (x : StateT σ m α) (f : α → StateT σ m β) : StateT σ m β :=
   fun s => do let (a, s) ← x s; f a s
 
 /--
 Modifies the value returned by a computation. Typically used via the `<$>` operator.
 -/
-@[always_inline, inline]
+@[always_inline, inline, expose]
 protected def map (f : α → β) (x : StateT σ m α) : StateT σ m β :=
   fun s => do let (a, s) ← x s; pure (f a, s)
 
@@ -114,14 +114,14 @@ Retrieves the current value of the monad's mutable state.
 
 This increments the reference count of the state, which may inhibit in-place updates.
 -/
-@[always_inline, inline]
+@[always_inline, inline, expose]
 protected def get : StateT σ m σ :=
   fun s => pure (s, s)
 
 /--
 Replaces the mutable state with a new value.
 -/
-@[always_inline, inline]
+@[always_inline, inline, expose]
 protected def set : σ → StateT σ m PUnit :=
   fun s' _ => pure (⟨⟩, s')
 
@@ -133,7 +133,7 @@ It is equivalent to `do let (a, s) := f (← StateT.get); StateT.set s; pure a`.
 `StateT.modifyGet` may lead to better performance because it doesn't add a new reference to the
 state value, and additional references can inhibit in-place updates of data.
 -/
-@[always_inline, inline]
+@[always_inline, inline, expose]
 protected def modifyGet (f : σ → α × σ) : StateT σ m α :=
   fun s => pure (f s)
 
@@ -143,7 +143,7 @@ Runs an action from the underlying monad in the monad with state. The state is n
 This function is typically implicitly accessed via a `MonadLiftT` instance as part of [automatic
 lifting](lean-manual://section/monad-lifting).
 -/
-@[always_inline, inline]
+@[always_inline, inline, expose]
 protected def lift {α : Type u} (t : m α) : StateT σ m α :=
   fun s => do let a ← t; pure (a, s)
 

src/Init/Control/StateCps.lean

@@ -28,7 +28,7 @@ variable {α σ : Type u} {m : Type u → Type v}
 Runs a stateful computation that's represented using continuation passing style by providing it with
 an initial state and a continuation.
 -/
-@[always_inline, inline]
+@[always_inline, inline, expose]
 def runK (x : StateCpsT σ m α) (s : σ) (k : α → σ → m β) : m β :=
   x _ s k
 
@@ -39,7 +39,7 @@ state, it returns a value paired with the final state.
 While the state is internally represented in continuation passing style, the resulting value is the
 same as for a non-CPS state monad.
 -/
-@[always_inline, inline]
+@[always_inline, inline, expose]
 def run [Monad m] (x : StateCpsT σ m α) (s : σ) : m (α × σ) :=
   runK x s (fun a s => pure (a, s))
 
@@ -47,7 +47,7 @@ def run [Monad m] (x : StateCpsT σ m α) (s : σ) : m (α × σ) :=
 Executes an action from a monad with added state in the underlying monad `m`. Given an initial
 state, it returns a value, discarding the final state.
 -/
-@[always_inline, inline]
+@[always_inline, inline, expose]
 def run' [Monad m] (x : StateCpsT σ m α) (s : σ) : m α :=
   runK x s (fun a _ => pure a)
 
@@ -72,7 +72,7 @@ Runs an action from the underlying monad in the monad with state. The state is n
 This function is typically implicitly accessed via a `MonadLiftT` instance as part of [automatic
 lifting](lean-manual://section/monad-lifting).
 -/
-@[always_inline, inline]
+@[always_inline, inline, expose]
 protected def lift [Monad m] (x : m α) : StateCpsT σ m α :=
   fun _ s k => x >>= (k . s)
 

src/Init/Conv.lean

@@ -9,7 +9,7 @@ module
 
 prelude
 import Init.Tactics
-import Init.Meta
+meta import Init.Meta
 
 namespace Lean.Parser.Tactic.Conv
 

src/Init/Core.lean

@@ -8,7 +8,7 @@ notation, basic datatypes and type classes
 module
 
 prelude
-import Init.Prelude
+meta import Init.Prelude
 import Init.SizeOf
 set_option linter.missingDocs true -- keep it documented
 
@@ -43,14 +43,14 @@ and `flip (·<·)` is the greater-than relation.
 theorem Function.comp_def {α β δ} (f : β → δ) (g : α → β) : f ∘ g = fun x => f (g x) := rfl
 
 @[simp] theorem Function.const_comp {f : α → β} {c : γ} :
-    (Function.const β c ∘ f) = Function.const α c := by
+    (Function.const β c ∘ f) = Function.const α c :=
   rfl
 @[simp] theorem Function.comp_const {f : β → γ} {b : β} :
-    (f ∘ Function.const α b) = Function.const α (f b) := by
+    (f ∘ Function.const α b) = Function.const α (f b) :=
   rfl
-@[simp] theorem Function.true_comp {f : α → β} : ((fun _ => true) ∘ f) = fun _ => true := by
+@[simp] theorem Function.true_comp {f : α → β} : ((fun _ => true) ∘ f) = fun _ => true :=
   rfl
-@[simp] theorem Function.false_comp {f : α → β} : ((fun _ => false) ∘ f) = fun _ => false := by
+@[simp] theorem Function.false_comp {f : α → β} : ((fun _ => false) ∘ f) = fun _ => false :=
   rfl
 
 @[simp] theorem Function.comp_id (f : α → β) : f ∘ id = f := rfl
@@ -95,7 +95,8 @@ structure Thunk (α : Type u) : Type u where
   -/
   mk ::
   /-- Extract the getter function out of a thunk. Use `Thunk.get` instead. -/
-  private fn : Unit → α
+  -- The field is public so as to allow computation through it.
+  fn : Unit → α
 
 attribute [extern "lean_mk_thunk"] Thunk.mk
 
@@ -117,6 +118,10 @@ Computed values are cached, so the value is not recomputed.
 @[extern "lean_thunk_get_own"] protected def Thunk.get (x : @& Thunk α) : α :=
   x.fn ()
 
+-- Ensure `Thunk.fn` is still computable even if it shouldn't be accessed directly.
+@[inline] private def Thunk.fnImpl (x : Thunk α) : Unit → α := fun _ => x.get
+@[csimp] private theorem Thunk.fn_eq_fnImpl : @Thunk.fn = @Thunk.fnImpl := rfl
+
 /--
 Constructs a new thunk that forces `x` and then applies `x` to the result. Upon forcing, the result
 of `f` is cached and the reference to the thunk `x` is dropped.
@@ -897,43 +902,43 @@ section
 variable {α β φ : Sort u} {a a' : α} {b b' : β} {c : φ}
 
 /-- Non-dependent recursor for `HEq` -/
-noncomputable def HEq.ndrec.{u1, u2} {α : Sort u2} {a : α} {motive : {β : Sort u2} → β → Sort u1} (m : motive a) {β : Sort u2} {b : β} (h : HEq a b) : motive b :=
+noncomputable def HEq.ndrec.{u1, u2} {α : Sort u2} {a : α} {motive : {β : Sort u2} → β → Sort u1} (m : motive a) {β : Sort u2} {b : β} (h : a ≍ b) : motive b :=
   h.rec m
 
 /-- `HEq.ndrec` variant -/
-noncomputable def HEq.ndrecOn.{u1, u2} {α : Sort u2} {a : α} {motive : {β : Sort u2} → β → Sort u1} {β : Sort u2} {b : β} (h : HEq a b) (m : motive a) : motive b :=
+noncomputable def HEq.ndrecOn.{u1, u2} {α : Sort u2} {a : α} {motive : {β : Sort u2} → β → Sort u1} {β : Sort u2} {b : β} (h : a ≍ b) (m : motive a) : motive b :=
   h.rec m
 
 /-- `HEq.ndrec` variant -/
-noncomputable def HEq.elim {α : Sort u} {a : α} {p : α → Sort v} {b : α} (h₁ : HEq a b) (h₂ : p a) : p b :=
+noncomputable def HEq.elim {α : Sort u} {a : α} {p : α → Sort v} {b : α} (h₁ : a ≍ b) (h₂ : p a) : p b :=
   eq_of_heq h₁ ▸ h₂
 
 /-- Substitution with heterogeneous equality. -/
-theorem HEq.subst {p : (T : Sort u) → T → Prop} (h₁ : HEq a b) (h₂ : p α a) : p β b :=
+theorem HEq.subst {p : (T : Sort u) → T → Prop} (h₁ : a ≍ b) (h₂ : p α a) : p β b :=
   HEq.ndrecOn h₁ h₂
 
 /-- Heterogeneous equality is symmetric. -/
-@[symm] theorem HEq.symm (h : HEq a b) : HEq b a :=
+@[symm] theorem HEq.symm (h : a ≍ b) : b ≍ a :=
   h.rec (HEq.refl a)
 
 /-- Propositionally equal terms are also heterogeneously equal. -/
-theorem heq_of_eq (h : a = a') : HEq a a' :=
+theorem heq_of_eq (h : a = a') : a ≍ a' :=
   Eq.subst h (HEq.refl a)
 
 /-- Heterogeneous equality is transitive. -/
-theorem HEq.trans (h₁ : HEq a b) (h₂ : HEq b c) : HEq a c :=
+theorem HEq.trans (h₁ : a ≍ b) (h₂ : b ≍ c) : a ≍ c :=
   HEq.subst h₂ h₁
 
 /-- Heterogeneous equality precomposes with propositional equality. -/
-theorem heq_of_heq_of_eq (h₁ : HEq a b) (h₂ : b = b') : HEq a b' :=
+theorem heq_of_heq_of_eq (h₁ : a ≍ b) (h₂ : b = b') : a ≍ b' :=
   HEq.trans h₁ (heq_of_eq h₂)
 
 /-- Heterogeneous equality postcomposes with propositional equality. -/
-theorem heq_of_eq_of_heq (h₁ : a = a') (h₂ : HEq a' b) : HEq a b :=
+theorem heq_of_eq_of_heq (h₁ : a = a') (h₂ : a' ≍ b) : a ≍ b :=
   HEq.trans (heq_of_eq h₁) h₂
 
 /-- If two terms are heterogeneously equal then their types are propositionally equal. -/
-theorem type_eq_of_heq (h : HEq a b) : α = β :=
+theorem type_eq_of_heq (h : a ≍ b) : α = β :=
   h.rec (Eq.refl α)
 
 end
@@ -942,7 +947,7 @@ end
 Rewriting inside `φ` using `Eq.recOn` yields a term that's heterogeneously equal to the original
 term.
 -/
-theorem eqRec_heq {α : Sort u} {φ : α → Sort v} {a a' : α} : (h : a = a') → (p : φ a) → HEq (Eq.recOn (motive := fun x _ => φ x) h p) p
+theorem eqRec_heq {α : Sort u} {φ : α → Sort v} {a a' : α} : (h : a = a') → (p : φ a) → Eq.recOn (motive := fun x _ => φ x) h p ≍ p
   | rfl, p => HEq.refl p
 
 /--
@@ -950,8 +955,8 @@ Heterogeneous equality with an `Eq.rec` application on the left is equivalent to
 equality on the original term.
 -/
 theorem eqRec_heq_iff {α : Sort u} {a : α} {motive : (b : α) → a = b → Sort v}
-    {b : α} {refl : motive a (Eq.refl a)} {h : a = b} {c : motive b h} :
-    HEq (@Eq.rec α a motive refl b h) c ↔ HEq refl c :=
+    {b : α} {refl : motive a (Eq.refl a)} {h : a = b} {c : motive b h}
+    : @Eq.rec α a motive refl b h ≍ c ↔ refl ≍ c :=
   h.rec (fun _ => ⟨id, id⟩) c
 
 /--
@@ -960,7 +965,7 @@ equality on the original term.
 -/
 theorem heq_eqRec_iff {α : Sort u} {a : α} {motive : (b : α) → a = b → Sort v}
     {b : α} {refl : motive a (Eq.refl a)} {h : a = b} {c : motive b h} :
-    HEq c (@Eq.rec α a motive refl b h) ↔ HEq c refl :=
+    c ≍ @Eq.rec α a motive refl b h ↔ c ≍ refl :=
   h.rec (fun _ => ⟨id, id⟩) c
 
 /--
@@ -977,7 +982,7 @@ theorem apply_eqRec {α : Sort u} {a : α} (motive : (b : α) → a = b → Sort
 If casting a term with `Eq.rec` to another type makes it equal to some other term, then the two
 terms are heterogeneously equal.
 -/
-theorem heq_of_eqRec_eq {α β : Sort u} {a : α} {b : β} (h₁ : α = β) (h₂ : Eq.rec (motive := fun α _ => α) a h₁ = b) : HEq a b := by
+theorem heq_of_eqRec_eq {α β : Sort u} {a : α} {b : β} (h₁ : α = β) (h₂ : Eq.rec (motive := fun α _ => α) a h₁ = b) : a ≍ b := by
   subst h₁
   apply heq_of_eq
   exact h₂
@@ -985,7 +990,7 @@ theorem heq_of_eqRec_eq {α β : Sort u} {a : α} {b : β} (h₁ : α = β) (h
 /--
 The result of casting a term with `cast` is heterogeneously equal to the original term.
 -/
-theorem cast_heq {α β : Sort u} : (h : α = β) → (a : α) → HEq (cast h a) a
+theorem cast_heq {α β : Sort u} : (h : α = β) → (a : α) → cast h a ≍ a
   | rfl, a => HEq.refl a
 
 variable {a b c d : Prop}
@@ -1014,8 +1019,8 @@ instance : Trans Iff Iff Iff where
 theorem Eq.comm {a b : α} : a = b ↔ b = a := Iff.intro Eq.symm Eq.symm
 theorem eq_comm {a b : α} : a = b ↔ b = a := Eq.comm
 
-theorem HEq.comm {a : α} {b : β} : HEq a b ↔ HEq b a := Iff.intro HEq.symm HEq.symm
-theorem heq_comm {a : α} {b : β} : HEq a b ↔ HEq b a := HEq.comm
+theorem HEq.comm {a : α} {b : β} : a ≍ b ↔ b ≍ a := Iff.intro HEq.symm HEq.symm
+theorem heq_comm {a : α} {b : β} : a ≍ b ↔ b ≍ a := HEq.comm
 
 @[symm] theorem Iff.symm (h : a ↔ b) : b ↔ a := Iff.intro h.mpr h.mp
 theorem Iff.comm : (a ↔ b) ↔ (b ↔ a) := Iff.intro Iff.symm Iff.symm
@@ -1048,11 +1053,6 @@ theorem Exists.elim {α : Sort u} {p : α → Prop} {b : Prop}
   | isFalse _ => rfl
   | isTrue h  => False.elim h
 
-set_option linter.missingDocs false in
-@[deprecated decide_true (since := "2024-11-05")] abbrev decide_true_eq_true := decide_true
-set_option linter.missingDocs false in
-@[deprecated decide_false (since := "2024-11-05")] abbrev decide_false_eq_false := decide_false
-
 /-- Similar to `decide`, but uses an explicit instance -/
 @[inline] def toBoolUsing {p : Prop} (d : Decidable p) : Bool :=
   decide (h := d)
@@ -1239,7 +1239,7 @@ protected theorem Subsingleton.elim {α : Sort u} [h : Subsingleton α] : (a b :
 If two types are equal and one of them is a subsingleton, then all of their elements are
 [heterogeneously equal](lean-manual://section/HEq).
 -/
-protected theorem Subsingleton.helim {α β : Sort u} [h₁ : Subsingleton α] (h₂ : α = β) (a : α) (b : β) : HEq a b := by
+protected theorem Subsingleton.helim {α β : Sort u} [h₁ : Subsingleton α] (h₂ : α = β) (a : α) (b : β) : a ≍ b := by
   subst h₂
   apply heq_of_eq
   apply Subsingleton.elim
@@ -1690,7 +1690,7 @@ theorem true_iff_false : (True ↔ False) ↔ False := iff_false_intro (·.mp  T
 theorem false_iff_true : (False ↔ True) ↔ False := iff_false_intro (·.mpr True.intro)
 
 theorem iff_not_self : ¬(a ↔ ¬a) | H => let f h := H.1 h h; f (H.2 f)
-theorem heq_self_iff_true (a : α) : HEq a a ↔ True := iff_true_intro HEq.rfl
+theorem heq_self_iff_true (a : α) : a ≍ a ↔ True := iff_true_intro HEq.rfl
 
 /-! ## implies -/
 
@@ -1890,7 +1890,7 @@ a structure.
 protected abbrev hrecOn
     (q : Quot r)
     (f : (a : α) → motive (Quot.mk r a))
-    (c : (a b : α) → (p : r a b) → HEq (f a) (f b))
+    (c : (a b : α) → (p : r a b) → f a ≍ f b)
     : motive q :=
   Quot.recOn q f fun a b p => eq_of_heq (eqRec_heq_iff.mpr (c a b p))
 
@@ -2088,7 +2088,7 @@ a structure.
 protected abbrev hrecOn
     (q : Quotient s)
     (f : (a : α) → motive (Quotient.mk s a))
-    (c : (a b : α) → (p : a ≈ b) → HEq (f a) (f b))
+    (c : (a b : α) → (p : a ≈ b) → f a ≍ f b)
     : motive q :=
   Quot.hrecOn q f c
 end
@@ -2252,7 +2252,7 @@ theorem funext {α : Sort u} {β : α → Sort v} {f g : (x : α) → β x}
     Quot.liftOn f
       (fun (f : ∀ (x : α), β x) => f x)
       (fun _ _ h => h x)
-  show extfunApp (Quot.mk eqv f) = extfunApp (Quot.mk eqv g)
+  change extfunApp (Quot.mk eqv f) = extfunApp (Quot.mk eqv g)
   exact congrArg extfunApp (Quot.sound h)
 
 /--

src/Init/Data/Array/Attach.lean

@@ -22,7 +22,7 @@ an array `xs : Array α`, given a proof that every element of `xs` in fact satis
 
 `Array.pmap`, named for “partial map,” is the equivalent of `Array.map` for such partial functions.
 -/
-
+@[expose]
 def pmap {P : α → Prop} (f : ∀ a, P a → β) (xs : Array α) (H : ∀ a ∈ xs, P a) : Array β :=
   (xs.toList.pmap f (fun a m => H a (mem_def.mpr m))).toArray
 
@@ -39,7 +39,7 @@ of elements in the corresponding subtype `{ x // P x }`.
 
 `O(1)`.
 -/
-@[implemented_by attachWithImpl] def attachWith
+@[implemented_by attachWithImpl, expose] def attachWith
     (xs : Array α) (P : α → Prop) (H : ∀ x ∈ xs, P x) : Array {x // P x} :=
   ⟨xs.toList.attachWith P fun x h => H x (Array.Mem.mk h)⟩
 
@@ -54,7 +54,7 @@ recursion](lean-manual://section/well-founded-recursion) that use higher-order f
 `Array.map`) to prove that an value taken from a list is smaller than the list. This allows the
 well-founded recursion mechanism to prove that the function terminates.
 -/
-@[inline] def attach (xs : Array α) : Array {x // x ∈ xs} := xs.attachWith _ fun _ => id
+@[inline, expose] def attach (xs : Array α) : Array {x // x ∈ xs} := xs.attachWith _ fun _ => id
 
 @[simp, grind =] theorem _root_.List.attachWith_toArray {l : List α} {P : α → Prop} {H : ∀ x ∈ l.toArray, P x} :
     l.toArray.attachWith P H = (l.attachWith P (by simpa using H)).toArray := by
@@ -69,11 +69,11 @@ well-founded recursion mechanism to prove that the function terminates.
   simp [pmap]
 
 @[simp] theorem toList_attachWith {xs : Array α} {P : α → Prop} {H : ∀ x ∈ xs, P x} :
-   (xs.attachWith P H).toList = xs.toList.attachWith P (by simpa [mem_toList] using H) := by
+   (xs.attachWith P H).toList = xs.toList.attachWith P (by simpa [mem_toList_iff] using H) := by
   simp [attachWith]
 
 @[simp] theorem toList_attach {xs : Array α} :
-    xs.attach.toList = xs.toList.attachWith (· ∈ xs) (by simp [mem_toList]) := by
+    xs.attach.toList = xs.toList.attachWith (· ∈ xs) (by simp [mem_toList_iff]) := by
   simp [attach]
 
 @[simp] theorem toList_pmap {xs : Array α} {P : α → Prop} {f : ∀ a, P a → β} {H : ∀ a ∈ xs, P a} :
@@ -574,9 +574,12 @@ state, the right approach is usually the tactic `simp [Array.unattach, -Array.ma
 -/
 def unattach {α : Type _} {p : α → Prop} (xs : Array { x // p x }) : Array α := xs.map (·.val)
 
-@[simp] theorem unattach_nil {p : α → Prop} : (#[] : Array { x // p x }).unattach = #[] := by
+@[simp] theorem unattach_empty {p : α → Prop} : (#[] : Array { x // p x }).unattach = #[] := by
   simp [unattach]
 
+@[deprecated unattach_empty (since := "2025-05-26")]
+abbrev unattach_nil := @unattach_empty
+
 @[simp] theorem unattach_push {p : α → Prop} {a : { x // p x }} {xs : Array { x // p x }} :
     (xs.push a).unattach = xs.unattach.push a.1 := by
   simp only [unattach, Array.map_push]

src/Init/Data/Array/Basic.lean

@@ -91,7 +91,8 @@ theorem ext' {xs ys : Array α} (h : xs.toList = ys.toList) : xs = ys := by
 @[simp, grind =] theorem getElem_toList {xs : Array α} {i : Nat} (h : i < xs.size) : xs.toList[i] = xs[i] := rfl
 
 @[simp, grind =] theorem getElem?_toList {xs : Array α} {i : Nat} : xs.toList[i]? = xs[i]? := by
-  simp [getElem?_def]
+  simp only [getElem?_def, getElem_toList]
+  simp only [Array.size]
 
 /-- `a ∈ as` is a predicate which asserts that `a` is in the array `as`. -/
 -- NB: This is defined as a structure rather than a plain def so that a lemma
@@ -112,6 +113,10 @@ theorem mem_def {a : α} {as : Array α} : a ∈ as ↔ a ∈ as.toList :=
   rw [Array.mem_def, ← getElem_toList]
   apply List.getElem_mem
 
+@[simp, grind =] theorem emptyWithCapacity_eq {α n} : @emptyWithCapacity α n = #[] := rfl
+
+@[simp] theorem mkEmpty_eq {α n} : @mkEmpty α n = #[] := rfl
+
 end Array
 
 namespace List
@@ -163,7 +168,7 @@ Low-level indexing operator which is as fast as a C array read.
 
 This avoids overhead due to unboxing a `Nat` used as an index.
 -/
-@[extern "lean_array_uget", simp]
+@[extern "lean_array_uget", simp, expose]
 def uget (a : @& Array α) (i : USize) (h : i.toNat < a.size) : α :=
   a[i.toNat]
 
@@ -186,7 +191,7 @@ Examples:
 * `#["orange", "yellow"].pop = #["orange"]`
 * `(#[] : Array String).pop = #[]`
 -/
-@[extern "lean_array_pop"]
+@[extern "lean_array_pop", expose]
 def pop (xs : Array α) : Array α where
   toList := xs.toList.dropLast
 
@@ -205,7 +210,7 @@ Examples:
  * `Array.replicate 3 () = #[(), (), ()]`
  * `Array.replicate 0 "anything" = #[]`
 -/
-@[extern "lean_mk_array"]
+@[extern "lean_mk_array", expose]
 def replicate {α : Type u} (n : Nat) (v : α) : Array α where
   toList := List.replicate n v
 
@@ -233,7 +238,7 @@ Examples:
 * `#["red", "green", "blue", "brown"].swap 1 2 = #["red", "blue", "green", "brown"]`
 * `#["red", "green", "blue", "brown"].swap 3 0 = #["brown", "green", "blue", "red"]`
 -/
-@[extern "lean_array_fswap"]
+@[extern "lean_array_fswap", expose]
 def swap (xs : Array α) (i j : @& Nat) (hi : i < xs.size := by get_elem_tactic) (hj : j < xs.size := by get_elem_tactic) : Array α :=
   let v₁ := xs[i]
   let v₂ := xs[j]
@@ -241,7 +246,7 @@ def swap (xs : Array α) (i j : @& Nat) (hi : i < xs.size := by get_elem_tactic)
   xs'.set j v₁ (Nat.lt_of_lt_of_eq hj (size_set _).symm)
 
 @[simp] theorem size_swap {xs : Array α} {i j : Nat} {hi hj} : (xs.swap i j hi hj).size = xs.size := by
-  show ((xs.set i xs[j]).set j xs[i]
+  change ((xs.set i xs[j]).set j xs[i]
     (Nat.lt_of_lt_of_eq hj (size_set _).symm)).size = xs.size
   rw [size_set, size_set]
 
@@ -263,8 +268,6 @@ def swapIfInBounds (xs : Array α) (i j : @& Nat) : Array α :=
   else xs
   else xs
 
-@[deprecated swapIfInBounds (since := "2024-11-24")] abbrev swap! := @swapIfInBounds
-
 /-! ### GetElem instance for `USize`, backed by `uget` -/
 
 instance : GetElem (Array α) USize α fun xs i => i.toNat < xs.size where
@@ -286,6 +289,7 @@ Examples:
  * `#[1, 2].isEmpty = false`
  * `#[()].isEmpty = false`
 -/
+@[expose]
 def isEmpty (xs : Array α) : Bool :=
   xs.size = 0
 
@@ -327,12 +331,16 @@ Examples:
  * `Array.ofFn (n := 3) toString = #["0", "1", "2"]`
  * `Array.ofFn (fun i => #["red", "green", "blue"].get i.val i.isLt) = #["red", "green", "blue"]`
 -/
-def ofFn {n} (f : Fin n → α) : Array α := go 0 (emptyWithCapacity n) where
-  /-- Auxiliary for `ofFn`. `ofFn.go f i acc = acc ++ #[f i, ..., f(n - 1)]` -/
-  @[semireducible] -- This is otherwise irreducible because it uses well-founded recursion.
-  go (i : Nat) (acc : Array α) : Array α :=
-    if h : i < n then go (i+1) (acc.push (f ⟨i, h⟩)) else acc
-  decreasing_by simp_wf; decreasing_trivial_pre_omega
+def ofFn {n} (f : Fin n → α) : Array α := go (emptyWithCapacity n) n (Nat.le_refl n) where
+  /-- Auxiliary for `ofFn`. `ofFn.go f acc i h = acc ++ #[f (n - i), ..., f(n - 1)]` -/
+  go (acc : Array α) : (i : Nat) → i ≤ n → Array α
+  | i + 1, h =>
+     have w : n - i - 1 < n :=
+       Nat.lt_of_lt_of_le (Nat.sub_one_lt (Nat.sub_ne_zero_iff_lt.mpr h)) (Nat.sub_le n i)
+     go (acc.push (f ⟨n - i - 1, w⟩)) i (Nat.le_of_succ_le h)
+  | 0, _ => acc
+
+-- See also `Array.ofFnM` defined in `Init.Data.Array.OfFn`.
 
 /--
 Constructs an array that contains all the numbers from `0` to `n`, exclusive.
@@ -367,7 +375,7 @@ Examples:
  * `Array.singleton 5 = #[5]`
  * `Array.singleton "one" = #["one"]`
 -/
-@[inline] protected def singleton (v : α) : Array α := #[v]
+@[inline, expose] protected def singleton (v : α) : Array α := #[v]
 
 /--
 Returns the last element of an array, or panics if the array is empty.
@@ -396,7 +404,7 @@ that requires a proof the array is non-empty.
 def back? (xs : Array α) : Option α :=
   xs[xs.size - 1]?
 
-@[deprecated "Use `a[i]?` instead." (since := "2025-02-12")]
+@[deprecated "Use `a[i]?` instead." (since := "2025-02-12"), expose]
 def get? (xs : Array α) (i : Nat) : Option α :=
   if h : i < xs.size then some xs[i] else none
 
@@ -410,7 +418,7 @@ Examples:
 * `#["spinach", "broccoli", "carrot"].swapAt 1 "pepper" = ("broccoli", #["spinach", "pepper", "carrot"])`
 * `#["spinach", "broccoli", "carrot"].swapAt 2 "pepper" = ("carrot", #["spinach", "broccoli", "pepper"])`
 -/
-@[inline] def swapAt (xs : Array α) (i : Nat) (v : α) (hi : i < xs.size := by get_elem_tactic) : α × Array α :=
+@[inline, expose] def swapAt (xs : Array α) (i : Nat) (v : α) (hi : i < xs.size := by get_elem_tactic) : α × Array α :=
   let e := xs[i]
   let xs' := xs.set i v
   (e, xs')
@@ -425,7 +433,7 @@ Examples:
 * `#["spinach", "broccoli", "carrot"].swapAt! 1 "pepper" = (#["spinach", "pepper", "carrot"], "broccoli")`
 * `#["spinach", "broccoli", "carrot"].swapAt! 2 "pepper" = (#["spinach", "broccoli", "pepper"], "carrot")`
 -/
-@[inline]
+@[inline, expose]
 def swapAt! (xs : Array α) (i : Nat) (v : α) : α × Array α :=
   if h : i < xs.size then
     swapAt xs i v
@@ -538,7 +546,7 @@ Examples:
 -/
 @[inline]
 def modify (xs : Array α) (i : Nat) (f : α → α) : Array α :=
-  Id.run <| modifyM xs i f
+  Id.run <| modifyM xs i (pure <| f ·)
 
 set_option linter.indexVariables false in -- Changing `idx` causes bootstrapping issues, haven't investigated.
 /--
@@ -571,7 +579,7 @@ def modifyOp (xs : Array α) (idx : Nat) (f : α → α) : Array α :=
   loop 0 b
 
 /-- Reference implementation for `forIn'` -/
-@[implemented_by Array.forIn'Unsafe]
+@[implemented_by Array.forIn'Unsafe, expose]
 protected def forIn' {α : Type u} {β : Type v} {m : Type v → Type w} [Monad m] (as : Array α) (b : β) (f : (a : α) → a ∈ as → β → m (ForInStep β)) : m β :=
   let rec loop (i : Nat) (h : i ≤ as.size) (b : β) : m β := do
     match i, h with
@@ -638,7 +646,7 @@ example [Monad m] (f : α → β → m α) :
 ```
 -/
 -- Reference implementation for `foldlM`
-@[implemented_by foldlMUnsafe]
+@[implemented_by foldlMUnsafe, expose]
 def foldlM {α : Type u} {β : Type v} {m : Type v → Type w} [Monad m] (f : β → α → m β) (init : β) (as : Array α) (start := 0) (stop := as.size) : m β :=
   let fold (stop : Nat) (h : stop ≤ as.size) :=
     let rec loop (i : Nat) (j : Nat) (b : β) : m β := do
@@ -703,7 +711,7 @@ example [Monad m] (f : α → β → m β) :
 ```
 -/
 -- Reference implementation for `foldrM`
-@[implemented_by foldrMUnsafe]
+@[implemented_by foldrMUnsafe, expose]
 def foldrM {α : Type u} {β : Type v} {m : Type v → Type w} [Monad m] (f : α → β → m β) (init : β) (as : Array α) (start := as.size) (stop := 0) : m β :=
   let rec fold (i : Nat) (h : i ≤ as.size) (b : β) : m β := do
     if i == stop then
@@ -758,13 +766,11 @@ def mapM {α : Type u} {β : Type v} {m : Type v → Type w} [Monad m] (f : α
   decreasing_by simp_wf; decreasing_trivial_pre_omega
   map 0 (emptyWithCapacity as.size)
 
-@[deprecated mapM (since := "2024-11-11")] abbrev sequenceMap := @mapM
-
 /--
 Applies the monadic action `f` to every element in the array, along with the element's index and a
 proof that the index is in bounds, from left to right. Returns the array of results.
 -/
-@[inline]
+@[inline, expose]
 def mapFinIdxM {α : Type u} {β : Type v} {m : Type v → Type w} [Monad m]
     (as : Array α) (f : (i : Nat) → α → (h : i < as.size) → m β) : m (Array β) :=
   let rec @[specialize] map (i : Nat) (j : Nat) (inv : i + j = as.size) (bs : Array β) : m (Array β) := do
@@ -782,7 +788,7 @@ def mapFinIdxM {α : Type u} {β : Type v} {m : Type v → Type w} [Monad m]
 Applies the monadic action `f` to every element in the array, along with the element's index, from
 left to right. Returns the array of results.
 -/
-@[inline]
+@[inline, expose]
 def mapIdxM {α : Type u} {β : Type v} {m : Type v → Type w} [Monad m] (f : Nat → α → m β) (as : Array α) : m (Array β) :=
   as.mapFinIdxM fun i a _ => f i a
 
@@ -828,7 +834,7 @@ Almost! 5
 some 10
 ```
 -/
-@[inline]
+@[inline, expose]
 def findSomeM? {α : Type u} {β : Type v} {m : Type v → Type w} [Monad m] (f : α → m (Option β)) (as : Array α) : m (Option β) := do
   for a in as do
     match (← f a) with
@@ -909,7 +915,7 @@ The optional parameters `start` and `stop` control the region of the array to be
 elements with indices from `start` (inclusive) to `stop` (exclusive) are checked. By default, the
 entire array is checked.
 -/
-@[implemented_by anyMUnsafe]
+@[implemented_by anyMUnsafe, expose]
 def anyM {α : Type u} {m : Type → Type w} [Monad m] (p : α → m Bool) (as : Array α) (start := 0) (stop := as.size) : m Bool :=
   let any (stop : Nat) (h : stop ≤ as.size) :=
     let rec @[semireducible] -- This is otherwise irreducible because it uses well-founded recursion.
@@ -1051,9 +1057,9 @@ Examples:
  * `#[1, 2, 3].foldl (· ++ toString ·) "" = "123"`
  * `#[1, 2, 3].foldl (s!"({·} {·})") "" = "((( 1) 2) 3)"`
 -/
-@[inline]
+@[inline, expose]
 def foldl {α : Type u} {β : Type v} (f : β → α → β) (init : β) (as : Array α) (start := 0) (stop := as.size) : β :=
-  Id.run <| as.foldlM f init start stop
+  Id.run <| as.foldlM (pure <| f · ·) init start stop
 
 /--
 Folds a function over an array from the right, accumulating a value starting with `init`. The
@@ -1068,9 +1074,9 @@ Examples:
  * `#[1, 2, 3].foldr (toString · ++ ·) "" = "123"`
  * `#[1, 2, 3].foldr (s!"({·} {·})") "!" = "(1 (2 (3 !)))"`
 -/
-@[inline]
+@[inline, expose]
 def foldr {α : Type u} {β : Type v} (f : α → β → β) (init : β) (as : Array α) (start := as.size) (stop := 0) : β :=
-  Id.run <| as.foldrM f init start stop
+  Id.run <| as.foldrM (pure <| f · ·) init start stop
 
 /--
 Computes the sum of the elements of an array.
@@ -1079,7 +1085,7 @@ Examples:
  * `#[a, b, c].sum = a + (b + (c + 0))`
  * `#[1, 2, 5].sum = 8`
 -/
-@[inline]
+@[inline, expose]
 def sum {α} [Add α] [Zero α] : Array α → α :=
   foldr (· + ·) 0
 
@@ -1091,7 +1097,7 @@ Examples:
  * `#[1, 2, 3, 4, 5].countP (· < 5) = 4`
  * `#[1, 2, 3, 4, 5].countP (· > 5) = 0`
 -/
-@[inline]
+@[inline, expose]
 def countP {α : Type u} (p : α → Bool) (as : Array α) : Nat :=
   as.foldr (init := 0) fun a acc => bif p a then acc + 1 else acc
 
@@ -1103,7 +1109,7 @@ Examples:
  * `#[1, 1, 2, 3, 5].count 5 = 1`
  * `#[1, 1, 2, 3, 5].count 4 = 0`
 -/
-@[inline]
+@[inline, expose]
 def count {α : Type u} [BEq α] (a : α) (as : Array α) : Nat :=
   countP (· == a) as
 
@@ -1116,9 +1122,9 @@ Examples:
 * `#["one", "two", "three"].map (·.length) = #[3, 3, 5]`
 * `#["one", "two", "three"].map (·.reverse) = #["eno", "owt", "eerht"]`
 -/
-@[inline]
+@[inline, expose]
 def map {α : Type u} {β : Type v} (f : α → β) (as : Array α) : Array β :=
-  Id.run <| as.mapM f
+  Id.run <| as.mapM (pure <| f ·)
 
 instance : Functor Array where
   map := map
@@ -1131,9 +1137,9 @@ that the index is valid.
 `Array.mapIdx` is a variant that does not provide the function with evidence that the index is
 valid.
 -/
-@[inline]
+@[inline, expose]
 def mapFinIdx {α : Type u} {β : Type v} (as : Array α) (f : (i : Nat) → α → (h : i < as.size) → β) : Array β :=
-  Id.run <| as.mapFinIdxM f
+  Id.run <| as.mapFinIdxM (pure <| f · · ·)
 
 /--
 Applies a function to each element of the array along with the index at which that element is found,
@@ -1142,9 +1148,9 @@ returning the array of results.
 `Array.mapFinIdx` is a variant that additionally provides the function with a proof that the index
 is valid.
 -/
-@[inline]
+@[inline, expose]
 def mapIdx {α : Type u} {β : Type v} (f : Nat → α → β) (as : Array α) : Array β :=
-  Id.run <| as.mapIdxM f
+  Id.run <| as.mapIdxM (pure <| f · ·)
 
 /--
 Pairs each element of an array with its index, optionally starting from an index other than `0`.
@@ -1153,6 +1159,7 @@ Examples:
 * `#[a, b, c].zipIdx = #[(a, 0), (b, 1), (c, 2)]`
 * `#[a, b, c].zipIdx 5 = #[(a, 5), (b, 6), (c, 7)]`
 -/
+@[expose]
 def zipIdx (xs : Array α) (start := 0) : Array (α × Nat) :=
   xs.mapIdx fun i a => (a, start + i)
 
@@ -1166,7 +1173,7 @@ Examples:
 * `#[7, 6, 5, 8, 1, 2, 6].find? (· < 5) = some 1`
 * `#[7, 6, 5, 8, 1, 2, 6].find? (· < 1) = none`
 -/
-@[inline]
+@[inline, expose]
 def find? {α : Type u} (p : α → Bool) (as : Array α) : Option α :=
   Id.run do
     for a in as do
@@ -1190,9 +1197,9 @@ Example:
 some 10
 ```
 -/
-@[inline]
+@[inline, expose]
 def findSome? {α : Type u} {β : Type v} (f : α → Option β) (as : Array α) : Option β :=
-  Id.run <| as.findSomeM? f
+  Id.run <| as.findSomeM? (pure <| f ·)
 
 /--
 Returns the first non-`none` result of applying the function `f` to each element of the
@@ -1226,7 +1233,7 @@ Examples:
 -/
 @[inline]
 def findSomeRev? {α : Type u} {β : Type v} (f : α → Option β) (as : Array α) : Option β :=
-  Id.run <| as.findSomeRevM? f
+  Id.run <| as.findSomeRevM? (pure <| f ·)
 
 /--
 Returns the last element of the array for which the predicate `p` returns `true`, or `none` if no
@@ -1238,7 +1245,7 @@ Examples:
 -/
 @[inline]
 def findRev? {α : Type} (p : α → Bool) (as : Array α) : Option α :=
-  Id.run <| as.findRevM? p
+  Id.run <| as.findRevM? (pure <| p ·)
 
 /--
 Returns the index of the first element for which `p` returns `true`, or `none` if there is no such
@@ -1248,7 +1255,7 @@ Examples:
 * `#[7, 6, 5, 8, 1, 2, 6].findIdx (· < 5) = some 4`
 * `#[7, 6, 5, 8, 1, 2, 6].findIdx (· < 1) = none`
 -/
-@[inline]
+@[inline, expose]
 def findIdx? {α : Type u} (p : α → Bool) (as : Array α) : Option Nat :=
   let rec @[semireducible] -- This is otherwise irreducible because it uses well-founded recursion.
   loop (j : Nat) :=
@@ -1302,7 +1309,7 @@ Examples:
 * `#[7, 6, 5, 8, 1, 2, 6].findIdx (· < 5) = 4`
 * `#[7, 6, 5, 8, 1, 2, 6].findIdx (· < 1) = 7`
 -/
-@[inline]
+@[inline, expose]
 def findIdx (p : α → Bool) (as : Array α) : Nat := (as.findIdx? p).getD as.size
 
 @[semireducible] -- This is otherwise irreducible because it uses well-founded recursion.
@@ -1356,10 +1363,6 @@ Examples:
 def idxOf? [BEq α] (xs : Array α) (v : α) : Option Nat :=
   (xs.finIdxOf? v).map (·.val)
 
-@[deprecated idxOf? (since := "2024-11-20")]
-def getIdx? [BEq α] (xs : Array α) (v : α) : Option Nat :=
-  xs.findIdx? fun a => a == v
-
 /--
 Returns `true` if `p` returns `true` for any element of `as`.
 
@@ -1375,9 +1378,9 @@ Examples:
 * `#[2, 4, 5, 6].any (· % 2 = 0) = true`
 * `#[2, 4, 5, 6].any (· % 2 = 1) = true`
 -/
-@[inline]
+@[inline, expose]
 def any (as : Array α) (p : α → Bool) (start := 0) (stop := as.size) : Bool :=
-  Id.run <| as.anyM p start stop
+  Id.run <| as.anyM (pure <| p ·) start stop
 
 /--
 Returns `true` if `p` returns `true` for every element of `as`.
@@ -1395,7 +1398,7 @@ Examples:
 -/
 @[inline]
 def all (as : Array α) (p : α → Bool) (start := 0) (stop := as.size) : Bool :=
-  Id.run <| as.allM p start stop
+  Id.run <| as.allM (pure <| p ·) start stop
 
 /--
 Checks whether `a` is an element of `as`, using `==` to compare elements.
@@ -1406,6 +1409,7 @@ Examples:
 * `#[1, 4, 2, 3, 3, 7].contains 3 = true`
 * `Array.contains #[1, 4, 2, 3, 3, 7] 5 = false`
 -/
+@[expose]
 def contains [BEq α] (as : Array α) (a : α) : Bool :=
   as.any (a == ·)
 
@@ -1454,6 +1458,7 @@ Examples:
   * `#[] ++ #[4, 5] = #[4, 5]`.
   * `#[1, 2, 3] ++ #[] = #[1, 2, 3]`.
 -/
+@[expose]
 protected def append (as : Array α) (bs : Array α) : Array α :=
   bs.foldl (init := as) fun xs v => xs.push v
 
@@ -1491,7 +1496,7 @@ Examples:
 * `#[2, 3, 2].flatMap Array.range = #[0, 1, 0, 1, 2, 0, 1]`
 * `#[['a', 'b'], ['c', 'd', 'e']].flatMap List.toArray = #['a', 'b', 'c', 'd', 'e']`
 -/
-@[inline]
+@[inline, expose]
 def flatMap (f : α → Array β) (as : Array α) : Array β :=
   as.foldl (init := empty) fun bs a => bs ++ f a
 
@@ -1504,7 +1509,7 @@ Examples:
  * `#[#[0, 1], #[], #[2], #[1, 0, 1]].flatten = #[0, 1, 2, 1, 0, 1]`
  * `(#[] : Array Nat).flatten = #[]`
 -/
-@[inline] def flatten (xss : Array (Array α)) : Array α :=
+@[inline, expose] def flatten (xss : Array (Array α)) : Array α :=
   xss.foldl (init := empty) fun acc xs => acc ++ xs
 
 /--
@@ -1517,6 +1522,7 @@ Examples:
 * `#[0, 1].reverse = #[1, 0]`
 * `#[0, 1, 2].reverse = #[2, 1, 0]`
 -/
+@[expose]
 def reverse (as : Array α) : Array α :=
   if h : as.size ≤ 1 then
     as
@@ -1549,7 +1555,7 @@ Examples:
 * `#[1, 2, 5, 2, 7, 7].filter (fun _ => true) (start := 3) = #[2, 7, 7]`
 * `#[1, 2, 5, 2, 7, 7].filter (fun _ => true) (stop := 3) = #[1, 2, 5]`
 -/
-@[inline]
+@[inline, expose]
 def filter (p : α → Bool) (as : Array α) (start := 0) (stop := as.size) : Array α :=
   as.foldl (init := #[]) (start := start) (stop := stop) fun acc a =>
     if p a then acc.push a else acc
@@ -1642,7 +1648,7 @@ Examining 7
 #[10, 14, 14]
 ```
 -/
-@[specialize]
+@[specialize, expose]
 def filterMapM [Monad m] (f : α → m (Option β)) (as : Array α) (start := 0) (stop := as.size) : m (Array β) :=
   as.foldlM (init := #[]) (start := start) (stop := stop) fun bs a => do
     match (← f a) with
@@ -1662,9 +1668,9 @@ Example:
 #[10, 14, 14]
 ```
 -/
-@[inline]
+@[inline, expose]
 def filterMap (f : α → Option β) (as : Array α) (start := 0) (stop := as.size) : Array β :=
-  Id.run <| as.filterMapM f (start := start) (stop := stop)
+  Id.run <| as.filterMapM (pure <| f ·) (start := start) (stop := stop)
 
 /--
 Returns the largest element of the array, as determined by the comparison `lt`, or `none` if
@@ -1875,8 +1881,6 @@ Examples:
   let as := as.push a
   loop as ⟨j, size_push .. ▸ j.lt_succ_self⟩
 
-@[deprecated insertIdx (since := "2024-11-20")] abbrev insertAt := @insertIdx
-
 /--
 Inserts an element into an array at the specified index. Panics if the index is greater than the
 size of the array.
@@ -1897,8 +1901,6 @@ def insertIdx! (as : Array α) (i : Nat) (a : α) : Array α :=
     insertIdx as i a
   else panic! "invalid index"
 
-@[deprecated insertIdx! (since := "2024-11-20")] abbrev insertAt! := @insertIdx!
-
 /--
 Inserts an element into an array at the specified index. The array is returned unmodified if the
 index is greater than the size of the array.
@@ -2021,11 +2023,6 @@ Examples:
 def unzip (as : Array (α × β)) : Array α × Array β :=
   as.foldl (init := (#[], #[])) fun (as, bs) (a, b) => (as.push a, bs.push b)
 
-@[deprecated partition (since := "2024-11-06")]
-def split (as : Array α) (p : α → Bool) : Array α × Array α :=
-  as.foldl (init := (#[], #[])) fun (as, bs) a =>
-    if p a then (as.push a, bs) else (as, bs.push a)
-
 /--
 Replaces the first occurrence of `a` with `b` in an array. The modification is performed in-place
 when the reference to the array is unique. Returns the array unmodified when `a` is not present.

src/Init/Data/Array/BasicAux.lean

@@ -88,4 +88,4 @@ pointer equality, and does not allocate a new array if the result of each functi
 pointer-equal to its argument.
 -/
 @[inline] def Array.mapMono (as : Array α) (f : α → α) : Array α :=
-  Id.run <| as.mapMonoM f
+  Id.run <| as.mapMonoM (pure <| f ·)

src/Init/Data/Array/BinSearch.lean

@@ -129,6 +129,6 @@ Examples:
 * `#[].binInsert (· < ·) 1 = #[1]`
 -/
 @[inline] def binInsert {α : Type u} (lt : α → α → Bool) (as : Array α) (k : α) : Array α :=
-  Id.run <| binInsertM lt (fun _ => k) (fun _ => k) as k
+  Id.run <| binInsertM lt (fun _ => pure k) (fun _ => pure k) as k
 
 end Array

src/Init/Data/Array/Bootstrap.lean

@@ -40,7 +40,7 @@ Use the indexing notation `a[i]!` instead.
 
 Access an element from an array, or panic if the index is out of bounds.
 -/
-@[deprecated "Use indexing notation `as[i]!` instead" (since := "2025-02-17")]
+@[deprecated "Use indexing notation `as[i]!` instead" (since := "2025-02-17"), expose]
 def get! {α : Type u} [Inhabited α] (a : @& Array α) (i : @& Nat) : α :=
   Array.getD a i default
 
@@ -78,7 +78,8 @@ theorem foldrM_eq_reverse_foldlM_toList [Monad m] {f : α → β → m β} {init
   have : xs = #[] ∨ 0 < xs.size :=
     match xs with | ⟨[]⟩ => .inl rfl | ⟨a::l⟩ => .inr (Nat.zero_lt_succ _)
   match xs, this with | _, .inl rfl => simp [foldrM] | xs, .inr h => ?_
-  simp [foldrM, h, ← foldrM_eq_reverse_foldlM_toList.aux, List.take_length]
+  simp only [foldrM, h, ← foldrM_eq_reverse_foldlM_toList.aux]
+  simp [Array.size]
 
 @[simp, grind =] theorem foldrM_toList [Monad m]
     {f : α → β → m β} {init : β} {xs : Array α} :
@@ -89,9 +90,13 @@ theorem foldrM_eq_reverse_foldlM_toList [Monad m] {f : α → β → m β} {init
     xs.toList.foldr f init = xs.foldr f init :=
   List.foldr_eq_foldrM .. ▸ foldrM_toList ..
 
-@[simp, grind =] theorem push_toList {xs : Array α} {a : α} : (xs.push a).toList = xs.toList ++ [a] := by
+@[simp, grind =] theorem toList_push {xs : Array α} {x : α} : (xs.push x).toList = xs.toList ++ [x] := by
+  rcases xs with ⟨xs⟩
   simp [push, List.concat_eq_append]
 
+@[deprecated toList_push (since := "2025-05-26")]
+abbrev push_toList := @toList_push
+
 @[simp, grind =] theorem toListAppend_eq {xs : Array α} {l : List α} : xs.toListAppend l = xs.toList ++ l := by
   simp [toListAppend, ← foldr_toList]
 
@@ -138,26 +143,4 @@ abbrev nil_append := @empty_append
 @[deprecated toList_appendList (since := "2024-12-11")]
 abbrev appendList_toList := @toList_appendList
 
-@[deprecated "Use the reverse direction of `foldrM_toList`." (since := "2024-11-13")]
-theorem foldrM_eq_foldrM_toList [Monad m]
-    {f : α → β → m β} {init : β} {xs : Array α} :
-    xs.foldrM f init = xs.toList.foldrM f init := by
-  simp
-
-@[deprecated "Use the reverse direction of `foldlM_toList`." (since := "2024-11-13")]
-theorem foldlM_eq_foldlM_toList [Monad m]
-    {f : β → α → m β} {init : β} {xs : Array α} :
-    xs.foldlM f init = xs.toList.foldlM f init:= by
-  simp
-
-@[deprecated "Use the reverse direction of `foldr_toList`." (since := "2024-11-13")]
-theorem foldr_eq_foldr_toList {f : α → β → β} {init : β} {xs : Array α} :
-    xs.foldr f init = xs.toList.foldr f init := by
-  simp
-
-@[deprecated "Use the reverse direction of `foldl_toList`." (since := "2024-11-13")]
-theorem foldl_eq_foldl_toList {f : β → α → β} {init : β} {xs : Array α} :
-    xs.foldl f init = xs.toList.foldl f init:= by
-  simp
-
 end Array

src/Init/Data/Array/Count.lean

@@ -52,17 +52,20 @@ theorem countP_push {a : α} {xs : Array α} : countP p (xs.push a) = countP p x
   rcases xs with ⟨xs⟩
   simp_all
 
-@[simp] theorem countP_singleton {a : α} : countP p #[a] = if p a then 1 else 0 := by
-  simp [countP_push]
+@[grind =]
+theorem countP_singleton {a : α} : countP p #[a] = if p a then 1 else 0 := by
+  simp
 
 theorem size_eq_countP_add_countP {xs : Array α} : xs.size = countP p xs + countP (fun a => ¬p a) xs := by
   rcases xs with ⟨xs⟩
   simp [List.length_eq_countP_add_countP (p := p)]
 
+@[grind _=_]
 theorem countP_eq_size_filter {xs : Array α} : countP p xs = (filter p xs).size := by
   rcases xs with ⟨xs⟩
   simp [List.countP_eq_length_filter]
 
+@[grind =]
 theorem countP_eq_size_filter' : countP p = size ∘ filter p := by
   funext xs
   apply countP_eq_size_filter
@@ -71,7 +74,7 @@ theorem countP_le_size : countP p xs ≤ xs.size := by
   simp only [countP_eq_size_filter]
   apply size_filter_le
 
-@[simp] theorem countP_append {xs ys : Array α} : countP p (xs ++ ys) = countP p xs + countP p ys := by
+@[simp, grind =] theorem countP_append {xs ys : Array α} : countP p (xs ++ ys) = countP p xs + countP p ys := by
   rcases xs with ⟨xs⟩
   rcases ys with ⟨ys⟩
   simp
@@ -102,9 +105,11 @@ theorem boole_getElem_le_countP {xs : Array α} {i : Nat} (h : i < xs.size) :
   rcases xs with ⟨xs⟩
   simp [List.boole_getElem_le_countP]
 
+@[grind =]
 theorem countP_set {xs : Array α} {i : Nat} {a : α} (h : i < xs.size) :
     (xs.set i a).countP p = xs.countP p - (if p xs[i] then 1 else 0) + (if p a then 1 else 0) := by
   rcases xs with ⟨xs⟩
+  simp at h
   simp [List.countP_set, h]
 
 theorem countP_filter {xs : Array α} :
@@ -145,7 +150,7 @@ theorem countP_flatMap {p : β → Bool} {xs : Array α} {f : α → Array β} :
   rcases xs with ⟨xs⟩
   simp [List.countP_flatMap, Function.comp_def]
 
-@[simp] theorem countP_reverse {xs : Array α} : countP p xs.reverse = countP p xs := by
+@[simp, grind =] theorem countP_reverse {xs : Array α} : countP p xs.reverse = countP p xs := by
   rcases xs with ⟨xs⟩
   simp [List.countP_reverse]
 
@@ -172,7 +177,7 @@ variable [BEq α]
   cases xs
   simp
 
-@[simp] theorem count_empty {a : α} : count a #[] = 0 := rfl
+@[simp, grind =] theorem count_empty {a : α} : count a #[] = 0 := rfl
 
 theorem count_push {a b : α} {xs : Array α} :
     count a (xs.push b) = count a xs + if b == a then 1 else 0 := by
@@ -185,21 +190,28 @@ theorem count_eq_countP' {a : α} : count a = countP (· == a) := by
 
 theorem count_le_size {a : α} {xs : Array α} : count a xs ≤ xs.size := countP_le_size
 
+grind_pattern count_le_size => count a xs
+
+@[grind =]
+theorem count_eq_size_filter {a : α} {xs : Array α} : count a xs = (filter (· == a) xs).size := by
+  simp [count, countP_eq_size_filter]
+
 theorem count_le_count_push {a b : α} {xs : Array α} : count a xs ≤ count a (xs.push b) := by
   simp [count_push]
 
+@[grind =]
 theorem count_singleton {a b : α} : count a #[b] = if b == a then 1 else 0 := by
   simp [count_eq_countP]
 
-@[simp] theorem count_append {a : α} {xs ys : Array α} : count a (xs ++ ys) = count a xs + count a ys :=
+@[simp, grind =] theorem count_append {a : α} {xs ys : Array α} : count a (xs ++ ys) = count a xs + count a ys :=
   countP_append
 
-@[simp] theorem count_flatten {a : α} {xss : Array (Array α)} :
+@[simp, grind =] theorem count_flatten {a : α} {xss : Array (Array α)} :
     count a xss.flatten = (xss.map (count a)).sum := by
   cases xss using array₂_induction
   simp [List.count_flatten, Function.comp_def]
 
-@[simp] theorem count_reverse {a : α} {xs : Array α} : count a xs.reverse = count a xs := by
+@[simp, grind =] theorem count_reverse {a : α} {xs : Array α} : count a xs.reverse = count a xs := by
   rcases xs with ⟨xs⟩
   simp
 
@@ -208,6 +220,7 @@ theorem boole_getElem_le_count {xs : Array α} {i : Nat} {a : α} (h : i < xs.si
   rw [count_eq_countP]
   apply boole_getElem_le_countP (p := (· == a))
 
+@[grind =]
 theorem count_set {xs : Array α} {i : Nat} {a b : α} (h : i < xs.size) :
     (xs.set i a).count b = xs.count b - (if xs[i] == b then 1 else 0) + (if a == b then 1 else 0) := by
   simp [count_eq_countP, countP_set, h]

src/Init/Data/Array/DecidableEq.lean

@@ -69,7 +69,7 @@ theorem isEqv_eq_decide (xs ys : Array α) (r) :
     simpa [isEqv_iff_rel] using h'
 
 @[simp, grind =] theorem isEqv_toList [BEq α] (xs ys : Array α) : (xs.toList.isEqv ys.toList r) = (xs.isEqv ys r) := by
-  simp [isEqv_eq_decide, List.isEqv_eq_decide]
+  simp [isEqv_eq_decide, List.isEqv_eq_decide, Array.size]
 
 theorem eq_of_isEqv [DecidableEq α] (xs ys : Array α) (h : Array.isEqv xs ys (fun x y => x = y)) : xs = ys := by
   have ⟨h, h'⟩ := rel_of_isEqv h
@@ -100,7 +100,7 @@ theorem beq_eq_decide [BEq α] (xs ys : Array α) :
   simp [BEq.beq, isEqv_eq_decide]
 
 @[simp, grind =] theorem beq_toList [BEq α] (xs ys : Array α) : (xs.toList == ys.toList) = (xs == ys) := by
-  simp [beq_eq_decide, List.beq_eq_decide]
+  simp [beq_eq_decide, List.beq_eq_decide, Array.size]
 
 end Array
 

src/Init/Data/Array/Erase.lean

@@ -24,7 +24,8 @@ open Nat
 
 /-! ### eraseP -/
 
-@[simp] theorem eraseP_empty : #[].eraseP p = #[] := by simp
+@[grind =]
+theorem eraseP_empty : #[].eraseP p = #[] := by simp
 
 theorem eraseP_of_forall_mem_not {xs : Array α} (h : ∀ a, a ∈ xs → ¬p a) : xs.eraseP p = xs := by
   rcases xs with ⟨xs⟩
@@ -64,6 +65,7 @@ theorem exists_or_eq_self_of_eraseP (p) (xs : Array α) :
   let ⟨_, ys, zs, _, _, e₁, e₂⟩ := exists_of_eraseP al pa
   rw [e₂]; simp [size_append, e₁]
 
+@[grind =]
 theorem size_eraseP {xs : Array α} : (xs.eraseP p).size = if xs.any p then xs.size - 1 else xs.size := by
   split <;> rename_i h
   · simp only [any_eq_true] at h
@@ -81,11 +83,12 @@ theorem le_size_eraseP {xs : Array α} : xs.size - 1 ≤ (xs.eraseP p).size := b
   rcases xs with ⟨xs⟩
   simpa using List.le_length_eraseP
 
+@[grind →]
 theorem mem_of_mem_eraseP {xs : Array α} : a ∈ xs.eraseP p → a ∈ xs := by
   rcases xs with ⟨xs⟩
   simpa using List.mem_of_mem_eraseP
 
-@[simp] theorem mem_eraseP_of_neg {xs : Array α} (pa : ¬p a) : a ∈ xs.eraseP p ↔ a ∈ xs := by
+@[simp, grind] theorem mem_eraseP_of_neg {xs : Array α} (pa : ¬p a) : a ∈ xs.eraseP p ↔ a ∈ xs := by
   rcases xs with ⟨xs⟩
   simpa using List.mem_eraseP_of_neg pa
 
@@ -93,15 +96,18 @@ theorem mem_of_mem_eraseP {xs : Array α} : a ∈ xs.eraseP p → a ∈ xs := by
   rcases xs with ⟨xs⟩
   simp
 
+@[grind _=_]
 theorem eraseP_map {f : β → α} {xs : Array β} : (xs.map f).eraseP p = (xs.eraseP (p ∘ f)).map f := by
   rcases xs with ⟨xs⟩
   simpa using List.eraseP_map
 
+@[grind =]
 theorem eraseP_filterMap {f : α → Option β} {xs : Array α} :
     (filterMap f xs).eraseP p = filterMap f (xs.eraseP (fun x => match f x with | some y => p y | none => false)) := by
   rcases xs with ⟨xs⟩
   simpa using List.eraseP_filterMap
 
+@[grind =]
 theorem eraseP_filter {f : α → Bool} {xs : Array α} :
     (filter f xs).eraseP p = filter f (xs.eraseP (fun x => p x && f x)) := by
   rcases xs with ⟨xs⟩
@@ -119,6 +125,7 @@ theorem eraseP_append_right {xs : Array α} ys (h : ∀ b ∈ xs, ¬p b) :
   rcases ys with ⟨ys⟩
   simpa using List.eraseP_append_right ys (by simpa using h)
 
+@[grind =]
 theorem eraseP_append {xs : Array α} {ys : Array α} :
     (xs ++ ys).eraseP p = if xs.any p then xs.eraseP p ++ ys else xs ++ ys.eraseP p := by
   rcases xs with ⟨xs⟩
@@ -126,6 +133,7 @@ theorem eraseP_append {xs : Array α} {ys : Array α} :
   simp only [List.append_toArray, List.eraseP_toArray, List.eraseP_append, List.any_toArray]
   split <;> simp
 
+@[grind =]
 theorem eraseP_replicate {n : Nat} {a : α} {p : α → Bool} :
     (replicate n a).eraseP p = if p a then replicate (n - 1) a else replicate n a := by
   simp only [← List.toArray_replicate, List.eraseP_toArray, List.eraseP_replicate]
@@ -165,6 +173,7 @@ theorem eraseP_eq_iff {p} {xs : Array α} :
     · exact Or.inl h
     · exact Or.inr ⟨a, l₁, by simpa using h₁, h₂, ⟨l, by simp⟩⟩
 
+@[grind =]
 theorem eraseP_comm {xs : Array α} (h : ∀ a ∈ xs, ¬ p a ∨ ¬ q a) :
     (xs.eraseP p).eraseP q = (xs.eraseP q).eraseP p := by
   rcases xs with ⟨xs⟩
@@ -208,6 +217,7 @@ theorem exists_erase_eq [LawfulBEq α] {a : α} {xs : Array α} (h : a ∈ xs) :
     (xs.erase a).size = xs.size - 1 := by
   rw [erase_eq_eraseP]; exact size_eraseP_of_mem h (beq_self_eq_true a)
 
+@[grind =]
 theorem size_erase [LawfulBEq α] {a : α} {xs : Array α} :
     (xs.erase a).size = if a ∈ xs then xs.size - 1 else xs.size := by
   rw [erase_eq_eraseP, size_eraseP]
@@ -222,11 +232,12 @@ theorem le_size_erase [LawfulBEq α] {a : α} {xs : Array α} : xs.size - 1 ≤
   rcases xs with ⟨xs⟩
   simpa using List.le_length_erase
 
+@[grind →]
 theorem mem_of_mem_erase {a b : α} {xs : Array α} (h : a ∈ xs.erase b) : a ∈ xs := by
   rcases xs with ⟨xs⟩
   simpa using List.mem_of_mem_erase (by simpa using h)
 
-@[simp] theorem mem_erase_of_ne [LawfulBEq α] {a b : α} {xs : Array α} (ab : a ≠ b) :
+@[simp, grind] theorem mem_erase_of_ne [LawfulBEq α] {a b : α} {xs : Array α} (ab : a ≠ b) :
     a ∈ xs.erase b ↔ a ∈ xs :=
   erase_eq_eraseP b xs ▸ mem_eraseP_of_neg (mt eq_of_beq ab.symm)
 
@@ -234,6 +245,7 @@ theorem mem_of_mem_erase {a b : α} {xs : Array α} (h : a ∈ xs.erase b) : a
   rw [erase_eq_eraseP', eraseP_eq_self_iff]
   simp [forall_mem_ne']
 
+@[grind _=_]
 theorem erase_filter [LawfulBEq α] {f : α → Bool} {xs : Array α} :
     (filter f xs).erase a = filter f (xs.erase a) := by
   rcases xs with ⟨xs⟩
@@ -251,6 +263,7 @@ theorem erase_append_right [LawfulBEq α] {a : α} {xs : Array α} (ys : Array
   rcases ys with ⟨ys⟩
   simpa using List.erase_append_right ys (by simpa using h)
 
+@[grind =]
 theorem erase_append [LawfulBEq α] {a : α} {xs ys : Array α} :
     (xs ++ ys).erase a = if a ∈ xs then xs.erase a ++ ys else xs ++ ys.erase a := by
   rcases xs with ⟨xs⟩
@@ -258,6 +271,7 @@ theorem erase_append [LawfulBEq α] {a : α} {xs ys : Array α} :
   simp only [List.append_toArray, List.erase_toArray, List.erase_append, mem_toArray]
   split <;> simp
 
+@[grind =]
 theorem erase_replicate [LawfulBEq α] {n : Nat} {a b : α} :
     (replicate n a).erase b = if b == a then replicate (n - 1) a else replicate n a := by
   simp only [← List.toArray_replicate, List.erase_toArray]
@@ -269,6 +283,7 @@ abbrev erase_mkArray := @erase_replicate
 
 -- The arguments `a b` are explicit,
 -- so they can be specified to prevent `simp` repeatedly applying the lemma.
+@[grind =]
 theorem erase_comm [LawfulBEq α] (a b : α) {xs : Array α} :
     (xs.erase a).erase b = (xs.erase b).erase a := by
   rcases xs with ⟨xs⟩
@@ -312,6 +327,7 @@ theorem eraseIdx_eq_eraseIdxIfInBounds {xs : Array α} {i : Nat} (h : i < xs.siz
     xs.eraseIdx i h = xs.eraseIdxIfInBounds i := by
   simp [eraseIdxIfInBounds, h]
 
+@[grind =]
 theorem eraseIdx_eq_take_drop_succ {xs : Array α} {i : Nat} (h) :
     xs.eraseIdx i h = xs.take i ++ xs.drop (i + 1) := by
   rcases xs with ⟨xs⟩
@@ -322,6 +338,7 @@ theorem eraseIdx_eq_take_drop_succ {xs : Array α} {i : Nat} (h) :
   rw [List.take_of_length_le]
   simp
 
+@[grind =]
 theorem getElem?_eraseIdx {xs : Array α} {i : Nat} (h : i < xs.size) {j : Nat} :
     (xs.eraseIdx i)[j]? = if j < i then xs[j]? else xs[j + 1]? := by
   rcases xs with ⟨xs⟩
@@ -339,6 +356,7 @@ theorem getElem?_eraseIdx_of_ge {xs : Array α} {i : Nat} (h : i < xs.size) {j :
   intro h'
   omega
 
+@[grind =]
 theorem getElem_eraseIdx {xs : Array α} {i : Nat} (h : i < xs.size) {j : Nat} (h' : j < (xs.eraseIdx i).size) :
     (xs.eraseIdx i)[j] = if h'' : j < i then
         xs[j]
@@ -362,6 +380,7 @@ theorem eraseIdx_ne_empty_iff {xs : Array α} {i : Nat} {h} : xs.eraseIdx i ≠
     simp [h]
   · simp
 
+@[grind →]
 theorem mem_of_mem_eraseIdx {xs : Array α} {i : Nat} {h} {a : α} (h : a ∈ xs.eraseIdx i) : a ∈ xs := by
   rcases xs with ⟨xs⟩
   simpa using List.mem_of_mem_eraseIdx (by simpa using h)
@@ -373,13 +392,29 @@ theorem eraseIdx_append_of_lt_size {xs : Array α} {k : Nat} (hk : k < xs.size)
   simp at hk
   simp [List.eraseIdx_append_of_lt_length, *]
 
-theorem eraseIdx_append_of_length_le {xs : Array α} {k : Nat} (hk : xs.size ≤ k) (ys : Array α) (h) :
+theorem eraseIdx_append_of_size_le {xs : Array α} {k : Nat} (hk : xs.size ≤ k) (ys : Array α) (h) :
     eraseIdx (xs ++ ys) k = xs ++ eraseIdx ys (k - xs.size) (by simp at h; omega) := by
   rcases xs with ⟨l⟩
   rcases ys with ⟨l'⟩
   simp at hk
   simp [List.eraseIdx_append_of_length_le, *]
 
+@[deprecated eraseIdx_append_of_size_le (since := "2025-06-11")]
+abbrev eraseIdx_append_of_length_le := @eraseIdx_append_of_size_le
+
+@[grind =]
+theorem eraseIdx_append {xs ys : Array α} (h : k < (xs ++ ys).size) :
+    eraseIdx (xs ++ ys) k =
+      if h' : k < xs.size then
+        eraseIdx xs k ++ ys
+      else
+        xs ++ eraseIdx ys (k - xs.size) (by simp at h; omega) := by
+  split <;> rename_i h
+  · simp [eraseIdx_append_of_lt_size h]
+  · rw [eraseIdx_append_of_size_le]
+    omega
+
+@[grind =]
 theorem eraseIdx_replicate {n : Nat} {a : α} {k : Nat} {h} :
     (replicate n a).eraseIdx k = replicate (n - 1) a := by
   simp at h
@@ -428,6 +463,48 @@ theorem eraseIdx_set_gt {xs : Array α} {i : Nat} {j : Nat} {a : α} (h : i < j)
   rcases xs with ⟨xs⟩
   simp [List.eraseIdx_set_gt, *]
 
+@[grind =]
+theorem eraseIdx_set {xs : Array α} {i : Nat} {a : α} {hi : i < xs.size} {j : Nat} {hj : j < (xs.set i a).size} :
+    (xs.set i a).eraseIdx j =
+      if h' : j < i then
+        (xs.eraseIdx j).set (i - 1) a (by simp; omega)
+      else if h'' : j = i then
+        xs.eraseIdx i
+      else
+        (xs.eraseIdx j (by simp at hj; omega)).set i a (by simp at hj ⊢; omega) := by
+  split <;> rename_i h'
+  · rw [eraseIdx_set_lt]
+    omega
+  · split <;> rename_i h''
+    · subst h''
+      rw [eraseIdx_set_eq]
+    · rw [eraseIdx_set_gt]
+      omega
+
+theorem set_eraseIdx_le {xs : Array α} {i : Nat} {w : i < xs.size} {j : Nat} {a : α} (h : i ≤ j) (hj : j < (xs.eraseIdx i).size) :
+    (xs.eraseIdx i).set j a = (xs.set (j + 1) a (by simp at hj; omega)).eraseIdx i (by simp at ⊢; omega) := by
+  rw [eraseIdx_set_lt]
+  · simp
+  · omega
+
+theorem set_eraseIdx_gt {xs : Array α} {i : Nat} {w : i < xs.size} {j : Nat} {a : α} (h : j < i) (hj : j < (xs.eraseIdx i).size) :
+    (xs.eraseIdx i).set j a = (xs.set j a).eraseIdx i (by simp at ⊢; omega) := by
+  rw [eraseIdx_set_gt]
+  omega
+
+@[grind =]
+theorem set_eraseIdx {xs : Array α} {i : Nat} {w : i < xs.size} {j : Nat} {a : α} (hj : j < (xs.eraseIdx i).size) :
+    (xs.eraseIdx i).set j a =
+      if h' : i ≤ j then
+        (xs.set (j + 1) a (by simp at hj; omega)).eraseIdx i (by simp at ⊢; omega)
+      else
+        (xs.set j a).eraseIdx i (by simp at ⊢; omega) := by
+  split <;> rename_i h'
+  · rw [set_eraseIdx_le]
+    omega
+  · rw [set_eraseIdx_gt]
+    omega
+
 @[simp] theorem set_getElem_succ_eraseIdx_succ
     {xs : Array α} {i : Nat} (h : i + 1 < xs.size) :
     (xs.eraseIdx (i + 1)).set i xs[i + 1] (by simp; omega) = xs.eraseIdx i := by

src/Init/Data/Array/Extract.lean

@@ -46,7 +46,7 @@ theorem size_extract_of_le {as : Array α} {i j : Nat} (h : j ≤ as.size) :
   simp
   omega
 
-@[simp]
+@[simp, grind =]
 theorem extract_push {as : Array α} {b : α} {start stop : Nat} (h : stop ≤ as.size) :
     (as.push b).extract start stop = as.extract start stop := by
   ext i h₁ h₂
@@ -56,7 +56,7 @@ theorem extract_push {as : Array α} {b : α} {start stop : Nat} (h : stop ≤ a
     simp only [getElem_extract, getElem_push]
     rw [dif_pos (by omega)]
 
-@[simp]
+@[simp, grind =]
 theorem extract_eq_pop {as : Array α} {stop : Nat} (h : stop = as.size - 1) :
     as.extract 0 stop = as.pop := by
   ext i h₁ h₂
@@ -65,7 +65,7 @@ theorem extract_eq_pop {as : Array α} {stop : Nat} (h : stop = as.size - 1) :
   · simp only [size_extract, size_pop] at h₁ h₂
     simp [getElem_extract, getElem_pop]
 
-@[simp]
+@[simp, grind _=_]
 theorem extract_append_extract {as : Array α} {i j k : Nat} :
     as.extract i j ++ as.extract j k = as.extract (min i j) (max j k) := by
   ext l h₁ h₂
@@ -169,7 +169,7 @@ theorem getElem?_extract_of_succ {as : Array α} {j : Nat} :
   simp [getElem?_extract]
   omega
 
-@[simp] theorem extract_extract {as : Array α} {i j k l : Nat} :
+@[simp, grind =] theorem extract_extract {as : Array α} {i j k l : Nat} :
     (as.extract i j).extract k l = as.extract (i + k) (min (i + l) j) := by
   ext m h₁ h₂
   · simp
@@ -185,6 +185,7 @@ theorem ne_empty_of_extract_ne_empty {as : Array α} {i j : Nat} (h : as.extract
     as ≠ #[] :=
   mt extract_eq_empty_of_eq_empty h
 
+@[grind =]
 theorem extract_set {as : Array α} {i j k : Nat} (h : k < as.size) {a : α} :
     (as.set k a).extract i j =
       if _ : k < i then
@@ -211,13 +212,14 @@ theorem extract_set {as : Array α} {i j k : Nat} (h : k < as.size) {a : α} :
         simp [getElem_set]
         omega
 
+@[grind =]
 theorem set_extract {as : Array α} {i j k : Nat} (h : k < (as.extract i j).size) {a : α} :
     (as.extract i j).set k a = (as.set (i + k) a (by simp at h; omega)).extract i j := by
   ext l h₁ h₂
   · simp
   · simp_all [getElem_set]
 
-@[simp]
+@[simp, grind =]
 theorem extract_append {as bs : Array α} {i j : Nat} :
     (as ++ bs).extract i j = as.extract i j ++ bs.extract (i - as.size) (j - as.size) := by
   ext l h₁ h₂
@@ -238,20 +240,18 @@ theorem extract_append_left {as bs : Array α} :
     (as ++ bs).extract 0 as.size = as.extract 0 as.size := by
   simp
 
-@[simp] theorem extract_append_right {as bs : Array α} :
+theorem extract_append_right {as bs : Array α} :
     (as ++ bs).extract as.size (as.size + i) = bs.extract 0 i := by
-  simp only [extract_append, extract_size_left, Nat.sub_self, empty_append]
-  congr 1
-  omega
+  simp
 
-@[simp] theorem map_extract {as : Array α} {i j : Nat} :
+@[simp, grind =] theorem map_extract {as : Array α} {i j : Nat} :
     (as.extract i j).map f = (as.map f).extract i j := by
   ext l h₁ h₂
   · simp
   · simp only [size_map, size_extract] at h₁ h₂
     simp only [getElem_map, getElem_extract]
 
-@[simp] theorem extract_replicate {a : α} {n i j : Nat} :
+@[simp, grind =] theorem extract_replicate {a : α} {n i j : Nat} :
     (replicate n a).extract i j = replicate (min j n - i) a := by
   ext l h₁ h₂
   · simp
@@ -299,6 +299,7 @@ theorem set_eq_push_extract_append_extract {as : Array α} {i : Nat} (h : i < as
   simp at h
   simp [List.set_eq_take_append_cons_drop, h, List.take_of_length_le]
 
+@[grind =]
 theorem extract_reverse {as : Array α} {i j : Nat} :
     as.reverse.extract i j = (as.extract (as.size - j) (as.size - i)).reverse := by
   ext l h₁ h₂
@@ -309,6 +310,7 @@ theorem extract_reverse {as : Array α} {i j : Nat} :
     congr 1
     omega
 
+@[grind =]
 theorem reverse_extract {as : Array α} {i j : Nat} :
     (as.extract i j).reverse = as.reverse.extract (as.size - j) (as.size - i) := by
   rw [extract_reverse]

src/Init/Data/Array/FinRange.lean

@@ -23,10 +23,10 @@ Examples:
 -/
 protected def finRange (n : Nat) : Array (Fin n) := ofFn fun i => i
 
-@[simp] theorem size_finRange {n} : (Array.finRange n).size = n := by
+@[simp, grind =] theorem size_finRange {n} : (Array.finRange n).size = n := by
   simp [Array.finRange]
 
-@[simp] theorem getElem_finRange {i : Nat} (h : i < (Array.finRange n).size) :
+@[simp, grind =] theorem getElem_finRange {i : Nat} (h : i < (Array.finRange n).size) :
     (Array.finRange n)[i] = Fin.cast size_finRange ⟨i, h⟩ := by
   simp [Array.finRange]
 
@@ -49,6 +49,7 @@ theorem finRange_succ_last {n} :
     · simp_all
       omega
 
+@[grind _=_]
 theorem finRange_reverse {n} : (Array.finRange n).reverse = (Array.finRange n).map Fin.rev := by
   ext i h
   · simp

src/Init/Data/Array/Find.lean

@@ -38,11 +38,22 @@ theorem findSome?_singleton {a : α} {f : α → Option β} : #[a].findSome? f =
 @[simp] theorem findSomeRev?_push_of_isNone {xs : Array α} (h : (f a).isNone) : (xs.push a).findSomeRev? f = xs.findSomeRev? f := by
   cases xs; simp_all
 
+@[grind =]
+theorem findSomeRev?_push {xs : Array α} {a : α} {f : α → Option β} :
+    (xs.push a).findSomeRev? f = (f a).or (xs.findSomeRev? f) := by
+  match h : f a with
+  | some b =>
+    rw [findSomeRev?_push_of_isSome]
+    all_goals simp_all
+  | none =>
+    rw [findSomeRev?_push_of_isNone]
+    all_goals simp_all
+
 theorem exists_of_findSome?_eq_some {f : α → Option β} {xs : Array α} (w : xs.findSome? f = some b) :
     ∃ a, a ∈ xs ∧ f a = some b := by
   cases xs; simp_all [List.exists_of_findSome?_eq_some]
 
-@[simp] theorem findSome?_eq_none_iff : findSome? p xs = none ↔ ∀ x ∈ xs, p x = none := by
+@[simp, grind =] theorem findSome?_eq_none_iff : findSome? p xs = none ↔ ∀ x ∈ xs, p x = none := by
   cases xs; simp
 
 @[simp] theorem findSome?_isSome_iff {f : α → Option β} {xs : Array α} :
@@ -59,36 +70,39 @@ theorem findSome?_eq_some_iff {f : α → Option β} {xs : Array α} {b : β} :
   · rintro ⟨xs, a, ys, h₀, h₁, h₂⟩
     exact ⟨xs.toList, a, ys.toList, by simpa using congrArg toList h₀, h₁, by simpa⟩
 
-@[simp] theorem findSome?_guard {xs : Array α} : findSome? (Option.guard fun x => p x) xs = find? p xs := by
+@[simp, grind =] theorem findSome?_guard {xs : Array α} : findSome? (Option.guard p) xs = find? p xs := by
   cases xs; simp
 
-theorem find?_eq_findSome?_guard {xs : Array α} : find? p xs = findSome? (Option.guard fun x => p x) xs :=
+theorem find?_eq_findSome?_guard {xs : Array α} : find? p xs = findSome? (Option.guard p) xs :=
   findSome?_guard.symm
 
-@[simp] theorem getElem?_zero_filterMap {f : α → Option β} {xs : Array α} : (xs.filterMap f)[0]? = xs.findSome? f := by
+@[simp, grind =] theorem getElem?_zero_filterMap {f : α → Option β} {xs : Array α} : (xs.filterMap f)[0]? = xs.findSome? f := by
   cases xs; simp [← List.head?_eq_getElem?]
 
-@[simp] theorem getElem_zero_filterMap {f : α → Option β} {xs : Array α} (h) :
+@[simp, grind =] theorem getElem_zero_filterMap {f : α → Option β} {xs : Array α} (h) :
     (xs.filterMap f)[0] = (xs.findSome? f).get (by cases xs; simpa [List.length_filterMap_eq_countP] using h) := by
   cases xs; simp [← List.head_eq_getElem, ← getElem?_zero_filterMap]
 
-@[simp] theorem back?_filterMap {f : α → Option β} {xs : Array α} : (xs.filterMap f).back? = xs.findSomeRev? f := by
+@[simp, grind =] theorem back?_filterMap {f : α → Option β} {xs : Array α} : (xs.filterMap f).back? = xs.findSomeRev? f := by
   cases xs; simp
 
-@[simp] theorem back!_filterMap [Inhabited β] {f : α → Option β} {xs : Array α} :
+@[simp, grind =] theorem back!_filterMap [Inhabited β] {f : α → Option β} {xs : Array α} :
     (xs.filterMap f).back! = (xs.findSomeRev? f).getD default := by
   cases xs; simp
 
-@[simp] theorem map_findSome? {f : α → Option β} {g : β → γ} {xs : Array α} :
+@[simp, grind _=_] theorem map_findSome? {f : α → Option β} {g : β → γ} {xs : Array α} :
     (xs.findSome? f).map g = xs.findSome? (Option.map g ∘ f) := by
   cases xs; simp
 
+@[grind _=_]
 theorem findSome?_map {f : β → γ} {xs : Array β} : findSome? p (xs.map f) = xs.findSome? (p ∘ f) := by
   cases xs; simp [List.findSome?_map]
 
+@[grind =]
 theorem findSome?_append {xs ys : Array α} : (xs ++ ys).findSome? f = (xs.findSome? f).or (ys.findSome? f) := by
   cases xs; cases ys; simp [List.findSome?_append]
 
+@[grind =]
 theorem getElem?_zero_flatten (xss : Array (Array α)) :
     (flatten xss)[0]? = xss.findSome? fun xs => xs[0]? := by
   cases xss using array₂_induction
@@ -104,12 +118,14 @@ theorem getElem_zero_flatten.proof {xss : Array (Array α)} (h : 0 < xss.flatten
   obtain ⟨_, ⟨xs, m, rfl⟩, h⟩ := h
   exact ⟨xs, m, by simpa using h⟩
 
+@[grind =]
 theorem getElem_zero_flatten {xss : Array (Array α)} (h) :
     (flatten xss)[0] = (xss.findSome? fun xs => xs[0]?).get (getElem_zero_flatten.proof h) := by
   have t := getElem?_zero_flatten xss
   simp [getElem?_eq_getElem, h] at t
   simp [← t]
 
+@[grind =]
 theorem findSome?_replicate : findSome? f (replicate n a) = if n = 0 then none else f a := by
   simp [← List.toArray_replicate, List.findSome?_replicate]
 
@@ -140,21 +156,37 @@ abbrev findSome?_mkArray_of_isNone := @findSome?_replicate_of_isNone
 
 /-! ### find? -/
 
-@[simp] theorem find?_empty : find? p #[] = none := rfl
+@[simp, grind =] theorem find?_empty : find? p #[] = none := rfl
 
-@[simp] theorem find?_singleton {a : α} {p : α → Bool} :
+@[grind =]
+theorem find?_singleton {a : α} {p : α → Bool} :
     #[a].find? p = if p a then some a else none := by
-  simp [singleton_eq_toArray_singleton]
+  simp
 
 @[simp] theorem findRev?_push_of_pos {xs : Array α} (h : p a) :
     findRev? p (xs.push a) = some a := by
   cases xs; simp [h]
 
-@[simp] theorem findRev?_cons_of_neg {xs : Array α} (h : ¬p a) :
+@[simp] theorem findRev?_push_of_neg {xs : Array α} (h : ¬p a) :
     findRev? p (xs.push a) = findRev? p xs := by
   cases xs; simp [h]
 
-@[simp] theorem find?_eq_none : find? p xs = none ↔ ∀ x ∈ xs, ¬ p x := by
+@[deprecated findRev?_push_of_neg (since := "2025-06-12")]
+abbrev findRev?_cons_of_neg := @findRev?_push_of_neg
+
+@[grind =]
+theorem finRev?_push {xs : Array α} :
+    findRev? p (xs.push a) = (Option.guard p a).or (xs.findRev? p) := by
+  cases h : p a
+  · rw [findRev?_push_of_neg, Option.guard_eq_none_iff.mpr h]
+    all_goals simp [h]
+  · rw [findRev?_push_of_pos, Option.guard_eq_some_iff.mpr ⟨rfl, h⟩]
+    all_goals simp [h]
+
+@[deprecated finRev?_push (since := "2025-06-12")]
+abbrev findRev?_cons := @finRev?_push
+
+@[simp, grind =] theorem find?_eq_none : find? p xs = none ↔ ∀ x ∈ xs, ¬ p x := by
   cases xs; simp
 
 theorem find?_eq_some_iff_append {xs : Array α} :
@@ -178,60 +210,63 @@ theorem find?_push_eq_some {xs : Array α} :
     (xs.push a).find? p = some b ↔ xs.find? p = some b ∨ (xs.find? p = none ∧ (p a ∧ a = b)) := by
   cases xs; simp
 
-@[simp] theorem find?_isSome {xs : Array α} {p : α → Bool} : (xs.find? p).isSome ↔ ∃ x, x ∈ xs ∧ p x := by
+@[simp, grind =] theorem find?_isSome {xs : Array α} {p : α → Bool} : (xs.find? p).isSome ↔ ∃ x, x ∈ xs ∧ p x := by
   cases xs; simp
 
+@[grind →]
 theorem find?_some {xs : Array α} (h : find? p xs = some a) : p a := by
   cases xs
   simp at h
   exact List.find?_some h
 
+@[grind →]
 theorem mem_of_find?_eq_some {xs : Array α} (h : find? p xs = some a) : a ∈ xs := by
   cases xs
   simp at h
   simpa using List.mem_of_find?_eq_some h
 
+@[grind]
 theorem get_find?_mem {xs : Array α} (h) : (xs.find? p).get h ∈ xs := by
   cases xs
   simp [List.get_find?_mem]
 
-@[simp] theorem find?_filter {xs : Array α} (p q : α → Bool) :
+@[simp, grind =] theorem find?_filter {xs : Array α} (p q : α → Bool) :
     (xs.filter p).find? q = xs.find? (fun a => p a ∧ q a) := by
   cases xs; simp
 
-@[simp] theorem getElem?_zero_filter {p : α → Bool} {xs : Array α} :
+@[simp, grind =] theorem getElem?_zero_filter {p : α → Bool} {xs : Array α} :
     (xs.filter p)[0]? = xs.find? p := by
   cases xs; simp [← List.head?_eq_getElem?]
 
-@[simp] theorem getElem_zero_filter {p : α → Bool} {xs : Array α} (h) :
+@[simp, grind =] theorem getElem_zero_filter {p : α → Bool} {xs : Array α} (h) :
     (xs.filter p)[0] =
       (xs.find? p).get (by cases xs; simpa [← List.countP_eq_length_filter] using h) := by
   cases xs
   simp [List.getElem_zero_eq_head]
 
-@[simp] theorem back?_filter {p : α → Bool} {xs : Array α} : (xs.filter p).back? = xs.findRev? p := by
+@[simp, grind =] theorem back?_filter {p : α → Bool} {xs : Array α} : (xs.filter p).back? = xs.findRev? p := by
   cases xs; simp
 
-@[simp] theorem back!_filter [Inhabited α] {p : α → Bool} {xs : Array α} :
+@[simp, grind =] theorem back!_filter [Inhabited α] {p : α → Bool} {xs : Array α} :
     (xs.filter p).back! = (xs.findRev? p).get! := by
   cases xs; simp [Option.get!_eq_getD]
 
-@[simp] theorem find?_filterMap {xs : Array α} {f : α → Option β} {p : β → Bool} :
+@[simp, grind =] theorem find?_filterMap {xs : Array α} {f : α → Option β} {p : β → Bool} :
     (xs.filterMap f).find? p = (xs.find? (fun a => (f a).any p)).bind f := by
   cases xs; simp
 
-@[simp] theorem find?_map {f : β → α} {xs : Array β} :
+@[simp, grind =] theorem find?_map {f : β → α} {xs : Array β} :
     find? p (xs.map f) = (xs.find? (p ∘ f)).map f := by
   cases xs; simp
 
-@[simp] theorem find?_append {xs ys : Array α} :
+@[simp, grind =] theorem find?_append {xs ys : Array α} :
     (xs ++ ys).find? p = (xs.find? p).or (ys.find? p) := by
   cases xs
   cases ys
   simp
 
-@[simp] theorem find?_flatten {xss : Array (Array α)} {p : α → Bool} :
-    xss.flatten.find? p = xss.findSome? (·.find? p) := by
+@[simp, grind _=_] theorem find?_flatten {xss : Array (Array α)} {p : α → Bool} :
+    xss.flatten.find? p = xss.findSome? (find? p) := by
   cases xss using array₂_induction
   simp [List.findSome?_map, Function.comp_def]
 
@@ -270,7 +305,7 @@ theorem find?_flatten_eq_some_iff {xss : Array (Array α)} {p : α → Bool} {a
 @[deprecated find?_flatten_eq_some_iff (since := "2025-02-03")]
 abbrev find?_flatten_eq_some := @find?_flatten_eq_some_iff
 
-@[simp] theorem find?_flatMap {xs : Array α} {f : α → Array β} {p : β → Bool} :
+@[simp, grind =] theorem find?_flatMap {xs : Array α} {f : α → Array β} {p : β → Bool} :
     (xs.flatMap f).find? p = xs.findSome? (fun x => (f x).find? p) := by
   cases xs
   simp [List.find?_flatMap, Array.flatMap_toArray]
@@ -282,6 +317,7 @@ theorem find?_flatMap_eq_none_iff {xs : Array α} {f : α → Array β} {p : β
 @[deprecated find?_flatMap_eq_none_iff (since := "2025-02-03")]
 abbrev find?_flatMap_eq_none := @find?_flatMap_eq_none_iff
 
+@[grind =]
 theorem find?_replicate :
     find? p (replicate n a) = if n = 0 then none else if p a then some a else none := by
   simp [← List.toArray_replicate, List.find?_replicate]
@@ -334,6 +370,7 @@ abbrev find?_mkArray_eq_some := @find?_replicate_eq_some_iff
 @[deprecated get_find?_replicate (since := "2025-03-18")]
 abbrev get_find?_mkArray := @get_find?_replicate
 
+@[grind =]
 theorem find?_pmap {P : α → Prop} {f : (a : α) → P a → β} {xs : Array α}
     (H : ∀ (a : α), a ∈ xs → P a) {p : β → Bool} :
     (xs.pmap f H).find? p = (xs.attach.find? (fun ⟨a, m⟩ => p (f a (H a m)))).map fun ⟨a, m⟩ => f a (H a m) := by
@@ -347,11 +384,15 @@ theorem find?_eq_some_iff_getElem {xs : Array α} {p : α → Bool} {b : α} :
 
 /-! ### findIdx -/
 
-@[simp] theorem findIdx_empty : findIdx p #[] = 0 := rfl
+@[grind =]
+theorem findIdx_empty : findIdx p #[] = 0 := rfl
+
+@[grind =]
 theorem findIdx_singleton {a : α} {p : α → Bool} :
     #[a].findIdx p = if p a then 0 else 1 := by
   simp
 
+@[grind →]
 theorem findIdx_of_getElem?_eq_some {xs : Array α} (w : xs[xs.findIdx p]? = some y) : p y := by
   rcases xs with ⟨xs⟩
   exact List.findIdx_of_getElem?_eq_some (by simpa using w)
@@ -360,6 +401,8 @@ theorem findIdx_getElem {xs : Array α} {w : xs.findIdx p < xs.size} :
     p xs[xs.findIdx p] :=
   xs.findIdx_of_getElem?_eq_some (getElem?_eq_getElem w)
 
+grind_pattern findIdx_getElem => xs[xs.findIdx p]
+
 theorem findIdx_lt_size_of_exists {xs : Array α} (h : ∃ x ∈ xs, p x) :
     xs.findIdx p < xs.size := by
   rcases xs with ⟨xs⟩
@@ -386,18 +429,24 @@ theorem findIdx_le_size {p : α → Bool} {xs : Array α} : xs.findIdx p ≤ xs.
   · simp at e
     exact Nat.le_of_eq (findIdx_eq_size.mpr e)
 
+grind_pattern findIdx_le_size => xs.findIdx p, xs.size
+
 @[simp]
 theorem findIdx_lt_size {p : α → Bool} {xs : Array α} :
     xs.findIdx p < xs.size ↔ ∃ x ∈ xs, p x := by
   rcases xs with ⟨xs⟩
   simp
 
+grind_pattern findIdx_lt_size => xs.findIdx p, xs.size
+
 /-- `p` does not hold for elements with indices less than `xs.findIdx p`. -/
 theorem not_of_lt_findIdx {p : α → Bool} {xs : Array α} {i : Nat} (h : i < xs.findIdx p) :
     p (xs[i]'(Nat.le_trans h findIdx_le_size)) = false := by
   rcases xs with ⟨xs⟩
   simpa using List.not_of_lt_findIdx (by simpa using h)
 
+grind_pattern not_of_lt_findIdx => xs.findIdx p, xs[i]
+
 /-- If `¬ p xs[j]` for all `j < i`, then `i ≤ xs.findIdx p`. -/
 theorem le_findIdx_of_not {p : α → Bool} {xs : Array α} {i : Nat} (h : i < xs.size)
     (h2 : ∀ j (hji : j < i), p (xs[j]'(Nat.lt_trans hji h)) = false) : i ≤ xs.findIdx p := by
@@ -425,6 +474,7 @@ theorem findIdx_eq {p : α → Bool} {xs : Array α} {i : Nat} (h : i < xs.size)
   simp at h3
   simp_all [not_of_lt_findIdx h3]
 
+@[grind =]
 theorem findIdx_append {p : α → Bool} {xs ys : Array α} :
     (xs ++ ys).findIdx p =
       if xs.findIdx p < xs.size then xs.findIdx p else ys.findIdx p + xs.size := by
@@ -432,6 +482,7 @@ theorem findIdx_append {p : α → Bool} {xs ys : Array α} :
   rcases ys with ⟨ys⟩
   simp [List.findIdx_append]
 
+@[grind =]
 theorem findIdx_push {xs : Array α} {a : α} {p : α → Bool} :
     (xs.push a).findIdx p = if xs.findIdx p < xs.size then xs.findIdx p else xs.size + if p a then 0 else 1 := by
   simp only [push_eq_append, findIdx_append]
@@ -454,7 +505,7 @@ theorem false_of_mem_extract_findIdx {xs : Array α} {p : α → Bool} (h : x
   rcases xs with ⟨xs⟩
   exact List.false_of_mem_take_findIdx (by simpa using h)
 
-@[simp] theorem findIdx_extract {xs : Array α} {i : Nat} {p : α → Bool} :
+@[simp, grind =] theorem findIdx_extract {xs : Array α} {i : Nat} {p : α → Bool} :
     (xs.extract 0 i).findIdx p = min i (xs.findIdx p) := by
   cases xs
   simp
@@ -466,24 +517,24 @@ theorem false_of_mem_extract_findIdx {xs : Array α} {p : α → Bool} (h : x
 
 /-! ### findIdx? -/
 
-@[simp] theorem findIdx?_empty : (#[] : Array α).findIdx? p = none := by simp
-theorem findIdx?_singleton {a : α} {p : α → Bool} :
+@[simp, grind =] theorem findIdx?_empty : (#[] : Array α).findIdx? p = none := by simp
+@[grind =] theorem findIdx?_singleton {a : α} {p : α → Bool} :
     #[a].findIdx? p = if p a then some 0 else none := by
   simp
 
-@[simp]
+@[simp, grind =]
 theorem findIdx?_eq_none_iff {xs : Array α} {p : α → Bool} :
     xs.findIdx? p = none ↔ ∀ x, x ∈ xs → p x = false := by
   rcases xs with ⟨xs⟩
   simp
 
-@[simp]
+@[simp, grind =]
 theorem findIdx?_isSome {xs : Array α} {p : α → Bool} :
     (xs.findIdx? p).isSome = xs.any p := by
   rcases xs with ⟨xs⟩
   simp [List.findIdx?_isSome]
 
-@[simp]
+@[simp, grind =]
 theorem findIdx?_isNone {xs : Array α} {p : α → Bool} :
     (xs.findIdx? p).isNone = xs.all (¬p ·) := by
   rcases xs with ⟨xs⟩
@@ -525,18 +576,19 @@ theorem of_findIdx?_eq_none {xs : Array α} {p : α → Bool} (w : xs.findIdx? p
   rcases xs with ⟨xs⟩
   simpa using List.of_findIdx?_eq_none (by simpa using w)
 
-@[simp] theorem findIdx?_map {f : β → α} {xs : Array β} {p : α → Bool} :
+@[simp, grind =] theorem findIdx?_map {f : β → α} {xs : Array β} {p : α → Bool} :
     findIdx? p (xs.map f) = xs.findIdx? (p ∘ f) := by
   rcases xs with ⟨xs⟩
   simp [List.findIdx?_map]
 
-@[simp] theorem findIdx?_append :
+@[simp, grind =] theorem findIdx?_append :
     (xs ++ ys : Array α).findIdx? p =
       (xs.findIdx? p).or ((ys.findIdx? p).map fun i => i + xs.size) := by
   rcases xs with ⟨xs⟩
   rcases ys with ⟨ys⟩
   simp [List.findIdx?_append]
 
+@[grind =]
 theorem findIdx?_push {xs : Array α} {a : α} {p : α → Bool} :
     (xs.push a).findIdx? p = (xs.findIdx? p).or (if p a then some xs.size else none) := by
   simp only [push_eq_append, findIdx?_append]
@@ -552,7 +604,7 @@ theorem findIdx?_flatten {xss : Array (Array α)} {p : α → Bool} :
   cases xss using array₂_induction
   simp [List.findIdx?_flatten, Function.comp_def]
 
-@[simp] theorem findIdx?_replicate :
+@[simp, grind =] theorem findIdx?_replicate :
     (replicate n a).findIdx? p = if 0 < n ∧ p a then some 0 else none := by
   rw [← List.toArray_replicate]
   simp only [List.findIdx?_toArray]
@@ -577,6 +629,7 @@ theorem findIdx?_eq_none_of_findIdx?_eq_none {xs : Array α} {p q : α → Bool}
   rcases xs with ⟨xs⟩
   simpa using List.findIdx?_eq_none_of_findIdx?_eq_none (by simpa using w)
 
+@[grind =]
 theorem findIdx_eq_getD_findIdx? {xs : Array α} {p : α → Bool} :
     xs.findIdx p = (xs.findIdx? p).getD xs.size := by
   rcases xs with ⟨xs⟩
@@ -593,14 +646,17 @@ theorem findIdx?_eq_some_le_of_findIdx?_eq_some {xs : Array α} {p q : α → Bo
   cases xs
   simp [hf]
 
-@[simp] theorem findIdx?_take {xs : Array α} {i : Nat} {p : α → Bool} :
+@[simp, grind =] theorem findIdx?_take {xs : Array α} {i : Nat} {p : α → Bool} :
     (xs.take i).findIdx? p = (xs.findIdx? p).bind (Option.guard (fun j => j < i)) := by
   cases xs
   simp
 
 /-! ### findFinIdx? -/
 
-@[simp] theorem findFinIdx?_empty {p : α → Bool} : findFinIdx? p #[] = none := by simp
+@[grind =]
+theorem findFinIdx?_empty {p : α → Bool} : findFinIdx? p #[] = none := by simp
+
+@[grind =]
 theorem findFinIdx?_singleton {a : α} {p : α → Bool} :
     #[a].findFinIdx? p = if p a then some ⟨0, by simp⟩ else none := by
   simp
@@ -618,7 +674,7 @@ theorem findFinIdx?_eq_pmap_findIdx? {xs : Array α} {p : α → Bool} :
         (fun i h => h) := by
   simp [findIdx?_eq_map_findFinIdx?_val, Option.pmap_map]
 
-@[simp] theorem findFinIdx?_eq_none_iff {xs : Array α} {p : α → Bool} :
+@[simp, grind =] theorem findFinIdx?_eq_none_iff {xs : Array α} {p : α → Bool} :
     xs.findFinIdx? p = none ↔ ∀ x, x ∈ xs → ¬ p x := by
   simp [findFinIdx?_eq_pmap_findIdx?]
 
@@ -634,12 +690,14 @@ theorem findFinIdx?_eq_some_iff {xs : Array α} {p : α → Bool} {i : Fin xs.si
   · rintro ⟨h, w⟩
     exact ⟨i, ⟨i.2, h, fun j hji => w ⟨j, by omega⟩ hji⟩, rfl⟩
 
+@[grind =]
 theorem findFinIdx?_push {xs : Array α} {a : α} {p : α → Bool} :
     (xs.push a).findFinIdx? p =
       ((xs.findFinIdx? p).map (Fin.castLE (by simp))).or (if p a then some ⟨xs.size, by simp⟩ else none) := by
   simp only [findFinIdx?_eq_pmap_findIdx?, findIdx?_push, Option.pmap_or]
   split <;> rename_i h _ <;> split <;> simp [h]
 
+@[grind =]
 theorem findFinIdx?_append {xs ys : Array α} {p : α → Bool} :
     (xs ++ ys).findFinIdx? p =
       ((xs.findFinIdx? p).map (Fin.castLE (by simp))).or
@@ -649,17 +707,17 @@ theorem findFinIdx?_append {xs ys : Array α} {p : α → Bool} :
   · simp [h, Option.pmap_map, Option.map_pmap, Nat.add_comm]
   · simp [h]
 
-@[simp]
+@[simp, grind =]
 theorem isSome_findFinIdx? {xs : Array α} {p : α → Bool} :
     (xs.findFinIdx? p).isSome = xs.any p := by
   rcases xs with ⟨xs⟩
-  simp
+  simp [Array.size]
 
-@[simp]
+@[simp, grind =]
 theorem isNone_findFinIdx? {xs : Array α} {p : α → Bool} :
     (xs.findFinIdx? p).isNone = xs.all (fun x => ¬ p x) := by
   rcases xs with ⟨xs⟩
-  simp
+  simp [Array.size]
 
 @[simp] theorem findFinIdx?_subtype {p : α → Prop} {xs : Array { x // p x }}
     {f : { x // p x } → Bool} {g : α → Bool} (hf : ∀ x h, f ⟨x, h⟩ = g x) :
@@ -667,7 +725,8 @@ theorem isNone_findFinIdx? {xs : Array α} {p : α → Bool} :
   cases xs
   simp only [List.findFinIdx?_toArray, hf, List.findFinIdx?_subtype]
   rw [findFinIdx?_congr List.unattach_toArray]
-  simp [Function.comp_def]
+  simp only [Option.map_map, Function.comp_def, Fin.cast_trans]
+  simp [Array.size]
 
 /-! ### idxOf
 
@@ -675,6 +734,7 @@ The verification API for `idxOf` is still incomplete.
 The lemmas below should be made consistent with those for `findIdx` (and proved using them).
 -/
 
+@[grind =]
 theorem idxOf_append [BEq α] [LawfulBEq α] {xs ys : Array α} {a : α} :
     (xs ++ ys).idxOf a = if a ∈ xs then xs.idxOf a else ys.idxOf a + xs.size := by
   rw [idxOf, findIdx_append]
@@ -688,10 +748,23 @@ theorem idxOf_eq_size [BEq α] [LawfulBEq α] {xs : Array α} (h : a ∉ xs) : x
   rcases xs with ⟨xs⟩
   simp [List.idxOf_eq_length (by simpa using h)]
 
-theorem idxOf_lt_length [BEq α] [LawfulBEq α] {xs : Array α} (h : a ∈ xs) : xs.idxOf a < xs.size := by
+theorem idxOf_lt_length_of_mem [BEq α] [LawfulBEq α] {xs : Array α} (h : a ∈ xs) : xs.idxOf a < xs.size := by
   rcases xs with ⟨xs⟩
-  simp [List.idxOf_lt_length (by simpa using h)]
+  simp [List.idxOf_lt_length_of_mem (by simpa using h)]
 
+theorem idxOf_le_size [BEq α] [LawfulBEq α] {xs : Array α} {a : α} :
+    xs.idxOf a ≤ xs.size := by
+  rcases xs with ⟨xs⟩
+  simp [List.idxOf_le_length]
+
+grind_pattern idxOf_le_size => xs.idxOf a, xs.size
+
+theorem idxOf_lt_size_iff [BEq α] [LawfulBEq α] {xs : Array α} {a : α} :
+    xs.idxOf a < xs.size ↔ a ∈ xs := by
+  rcases xs with ⟨xs⟩
+  simp [List.idxOf_lt_length_iff]
+
+grind_pattern idxOf_lt_size_iff => xs.idxOf a, xs.size
 
 /-! ### idxOf?
 
@@ -699,27 +772,24 @@ The verification API for `idxOf?` is still incomplete.
 The lemmas below should be made consistent with those for `findIdx?` (and proved using them).
 -/
 
-@[simp] theorem idxOf?_empty [BEq α] : (#[] : Array α).idxOf? a = none := by simp
+@[grind =] theorem idxOf?_empty [BEq α] : (#[] : Array α).idxOf? a = none := by simp
 
-@[simp] theorem idxOf?_eq_none_iff [BEq α] [LawfulBEq α] {xs : Array α} {a : α} :
+@[simp, grind =] theorem idxOf?_eq_none_iff [BEq α] [LawfulBEq α] {xs : Array α} {a : α} :
     xs.idxOf? a = none ↔ a ∉ xs := by
   rcases xs with ⟨xs⟩
   simp [List.idxOf?_eq_none_iff]
 
-@[simp]
+@[simp, grind =]
 theorem isSome_idxOf? [BEq α] [LawfulBEq α] {xs : Array α} {a : α} :
     (xs.idxOf? a).isSome ↔ a ∈ xs := by
   rcases xs with ⟨xs⟩
   simp
 
-@[simp]
+@[grind =]
 theorem isNone_idxOf? [BEq α] [LawfulBEq α] {xs : Array α} {a : α} :
     (xs.idxOf? a).isNone = ¬ a ∈ xs := by
-  rcases xs with ⟨xs⟩
   simp
 
-
-
 /-! ### finIdxOf?
 
 The verification API for `finIdxOf?` is still incomplete.
@@ -730,28 +800,29 @@ theorem idxOf?_eq_map_finIdxOf?_val [BEq α] {xs : Array α} {a : α} :
     xs.idxOf? a = (xs.finIdxOf? a).map (·.val) := by
   simp [idxOf?, finIdxOf?, findIdx?_eq_map_findFinIdx?_val]
 
-@[simp] theorem finIdxOf?_empty [BEq α] : (#[] : Array α).finIdxOf? a = none := by simp
+@[grind =] theorem finIdxOf?_empty [BEq α] : (#[] : Array α).finIdxOf? a = none := by simp
 
-@[simp] theorem finIdxOf?_eq_none_iff [BEq α] [LawfulBEq α] {xs : Array α} {a : α} :
+@[simp, grind =] theorem finIdxOf?_eq_none_iff [BEq α] [LawfulBEq α] {xs : Array α} {a : α} :
     xs.finIdxOf? a = none ↔ a ∉ xs := by
   rcases xs with ⟨xs⟩
-  simp [List.finIdxOf?_eq_none_iff]
+  simp [List.finIdxOf?_eq_none_iff, Array.size]
 
 @[simp] theorem finIdxOf?_eq_some_iff [BEq α] [LawfulBEq α] {xs : Array α} {a : α} {i : Fin xs.size} :
     xs.finIdxOf? a = some i ↔ xs[i] = a ∧ ∀ j (_ : j < i), ¬xs[j] = a := by
   rcases xs with ⟨xs⟩
+  unfold Array.size at i ⊢
   simp [List.finIdxOf?_eq_some_iff]
 
-@[simp]
-theorem isSome_finIdxOf? [BEq α] [LawfulBEq α] {xs : Array α} {a : α} :
-    (xs.finIdxOf? a).isSome ↔ a ∈ xs := by
+@[simp, grind =]
+theorem isSome_finIdxOf? [BEq α] [PartialEquivBEq α] {xs : Array α} {a : α} :
+    (xs.finIdxOf? a).isSome = xs.contains a := by
   rcases xs with ⟨xs⟩
-  simp
+  simp [Array.size]
 
-@[simp]
-theorem isNone_finIdxOf? [BEq α] [LawfulBEq α] {xs : Array α} {a : α} :
-    (xs.finIdxOf? a).isNone = ¬ a ∈ xs := by
+@[simp, grind =]
+theorem isNone_finIdxOf? [BEq α] [PartialEquivBEq α] {xs : Array α} {a : α} :
+    (xs.finIdxOf? a).isNone = !xs.contains a := by
   rcases xs with ⟨xs⟩
-  simp
+  simp [Array.size]
 
 end Array

src/Init/Data/Array/InsertIdx.lean

@@ -44,13 +44,19 @@ theorem insertIdx_zero {xs : Array α} {x : α} : xs.insertIdx 0 x = #[x] ++ xs
 
 @[simp] theorem size_insertIdx {xs : Array α} (h : i ≤ xs.size) : (xs.insertIdx i a).size = xs.size + 1 := by
   rcases xs with ⟨xs⟩
+  simp at h
   simp [List.length_insertIdx, h]
 
-theorem eraseIdx_insertIdx {i : Nat} {xs : Array α} (h : i ≤ xs.size) :
+theorem eraseIdx_insertIdx_self {i : Nat} {xs : Array α} (h : i ≤ xs.size) :
     (xs.insertIdx i a).eraseIdx i (by simp; omega) = xs := by
   rcases xs with ⟨xs⟩
   simp_all
 
+@[deprecated eraseIdx_insertIdx_self (since := "2025-06-15")]
+theorem eraseIdx_insertIdx {i : Nat} {xs : Array α} (h : i ≤ xs.size) :
+    (xs.insertIdx i a).eraseIdx i (by simp; omega) = xs := by
+  simp [eraseIdx_insertIdx_self]
+
 theorem insertIdx_eraseIdx_of_ge {as : Array α}
     (w₁ : i < as.size) (w₂ : j ≤ (as.eraseIdx i).size) (h : i ≤ j) :
     (as.eraseIdx i).insertIdx j a =
@@ -65,6 +71,18 @@ theorem insertIdx_eraseIdx_of_le {as : Array α}
   cases as
   simpa using List.insertIdx_eraseIdx_of_le (by simpa) (by simpa)
 
+@[grind =]
+theorem insertIdx_eraseIdx {as : Array α} (h₁ : i < as.size) (h₂ : j ≤ (as.eraseIdx i).size) :
+    (as.eraseIdx i).insertIdx j a =
+      if h : i ≤ j then
+        (as.insertIdx (j + 1) a (by simp_all; omega)).eraseIdx i (by simp_all; omega)
+      else
+        (as.insertIdx j a).eraseIdx (i + 1) (by simp_all) := by
+  split <;> rename_i h'
+  · rw [insertIdx_eraseIdx_of_ge] <;> omega
+  · rw [insertIdx_eraseIdx_of_le] <;> omega
+
+@[grind =]
 theorem insertIdx_comm (a b : α) {i j : Nat} {xs : Array α} (_ : i ≤ j) (_ : j ≤ xs.size) :
     (xs.insertIdx i a).insertIdx (j + 1) b (by simpa) =
       (xs.insertIdx j b).insertIdx i a (by simp; omega) := by
@@ -80,6 +98,7 @@ theorem insertIdx_size_self {xs : Array α} {x : α} : xs.insertIdx xs.size x =
   rcases xs with ⟨xs⟩
   simp
 
+@[grind =]
 theorem getElem_insertIdx {xs : Array α} {x : α} {i k : Nat} (w : i ≤ xs.size) (h : k < (xs.insertIdx i x).size) :
     (xs.insertIdx i x)[k] =
       if h₁ : k < i then
@@ -105,6 +124,7 @@ theorem getElem_insertIdx_of_gt {xs : Array α} {x : α} {i k : Nat} (w : k ≤
   simp [getElem_insertIdx, w, h]
   rw [dif_neg (by omega), dif_neg (by omega)]
 
+@[grind =]
 theorem getElem?_insertIdx {xs : Array α} {x : α} {i k : Nat} (h : i ≤ xs.size) :
     (xs.insertIdx i x)[k]? =
       if k < i then

src/Init/Data/Array/Lemmas.lean

@@ -61,14 +61,9 @@ theorem toArray_eq : List.toArray as = xs ↔ as = xs.toList := by
 
 @[grind] theorem size_empty : (#[] : Array α).size = 0 := rfl
 
-@[simp] theorem emptyWithCapacity_eq {α n} : @emptyWithCapacity α n = #[] := rfl
-
-@[deprecated emptyWithCapacity_eq (since := "2025-03-12")]
-theorem mkEmpty_eq {α n} : @mkEmpty α n = #[] := rfl
-
 /-! ### size -/
 
-@[grind →] theorem eq_empty_of_size_eq_zero (h : xs.size = 0) : xs = #[] := by
+theorem eq_empty_of_size_eq_zero (h : xs.size = 0) : xs = #[] := by
   cases xs
   simp_all
 
@@ -80,8 +75,7 @@ theorem ne_empty_of_size_pos (h : 0 < xs.size) : xs ≠ #[] := by
   cases xs
   simpa using List.ne_nil_of_length_pos h
 
-@[grind]
-theorem size_eq_zero_iff : xs.size = 0 ↔ xs = #[] :=
+@[simp] theorem size_eq_zero_iff : xs.size = 0 ↔ xs = #[] :=
   ⟨eq_empty_of_size_eq_zero, fun h => h ▸ rfl⟩
 
 @[deprecated size_eq_zero_iff (since := "2025-02-24")]
@@ -95,6 +89,8 @@ theorem size_pos_of_mem {a : α} {xs : Array α} (h : a ∈ xs) : 0 < xs.size :=
   simp only [mem_toArray] at h
   simpa using List.length_pos_of_mem h
 
+grind_pattern size_pos_of_mem => a ∈ xs, xs.size
+
 theorem exists_mem_of_size_pos {xs : Array α} (h : 0 < xs.size) : ∃ a, a ∈ xs := by
   cases xs
   simpa using List.exists_mem_of_length_pos h
@@ -122,14 +118,11 @@ abbrev size_eq_one := @size_eq_one_iff
 
 /-! ## L[i] and L[i]? -/
 
-@[simp] theorem getElem?_eq_none_iff {xs : Array α} : xs[i]? = none ↔ xs.size ≤ i := by
-  by_cases h : i < xs.size
-  · simp [getElem?_pos, h]
-  · rw [getElem?_neg xs i h]
-    simp_all
+theorem getElem?_eq_none_iff {xs : Array α} : xs[i]? = none ↔ xs.size ≤ i := by
+  simp
 
-@[simp] theorem none_eq_getElem?_iff {xs : Array α} {i : Nat} : none = xs[i]? ↔ xs.size ≤ i := by
-  simp [eq_comm (a := none)]
+theorem none_eq_getElem?_iff {xs : Array α} {i : Nat} : none = xs[i]? ↔ xs.size ≤ i := by
+  simp
 
 theorem getElem?_eq_none {xs : Array α} (h : xs.size ≤ i) : xs[i]? = none := by
   simp [getElem?_eq_none_iff, h]
@@ -139,23 +132,22 @@ grind_pattern Array.getElem?_eq_none => xs.size ≤ i, xs[i]?
 @[simp] theorem getElem?_eq_getElem {xs : Array α} {i : Nat} (h : i < xs.size) : xs[i]? = some xs[i] :=
   getElem?_pos ..
 
-theorem getElem?_eq_some_iff {xs : Array α} : xs[i]? = some b ↔ ∃ h : i < xs.size, xs[i] = b := by
-  simp [getElem?_def]
+theorem getElem?_eq_some_iff {xs : Array α} : xs[i]? = some b ↔ ∃ h : i < xs.size, xs[i] = b :=
+  _root_.getElem?_eq_some_iff
 
-@[grind →]
 theorem getElem_of_getElem? {xs : Array α} : xs[i]? = some a → ∃ h : i < xs.size, xs[i] = a :=
   getElem?_eq_some_iff.mp
 
 theorem some_eq_getElem?_iff {xs : Array α} : some b = xs[i]? ↔ ∃ h : i < xs.size, xs[i] = b := by
   rw [eq_comm, getElem?_eq_some_iff]
 
-@[simp] theorem some_getElem_eq_getElem?_iff (xs : Array α) (i : Nat) (h : i < xs.size) :
+theorem some_getElem_eq_getElem?_iff (xs : Array α) (i : Nat) (h : i < xs.size) :
     (some xs[i] = xs[i]?) ↔ True := by
-  simp [h]
+  simp
 
-@[simp] theorem getElem?_eq_some_getElem_iff (xs : Array α) (i : Nat) (h : i < xs.size) :
+theorem getElem?_eq_some_getElem_iff (xs : Array α) (i : Nat) (h : i < xs.size) :
     (xs[i]? = some xs[i]) ↔ True := by
-  simp [h]
+  simp
 
 theorem getElem_eq_iff {xs : Array α} {i : Nat} {h : i < xs.size} : xs[i] = x ↔ xs[i]? = some x := by
   simp only [getElem?_eq_some_iff]
@@ -178,29 +170,29 @@ theorem getD_getElem? {xs : Array α} {i : Nat} {d : α} :
 theorem getElem_push_lt {xs : Array α} {x : α} {i : Nat} (h : i < xs.size) :
     have : i < (xs.push x).size := by simp [*, Nat.lt_succ_of_le, Nat.le_of_lt]
     (xs.push x)[i] = xs[i] := by
+  rw [Array.size] at h
   simp only [push, ← getElem_toList, List.concat_eq_append, List.getElem_append_left, h]
 
 @[simp] theorem getElem_push_eq {xs : Array α} {x : α} : (xs.push x)[xs.size] = x := by
   simp only [push, ← getElem_toList, List.concat_eq_append]
   rw [List.getElem_append_right] <;> simp [← getElem_toList, Nat.zero_lt_one]
 
-theorem getElem_push {xs : Array α} {x : α} {i : Nat} (h : i < (xs.push x).size) :
+@[grind =] theorem getElem_push {xs : Array α} {x : α} {i : Nat} (h : i < (xs.push x).size) :
     (xs.push x)[i] = if h : i < xs.size then xs[i] else x := by
   by_cases h' : i < xs.size
   · simp [getElem_push_lt, h']
   · simp at h
     simp [getElem_push_lt, Nat.le_antisymm (Nat.le_of_lt_succ h) (Nat.ge_of_not_lt h')]
 
-theorem getElem?_push {xs : Array α} {x} : (xs.push x)[i]? = if i = xs.size then some x else xs[i]? := by
+@[grind =] theorem getElem?_push {xs : Array α} {x} : (xs.push x)[i]? = if i = xs.size then some x else xs[i]? := by
   simp [getElem?_def, getElem_push]
   (repeat' split) <;> first | rfl | omega
 
-@[simp] theorem getElem?_push_size {xs : Array α} {x} : (xs.push x)[xs.size]? = some x := by
-  simp [getElem?_push]
+theorem getElem?_push_size {xs : Array α} {x} : (xs.push x)[xs.size]? = some x := by
+  simp
 
-@[simp] theorem getElem_singleton {a : α} {i : Nat} (h : i < 1) : #[a][i] = a :=
-  match i, h with
-  | 0, _ => rfl
+theorem getElem_singleton {a : α} {i : Nat} (h : i < 1) : #[a][i] = a := by
+  simp
 
 @[grind]
 theorem getElem?_singleton {a : α} {i : Nat} : #[a][i]? = if i = 0 then some a else none := by
@@ -247,6 +239,8 @@ theorem back?_pop {xs : Array α} :
 
 /-! ### push -/
 
+@[simp] theorem push_empty : #[].push x = #[x] := rfl
+
 @[simp] theorem push_ne_empty {a : α} {xs : Array α} : xs.push a ≠ #[] := by
   cases xs
   simp
@@ -426,8 +420,7 @@ theorem eq_empty_iff_forall_not_mem {xs : Array α} : xs = #[] ↔ ∀ a, a ∉
 theorem eq_of_mem_singleton (h : a ∈ #[b]) : a = b := by
   simpa using h
 
-@[simp] theorem mem_singleton {a b : α} : a ∈ #[b] ↔ a = b :=
-  ⟨eq_of_mem_singleton, (by simp [·])⟩
+theorem mem_singleton {a b : α} : a ∈ #[b] ↔ a = b := by simp
 
 theorem forall_mem_push {p : α → Prop} {xs : Array α} {a : α} :
     (∀ x, x ∈ xs.push a → p x) ↔ p a ∧ ∀ x, x ∈ xs → p x := by
@@ -612,13 +605,13 @@ theorem anyM_loop_cons [Monad m] {p : α → m Bool} {a : α} {as : List α} {st
 
 -- Auxiliary for `any_iff_exists`.
 theorem anyM_loop_iff_exists {p : α → Bool} {as : Array α} {start stop} (h : stop ≤ as.size) :
-    anyM.loop (m := Id) p as stop h start = true ↔
+    (anyM.loop (m := Id) (pure <| p ·) as stop h start).run = true ↔
       ∃ (i : Nat) (_ : i < as.size), start ≤ i ∧ i < stop ∧ p as[i] = true := by
   unfold anyM.loop
   split <;> rename_i h₁
   · dsimp
     split <;> rename_i h₂
-    · simp only [true_iff]
+    · simp only [true_iff, Id.run_pure]
       refine ⟨start, by omega, by omega, by omega, h₂⟩
     · rw [anyM_loop_iff_exists]
       constructor
@@ -635,9 +628,9 @@ termination_by stop - start
 -- This could also be proved from `SatisfiesM_anyM_iff_exists` in `Batteries.Data.Array.Init.Monadic`
 theorem any_iff_exists {p : α → Bool} {as : Array α} {start stop} :
     as.any p start stop ↔ ∃ (i : Nat) (_ : i < as.size), start ≤ i ∧ i < stop ∧ p as[i] := by
-  dsimp [any, anyM, Id.run]
+  dsimp [any, anyM]
   split
-  · rw [anyM_loop_iff_exists]
+  · rw [anyM_loop_iff_exists (p := p)]
   · rw [anyM_loop_iff_exists]
     constructor
     · rintro ⟨i, hi, ge, _, h⟩
@@ -771,6 +764,7 @@ theorem all_eq_false' {p : α → Bool} {as : Array α} :
   rw [Bool.eq_false_iff, Ne, all_eq_true']
   simp
 
+@[grind =]
 theorem any_eq {xs : Array α} {p : α → Bool} : xs.any p = decide (∃ i : Nat, ∃ h, p (xs[i]'h)) := by
   by_cases h : xs.any p
   · simp_all [any_eq_true]
@@ -785,6 +779,7 @@ theorem any_eq' {xs : Array α} {p : α → Bool} : xs.any p = decide (∃ x, x
     simp only [any_eq_false'] at h
     simpa using h
 
+@[grind =]
 theorem all_eq {xs : Array α} {p : α → Bool} : xs.all p = decide (∀ i, (_ : i < xs.size) → p xs[i]) := by
   by_cases h : xs.all p
   · simp_all [all_eq_true]
@@ -871,8 +866,8 @@ theorem elem_eq_mem [BEq α] [LawfulBEq α] {a : α} {xs : Array α} :
 @[simp, grind] theorem contains_eq_mem [BEq α] [LawfulBEq α] {a : α} {xs : Array α} :
     xs.contains a = decide (a ∈ xs) := by rw [← elem_eq_contains, elem_eq_mem]
 
-@[simp, grind] theorem any_empty [BEq α] {p : α → Bool} : (#[] : Array α).any p = false := by simp
-@[simp, grind] theorem all_empty [BEq α] {p : α → Bool} : (#[] : Array α).all p = true := by simp
+@[grind] theorem any_empty [BEq α] {p : α → Bool} : (#[] : Array α).any p = false := by simp
+@[grind] theorem all_empty [BEq α] {p : α → Bool} : (#[] : Array α).all p = true := by simp
 
 /-- Variant of `any_push` with a side condition on `stop`. -/
 @[simp, grind] theorem any_push' [BEq α] {xs : Array α} {a : α} {p : α → Bool} (h : stop = xs.size + 1) :
@@ -960,6 +955,13 @@ theorem set_push {xs : Array α} {x y : α} {h} :
         · simp at h
           omega
 
+@[grind _=_]
+theorem set_pop {xs : Array α} {x : α} {i : Nat} (h : i < xs.pop.size) :
+    xs.pop.set i x h = (xs.set i x (by simp at h; omega)).pop := by
+  ext i h₁ h₂
+  · simp
+  · simp [getElem_set]
+
 @[simp] theorem set_eq_empty_iff {xs : Array α} {i : Nat} {a : α} {h : i < xs.size} :
     xs.set i a = #[] ↔ xs = #[] := by
   cases xs <;> cases i <;> simp [set]
@@ -992,7 +994,11 @@ theorem mem_or_eq_of_mem_set
 @[simp, grind] theorem setIfInBounds_empty {i : Nat} {a : α} :
     #[].setIfInBounds i a = #[] := rfl
 
-@[simp] theorem set!_eq_setIfInBounds : @set! = @setIfInBounds := rfl
+@[simp, grind =] theorem set!_eq_setIfInBounds : set! xs i v = setIfInBounds xs i v := rfl
+
+@[grind]
+theorem setIfInBounds_def (xs : Array α) (i : Nat) (a : α) :
+    xs.setIfInBounds i a = if h : i < xs.size then xs.set i a else xs := rfl
 
 @[deprecated set!_eq_setIfInBounds (since := "2024-12-12")]
 abbrev set!_is_setIfInBounds := @set!_eq_setIfInBounds
@@ -1084,7 +1090,7 @@ theorem mem_or_eq_of_mem_setIfInBounds
   by_cases h : i < xs.size <;>
     simp [setIfInBounds, Nat.not_lt_of_le, h,  getD_getElem?]
 
-@[simp] theorem toList_setIfInBounds {xs : Array α} {i : Nat} {x : α} :
+@[simp, grind =] theorem toList_setIfInBounds {xs : Array α} {i : Nat} {x : α} :
     (xs.setIfInBounds i x).toList = xs.toList.set i x := by
   simp only [setIfInBounds]
   split <;> rename_i h
@@ -1231,7 +1237,7 @@ where
 @[simp] theorem mapM_empty [Monad m] (f : α → m β) : mapM f #[] = pure #[] := by
   rw [mapM, mapM.map]; rfl
 
-@[simp, grind] theorem map_empty {f : α → β} : map f #[] = #[] := mapM_empty f
+@[grind] theorem map_empty {f : α → β} : map f #[] = #[] := by simp
 
 @[simp, grind] theorem map_push {f : α → β} {as : Array α} {x : α} :
     (as.push x).map f = (as.map f).push (f x) := by
@@ -1266,7 +1272,8 @@ theorem map_singleton {f : α → β} {a : α} : map f #[a] = #[f a] := by simp
 
 -- We use a lower priority here as there are more specific lemmas in downstream libraries
 -- which should be able to fire first.
-@[simp 500] theorem mem_map {f : α → β} {xs : Array α} : b ∈ xs.map f ↔ ∃ a, a ∈ xs ∧ f a = b := by
+@[simp 500, grind =] theorem mem_map {f : α → β} {xs : Array α} :
+    b ∈ xs.map f ↔ ∃ a, a ∈ xs ∧ f a = b := by
   simp only [mem_def, toList_map, List.mem_map]
 
 theorem exists_of_mem_map (h : b ∈ map f l) : ∃ a, a ∈ l ∧ f a = b := mem_map.1 h
@@ -1369,17 +1376,17 @@ theorem mapM_eq_mapM_toList [Monad m] [LawfulMonad m] {f : α → m β} {xs : Ar
 
 @[deprecated "Use `mapM_eq_foldlM` instead" (since := "2025-01-08")]
 theorem mapM_map_eq_foldl {as : Array α} {f : α → β} {i : Nat} :
-    mapM.map (m := Id) f as i b = as.foldl (start := i) (fun acc a => acc.push (f a)) b := by
+    mapM.map (m := Id) (pure <| f ·) as i b = pure (as.foldl (start := i) (fun acc a => acc.push (f a)) b) := by
   unfold mapM.map
   split <;> rename_i h
-  · simp only [Id.bind_eq]
-    dsimp [foldl, Id.run, foldlM]
+  · ext : 1
+    dsimp [foldl, foldlM]
     rw [mapM_map_eq_foldl, dif_pos (by omega), foldlM.loop, dif_pos h]
     -- Calling `split` here gives a bad goal.
     have : size as - i = Nat.succ (size as - i - 1) := by omega
     rw [this]
-    simp [foldl, foldlM, Id.run, Nat.sub_add_eq]
-  · dsimp [foldl, Id.run, foldlM]
+    simp [foldl, foldlM, Nat.sub_add_eq]
+  · dsimp [foldl, foldlM]
     rw [dif_pos (by omega), foldlM.loop, dif_neg h]
     rfl
 termination_by as.size - i
@@ -1493,6 +1500,19 @@ theorem forall_mem_filter {p : α → Bool} {xs : Array α} {P : α → Prop} :
     (∀ (i) (_ : i ∈ xs.filter p), P i) ↔ ∀ (j) (_ : j ∈ xs), p j → P j := by
   simp
 
+@[grind] theorem getElem_filter {xs : Array α} {p : α → Bool} {i : Nat} (h : i < (xs.filter p).size) :
+    p (xs.filter p)[i] :=
+  (mem_filter.mp (getElem_mem h)).2
+
+theorem getElem?_filter {xs : Array α} {p : α → Bool} {i : Nat} (h : i < (xs.filter p).size)
+    (w : (xs.filter p)[i]? = some a) : p a := by
+  rw [getElem?_eq_getElem] at w
+  simp only [Option.some.injEq] at w
+  rw [← w]
+  apply getElem_filter h
+
+grind_pattern getElem?_filter => (xs.filter p)[i]?, some a
+
 @[simp] theorem filter_filter {p q : α → Bool} {xs : Array α} :
     filter p (filter q xs) = filter (fun a => p a && q a) xs := by
   apply ext'
@@ -1601,8 +1621,8 @@ theorem filterMap_congr {as bs : Array α} (h : as = bs)
     as.toList ++ List.filterMap f xs := ?_
   exact this #[]
   induction xs
-  · simp_all [Id.run]
-  · simp_all [Id.run, List.filterMap_cons]
+  · simp_all
+  · simp_all [List.filterMap_cons]
     split <;> simp_all
 
 @[grind] theorem toList_filterMap {f : α → Option β} {xs : Array α} :
@@ -1816,7 +1836,8 @@ theorem toArray_append {xs : List α} {ys : Array α} :
 
 theorem singleton_eq_toArray_singleton {a : α} : #[a] = [a].toArray := rfl
 
-@[simp] theorem empty_append_fun : ((#[] : Array α) ++ ·) = id := by
+@[deprecated empty_append (since := "2025-05-26")]
+theorem empty_append_fun : ((#[] : Array α) ++ ·) = id := by
   funext ⟨l⟩
   simp
 
@@ -1866,7 +1887,7 @@ theorem getElem_append_right {xs ys : Array α} {h : i < (xs ++ ys).size} (hle :
     (xs ++ ys)[i] = ys[i - xs.size]'(Nat.sub_lt_left_of_lt_add hle (size_append .. ▸ h)) := by
   simp only [← getElem_toList]
   have h' : i < (xs.toList ++ ys.toList).length := by rwa [← length_toList, toList_append] at h
-  conv => rhs; rw [← List.getElem_append_right (h₁ := hle) (h₂ := h')]
+  conv => rhs; unfold Array.size; rw [← List.getElem_append_right (h₁ := hle) (h₂ := h')]
   apply List.get_of_eq; rw [toList_append]
 
 theorem getElem?_append_left {xs ys : Array α} {i : Nat} (hn : i < xs.size) :
@@ -1967,8 +1988,8 @@ theorem append_left_inj {xs₁ xs₂ : Array α} (ys) : xs₁ ++ ys = xs₂ ++ y
 theorem eq_empty_of_append_eq_empty {xs ys : Array α} (h : xs ++ ys = #[]) : xs = #[] ∧ ys = #[] :=
   append_eq_empty_iff.mp h
 
-@[simp] theorem empty_eq_append_iff {xs ys : Array α} : #[] = xs ++ ys ↔ xs = #[] ∧ ys = #[] := by
-  rw [eq_comm, append_eq_empty_iff]
+theorem empty_eq_append_iff {xs ys : Array α} : #[] = xs ++ ys ↔ xs = #[] ∧ ys = #[] := by
+  simp
 
 theorem append_ne_empty_of_left_ne_empty {xs ys : Array α} (h : xs ≠ #[]) : xs ++ ys ≠ #[] := by
   simp_all
@@ -2033,10 +2054,10 @@ theorem append_eq_append_iff {ws xs ys zs : Array α} :
         xs ++ ys.set (i - xs.size) x (by simp at h; omega) := by
   rcases xs with ⟨s⟩
   rcases ys with ⟨t⟩
-  simp only [List.append_toArray, List.set_toArray, List.set_append]
+  simp only [List.append_toArray, List.set_toArray, List.set_append, Array.size]
   split <;> simp
 
-@[simp] theorem set_append_left {xs ys : Array α} {i : Nat} {x : α} (h : i < xs.size) :
+@[simp] theorem set_append_left {xs ys : Array α} {i : Nat} {x : α} (h : i < xs.size)  :
     (xs ++ ys).set i x (by simp; omega) = xs.set i x ++ ys := by
   simp [set_append, h]
 
@@ -2053,7 +2074,7 @@ theorem append_eq_append_iff {ws xs ys zs : Array α} :
         xs ++ ys.setIfInBounds (i - xs.size) x := by
   rcases xs with ⟨s⟩
   rcases ys with ⟨t⟩
-  simp only [List.append_toArray, List.setIfInBounds_toArray, List.set_append]
+  simp only [List.append_toArray, List.setIfInBounds_toArray, List.set_append, Array.size]
   split <;> simp
 
 @[simp] theorem setIfInBounds_append_left {xs ys : Array α} {i : Nat} {x : α} (h : i < xs.size) :
@@ -2111,14 +2132,13 @@ theorem append_eq_map_iff {f : α → β} :
   | nil => simp
   | cons as => induction as.toList <;> simp [*]
 
-@[simp] theorem flatten_map_toArray {L : List (List α)} :
-    (L.toArray.map List.toArray).flatten = L.flatten.toArray := by
+@[simp] theorem flatten_toArray_map {L : List (List α)} :
+    (L.map List.toArray).toArray.flatten = L.flatten.toArray := by
   apply ext'
   simp [Function.comp_def]
 
-@[simp] theorem flatten_toArray_map {L : List (List α)} :
-    (L.map List.toArray).toArray.flatten = L.flatten.toArray := by
-  rw [← flatten_map_toArray]
+theorem flatten_map_toArray {L : List (List α)} :
+    (L.toArray.map List.toArray).flatten = L.flatten.toArray := by
   simp
 
 -- We set this to lower priority so that `flatten_toArray_map` is applied first when relevant.
@@ -2146,8 +2166,8 @@ theorem mem_flatten : ∀ {xss : Array (Array α)}, a ∈ xss.flatten ↔ ∃ xs
   induction xss using array₂_induction
   simp
 
-@[simp] theorem empty_eq_flatten_iff {xss : Array (Array α)} : #[] = xss.flatten ↔ ∀ xs ∈ xss, xs = #[] := by
-  rw [eq_comm, flatten_eq_empty_iff]
+theorem empty_eq_flatten_iff {xss : Array (Array α)} : #[] = xss.flatten ↔ ∀ xs ∈ xss, xs = #[] := by
+  simp
 
 theorem flatten_ne_empty_iff {xss : Array (Array α)} : xss.flatten ≠ #[] ↔ ∃ xs, xs ∈ xss ∧ xs ≠ #[] := by
   simp
@@ -2287,15 +2307,9 @@ theorem eq_iff_flatten_eq {xss₁ xss₂ : Array (Array α)} :
       rw [List.map_inj_right]
       simp +contextual
 
-@[simp] theorem flatten_toArray_map_toArray {xss : List (List α)} :
+theorem flatten_toArray_map_toArray {xss : List (List α)} :
     (xss.map List.toArray).toArray.flatten = xss.flatten.toArray := by
-  simp [flatten]
-  suffices ∀ as, List.foldl (fun acc bs => acc ++ bs) as (List.map List.toArray xss) = as ++ xss.flatten.toArray by
-    simpa using this #[]
-  intro as
-  induction xss generalizing as with
-  | nil => simp
-  | cons xs xss ih => simp [ih]
+  simp
 
 /-! ### flatMap -/
 
@@ -2325,13 +2339,9 @@ theorem flatMap_toArray_cons {β} {f : α → Array β} {a : α} {as : List α}
   intro cs
   induction as generalizing cs <;> simp_all
 
-@[simp, grind =] theorem flatMap_toArray {β} {f : α → Array β} {as : List α} :
+theorem flatMap_toArray {β} {f : α → Array β} {as : List α} :
     as.toArray.flatMap f = (as.flatMap (fun a => (f a).toList)).toArray := by
-  induction as with
-  | nil => simp
-  | cons a as ih =>
-    apply ext'
-    simp [ih, flatMap_toArray_cons]
+  simp
 
 @[simp] theorem flatMap_id {xss : Array (Array α)} : xss.flatMap id = xss.flatten := by simp [flatMap_def]
 
@@ -2797,7 +2807,7 @@ theorem reverse_eq_iff {xs ys : Array α} : xs.reverse = ys ↔ xs = ys.reverse
   cases xs
   simp
 
-@[grind _=_]theorem filterMap_reverse {f : α → Option β} {xs : Array α} : (xs.reverse.filterMap f) = (xs.filterMap f).reverse := by
+@[grind _=_] theorem filterMap_reverse {f : α → Option β} {xs : Array α} : (xs.reverse.filterMap f) = (xs.filterMap f).reverse := by
   cases xs
   simp
 
@@ -3012,6 +3022,10 @@ theorem extract_empty_of_size_le_start {xs : Array α} {start stop : Nat} (h : x
   apply ext'
   simp
 
+theorem _root_.List.toArray_drop {l : List α} {k : Nat} :
+    (l.drop k).toArray = l.toArray.extract k := by
+  rw [List.drop_eq_extract, List.extract_toArray, List.size_toArray]
+
 @[deprecated extract_size (since := "2025-02-27")]
 theorem take_size {xs : Array α} : xs.take xs.size = xs := by
   cases xs
@@ -3033,19 +3047,21 @@ theorem take_size {xs : Array α} : xs.take xs.size = xs := by
   | succ n ih =>
     simp [shrink.loop, ih]
 
-@[simp] theorem size_shrink {xs : Array α} {i : Nat} : (xs.shrink i).size = min i xs.size := by
+-- This doesn't need to be a simp lemma, as shortly we will simplify `shrink` to `take`.
+theorem size_shrink {xs : Array α} {i : Nat} : (xs.shrink i).size = min i xs.size := by
   simp [shrink]
   omega
 
-@[simp] theorem getElem_shrink {xs : Array α} {i j : Nat} (h : j < (xs.shrink i).size) :
-    (xs.shrink i)[j] = xs[j]'(by simp at h; omega) := by
+-- This doesn't need to be a simp lemma, as shortly we will simplify `shrink` to `take`.
+theorem getElem_shrink {xs : Array α} {i j : Nat} (h : j < (xs.shrink i).size) :
+    (xs.shrink i)[j] = xs[j]'(by simp [size_shrink] at h; omega) := by
   simp [shrink]
 
-@[simp] theorem toList_shrink {xs : Array α} {i : Nat} : (xs.shrink i).toList = xs.toList.take i := by
-  apply List.ext_getElem <;> simp
-
 @[simp] theorem shrink_eq_take {xs : Array α} {i : Nat} : xs.shrink i = xs.take i := by
-  ext <;> simp
+  ext <;> simp [size_shrink, getElem_shrink]
+
+theorem toList_shrink {xs : Array α} {i : Nat} : (xs.shrink i).toList = xs.toList.take i := by
+  simp
 
 /-! ### foldlM and foldrM -/
 
@@ -3214,18 +3230,16 @@ theorem foldlM_push [Monad m] [LawfulMonad m] {xs : Array α} {a : α} {f : β
   rw [foldr, foldrM_start_stop, ← foldrM_toList, List.foldrM_pure, foldr_toList, foldr, ← foldrM_start_stop]
 
 theorem foldl_eq_foldlM {f : β → α → β} {b} {xs : Array α} {start stop : Nat} :
-    xs.foldl f b start stop = xs.foldlM (m := Id) f b start stop := by
-  simp [foldl, Id.run]
+    xs.foldl f b start stop = (xs.foldlM (m := Id) (pure <| f · ·) b start stop).run := rfl
 
 theorem foldr_eq_foldrM {f : α → β → β} {b} {xs : Array α} {start stop : Nat} :
-    xs.foldr f b start stop = xs.foldrM (m := Id) f b start stop := by
-  simp [foldr, Id.run]
+    xs.foldr f b start stop = (xs.foldrM (m := Id) (pure <| f · ·) b start stop).run := rfl
 
 @[simp] theorem id_run_foldlM {f : β → α → Id β} {b} {xs : Array α} {start stop : Nat} :
-    Id.run (xs.foldlM f b start stop) = xs.foldl f b start stop := foldl_eq_foldlM.symm
+    Id.run (xs.foldlM f b start stop) = xs.foldl (f · · |>.run) b start stop := rfl
 
 @[simp] theorem id_run_foldrM {f : α → β → Id β} {b} {xs : Array α} {start stop : Nat} :
-    Id.run (xs.foldrM f b start stop) = xs.foldr f b start stop := foldr_eq_foldrM.symm
+    Id.run (xs.foldrM f b start stop) = xs.foldr (f · · |>.run) b start stop := rfl
 
 /-- Variant of `foldlM_reverse` with a side condition for the `stop` argument. -/
 @[simp] theorem foldlM_reverse' [Monad m] {xs : Array α} {f : β → α → m β} {b} {stop : Nat}
@@ -3254,7 +3268,7 @@ theorem foldrM_reverse [Monad m] {xs : Array α} {f : α → β → m β} {b} :
 
 theorem foldrM_push [Monad m] {f : α → β → m β} {init : β} {xs : Array α} {a : α} :
     (xs.push a).foldrM f init = f a init >>= xs.foldrM f := by
-  simp only [foldrM_eq_reverse_foldlM_toList, push_toList, List.reverse_append, List.reverse_cons,
+  simp only [foldrM_eq_reverse_foldlM_toList, toList_push, List.reverse_append, List.reverse_cons,
     List.reverse_nil, List.nil_append, List.singleton_append, List.foldlM_cons, List.foldlM_reverse]
 
 /--
@@ -3266,6 +3280,22 @@ rather than `(arr.push a).size` as the argument.
     (xs.push a).foldrM f init start = f a init >>= xs.foldrM f := by
   simp [← foldrM_push, h]
 
+@[simp, grind] theorem _root_.List.foldrM_push_eq_append [Monad m] [LawfulMonad m] {l : List α} {f : α → m β} {xs : Array β} :
+    l.foldrM (fun x xs => xs.push <$> f x) xs = do return xs ++ (← l.reverse.mapM f).toArray := by
+  induction l with
+  | nil => simp
+  | cons a l ih =>
+    simp [ih]
+    congr 1
+    funext l'
+    congr 1
+    funext x
+    simp
+
+@[simp, grind] theorem _root_.List.foldlM_push_eq_append [Monad m] [LawfulMonad m] {l : List α} {f : α → m β} {xs : Array β} :
+    l.foldlM (fun xs x => xs.push <$> f x) xs = do return xs ++ (← l.mapM f).toArray := by
+  induction l generalizing xs <;> simp [*]
+
 /-! ### foldl / foldr -/
 
 @[grind] theorem foldl_empty {f : β → α → β} {init : β} : (#[].foldl f init) = init := rfl
@@ -3362,6 +3392,32 @@ rather than `(arr.push a).size` as the argument.
   rcases as with ⟨as⟩
   simp
 
+@[simp, grind] theorem _root_.List.foldr_push_eq_append {l : List α} {f : α → β} {xs : Array β} :
+    l.foldr (fun x xs => xs.push (f x)) xs = xs ++ (l.reverse.map f).toArray := by
+  induction l <;> simp [*]
+
+/-- Variant of `List.foldr_push_eq_append` specialized to `f = id`. -/
+@[simp, grind] theorem _root_.List.foldr_push_eq_append' {l : List α} {xs : Array α} :
+    l.foldr (fun x xs => xs.push x) xs = xs ++ l.reverse.toArray := by
+  induction l <;> simp [*]
+
+@[simp, grind] theorem _root_.List.foldl_push_eq_append {l : List α} {f : α → β} {xs : Array β} :
+    l.foldl (fun xs x => xs.push (f x)) xs = xs ++ (l.map f).toArray := by
+  induction l generalizing xs <;> simp [*]
+
+/-- Variant of `List.foldl_push_eq_append` specialized to `f = id`. -/
+@[simp, grind] theorem _root_.List.foldl_push_eq_append' {l : List α} {xs : Array α} :
+    l.foldl (fun xs x => xs.push x) xs = xs ++ l.toArray := by
+  simpa using List.foldl_push_eq_append (f := id)
+
+@[deprecated _root_.List.foldl_push_eq_append' (since := "2025-05-18")]
+theorem _root_.List.foldl_push {l : List α} {as : Array α} : l.foldl Array.push as = as ++ l.toArray := by
+  induction l generalizing as <;> simp [*]
+
+@[deprecated _root_.List.foldr_push_eq_append' (since := "2025-05-18")]
+theorem _root_.List.foldr_push {l : List α} {as : Array α} : l.foldr (fun a bs => push bs a) as = as ++ l.reverse.toArray := by
+  rw [List.foldr_eq_foldl_reverse, List.foldl_push_eq_append']
+
 @[simp, grind] theorem foldr_append_eq_append {xs : Array α} {f : α → Array β} {ys : Array β} :
     xs.foldr (f · ++ ·) ys = (xs.map f).flatten ++ ys := by
   rcases xs with ⟨xs⟩
@@ -3483,17 +3539,16 @@ theorem foldrM_append [Monad m] [LawfulMonad m] {f : α → β → m β} {b} {xs
 
 @[simp] theorem foldr_append' {f : α → β → β} {b} {xs ys : Array α} {start : Nat}
     (w : start = xs.size + ys.size) :
-    (xs ++ ys).foldr f b start 0 = xs.foldr f (ys.foldr f b) := by
-  subst w
-  simp [foldr_eq_foldrM]
+    (xs ++ ys).foldr f b start 0 = xs.foldr f (ys.foldr f b) :=
+  foldrM_append' w
 
-@[grind _=_]theorem foldl_append {β : Type _} {f : β → α → β} {b} {xs ys : Array α} :
-    (xs ++ ys).foldl f b = ys.foldl f (xs.foldl f b) := by
-  simp [foldl_eq_foldlM]
+@[grind _=_] theorem foldl_append {β : Type _} {f : β → α → β} {b} {xs ys : Array α} :
+    (xs ++ ys).foldl f b = ys.foldl f (xs.foldl f b) :=
+  foldlM_append
 
 @[grind _=_] theorem foldr_append {f : α → β → β} {b} {xs ys : Array α} :
-    (xs ++ ys).foldr f b = xs.foldr f (ys.foldr f b) := by
-  simp [foldr_eq_foldrM]
+    (xs ++ ys).foldr f b = xs.foldr f (ys.foldr f b) :=
+  foldrM_append
 
 @[simp] theorem foldl_flatten' {f : β → α → β} {b} {xss : Array (Array α)} {stop : Nat}
     (w : stop = xss.flatten.size) :
@@ -3522,21 +3577,22 @@ theorem foldrM_append [Monad m] [LawfulMonad m] {f : α → β → m β} {b} {xs
 /-- Variant of `foldl_reverse` with a side condition for the `stop` argument. -/
 @[simp] theorem foldl_reverse' {xs : Array α} {f : β → α → β} {b} {stop : Nat}
     (w : stop = xs.size) :
-    xs.reverse.foldl f b 0 stop = xs.foldr (fun x y => f y x) b := by
-  simp [w, foldl_eq_foldlM, foldr_eq_foldrM]
+    xs.reverse.foldl f b 0 stop = xs.foldr (fun x y => f y x) b :=
+  foldlM_reverse' w
 
 /-- Variant of `foldr_reverse` with a side condition for the `start` argument. -/
 @[simp] theorem foldr_reverse' {xs : Array α} {f : α → β → β} {b} {start : Nat}
     (w : start = xs.size) :
-    xs.reverse.foldr f b start 0 = xs.foldl (fun x y => f y x) b := by
-  simp [w, foldl_eq_foldlM, foldr_eq_foldrM]
+    xs.reverse.foldr f b start 0 = xs.foldl (fun x y => f y x) b :=
+  foldrM_reverse' w
 
 @[grind] theorem foldl_reverse {xs : Array α} {f : β → α → β} {b} :
-    xs.reverse.foldl f b = xs.foldr (fun x y => f y x) b := by simp [foldl_eq_foldlM, foldr_eq_foldrM]
+    xs.reverse.foldl f b = xs.foldr (fun x y => f y x) b :=
+  foldlM_reverse
 
 @[grind] theorem foldr_reverse {xs : Array α} {f : α → β → β} {b} :
     xs.reverse.foldr f b = xs.foldl (fun x y => f y x) b :=
-  (foldl_reverse ..).symm.trans <| by simp
+  foldrM_reverse
 
 theorem foldl_eq_foldr_reverse {xs : Array α} {f : β → α → β} {b} :
     xs.foldl f b = xs.reverse.foldr (fun x y => f y x) b := by simp
@@ -3580,8 +3636,8 @@ We can prove that two folds over the same array are related (by some arbitrary r
 if we know that the initial elements are related and the folding function, for each element of the array,
 preserves the relation.
 -/
-theorem foldl_rel {xs : Array α} {f g : β → α → β} {a b : β} {r : β → β → Prop}
-    (h : r a b) (h' : ∀ (a : α), a ∈ xs → ∀ (c c' : β), r c c' → r (f c a) (g c' a)) :
+theorem foldl_rel {xs : Array α} {f : β → α → β} {g : γ → α → γ} {a : β} {b : γ} {r : β → γ → Prop}
+    (h : r a b) (h' : ∀ (a : α), a ∈ xs → ∀ (c : β) (c' : γ), r c c' → r (f c a) (g c' a)) :
     r (xs.foldl (fun acc a => f acc a) a) (xs.foldl (fun acc a => g acc a) b) := by
   rcases xs with ⟨xs⟩
   simpa using List.foldl_rel h (by simpa using h')
@@ -3591,8 +3647,8 @@ We can prove that two folds over the same array are related (by some arbitrary r
 if we know that the initial elements are related and the folding function, for each element of the array,
 preserves the relation.
 -/
-theorem foldr_rel {xs : Array α} {f g : α → β → β} {a b : β} {r : β → β → Prop}
-    (h : r a b) (h' : ∀ (a : α), a ∈ xs → ∀ (c c' : β), r c c' → r (f a c) (g a c')) :
+theorem foldr_rel {xs : Array α} {f : α → β → β} {g : α → γ → γ} {a : β} {b : γ} {r : β → γ → Prop}
+    (h : r a b) (h' : ∀ (a : α), a ∈ xs → ∀ (c : β) (c' : γ), r c c' → r (f a c) (g a c')) :
     r (xs.foldr (fun a acc => f a acc) a) (xs.foldr (fun a acc => g a acc) b) := by
   rcases xs with ⟨xs⟩
   simpa using List.foldr_rel h (by simpa using h')
@@ -3617,7 +3673,7 @@ theorem foldr_rel {xs : Array α} {f g : α → β → β} {a b : β} {r : β
 theorem back?_eq_some_iff {xs : Array α} {a : α} :
     xs.back? = some a ↔ ∃ ys : Array α, xs = ys.push a := by
   rcases xs with ⟨xs⟩
-  simp only [List.back?_toArray, List.getLast?_eq_some_iff, toArray_eq, push_toList]
+  simp only [List.back?_toArray, List.getLast?_eq_some_iff, toArray_eq, toList_push]
   constructor
   · rintro ⟨ys, rfl⟩
     exact ⟨ys.toArray, by simp⟩
@@ -3707,7 +3763,7 @@ theorem back?_replicate {a : α} {n : Nat} :
 @[deprecated back?_replicate (since := "2025-03-18")]
 abbrev back?_mkArray := @back?_replicate
 
-@[simp] theorem back_replicate (w : 0 < n) : (replicate n a).back (by simpa using w) = a := by
+@[simp] theorem back_replicate {xs : Array α} (w : 0 < n) : (replicate n xs).back (by simpa using w) = xs := by
   simp [back_eq_getElem]
 
 @[deprecated back_replicate (since := "2025-03-18")]
@@ -3742,7 +3798,7 @@ theorem contains_iff_exists_mem_beq [BEq α] {xs : Array α} {a : α} :
   rcases xs with ⟨xs⟩
   simp [List.contains_iff_exists_mem_beq]
 
-@[grind]
+@[grind _=_]
 theorem contains_iff_mem [BEq α] [LawfulBEq α] {xs : Array α} {a : α} :
     xs.contains a ↔ a ∈ xs := by
   simp
@@ -4050,18 +4106,19 @@ abbrev all_mkArray := @all_replicate
 
 /-! ### modify -/
 
-@[simp] theorem size_modify {xs : Array α} {i : Nat} {f : α → α} : (xs.modify i f).size = xs.size := by
-  unfold modify modifyM Id.run
+@[simp, grind =] theorem size_modify {xs : Array α} {i : Nat} {f : α → α} : (xs.modify i f).size = xs.size := by
+  unfold modify modifyM
   split <;> simp
 
-theorem getElem_modify {xs : Array α} {j i} (h : i < (xs.modify j f).size) :
+@[grind =] theorem getElem_modify {xs : Array α} {j i} (h : i < (xs.modify j f).size) :
     (xs.modify j f)[i] = if j = i then f (xs[i]'(by simpa using h)) else xs[i]'(by simpa using h) := by
-  simp only [modify, modifyM, Id.run, Id.pure_eq]
+  simp only [modify, modifyM]
   split
-  · simp only [Id.bind_eq, getElem_set]; split <;> simp [*]
-  · rw [if_neg (mt (by rintro rfl; exact h) (by simp_all))]
+  · simp only [getElem_set, Id.run_pure, Id.run_bind]; split <;> simp [*]
+  · simp only [Id.run_pure]
+    rw [if_neg (mt (by rintro rfl; exact h) (by simp_all))]
 
-@[simp] theorem toList_modify {xs : Array α} {f : α → α} {i : Nat} :
+@[simp, grind =] theorem toList_modify {xs : Array α} {f : α → α} {i : Nat} :
     (xs.modify i f).toList = xs.toList.modify i f := by
   apply List.ext_getElem
   · simp
@@ -4076,7 +4133,7 @@ theorem getElem_modify_of_ne {xs : Array α} {i : Nat} (h : i ≠ j)
     (xs.modify i f)[j] = xs[j]'(by simpa using hj) := by
   simp [getElem_modify hj, h]
 
-theorem getElem?_modify {xs : Array α} {i : Nat} {f : α → α} {j : Nat} :
+@[grind =] theorem getElem?_modify {xs : Array α} {i : Nat} {f : α → α} {j : Nat} :
     (xs.modify i f)[j]? = if i = j then xs[j]?.map f else xs[j]? := by
   simp only [getElem?_def, size_modify, getElem_modify, Option.map_dif]
   split <;> split <;> rfl
@@ -4125,20 +4182,18 @@ theorem swap_comm {xs : Array α} {i j : Nat} (hi hj) : xs.swap i j hi hj = xs.s
     · split <;> simp_all
     · split <;> simp_all
 
-@[simp] theorem size_swapIfInBounds {xs : Array α} {i j : Nat} :
+@[simp, grind =] theorem size_swapIfInBounds {xs : Array α} {i j : Nat} :
     (xs.swapIfInBounds i j).size = xs.size := by unfold swapIfInBounds; split <;> (try split) <;> simp [size_swap]
 
-@[deprecated size_swapIfInBounds (since := "2024-11-24")] abbrev size_swap! := @size_swapIfInBounds
-
 /-! ### swapAt -/
 
-@[simp] theorem swapAt_def {xs : Array α} {i : Nat} {v : α} (hi) :
+@[simp, grind =] theorem swapAt_def {xs : Array α} {i : Nat} {v : α} (hi) :
     xs.swapAt i v hi = (xs[i], xs.set i v) := rfl
 
 theorem size_swapAt {xs : Array α} {i : Nat} {v : α} (hi) :
     (xs.swapAt i v hi).2.size = xs.size := by simp
 
-@[simp]
+@[simp, grind =]
 theorem swapAt!_def {xs : Array α} {i : Nat} {v : α} (h : i < xs.size) :
     xs.swapAt! i v = (xs[i], xs.set i v) := by simp [swapAt!, h]
 
@@ -4261,42 +4316,44 @@ Examples:
 
 /-! ### Preliminaries about `ofFn` -/
 
-@[simp] theorem size_ofFn_go {n} {f : Fin n → α} {i acc} :
-    (ofFn.go f i acc).size = acc.size + (n - i) := by
-  if hin : i < n then
-    unfold ofFn.go
-    have : 1 + (n - (i + 1)) = n - i :=
-      Nat.sub_sub .. ▸ Nat.add_sub_cancel' (Nat.le_sub_of_add_le (Nat.add_comm .. ▸ hin))
-    rw [dif_pos hin, size_ofFn_go, size_push, Nat.add_assoc, this]
-  else
-    have : n - i = 0 := Nat.sub_eq_zero_of_le (Nat.le_of_not_lt hin)
-    unfold ofFn.go
-    simp [hin, this]
-termination_by n - i
+@[simp] theorem size_ofFn_go {n} {f : Fin n → α} {i acc h} :
+    (ofFn.go f acc i h).size = acc.size + i := by
+  induction i generalizing acc with
+  | zero => simp [ofFn.go]
+  | succ i ih =>
+    simpa [ofFn.go, ih] using Nat.succ_add_eq_add_succ acc.size i
 
 @[simp] theorem size_ofFn {n : Nat} {f : Fin n → α} : (ofFn f).size = n := by simp [ofFn]
 
-theorem getElem_ofFn_go {f : Fin n → α} {i} {acc k}
-    (hki : k < n) (hin : i ≤ n) (hi : i = acc.size)
-    (hacc : ∀ j, ∀ hj : j < acc.size, acc[j] = f ⟨j, Nat.lt_of_lt_of_le hj (hi ▸ hin)⟩) :
-    haveI : acc.size + (n - acc.size) = n := Nat.add_sub_cancel' (hi ▸ hin)
-    (ofFn.go f i acc)[k]'(by simp [*]) = f ⟨k, hki⟩ := by
-  unfold ofFn.go
-  if hin : i < n then
-    have : 1 + (n - (i + 1)) = n - i :=
-      Nat.sub_sub .. ▸ Nat.add_sub_cancel' (Nat.le_sub_of_add_le (Nat.add_comm .. ▸ hin))
-    simp only [dif_pos hin]
-    rw [getElem_ofFn_go _ hin (by simp [*]) (fun j hj => ?hacc)]
-    cases (Nat.lt_or_eq_of_le <| Nat.le_of_lt_succ (by simpa using hj)) with
-    | inl hj => simp [getElem_push, hj, hacc j hj]
-    | inr hj => simp [getElem_push, *]
-  else
-    simp [hin, hacc k (Nat.lt_of_lt_of_le hki (Nat.le_of_not_lt (hi ▸ hin)))]
-termination_by n - i
+-- Recall `ofFn.go f acc i h = acc ++ #[f (n - i), ..., f(n - 1)]`
+theorem getElem_ofFn_go {f : Fin n → α} {acc i k} (h : i ≤ n) (w₁ : k < acc.size + i) :
+    (ofFn.go f acc i h)[k]'(by simpa using w₁) =
+      if w₂ : k < acc.size then acc[k] else f ⟨n - i + k - acc.size, by omega⟩ := by
+  induction i generalizing acc k with
+  | zero =>
+    simp at w₁
+    simp_all [ofFn.go]
+  | succ i ih =>
+    unfold ofFn.go
+    rw [ih]
+    · simp only [size_push]
+      split <;> rename_i h'
+      · rw [Array.getElem_push]
+        split
+        · rfl
+        · congr 2
+          omega
+      · split
+        · omega
+        · congr 2
+          omega
+    · simp
+      omega
 
 @[simp] theorem getElem_ofFn {f : Fin n → α} {i : Nat} (h : i < (ofFn f).size) :
-    (ofFn f)[i] = f ⟨i, size_ofFn (f := f) ▸ h⟩ :=
-  getElem_ofFn_go _ (by simp) (by simp) nofun
+    (ofFn f)[i] = f ⟨i, size_ofFn (f := f) ▸ h⟩ := by
+  unfold ofFn
+  rw [getElem_ofFn_go] <;> simp_all
 
 theorem getElem?_ofFn {f : Fin n → α} {i : Nat} :
     (ofFn f)[i]? = if h : i < n then some (f ⟨i, h⟩) else none := by
@@ -4304,42 +4361,44 @@ theorem getElem?_ofFn {f : Fin n → α} {i : Nat} :
 
 /-! ### Preliminaries about `range` and `range'` -/
 
-@[simp] theorem size_range' {start size step} : (range' start size step).size = size := by
+@[simp, grind =] theorem size_range' {start size step} : (range' start size step).size = size := by
   simp [range']
 
-@[simp] theorem toList_range' {start size step} :
+@[simp, grind =] theorem toList_range' {start size step} :
      (range' start size step).toList = List.range' start size step := by
   apply List.ext_getElem <;> simp [range']
 
-@[simp]
+@[simp, grind =]
 theorem getElem_range' {start size step : Nat} {i : Nat}
     (h : i < (Array.range' start size step).size) :
     (Array.range' start size step)[i] = start + step * i := by
   simp [← getElem_toList]
 
+@[grind =]
 theorem getElem?_range' {start size step : Nat} {i : Nat} :
     (Array.range' start size step)[i]? = if i < size then some (start + step * i) else none := by
   simp [getElem?_def, getElem_range']
 
-@[simp] theorem _root_.List.toArray_range' {start size step : Nat} :
+@[simp, grind =] theorem _root_.List.toArray_range' {start size step : Nat} :
     (List.range' start size step).toArray = Array.range' start size step := by
   apply ext'
   simp
 
-@[simp] theorem size_range {n : Nat} : (range n).size = n := by
+@[simp, grind =] theorem size_range {n : Nat} : (range n).size = n := by
   simp [range]
 
-@[simp] theorem toList_range {n : Nat} : (range n).toList = List.range n := by
+@[simp, grind =] theorem toList_range {n : Nat} : (range n).toList = List.range n := by
   apply List.ext_getElem <;> simp [range]
 
-@[simp]
+@[simp, grind =]
 theorem getElem_range {n : Nat} {i : Nat} (h : i < (Array.range n).size) : (Array.range n)[i] = i := by
   simp [← getElem_toList]
 
+@[grind =]
 theorem getElem?_range {n : Nat} {i : Nat} : (Array.range n)[i]? = if i < n then some i else none := by
   simp [getElem?_def, getElem_range]
 
-@[simp] theorem _root_.List.toArray_range {n : Nat} : (List.range n).toArray = Array.range n := by
+@[simp, grind =] theorem _root_.List.toArray_range {n : Nat} : (List.range n).toArray = Array.range n := by
   apply ext'
   simp
 
@@ -4387,7 +4446,8 @@ theorem getElem!_eq_getD [Inhabited α] {xs : Array α} {i} : xs[i]! = xs.getD i
 
 /-! # mem -/
 
-@[simp, grind =] theorem mem_toList {a : α} {xs : Array α} : a ∈ xs.toList ↔ a ∈ xs := mem_def.symm
+@[deprecated mem_toList_iff (since := "2025-05-26")]
+theorem mem_toList {a : α} {xs : Array α} : a ∈ xs.toList ↔ a ∈ xs := mem_def.symm
 
 @[deprecated not_mem_empty (since := "2025-03-25")]
 theorem not_mem_nil (a : α) : ¬ a ∈ #[] := nofun
@@ -4407,7 +4467,7 @@ theorem getElem?_size_le {xs : Array α} {i : Nat} (h : xs.size ≤ i) : xs[i]?
   simp [getElem?_neg, h]
 
 theorem getElem_mem_toList {xs : Array α} {i : Nat} (h : i < xs.size) : xs[i] ∈ xs.toList := by
-  simp only [← getElem_toList, List.getElem_mem]
+  simp only [← getElem_toList, List.getElem_mem, ugetElem_eq_getElem]
 
 theorem back!_eq_back? [Inhabited α] {xs : Array α} : xs.back! = xs.back?.getD default := by
   simp [back!, back?, getElem!_def, Option.getD]; rfl
@@ -4436,7 +4496,7 @@ theorem getElem?_push_eq {xs : Array α} {x : α} : (xs.push x)[xs.size]? = some
   simp
 
 @[simp, grind =] theorem forIn'_toList [Monad m] {xs : Array α} {b : β} {f : (a : α) → a ∈ xs.toList → β → m (ForInStep β)} :
-    forIn' xs.toList b f = forIn' xs b (fun a m b => f a (mem_toList.mpr m) b) := by
+    forIn' xs.toList b f = forIn' xs b (fun a m b => f a (mem_toList_iff.mpr m) b) := by
   cases xs
   simp
 
@@ -4475,12 +4535,13 @@ abbrev contains_def [DecidableEq α] {a : α} {xs : Array α} : xs.contains a
 @[simp] theorem size_zipWith {xs : Array α} {ys : Array β} {f : α → β → γ} :
     (zipWith f xs ys).size = min xs.size ys.size := by
   rw [size_eq_length_toList, toList_zipWith, List.length_zipWith]
+  simp only [Array.size]
 
 @[simp] theorem size_zip {xs : Array α} {ys : Array β} :
     (zip xs ys).size = min xs.size ys.size :=
   size_zipWith
 
-@[simp] theorem getElem_zipWith {xs : Array α} {ys : Array β} {f : α → β → γ} {i : Nat}
+@[simp, grind =] theorem getElem_zipWith {xs : Array α} {ys : Array β} {f : α → β → γ} {i : Nat}
     (hi : i < (zipWith f xs ys).size) :
     (zipWith f xs ys)[i] = f (xs[i]'(by simp at hi; omega)) (ys[i]'(by simp at hi; omega)) := by
   cases xs
@@ -4533,8 +4594,8 @@ Our goal is to have `simp` "pull `List.toArray` outwards" as much as possible.
 
 theorem toListRev_toArray {l : List α} : l.toArray.toListRev = l.reverse := by simp
 
-@[simp, grind =] theorem take_toArray {l : List α} {i : Nat} : l.toArray.take i = (l.take i).toArray := by
-  apply Array.ext <;> simp
+@[grind =] theorem take_toArray {l : List α} {i : Nat} : l.toArray.take i = (l.take i).toArray := by
+  simp
 
 @[simp, grind =] theorem mapM_toArray [Monad m] [LawfulMonad m] {f : α → m β} {l : List α} :
     l.toArray.mapM f = List.toArray <$> l.mapM f := by
@@ -4547,7 +4608,7 @@ theorem toListRev_toArray {l : List α} : l.toArray.toListRev = l.reverse := by
   | nil => simp
   | cons a l ih =>
     simp only [foldlM_toArray] at ih
-    rw [size_toArray, mapM'_cons, foldlM_toArray]
+    rw [size_toArray, mapM'_cons]
     simp [ih]
 
 theorem uset_toArray {l : List α} {i : USize} {a : α} {h : i.toNat < l.toArray.size} :
@@ -4600,12 +4661,12 @@ namespace Array
 @[simp] theorem findSomeRev?_eq_findSome?_reverse {f : α → Option β} {xs : Array α} :
     xs.findSomeRev? f = xs.reverse.findSome? f := by
   cases xs
-  simp [findSomeRev?, Id.run]
+  simp [findSomeRev?]
 
 @[simp] theorem findRev?_eq_find?_reverse {f : α → Bool} {xs : Array α} :
     xs.findRev? f = xs.reverse.find? f := by
   cases xs
-  simp [findRev?, Id.run]
+  simp [findRev?]
 
 /-! ### unzip -/
 
@@ -4661,13 +4722,6 @@ namespace List
 end List
 
 /-! ### Deprecations -/
-
-namespace List
-
-@[deprecated setIfInBounds_toArray (since := "2024-11-24")] abbrev setD_toArray := @setIfInBounds_toArray
-
-end List
-
 namespace Array
 
 @[deprecated size_toArray (since := "2024-12-11")]
@@ -4720,17 +4774,6 @@ theorem get_set_eq (xs : Array α) (i : Nat) (v : α) (h : i < xs.size) :
     (xs.set i v h)[i]'(by simp [h]) = v := by
   simp only [set, ← getElem_toList, List.getElem_set_self]
 
-@[deprecated set!_is_setIfInBounds (since := "2024-11-24")] abbrev set_is_setIfInBounds := @set!_eq_setIfInBounds
-@[deprecated size_setIfInBounds (since := "2024-11-24")] abbrev size_setD := @size_setIfInBounds
-@[deprecated getElem_setIfInBounds_eq (since := "2024-11-24")] abbrev getElem_setD_eq := @getElem_setIfInBounds_self
-@[deprecated getElem?_setIfInBounds_eq (since := "2024-11-24")] abbrev get?_setD_eq := @getElem?_setIfInBounds_self
-@[deprecated getD_getElem?_setIfInBounds (since := "2025-04-04")] abbrev getD_get?_setIfInBounds := @getD_getElem?_setIfInBounds
-@[deprecated getD_getElem?_setIfInBounds (since := "2024-11-24")] abbrev getD_setD := @getD_getElem?_setIfInBounds
-@[deprecated getElem_setIfInBounds (since := "2024-11-24")] abbrev getElem_setD := @getElem_setIfInBounds
-
-@[deprecated List.getElem_toArray (since := "2024-11-29")]
-theorem getElem_mk {xs : List α} {i : Nat} (h : i < xs.length) : (Array.mk xs)[i] = xs[i] := rfl
-
 @[deprecated Array.getElem_toList (since := "2024-12-08")]
 theorem getElem_eq_getElem_toList {xs : Array α} (h : i < xs.size) : xs[i] = xs.toList[i] := rfl
 

src/Init/Data/Array/Lex/Lemmas.lean

@@ -29,16 +29,12 @@ protected theorem not_le_iff_gt [DecidableEq α] [LT α] [DecidableLT α] {xs ys
   Decidable.not_not
 
 @[simp] theorem lex_empty [BEq α] {lt : α → α → Bool} {xs : Array α} : xs.lex #[] lt = false := by
-  simp [lex, Id.run]
-
-@[simp] theorem singleton_lex_singleton [BEq α] {lt : α → α → Bool} : #[a].lex #[b] lt = lt a b := by
-  simp only [lex, List.getElem_toArray, List.getElem_singleton]
-  cases lt a b <;> cases a != b <;> simp [Id.run]
+  simp [lex]
 
 private theorem cons_lex_cons [BEq α] {lt : α → α → Bool} {a b : α} {xs ys : Array α} :
      (#[a] ++ xs).lex (#[b] ++ ys) lt =
        (lt a b || a == b && xs.lex ys lt) := by
-  simp only [lex, Id.run]
+  simp only [lex]
   simp only [Std.Range.forIn'_eq_forIn'_range', size_append, List.size_toArray, List.length_singleton,
     Nat.add_comm 1]
   simp [Nat.add_min_add_right, List.range'_succ, getElem_append_left, List.range'_succ_left,
@@ -51,13 +47,16 @@ private theorem cons_lex_cons [BEq α] {lt : α → α → Bool} {a b : α} {xs
 @[simp, grind =] theorem _root_.List.lex_toArray [BEq α] {lt : α → α → Bool} {l₁ l₂ : List α} :
     l₁.toArray.lex l₂.toArray lt = l₁.lex l₂ lt := by
   induction l₁ generalizing l₂ with
-  | nil => cases l₂ <;> simp [lex, Id.run]
+  | nil => cases l₂ <;> simp [lex]
   | cons x l₁ ih =>
     cases l₂ with
-    | nil => simp [lex, Id.run]
+    | nil => simp [lex]
     | cons y l₂ =>
       rw [List.toArray_cons, List.toArray_cons y, cons_lex_cons, List.lex, ih]
 
+theorem singleton_lex_singleton [BEq α] {lt : α → α → Bool} : #[a].lex #[b] lt = lt a b := by
+  simp
+
 @[simp, grind =] theorem lex_toList [BEq α] {lt : α → α → Bool} {xs ys : Array α} :
     xs.toList.lex ys.toList lt = xs.lex ys lt := by
   cases xs <;> cases ys <;> simp

src/Init/Data/Array/MapIdx.lean

@@ -27,7 +27,7 @@ theorem mapFinIdx_induction (xs : Array α) (f : (i : Nat) → α → (h : i < x
     motive xs.size ∧ ∃ eq : (Array.mapFinIdx xs f).size = xs.size,
       ∀ i h, p i ((Array.mapFinIdx xs f)[i]) h := by
   let rec go {bs i j h} (h₁ : j = bs.size) (h₂ : ∀ i h h', p i bs[i] h) (hm : motive j) :
-    let as : Array β := Array.mapFinIdxM.map (m := Id) xs f i j h bs
+    let as : Array β := Id.run <| Array.mapFinIdxM.map xs (pure <| f · · ·) i j h bs
     motive xs.size ∧ ∃ eq : as.size = xs.size, ∀ i h, p i as[i] h := by
     induction i generalizing j bs with simp [mapFinIdxM.map]
     | zero =>
@@ -51,27 +51,27 @@ theorem mapFinIdx_spec {xs : Array α} {f : (i : Nat) → α → (h : i < xs.siz
       ∀ i h, p i ((Array.mapFinIdx xs f)[i]) h :=
   (mapFinIdx_induction _ _ (fun _ => True) trivial p fun _ _ _ => ⟨hs .., trivial⟩).2
 
-@[simp] theorem size_mapFinIdx {xs : Array α} {f : (i : Nat) → α → (h : i < xs.size) → β} :
+@[simp, grind =] theorem size_mapFinIdx {xs : Array α} {f : (i : Nat) → α → (h : i < xs.size) → β} :
     (xs.mapFinIdx f).size = xs.size :=
   (mapFinIdx_spec (p := fun _ _ _ => True) (hs := fun _ _ => trivial)).1
 
-@[simp] theorem size_zipIdx {xs : Array α} {k : Nat} : (xs.zipIdx k).size = xs.size :=
+@[simp, grind =] theorem size_zipIdx {xs : Array α} {k : Nat} : (xs.zipIdx k).size = xs.size :=
   Array.size_mapFinIdx
 
 @[deprecated size_zipIdx (since := "2025-01-21")] abbrev size_zipWithIndex := @size_zipIdx
 
-@[simp] theorem getElem_mapFinIdx {xs : Array α} {f : (i : Nat) → α → (h : i < xs.size) → β} {i : Nat}
+@[simp, grind =] theorem getElem_mapFinIdx {xs : Array α} {f : (i : Nat) → α → (h : i < xs.size) → β} {i : Nat}
     (h : i < (xs.mapFinIdx f).size) :
     (xs.mapFinIdx f)[i] = f i (xs[i]'(by simp_all)) (by simp_all) :=
   (mapFinIdx_spec (p := fun i b h => b = f i xs[i] h) fun _ _ => rfl).2 i _
 
-@[simp] theorem getElem?_mapFinIdx {xs : Array α} {f : (i : Nat) → α → (h : i < xs.size) → β} {i : Nat} :
+@[simp, grind =] theorem getElem?_mapFinIdx {xs : Array α} {f : (i : Nat) → α → (h : i < xs.size) → β} {i : Nat} :
     (xs.mapFinIdx f)[i]? =
       xs[i]?.pbind fun b h => some <| f i b (getElem?_eq_some_iff.1 h).1 := by
   simp only [getElem?_def, size_mapFinIdx, getElem_mapFinIdx]
   split <;> simp_all
 
-@[simp] theorem toList_mapFinIdx {xs : Array α} {f : (i : Nat) → α → (h : i < xs.size) → β} :
+@[simp, grind =] theorem toList_mapFinIdx {xs : Array α} {f : (i : Nat) → α → (h : i < xs.size) → β} :
     (xs.mapFinIdx f).toList = xs.toList.mapFinIdx (fun i a h => f i a (by simpa)) := by
   apply List.ext_getElem <;> simp
 
@@ -91,20 +91,20 @@ theorem mapIdx_spec {f : Nat → α → β} {xs : Array α}
       ∀ i h, p i ((xs.mapIdx f)[i]) h :=
   (mapIdx_induction (motive := fun _ => True) trivial fun _ _ _ => ⟨hs .., trivial⟩).2
 
-@[simp] theorem size_mapIdx {f : Nat → α → β} {xs : Array α} : (xs.mapIdx f).size = xs.size :=
+@[simp, grind =] theorem size_mapIdx {f : Nat → α → β} {xs : Array α} : (xs.mapIdx f).size = xs.size :=
   (mapIdx_spec (p := fun _ _ _ => True) (hs := fun _ _ => trivial)).1
 
-@[simp] theorem getElem_mapIdx {f : Nat → α → β} {xs : Array α} {i : Nat}
+@[simp, grind =] theorem getElem_mapIdx {f : Nat → α → β} {xs : Array α} {i : Nat}
     (h : i < (xs.mapIdx f).size) :
     (xs.mapIdx f)[i] = f i (xs[i]'(by simp_all)) :=
   (mapIdx_spec (p := fun i b h => b = f i xs[i]) fun _ _ => rfl).2 i (by simp_all)
 
-@[simp] theorem getElem?_mapIdx {f : Nat → α → β} {xs : Array α} {i : Nat} :
+@[simp, grind =] theorem getElem?_mapIdx {f : Nat → α → β} {xs : Array α} {i : Nat} :
     (xs.mapIdx f)[i]? =
       xs[i]?.map (f i) := by
   simp [getElem?_def, size_mapIdx, getElem_mapIdx]
 
-@[simp] theorem toList_mapIdx {f : Nat → α → β} {xs : Array α} :
+@[simp, grind =] theorem toList_mapIdx {f : Nat → α → β} {xs : Array α} :
     (xs.mapIdx f).toList = xs.toList.mapIdx (fun i a => f i a) := by
   apply List.ext_getElem <;> simp
 
@@ -126,7 +126,7 @@ namespace Array
 
 /-! ### zipIdx -/
 
-@[simp] theorem getElem_zipIdx {xs : Array α} {k : Nat} {i : Nat} (h : i < (xs.zipIdx k).size) :
+@[simp, grind =] theorem getElem_zipIdx {xs : Array α} {k : Nat} {i : Nat} (h : i < (xs.zipIdx k).size) :
     (xs.zipIdx k)[i] = (xs[i]'(by simp_all), k + i) := by
   simp [zipIdx]
 
@@ -140,7 +140,7 @@ abbrev getElem_zipWithIndex := @getElem_zipIdx
 @[deprecated zipIdx_toArray (since := "2025-01-21")]
 abbrev zipWithIndex_toArray := @zipIdx_toArray
 
-@[simp] theorem toList_zipIdx {xs : Array α} {k : Nat} :
+@[simp, grind =] theorem toList_zipIdx {xs : Array α} {k : Nat} :
     (xs.zipIdx k).toList = xs.toList.zipIdx k := by
   rcases xs with ⟨xs⟩
   simp
@@ -185,24 +185,26 @@ abbrev mem_zipWithIndex_iff_getElem? := @mem_zipIdx_iff_getElem?
   subst w
   rfl
 
-@[simp]
+@[simp, grind =]
 theorem mapFinIdx_empty {f : (i : Nat) → α → (h : i < 0) → β} : mapFinIdx #[] f = #[] :=
   rfl
 
 theorem mapFinIdx_eq_ofFn {xs : Array α} {f : (i : Nat) → α → (h : i < xs.size) → β} :
     xs.mapFinIdx f = Array.ofFn fun i : Fin xs.size => f i xs[i] i.2 := by
   cases xs
-  simp [List.mapFinIdx_eq_ofFn]
+  simp only [List.mapFinIdx_toArray, List.mapFinIdx_eq_ofFn, Fin.getElem_fin, List.getElem_toArray]
+  simp [Array.size]
 
+@[grind =]
 theorem mapFinIdx_append {xs ys : Array α} {f : (i : Nat) → α → (h : i < (xs ++ ys).size) → β} :
     (xs ++ ys).mapFinIdx f =
       xs.mapFinIdx (fun i a h => f i a (by simp; omega)) ++
         ys.mapFinIdx (fun i a h => f (i + xs.size) a (by simp; omega)) := by
   cases xs
   cases ys
-  simp [List.mapFinIdx_append]
+  simp [List.mapFinIdx_append, Array.size]
 
-@[simp]
+@[simp, grind =]
 theorem mapFinIdx_push {xs : Array α} {a : α} {f : (i : Nat) → α → (h : i < (xs.push a).size) → β} :
     mapFinIdx (xs.push a) f =
       (mapFinIdx xs (fun i a h => f i a (by simp; omega))).push (f xs.size a (by simp)) := by
@@ -236,7 +238,7 @@ theorem exists_of_mem_mapFinIdx {b : β} {xs : Array α} {f : (i : Nat) → α
   rcases xs with ⟨xs⟩
   exact List.exists_of_mem_mapFinIdx (by simpa using h)
 
-@[simp] theorem mem_mapFinIdx {b : β} {xs : Array α} {f : (i : Nat) → α → (h : i < xs.size) → β} :
+@[simp, grind =] theorem mem_mapFinIdx {b : β} {xs : Array α} {f : (i : Nat) → α → (h : i < xs.size) → β} :
     b ∈ xs.mapFinIdx f ↔ ∃ (i : Nat) (h : i < xs.size), f i xs[i] h = b := by
   rcases xs with ⟨xs⟩
   simp
@@ -264,12 +266,12 @@ theorem mapFinIdx_eq_append_iff {xs : Array α} {f : (i : Nat) → α → (h : i
     toArray_eq_append_iff]
   constructor
   · rintro ⟨l₁, l₂, rfl, rfl, rfl⟩
-    refine ⟨l₁.toArray, l₂.toArray, by simp_all⟩
+    refine ⟨l₁.toArray, l₂.toArray, by simp_all [Array.size]⟩
   · rintro ⟨⟨l₁⟩, ⟨l₂⟩, rfl, h₁, h₂⟩
     simp [← toList_inj] at h₁ h₂
     obtain rfl := h₁
     obtain rfl := h₂
-    refine ⟨l₁, l₂, by simp_all⟩
+    refine ⟨l₁, l₂, by simp_all [Array.size]⟩
 
 theorem mapFinIdx_eq_push_iff {xs : Array α} {b : β} {f : (i : Nat) → α → (h : i < xs.size) → β} :
     xs.mapFinIdx f = ys.push b ↔
@@ -289,7 +291,7 @@ theorem mapFinIdx_eq_mapFinIdx_iff {xs : Array α} {f g : (i : Nat) → α → (
   rw [eq_comm, mapFinIdx_eq_iff]
   simp
 
-@[simp] theorem mapFinIdx_mapFinIdx {xs : Array α}
+@[simp, grind =] theorem mapFinIdx_mapFinIdx {xs : Array α}
     {f : (i : Nat) → α → (h : i < xs.size) → β}
     {g : (i : Nat) → β → (h : i < (xs.mapFinIdx f).size) → γ} :
     (xs.mapFinIdx f).mapFinIdx g = xs.mapFinIdx (fun i a h => g i (f i a h) (by simpa using h)) := by
@@ -304,14 +306,14 @@ theorem mapFinIdx_eq_replicate_iff {xs : Array α} {f : (i : Nat) → α → (h
 @[deprecated mapFinIdx_eq_replicate_iff (since := "2025-03-18")]
 abbrev mapFinIdx_eq_mkArray_iff := @mapFinIdx_eq_replicate_iff
 
-@[simp] theorem mapFinIdx_reverse {xs : Array α} {f : (i : Nat) → α → (h : i < xs.reverse.size) → β} :
+@[simp, grind =] theorem mapFinIdx_reverse {xs : Array α} {f : (i : Nat) → α → (h : i < xs.reverse.size) → β} :
     xs.reverse.mapFinIdx f = (xs.mapFinIdx (fun i a h => f (xs.size - 1 - i) a (by simp; omega))).reverse := by
   rcases xs with ⟨l⟩
-  simp [List.mapFinIdx_reverse]
+  simp [List.mapFinIdx_reverse, Array.size]
 
 /-! ### mapIdx -/
 
-@[simp]
+@[simp, grind =]
 theorem mapIdx_empty {f : Nat → α → β} : mapIdx f #[] = #[] :=
   rfl
 
@@ -331,13 +333,14 @@ theorem mapIdx_eq_zipIdx_map {xs : Array α} {f : Nat → α → β} :
 @[deprecated mapIdx_eq_zipIdx_map (since := "2025-01-21")]
 abbrev mapIdx_eq_zipWithIndex_map := @mapIdx_eq_zipIdx_map
 
+@[grind =]
 theorem mapIdx_append {xs ys : Array α} :
     (xs ++ ys).mapIdx f = xs.mapIdx f ++ ys.mapIdx (fun i => f (i + xs.size)) := by
   rcases xs with ⟨xs⟩
   rcases ys with ⟨ys⟩
   simp [List.mapIdx_append]
 
-@[simp]
+@[simp, grind =]
 theorem mapIdx_push {xs : Array α} {a : α} :
     mapIdx f (xs.push a) = (mapIdx f xs).push (f xs.size a) := by
   simp [← append_singleton, mapIdx_append]
@@ -359,7 +362,7 @@ theorem exists_of_mem_mapIdx {b : β} {xs : Array α}
   rw [mapIdx_eq_mapFinIdx] at h
   simpa [Fin.exists_iff] using exists_of_mem_mapFinIdx h
 
-@[simp] theorem mem_mapIdx {b : β} {xs : Array α} :
+@[simp, grind =] theorem mem_mapIdx {b : β} {xs : Array α} :
     b ∈ mapIdx f xs ↔ ∃ (i : Nat) (h : i < xs.size), f i xs[i] = b := by
   constructor
   · intro h
@@ -413,7 +416,7 @@ theorem mapIdx_eq_mapIdx_iff {xs : Array α} :
   rcases xs with ⟨xs⟩
   simp [List.mapIdx_eq_mapIdx_iff]
 
-@[simp] theorem mapIdx_set {xs : Array α} {i : Nat} {h : i < xs.size} {a : α} :
+@[simp, grind =] theorem mapIdx_set {f : Nat → α → β} {xs : Array α} {i : Nat} {h : i < xs.size} {a : α} :
     (xs.set i a).mapIdx f = (xs.mapIdx f).set i (f i a) (by simpa) := by
   rcases xs with ⟨xs⟩
   simp [List.mapIdx_set]
@@ -423,17 +426,17 @@ theorem mapIdx_eq_mapIdx_iff {xs : Array α} :
   rcases xs with ⟨xs⟩
   simp [List.mapIdx_set]
 
-@[simp] theorem back?_mapIdx {xs : Array α} {f : Nat → α → β} :
+@[simp, grind =] theorem back?_mapIdx {xs : Array α} {f : Nat → α → β} :
     (mapIdx f xs).back? = (xs.back?).map (f (xs.size - 1)) := by
   rcases xs with ⟨xs⟩
   simp [List.getLast?_mapIdx]
 
-@[simp] theorem back_mapIdx {xs : Array α} {f : Nat → α → β} (h) :
+@[simp, grind =] theorem back_mapIdx {xs : Array α} {f : Nat → α → β} (h) :
     (xs.mapIdx f).back h = f (xs.size - 1) (xs.back (by simpa using h)) := by
   rcases xs with ⟨xs⟩
   simp [List.getLast_mapIdx]
 
-@[simp] theorem mapIdx_mapIdx {xs : Array α} {f : Nat → α → β} {g : Nat → β → γ} :
+@[simp, grind =] theorem mapIdx_mapIdx {xs : Array α} {f : Nat → α → β} {g : Nat → β → γ} :
     (xs.mapIdx f).mapIdx g = xs.mapIdx (fun i => g i ∘ f i) := by
   simp [mapIdx_eq_iff]
 
@@ -446,7 +449,7 @@ theorem mapIdx_eq_replicate_iff {xs : Array α} {f : Nat → α → β} {b : β}
 @[deprecated mapIdx_eq_replicate_iff (since := "2025-03-18")]
 abbrev mapIdx_eq_mkArray_iff := @mapIdx_eq_replicate_iff
 
-@[simp] theorem mapIdx_reverse {xs : Array α} {f : Nat → α → β} :
+@[simp, grind =] theorem mapIdx_reverse {xs : Array α} {f : Nat → α → β} :
     xs.reverse.mapIdx f = (mapIdx (fun i => f (xs.size - 1 - i)) xs).reverse := by
   rcases xs with ⟨xs⟩
   simp [List.mapIdx_reverse]
@@ -455,7 +458,7 @@ end Array
 
 namespace List
 
-@[grind] theorem mapFinIdxM_toArray [Monad m] [LawfulMonad m] {l : List α}
+@[grind =] theorem mapFinIdxM_toArray [Monad m] [LawfulMonad m] {l : List α}
     {f : (i : Nat) → α → (h : i < l.length) → m β} :
     l.toArray.mapFinIdxM f = toArray <$> l.mapFinIdxM f := by
   let rec go (i : Nat) (acc : Array β) (inv : i + acc.size = l.length) :
@@ -476,7 +479,7 @@ namespace List
   simp only [Array.mapFinIdxM, mapFinIdxM]
   exact go _ #[] _
 
-@[grind] theorem mapIdxM_toArray [Monad m] [LawfulMonad m] {l : List α}
+@[grind =] theorem mapIdxM_toArray [Monad m] [LawfulMonad m] {l : List α}
     {f : Nat → α → m β} :
     l.toArray.mapIdxM f = toArray <$> l.mapIdxM f := by
   let rec go (bs : List α) (acc : Array β) (inv : bs.length + acc.size = l.length) :
@@ -486,7 +489,7 @@ namespace List
     | x :: xs => simp only [mapFinIdxM.go, mapIdxM.go, go]
   unfold Array.mapIdxM
   rw [mapFinIdxM_toArray]
-  simp only [mapFinIdxM, mapIdxM]
+  simp only [mapFinIdxM, mapIdxM, Array.size]
   rw [go]
 
 end List

src/Init/Data/Array/Monadic.lean

@@ -25,15 +25,29 @@ open Nat
 
 /-! ## Monadic operations -/
 
+theorem map_toList_inj [Monad m] [LawfulMonad m]
+    {xs : m (Array α)} {ys : m (Array α)} :
+   toList <$> xs = toList <$> ys ↔ xs = ys := by
+  simp
+
 /-! ### mapM -/
 
 @[simp] theorem mapM_pure [Monad m] [LawfulMonad m] {xs : Array α} {f : α → β} :
     xs.mapM (m := m) (pure <| f ·) = pure (xs.map f) := by
   induction xs; simp_all
 
-@[simp] theorem mapM_id {xs : Array α} {f : α → Id β} : xs.mapM f = xs.map f :=
+@[simp] theorem idRun_mapM {xs : Array α} {f : α → Id β} : (xs.mapM f).run = xs.map (f · |>.run) :=
   mapM_pure
 
+@[deprecated idRun_mapM (since := "2025-05-21")]
+theorem mapM_id {xs : Array α} {f : α → Id β} : xs.mapM f = xs.map f :=
+  mapM_pure
+
+@[simp] theorem mapM_map [Monad m] [LawfulMonad m] {f : α → β} {g : β → m γ} {xs : Array α} :
+    (xs.map f).mapM g = xs.mapM (g ∘ f) := by
+  rcases xs with ⟨xs⟩
+  simp
+
 @[simp] theorem mapM_append [Monad m] [LawfulMonad m] {f : α → m β} {xs ys : Array α} :
     (xs ++ ys).mapM f = (return (← xs.mapM f) ++ (← ys.mapM f)) := by
   rcases xs with ⟨xs⟩
@@ -181,12 +195,18 @@ theorem forIn'_eq_foldlM [Monad m] [LawfulMonad m]
   rcases xs with ⟨xs⟩
   simp [List.forIn'_pure_yield_eq_foldl, List.foldl_map]
 
-@[simp] theorem forIn'_yield_eq_foldl
+theorem idRun_forIn'_yield_eq_foldl
+    {xs : Array α} (f : (a : α) → a ∈ xs → β → Id β) (init : β) :
+    (forIn' xs init (fun a m b => .yield <$> f a m b)).run =
+      xs.attach.foldl (fun b ⟨a, h⟩ => f a h b |>.run) init := by
+  simp
+
+@[deprecated idRun_forIn'_yield_eq_foldl (since := "2025-05-21")]
+theorem forIn'_yield_eq_foldl
     {xs : Array α} (f : (a : α) → a ∈ xs → β → β) (init : β) :
     forIn' (m := Id) xs init (fun a m b => .yield (f a m b)) =
-      xs.attach.foldl (fun b ⟨a, h⟩ => f a h b) init := by
-  rcases xs with ⟨xs⟩
-  simp [List.foldl_map]
+      xs.attach.foldl (fun b ⟨a, h⟩ => f a h b) init :=
+  forIn'_pure_yield_eq_foldl _ _
 
 @[simp] theorem forIn'_map [Monad m] [LawfulMonad m]
     {xs : Array α} (g : α → β) (f : (b : β) → b ∈ xs.map g → γ → m (ForInStep γ)) :
@@ -223,12 +243,18 @@ theorem forIn_eq_foldlM [Monad m] [LawfulMonad m]
   rcases xs with ⟨xs⟩
   simp [List.forIn_pure_yield_eq_foldl, List.foldl_map]
 
-@[simp] theorem forIn_yield_eq_foldl
+theorem idRun_forIn_yield_eq_foldl
+    {xs : Array α} (f : α → β → Id β) (init : β) :
+    (forIn xs init (fun a b => .yield <$> f a b)).run =
+      xs.foldl (fun b a => f a b |>.run) init := by
+  simp
+
+@[deprecated idRun_forIn_yield_eq_foldl (since := "2025-05-21")]
+theorem forIn_yield_eq_foldl
     {xs : Array α} (f : α → β → β) (init : β) :
     forIn (m := Id) xs init (fun a b => .yield (f a b)) =
-      xs.foldl (fun b a => f a b) init := by
-  rcases xs with ⟨xs⟩
-  simp [List.foldl_map]
+      xs.foldl (fun b a => f a b) init :=
+  forIn_pure_yield_eq_foldl _ _
 
 @[simp] theorem forIn_map [Monad m] [LawfulMonad m]
     {xs : Array α} {g : α → β} {f : β → γ → m (ForInStep γ)} :
@@ -284,7 +310,7 @@ namespace List
 @[simp] theorem filterM_toArray' [Monad m] [LawfulMonad m] {l : List α} {p : α → m Bool} (w : stop = l.length) :
     l.toArray.filterM p 0 stop = toArray <$> l.filterM p := by
   subst w
-  rw [filterM_toArray]
+  simp [← filterM_toArray]
 
 @[grind =] theorem filterRevM_toArray [Monad m] [LawfulMonad m] {l : List α} {p : α → m Bool} :
     l.toArray.filterRevM p = toArray <$> l.filterRevM p := by
@@ -296,7 +322,7 @@ namespace List
 @[simp] theorem filterRevM_toArray' [Monad m] [LawfulMonad m] {l : List α} {p : α → m Bool} (w : start = l.length) :
     l.toArray.filterRevM p start 0 = toArray <$> l.filterRevM p := by
   subst w
-  rw [filterRevM_toArray]
+  simp [← filterRevM_toArray]
 
 @[grind =] theorem filterMapM_toArray [Monad m] [LawfulMonad m] {l : List α} {f : α → m (Option β)} :
     l.toArray.filterMapM f = toArray <$> l.filterMapM f := by
@@ -314,7 +340,7 @@ namespace List
 @[simp] theorem filterMapM_toArray' [Monad m] [LawfulMonad m] {l : List α} {f : α → m (Option β)} (w : stop = l.length) :
     l.toArray.filterMapM f 0 stop = toArray <$> l.filterMapM f := by
   subst w
-  rw [filterMapM_toArray]
+  simp [← filterMapM_toArray]
 
 @[simp, grind =] theorem flatMapM_toArray [Monad m] [LawfulMonad m] {l : List α} {f : α → m (Array β)} :
     l.toArray.flatMapM f = toArray <$> l.flatMapM (fun a => Array.toList <$> f a) := by

src/Init/Data/Array/OfFn.lean

@@ -8,7 +8,9 @@ module
 prelude
 import all Init.Data.Array.Basic
 import Init.Data.Array.Lemmas
+import Init.Data.Array.Monadic
 import Init.Data.List.OfFn
+import Init.Data.List.FinRange
 
 /-!
 # Theorems about `Array.ofFn`
@@ -19,7 +21,9 @@ set_option linter.indexVariables true -- Enforce naming conventions for index va
 
 namespace Array
 
-@[simp] theorem ofFn_zero {f : Fin 0 → α} : ofFn f = #[] := by
+/-! ### ofFn -/
+
+@[simp, grind =] theorem ofFn_zero {f : Fin 0 → α} : ofFn f = #[] := by
   simp [ofFn, ofFn.go]
 
 theorem ofFn_succ {f : Fin (n+1) → α} :
@@ -32,18 +36,29 @@ theorem ofFn_succ {f : Fin (n+1) → α} :
     intro h₃
     simp only [show i = n by omega]
 
-@[simp] theorem _root_.List.toArray_ofFn {f : Fin n → α} : (List.ofFn f).toArray = Array.ofFn f := by
+theorem ofFn_add {n m} {f : Fin (n + m) → α} :
+    ofFn f = (ofFn (fun i => f (i.castLE (Nat.le_add_right n m)))) ++ (ofFn (fun i => f (i.natAdd n))) := by
+  induction m with
+  | zero => simp
+  | succ m ih => simp [ofFn_succ, ih]
+
+@[simp, grind =] theorem _root_.List.toArray_ofFn {f : Fin n → α} : (List.ofFn f).toArray = Array.ofFn f := by
   ext <;> simp
 
-@[simp] theorem toList_ofFn {f : Fin n → α} : (Array.ofFn f).toList = List.ofFn f := by
+@[simp, grind =] theorem toList_ofFn {f : Fin n → α} : (Array.ofFn f).toList = List.ofFn f := by
   apply List.ext_getElem <;> simp
 
+theorem ofFn_succ' {f : Fin (n+1) → α} :
+    ofFn f = #[f 0] ++ ofFn (fun i => f i.succ) := by
+  apply Array.toList_inj.mp
+  simp [List.ofFn_succ]
+
 @[simp]
 theorem ofFn_eq_empty_iff {f : Fin n → α} : ofFn f = #[] ↔ n = 0 := by
   rw [← Array.toList_inj]
   simp
 
-@[simp 500]
+@[simp 500, grind =]
 theorem mem_ofFn {n} {f : Fin n → α} {a : α} : a ∈ ofFn f ↔ ∃ i, f i = a := by
   constructor
   · intro w
@@ -52,4 +67,70 @@ theorem mem_ofFn {n} {f : Fin n → α} {a : α} : a ∈ ofFn f ↔ ∃ i, f i =
   · rintro ⟨i, rfl⟩
     apply mem_of_getElem (i := i) <;> simp
 
+/-! ### ofFnM -/
+
+/-- Construct (in a monadic context) an array by applying a monadic function to each index. -/
+def ofFnM {n} [Monad m] (f : Fin n → m α) : m (Array α) :=
+  Fin.foldlM n (fun xs i => xs.push <$> f i) (Array.emptyWithCapacity n)
+
+@[simp, grind =]
+theorem ofFnM_zero [Monad m] {f : Fin 0 → m α} : ofFnM f = pure #[] := by
+  simp [ofFnM]
+
+theorem ofFnM_succ' {n} [Monad m] [LawfulMonad m] {f : Fin (n + 1) → m α} :
+    ofFnM f = (do
+      let a ← f 0
+      let as ← ofFnM fun i => f i.succ
+      pure (#[a] ++ as)) := by
+  simp [ofFnM, Fin.foldlM_eq_foldlM_finRange, List.foldlM_push_eq_append, List.finRange_succ, Function.comp_def]
+
+theorem ofFnM_succ {n} [Monad m] [LawfulMonad m] {f : Fin (n + 1) → m α} :
+    ofFnM f = (do
+      let as ← ofFnM fun i => f i.castSucc
+      let a  ← f (Fin.last n)
+      pure (as.push a)) := by
+  simp [ofFnM, Fin.foldlM_succ_last]
+
+theorem ofFnM_add {n m} [Monad m] [LawfulMonad m] {f : Fin (n + k) → m α} :
+    ofFnM f = (do
+      let as ← ofFnM fun i : Fin n => f (i.castLE (Nat.le_add_right n k))
+      let bs ← ofFnM fun i : Fin k => f (i.natAdd n)
+      pure (as ++ bs)) := by
+  induction k with
+  | zero => simp
+  | succ k ih =>
+    simp only [ofFnM_succ, Nat.add_eq, ih, Fin.castSucc_castLE, Fin.castSucc_natAdd, bind_pure_comp,
+      bind_assoc, bind_map_left, Fin.natAdd_last, map_bind, Functor.map_map]
+    congr 1
+    funext xs
+    congr 1
+    funext ys
+    congr 1
+    funext x
+    simp
+
+@[simp, grind =] theorem toList_ofFnM [Monad m] [LawfulMonad m] {f : Fin n → m α} :
+    toList <$> ofFnM f = List.ofFnM f := by
+  induction n with
+  | zero => simp
+  | succ n ih => simp [ofFnM_succ, List.ofFnM_succ_last, ← ih]
+
+@[simp]
+theorem ofFnM_pure_comp [Monad m] [LawfulMonad m] {n} {f : Fin n → α} :
+    ofFnM (pure ∘ f) = (pure (ofFn f) : m (Array α)) := by
+  apply Array.map_toList_inj.mp
+  simp
+
+-- Variant of `ofFnM_pure_comp` using a lambda.
+-- This is not marked a `@[simp]` as it would match on every occurrence of `ofFnM`.
+theorem ofFnM_pure [Monad m] [LawfulMonad m] {n} {f : Fin n → α} :
+    ofFnM (fun i => pure (f i)) = (pure (ofFn f) : m (Array α)) :=
+  ofFnM_pure_comp
+
+@[simp, grind =] theorem idRun_ofFnM {f : Fin n → Id α} :
+    Id.run (ofFnM f) = ofFn (fun i => Id.run (f i)) := by
+  induction n with
+  | zero => simp
+  | succ n ih => simp [ofFnM_succ', ofFn_succ', ih]
+
 end Array

src/Init/Data/Array/Perm.lean

@@ -91,17 +91,26 @@ theorem Perm.mem_iff {a : α} {xs ys : Array α} (p : xs ~ ys) : a ∈ xs ↔ a
   simp only [perm_iff_toList_perm] at p
   simpa using p.mem_iff
 
+grind_pattern Perm.mem_iff => xs ~ ys, a ∈ xs
+grind_pattern Perm.mem_iff => xs ~ ys, a ∈ ys
+
 theorem Perm.append {xs ys as bs : Array α} (p₁ : xs ~ ys) (p₂ : as ~ bs) :
     xs ++ as ~ ys ++ bs := by
   cases xs; cases ys; cases as; cases bs
   simp only [append_toArray, perm_iff_toList_perm] at p₁ p₂ ⊢
   exact p₁.append p₂
 
+grind_pattern Perm.append => xs ~ ys, as ~ bs, xs ++ as
+grind_pattern Perm.append => xs ~ ys, as ~ bs, ys ++ bs
+
 theorem Perm.push (x : α) {xs ys : Array α} (p : xs ~ ys) :
     xs.push x ~ ys.push x := by
   rw [push_eq_append_singleton]
   exact p.append .rfl
 
+grind_pattern Perm.push => xs ~ ys, xs.push x
+grind_pattern Perm.push => xs ~ ys, ys.push x
+
 theorem Perm.push_comm (x y : α) {xs ys : Array α} (p : xs ~ ys) :
     (xs.push x).push y ~ (ys.push y).push x := by
   cases xs; cases ys

src/Init/Data/Array/QSort/Basic.lean

@@ -27,23 +27,27 @@ Internal implementation of `Array.qsort`.
 
 It does so by first swapping the elements at indices `lo`, `mid := (lo + hi) / 2`, and `hi`
 if necessary so that the middle (pivot) element is at index `hi`.
-We then iterate from `j = lo` to `j = hi`, with a pointer `i` starting at `lo`, and
+We then iterate from `k = lo` to `k = hi`, with a pointer `i` starting at `lo`, and
 swapping each element which is less than the pivot to position `i`, and then incrementing `i`.
 -/
-def qpartition {n} (as : Vector α n) (lt : α → α → Bool) (lo hi : Nat)
-    (hlo : lo < n := by omega) (hhi : hi < n := by omega) : {m : Nat // lo ≤ m ∧ m < n} × Vector α n :=
+def qpartition {n} (as : Vector α n) (lt : α → α → Bool) (lo hi : Nat) (w : lo ≤ hi := by omega)
+    (hlo : lo < n := by omega) (hhi : hi < n := by omega) : {m : Nat // lo ≤ m ∧ m ≤ hi} × Vector α n :=
   let mid := (lo + hi) / 2
   let as  := if lt as[mid] as[lo] then as.swap lo mid else as
   let as  := if lt as[hi]  as[lo] then as.swap lo hi  else as
   let as  := if lt as[mid] as[hi] then as.swap mid hi else as
   let pivot := as[hi]
-  let rec loop (as : Vector α n) (i j : Nat)
-      (ilo : lo ≤ i := by omega) (jh : j < n := by omega) (w : i ≤ j := by omega) :=
-    if h : j < hi then
-      if lt as[j] pivot then
-        loop (as.swap i j) (i+1) (j+1)
+  -- During this loop, elements below in `[lo, i)` are less than `pivot`,
+  -- elements in `[i, k)` are greater than or equal to `pivot`,
+  -- elements in `[k, hi)` are unexamined,
+  -- while `as[hi]` is (by definition) the pivot.
+  let rec loop (as : Vector α n) (i k : Nat)
+      (ilo : lo ≤ i := by omega) (ik : i ≤ k := by omega) (w : k ≤ hi := by omega) :=
+    if h : k < hi then
+      if lt as[k] pivot then
+        loop (as.swap i k) (i+1) (k+1)
       else
-        loop as i (j+1)
+        loop as i (k+1)
     else
       (⟨i, ilo, by omega⟩, as.swap i hi)
   loop as lo lo
@@ -51,25 +55,28 @@ def qpartition {n} (as : Vector α n) (lt : α → α → Bool) (lo hi : Nat)
 /--
 In-place quicksort.
 
-`qsort as lt low high` sorts the subarray `as[low:high+1]` in-place using `lt` to compare elements.
+`qsort as lt lo hi` sorts the subarray `as[lo:hi+1]` in-place using `lt` to compare elements.
 -/
 @[inline] def qsort (as : Array α) (lt : α → α → Bool := by exact (· < ·))
-    (low := 0) (high := as.size - 1) : Array α :=
-  let rec @[specialize] sort {n} (as : Vector α n) (lo hi : Nat)
+    (lo := 0) (hi := as.size - 1) : Array α :=
+  let rec @[specialize] sort {n} (as : Vector α n) (lo hi : Nat) (w : lo ≤ hi := by omega)
       (hlo : lo < n := by omega) (hhi : hi < n := by omega) :=
     if h₁ : lo < hi then
       let ⟨⟨mid, hmid⟩, as⟩ := qpartition as lt lo hi
       if h₂ : mid ≥ hi then
+        -- This only occurs when `hi ≤ lo`,
+        -- and thus `as[lo:hi+1]` is trivially already sorted.
         as
       else
+        -- Otherwise, we recursively sort the two subarrays.
         sort (sort as lo mid) (mid+1) hi
     else as
   if h : as.size = 0 then
     as
   else
-    let low := min low (as.size - 1)
-    let high := min high (as.size - 1)
-    sort as.toVector low high |>.toArray
+    let lo := min lo (as.size - 1)
+    let hi := max lo (min hi (as.size - 1))
+    sort as.toVector lo hi |>.toArray
 
 set_option linter.unusedVariables.funArgs false in
 /--

src/Init/Data/Array/Range.lean

@@ -29,6 +29,7 @@ open Nat
 
 /-! ### range' -/
 
+@[grind _=_]
 theorem range'_succ {s n step} : range' s (n + 1) step = #[s] ++ range' (s + step) n step := by
   rw [← toList_inj]
   simp [List.range'_succ]
@@ -39,16 +40,17 @@ theorem range'_succ {s n step} : range' s (n + 1) step = #[s] ++ range' (s + ste
 theorem range'_ne_empty_iff : range' s n step ≠ #[] ↔ n ≠ 0 := by
   cases n <;> simp
 
-@[simp] theorem range'_zero : range' s 0 step = #[] := by
+@[simp, grind =] theorem range'_zero : range' s 0 step = #[] := by
   simp
 
-@[simp] theorem range'_one {s step : Nat} : range' s 1 step = #[s] := by
+@[simp, grind =] theorem range'_one {s step : Nat} : range' s 1 step = #[s] := by
   simp [range', ofFn, ofFn.go]
 
 @[simp] theorem range'_inj : range' s n = range' s' n' ↔ n = n' ∧ (n = 0 ∨ s = s') := by
   rw [← toList_inj]
   simp [List.range'_inj]
 
+@[grind =]
 theorem mem_range' {n} : m ∈ range' s n step ↔ ∃ i < n, m = s + step * i := by
   simp [range']
   constructor
@@ -57,6 +59,7 @@ theorem mem_range' {n} : m ∈ range' s n step ↔ ∃ i < n, m = s + step * i :
   · rintro ⟨i, w, h'⟩
     exact ⟨⟨i, w⟩, by simp_all⟩
 
+@[simp, grind =]
 theorem pop_range' : (range' s n step).pop = range' s (n - 1) step := by
   ext <;> simp
 
@@ -66,6 +69,7 @@ theorem map_add_range' {a} (s n step) : map (a + ·) (range' s n step) = range'
 theorem range'_succ_left : range' (s + 1) n step = (range' s n step).map (· + 1) := by
   ext <;> simp <;> omega
 
+@[grind _=_]
 theorem range'_append {s m n step : Nat} :
     range' s m step ++ range' (s + step * m) n step = range' s (m + n) step := by
   ext i h₁ h₂
@@ -77,7 +81,8 @@ theorem range'_append {s m n step : Nat} :
     have : step * m ≤ step * i := by exact mul_le_mul_left step h
     omega
 
-@[simp] theorem range'_append_1 {s m n : Nat} :
+@[simp, grind _=_]
+theorem range'_append_1 {s m n : Nat} :
     range' s m ++ range' (s + m) n = range' s (m + n) := by simpa using range'_append (step := 1)
 
 theorem range'_concat {s n : Nat} : range' s (n + 1) step = range' s n step ++ #[s + step * n] := by
@@ -86,7 +91,7 @@ theorem range'_concat {s n : Nat} : range' s (n + 1) step = range' s n step ++ #
 theorem range'_1_concat {s n : Nat} : range' s (n + 1) = range' s n ++ #[s + n] := by
   simp [range'_concat]
 
-@[simp] theorem mem_range'_1 : m ∈ range' s n ↔ s ≤ m ∧ m < s + n := by
+@[simp, grind =] theorem mem_range'_1 : m ∈ range' s n ↔ s ≤ m ∧ m < s + n := by
   simp [mem_range']; exact ⟨
     fun ⟨i, h, e⟩ => e ▸ ⟨Nat.le_add_right .., Nat.add_lt_add_left h _⟩,
     fun ⟨h₁, h₂⟩ => ⟨m - s, Nat.sub_lt_left_of_lt_add h₁ h₂, (Nat.add_sub_cancel' h₁).symm⟩⟩
@@ -116,14 +121,26 @@ theorem range'_eq_append_iff : range' s n = xs ++ ys ↔ ∃ k, k ≤ n ∧ xs =
   simp only [List.find?_toArray]
   simp
 
+@[grind =]
 theorem erase_range' :
     (range' s n).erase i =
       range' s (min n (i - s)) ++ range' (max s (i + 1)) (min s (i + 1) + n - (i + 1)) := by
   simp only [← List.toArray_range', List.erase_toArray]
   simp [List.erase_range']
 
+@[simp, grind =]
+theorem count_range' {a s n step} (h : 0 < step := by simp) :
+    count a (range' s n step) = if ∃ i, i < n ∧ a = s + step * i then 1 else 0 := by
+  rw [← List.toArray_range', List.count_toArray, ← List.count_range' h]
+
+@[simp, grind =]
+theorem count_range_1' {a s n} :
+    count a (range' s n) = if s ≤ a ∧ a < s + n then 1 else 0 := by
+  rw [← List.toArray_range', List.count_toArray, ← List.count_range_1']
+
 /-! ### range -/
 
+@[grind _=_]
 theorem range_eq_range' {n : Nat} : range n = range' 0 n := by
   simp [range, range']
 
@@ -145,6 +162,7 @@ theorem range'_eq_map_range {s n : Nat} : range' s n = map (s + ·) (range n) :=
 theorem range_ne_empty_iff {n : Nat} : range n ≠ #[] ↔ n ≠ 0 := by
   cases n <;> simp
 
+@[grind _=_]
 theorem range_succ {n : Nat} : range (succ n) = range n ++ #[n] := by
   ext i h₁ h₂
   · simp
@@ -160,7 +178,7 @@ theorem range_add {n m : Nat} : range (n + m) = range n ++ (range m).map (n + ·
 theorem reverse_range' {s n : Nat} : reverse (range' s n) = map (s + n - 1 - ·) (range n) := by
   simp [← toList_inj, List.reverse_range']
 
-@[simp]
+@[simp, grind =]
 theorem mem_range {m n : Nat} : m ∈ range n ↔ m < n := by
   simp only [range_eq_range', mem_range'_1, Nat.zero_le, true_and, Nat.zero_add]
 
@@ -168,20 +186,25 @@ theorem not_mem_range_self {n : Nat} : n ∉ range n := by simp
 
 theorem self_mem_range_succ {n : Nat} : n ∈ range (n + 1) := by simp
 
-@[simp] theorem take_range {i n : Nat} : take (range n) i = range (min i n) := by
+@[simp, grind =] theorem take_range {i n : Nat} : take (range n) i = range (min i n) := by
   ext <;> simp
 
-@[simp] theorem find?_range_eq_some {n : Nat} {i : Nat} {p : Nat → Bool} :
+@[simp, grind =] theorem find?_range_eq_some {n : Nat} {i : Nat} {p : Nat → Bool} :
     (range n).find? p = some i ↔ p i ∧ i ∈ range n ∧ ∀ j, j < i → !p j := by
   simp [range_eq_range']
 
-@[simp] theorem find?_range_eq_none {n : Nat} {p : Nat → Bool} :
+@[simp, grind =] theorem find?_range_eq_none {n : Nat} {p : Nat → Bool} :
     (range n).find? p = none ↔ ∀ i, i < n → !p i := by
   simp only [← List.toArray_range, List.find?_toArray, List.find?_range_eq_none]
 
+@[grind =]
 theorem erase_range : (range n).erase i = range (min n i) ++ range' (i + 1) (n - (i + 1)) := by
   simp [range_eq_range', erase_range']
 
+@[simp, grind =]
+theorem count_range {a n} :
+    count a (range n) = if a < n then 1 else 0 := by
+  rw [← List.toArray_range, List.count_toArray, ← List.count_range]
 
 /-! ### zipIdx -/
 
@@ -190,7 +213,7 @@ theorem zipIdx_eq_empty_iff {xs : Array α} {i : Nat} : xs.zipIdx i = #[] ↔ xs
   cases xs
   simp
 
-@[simp]
+@[simp, grind =]
 theorem getElem?_zipIdx {xs : Array α} {i j} : (zipIdx xs i)[j]? = xs[j]?.map fun a => (a, i + j) := by
   simp [getElem?_def]
 
@@ -233,7 +256,7 @@ theorem zipIdx_eq_map_add {xs : Array α} {i : Nat} :
   simp only [zipIdx_toArray, List.map_toArray, mk.injEq]
   rw [List.zipIdx_eq_map_add]
 
-@[simp]
+@[simp, grind =]
 theorem zipIdx_singleton {x : α} {k : Nat} : zipIdx #[x] k = #[(x, k)] :=
   rfl
 
@@ -281,6 +304,7 @@ theorem zipIdx_map {xs : Array α} {k : Nat} {f : α → β} :
   cases xs
   simp [List.zipIdx_map]
 
+@[grind =]
 theorem zipIdx_append {xs ys : Array α} {k : Nat} :
     zipIdx (xs ++ ys) k = zipIdx xs k ++ zipIdx ys (k + xs.size) := by
   cases xs

src/Init/Data/Array/Set.lean

@@ -24,7 +24,7 @@ Examples:
 * `#[0, 1, 2].set 1 5 = #[0, 5, 2]`
 * `#["orange", "apple"].set 1 "grape" = #["orange", "grape"]`
 -/
-@[extern "lean_array_fset"]
+@[extern "lean_array_fset", expose]
 def Array.set (xs : Array α) (i : @& Nat) (v : α) (h : i < xs.size := by get_elem_tactic) :
     Array α where
   toList := xs.toList.set i v
@@ -40,17 +40,15 @@ Examples:
 * `#["orange", "apple"].setIfInBounds 1 "grape" = #["orange", "grape"]`
 * `#["orange", "apple"].setIfInBounds 5 "grape" = #["orange", "apple"]`
 -/
-@[inline] def Array.setIfInBounds (xs : Array α) (i : Nat) (v : α) : Array α :=
+@[inline, expose] def Array.setIfInBounds (xs : Array α) (i : Nat) (v : α) : Array α :=
   dite (LT.lt i xs.size) (fun h => xs.set i v h) (fun _ => xs)
 
-@[deprecated Array.setIfInBounds (since := "2024-11-24")] abbrev Array.setD := @Array.setIfInBounds
-
 /--
 Set an element in an array, or panic if the index is out of bounds.
 
 This will perform the update destructively provided that `a` has a reference
 count of 1 when called.
 -/
-@[extern "lean_array_set"]
+@[extern "lean_array_set", expose]
 def Array.set! (xs : Array α) (i : @& Nat) (v : α) : Array α :=
   Array.setIfInBounds xs i v

src/Init/Data/Array/Subarray.lean

@@ -290,7 +290,7 @@ Examples:
 -/
 @[inline]
 def foldl {α : Type u} {β : Type v} (f : β → α → β) (init : β) (as : Subarray α) : β :=
-  Id.run <| as.foldlM f (init := init)
+  Id.run <| as.foldlM (pure <| f · ·) (init := init)
 
 /--
 Folds an operation from right to left over the elements in a subarray.
@@ -304,7 +304,7 @@ Examples:
 -/
 @[inline]
 def foldr {α : Type u} {β : Type v} (f : α → β → β) (init : β) (as : Subarray α) : β :=
-  Id.run <| as.foldrM f (init := init)
+  Id.run <| as.foldrM (pure <| f · ·) (init := init)
 
 /--
 Checks whether any of the elements in a subarray satisfy a Boolean predicate.
@@ -314,7 +314,7 @@ an element that satisfies the predicate is found.
 -/
 @[inline]
 def any {α : Type u} (p : α → Bool) (as : Subarray α) : Bool :=
-  Id.run <| as.anyM p
+  Id.run <| as.anyM (pure <| p ·)
 
 /--
 Checks whether all of the elements in a subarray satisfy a Boolean predicate.
@@ -324,7 +324,7 @@ an element that does not satisfy the predicate is found.
 -/
 @[inline]
 def all {α : Type u} (p : α → Bool) (as : Subarray α) : Bool :=
-  Id.run <| as.allM p
+  Id.run <| as.allM (pure <| p ·)
 
 /--
 Applies a monadic function to each element in a subarray in reverse order, stopping at the first
@@ -394,7 +394,7 @@ Examples:
 -/
 @[inline]
 def findRev? {α : Type} (as : Subarray α) (p : α → Bool) : Option α :=
-  Id.run <| as.findRevM? p
+  Id.run <| as.findRevM? (pure <| p ·)
 
 end Subarray
 

src/Init/Data/Array/Zip.lean

@@ -45,6 +45,7 @@ theorem zipWith_self {f : α → α → δ} {xs : Array α} : zipWith f xs xs =
 See also `getElem?_zipWith'` for a variant
 using `Option.map` and `Option.bind` rather than a `match`.
 -/
+@[grind =]
 theorem getElem?_zipWith {f : α → β → γ} {i : Nat} :
     (zipWith f as bs)[i]? = match as[i]?, bs[i]? with
       | some a, some b => some (f a b) | _, _ => none := by
@@ -76,31 +77,35 @@ theorem getElem?_zip_eq_some {as : Array α} {bs : Array β} {z : α × β} {i :
   · rintro ⟨h₀, h₁⟩
     exact ⟨_, _, h₀, h₁, rfl⟩
 
-@[simp]
+@[simp, grind =]
 theorem zipWith_map {μ} {f : γ → δ → μ} {g : α → γ} {h : β → δ} {as : Array α} {bs : Array β} :
     zipWith f (as.map g) (bs.map h) = zipWith (fun a b => f (g a) (h b)) as bs := by
   cases as
   cases bs
   simp [List.zipWith_map]
 
+@[grind =]
 theorem zipWith_map_left {as : Array α} {bs : Array β} {f : α → α'} {g : α' → β → γ} :
     zipWith g (as.map f) bs = zipWith (fun a b => g (f a) b) as bs := by
   cases as
   cases bs
   simp [List.zipWith_map_left]
 
+@[grind =]
 theorem zipWith_map_right {as : Array α} {bs : Array β} {f : β → β'} {g : α → β' → γ} :
     zipWith g as (bs.map f) = zipWith (fun a b => g a (f b)) as bs := by
   cases as
   cases bs
   simp [List.zipWith_map_right]
 
+@[grind =]
 theorem zipWith_foldr_eq_zip_foldr {f : α → β → γ} {i : δ} :
     (zipWith f as bs).foldr g i = (zip as bs).foldr (fun p r => g (f p.1 p.2) r) i := by
   cases as
   cases bs
   simp [List.zipWith_foldr_eq_zip_foldr]
 
+@[grind =]
 theorem zipWith_foldl_eq_zip_foldl {f : α → β → γ} {i : δ} :
     (zipWith f as bs).foldl g i = (zip as bs).foldl (fun r p => g r (f p.1 p.2)) i := by
   cases as
@@ -111,22 +116,26 @@ theorem zipWith_foldl_eq_zip_foldl {f : α → β → γ} {i : δ} :
 theorem zipWith_eq_empty_iff {f : α → β → γ} {as : Array α} {bs : Array β} : zipWith f as bs = #[] ↔ as = #[] ∨ bs = #[] := by
   cases as <;> cases bs <;> simp
 
+@[grind =]
 theorem map_zipWith {δ : Type _} {f : α → β} {g : γ → δ → α} {cs : Array γ} {ds : Array δ} :
     map f (zipWith g cs ds) = zipWith (fun x y => f (g x y)) cs ds := by
   cases cs
   cases ds
   simp [List.map_zipWith]
 
+@[grind =]
 theorem take_zipWith : (zipWith f as bs).take i = zipWith f (as.take i) (bs.take i) := by
   cases as
   cases bs
   simp [List.take_zipWith]
 
+@[grind =]
 theorem extract_zipWith : (zipWith f as bs).extract i j = zipWith f (as.extract i j) (bs.extract i j) := by
   cases as
   cases bs
   simp [List.drop_zipWith, List.take_zipWith]
 
+@[grind =]
 theorem zipWith_append {f : α → β → γ} {as as' : Array α} {bs bs' : Array β}
     (h : as.size = bs.size) :
     zipWith f (as ++ as') (bs ++ bs') = zipWith f as bs ++ zipWith f as' bs' := by
@@ -152,7 +161,7 @@ theorem zipWith_eq_append_iff {f : α → β → γ} {as : Array α} {bs : Array
   · rintro ⟨⟨ws⟩, ⟨xs⟩, ⟨ys⟩, ⟨zs⟩, h, rfl, rfl, h₁, h₂⟩
     exact ⟨ws, xs, ys, zs, by simp_all⟩
 
-@[simp] theorem zipWith_replicate {a : α} {b : β} {m n : Nat} :
+@[simp, grind =] theorem zipWith_replicate {a : α} {b : β} {m n : Nat} :
     zipWith f (replicate m a) (replicate n b) = replicate (min m n) (f a b) := by
   simp [← List.toArray_replicate]
 
@@ -184,6 +193,7 @@ theorem zipWith_eq_zipWith_take_min (as : Array α) (bs : Array β) :
   simp
   rw [List.zipWith_eq_zipWith_take_min]
 
+@[grind =]
 theorem reverse_zipWith (h : as.size = bs.size) :
     (zipWith f as bs).reverse = zipWith f as.reverse bs.reverse := by
   cases as
@@ -200,7 +210,7 @@ theorem lt_size_right_of_zip {i : Nat} {as : Array α} {bs : Array β} (h : i <
     i < bs.size :=
   lt_size_right_of_zipWith h
 
-@[simp]
+@[simp, grind =]
 theorem getElem_zip {as : Array α} {bs : Array β} {i : Nat} {h : i < (zip as bs).size} :
     (zip as bs)[i] =
       (as[i]'(lt_size_left_of_zip h), bs[i]'(lt_size_right_of_zip h)) :=
@@ -211,18 +221,22 @@ theorem zip_eq_zipWith {as : Array α} {bs : Array β} : zip as bs = zipWith Pro
   cases bs
   simp [List.zip_eq_zipWith]
 
+@[grind _=_]
 theorem zip_map {f : α → γ} {g : β → δ} {as : Array α} {bs : Array β} :
     zip (as.map f) (bs.map g) = (zip as bs).map (Prod.map f g) := by
   cases as
   cases bs
   simp [List.zip_map]
 
+@[grind _=_]
 theorem zip_map_left {f : α → γ} {as : Array α} {bs : Array β} :
     zip (as.map f) bs = (zip as bs).map (Prod.map f id) := by rw [← zip_map, map_id]
 
+@[grind _=_]
 theorem zip_map_right {f : β → γ} {as : Array α} {bs : Array β} :
     zip as (bs.map f) = (zip as bs).map (Prod.map id f) := by rw [← zip_map, map_id]
 
+@[grind =]
 theorem zip_append {as bs : Array α} {cs ds : Array β} (_h : as.size = cs.size) :
     zip (as ++ bs) (cs ++ ds) = zip as cs ++ zip bs ds := by
   cases as
@@ -231,6 +245,7 @@ theorem zip_append {as bs : Array α} {cs ds : Array β} (_h : as.size = cs.size
   cases ds
   simp_all [List.zip_append]
 
+@[grind =]
 theorem zip_map' {f : α → β} {g : α → γ} {xs : Array α} :
     zip (xs.map f) (xs.map g) = xs.map fun a => (f a, g a) := by
   cases xs
@@ -276,7 +291,7 @@ theorem zip_eq_append_iff {as : Array α} {bs : Array β} :
       ∃ as₁ as₂ bs₁ bs₂, as₁.size = bs₁.size ∧ as = as₁ ++ as₂ ∧ bs = bs₁ ++ bs₂ ∧ xs = zip as₁ bs₁ ∧ ys = zip as₂ bs₂ := by
   simp [zip_eq_zipWith, zipWith_eq_append_iff]
 
-@[simp] theorem zip_replicate {a : α} {b : β} {m n : Nat} :
+@[simp, grind =] theorem zip_replicate {a : α} {b : β} {m n : Nat} :
     zip (replicate m a) (replicate n b) = replicate (min m n) (a, b) := by
   simp [← List.toArray_replicate]
 
@@ -293,6 +308,7 @@ theorem zip_eq_zip_take_min {as : Array α} {bs : Array β} :
 
 /-! ### zipWithAll -/
 
+@[grind =]
 theorem getElem?_zipWithAll {f : Option α → Option β → γ} {i : Nat} :
     (zipWithAll f as bs)[i]? = match as[i]?, bs[i]? with
       | none, none => .none | a?, b? => some (f a? b?) := by
@@ -301,31 +317,35 @@ theorem getElem?_zipWithAll {f : Option α → Option β → γ} {i : Nat} :
   simp [List.getElem?_zipWithAll]
   rfl
 
+@[grind =]
 theorem zipWithAll_map {μ} {f : Option γ → Option δ → μ} {g : α → γ} {h : β → δ} {as : Array α} {bs : Array β} :
     zipWithAll f (as.map g) (bs.map h) = zipWithAll (fun a b => f (g <$> a) (h <$> b)) as bs := by
   cases as
   cases bs
   simp [List.zipWithAll_map]
 
+@[grind =]
 theorem zipWithAll_map_left {as : Array α} {bs : Array β} {f : α → α'} {g : Option α' → Option β → γ} :
     zipWithAll g (as.map f) bs = zipWithAll (fun a b => g (f <$> a) b) as bs := by
   cases as
   cases bs
   simp [List.zipWithAll_map_left]
 
+@[grind =]
 theorem zipWithAll_map_right {as : Array α} {bs : Array β} {f : β → β'} {g : Option α → Option β' → γ} :
     zipWithAll g as (bs.map f) = zipWithAll (fun a b => g a (f <$> b)) as bs := by
   cases as
   cases bs
   simp [List.zipWithAll_map_right]
 
+@[grind =]
 theorem map_zipWithAll {δ : Type _} {f : α → β} {g : Option γ → Option δ → α} {cs : Array γ} {ds : Array δ} :
     map f (zipWithAll g cs ds) = zipWithAll (fun x y => f (g x y)) cs ds := by
   cases cs
   cases ds
   simp [List.map_zipWithAll]
 
-@[simp] theorem zipWithAll_replicate {a : α} {b : β} {n : Nat} :
+@[simp, grind =] theorem zipWithAll_replicate {a : α} {b : β} {n : Nat} :
     zipWithAll f (replicate n a) (replicate n b) = replicate n (f (some a) (some b)) := by
   simp [← List.toArray_replicate]
 
@@ -334,12 +354,15 @@ abbrev zipWithAll_mkArray := @zipWithAll_replicate
 
 /-! ### unzip -/
 
-@[simp] theorem unzip_fst : (unzip l).fst = l.map Prod.fst := by
-  induction l <;> simp_all
+@[deprecated fst_unzip (since := "2025-05-26")]
+theorem unzip_fst : (unzip l).fst = l.map Prod.fst := by
+  simp
 
-@[simp] theorem unzip_snd : (unzip l).snd = l.map Prod.snd := by
-  induction l <;> simp_all
+@[deprecated snd_unzip (since := "2025-05-26")]
+theorem unzip_snd : (unzip l).snd = l.map Prod.snd := by
+  simp
 
+@[grind =]
 theorem unzip_eq_map {xs : Array (α × β)} : unzip xs = (xs.map Prod.fst, xs.map Prod.snd) := by
   cases xs
   simp [List.unzip_eq_map]
@@ -371,11 +394,13 @@ theorem unzip_zip {as : Array α} {bs : Array β} (h : as.size = bs.size) :
 
 theorem zip_of_prod {as : Array α} {bs : Array β} {xs : Array (α × β)} (hl : xs.map Prod.fst = as)
     (hr : xs.map Prod.snd = bs) : xs = as.zip bs := by
-  rw [← hl, ← hr, ← zip_unzip xs, ← unzip_fst, ← unzip_snd, zip_unzip, zip_unzip]
+  rw [← hl, ← hr, ← zip_unzip xs, ← fst_unzip, ← snd_unzip, zip_unzip, zip_unzip]
 
-@[simp] theorem unzip_replicate {n : Nat} {a : α} {b : β} :
+@[simp, grind =] theorem unzip_replicate {n : Nat} {a : α} {b : β} :
     unzip (replicate n (a, b)) = (replicate n a, replicate n b) := by
   ext1 <;> simp
 
 @[deprecated unzip_replicate (since := "2025-03-18")]
 abbrev unzip_mkArray := @unzip_replicate
+
+end Array

src/Init/Data/BEq.lean

@@ -27,7 +27,7 @@ class EquivBEq (α) [BEq α] : Prop extends PartialEquivBEq α, ReflBEq α
 theorem BEq.symm [BEq α] [PartialEquivBEq α] {a b : α} : a == b → b == a :=
   PartialEquivBEq.symm
 
-@[grind] theorem BEq.comm [BEq α] [PartialEquivBEq α] {a b : α} : (a == b) = (b == a) :=
+theorem BEq.comm [BEq α] [PartialEquivBEq α] {a b : α} : (a == b) = (b == a) :=
   Bool.eq_iff_iff.2 ⟨BEq.symm, BEq.symm⟩
 
 theorem bne_comm [BEq α] [PartialEquivBEq α] {a b : α} : (a != b) = (b != a) := by

src/Init/Data/BitVec.lean

@@ -6,7 +6,10 @@ Authors: Kim Morrison
 module
 
 prelude
+import Init.Data.BitVec.BasicAux
 import Init.Data.BitVec.Basic
+import Init.Data.BitVec.Bootstrap
 import Init.Data.BitVec.Bitblast
-import Init.Data.BitVec.Folds
+import Init.Data.BitVec.Decidable
 import Init.Data.BitVec.Lemmas
+import Init.Data.BitVec.Folds

src/Init/Data/BitVec/Basic.lean

@@ -61,7 +61,7 @@ end subsingleton
 section zero_allOnes
 
 /-- Returns a bitvector of size `n` where all bits are `0`. -/
-protected def zero (n : Nat) : BitVec n := .ofNatLT 0 (Nat.two_pow_pos n)
+@[expose] protected def zero (n : Nat) : BitVec n := .ofNatLT 0 (Nat.two_pow_pos n)
 instance : Inhabited (BitVec n) where default := .zero n
 
 /-- Returns a bitvector of size `n` where all bits are `1`. -/
@@ -74,28 +74,30 @@ section getXsb
 
 /--
 Returns the `i`th least significant bit.
-
-This will be renamed `getLsb` after the existing deprecated alias is removed.
 -/
-@[inline] def getLsb' (x : BitVec w) (i : Fin w) : Bool := x.toNat.testBit i
+@[inline, expose] def getLsb (x : BitVec w) (i : Fin w) : Bool := x.toNat.testBit i
+
+@[deprecated getLsb (since := "2025-06-17"), inherit_doc getLsb]
+abbrev getLsb' := @getLsb
 
 /-- Returns the `i`th least significant bit, or `none` if `i ≥ w`. -/
-@[inline] def getLsb? (x : BitVec w) (i : Nat) : Option Bool :=
-  if h : i < w then some (getLsb' x ⟨i, h⟩) else none
+@[inline, expose] def getLsb? (x : BitVec w) (i : Nat) : Option Bool :=
+  if h : i < w then some (getLsb x ⟨i, h⟩) else none
 
 /--
 Returns the `i`th most significant bit.
-
-This will be renamed `BitVec.getMsb` after the existing deprecated alias is removed.
 -/
-@[inline] def getMsb' (x : BitVec w) (i : Fin w) : Bool := x.getLsb' ⟨w-1-i, by omega⟩
+@[inline] def getMsb (x : BitVec w) (i : Fin w) : Bool := x.getLsb ⟨w-1-i, by omega⟩
+
+@[deprecated getMsb (since := "2025-06-17"), inherit_doc getMsb]
+abbrev getMsb' := @getMsb
 
 /-- Returns the `i`th most significant bit or `none` if `i ≥ w`. -/
 @[inline] def getMsb? (x : BitVec w) (i : Nat) : Option Bool :=
-  if h : i < w then some (getMsb' x ⟨i, h⟩) else none
+  if h : i < w then some (getMsb x ⟨i, h⟩) else none
 
 /-- Returns the `i`th least significant bit or `false` if `i ≥ w`. -/
-@[inline] def getLsbD (x : BitVec w) (i : Nat) : Bool :=
+@[inline, expose] def getLsbD (x : BitVec w) (i : Nat) : Bool :=
   x.toNat.testBit i
 
 /-- Returns the `i`th most significant bit, or `false` if `i ≥ w`. -/
@@ -110,11 +112,11 @@ end getXsb
 section getElem
 
 instance : GetElem (BitVec w) Nat Bool fun _ i => i < w where
-  getElem xs i h := xs.getLsb' ⟨i, h⟩
+  getElem xs i h := xs.getLsb ⟨i, h⟩
 
 /-- We prefer `x[i]` as the simp normal form for `getLsb'` -/
-@[simp] theorem getLsb'_eq_getElem (x : BitVec w) (i : Fin w) :
-    x.getLsb' i = x[i] := rfl
+@[simp] theorem getLsb_eq_getElem (x : BitVec w) (i : Fin w) :
+    x.getLsb i = x[i] := rfl
 
 /-- We prefer `x[i]?` as the simp normal form for `getLsb?` -/
 @[simp] theorem getLsb?_eq_getElem? (x : BitVec w) (i : Nat) :
@@ -134,6 +136,7 @@ section Int
 /--
 Interprets the bitvector as an integer stored in two's complement form.
 -/
+@[expose]
 protected def toInt (x : BitVec n) : Int :=
   if 2 * x.toNat < 2^n then
     x.toNat
@@ -147,6 +150,7 @@ over- and underflowing as needed.
 The underlying `Nat` is `(2^n + (i mod 2^n)) mod 2^n`. Converting the bitvector back to an `Int`
 with `BitVec.toInt` results in the value `i.bmod (2^n)`.
 -/
+@[expose]
 protected def ofInt (n : Nat) (i : Int) : BitVec n := .ofNatLT (i % (Int.ofNat (2^n))).toNat (by
   apply (Int.toNat_lt _).mpr
   · apply Int.emod_lt_of_pos
@@ -172,7 +176,7 @@ recommended_spelling "zero" for "0#n" in [BitVec.ofNat, «term__#__»]
 recommended_spelling "one" for "1#n" in [BitVec.ofNat, «term__#__»]
 
 /-- Unexpander for bitvector literals. -/
-@[app_unexpander BitVec.ofNat] def unexpandBitVecOfNat : Lean.PrettyPrinter.Unexpander
+@[app_unexpander BitVec.ofNat] meta def unexpandBitVecOfNat : Lean.PrettyPrinter.Unexpander
   | `($(_) $n $i:num) => `($i:num#$n)
   | _ => throw ()
 
@@ -181,7 +185,7 @@ scoped syntax:max term:max noWs "#'" noWs term:max : term
 macro_rules | `($i#'$p) => `(BitVec.ofNatLT $i $p)
 
 /-- Unexpander for bitvector literals without truncation. -/
-@[app_unexpander BitVec.ofNatLT] def unexpandBitVecOfNatLt : Lean.PrettyPrinter.Unexpander
+@[app_unexpander BitVec.ofNatLT] meta def unexpandBitVecOfNatLt : Lean.PrettyPrinter.Unexpander
   | `($(_) $i $p) => `($i#'$p)
   | _ => throw ()
 
@@ -218,12 +222,14 @@ Usually accessed via the `-` prefix operator.
 
 SMT-LIB name: `bvneg`.
 -/
+@[expose]
 protected def neg (x : BitVec n) : BitVec n := .ofNat n (2^n - x.toNat)
 instance : Neg (BitVec n) := ⟨.neg⟩
 
 /--
 Returns the absolute value of a signed bitvector.
 -/
+@[expose]
 protected def abs (x : BitVec n) : BitVec n := if x.msb then .neg x else x
 
 /--
@@ -232,6 +238,7 @@ modulo `2^n`. Usually accessed via the `*` operator.
 
 SMT-LIB name: `bvmul`.
 -/
+@[expose]
 protected def mul (x y : BitVec n) : BitVec n := BitVec.ofNat n (x.toNat * y.toNat)
 instance : Mul (BitVec n) := ⟨.mul⟩
 
@@ -242,6 +249,7 @@ Note that this is currently an inefficient implementation,
 and should be replaced via an `@[extern]` with a native implementation.
 See https://github.com/leanprover/lean4/issues/7887.
 -/
+@[expose]
 protected def pow (x : BitVec n) (y : Nat) : BitVec n :=
   match y with
   | 0 => 1
@@ -253,6 +261,7 @@ instance : Pow (BitVec n) Nat where
 Unsigned division of bitvectors using the Lean convention where division by zero returns zero.
 Usually accessed via the `/` operator.
 -/
+@[expose]
 def udiv (x y : BitVec n) : BitVec n :=
   (x.toNat / y.toNat)#'(Nat.lt_of_le_of_lt (Nat.div_le_self _ _) x.isLt)
 instance : Div (BitVec n) := ⟨.udiv⟩
@@ -262,6 +271,7 @@ Unsigned modulo for bitvectors. Usually accessed via the `%` operator.
 
 SMT-LIB name: `bvurem`.
 -/
+@[expose]
 def umod (x y : BitVec n) : BitVec n :=
   (x.toNat % y.toNat)#'(Nat.lt_of_le_of_lt (Nat.mod_le _ _) x.isLt)
 instance : Mod (BitVec n) := ⟨.umod⟩
@@ -273,6 +283,7 @@ where division by zero returns `BitVector.allOnes n`.
 
 SMT-LIB name: `bvudiv`.
 -/
+@[expose]
 def smtUDiv (x y : BitVec n) : BitVec n := if y = 0 then allOnes n else udiv x y
 
 /--
@@ -342,6 +353,7 @@ end arithmetic
 section bool
 
 /-- Turns a `Bool` into a bitvector of length `1`. -/
+@[expose]
 def ofBool (b : Bool) : BitVec 1 := cond b 1 0
 
 @[simp] theorem ofBool_false : ofBool false = 0 := by trivial
@@ -359,6 +371,7 @@ Unsigned less-than for bitvectors.
 
 SMT-LIB name: `bvult`.
 -/
+@[expose]
 protected def ult (x y : BitVec n) : Bool := x.toNat < y.toNat
 
 /--
@@ -366,6 +379,7 @@ Unsigned less-than-or-equal-to for bitvectors.
 
 SMT-LIB name: `bvule`.
 -/
+@[expose]
 protected def ule (x y : BitVec n) : Bool := x.toNat ≤ y.toNat
 
 /--
@@ -377,6 +391,7 @@ Examples:
  * `BitVec.slt 6#4 7 = true`
  * `BitVec.slt 7#4 8 = false`
 -/
+@[expose]
 protected def slt (x y : BitVec n) : Bool := x.toInt < y.toInt
 
 /--
@@ -384,6 +399,7 @@ Signed less-than-or-equal-to for bitvectors.
 
 SMT-LIB name: `bvsle`.
 -/
+@[expose]
 protected def sle (x y : BitVec n) : Bool := x.toInt ≤ y.toInt
 
 end relations
@@ -397,7 +413,7 @@ width `m`.
 Using `x.cast eq` should be preferred over `eq ▸ x` because there are special-purpose `simp` lemmas
 that can more consistently simplify `BitVec.cast` away.
 -/
-@[inline] protected def cast (eq : n = m) (x : BitVec n) : BitVec m := .ofNatLT x.toNat (eq ▸ x.isLt)
+@[inline, expose] protected def cast (eq : n = m) (x : BitVec n) : BitVec m := .ofNatLT x.toNat (eq ▸ x.isLt)
 
 @[simp] theorem cast_ofNat {n m : Nat} (h : n = m) (x : Nat) :
     (BitVec.ofNat n x).cast h = BitVec.ofNat m x := by
@@ -413,6 +429,7 @@ that can more consistently simplify `BitVec.cast` away.
 Extracts the bits `start` to `start + len - 1` from a bitvector of size `n` to yield a
 new bitvector of size `len`. If `start + len > n`, then the bitvector is zero-extended.
 -/
+@[expose]
 def extractLsb' (start len : Nat) (x : BitVec n) : BitVec len := .ofNat _ (x.toNat >>> start)
 
 /--
@@ -423,6 +440,7 @@ The resulting bitvector has size `hi - lo + 1`.
 
 SMT-LIB name: `extract`.
 -/
+@[expose]
 def extractLsb (hi lo : Nat) (x : BitVec n) : BitVec (hi - lo + 1) := extractLsb' lo _ x
 
 /--
@@ -431,6 +449,7 @@ Increases the width of a bitvector to one that is at least as large by zero-exte
 This is a constant-time operation because the underlying `Nat` is unmodified; because the new width
 is at least as large as the old one, no overflow is possible.
 -/
+@[expose]
 def setWidth' {n w : Nat} (le : n ≤ w) (x : BitVec n) : BitVec w :=
   x.toNat#'(by
     apply Nat.lt_of_lt_of_le x.isLt
@@ -439,6 +458,7 @@ def setWidth' {n w : Nat} (le : n ≤ w) (x : BitVec n) : BitVec w :=
 /--
 Returns `zeroExtend (w+n) x <<< n` without needing to compute `x % 2^(2+n)`.
 -/
+@[expose]
 def shiftLeftZeroExtend (msbs : BitVec w) (m : Nat) : BitVec (w + m) :=
   let shiftLeftLt {x : Nat} (p : x < 2^w) (m : Nat) : x <<< m < 2^(w + m) := by
         simp [Nat.shiftLeft_eq, Nat.pow_add]
@@ -495,6 +515,7 @@ SMT-LIB name: `bvand`.
 Example:
  * `0b1010#4 &&& 0b0110#4 = 0b0010#4`
 -/
+@[expose]
 protected def and (x y : BitVec n) : BitVec n :=
   (x.toNat &&& y.toNat)#'(Nat.and_lt_two_pow x.toNat y.isLt)
 instance : AndOp (BitVec w) := ⟨.and⟩
@@ -507,6 +528,7 @@ SMT-LIB name: `bvor`.
 Example:
  * `0b1010#4 ||| 0b0110#4 = 0b1110#4`
 -/
+@[expose]
 protected def or (x y : BitVec n) : BitVec n :=
   (x.toNat ||| y.toNat)#'(Nat.or_lt_two_pow x.isLt y.isLt)
 instance : OrOp (BitVec w) := ⟨.or⟩
@@ -519,6 +541,7 @@ SMT-LIB name: `bvxor`.
 Example:
  * `0b1010#4 ^^^ 0b0110#4 = 0b1100#4`
 -/
+@[expose]
 protected def xor (x y : BitVec n) : BitVec n :=
   (x.toNat ^^^ y.toNat)#'(Nat.xor_lt_two_pow x.isLt y.isLt)
 instance : Xor (BitVec w) := ⟨.xor⟩
@@ -531,6 +554,7 @@ SMT-LIB name: `bvnot`.
 Example:
  * `~~~(0b0101#4) == 0b1010`
 -/
+@[expose]
 protected def not (x : BitVec n) : BitVec n := allOnes n ^^^ x
 instance : Complement (BitVec w) := ⟨.not⟩
 
@@ -540,6 +564,7 @@ equivalent to `x * 2^s`, modulo `2^n`.
 
 SMT-LIB name: `bvshl` except this operator uses a `Nat` shift value.
 -/
+@[expose]
 protected def shiftLeft (x : BitVec n) (s : Nat) : BitVec n := BitVec.ofNat n (x.toNat <<< s)
 instance : HShiftLeft (BitVec w) Nat (BitVec w) := ⟨.shiftLeft⟩
 
@@ -551,6 +576,7 @@ As a numeric operation, this is equivalent to `x / 2^s`, rounding down.
 
 SMT-LIB name: `bvlshr` except this operator uses a `Nat` shift value.
 -/
+@[expose]
 def ushiftRight (x : BitVec n) (s : Nat) : BitVec n :=
   (x.toNat >>> s)#'(by
   let ⟨x, lt⟩ := x
@@ -568,6 +594,7 @@ As a numeric operation, this is equivalent to `x.toInt >>> s`.
 
 SMT-LIB name: `bvashr` except this operator uses a `Nat` shift value.
 -/
+@[expose]
 def sshiftRight (x : BitVec n) (s : Nat) : BitVec n := .ofInt n (x.toInt >>> s)
 
 instance {n} : HShiftLeft  (BitVec m) (BitVec n) (BitVec m) := ⟨fun x y => x <<< y.toNat⟩
@@ -581,10 +608,12 @@ As a numeric operation, this is equivalent to `a.toInt >>> s.toNat`.
 
 SMT-LIB name: `bvashr`.
 -/
+@[expose]
 def sshiftRight' (a : BitVec n) (s : BitVec m) : BitVec n := a.sshiftRight s.toNat
 
 /-- Auxiliary function for `rotateLeft`, which does not take into account the case where
 the rotation amount is greater than the bitvector width. -/
+@[expose]
 def rotateLeftAux (x : BitVec w) (n : Nat) : BitVec w :=
   x <<< n ||| x >>> (w - n)
 
@@ -599,6 +628,7 @@ SMT-LIB name: `rotate_left`, except this operator uses a `Nat` shift amount.
 Example:
  * `(0b0011#4).rotateLeft 3 = 0b1001`
 -/
+@[expose]
 def rotateLeft (x : BitVec w) (n : Nat) : BitVec w := rotateLeftAux x (n % w)
 
 
@@ -606,6 +636,7 @@ def rotateLeft (x : BitVec w) (n : Nat) : BitVec w := rotateLeftAux x (n % w)
 Auxiliary function for `rotateRight`, which does not take into account the case where
 the rotation amount is greater than the bitvector width.
 -/
+@[expose]
 def rotateRightAux (x : BitVec w) (n : Nat) : BitVec w :=
   x >>> n ||| x <<< (w - n)
 
@@ -620,6 +651,7 @@ SMT-LIB name: `rotate_right`, except this operator uses a `Nat` shift amount.
 Example:
  * `rotateRight 0b01001#5 1 = 0b10100`
 -/
+@[expose]
 def rotateRight (x : BitVec w) (n : Nat) : BitVec w := rotateRightAux x (n % w)
 
 /--
@@ -631,6 +663,7 @@ SMT-LIB name: `concat`.
 Example:
  * `0xAB#8 ++ 0xCD#8 = 0xABCD#16`.
 -/
+@[expose]
 def append (msbs : BitVec n) (lsbs : BitVec m) : BitVec (n+m) :=
   shiftLeftZeroExtend msbs m ||| setWidth' (Nat.le_add_left m n) lsbs
 
@@ -653,6 +686,7 @@ result of appending a single bit to the front in the naive implementation).
 
 /-- Append a single bit to the end of a bitvector, using big endian order (see `append`).
     That is, the new bit is the least significant bit. -/
+@[expose]
 def concat {n} (msbs : BitVec n) (lsb : Bool) : BitVec (n+1) := msbs ++ (ofBool lsb)
 
 /--
@@ -660,6 +694,7 @@ Shifts all bits of `x` to the left by `1` and sets the least significant bit to
 
 This is a non-dependent version of `BitVec.concat` that does not change the total bitwidth.
 -/
+@[expose]
 def shiftConcat (x : BitVec n) (b : Bool) : BitVec n :=
   (x.concat b).truncate n
 
@@ -668,6 +703,7 @@ Prepends a single bit to the front of a bitvector, using big-endian order (see `
 
 The new bit is the most significant bit.
 -/
+@[expose]
 def cons {n} (msb : Bool) (lsbs : BitVec n) : BitVec (n+1) :=
   ((ofBool msb) ++ lsbs).cast (Nat.add_comm ..)
 
@@ -689,6 +725,12 @@ def twoPow (w : Nat) (i : Nat) : BitVec w := 1#w <<< i
 
 end bitwise
 
+/-- The bitvector of width `w` that has the smallest value when interpreted as an integer. -/
+def intMin (w : Nat) := twoPow w (w - 1)
+
+/-- The bitvector of width `w` that has the largest value when interpreted as an integer. -/
+def intMax (w : Nat) := (twoPow w (w - 1)) - 1
+
 /--
 Computes a hash of a bitvector, combining 64-bit words using `mixHash`.
 -/
@@ -752,6 +794,7 @@ Checks whether subtraction of `x` and `y` results in *unsigned* overflow.
 
 SMT-Lib name: `bvusubo`.
 -/
+@[expose]
 def usubOverflow {w : Nat} (x y : BitVec w) : Bool := x.toNat < y.toNat
 
 /--
@@ -760,6 +803,7 @@ Checks whether the subtraction of `x` and `y` results in *signed* overflow, trea
 
 SMT-Lib name: `bvssubo`.
 -/
+@[expose]
 def ssubOverflow {w : Nat} (x y : BitVec w) : Bool :=
   (x.toInt - y.toInt ≥ 2 ^ (w - 1)) || (x.toInt - y.toInt < - 2 ^ (w - 1))
 
@@ -770,6 +814,7 @@ For a bitvector `x` with nonzero width, this only happens if `x = intMin`.
 
 SMT-Lib name: `bvnego`.
 -/
+@[expose]
 def negOverflow {w : Nat} (x : BitVec w) : Bool :=
   x.toInt == - 2 ^ (w - 1)
 
@@ -779,6 +824,7 @@ For BitVecs `x` and `y` with nonzero width, this only happens if `x = intMin` an
 
 SMT-LIB name: `bvsdivo`.
 -/
+@[expose]
 def sdivOverflow {w : Nat} (x y : BitVec w) : Bool :=
   (2 ^ (w - 1) ≤ x.toInt / y.toInt) || (x.toInt / y.toInt <  - 2 ^ (w - 1))
 

src/Init/Data/BitVec/BasicAux.lean

@@ -24,7 +24,7 @@ The bitvector with value `i mod 2^n`.
 -/
 @[expose, match_pattern]
 protected def ofNat (n : Nat) (i : Nat) : BitVec n where
-  toFin := Fin.ofNat' (2^n) i
+  toFin := Fin.ofNat (2^n) i
 
 instance instOfNat : OfNat (BitVec n) i where ofNat := .ofNat n i
 
@@ -41,6 +41,7 @@ Usually accessed via the `+` operator.
 
 SMT-LIB name: `bvadd`.
 -/
+@[expose]
 protected def add (x y : BitVec n) : BitVec n := .ofNat n (x.toNat + y.toNat)
 instance : Add (BitVec n) := ⟨BitVec.add⟩
 
@@ -49,6 +50,7 @@ Subtracts one bitvector from another. This can be interpreted as either signed o
 modulo `2^n`. Usually accessed via the `-` operator.
 
 -/
+@[expose]
 protected def sub (x y : BitVec n) : BitVec n := .ofNat n ((2^n - y.toNat) + x.toNat)
 instance : Sub (BitVec n) := ⟨BitVec.sub⟩
 

src/Init/Data/BitVec/Bitblast.lean

@@ -6,12 +6,14 @@ Authors: Harun Khan, Abdalrhman M Mohamed, Joe Hendrix, Siddharth Bhat
 module
 
 prelude
-import Init.Data.BitVec.Folds
 import all Init.Data.Nat.Bitwise.Basic
 import Init.Data.Nat.Mod
 import all Init.Data.Int.DivMod
 import Init.Data.Int.LemmasAux
-import all Init.Data.BitVec.Lemmas
+import all Init.Data.BitVec.Basic
+import Init.Data.BitVec.Decidable
+import Init.Data.BitVec.Lemmas
+import Init.Data.BitVec.Folds
 
 /-!
 # Bit blasting of bitvectors
@@ -518,9 +520,6 @@ theorem msb_neg {w : Nat} {x : BitVec w} :
   rw [(show w = w - 1 + 1 by omega), Int.pow_succ] at this
   omega
 
-@[simp] theorem setWidth_neg_of_le {x : BitVec v} (h : w ≤ v) : BitVec.setWidth w (-x) = -BitVec.setWidth w x := by
-  simp [← BitVec.signExtend_eq_setWidth_of_le _ h, BitVec.signExtend_neg_of_le h]
-
 /-! ### abs -/
 
 theorem msb_abs {w : Nat} {x : BitVec w} :
@@ -548,54 +547,14 @@ theorem ult_eq_not_carry (x y : BitVec w) : x.ult y = !carry w x (~~~y) true :=
   rw [Nat.mod_eq_of_lt (by omega)]
   omega
 
-theorem ule_eq_not_ult (x y : BitVec w) : x.ule y = !y.ult x := by
-  simp [BitVec.ule, BitVec.ult, ← decide_not]
-
 theorem ule_eq_carry (x y : BitVec w) : x.ule y = carry w y (~~~x) true := by
   simp [ule_eq_not_ult, ult_eq_not_carry]
 
-/-- If two bitvectors have the same `msb`, then signed and unsigned comparisons coincide -/
-theorem slt_eq_ult_of_msb_eq {x y : BitVec w} (h : x.msb = y.msb) :
-    x.slt y = x.ult y := by
-  simp only [BitVec.slt, toInt_eq_msb_cond, BitVec.ult, decide_eq_decide, h]
-  cases y.msb <;> simp
-
-/-- If two bitvectors have different `msb`s, then unsigned comparison is determined by this bit -/
-theorem ult_eq_msb_of_msb_neq {x y : BitVec w} (h : x.msb ≠ y.msb) :
-    x.ult y = y.msb := by
-  simp only [BitVec.ult, msb_eq_decide, ne_eq, decide_eq_decide] at *
-  omega
-
-/-- If two bitvectors have different `msb`s, then signed and unsigned comparisons are opposites -/
-theorem slt_eq_not_ult_of_msb_neq {x y : BitVec w} (h : x.msb ≠ y.msb) :
-    x.slt y = !x.ult y := by
-  simp only [BitVec.slt, toInt_eq_msb_cond, Bool.eq_not_of_ne h, ult_eq_msb_of_msb_neq h]
-  cases y.msb <;> (simp [-Int.natCast_pow]; omega)
-
-theorem slt_eq_ult {x y : BitVec w} :
-    x.slt y = (x.msb != y.msb).xor (x.ult y) := by
-  by_cases h : x.msb = y.msb
-  · simp [h, slt_eq_ult_of_msb_eq]
-  · have h' : x.msb != y.msb := by simp_all
-    simp [slt_eq_not_ult_of_msb_neq h, h']
-
 theorem slt_eq_not_carry {x y : BitVec w} :
     x.slt y = (x.msb == y.msb).xor (carry w x (~~~y) true) := by
   simp only [slt_eq_ult, bne, ult_eq_not_carry]
   cases x.msb == y.msb <;> simp
 
-theorem sle_eq_not_slt {x y : BitVec w} : x.sle y = !y.slt x := by
-  simp only [BitVec.sle, BitVec.slt, ← decide_not, decide_eq_decide]; omega
-
-theorem zero_sle_eq_not_msb {w : Nat} {x : BitVec w} : BitVec.sle 0#w x = !x.msb := by
-  rw [sle_eq_not_slt, BitVec.slt_zero_eq_msb]
-
-theorem zero_sle_iff_msb_eq_false {w : Nat} {x : BitVec w} : BitVec.sle 0#w x ↔ x.msb = false := by
-  simp [zero_sle_eq_not_msb]
-
-theorem toNat_toInt_of_sle {w : Nat} {x : BitVec w} (hx : BitVec.sle 0#w x) : x.toInt.toNat = x.toNat :=
-  toNat_toInt_of_msb x (zero_sle_iff_msb_eq_false.1 hx)
-
 theorem sle_eq_carry {x y : BitVec w} :
     x.sle y = !((x.msb == y.msb).xor (carry w y (~~~x) true)) := by
   rw [sle_eq_not_slt, slt_eq_not_carry, beq_comm]
@@ -618,12 +577,6 @@ theorem neg_sle_zero (h : 0 < w) {x : BitVec w} :
   rw [sle_eq_slt_or_eq, neg_slt_zero h, sle_eq_slt_or_eq]
   simp [Bool.beq_eq_decide_eq (-x), Bool.beq_eq_decide_eq _ x, Eq.comm (a := x), Bool.or_assoc]
 
-theorem sle_eq_ule {x y : BitVec w} : x.sle y = (x.msb != y.msb ^^ x.ule y) := by
-  rw [sle_eq_not_slt, slt_eq_ult, ← Bool.xor_not, ← ule_eq_not_ult, bne_comm]
-
-theorem sle_eq_ule_of_msb_eq {x y : BitVec w} (h : x.msb = y.msb) : x.sle y = x.ule y := by
-  simp [BitVec.sle_eq_ule, h]
-
 /-! ### mul recurrence for bit blasting -/
 
 /--
@@ -631,6 +584,7 @@ A recurrence that describes multiplication as repeated addition.
 
 This function is useful for bit blasting multiplication.
 -/
+@[expose]
 def mulRec (x y : BitVec w) (s : Nat) : BitVec w :=
   let cur := if y.getLsbD s then (x <<< s) else 0
   match s with
@@ -1022,7 +976,7 @@ theorem DivModState.toNat_shiftRight_sub_one_eq
     {args : DivModArgs w} {qr : DivModState w} (h : qr.Poised args) :
     args.n.toNat >>> (qr.wn - 1)
     = (args.n.toNat >>> qr.wn) * 2 + (args.n.getLsbD (qr.wn - 1)).toNat := by
-  show BitVec.toNat (args.n >>> (qr.wn - 1)) = _
+  change BitVec.toNat (args.n >>> (qr.wn - 1)) = _
   have {..} := h -- break the structure down for `omega`
   rw [shiftRight_sub_one_eq_shiftConcat args.n h.hwn_lt]
   rw [toNat_shiftConcat_eq_of_lt (k := w - qr.wn)]
@@ -1091,6 +1045,7 @@ theorem lawful_divSubtractShift (qr : DivModState w) (h : qr.Poised args) :
 /-! ### Core division algorithm circuit -/
 
 /-- A recursive definition of division for bit blasting, in terms of a shift-subtraction circuit. -/
+@[expose]
 def divRec {w : Nat} (m : Nat) (args : DivModArgs w) (qr : DivModState w) :
     DivModState w :=
   match m with
@@ -1750,6 +1705,116 @@ theorem toInt_srem (x y : BitVec w) : (x.srem y).toInt = x.toInt.tmod y.toInt :=
         ((not_congr neg_eq_zero_iff).mpr hyz)]
       exact neg_le_intMin_of_msb_eq_true h'
 
+@[simp]
+theorem msb_intMin_umod_neg_of_msb_true {y : BitVec w} (hy : y.msb = true) :
+    (intMin w % -y).msb = false := by
+  by_cases hyintmin : y = intMin w
+  · simp [hyintmin]
+  · rw [msb_umod_of_msb_false_of_ne_zero (by simp [hyintmin, hy])]
+    simp [hy]
+
+@[simp]
+theorem msb_neg_umod_neg_of_msb_true_of_msb_true {x y : BitVec w} (hx : x.msb = true) (hy : y.msb = true) :
+      (-x % -y).msb = false := by
+  by_cases hx' : x = intMin w
+  · simp only [hx', neg_intMin, msb_intMin_umod_neg_of_msb_true hy]
+  · simp [show (-x).msb = false by simp [hx, hx']]
+
+theorem toInt_dvd_toInt_iff {x y : BitVec w} :
+    y.toInt ∣ x.toInt ↔ (if x.msb then -x else x) % (if y.msb then -y else y) = 0#w := by
+  constructor
+  <;> by_cases hxmsb : x.msb <;> by_cases hymsb: y.msb
+  <;> intros h
+  <;> simp only [hxmsb, hymsb, reduceIte, false_eq_true, toNat_eq, toNat_umod, toNat_ofNat,
+        zero_mod, toInt_eq_neg_toNat_neg_of_msb_true, Int.dvd_neg, Int.neg_dvd,
+        toInt_eq_toNat_of_msb] at h
+  <;> simp only [hxmsb, hymsb, toInt_eq_neg_toNat_neg_of_msb_true, toInt_eq_toNat_of_msb,
+        Int.dvd_neg, Int.neg_dvd, toNat_eq, toNat_umod, reduceIte, toNat_ofNat, zero_mod]
+  <;> norm_cast
+  <;> norm_cast at h
+  <;> simp only [dvd_of_mod_eq_zero, h, dvd_iff_mod_eq_zero.mp, reduceIte]
+
+theorem toInt_dvd_toInt_iff_of_msb_true_msb_false {x y : BitVec w} (hx : x.msb = true) (hy : y.msb = false) :
+    y.toInt ∣ x.toInt ↔ (-x) % y = 0#w := by
+  simpa [hx, hy] using toInt_dvd_toInt_iff (x := x) (y := y)
+
+theorem toInt_dvd_toInt_iff_of_msb_false_msb_true {x y : BitVec w} (hx : x.msb = false) (hy : y.msb = true) :
+    y.toInt ∣ x.toInt ↔ x % (-y) = 0#w := by
+  simpa [hx, hy] using toInt_dvd_toInt_iff (x := x) (y := y)
+
+@[simp]
+theorem neg_toInt_neg_umod_eq_of_msb_true_msb_true {x y : BitVec w} (hx : x.msb = true) (hy : y.msb = true) :
+    -(-(-x % -y)).toInt = (-x % -y).toNat := by
+  rw [neg_toInt_neg]
+  by_cases h : -x % -y = 0#w
+  · simp [h]
+  · rw [msb_neg_umod_neg_of_msb_true_of_msb_true hx hy]
+
+@[simp]
+theorem toInt_umod_neg_add {x y : BitVec w} (hymsb : y.msb = true) (hxmsb : x.msb = false) (hdvd : ¬y.toInt ∣ x.toInt) :
+    (x % -y + y).toInt = x.toInt % y.toInt + y.toInt := by
+  rcases w with _|w ; simp [of_length_zero]
+  have hypos : 0 < y.toNat := toNat_pos_of_ne_zero (by simp [hymsb])
+  have hxnonneg := toInt_nonneg_of_msb_false hxmsb
+  have hynonpos := toInt_neg_of_msb_true hymsb
+  have hylt : (-y).toNat ≤ 2 ^ (w) := toNat_neg_lt_of_msb y hymsb
+  have hmodlt := Nat.mod_lt x.toNat (y := (-y).toNat)
+      (by rw [toNat_neg, Nat.mod_eq_of_lt (by omega)]; omega)
+  simp only [hdvd, reduceIte, toInt_add, hxnonneg, show ¬0 ≤ y.toInt by omega]
+  rw [toInt_umod, toInt_eq_neg_toNat_neg_of_msb_true hymsb, Int.bmod_add_bmod,
+    Int.bmod_eq_of_le (by omega) (by omega),
+    toInt_eq_toNat_of_msb hxmsb, Int.emod_neg]
+
+@[simp]
+theorem toInt_sub_neg_umod {x y : BitVec w} (hxmsb : x.msb = true) (hymsb : y.msb = false) (hdvd : ¬y.toInt ∣ x.toInt) :
+    (y - -x % y).toInt = x.toInt % y.toInt := by
+  rcases w with _|w
+  · simp [of_length_zero]
+  · have : y.toNat < 2 ^ w := toNat_lt_of_msb_false hymsb
+    by_cases hyzero : y = 0#(w+1)
+    · subst hyzero; simp
+    · simp only [toNat_eq, toNat_ofNat, zero_mod] at hyzero
+      have hypos : 0 < y.toNat := by omega
+      simp only [reduceIte, toInt_sub, toInt_eq_toNat_of_msb hymsb, toInt_umod,
+        Int.sub_bmod_bmod, toInt_eq_neg_toNat_neg_of_msb_true hxmsb, Int.neg_emod]
+      have hmodlt := Nat.mod_lt (x := (-x).toNat) (y := y.toNat) hypos
+      rw [Int.bmod_eq_of_le (by omega) (by omega)]
+      simp only [toInt_eq_toNat_of_msb hymsb, BitVec.toInt_eq_neg_toNat_neg_of_msb_true hxmsb,
+        Int.dvd_neg] at hdvd
+      simp only [hdvd, ↓reduceIte, Int.natAbs_cast]
+
+theorem toInt_smod {x y : BitVec w} :
+    (x.smod y).toInt = x.toInt.fmod y.toInt := by
+  rcases w with _|w
+  · decide +revert
+  · by_cases hyzero : y = 0#(w + 1)
+    · simp [hyzero]
+    · rw [smod_eq]
+      cases hxmsb : x.msb <;> cases hymsb : y.msb
+      <;> simp only [umod_eq]
+      · have : 0 < y.toNat := by simp [toNat_eq] at hyzero; omega
+        have : y.toNat < 2 ^ w := toNat_lt_of_msb_false hymsb
+        have : x.toNat % y.toNat < y.toNat := Nat.mod_lt x.toNat (by omega)
+        rw [toInt_umod, Int.fmod_eq_emod_of_nonneg x.toInt (toInt_nonneg_of_msb_false hymsb),
+          toInt_eq_toNat_of_msb hxmsb, toInt_eq_toNat_of_msb hymsb,
+          Int.bmod_eq_of_le_mul_two (by omega) (by omega)]
+      · have := toInt_dvd_toInt_iff_of_msb_false_msb_true hxmsb hymsb
+        by_cases hx_dvd_y : y.toInt ∣ x.toInt
+        · simp [show x % -y = 0#(w + 1) by simp_all, hx_dvd_y, Int.fmod_eq_zero_of_dvd]
+        · have hynonpos := toInt_neg_of_msb_true hymsb
+          simp only [show ¬x % -y = 0#(w + 1) by simp_all, ↓reduceIte,
+            toInt_umod_neg_add hymsb hxmsb hx_dvd_y, Int.fmod_eq_emod, show ¬0 ≤ y.toInt by omega,
+            hx_dvd_y, _root_.or_self]
+      · have hynonneg := toInt_nonneg_of_msb_false hymsb
+        rw [Int.fmod_eq_emod_of_nonneg x.toInt (b := y.toInt) (by omega)]
+        have hdvd := toInt_dvd_toInt_iff_of_msb_true_msb_false hxmsb hymsb
+        by_cases hx_dvd_y : y.toInt ∣ x.toInt
+        · simp [show -x % y = 0#(w + 1) by simp_all, hx_dvd_y, Int.emod_eq_zero_of_dvd]
+        · simp [show ¬-x % y = 0#(w + 1) by simp_all, toInt_sub_neg_umod hxmsb hymsb hx_dvd_y]
+      · rw [←Int.neg_inj, neg_toInt_neg_umod_eq_of_msb_true_msb_true hxmsb hymsb]
+        simp [BitVec.toInt_eq_neg_toNat_neg_of_msb_true, hxmsb, hymsb,
+          Int.fmod_eq_emod_of_nonneg _, show 0 ≤ (-y).toNat by omega]
+
 /-! ### Lemmas that use bit blasting circuits -/
 
 theorem add_sub_comm {x y : BitVec w} : x + y - z = x - z + y := by

src/Init/Data/BitVec/Bootstrap.lean

@@ -0,0 +1,146 @@
+/-
+Copyright (c) 2023 Lean FRO, LLC. All rights reserved.
+Released under Apache 2.0 license as described in the file LICENSE.
+Authors: Joe Hendrix, Harun Khan, Alex Keizer, Abdalrhman M Mohamed, Siddharth Bhat
+-/
+module
+
+prelude
+import all Init.Data.BitVec.Basic
+
+namespace BitVec
+
+theorem testBit_toNat (x : BitVec w) : x.toNat.testBit i = x.getLsbD i := rfl
+
+@[simp] theorem getLsbD_ofFin (x : Fin (2^n)) (i : Nat) :
+    getLsbD (BitVec.ofFin x) i = x.val.testBit i := rfl
+
+@[simp] theorem getLsbD_of_ge (x : BitVec w) (i : Nat) (ge : w ≤ i) : getLsbD x i = false := by
+  let ⟨x, x_lt⟩ := x
+  simp only [getLsbD_ofFin]
+  apply Nat.testBit_lt_two_pow
+  have p : 2^w ≤ 2^i := Nat.pow_le_pow_right (by omega) ge
+  omega
+
+/-- Prove equality of bitvectors in terms of nat operations. -/
+theorem eq_of_toNat_eq {n} : ∀ {x y : BitVec n}, x.toNat = y.toNat → x = y
+  | ⟨_, _⟩, ⟨_, _⟩, rfl => rfl
+
+theorem eq_of_getLsbD_eq {x y : BitVec w}
+    (pred : ∀ i, i < w → x.getLsbD i = y.getLsbD i) : x = y := by
+  apply eq_of_toNat_eq
+  apply Nat.eq_of_testBit_eq
+  intro i
+  if i_lt : i < w then
+    exact pred i i_lt
+  else
+    have p : i ≥ w := Nat.le_of_not_gt i_lt
+    simp [testBit_toNat, getLsbD_of_ge _ _ p]
+
+@[simp, bitvec_to_nat] theorem toNat_ofNat (x w : Nat) : (BitVec.ofNat w x).toNat = x % 2^w := by
+  simp [BitVec.toNat, BitVec.ofNat, Fin.ofNat]
+
+@[ext] theorem eq_of_getElem_eq {x y : BitVec n} :
+        (∀ i (hi : i < n), x[i] = y[i]) → x = y :=
+  fun h => BitVec.eq_of_getLsbD_eq (h ↑·)
+
+@[simp] theorem toNat_append (x : BitVec m) (y : BitVec n) :
+    (x ++ y).toNat = x.toNat <<< n ||| y.toNat :=
+  rfl
+
+@[simp] theorem toNat_ofBool (b : Bool) : (ofBool b).toNat = b.toNat := by
+  cases b <;> rfl
+
+@[simp, bitvec_to_nat] theorem toNat_cast (h : w = v) (x : BitVec w) : (x.cast h).toNat = x.toNat := rfl
+
+@[simp, bitvec_to_nat] theorem toNat_ofFin (x : Fin (2^n)) : (BitVec.ofFin x).toNat = x.val := rfl
+
+@[simp] theorem toNat_ofNatLT (x : Nat) (p : x < 2^w) : (x#'p).toNat = x := rfl
+
+@[simp] theorem toNat_cons (b : Bool) (x : BitVec w) :
+    (cons b x).toNat = (b.toNat <<< w) ||| x.toNat := by
+  let ⟨x, _⟩ := x
+  simp only [cons, toNat_cast, toNat_append, toNat_ofBool, toNat_ofFin]
+
+theorem getElem_cons {b : Bool} {n} {x : BitVec n} {i : Nat} (h : i < n + 1) :
+    (cons b x)[i] = if h : i = n then b else x[i] := by
+  simp only [getElem_eq_testBit_toNat, toNat_cons, Nat.testBit_or, getLsbD]
+  rw [Nat.testBit_shiftLeft]
+  rcases Nat.lt_trichotomy i n with i_lt_n | i_eq_n | n_lt_i
+  · have p1 : ¬(n ≤ i) := by omega
+    have p2 : i ≠ n := by omega
+    simp [p1, p2]
+  · simp only [i_eq_n, ge_iff_le, Nat.le_refl, decide_true, Nat.sub_self, Nat.testBit_zero,
+    Bool.true_and, testBit_toNat, getLsbD_of_ge, Bool.or_false, ↓reduceIte]
+    cases b <;> trivial
+  · have p1 : i ≠ n := by omega
+    have p2 : i - n ≠ 0 := by omega
+    simp [p1, p2, Nat.testBit_bool_to_nat]
+
+private theorem lt_two_pow_of_le {x m n : Nat} (lt : x < 2 ^ m) (le : m ≤ n) : x < 2 ^ n :=
+  Nat.lt_of_lt_of_le lt (Nat.pow_le_pow_right (by trivial : 0 < 2) le)
+
+@[simp, bitvec_to_nat] theorem toNat_setWidth' {m n : Nat} (p : m ≤ n) (x : BitVec m) :
+    (setWidth' p x).toNat = x.toNat := by
+  simp only [setWidth', toNat_ofNatLT]
+
+@[simp, bitvec_to_nat] theorem toNat_setWidth (i : Nat) (x : BitVec n) :
+    BitVec.toNat (setWidth i x) = x.toNat % 2^i := by
+  let ⟨x, lt_n⟩ := x
+  simp only [setWidth]
+  if n_le_i : n ≤ i then
+    have x_lt_two_i : x < 2 ^ i := lt_two_pow_of_le lt_n n_le_i
+    simp [n_le_i, Nat.mod_eq_of_lt, x_lt_two_i]
+  else
+    simp [n_le_i, toNat_ofNat]
+
+@[simp] theorem ofNat_toNat (m : Nat) (x : BitVec n) : BitVec.ofNat m x.toNat = setWidth m x := by
+  apply eq_of_toNat_eq
+  simp only [toNat_ofNat, toNat_setWidth]
+
+theorem getElem_setWidth' (x : BitVec w) (i : Nat) (h : w ≤ v) (hi : i < v) :
+    (setWidth' h x)[i] = x.getLsbD i := by
+  rw [getElem_eq_testBit_toNat, toNat_setWidth', getLsbD]
+
+@[simp]
+theorem getElem_setWidth (m : Nat) (x : BitVec n) (i : Nat) (h : i < m) :
+    (setWidth m x)[i] = x.getLsbD i := by
+  rw [setWidth]
+  split
+  · rw [getElem_setWidth']
+  · simp only [ofNat_toNat, getElem_eq_testBit_toNat, toNat_setWidth, Nat.testBit_mod_two_pow,
+      getLsbD, Bool.and_eq_right_iff_imp, decide_eq_true_eq]
+    omega
+
+@[simp] theorem cons_msb_setWidth (x : BitVec (w+1)) : (cons x.msb (x.setWidth w)) = x := by
+  ext i
+  simp only [getElem_cons]
+  split <;> rename_i h
+  · simp [BitVec.msb, getMsbD, h]
+  · by_cases h' : i < w
+    · simp_all only [getElem_setWidth, getLsbD_eq_getElem]
+    · omega
+
+@[simp, bitvec_to_nat] theorem toNat_neg (x : BitVec n) : (- x).toNat = (2^n - x.toNat) % 2^n := by
+  simp [Neg.neg, BitVec.neg]
+
+@[simp] theorem setWidth_neg_of_le {x : BitVec v} (h : w ≤ v) : BitVec.setWidth w (-x) = -BitVec.setWidth w x := by
+  apply BitVec.eq_of_toNat_eq
+  simp only [toNat_setWidth, toNat_neg]
+  rw [Nat.mod_mod_of_dvd _ (Nat.pow_dvd_pow 2 h)]
+  rw [Nat.mod_eq_mod_iff]
+  rw [Nat.mod_def]
+  refine ⟨1 + x.toNat / 2^w, 2^(v-w), ?_⟩
+  rw [← Nat.pow_add]
+  have : v - w + w = v := by omega
+  rw [this]
+  rw [Nat.add_mul, Nat.one_mul, Nat.mul_comm (2^w)]
+  have sub_sub : ∀ (a : Nat) {b c : Nat} (h : c ≤ b), a - (b - c) = a + c - b := by omega
+  rw [sub_sub _ (Nat.div_mul_le_self x.toNat (2 ^ w))]
+  have : x.toNat / 2 ^ w * 2 ^ w ≤ x.toNat := Nat.div_mul_le_self x.toNat (2 ^ w)
+  have : x.toNat < 2 ^w ∨ x.toNat - 2 ^ w < x.toNat / 2 ^ w * 2 ^ w := by
+    have := Nat.lt_div_mul_add (a := x.toNat) (b := 2 ^ w) (Nat.two_pow_pos w)
+    omega
+  omega
+
+end BitVec

src/Init/Data/BitVec/Decidable.lean

@@ -0,0 +1,79 @@
+/-
+Copyright (c) 2023 Lean FRO, LLC. All rights reserved.
+Released under Apache 2.0 license as described in the file LICENSE.
+Authors: Joe Hendrix, Harun Khan, Alex Keizer, Abdalrhman M Mohamed, Siddharth Bhat
+
+-/
+module
+
+prelude
+import Init.Data.BitVec.Bootstrap
+
+set_option linter.missingDocs true
+
+namespace BitVec
+
+/-! ### Decidable quantifiers -/
+
+theorem forall_zero_iff {P : BitVec 0 → Prop} :
+    (∀ v, P v) ↔ P 0#0 := by
+  constructor
+  · intro h
+    apply h
+  · intro h v
+    obtain (rfl : v = 0#0) := (by ext i ⟨⟩)
+    apply h
+
+theorem forall_cons_iff {P : BitVec (n + 1) → Prop} :
+    (∀ v : BitVec (n + 1), P v) ↔ (∀ (x : Bool) (v : BitVec n), P (v.cons x)) := by
+  constructor
+  · intro h _ _
+    apply h
+  · intro h v
+    have w : v = (v.setWidth n).cons v.msb := by simp only [cons_msb_setWidth]
+    rw [w]
+    apply h
+
+instance instDecidableForallBitVecZero (P : BitVec 0 → Prop) :
+    ∀ [Decidable (P 0#0)], Decidable (∀ v, P v)
+  | .isTrue h => .isTrue fun v => by
+    obtain (rfl : v = 0#0) := (by ext i ⟨⟩)
+    exact h
+  | .isFalse h => .isFalse (fun w => h (w _))
+
+instance instDecidableForallBitVecSucc (P : BitVec (n+1) → Prop) [DecidablePred P]
+    [Decidable (∀ (x : Bool) (v : BitVec n), P (v.cons x))] : Decidable (∀ v, P v) :=
+  decidable_of_iff' (∀ x (v : BitVec n), P (v.cons x)) forall_cons_iff
+
+instance instDecidableExistsBitVecZero (P : BitVec 0 → Prop) [Decidable (P 0#0)] :
+    Decidable (∃ v, P v) :=
+  decidable_of_iff (¬ ∀ v, ¬ P v) Classical.not_forall_not
+
+instance instDecidableExistsBitVecSucc (P : BitVec (n+1) → Prop) [DecidablePred P]
+    [Decidable (∀ (x : Bool) (v : BitVec n), ¬ P (v.cons x))] : Decidable (∃ v, P v) :=
+  decidable_of_iff (¬ ∀ v, ¬ P v) Classical.not_forall_not
+
+/--
+For small numerals this isn't necessary (as typeclass search can use the above two instances),
+but for large numerals this provides a shortcut.
+Note, however, that for large numerals the decision procedure may be very slow,
+and you should use `bv_decide` if possible.
+-/
+instance instDecidableForallBitVec :
+    ∀ (n : Nat) (P : BitVec n → Prop) [DecidablePred P], Decidable (∀ v, P v)
+  | 0, _, _ => inferInstance
+  | n + 1, _, _ =>
+    have := instDecidableForallBitVec n
+    inferInstance
+
+/--
+For small numerals this isn't necessary (as typeclass search can use the above two instances),
+but for large numerals this provides a shortcut.
+Note, however, that for large numerals the decision procedure may be very slow.
+-/
+instance instDecidableExistsBitVec :
+    ∀ (n : Nat) (P : BitVec n → Prop) [DecidablePred P], Decidable (∃ v, P v)
+  | 0, _, _ => inferInstance
+  | _ + 1, _, _ => inferInstance
+
+end BitVec

src/Init/Data/BitVec/Lemmas.lean

@@ -2,7 +2,6 @@
 Copyright (c) 2023 Lean FRO, LLC. All rights reserved.
 Released under Apache 2.0 license as described in the file LICENSE.
 Authors: Joe Hendrix, Harun Khan, Alex Keizer, Abdalrhman M Mohamed, Siddharth Bhat
-
 -/
 module
 
@@ -19,6 +18,7 @@ import Init.Data.Int.Bitwise.Lemmas
 import Init.Data.Int.LemmasAux
 import Init.Data.Int.Pow
 import Init.Data.Int.LemmasAux
+import Init.Data.BitVec.Bootstrap
 
 set_option linter.missingDocs true
 
@@ -27,19 +27,9 @@ namespace BitVec
 @[simp] theorem mk_zero : BitVec.ofFin (w := w) ⟨0, h⟩ = 0#w := rfl
 @[simp] theorem ofNatLT_zero : BitVec.ofNatLT (w := w) 0 h = 0#w := rfl
 
-@[simp] theorem getLsbD_ofFin (x : Fin (2^n)) (i : Nat) :
-    getLsbD (BitVec.ofFin x) i = x.val.testBit i := rfl
-
 @[simp] theorem getElem_ofFin (x : Fin (2^n)) (i : Nat) (h : i < n) :
     (BitVec.ofFin x)[i] = x.val.testBit i := rfl
 
-@[simp] theorem getLsbD_of_ge (x : BitVec w) (i : Nat) (ge : w ≤ i) : getLsbD x i = false := by
-  let ⟨x, x_lt⟩ := x
-  simp only [getLsbD_ofFin]
-  apply Nat.testBit_lt_two_pow
-  have p : 2^w ≤ 2^i := Nat.pow_le_pow_right (by omega) ge
-  omega
-
 @[simp] theorem getMsbD_of_ge (x : BitVec w) (i : Nat) (ge : w ≤ i) : getMsbD x i = false := by
   rw [getMsbD]
   simp only [Bool.and_eq_false_imp, decide_eq_true_eq]
@@ -68,11 +58,11 @@ theorem lt_of_getMsbD {x : BitVec w} {i : Nat} : getMsbD x i = true → i < w :=
 @[simp] theorem getElem?_eq_getElem {l : BitVec w} {n} (h : n < w) : l[n]? = some l[n] := by
   simp only [getElem?_def, h, ↓reduceDIte]
 
-theorem getElem?_eq_some_iff {l : BitVec w} : l[n]? = some a ↔ ∃ h : n < w, l[n] = a := by
-  simp only [getElem?_def]
-  split
-  · simp_all
-  · simp; omega
+theorem getElem?_eq_some_iff {l : BitVec w} : l[n]? = some a ↔ ∃ h : n < w, l[n] = a :=
+  _root_.getElem?_eq_some_iff
+
+theorem some_eq_getElem?_iff {l : BitVec w} : some a = l[n]? ↔ ∃ h : n < w, l[n] = a :=
+  _root_.some_eq_getElem?_iff
 
 theorem getElem_of_getElem? {l : BitVec w} : l[n]? = some a → ∃ h : n < w, l[n] = a :=
   getElem?_eq_some_iff.mp
@@ -81,11 +71,11 @@ set_option linter.missingDocs false in
 @[deprecated getElem?_eq_some_iff (since := "2025-02-17")]
 abbrev getElem?_eq_some := @getElem?_eq_some_iff
 
-@[simp] theorem getElem?_eq_none_iff {l : BitVec w} : l[n]? = none ↔ w ≤ n := by
-  simp only [getElem?_def]
-  split
-  · simp_all
-  · simp; omega
+theorem getElem?_eq_none_iff {l : BitVec w} : l[n]? = none ↔ w ≤ n := by
+  simp
+
+theorem none_eq_getElem?_iff {l : BitVec w} : none = l[n]? ↔ w ≤ n := by
+  simp
 
 theorem getElem?_eq_none {l : BitVec w} (h : w ≤ n) : l[n]? = none := getElem?_eq_none_iff.mpr h
 
@@ -93,13 +83,13 @@ theorem getElem?_eq (l : BitVec w) (i : Nat) :
     l[i]? = if h : i < w then some l[i] else none := by
   split <;> simp_all
 
-@[simp] theorem some_getElem_eq_getElem? (l : BitVec w) (i : Nat) (h : i < w) :
+theorem some_getElem_eq_getElem? (l : BitVec w) (i : Nat) (h : i < w) :
     (some l[i] = l[i]?) ↔ True := by
-  simp [h]
+  simp
 
-@[simp] theorem getElem?_eq_some_getElem (l : BitVec w) (i : Nat) (h : i < w) :
+theorem getElem?_eq_some_getElem (l : BitVec w) (i : Nat) (h : i < w) :
     (l[i]? = some l[i]) ↔ True := by
-  simp [h]
+  simp
 
 theorem getElem_eq_iff {l : BitVec w} {n : Nat} {h : n < w} : l[n] = x ↔ l[n]? = some x := by
   simp only [getElem?_eq_some_iff]
@@ -125,11 +115,7 @@ theorem getElem_of_getLsbD_eq_true {x : BitVec w} {i : Nat} (h : x.getLsbD i = t
 This normalized a bitvec using `ofFin` to `ofNat`.
 -/
 theorem ofFin_eq_ofNat : @BitVec.ofFin w (Fin.mk x lt) = BitVec.ofNat w x := by
-  simp only [BitVec.ofNat, Fin.ofNat', lt, Nat.mod_eq_of_lt]
-
-/-- Prove equality of bitvectors in terms of nat operations. -/
-theorem eq_of_toNat_eq {n} : ∀ {x y : BitVec n}, x.toNat = y.toNat → x = y
-  | ⟨_, _⟩, ⟨_, _⟩, rfl => rfl
+  simp only [BitVec.ofNat, Fin.ofNat, lt, Nat.mod_eq_of_lt]
 
 /-- Prove nonequality of bitvectors in terms of nat operations. -/
 theorem toNat_ne_iff_ne {n} {x y : BitVec n} : x.toNat ≠ y.toNat ↔ x ≠ y := by
@@ -153,26 +139,28 @@ protected theorem toNat_lt_twoPow_of_le (h : m ≤ n) {x : BitVec m} :
   apply Nat.pow_le_pow_of_le
   <;> omega
 
-theorem testBit_toNat (x : BitVec w) : x.toNat.testBit i = x.getLsbD i := rfl
-
 theorem two_pow_le_toNat_of_getElem_eq_true {i : Nat} {x : BitVec w}
     (hi : i < w) (hx : x[i] = true) : 2^i ≤ x.toNat := by
   apply Nat.ge_two_pow_of_testBit
   rw [← getElem_eq_testBit_toNat x i hi]
   exact hx
 
-theorem getMsb'_eq_getLsb' (x : BitVec w) (i : Fin w) :
-    x.getMsb' i = x.getLsb' ⟨w - 1 - i, by omega⟩ := by
-  simp only [getMsb', getLsb']
+theorem getMsb_eq_getLsb (x : BitVec w) (i : Fin w) :
+    x.getMsb i = x.getLsb ⟨w - 1 - i, by omega⟩ := by
+  simp only [getMsb, getLsb]
 
 theorem getMsb?_eq_getLsb? (x : BitVec w) (i : Nat) :
     x.getMsb? i = if i < w then x.getLsb? (w - 1 - i) else none := by
   simp only [getMsb?, getLsb?_eq_getElem?]
-  split <;> simp [getMsb'_eq_getLsb']
+  split <;> simp [getMsb_eq_getLsb]
 
 theorem getMsbD_eq_getLsbD (x : BitVec w) (i : Nat) : x.getMsbD i = (decide (i < w) && x.getLsbD (w - 1 - i)) := by
   rw [getMsbD, getLsbD]
 
+@[deprecated getMsb_eq_getLsb (since := "2025-06-17")]
+theorem getMsb'_eq_getLsb' (x : BitVec w) (i : Nat) : x.getMsbD i = (decide (i < w) && x.getLsbD (w - 1 - i)) := by
+  rw [getMsbD, getLsbD]
+
 theorem getLsbD_eq_getMsbD (x : BitVec w) (i : Nat) : x.getLsbD i = (decide (i < w) && x.getMsbD (w - 1 - i)) := by
   rw [getMsbD]
   by_cases h₁ : i < w <;> by_cases h₂ : w - 1 - i < w <;>
@@ -241,21 +229,6 @@ theorem getMsbD_eq_getMsb?_getD (x : BitVec w) (i : Nat) :
       intros
       omega
 
-theorem eq_of_getLsbD_eq {x y : BitVec w}
-    (pred : ∀ i, i < w → x.getLsbD i = y.getLsbD i) : x = y := by
-  apply eq_of_toNat_eq
-  apply Nat.eq_of_testBit_eq
-  intro i
-  if i_lt : i < w then
-    exact pred i i_lt
-  else
-    have p : i ≥ w := Nat.le_of_not_gt i_lt
-    simp [testBit_toNat, getLsbD_of_ge _ _ p]
-
-@[ext] theorem eq_of_getElem_eq {x y : BitVec n} :
-        (∀ i (hi : i < n), x[i] = y[i]) → x = y :=
-  fun h => BitVec.eq_of_getLsbD_eq (h ↑·)
-
 theorem eq_of_getLsbD_eq_iff {w : Nat} {x y : BitVec w} :
     x = y ↔ ∀ (i : Nat), i < w → x.getLsbD i = y.getLsbD i := by
   have iff := @BitVec.eq_of_getElem_eq_iff w x y
@@ -314,11 +287,12 @@ theorem length_pos_of_ne {x y : BitVec w} (h : x ≠ y) : 0 < w :=
 
 theorem ofFin_ofNat (n : Nat) :
     ofFin (no_index (OfNat.ofNat n : Fin (2^w))) = OfNat.ofNat n := by
-  simp only [OfNat.ofNat, Fin.ofNat', BitVec.ofNat, Nat.and_two_pow_sub_one_eq_mod]
+  simp only [OfNat.ofNat, Fin.ofNat, BitVec.ofNat, Nat.and_two_pow_sub_one_eq_mod]
 
 @[simp] theorem ofFin_neg {x : Fin (2 ^ w)} : ofFin (-x) = -(ofFin x) := by
   rfl
 
+open Fin.NatCast in
 @[simp, norm_cast] theorem ofFin_natCast (n : Nat) : ofFin (n : Fin (2^w)) = (n : BitVec w) := by
   rfl
 
@@ -337,20 +311,18 @@ theorem toFin_zero : toFin (0 : BitVec w) = 0 := rfl
 theorem toFin_one  : toFin (1 : BitVec w) = 1 := by
   rw [toFin_inj]; simp only [ofNat_eq_ofNat, ofFin_ofNat]
 
+open Fin.NatCast in
 @[simp, norm_cast] theorem toFin_natCast (n : Nat) : toFin (n : BitVec w) = (n : Fin (2^w)) := by
   rfl
 
-@[simp] theorem toNat_ofBool (b : Bool) : (ofBool b).toNat = b.toNat := by
-  cases b <;> rfl
-
 @[simp] theorem toInt_ofBool (b : Bool) : (ofBool b).toInt = -b.toInt := by
   cases b <;> simp
 
-@[simp] theorem toFin_ofBool (b : Bool) : (ofBool b).toFin = Fin.ofNat' 2 (b.toNat) := by
+@[simp] theorem toFin_ofBool (b : Bool) : (ofBool b).toFin = Fin.ofNat 2 (b.toNat) := by
   cases b <;> rfl
 
 theorem ofNat_one (n : Nat) : BitVec.ofNat 1 n = BitVec.ofBool (n % 2 = 1) :=  by
-  rcases (Nat.mod_two_eq_zero_or_one n) with h | h <;> simp [h, BitVec.ofNat, Fin.ofNat']
+  rcases (Nat.mod_two_eq_zero_or_one n) with h | h <;> simp [h, BitVec.ofNat, Fin.ofNat]
 
 theorem ofBool_eq_iff_eq : ∀ {b b' : Bool}, BitVec.ofBool b = BitVec.ofBool b' ↔ b = b' := by
   decide
@@ -366,10 +338,6 @@ theorem ofBool_eq_iff_eq : ∀ {b b' : Bool}, BitVec.ofBool b = BitVec.ofBool b'
 @[simp] theorem ofBool_xor_ofBool : ofBool b ^^^ ofBool b' = ofBool (b ^^ b') := by
   cases b <;> cases b' <;> rfl
 
-@[simp, bitvec_to_nat] theorem toNat_ofFin (x : Fin (2^n)) : (BitVec.ofFin x).toNat = x.val := rfl
-
-@[simp] theorem toNat_ofNatLT (x : Nat) (p : x < 2^w) : (x#'p).toNat = x := rfl
-
 @[deprecated toNat_ofNatLT (since := "2025-02-13")]
 theorem toNat_ofNatLt (x : Nat) (p : x < 2^w) : (x#'p).toNat = x := rfl
 
@@ -389,13 +357,10 @@ theorem getLsbD_ofNatLt {n : Nat} (x : Nat) (lt : x < 2^n) (i : Nat) :
 theorem getMsbD_ofNatLt {n x i : Nat} (h : x < 2^n) :
     getMsbD (x#'h) i = (decide (i < n) && x.testBit (n - 1 - i)) := getMsbD_ofNatLT h
 
-@[simp, bitvec_to_nat] theorem toNat_ofNat (x w : Nat) : (BitVec.ofNat w x).toNat = x % 2^w := by
-  simp [BitVec.toNat, BitVec.ofNat, Fin.ofNat']
-
 theorem ofNatLT_eq_ofNat {w : Nat} {n : Nat} (hn) : BitVec.ofNatLT n hn = BitVec.ofNat w n :=
   eq_of_toNat_eq (by simp [Nat.mod_eq_of_lt hn])
 
-@[simp] theorem toFin_ofNat (x : Nat) : toFin (BitVec.ofNat w x) = Fin.ofNat' (2^w) x := rfl
+@[simp] theorem toFin_ofNat (x : Nat) : toFin (BitVec.ofNat w x) = Fin.ofNat (2^w) x := rfl
 
 @[simp] theorem finMk_toNat (x : BitVec w) : Fin.mk x.toNat x.isLt = x.toFin := rfl
 
@@ -415,7 +380,7 @@ theorem ofNatLT_eq_ofNat {w : Nat} {n : Nat} (hn) : BitVec.ofNatLT n hn = BitVec
 -- If `x` and `n` are not literals, applying this theorem eagerly may not be a good idea.
 theorem getLsbD_ofNat (n : Nat) (x : Nat) (i : Nat) :
   getLsbD (BitVec.ofNat n x) i = (i < n && x.testBit i) := by
-  simp [getLsbD, BitVec.ofNat, Fin.val_ofNat']
+  simp [getLsbD, BitVec.ofNat, Fin.val_ofNat]
 
 @[simp] theorem getLsbD_zero : (0#w).getLsbD i = false := by simp [getLsbD]
 
@@ -505,7 +470,7 @@ theorem getLsbD_ofBool (b : Bool) (i : Nat) : (ofBool b).getLsbD i = ((i = 0) &&
   · simp only [ofBool, ofNat_eq_ofNat, cond_true, getLsbD_ofNat, Bool.and_true]
     by_cases hi : i = 0 <;> simp [hi] <;> omega
 
-@[simp] theorem getElem_ofBool_zero {b : Bool} : (ofBool b)[0] = b := by simp
+theorem getElem_ofBool_zero {b : Bool} : (ofBool b)[0] = b := by simp
 
 @[simp]
 theorem getElem_ofBool {b : Bool} {h : i < 1}: (ofBool b)[i] = b := by
@@ -579,7 +544,6 @@ theorem msb_eq_getMsbD_zero (x : BitVec w) : x.msb = x.getMsbD 0 := by
 
 /-! ### cast -/
 
-@[simp, bitvec_to_nat] theorem toNat_cast (h : w = v) (x : BitVec w) : (x.cast h).toNat = x.toNat := rfl
 @[simp] theorem toFin_cast (h : w = v) (x : BitVec w) :
     (x.cast h).toFin = x.toFin.cast (by rw [h]) :=
   rfl
@@ -880,6 +844,19 @@ theorem slt_eq_sle_and_ne {x y : BitVec w} : x.slt y = (x.sle y && x != y) := by
   apply Bool.eq_iff_iff.2
   simp [BitVec.slt, BitVec.sle, Int.lt_iff_le_and_ne, BitVec.toInt_inj]
 
+/-- For all bitvectors `x, y`, either `x` is signed less than `y`,
+or is equal to `y`, or is signed greater than `y`. -/
+theorem slt_trichotomy (x y : BitVec w) : x.slt y ∨ x = y ∨ y.slt x := by
+  simpa [slt_iff_toInt_lt, ← toInt_inj]
+    using Int.lt_trichotomy x.toInt y.toInt
+
+/-- For all bitvectors `x, y`, either `x` is unsigned less than `y`,
+or is equal to `y`, or is unsigned greater than `y`. -/
+theorem lt_trichotomy (x y : BitVec w) :
+    x < y ∨ x = y ∨ y < x := by
+  simpa [← ult_iff_lt, ult_eq_decide, decide_eq_true_eq, ← toNat_inj]
+    using Nat.lt_trichotomy x.toNat y.toNat
+
 /-! ### setWidth, zeroExtend and truncate -/
 
 @[simp]
@@ -890,26 +867,12 @@ theorem truncate_eq_setWidth {v : Nat} {x : BitVec w} :
 theorem zeroExtend_eq_setWidth {v : Nat} {x : BitVec w} :
   zeroExtend v x = setWidth v x := rfl
 
-@[simp, bitvec_to_nat] theorem toNat_setWidth' {m n : Nat} (p : m ≤ n) (x : BitVec m) :
-    (setWidth' p x).toNat = x.toNat := by
-  simp [setWidth']
-
-@[simp, bitvec_to_nat] theorem toNat_setWidth (i : Nat) (x : BitVec n) :
-    BitVec.toNat (setWidth i x) = x.toNat % 2^i := by
-  let ⟨x, lt_n⟩ := x
-  simp only [setWidth]
-  if n_le_i : n ≤ i then
-    have x_lt_two_i : x < 2 ^ i := lt_two_pow_of_le lt_n n_le_i
-    simp [n_le_i, Nat.mod_eq_of_lt, x_lt_two_i]
-  else
-    simp [n_le_i, toNat_ofNat]
-
 @[simp] theorem toInt_setWidth (x : BitVec w) :
     (x.setWidth v).toInt = Int.bmod x.toNat (2^v) := by
   simp [toInt_eq_toNat_bmod, toNat_setWidth, Int.emod_bmod, -Int.natCast_pow]
 
 @[simp] theorem toFin_setWidth {x : BitVec w} :
-    (x.setWidth v).toFin = Fin.ofNat' (2^v) x.toNat := by
+    (x.setWidth v).toFin = Fin.ofNat (2^v) x.toNat := by
   ext; simp
 
 @[simp] theorem setWidth_eq (x : BitVec n) : setWidth n x = x := by
@@ -921,10 +884,6 @@ theorem zeroExtend_eq_setWidth {v : Nat} {x : BitVec w} :
   apply eq_of_toNat_eq
   simp [toNat_setWidth]
 
-@[simp] theorem ofNat_toNat (m : Nat) (x : BitVec n) : BitVec.ofNat m x.toNat = setWidth m x := by
-  apply eq_of_toNat_eq
-  simp
-
 /-- Moves one-sided left toNat equality to BitVec equality. -/
 theorem toNat_eq_nat {x : BitVec w} {y : Nat}
   : (x.toNat = y) ↔ (y < 2^w ∧ (x = BitVec.ofNat w y)) := by
@@ -940,19 +899,6 @@ theorem nat_eq_toNat {x : BitVec w} {y : Nat}
   rw [@eq_comm _ _ x.toNat]
   apply toNat_eq_nat
 
-theorem getElem_setWidth' (x : BitVec w) (i : Nat) (h : w ≤ v) (hi : i < v) :
-    (setWidth' h x)[i] = x.getLsbD i := by
-  rw [getElem_eq_testBit_toNat, toNat_setWidth', getLsbD]
-
-@[simp]
-theorem getElem_setWidth (m : Nat) (x : BitVec n) (i : Nat) (h : i < m) :
-    (setWidth m x)[i] = x.getLsbD i := by
-  rw [setWidth]
-  split
-  · rw [getElem_setWidth']
-  · simp [getElem_eq_testBit_toNat, getLsbD]
-    omega
-
 theorem getElem?_setWidth' (x : BitVec w) (i : Nat) (h : w ≤ v) :
     (setWidth' h x)[i]? = if i < v then some (x.getLsbD i) else none := by
   simp [getElem?_eq, getElem_setWidth']
@@ -1105,7 +1051,7 @@ theorem toInt_setWidth' {m n : Nat} (p : m ≤ n) {x : BitVec m} :
 @[simp] theorem toFin_setWidth' {m n : Nat} (p : m ≤ n) (x : BitVec m) :
     (setWidth' p x).toFin = x.toFin.castLE (Nat.pow_le_pow_right (by omega) (by omega)) := by
   ext
-  rw [setWidth'_eq, toFin_setWidth, Fin.val_ofNat', Fin.coe_castLE, val_toFin,
+  rw [setWidth'_eq, toFin_setWidth, Fin.val_ofNat, Fin.coe_castLE, val_toFin,
     Nat.mod_eq_of_lt (by apply BitVec.toNat_lt_twoPow_of_le p)]
 
 /-! ## extractLsb -/
@@ -1135,11 +1081,11 @@ protected theorem extractLsb_ofNat (x n : Nat) (hi lo : Nat) :
   simp [extractLsb, toInt_ofNat]
 
 @[simp] theorem toFin_extractLsb' {s m : Nat} {x : BitVec n} :
-    (extractLsb' s m x).toFin = Fin.ofNat' (2 ^ m) (x.toNat >>> s) := by
+    (extractLsb' s m x).toFin = Fin.ofNat (2 ^ m) (x.toNat >>> s) := by
   simp [extractLsb', toInt_ofNat]
 
 @[simp] theorem toFin_extractLsb {hi lo : Nat} {x : BitVec n} :
-  (extractLsb hi lo x).toFin = Fin.ofNat' (2 ^ (hi - lo + 1)) (x.toNat >>> lo) := by
+  (extractLsb hi lo x).toFin = Fin.ofNat (2 ^ (hi - lo + 1)) (x.toNat >>> lo) := by
   simp [extractLsb, toInt_ofNat]
 
 @[simp] theorem getElem_extractLsb' {start len : Nat} {x : BitVec n} {i : Nat} (h : i < len) :
@@ -1310,7 +1256,7 @@ theorem extractLsb'_eq_zero {x : BitVec w} {start : Nat} :
     simp [BitVec.toInt, -Int.natCast_pow]
     omega
 
-@[simp] theorem toFin_allOnes : (allOnes w).toFin = Fin.ofNat' (2^w) (2^w - 1) := by
+@[simp] theorem toFin_allOnes : (allOnes w).toFin = Fin.ofNat (2^w) (2^w - 1) := by
   ext
   simp
 
@@ -1847,7 +1793,7 @@ theorem not_xor_right {x y : BitVec w} : ~~~ (x ^^^ y) = x ^^^ ~~~ y := by
   simp [-Int.natCast_pow]
 
 @[simp] theorem toFin_shiftLeft {n : Nat} (x : BitVec w) :
-    (x <<< n).toFin = Fin.ofNat' (2^w) (x.toNat <<< n) := rfl
+    (x <<< n).toFin = Fin.ofNat (2^w) (x.toNat <<< n) := rfl
 
 @[simp]
 theorem shiftLeft_zero (x : BitVec w) : x <<< 0 = x := by
@@ -1917,6 +1863,63 @@ theorem shiftLeftZeroExtend_eq {x : BitVec w} :
     exact Nat.mul_lt_mul_of_pos_right x.isLt (Nat.two_pow_pos _)
   · omega
 
+@[simp]
+theorem toNat_shiftLeftZeroExtend {x : BitVec w} :
+    (shiftLeftZeroExtend x n).toNat = x.toNat <<< n := by
+  rcases n with _|n
+  · simp [shiftLeftZeroExtend]
+  · simp only [shiftLeftZeroExtend_eq, toNat_shiftLeft, toNat_setWidth]
+    have :=  Nat.pow_lt_pow_of_lt (a := 2) (n := w) (m := w + (n + 1)) (by omega) (by omega)
+    have : x.toNat <<< (n + 1) < 2 ^ (w + (n + 1)) := by
+      rw [Nat.shiftLeft_eq, Nat.pow_add (m := w) (n := n + 1), Nat.mul_lt_mul_right (by apply Nat.two_pow_pos (w := n + 1))]
+      omega
+    rw [Nat.mod_eq_of_lt (by rw [Nat.mod_eq_of_lt (by omega)]; omega), Nat.mod_eq_of_lt (by omega)]
+
+@[simp]
+theorem toInt_shiftLeftZeroExtend {x : BitVec w} :
+    (shiftLeftZeroExtend x n).toInt = x.toInt * 2 ^ n := by
+  rw [shiftLeftZeroExtend_eq]
+  rcases w with _|w
+  · simp [of_length_zero, shiftLeftZeroExtend_eq]
+  · rcases n with _|n
+    · simp [shiftLeftZeroExtend_eq]
+    · have := Nat.pow_pos (a := 2) (n := n + 1) (by omega)
+      have : x.toNat <<< (n + 1) < 2 ^ (w + 1 + (n + 1)) := by
+        rw [Nat.shiftLeft_eq, Nat.pow_add (a := 2) (m := w + 1) (n := n + 1), Nat.mul_lt_mul_right (by omega)]
+        omega
+      simp only [shiftLeftZeroExtend_eq, toInt_shiftLeft, toNat_setWidth, Nat.lt_add_right_iff_pos,
+        Nat.zero_lt_succ, toNat_mod_cancel_of_lt, Int.bmod_def]
+      by_cases hmsb : x.msb
+      · have hge := toNat_ge_of_msb_true hmsb
+        simp only [Nat.add_one_sub_one, ge_iff_le] at hge
+        rw [Int.emod_eq_of_lt (by norm_cast; rw [Nat.shiftLeft_eq]; omega) (by omega)]
+        rw_mod_cast [← Nat.add_assoc]
+        rw [show (2 ^ (w + 1 + n + 1) + 1) / 2 = 2 ^ (w + 1 + n) by omega, Int.natCast_pow,
+          Int.cast_ofNat_Int, Nat.shiftLeft_eq, Nat.add_assoc, Nat.pow_add (a := 2) (m := w) (n := 1 + n),
+          Nat.add_comm 1 n]
+        simp only [Nat.mul_lt_mul_right (by omega), show ¬x.toNat < 2 ^ w by omega, reduceIte,
+          Int.natCast_mul, Int.natCast_pow, Int.cast_ofNat_Int, toInt_eq_toNat_cond,
+          show ¬2 * x.toNat < 2 ^ (w + 1) by simp [Nat.pow_add, Nat.mul_comm (2 ^ w) 2, hge]]
+        norm_cast
+        simp [Int.natCast_mul, Int.natCast_pow, Int.cast_ofNat_Int, Int.sub_mul,
+          Int.sub_right_inj, show w + (n + 1) + 1 = (w + 1) + (n + 1) by omega, Nat.pow_add]
+      · simp only [Bool.not_eq_true] at hmsb
+        have hle := toNat_lt_of_msb_false (x := x) hmsb
+        simp only [Nat.add_one_sub_one] at hle
+        rw [Int.emod_eq_of_lt (by norm_cast; rw [Nat.shiftLeft_eq]; omega) (by omega)]
+        rw_mod_cast [← Nat.add_assoc]
+        rw [show (2 ^ (w + 1 + n + 1) + 1) / 2 = 2 ^ (w + 1 + n) by omega, Int.natCast_pow,
+          Int.cast_ofNat_Int, Nat.shiftLeft_eq, Nat.add_assoc,  Nat.pow_add (a := 2) (m := w) (n := 1 + n), Nat.add_comm 1 n]
+        simp [Nat.mul_lt_mul_right (b := x.toNat) (c := 2 ^ w) (a := 2 ^ (n + 1)) (by omega), hle,
+          reduceIte, Int.natCast_mul, Int.natCast_pow, Int.cast_ofNat_Int, toInt_eq_toNat_of_msb hmsb]
+
+theorem toFin_shiftLeftZeroExtend {x : BitVec w} :
+    (shiftLeftZeroExtend x n).toFin = Fin.ofNat (2 ^ (w + n)) (x.toNat * 2 ^ n) := by
+  rcases w with _|w
+  · simp [of_length_zero, shiftLeftZeroExtend_eq]
+  · have := Nat.pow_le_pow_of_le (a := 2) (n := w + 1) (m := w + 1 + n) (by omega) (by omega)
+    rw [shiftLeftZeroExtend_eq, toFin_shiftLeft, toNat_setWidth, Nat.mod_eq_of_lt (by omega), Nat.shiftLeft_eq]
+
 @[simp] theorem getElem_shiftLeftZeroExtend {x : BitVec m} {n : Nat} (h : i < m + n) :
     (shiftLeftZeroExtend x n)[i] = if h' : i < n then false else x[i - n] := by
   rw [shiftLeftZeroExtend_eq]
@@ -2089,7 +2092,7 @@ theorem toInt_ushiftRight {x : BitVec w} {n : Nat} :
 
 @[simp]
 theorem toFin_ushiftRight {x : BitVec w} {n : Nat} :
-    (x >>> n).toFin = x.toFin / (Fin.ofNat' (2^w) (2^n)) := by
+    (x >>> n).toFin = x.toFin / (Fin.ofNat (2^w) (2^n)) := by
   apply Fin.eq_of_val_eq
   by_cases hn : n < w
   · simp [Nat.shiftRight_eq_div_pow, Nat.mod_eq_of_lt (Nat.pow_lt_pow_of_lt Nat.one_lt_two hn)]
@@ -2340,26 +2343,26 @@ theorem toNat_sshiftRight {x : BitVec w} {n : Nat} :
     simp [toNat_sshiftRight_of_msb_false, h]
 
 theorem toFin_sshiftRight_of_msb_true {x : BitVec w} {n : Nat} (h : x.msb = true) :
-    (x.sshiftRight n).toFin = Fin.ofNat' (2^w) (2 ^ w - 1 - (2 ^ w - 1 - x.toNat) >>> n) := by
+    (x.sshiftRight n).toFin = Fin.ofNat (2^w) (2 ^ w - 1 - (2 ^ w - 1 - x.toNat) >>> n) := by
   apply Fin.eq_of_val_eq
-  simp only [val_toFin, toNat_sshiftRight, h, ↓reduceIte, Fin.val_ofNat']
+  simp only [val_toFin, toNat_sshiftRight, h, ↓reduceIte, Fin.val_ofNat]
   rw [Nat.mod_eq_of_lt]
   have := x.isLt
   have ineq : ∀ y, 2 ^ w - 1 - y < 2 ^ w := by omega
   exact ineq ((2 ^ w - 1 - x.toNat) >>> n)
 
 theorem toFin_sshiftRight_of_msb_false {x : BitVec w} {n : Nat} (h : x.msb = false) :
-    (x.sshiftRight n).toFin = Fin.ofNat' (2^w) (x.toNat >>> n) := by
+    (x.sshiftRight n).toFin = Fin.ofNat (2^w) (x.toNat >>> n) := by
   apply Fin.eq_of_val_eq
-  simp only [val_toFin, toNat_sshiftRight, h, Bool.false_eq_true, ↓reduceIte, Fin.val_ofNat']
+  simp only [val_toFin, toNat_sshiftRight, h, Bool.false_eq_true, ↓reduceIte, Fin.val_ofNat]
   have := Nat.shiftRight_le x.toNat n
   rw [Nat.mod_eq_of_lt (by omega)]
 
 theorem toFin_sshiftRight {x : BitVec w} {n : Nat} :
     (x.sshiftRight n).toFin =
       if x.msb
-      then Fin.ofNat' (2^w) (2 ^ w - 1 - (2 ^ w - 1 - x.toNat) >>> n)
-      else Fin.ofNat' (2^w) (x.toNat >>> n) := by
+      then Fin.ofNat (2^w) (2 ^ w - 1 - (2 ^ w - 1 - x.toNat) >>> n)
+      else Fin.ofNat (2^w) (x.toNat >>> n) := by
   by_cases h : x.msb
   · simp [toFin_sshiftRight_of_msb_true, h]
   · simp [toFin_sshiftRight_of_msb_false, h]
@@ -2397,18 +2400,18 @@ theorem toNat_sshiftRight' {x y : BitVec w} :
   rw [sshiftRight_eq', toNat_sshiftRight]
 
 theorem toFin_sshiftRight'_of_msb_true {x y : BitVec w} (h : x.msb = true) :
-    (x.sshiftRight' y).toFin = Fin.ofNat' (2^w) (2 ^ w - 1 - (2 ^ w - 1 - x.toNat) >>> y.toNat) := by
+    (x.sshiftRight' y).toFin = Fin.ofNat (2^w) (2 ^ w - 1 - (2 ^ w - 1 - x.toNat) >>> y.toNat) := by
   rw [sshiftRight_eq', toFin_sshiftRight_of_msb_true h]
 
 theorem toFin_sshiftRight'_of_msb_false {x y : BitVec w} (h : x.msb = false) :
-    (x.sshiftRight' y).toFin = Fin.ofNat' (2^w) (x.toNat >>> y.toNat) := by
+    (x.sshiftRight' y).toFin = Fin.ofNat (2^w) (x.toNat >>> y.toNat) := by
   rw [sshiftRight_eq', toFin_sshiftRight_of_msb_false h]
 
 theorem toFin_sshiftRight' {x y : BitVec w} :
     (x.sshiftRight' y).toFin =
       if x.msb
-      then Fin.ofNat' (2^w) (2 ^ w - 1 - (2 ^ w - 1 - x.toNat) >>> y.toNat)
-      else Fin.ofNat' (2^w) (x.toNat >>> y.toNat) := by
+      then Fin.ofNat (2^w) (2 ^ w - 1 - (2 ^ w - 1 - x.toNat) >>> y.toNat)
+      else Fin.ofNat (2^w) (x.toNat >>> y.toNat) := by
   rw [sshiftRight_eq', toFin_sshiftRight]
 
 theorem toInt_sshiftRight' {x y : BitVec w} :
@@ -2614,16 +2617,16 @@ theorem toInt_signExtend_eq_toInt_bmod_of_le (x : BitVec w) (h : v ≤ w) :
   rw [BitVec.toInt_signExtend, Nat.min_eq_left h]
 
 theorem toFin_signExtend_of_le {x : BitVec w} (hv : v ≤ w):
-    (x.signExtend v).toFin = Fin.ofNat' (2 ^ v) x.toNat := by
+    (x.signExtend v).toFin = Fin.ofNat (2 ^ v) x.toNat := by
   simp [signExtend_eq_setWidth_of_le _ hv]
 
 theorem toFin_signExtend (x : BitVec w) :
-    (x.signExtend v).toFin = Fin.ofNat' (2 ^ v) (x.toNat + if x.msb = true then 2 ^ v - 2 ^ w else 0):= by
+    (x.signExtend v).toFin = Fin.ofNat (2 ^ v) (x.toNat + if x.msb = true then 2 ^ v - 2 ^ w else 0):= by
   by_cases hv : v ≤ w
   · simp [toFin_signExtend_of_le hv, show 2 ^ v - 2 ^ w = 0 by rw [@Nat.sub_eq_zero_iff_le]; apply Nat.pow_le_pow_of_le (by decide) (by omega)]
   · simp only [Nat.not_le] at hv
     apply Fin.eq_of_val_eq
-    simp only [val_toFin, Fin.val_ofNat']
+    simp only [val_toFin, Fin.val_ofNat]
     rw [toNat_signExtend_of_le _ (by omega)]
     have : 2 ^ w < 2 ^ v := by apply Nat.pow_lt_pow_of_lt <;> omega
     rw [Nat.mod_eq_of_lt]
@@ -2658,10 +2661,6 @@ theorem toFin_signExtend (x : BitVec w) :
 theorem append_def (x : BitVec v) (y : BitVec w) :
     x ++ y = (shiftLeftZeroExtend x w ||| setWidth' (Nat.le_add_left w v) y) := rfl
 
-@[simp] theorem toNat_append (x : BitVec m) (y : BitVec n) :
-    (x ++ y).toNat = x.toNat <<< n ||| y.toNat :=
-  rfl
-
 theorem getLsbD_append {x : BitVec n} {y : BitVec m} :
     getLsbD (x ++ y) i = if i < m then getLsbD y i else getLsbD x (i - m) := by
   simp only [append_def, getLsbD_or, getLsbD_shiftLeftZeroExtend, getLsbD_setWidth']
@@ -2974,7 +2973,7 @@ theorem extractLsb'_append_eq_ite {v w} {xhi : BitVec v} {xlo : BitVec w} {start
     extractLsb' start len (xhi ++ xlo) =
     if hstart : start < w
     then
-      if hlen : start + len < w
+      if hlen : start + len ≤ w
       then extractLsb' start len xlo
       else
         (((extractLsb' (start - w) (len - (w - start)) xhi) ++
@@ -2983,7 +2982,7 @@ theorem extractLsb'_append_eq_ite {v w} {xhi : BitVec v} {xlo : BitVec w} {start
       extractLsb' (start - w) len xhi := by
   by_cases hstart : start < w
   · simp only [hstart, ↓reduceDIte]
-    by_cases hlen : start + len < w
+    by_cases hlen : start + len ≤ w
     · simp only [hlen, ↓reduceDIte]
       ext i hi
       simp only [getElem_extractLsb', getLsbD_append, ite_eq_left_iff, Nat.not_lt]
@@ -3006,11 +3005,14 @@ theorem extractLsb'_append_eq_ite {v w} {xhi : BitVec v} {xlo : BitVec w} {start
 /-- Extracting bits `[start..start+len)` from `(xhi ++ xlo)` equals extracting
 the bits from `xlo` when `start + len` is within `xlo`.
 -/
-theorem extractLsb'_append_eq_of_lt {v w} {xhi : BitVec v} {xlo : BitVec w}
-    {start len : Nat} (h : start + len < w) :
+theorem extractLsb'_append_eq_of_add_le {v w} {xhi : BitVec v} {xlo : BitVec w}
+    {start len : Nat} (h : start + len ≤ w) :
     extractLsb' start len (xhi ++ xlo) = extractLsb' start len xlo := by
-  simp [extractLsb'_append_eq_ite, h]
-  omega
+  simp only [extractLsb'_append_eq_ite, h, ↓reduceDIte, dite_eq_ite, ite_eq_left_iff, Nat.not_lt]
+  intro h'
+  have : len = 0 := by omega
+  subst this
+  simp
 
 /-- Extracting bits `[start..start+len)` from `(xhi ++ xlo)` equals extracting
 the bits from `xhi` when `start` is outside `xlo`.
@@ -3043,11 +3045,6 @@ theorem getMsbD_rev (x : BitVec w) (i : Fin w) :
 
 /-! ### cons -/
 
-@[simp] theorem toNat_cons (b : Bool) (x : BitVec w) :
-    (cons b x).toNat = (b.toNat <<< w) ||| x.toNat := by
-  let ⟨x, _⟩ := x
-  simp [cons, toNat_append, toNat_ofBool]
-
 /-- Variant of `toNat_cons` using `+` instead of `|||`. -/
 theorem toNat_cons' {x : BitVec w} :
     (cons a x).toNat = (a.toNat <<< w) + x.toNat := by
@@ -3067,21 +3064,6 @@ theorem getLsbD_cons (b : Bool) {n} (x : BitVec n) (i : Nat) :
     have p2 : i - n ≠ 0 := by omega
     simp [p1, p2, Nat.testBit_bool_to_nat]
 
-theorem getElem_cons {b : Bool} {n} {x : BitVec n} {i : Nat} (h : i < n + 1) :
-    (cons b x)[i] = if h : i = n then b else x[i] := by
-  simp only [getElem_eq_testBit_toNat, toNat_cons, Nat.testBit_or, getLsbD]
-  rw [Nat.testBit_shiftLeft]
-  rcases Nat.lt_trichotomy i n with i_lt_n | i_eq_n | n_lt_i
-  · have p1 : ¬(n ≤ i) := by omega
-    have p2 : i ≠ n := by omega
-    simp [p1, p2]
-  · simp only [i_eq_n, ge_iff_le, Nat.le_refl, decide_true, Nat.sub_self, Nat.testBit_zero,
-    Bool.true_and, testBit_toNat, getLsbD_of_ge, Bool.or_false, ↓reduceIte]
-    cases b <;> trivial
-  · have p1 : i ≠ n := by omega
-    have p2 : i - n ≠ 0 := by omega
-    simp [p1, p2, Nat.testBit_bool_to_nat]
-
 @[simp] theorem msb_cons : (cons a x).msb = a := by
   simp [cons, msb_cast, msb_append]
 
@@ -3101,15 +3083,6 @@ theorem setWidth_succ (x : BitVec w) :
     have j_lt : j < i := Nat.lt_of_le_of_ne (Nat.le_of_succ_le_succ h) j_eq
     simp [j_eq, j_lt]
 
-@[simp] theorem cons_msb_setWidth (x : BitVec (w+1)) : (cons x.msb (x.setWidth w)) = x := by
-  ext i
-  simp only [getElem_cons]
-  split <;> rename_i h
-  · simp [BitVec.msb, getMsbD, h]
-  · by_cases h' : i < w
-    · simp_all
-    · omega
-
 @[simp] theorem not_cons (x : BitVec w) (b : Bool) : ~~~(cons b x) = cons (!b) (~~~x) := by
   simp [cons]
 
@@ -3179,11 +3152,11 @@ theorem getElem_concat (x : BitVec w) (b : Bool) (i : Nat) (h : i < w + 1) :
   · simp [Nat.mod_eq_of_lt b.toNat_lt]
   · simp [Nat.div_eq_of_lt b.toNat_lt, Nat.testBit_add_one]
 
-@[simp] theorem getLsbD_concat_zero : (concat x b).getLsbD 0 = b := by
+@[simp] theorem getElem_concat_zero {x : BitVec w} : (concat x b)[0] = b := by
   simp [getElem_concat]
 
-@[simp] theorem getElem_concat_zero : (concat x b)[0] = b := by
-  simp [getElem_concat]
+theorem getLsbD_concat_zero : (concat x b).getLsbD 0 = b := by
+  simp
 
 @[simp] theorem getLsbD_concat_succ : (concat x b).getLsbD (i + 1) = x.getLsbD i := by
   simp [getLsbD_concat]
@@ -3323,11 +3296,30 @@ Definition of bitvector addition as a nat.
 
 theorem ofNat_add {n} (x y : Nat) : BitVec.ofNat n (x + y) = BitVec.ofNat n x + BitVec.ofNat n y := by
   apply eq_of_toNat_eq
-  simp [BitVec.ofNat, Fin.ofNat'_add]
+  simp [BitVec.ofNat, Fin.ofNat_add]
 
 theorem ofNat_add_ofNat {n} (x y : Nat) : BitVec.ofNat n x + BitVec.ofNat n y = BitVec.ofNat n (x + y) :=
   (ofNat_add x y).symm
 
+@[simp]
+theorem toNat_add_of_not_uaddOverflow {x y : BitVec w} (h : ¬ uaddOverflow x y) :
+    (x + y).toNat = x.toNat + y.toNat := by
+  rcases w with _|w
+  · simp [of_length_zero]
+  · simp only [uaddOverflow, ge_iff_le, decide_eq_true_eq, Nat.not_le] at h
+    rw [toNat_add, Nat.mod_eq_of_lt h]
+
+/--
+Unsigned addition overflow reassociation.
+If `(x + y)` and `(y + z)` do not overflow, then `(x + y) + z` overflows iff `x + (y + z)` overflows.
+-/
+theorem uaddOverflow_assoc {x y z : BitVec w} (h : ¬ x.uaddOverflow y) (h' : ¬ y.uaddOverflow z) :
+    (x + y).uaddOverflow z = x.uaddOverflow (y + z) := by
+  simp only [uaddOverflow, ge_iff_le, decide_eq_true_eq, Nat.not_le] at h h'
+  simp only [uaddOverflow, toNat_add, ge_iff_le, decide_eq_decide]
+  repeat rw [Nat.mod_eq_of_lt (by omega)]
+  omega
+
 protected theorem add_assoc (x y z : BitVec n) : x + y + z = x + (y + z) := by
   apply eq_of_toNat_eq ; simp [Nat.add_assoc]
 instance : Std.Associative (α := BitVec n) (· + ·) := ⟨BitVec.add_assoc⟩
@@ -3357,6 +3349,29 @@ theorem ofInt_add {n} (x y : Int) : BitVec.ofInt n (x + y) =
   apply eq_of_toInt_eq
   simp
 
+@[simp]
+theorem toInt_add_of_not_saddOverflow {x y : BitVec w} (h : ¬ saddOverflow x y) :
+    (x + y).toInt = x.toInt + y.toInt := by
+  rcases w with _|w
+  · simp [of_length_zero]
+  · simp only [saddOverflow, Nat.add_one_sub_one, ge_iff_le, Bool.or_eq_true, decide_eq_true_eq,
+      _root_.not_or, Int.not_le, Int.not_lt] at h
+    rw [toInt_add, Int.bmod_eq_of_le (by push_cast; omega) (by push_cast; omega)]
+
+/--
+Signed addition overflow reassociation.
+If `(x + y)` and `(y + z)` do not overflow, then `(x + y) + z` overflows iff `x + (y + z)` overflows.
+-/
+theorem saddOverflow_assoc {x y z : BitVec w} (h : ¬ x.saddOverflow y) (h' : ¬ y.saddOverflow z) :
+    (x + y).saddOverflow z = x.saddOverflow (y + z) := by
+  rcases w with _|w
+  · simp [of_length_zero]
+  · simp only [saddOverflow, Nat.add_one_sub_one, ge_iff_le, Bool.or_eq_true, decide_eq_true_eq,
+      _root_.not_or, Int.not_le, Int.not_lt] at h h'
+    simp only [bool_to_prop, saddOverflow, toInt_add, ge_iff_le, Nat.add_one_sub_one]
+    repeat rw [Int.bmod_eq_of_le (by push_cast; omega) (by push_cast; omega)]
+    omega
+
 @[simp]
 theorem shiftLeft_add_distrib {x y : BitVec w} {n : Nat} :
     (x + y) <<< n = x <<< n + y <<< n := by
@@ -3382,6 +3397,24 @@ theorem sub_def {n} (x y : BitVec n) : x - y = .ofNat n ((2^n - y.toNat) + x.toN
     (x - y).toInt = (x.toInt - y.toInt).bmod (2 ^ w) := by
   simp [toInt_eq_toNat_bmod, @Int.ofNat_sub y.toNat (2 ^ w) (by omega), -Int.natCast_pow]
 
+@[simp]
+theorem toNat_sub_of_not_usubOverflow {x y : BitVec w} (h : ¬ usubOverflow x y) :
+    (x - y).toNat = x.toNat - y.toNat := by
+  rcases w with _|w
+  · simp [of_length_zero]
+  · simp only [usubOverflow, decide_eq_true_eq, Nat.not_lt] at h
+    rw [toNat_sub, ← Nat.sub_add_comm (by omega), Nat.add_sub_assoc h, Nat.add_mod_left,
+      Nat.mod_eq_of_lt (by omega)]
+
+@[simp]
+theorem toInt_sub_of_not_ssubOverflow {x y : BitVec w} (h : ¬ ssubOverflow x y) :
+    (x - y).toInt = x.toInt - y.toInt := by
+  rcases w with _|w
+  · simp [of_length_zero]
+  · simp only [ssubOverflow, Nat.add_one_sub_one, ge_iff_le, Bool.or_eq_true, decide_eq_true_eq,
+      _root_.not_or, Int.not_le, Int.not_lt] at h
+    rw [toInt_sub, Int.bmod_eq_of_le (by push_cast; omega) (by push_cast; omega)]
+
 theorem toInt_sub_toInt_lt_twoPow_iff {x y : BitVec w} :
     (x.toInt - y.toInt < - 2 ^ (w - 1))
     ↔ (x.toInt < 0 ∧ 0 ≤ y.toInt ∧ 0 ≤ (x.toInt - y.toInt).bmod (2 ^ w)) := by
@@ -3433,7 +3466,7 @@ theorem sub_ofFin (x : BitVec n) (y : Fin (2^n)) : x - .ofFin y = .ofFin (x.toFi
 -- If `x` and `n` are not literals, applying this theorem eagerly may not be a good idea.
 theorem ofNat_sub_ofNat {n} (x y : Nat) : BitVec.ofNat n x - BitVec.ofNat n y = .ofNat n ((2^n - y % 2^n) + x) := by
   apply eq_of_toNat_eq
-  simp [BitVec.ofNat, Fin.ofNat'_sub]
+  simp [BitVec.ofNat, Fin.ofNat_sub]
 
 @[simp] protected theorem sub_zero (x : BitVec n) : x - 0#n = x := by apply eq_of_toNat_eq ; simp
 
@@ -3446,9 +3479,6 @@ theorem ofNat_sub_ofNat {n} (x y : Nat) : BitVec.ofNat n x - BitVec.ofNat n y =
   · simp
   · exact Nat.le_of_lt x.isLt
 
-@[simp, bitvec_to_nat] theorem toNat_neg (x : BitVec n) : (- x).toNat = (2^n - x.toNat) % 2^n := by
-  simp [Neg.neg, BitVec.neg]
-
 theorem toNat_neg_of_pos {x : BitVec n} (h : 0#n < x) :
     (- x).toNat = 2^n - x.toNat := by
   change 0 < x.toNat at h
@@ -3460,11 +3490,21 @@ theorem toInt_neg {x : BitVec w} :
   rw [← BitVec.zero_sub, toInt_sub]
   simp [BitVec.toInt_ofNat]
 
+@[simp]
+theorem toInt_neg_of_not_negOverflow {x : BitVec w} (h : ¬ negOverflow x):
+    (-x).toInt = -x.toInt := by
+  rcases w with _|w
+  · simp [of_length_zero]
+  · have := toInt_lt (x := x); simp only [Nat.add_one_sub_one] at this
+    have := le_toInt (x := x); simp only [Nat.add_one_sub_one] at this
+    simp only [negOverflow, Nat.add_one_sub_one, beq_iff_eq] at h
+    rw [toInt_neg, Int.bmod_eq_of_le (by push_cast; omega) (by push_cast; omega)]
+
 theorem ofInt_neg {w : Nat} {n : Int} : BitVec.ofInt w (-n) = -BitVec.ofInt w n :=
   eq_of_toInt_eq (by simp [toInt_neg])
 
 @[simp] theorem toFin_neg (x : BitVec n) :
-    (-x).toFin = Fin.ofNat' (2^n) (2^n - x.toNat) :=
+    (-x).toFin = Fin.ofNat (2^n) (2^n - x.toNat) :=
   rfl
 
 theorem sub_eq_add_neg {n} (x y : BitVec n) : x - y = x + - y := by
@@ -3679,7 +3719,7 @@ theorem fill_false {w : Nat} : fill w false = 0#w := by
   by_cases h : v <;> simp [h]
 
 @[simp] theorem fill_toFin {w : Nat} {v : Bool} :
-    (fill w v).toFin = if v = true then (allOnes w).toFin else Fin.ofNat' (2 ^ w) 0 := by
+    (fill w v).toFin = if v = true then (allOnes w).toFin else Fin.ofNat (2 ^ w) 0 := by
   by_cases h : v <;> simp [h]
 
 /-! ### mul -/
@@ -3691,7 +3731,7 @@ theorem mul_def {n} {x y : BitVec n} : x * y = (ofFin <| x.toFin * y.toFin) := r
 
 theorem ofNat_mul {n} (x y : Nat) : BitVec.ofNat n (x * y) = BitVec.ofNat n x * BitVec.ofNat n y := by
   apply eq_of_toNat_eq
-  simp [BitVec.ofNat, Fin.ofNat'_mul]
+  simp [BitVec.ofNat, Fin.ofNat_mul]
 
 theorem ofNat_mul_ofNat {n} (x y : Nat) : BitVec.ofNat n x * BitVec.ofNat n y = BitVec.ofNat n (x * y) :=
   (ofNat_mul x y).symm
@@ -3749,6 +3789,49 @@ theorem two_mul {x : BitVec w} : 2#w * x = x + x := by rw [BitVec.mul_comm, mul_
   (x * y).toInt = (x.toInt * y.toInt).bmod (2^w) := by
   simp [toInt_eq_toNat_bmod, -Int.natCast_pow]
 
+@[simp]
+theorem toNat_mul_of_not_umulOverflow {x y : BitVec w} (h : ¬ umulOverflow x y) :
+    (x * y).toNat = x.toNat * y.toNat := by
+  rcases w with _|w
+  · simp [of_length_zero]
+  · simp only [umulOverflow, ge_iff_le, decide_eq_true_eq, Nat.not_le] at h
+    rw [toNat_mul, Nat.mod_eq_of_lt h]
+
+/--
+Unsigned multiplication overflow reassociation.
+If `(x * y)` and `(y * z)` do not overflow, then `(x * y) * z` overflows iff `x * (y * z)` overflows.
+-/
+theorem umulOverflow_assoc {x y z : BitVec w} (h : ¬ x.umulOverflow y) (h' : ¬ y.umulOverflow z) :
+
+    (x * y).umulOverflow z = x.umulOverflow (y * z) := by
+  simp only [umulOverflow, ge_iff_le, decide_eq_true_eq, Nat.not_le] at h h'
+  simp only [umulOverflow, toNat_mul, ge_iff_le, decide_eq_decide]
+  repeat rw [Nat.mod_eq_of_lt (by omega)]
+  rw [Nat.mul_assoc]
+
+@[simp]
+theorem toInt_mul_of_not_smulOverflow {x y : BitVec w} (h : ¬ smulOverflow x y) :
+    (x * y).toInt = x.toInt * y.toInt := by
+  rcases w with _|w
+  · simp [of_length_zero]
+  · simp only [smulOverflow, Nat.add_one_sub_one, ge_iff_le, Bool.or_eq_true, decide_eq_true_eq,
+      _root_.not_or, Int.not_le, Int.not_lt] at h
+    rw [toInt_mul, Int.bmod_eq_of_le (by push_cast; omega) (by push_cast; omega)]
+
+/--
+Signed multiplication overflow reassociation.
+If `(x * y)` and `(y * z)` do not overflow, then `(x * y) * z` overflows iff `x * (y * z)` overflows.
+-/
+theorem smulOverflow_assoc {x y z : BitVec w} (h : ¬ x.smulOverflow y) (h' : ¬ y.smulOverflow z) :
+    (x * y).smulOverflow z = x.smulOverflow (y * z) := by
+  rcases w with _|w
+  · simp [of_length_zero]
+  · simp only [smulOverflow, Nat.add_one_sub_one, ge_iff_le, Bool.or_eq_true, decide_eq_true_eq,
+      _root_.not_or, Int.not_le, Int.not_lt] at h h'
+    simp only [smulOverflow, toInt_mul, Nat.add_one_sub_one, ge_iff_le, bool_to_prop]
+    repeat rw [Int.bmod_eq_of_le (by push_cast; omega) (by push_cast; omega)]
+    rw [Int.mul_assoc]
+
 theorem ofInt_mul {n} (x y : Int) : BitVec.ofInt n (x * y) =
     BitVec.ofInt n x * BitVec.ofInt n y := by
   apply eq_of_toInt_eq
@@ -3933,6 +4016,15 @@ theorem pos_of_msb {x : BitVec w} (hx : x.msb = true) : 0#w < x := by
   rw [BitVec.not_lt, le_zero_iff] at h
   simp [h] at hx
 
+@[simp]
+theorem lt_of_msb_false_of_msb_true {x y : BitVec w} (hx : x.msb = false) (hy : y.msb = true) :
+    x < y := by
+  simp only [LT.lt]
+  have := toNat_ge_of_msb_true hy
+  have := toNat_lt_of_msb_false hx
+  simp
+  omega
+
 /-! ### udiv -/
 
 theorem udiv_def {x y : BitVec n} : x / y = BitVec.ofNat n (x.toNat / y.toNat) := by
@@ -4114,6 +4206,14 @@ theorem toInt_umod_of_msb {x y : BitVec w} (h : x.msb = false) :
     (x % y).toInt = x.toInt % y.toNat := by
   simp [toInt_eq_msb_cond, h]
 
+@[simp]
+theorem msb_umod_of_msb_false_of_ne_zero {x y : BitVec w} (hmsb : y.msb = false) (h_ne_zero : y ≠ 0#w) :
+    (x % y).msb = false := by
+  simp only [msb_umod, Bool.and_eq_false_imp, Bool.or_eq_false_iff, beq_eq_false_iff_ne,
+    ne_eq, h_ne_zero]
+  intro h
+  simp [BitVec.le_of_lt, lt_of_msb_false_of_msb_true hmsb h]
+
 /-! ### smtUDiv -/
 
 theorem smtUDiv_eq (x y : BitVec w) : smtUDiv x y = if y = 0#w then allOnes w else x / y := by
@@ -4562,7 +4662,7 @@ theorem toInt_rotateLeft {x : BitVec w} {r : Nat} :
 
 theorem toFin_rotateLeft {x : BitVec w} {r : Nat} :
   (x.rotateLeft r).toFin =
-    Fin.ofNat' (2 ^ w) (x.toNat <<< (r % w)) ||| x.toFin / Fin.ofNat' (2 ^ w) (2 ^ (w - r % w)) := by
+    Fin.ofNat (2 ^ w) (x.toNat <<< (r % w)) ||| x.toFin / Fin.ofNat (2 ^ w) (2 ^ (w - r % w)) := by
   simp [rotateLeft_def, toFin_shiftLeft, toFin_ushiftRight, toFin_or]
 
 /-! ## Rotate Right -/
@@ -4724,7 +4824,7 @@ theorem toInt_rotateRight {x : BitVec w} {r : Nat} :
   simp [rotateRight_def, toInt_shiftLeft, toInt_ushiftRight, toInt_or]
 
 theorem toFin_rotateRight {x : BitVec w} {r : Nat} :
-    (x.rotateRight r).toFin = x.toFin / Fin.ofNat' (2 ^ w) (2 ^ (r % w)) ||| Fin.ofNat' (2 ^ w) (x.toNat <<< (w - r % w)) := by
+    (x.rotateRight r).toFin = x.toFin / Fin.ofNat (2 ^ w) (2 ^ (r % w)) ||| Fin.ofNat (2 ^ w) (x.toNat <<< (w - r % w)) := by
   simp [rotateRight_def, toFin_shiftLeft, toFin_ushiftRight, toFin_or]
 
 /- ## twoPow -/
@@ -4796,7 +4896,7 @@ theorem toInt_twoPow {w i : Nat} :
       · simp [h, h', show i < w + 1 by omega, Int.natCast_pow]
 
 theorem toFin_twoPow {w i : Nat} :
-    (BitVec.twoPow w i).toFin = Fin.ofNat' (2^w) (2^i) := by
+    (BitVec.twoPow w i).toFin = Fin.ofNat (2^w) (2^i) := by
   rcases w with rfl | w
   · simp [BitVec.twoPow, BitVec.toFin, toFin_shiftLeft, Fin.fin_one_eq_zero]
   · simp [BitVec.twoPow, BitVec.toFin, toFin_shiftLeft, Nat.shiftLeft_eq]
@@ -5024,9 +5124,6 @@ theorem BitVec.setWidth_add_eq_mod {x y : BitVec w} : BitVec.setWidth i (x + y)
 
 /-! ### intMin -/
 
-/-- The bitvector of width `w` that has the smallest value when interpreted as an integer. -/
-def intMin (w : Nat) := twoPow w (w - 1)
-
 theorem getLsbD_intMin (w : Nat) : (intMin w).getLsbD i = decide (i + 1 = w) := by
   simp only [intMin, getLsbD_twoPow, bool_to_prop]
   omega
@@ -5177,9 +5274,6 @@ theorem neg_le_intMin_of_msb_eq_true {x : BitVec w} (hx : x.msb = true) : -x ≤
 
 /-! ### intMax -/
 
-/-- The bitvector of width `w` that has the largest value when interpreted as an integer. -/
-def intMax (w : Nat) := (twoPow w (w - 1)) - 1
-
 @[simp, bitvec_to_nat]
 theorem toNat_intMax : (intMax w).toNat = 2 ^ (w - 1) - 1 := by
   simp only [intMax]
@@ -5348,6 +5442,27 @@ theorem neg_ofNat_eq_ofInt_neg {w : Nat} {x : Nat} :
   apply BitVec.eq_of_toInt_eq
   simp [BitVec.toInt_neg, BitVec.toInt_ofNat]
 
+@[simp]
+theorem neg_toInt_neg {x : BitVec w} (h : x.msb = false) :
+    -(-x).toInt = x.toNat := by
+  simp [toInt_neg_eq_of_msb h, toInt_eq_toNat_of_msb, h]
+
+theorem toNat_pos_of_ne_zero {x : BitVec w} (hx : x ≠ 0#w) :
+    0 < x.toNat := by
+  simp [toNat_eq] at hx; omega
+
+theorem toNat_neg_lt_of_msb (x : BitVec w) (hmsb : x.msb = true) :
+    (-x).toNat ≤ 2^(w-1) := by
+  rcases w with _|w
+  · simp [BitVec.eq_nil x]
+  · by_cases hx : x = 0#(w + 1)
+    · simp [hx]
+    · have := BitVec.le_toNat_of_msb_true hmsb
+      have := toNat_pos_of_ne_zero hx
+      rw [toNat_neg, Nat.mod_eq_of_lt (by omega), ← Nat.two_pow_pred_add_two_pow_pred (by omega),
+        ← Nat.two_mul]
+      omega
+
 /-! ### abs -/
 
 theorem abs_eq (x : BitVec w) : x.abs = if x.msb then -x else x := rfl
@@ -5440,7 +5555,7 @@ theorem toInt_abs_eq_natAbs_of_ne_intMin {x : BitVec w} (hx : x ≠ intMin w) :
   simp [toInt_abs_eq_natAbs, hx]
 
 theorem toFin_abs {x : BitVec w} :
-    x.abs.toFin = if x.msb then Fin.ofNat' (2 ^ w) (2 ^ w - x.toNat) else x.toFin := by
+    x.abs.toFin = if x.msb then Fin.ofNat (2 ^ w) (2 ^ w - x.toNat) else x.toFin := by
   by_cases h : x.msb <;> simp [BitVec.abs, h]
 
 /-! ### Reverse -/
@@ -5510,68 +5625,54 @@ theorem msb_replicate {n w : Nat} {x : BitVec w} :
   simp only [BitVec.msb, getMsbD_replicate, Nat.zero_mod]
   cases n <;> cases w <;> simp
 
-/-! ### Decidable quantifiers -/
 
-theorem forall_zero_iff {P : BitVec 0 → Prop} :
-    (∀ v, P v) ↔ P 0#0 := by
-  constructor
-  · intro h
-    apply h
-  · intro h v
-    obtain (rfl : v = 0#0) := (by ext i ⟨⟩)
-    apply h
+/-! ### Inequalities (le / lt) -/
 
-theorem forall_cons_iff {P : BitVec (n + 1) → Prop} :
-    (∀ v : BitVec (n + 1), P v) ↔ (∀ (x : Bool) (v : BitVec n), P (v.cons x)) := by
-  constructor
-  · intro h _ _
-    apply h
-  · intro h v
-    have w : v = (v.setWidth n).cons v.msb := by simp
-    rw [w]
-    apply h
+theorem ule_eq_not_ult (x y : BitVec w) : x.ule y = !y.ult x := by
+  simp [BitVec.ule, BitVec.ult, ← decide_not]
 
-instance instDecidableForallBitVecZero (P : BitVec 0 → Prop) :
-    ∀ [Decidable (P 0#0)], Decidable (∀ v, P v)
-  | .isTrue h => .isTrue fun v => by
-    obtain (rfl : v = 0#0) := (by ext i ⟨⟩)
-    exact h
-  | .isFalse h => .isFalse (fun w => h (w _))
+/-- If two bitvectors have the same `msb`, then signed and unsigned comparisons coincide -/
+theorem slt_eq_ult_of_msb_eq {x y : BitVec w} (h : x.msb = y.msb) :
+    x.slt y = x.ult y := by
+  simp only [BitVec.slt, toInt_eq_msb_cond, BitVec.ult, decide_eq_decide, h]
+  cases y.msb <;> simp
 
-instance instDecidableForallBitVecSucc (P : BitVec (n+1) → Prop) [DecidablePred P]
-    [Decidable (∀ (x : Bool) (v : BitVec n), P (v.cons x))] : Decidable (∀ v, P v) :=
-  decidable_of_iff' (∀ x (v : BitVec n), P (v.cons x)) forall_cons_iff
+/-- If two bitvectors have different `msb`s, then unsigned comparison is determined by this bit -/
+theorem ult_eq_msb_of_msb_neq {x y : BitVec w} (h : x.msb ≠ y.msb) :
+    x.ult y = y.msb := by
+  simp only [BitVec.ult, msb_eq_decide, ne_eq, decide_eq_decide] at *
+  omega
 
-instance instDecidableExistsBitVecZero (P : BitVec 0 → Prop) [Decidable (P 0#0)] :
-    Decidable (∃ v, P v) :=
-  decidable_of_iff (¬ ∀ v, ¬ P v) Classical.not_forall_not
+/-- If two bitvectors have different `msb`s, then signed and unsigned comparisons are opposites -/
+theorem slt_eq_not_ult_of_msb_neq {x y : BitVec w} (h : x.msb ≠ y.msb) :
+    x.slt y = !x.ult y := by
+  simp only [BitVec.slt, toInt_eq_msb_cond, Bool.eq_not_of_ne h, ult_eq_msb_of_msb_neq h]
+  cases y.msb <;> (simp [-Int.natCast_pow]; omega)
 
-instance instDecidableExistsBitVecSucc (P : BitVec (n+1) → Prop) [DecidablePred P]
-    [Decidable (∀ (x : Bool) (v : BitVec n), ¬ P (v.cons x))] : Decidable (∃ v, P v) :=
-  decidable_of_iff (¬ ∀ v, ¬ P v) Classical.not_forall_not
+theorem slt_eq_ult {x y : BitVec w} :
+    x.slt y = (x.msb != y.msb).xor (x.ult y) := by
+  by_cases h : x.msb = y.msb
+  · simp [h, slt_eq_ult_of_msb_eq]
+  · have h' : x.msb != y.msb := by simp_all
+    simp [slt_eq_not_ult_of_msb_neq h, h']
 
-/--
-For small numerals this isn't necessary (as typeclass search can use the above two instances),
-but for large numerals this provides a shortcut.
-Note, however, that for large numerals the decision procedure may be very slow,
-and you should use `bv_decide` if possible.
--/
-instance instDecidableForallBitVec :
-    ∀ (n : Nat) (P : BitVec n → Prop) [DecidablePred P], Decidable (∀ v, P v)
-  | 0, _, _ => inferInstance
-  | n + 1, _, _ =>
-    have := instDecidableForallBitVec n
-    inferInstance
+theorem sle_eq_not_slt {x y : BitVec w} : x.sle y = !y.slt x := by
+  simp only [BitVec.sle, BitVec.slt, ← decide_not, decide_eq_decide]; omega
 
-/--
-For small numerals this isn't necessary (as typeclass search can use the above two instances),
-but for large numerals this provides a shortcut.
-Note, however, that for large numerals the decision procedure may be very slow.
--/
-instance instDecidableExistsBitVec :
-    ∀ (n : Nat) (P : BitVec n → Prop) [DecidablePred P], Decidable (∃ v, P v)
-  | 0, _, _ => inferInstance
-  | _ + 1, _, _ => inferInstance
+theorem zero_sle_eq_not_msb {w : Nat} {x : BitVec w} : BitVec.sle 0#w x = !x.msb := by
+  rw [sle_eq_not_slt, BitVec.slt_zero_eq_msb]
+
+theorem zero_sle_iff_msb_eq_false {w : Nat} {x : BitVec w} : BitVec.sle 0#w x ↔ x.msb = false := by
+  simp [zero_sle_eq_not_msb]
+
+theorem toNat_toInt_of_sle {w : Nat} {x : BitVec w} (hx : BitVec.sle 0#w x) : x.toInt.toNat = x.toNat :=
+  toNat_toInt_of_msb x (zero_sle_iff_msb_eq_false.1 hx)
+
+theorem sle_eq_ule {x y : BitVec w} : x.sle y = (x.msb != y.msb ^^ x.ule y) := by
+  rw [sle_eq_not_slt, slt_eq_ult, ← Bool.xor_not, ← ule_eq_not_ult, bne_comm]
+
+theorem sle_eq_ule_of_msb_eq {x y : BitVec w} (h : x.msb = y.msb) : x.sle y = x.ule y := by
+  simp [BitVec.sle_eq_ule, h]
 
 /-! ### Deprecations -/
 

src/Init/Data/Bool.lean

@@ -455,7 +455,7 @@ theorem toNat_lt (b : Bool) : b.toNat < 2 :=
 /--
 Converts `true` to `1` and `false` to `0`.
 -/
-def toInt (b : Bool) : Int := cond b 1 0
+@[expose] def toInt (b : Bool) : Int := cond b 1 0
 
 @[simp] theorem toInt_false : false.toInt = 0 := rfl
 

src/Init/Data/ByteArray/Basic.lean

@@ -205,7 +205,7 @@ def foldlM {β : Type v} {m : Type v → Type w} [Monad m] (f : β → UInt8 →
 
 @[inline]
 def foldl {β : Type v} (f : β → UInt8 → β) (init : β) (as : ByteArray) (start := 0) (stop := as.size) : β :=
-  Id.run <| as.foldlM f init start stop
+  Id.run <| as.foldlM (pure <| f · ·) init start stop
 
 /-- Iterator over the bytes (`UInt8`) of a `ByteArray`.
 

src/Init/Data/Fin/Basic.lean

@@ -46,15 +46,12 @@ Returns `a` modulo `n` as a `Fin n`.
 
 The assumption `NeZero n` ensures that `Fin n` is nonempty.
 -/
-@[expose] protected def ofNat' (n : Nat) [NeZero n] (a : Nat) : Fin n :=
+@[expose] protected def ofNat (n : Nat) [NeZero n] (a : Nat) : Fin n :=
   ⟨a % n, Nat.mod_lt _ (pos_of_neZero n)⟩
 
-/--
-Returns `a` modulo `n + 1` as a `Fin n.succ`.
--/
-@[deprecated Fin.ofNat' (since := "2024-11-27")]
-protected def ofNat {n : Nat} (a : Nat) : Fin (n + 1) :=
-  ⟨a % (n+1), Nat.mod_lt _ (Nat.zero_lt_succ _)⟩
+@[deprecated Fin.ofNat (since := "2025-05-28")]
+protected def ofNat' (n : Nat) [NeZero n] (a : Nat) : Fin n :=
+  Fin.ofNat n a
 
 -- We provide this because other similar types have a `toNat` function, but `simp` rewrites
 -- `i.toNat` to `i.val`.
@@ -84,7 +81,7 @@ Examples:
  * `(2 : Fin 3) + (2 : Fin 3) = (1 : Fin 3)`
 -/
 protected def add : Fin n → Fin n → Fin n
-  | ⟨a, h⟩, ⟨b, _⟩ => ⟨(a + b) % n, mlt h⟩
+  | ⟨a, h⟩, ⟨b, _⟩ => ⟨(a + b) % n, by exact mlt h⟩
 
 /--
 Multiplication modulo `n`, usually invoked via the `*` operator.
@@ -95,7 +92,7 @@ Examples:
  * `(3 : Fin 10) * (7 : Fin 10) = (1 : Fin 10)`
 -/
 protected def mul : Fin n → Fin n → Fin n
-  | ⟨a, h⟩, ⟨b, _⟩ => ⟨(a * b) % n, mlt h⟩
+  | ⟨a, h⟩, ⟨b, _⟩ => ⟨(a * b) % n, by exact mlt h⟩
 
 /--
 Subtraction modulo `n`, usually invoked via the `-` operator.
@@ -122,7 +119,7 @@ protected def sub : Fin n → Fin n → Fin n
   using recursion on the second argument.
   See issue #4413.
   -/
-  | ⟨a, h⟩, ⟨b, _⟩ => ⟨((n - b) + a) % n, mlt h⟩
+  | ⟨a, h⟩, ⟨b, _⟩ => ⟨((n - b) + a) % n, by exact mlt h⟩
 
 /-!
 Remark: land/lor can be defined without using (% n), but
@@ -164,19 +161,19 @@ def modn : Fin n → Nat → Fin n
 Bitwise and.
 -/
 def land : Fin n → Fin n → Fin n
-  | ⟨a, h⟩, ⟨b, _⟩ => ⟨(Nat.land a b) % n, mlt h⟩
+  | ⟨a, h⟩, ⟨b, _⟩ => ⟨(Nat.land a b) % n, by exact mlt h⟩
 
 /--
 Bitwise or.
 -/
 def lor : Fin n → Fin n → Fin n
-  | ⟨a, h⟩, ⟨b, _⟩ => ⟨(Nat.lor a b) % n, mlt h⟩
+  | ⟨a, h⟩, ⟨b, _⟩ => ⟨(Nat.lor a b) % n, by exact mlt h⟩
 
 /--
 Bitwise xor (“exclusive or”).
 -/
 def xor : Fin n → Fin n → Fin n
-  | ⟨a, h⟩, ⟨b, _⟩ => ⟨(Nat.xor a b) % n, mlt h⟩
+  | ⟨a, h⟩, ⟨b, _⟩ => ⟨(Nat.xor a b) % n, by exact mlt h⟩
 
 /--
 Bitwise left shift of bounded numbers, with wraparound on overflow.
@@ -187,7 +184,7 @@ Examples:
  * `(1 : Fin 10) <<< (4 : Fin 10) = (6 : Fin 10)`
 -/
 def shiftLeft : Fin n → Fin n → Fin n
-  | ⟨a, h⟩, ⟨b, _⟩ => ⟨(a <<< b) % n, mlt h⟩
+  | ⟨a, h⟩, ⟨b, _⟩ => ⟨(a <<< b) % n, by exact mlt h⟩
 
 /--
 Bitwise right shift of bounded numbers.
@@ -201,7 +198,7 @@ Examples:
  * `(15 : Fin 17) >>> (2 : Fin 17) = (3 : Fin 17)`
 -/
 def shiftRight : Fin n → Fin n → Fin n
-  | ⟨a, h⟩, ⟨b, _⟩ => ⟨(a >>> b) % n, mlt h⟩
+  | ⟨a, h⟩, ⟨b, _⟩ => ⟨(a >>> b) % n, by exact mlt h⟩
 
 instance : Add (Fin n) where
   add := Fin.add
@@ -230,7 +227,7 @@ instance : ShiftRight (Fin n) where
   shiftRight := Fin.shiftRight
 
 instance instOfNat {n : Nat} [NeZero n] {i : Nat} : OfNat (Fin n) i where
-  ofNat := Fin.ofNat' n i
+  ofNat := Fin.ofNat n i
 
 /-- If you actually have an element of `Fin n`, then the `n` is always positive -/
 protected theorem pos (i : Fin n) : 0 < n :=

src/Init/Data/Fin/Fold.lean

@@ -100,6 +100,11 @@ Fin.foldrM n f xₙ = do
 
 /-! ### foldlM -/
 
+@[congr] theorem foldlM_congr [Monad m] {n k : Nat} (w : n = k) (f : α → Fin n → m α) :
+    foldlM n f = foldlM k (fun x i => f x (i.cast w.symm)) := by
+  subst w
+  rfl
+
 theorem foldlM_loop_lt [Monad m] (f : α → Fin n → m α) (x) (h : i < n) :
     foldlM.loop n f x i = f x ⟨i, h⟩ >>= (foldlM.loop n f . (i+1)) := by
   rw [foldlM.loop, dif_pos h]
@@ -120,14 +125,49 @@ theorem foldlM_loop [Monad m] (f : α → Fin (n+1) → m α) (x) (h : i < n+1)
     rw [foldlM_loop_eq, foldlM_loop_eq]
 termination_by n - i
 
-@[simp] theorem foldlM_zero [Monad m] (f : α → Fin 0 → m α) (x) : foldlM 0 f x = pure x :=
-  foldlM_loop_eq ..
+@[simp] theorem foldlM_zero [Monad m] (f : α → Fin 0 → m α) : foldlM 0 f = pure := by
+  funext x
+  exact foldlM_loop_eq ..
 
-theorem foldlM_succ [Monad m] (f : α → Fin (n+1) → m α) (x) :
-    foldlM (n+1) f x = f x 0 >>= foldlM n (fun x j => f x j.succ) := foldlM_loop ..
+theorem foldlM_succ [Monad m] (f : α → Fin (n+1) → m α) :
+    foldlM (n+1) f = fun x => f x 0 >>= foldlM n (fun x j => f x j.succ) := by
+  funext x
+  exact foldlM_loop ..
+
+/-- Variant of `foldlM_succ` that splits off `Fin.last n` rather than `0`. -/
+theorem foldlM_succ_last [Monad m] [LawfulMonad m] (f : α → Fin (n+1) → m α) :
+    foldlM (n+1) f = fun x => foldlM n (fun x j => f x j.castSucc) x >>= (f · (Fin.last n)) := by
+  funext x
+  induction n generalizing x with
+  | zero =>
+    simp [foldlM_succ]
+  | succ n ih =>
+    rw [foldlM_succ]
+    conv => rhs; rw [foldlM_succ]
+    simp only [castSucc_zero, castSucc_succ, bind_assoc]
+    congr 1
+    funext x
+    rw [ih]
+    simp
+
+theorem foldlM_add [Monad m] [LawfulMonad m] (f : α → Fin (n + k) → m α) :
+    foldlM (n + k) f =
+      fun x => foldlM n (fun x i => f x (i.castLE (Nat.le_add_right n k))) x >>= foldlM k (fun x i => f x (i.natAdd n)) := by
+  induction k with
+  | zero =>
+    funext x
+    simp
+  | succ k ih =>
+    funext x
+    simp [foldlM_succ_last, ← Nat.add_assoc, ih]
 
 /-! ### foldrM -/
 
+@[congr] theorem foldrM_congr [Monad m] {n k : Nat} (w : n = k) (f : Fin n → α → m α) :
+    foldrM n f = foldrM k (fun i => f (i.cast w.symm)) := by
+  subst w
+  rfl
+
 theorem foldrM_loop_zero [Monad m] (f : Fin n → α → m α) (x) :
     foldrM.loop n f ⟨0, Nat.zero_le _⟩ x = pure x := by
   rw [foldrM.loop]
@@ -143,21 +183,47 @@ theorem foldrM_loop [Monad m] [LawfulMonad m] (f : Fin (n+1) → α → m α) (x
   | zero =>
     rw [foldrM_loop_zero, foldrM_loop_succ, pure_bind]
     conv => rhs; rw [←bind_pure (f 0 x)]
-    congr
-    funext
-    try simp only [foldrM.loop] -- the try makes this proof work with and without opaque wf rec
+    rfl
   | succ i ih =>
     rw [foldrM_loop_succ, foldrM_loop_succ, bind_assoc]
     congr; funext; exact ih ..
 
-@[simp] theorem foldrM_zero [Monad m] (f : Fin 0 → α → m α) (x) : foldrM 0 f x = pure x :=
-  foldrM_loop_zero ..
+@[simp] theorem foldrM_zero [Monad m] (f : Fin 0 → α → m α) : foldrM 0 f = pure := by
+  funext x
+  exact foldrM_loop_zero ..
 
-theorem foldrM_succ [Monad m] [LawfulMonad m] (f : Fin (n+1) → α → m α) (x) :
-    foldrM (n+1) f x = foldrM n (fun i => f i.succ) x >>= f 0 := foldrM_loop ..
+theorem foldrM_succ [Monad m] [LawfulMonad m] (f : Fin (n+1) → α → m α) :
+    foldrM (n+1) f = fun x => foldrM n (fun i => f i.succ) x >>= f 0 := by
+  funext x
+  exact foldrM_loop ..
+
+theorem foldrM_succ_last [Monad m] [LawfulMonad m] (f : Fin (n+1) → α → m α) :
+    foldrM (n+1) f = fun x => f (Fin.last n) x >>= foldrM n (fun i => f i.castSucc) := by
+  funext x
+  induction n generalizing x with
+  | zero => simp [foldrM_succ]
+  | succ n ih =>
+    rw [foldrM_succ]
+    conv => rhs; rw [foldrM_succ]
+    simp [ih]
+
+theorem foldrM_add [Monad m] [LawfulMonad m] (f : Fin (n + k) → α → m α) :
+    foldrM (n + k) f =
+      fun x => foldrM k (fun i => f (i.natAdd n)) x >>= foldrM n (fun i => f (i.castLE (Nat.le_add_right n k))) := by
+  induction k with
+  | zero =>
+    simp
+  | succ k ih =>
+    funext x
+    simp [foldrM_succ_last, ← Nat.add_assoc, ih]
 
 /-! ### foldl -/
 
+@[congr] theorem foldl_congr {n k : Nat} (w : n = k) (f : α → Fin n → α) :
+    foldl n f = foldl k (fun x i => f x (i.cast w.symm)) := by
+  subst w
+  rfl
+
 theorem foldl_loop_lt (f : α → Fin n → α) (x) (h : i < n) :
     foldl.loop n f x i = foldl.loop n f (f x ⟨i, h⟩) (i+1) := by
   rw [foldl.loop, dif_pos h]
@@ -187,14 +253,34 @@ theorem foldl_succ_last (f : α → Fin (n+1) → α) (x) :
   rw [foldl_succ]
   induction n generalizing x with
   | zero => simp [foldl_succ, Fin.last]
-  | succ n ih => rw [foldl_succ, ih (f · ·.succ), foldl_succ]; simp [succ_castSucc]
+  | succ n ih => rw [foldl_succ, ih (f · ·.succ), foldl_succ]; simp
+
+theorem foldl_add (f : α → Fin (n + m) → α) (x) :
+    foldl (n + m) f x =
+      foldl m (fun x i => f x (i.natAdd n))
+        (foldl n (fun x i => f x (i.castLE (Nat.le_add_right n m))) x):= by
+  induction m with
+  | zero => simp
+  | succ m ih => simp [foldl_succ_last, ih, ← Nat.add_assoc]
 
 theorem foldl_eq_foldlM (f : α → Fin n → α) (x) :
-    foldl n f x = foldlM (m:=Id) n f x := by
+    foldl n f x = (foldlM (m := Id) n (pure <| f · ·) x).run := by
   induction n generalizing x <;> simp [foldl_succ, foldlM_succ, *]
 
+-- This is not marked `@[simp]` as it would match on every occurrence of `foldlM`.
+theorem foldlM_pure [Monad m] [LawfulMonad m] {n} {f : α → Fin n → α} :
+    foldlM n (fun x i => pure (f x i)) x = (pure (foldl n f x) : m α) := by
+  induction n generalizing x with
+  | zero => simp
+  | succ n ih => simp [foldlM_succ, foldl_succ, ih]
+
 /-! ### foldr -/
 
+@[congr] theorem foldr_congr {n k : Nat} (w : n = k) (f : Fin n → α → α) :
+    foldr n f = foldr k (fun i => f (i.cast w.symm)) := by
+  subst w
+  rfl
+
 theorem foldr_loop_zero (f : Fin n → α → α) (x) :
     foldr.loop n f 0 (Nat.zero_le _) x = x := by
   rw [foldr.loop]
@@ -220,10 +306,18 @@ theorem foldr_succ_last (f : Fin (n+1) → α → α) (x) :
     foldr (n+1) f x = foldr n (f ·.castSucc) (f (last n) x) := by
   induction n generalizing x with
   | zero => simp [foldr_succ, Fin.last]
-  | succ n ih => rw [foldr_succ, ih (f ·.succ), foldr_succ]; simp [succ_castSucc]
+  | succ n ih => rw [foldr_succ, ih (f ·.succ), foldr_succ]; simp
+
+theorem foldr_add (f : Fin (n + m) → α → α) (x) :
+    foldr (n + m) f x =
+      foldr n (fun i => f (i.castLE (Nat.le_add_right n m)))
+        (foldr m (fun i => f (i.natAdd n)) x) := by
+  induction m generalizing x with
+  | zero => simp
+  | succ m ih => simp [foldr_succ_last, ih, ← Nat.add_assoc]
 
 theorem foldr_eq_foldrM (f : Fin n → α → α) (x) :
-    foldr n f x = foldrM (m:=Id) n f x := by
+    foldr n f x = (foldrM (m := Id) n (pure <| f · ·) x).run := by
   induction n <;> simp [foldr_succ, foldrM_succ, *]
 
 theorem foldl_rev (f : Fin n → α → α) (x) :
@@ -238,4 +332,11 @@ theorem foldr_rev (f : α → Fin n → α) (x) :
   | zero => simp
   | succ n ih => rw [foldl_succ_last, foldr_succ, ← ih]; simp [rev_succ]
 
+-- This is not marked `@[simp]` as it would match on every occurrence of `foldrM`.
+theorem foldrM_pure [Monad m] [LawfulMonad m] {n} {f : Fin n → α → α} :
+    foldrM n (fun i x => pure (f i x)) x = (pure (foldr n f x) : m α) := by
+  induction n generalizing x with
+  | zero => simp
+  | succ n ih => simp [foldrM_succ, foldr_succ, ih]
+
 end Fin

src/Init/Data/Fin/Lemmas.lean

@@ -15,10 +15,9 @@ import Init.Omega
 
 namespace Fin
 
-@[simp] theorem ofNat'_zero (n : Nat) [NeZero n] : Fin.ofNat' n 0 = 0 := rfl
+@[simp] theorem ofNat_zero (n : Nat) [NeZero n] : Fin.ofNat n 0 = 0 := rfl
 
-@[deprecated Fin.pos (since := "2024-11-11")]
-theorem size_pos (i : Fin n) : 0 < n := i.pos
+@[deprecated ofNat_zero (since := "2025-05-28")] abbrev ofNat'_zero := @ofNat_zero
 
 theorem mod_def (a m : Fin n) : a % m = Fin.mk (a % m) (Nat.lt_of_le_of_lt (Nat.mod_le _ _) a.2) :=
   rfl
@@ -29,8 +28,6 @@ theorem sub_def (a b : Fin n) : a - b = Fin.mk (((n - b) + a) % n) (Nat.mod_lt _
 
 theorem pos' : ∀ [Nonempty (Fin n)], 0 < n | ⟨i⟩ => i.pos
 
-@[deprecated pos' (since := "2024-11-11")] abbrev size_pos' := @pos'
-
 @[simp] theorem is_lt (a : Fin n) : (a : Nat) < n := a.2
 
 theorem pos_iff_nonempty {n : Nat} : 0 < n ↔ Nonempty (Fin n) :=
@@ -66,19 +63,25 @@ theorem mk_val (i : Fin n) : (⟨i, i.isLt⟩ : Fin n) = i := Fin.eta ..
     0 = (⟨a, ha⟩ : Fin n) ↔ a = 0 := by
   simp [eq_comm]
 
-@[simp] theorem val_ofNat' (n : Nat) [NeZero n] (a : Nat) :
-  (Fin.ofNat' n a).val = a % n := rfl
+@[simp] theorem val_ofNat (n : Nat) [NeZero n] (a : Nat) :
+  (Fin.ofNat n a).val = a % n := rfl
 
-@[simp] theorem ofNat'_self {n : Nat} [NeZero n] : Fin.ofNat' n n = 0 := by
+@[deprecated val_ofNat (since := "2025-05-28")] abbrev val_ofNat' := @val_ofNat
+
+@[simp] theorem ofNat_self {n : Nat} [NeZero n] : Fin.ofNat n n = 0 := by
   ext
   simp
   congr
 
-@[simp] theorem ofNat'_val_eq_self [NeZero n] (x : Fin n) : (Fin.ofNat' n x) = x := by
+@[deprecated ofNat_self (since := "2025-05-28")] abbrev ofNat'_self := @ofNat_self
+
+@[simp] theorem ofNat_val_eq_self [NeZero n] (x : Fin n) : (Fin.ofNat n x) = x := by
   ext
-  rw [val_ofNat', Nat.mod_eq_of_lt]
+  rw [val_ofNat, Nat.mod_eq_of_lt]
   exact x.2
 
+@[deprecated ofNat_val_eq_self (since := "2025-05-28")] abbrev ofNat'_val_eq_self := @ofNat_val_eq_self
+
 @[simp] theorem mod_val (a b : Fin n) : (a % b).val = a.val % b.val :=
   rfl
 
@@ -99,20 +102,55 @@ theorem dite_val {n : Nat} {c : Prop} [Decidable c] {x y : Fin n} :
     (if c then x else y).val = if c then x.val else y.val := by
   by_cases c <;> simp [*]
 
-instance (n : Nat) [NeZero n] : NatCast (Fin n) where
-  natCast a := Fin.ofNat' n a
+namespace NatCast
 
+/--
+This is not a global instance, but may be activated locally via `open Fin.NatCast in ...`.
+
+This is not an instance because the `binop%` elaborator assumes that
+there are no non-trivial coercion loops,
+but this introduces a coercion from `Nat` to `Fin n` and back.
+
+Non-trivial loops lead to undesirable and counterintuitive elaboration behavior.
+For example, for `x : Fin k` and `n : Nat`,
+it causes `x < n` to be elaborated as `x < ↑n` rather than `↑x < n`,
+silently introducing wraparound arithmetic.
+
+Note: as of 2025-06-03, Mathlib has such a coercion for `Fin n` anyway!
+-/
+@[expose]
+def instNatCast (n : Nat) [NeZero n] : NatCast (Fin n) where
+  natCast a := Fin.ofNat n a
+
+attribute [scoped instance] instNatCast
+
+end NatCast
+
+@[expose]
 def intCast [NeZero n] (a : Int) : Fin n :=
   if 0 ≤ a then
-    Fin.ofNat' n a.natAbs
+    Fin.ofNat n a.natAbs
   else
-    - Fin.ofNat' n a.natAbs
+    - Fin.ofNat n a.natAbs
 
-instance (n : Nat) [NeZero n] : IntCast (Fin n) where
+namespace IntCast
+
+/--
+This is not a global instance, but may be activated locally via `open Fin.IntCast in ...`.
+
+See the doc-string for `Fin.NatCast.instNatCast` for more details.
+-/
+@[expose]
+def instIntCast (n : Nat) [NeZero n] : IntCast (Fin n) where
   intCast := Fin.intCast
 
+attribute [scoped instance] instIntCast
+
+end IntCast
+
+open IntCast in
 theorem intCast_def {n : Nat} [NeZero n] (x : Int) :
-    (x : Fin n) = if 0 ≤ x then Fin.ofNat' n x.natAbs else -Fin.ofNat' n x.natAbs := rfl
+    (x : Fin n) = if 0 ≤ x then Fin.ofNat n x.natAbs else -Fin.ofNat n x.natAbs := rfl
 
 /-! ### order -/
 
@@ -646,6 +684,20 @@ theorem rev_castSucc (k : Fin n) : rev (castSucc k) = succ (rev k) := k.rev_cast
 
 theorem rev_succ (k : Fin n) : rev (succ k) = castSucc (rev k) := k.rev_addNat 1
 
+@[simp, grind _=_]
+theorem castSucc_succ (i : Fin n) : i.succ.castSucc = i.castSucc.succ := rfl
+
+@[simp, grind =]
+theorem castLE_refl (h : n ≤ n) (i : Fin n) : i.castLE h = i := rfl
+
+@[simp, grind =]
+theorem castSucc_castLE (h : n ≤ m) (i : Fin n) :
+    (i.castLE h).castSucc = i.castLE (by omega) := rfl
+
+@[simp, grind =]
+theorem castSucc_natAdd (n : Nat) (i : Fin k) :
+    (i.natAdd n).castSucc = (i.castSucc).natAdd n := rfl
+
 /-! ### pred -/
 
 @[simp] theorem coe_pred (j : Fin (n + 1)) (h : j ≠ 0) : (j.pred h : Nat) = j - 1 := rfl
@@ -783,7 +835,7 @@ parameter, `Fin.cases` is the corresponding case analysis operator, and `Fin.rev
 version that starts at the greatest value instead of `0`.
 -/
 -- FIXME: Performance review
-@[elab_as_elim] def induction {motive : Fin (n + 1) → Sort _} (zero : motive 0)
+@[elab_as_elim, expose] def induction {motive : Fin (n + 1) → Sort _} (zero : motive 0)
     (succ : ∀ i : Fin n, motive (castSucc i) → motive i.succ) :
     ∀ i : Fin (n + 1), motive i
   | ⟨i, hi⟩ => go i hi
@@ -825,7 +877,7 @@ The two cases are:
 
 The corresponding induction principle is `Fin.induction`.
 -/
-@[elab_as_elim] def cases {motive : Fin (n + 1) → Sort _}
+@[elab_as_elim, expose] def cases {motive : Fin (n + 1) → Sort _}
     (zero : motive 0) (succ : ∀ i : Fin n, motive i.succ) :
     ∀ i : Fin (n + 1), motive i := induction zero fun i _ => succ i
 
@@ -951,30 +1003,38 @@ theorem val_ne_zero_iff [NeZero n] {a : Fin n} : a.val ≠ 0 ↔ a ≠ 0 :=
 
 /-! ### add -/
 
-theorem ofNat'_add [NeZero n] (x : Nat) (y : Fin n) :
-    Fin.ofNat' n x + y = Fin.ofNat' n (x + y.val) := by
+theorem ofNat_add [NeZero n] (x : Nat) (y : Fin n) :
+    Fin.ofNat n x + y = Fin.ofNat n (x + y.val) := by
   apply Fin.eq_of_val_eq
-  simp [Fin.ofNat', Fin.add_def]
+  simp [Fin.ofNat, Fin.add_def]
 
-theorem add_ofNat' [NeZero n] (x : Fin n) (y : Nat) :
-    x + Fin.ofNat' n y = Fin.ofNat' n (x.val + y) := by
+@[deprecated ofNat_add (since := "2025-05-28")] abbrev ofNat_add' := @ofNat_add
+
+theorem add_ofNat [NeZero n] (x : Fin n) (y : Nat) :
+    x + Fin.ofNat n y = Fin.ofNat n (x.val + y) := by
   apply Fin.eq_of_val_eq
-  simp [Fin.ofNat', Fin.add_def]
+  simp [Fin.ofNat, Fin.add_def]
+
+@[deprecated add_ofNat (since := "2025-05-28")] abbrev add_ofNat' := @add_ofNat
 
 /-! ### sub -/
 
 protected theorem coe_sub (a b : Fin n) : ((a - b : Fin n) : Nat) = ((n - b) + a) % n := by
   cases a; cases b; rfl
 
-theorem ofNat'_sub [NeZero n] (x : Nat) (y : Fin n) :
-    Fin.ofNat' n x - y = Fin.ofNat' n ((n - y.val) + x) := by
+theorem ofNat_sub [NeZero n] (x : Nat) (y : Fin n) :
+    Fin.ofNat n x - y = Fin.ofNat n ((n - y.val) + x) := by
   apply Fin.eq_of_val_eq
-  simp [Fin.ofNat', Fin.sub_def]
+  simp [Fin.ofNat, Fin.sub_def]
 
-theorem sub_ofNat' [NeZero n] (x : Fin n) (y : Nat) :
-    x - Fin.ofNat' n y = Fin.ofNat' n ((n - y % n) + x.val) := by
+@[deprecated ofNat_sub (since := "2025-05-28")] abbrev ofNat_sub' := @ofNat_sub
+
+theorem sub_ofNat [NeZero n] (x : Fin n) (y : Nat) :
+    x - Fin.ofNat n y = Fin.ofNat n ((n - y % n) + x.val) := by
   apply Fin.eq_of_val_eq
-  simp [Fin.ofNat', Fin.sub_def]
+  simp [Fin.ofNat, Fin.sub_def]
+
+@[deprecated sub_ofNat (since := "2025-05-28")] abbrev sub_ofNat' := @sub_ofNat
 
 @[simp] protected theorem sub_self [NeZero n] {x : Fin n} : x - x = 0 := by
   ext
@@ -1019,17 +1079,32 @@ theorem val_neg {n : Nat} [NeZero n] (x : Fin n) :
     have := Fin.val_ne_zero_iff.mpr h
     omega
 
+protected theorem sub_eq_add_neg {n : Nat} (x y : Fin n) : x - y = x + -y := by
+  by_cases h : n = 0
+  · subst h
+    apply elim0 x
+  · replace h : NeZero n := ⟨h⟩
+    ext
+    rw [Fin.coe_sub, Fin.val_add, val_neg]
+    split
+    · simp_all
+    · simp [Nat.add_comm]
+
 /-! ### mul -/
 
-theorem ofNat'_mul [NeZero n] (x : Nat) (y : Fin n) :
-    Fin.ofNat' n x * y = Fin.ofNat' n (x * y.val) := by
+theorem ofNat_mul [NeZero n] (x : Nat) (y : Fin n) :
+    Fin.ofNat n x * y = Fin.ofNat n (x * y.val) := by
   apply Fin.eq_of_val_eq
-  simp [Fin.ofNat', Fin.mul_def]
+  simp [Fin.ofNat, Fin.mul_def]
 
-theorem mul_ofNat' [NeZero n] (x : Fin n) (y : Nat) :
-    x * Fin.ofNat' n y = Fin.ofNat' n (x.val * y) := by
+@[deprecated ofNat_mul (since := "2025-05-28")] abbrev ofNat_mul' := @ofNat_mul
+
+theorem mul_ofNat [NeZero n] (x : Fin n) (y : Nat) :
+    x * Fin.ofNat n y = Fin.ofNat n (x.val * y) := by
   apply Fin.eq_of_val_eq
-  simp [Fin.ofNat', Fin.mul_def]
+  simp [Fin.ofNat, Fin.mul_def]
+
+@[deprecated mul_ofNat (since := "2025-05-28")] abbrev mul_ofNat' := @mul_ofNat
 
 theorem val_mul {n : Nat} : ∀ a b : Fin n, (a * b).val = a.val * b.val % n
   | ⟨_, _⟩, ⟨_, _⟩ => rfl

src/Init/Data/FloatArray/Basic.lean

@@ -165,7 +165,7 @@ def foldlM {β : Type v} {m : Type v → Type w} [Monad m] (f : β → Float →
 
 @[inline]
 def foldl {β : Type v} (f : β → Float → β) (init : β) (as : FloatArray) (start := 0) (stop := as.size) : β :=
-  Id.run <| as.foldlM f init start stop
+  Id.run <| as.foldlM (pure <| f · ·) init start stop
 
 end FloatArray
 

src/Init/Data/Format/Basic.lean

@@ -142,17 +142,36 @@ private structure WorkItem where
   indent : Int
   activeTags : Nat
 
+/--
+A directive indicating whether a given work group is able to be flattened.
+
+- `allow` indicates that the group is allowed to be flattened; its argument is `true` if
+  there is sufficient space for it to be flattened (and so it should be), or `false` if not.
+- `disallow` means that this group should not be flattened irrespective of space concerns.
+  This is used at levels of a `Format` outside of any flattening groups. It is necessary to track
+  this so that, after a hard line break, we know whether to try to flatten the next line.
+-/
+inductive FlattenAllowability where
+  | allow (fits : Bool)
+  | disallow
+  deriving BEq
+
+/-- Whether the given directive indicates that flattening should occur. -/
+def FlattenAllowability.shouldFlatten : FlattenAllowability → Bool
+  | allow true => true
+  | _ => false
+
 private structure WorkGroup where
-  flatten : Bool
-  flb     : FlattenBehavior
-  items   : List WorkItem
+  fla   : FlattenAllowability
+  flb   : FlattenBehavior
+  items : List WorkItem
 
 private partial def spaceUptoLine' : List WorkGroup → Nat → Nat → SpaceResult
   |   [],                         _,   _ => {}
   |   { items := [],    .. }::gs, col, w => spaceUptoLine' gs col w
   | g@{ items := i::is, .. }::gs, col, w =>
     merge w
-      (spaceUptoLine i.f g.flatten (w + col - i.indent) w)
+      (spaceUptoLine i.f g.fla.shouldFlatten (w + col - i.indent) w)
       (spaceUptoLine' ({ g with items := is }::gs) col)
 
 /-- A monad in which we can pretty-print `Format` objects. -/
@@ -169,11 +188,11 @@ open MonadPrettyFormat
 private def pushGroup (flb : FlattenBehavior) (items : List WorkItem) (gs : List WorkGroup) (w : Nat) [Monad m] [MonadPrettyFormat m] : m (List WorkGroup) := do
   let k  ← currColumn
   -- Flatten group if it + the remainder (gs) fits in the remaining space. For `fill`, measure only up to the next (ungrouped) line break.
-  let g  := { flatten := flb == FlattenBehavior.allOrNone, flb := flb, items := items : WorkGroup }
+  let g  := { fla := .allow (flb == FlattenBehavior.allOrNone), flb := flb, items := items : WorkGroup }
   let r  := spaceUptoLine' [g] k (w-k)
   let r' := merge (w-k) r (spaceUptoLine' gs k)
   -- Prevent flattening if any item contains a hard line break, except within `fill` if it is ungrouped (=> unflattened)
-  return { g with flatten := !r.foundFlattenedHardLine && r'.space <= w-k }::gs
+  return { g with fla := .allow (!r.foundFlattenedHardLine && r'.space <= w-k) }::gs
 
 private partial def be (w : Nat) [Monad m] [MonadPrettyFormat m] : List WorkGroup → m Unit
   | []                           => pure ()
@@ -200,11 +219,15 @@ private partial def be (w : Nat) [Monad m] [MonadPrettyFormat m] : List WorkGrou
         pushNewline i.indent.toNat
         let is := { i with f := text (s.extract (s.next p) s.endPos) }::is
         -- after a hard line break, re-evaluate whether to flatten the remaining group
-        pushGroup g.flb is gs w >>= be w
+        -- note that we shouldn't start flattening after a hard break outside a group
+        if g.fla == .disallow then
+          be w (gs' is)
+        else
+          pushGroup g.flb is gs w >>= be w
     | line =>
       match g.flb with
       | FlattenBehavior.allOrNone =>
-        if g.flatten then
+        if g.fla.shouldFlatten then
           -- flatten line = text " "
           pushOutput " "
           endTags i.activeTags
@@ -220,10 +243,10 @@ private partial def be (w : Nat) [Monad m] [MonadPrettyFormat m] : List WorkGrou
           endTags i.activeTags
           pushGroup FlattenBehavior.fill is gs w >>= be w
         -- if preceding fill item fit in a single line, try to fit next one too
-        if g.flatten then
+        if g.fla.shouldFlatten then
           let gs'@(g'::_) ← pushGroup FlattenBehavior.fill is gs (w - " ".length)
             | panic "unreachable"
-          if g'.flatten then
+          if g'.fla.shouldFlatten then
             pushOutput " "
             endTags i.activeTags
             be w gs'  -- TODO: use `return`
@@ -232,7 +255,7 @@ private partial def be (w : Nat) [Monad m] [MonadPrettyFormat m] : List WorkGrou
         else
           breakHere
     | align force =>
-      if g.flatten && !force then
+      if g.fla.shouldFlatten && !force then
         -- flatten (align false) = nil
         endTags i.activeTags
         be w (gs' is)
@@ -247,7 +270,7 @@ private partial def be (w : Nat) [Monad m] [MonadPrettyFormat m] : List WorkGrou
           endTags i.activeTags
           be w (gs' is)
     | group f flb =>
-      if g.flatten then
+      if g.fla.shouldFlatten then
         -- flatten (group f) = flatten f
         be w (gs' ({ i with f }::is))
       else
@@ -256,7 +279,7 @@ private partial def be (w : Nat) [Monad m] [MonadPrettyFormat m] : List WorkGrou
 /-- Render the given `f : Format` with a line width of `w`.
 `indent` is the starting amount to indent each line by. -/
 def prettyM (f : Format) (w : Nat) (indent : Nat := 0) [Monad m] [MonadPrettyFormat m] : m Unit :=
-  be w [{ flb := FlattenBehavior.allOrNone, flatten := false, items := [{ f := f, indent, activeTags := 0 }]}]
+  be w [{ flb := FlattenBehavior.allOrNone, fla := .disallow, items := [{ f := f, indent, activeTags := 0 }]}]
 
 /-- Create a format `l ++ f ++ r` with a flatten group.
 FlattenBehaviour is `allOrNone`; for `fill` use `bracketFill`. -/
@@ -294,7 +317,7 @@ private structure State where
   out    : String := ""
   column : Nat    := 0
 
-instance : MonadPrettyFormat (StateM State) where
+private instance : MonadPrettyFormat (StateM State) where
   -- We avoid a structure instance update, and write these functions using pattern matching because of issue #316
   pushOutput s       := modify fun ⟨out, col⟩ => ⟨out ++ s, col + s.length⟩
   pushNewline indent := modify fun ⟨out, _⟩ => ⟨out ++ "\n".pushn ' ' indent, indent⟩

src/Init/Data/Int/Basic.lean

@@ -269,7 +269,7 @@ set_option bootstrap.genMatcherCode false in
 
   Implemented by efficient native code. -/
 @[extern "lean_int_dec_nonneg"]
-private def decNonneg (m : @& Int) : Decidable (NonNeg m) :=
+def decNonneg (m : @& Int) : Decidable (NonNeg m) :=
   match m with
   | ofNat m => isTrue <| NonNeg.mk m
   | -[_ +1] => isFalse <| fun h => nomatch h

src/Init/Data/Int/Bitwise/Basic.lean

@@ -41,6 +41,7 @@ Examples:
 * `(-0b1000 : Int) >>> 1 = -0b0100`
 * `(-0b0111 : Int) >>> 1 = -0b0100`
 -/
+@[expose]
 protected def shiftRight : Int → Nat → Int
   | Int.ofNat n, s => Int.ofNat (n >>> s)
   | Int.negSucc n, s => Int.negSucc (n >>> s)

src/Init/Data/Int/DivMod/Bootstrap.lean

@@ -3,7 +3,6 @@ Copyright (c) 2016 Jeremy Avigad. All rights reserved.
 Released under Apache 2.0 license as described in the file LICENSE.
 Authors: Jeremy Avigad, Mario Carneiro
 -/
-
 module
 
 prelude
@@ -99,7 +98,7 @@ theorem ofNat_emod (m n : Nat) : (↑(m % n) : Int) = m % n := natCast_emod m n
 theorem emod_add_ediv : ∀ a b : Int, a % b + b * (a / b) = a
   | ofNat _, ofNat _ => congrArg ofNat <| Nat.mod_add_div ..
   | ofNat m, -[n+1] => by
-    show (m % succ n + -↑(succ n) * -↑(m / succ n) : Int) = m
+    change (m % succ n + -↑(succ n) * -↑(m / succ n) : Int) = m
     rw [Int.neg_mul_neg]; exact congrArg ofNat <| Nat.mod_add_div ..
   | -[_+1], 0 => by rw [emod_zero]; rfl
   | -[m+1], succ n => aux m n.succ
@@ -149,7 +148,7 @@ theorem add_mul_ediv_right (a b : Int) {c : Int} (H : c ≠ 0) : (a + b * c) / c
   fun {k n} => @fun
   | ofNat _ => congrArg ofNat <| Nat.add_mul_div_right _ _ k.succ_pos
   | -[m+1] => by
-    show ((n * k.succ : Nat) - m.succ : Int).ediv k.succ = n - (m / k.succ + 1 : Nat)
+    change ((n * k.succ : Nat) - m.succ : Int).ediv k.succ = n - (m / k.succ + 1 : Nat)
     by_cases h : m < n * k.succ
     · rw [← Int.ofNat_sub h, ← Int.ofNat_sub ((Nat.div_lt_iff_lt_mul k.succ_pos).2 h)]
       apply congrArg ofNat
@@ -158,7 +157,7 @@ theorem add_mul_ediv_right (a b : Int) {c : Int} (H : c ≠ 0) : (a + b * c) / c
       have H {a b : Nat} (h : a ≤ b) : (a : Int) + -((b : Int) + 1) = -[b - a +1] := by
         rw [negSucc_eq, Int.ofNat_sub h]
         simp only [Int.sub_eq_add_neg, Int.neg_add, Int.neg_neg, Int.add_left_comm, Int.add_assoc]
-      show ediv (↑(n * succ k) + -((m : Int) + 1)) (succ k) = n + -(↑(m / succ k) + 1 : Int)
+      change ediv (↑(n * succ k) + -((m : Int) + 1)) (succ k) = n + -(↑(m / succ k) + 1 : Int)
       rw [H h, H ((Nat.le_div_iff_mul_le k.succ_pos).2 h)]
       apply congrArg negSucc
       rw [Nat.mul_comm, Nat.sub_mul_div_of_le]; rwa [Nat.mul_comm]
@@ -264,8 +263,8 @@ theorem mul_emod (a b n : Int) : (a * b) % n = (a % n) * (b % n) % n := by
   match k, h with
   | _, ⟨t, rfl⟩ => rw [Int.mul_assoc, add_mul_emod_self_left]
 
-@[simp] theorem emod_emod (a b : Int) : (a % b) % b = a % b := by
-  conv => rhs; rw [← emod_add_ediv a b, add_mul_emod_self_left]
+theorem emod_emod (a b : Int) : (a % b) % b = a % b := by
+  simp
 
 theorem sub_emod (a b n : Int) : (a - b) % n = (a % n - b % n) % n := by
   apply (emod_add_cancel_right b).mp

src/Init/Data/Int/DivMod/Lemmas.lean

@@ -3,7 +3,6 @@ Copyright (c) 2016 Jeremy Avigad. All rights reserved.
 Released under Apache 2.0 license as described in the file LICENSE.
 Authors: Jeremy Avigad, Mario Carneiro, Kim Morrison, Markus Himmel
 -/
-
 module
 
 prelude
@@ -203,6 +202,9 @@ theorem tdiv_eq_ediv_of_nonneg : ∀ {a b : Int}, 0 ≤ a → a.tdiv b = a / b
   | succ _, succ _, _ => rfl
   | succ _, -[_+1], _ => rfl
 
+@[simp] theorem natCast_tdiv_eq_ediv {a : Nat} {b : Int} : (a : Int).tdiv b = a / b :=
+    tdiv_eq_ediv_of_nonneg (by simp)
+
 theorem tdiv_eq_ediv {a b : Int} :
     a.tdiv b = a / b + if 0 ≤ a ∨ b ∣ a then 0 else sign b := by
   simp only [dvd_iff_emod_eq_zero]
@@ -329,17 +331,17 @@ theorem fdiv_eq_ediv_of_dvd {a b : Int} (h : b ∣ a) : a.fdiv b = a / b := by
 theorem tmod_add_tdiv : ∀ a b : Int, tmod a b + b * (a.tdiv b) = a
   | ofNat _, ofNat _ => congrArg ofNat (Nat.mod_add_div ..)
   | ofNat m, -[n+1] => by
-    show (m % succ n + -↑(succ n) * -↑(m / succ n) : Int) = m
+    change (m % succ n + -↑(succ n) * -↑(m / succ n) : Int) = m
     rw [Int.neg_mul_neg]; exact congrArg ofNat (Nat.mod_add_div ..)
   | -[m+1], 0 => by
-    show -(↑((succ m) % 0) : Int) + 0 * -↑(succ m / 0) = -↑(succ m)
+    change -(↑((succ m) % 0) : Int) + 0 * -↑(succ m / 0) = -↑(succ m)
     rw [Nat.mod_zero, Int.zero_mul, Int.add_zero]
   | -[m+1], ofNat n => by
-    show -(↑((succ m) % n) : Int) + ↑n * -↑(succ m / n) = -↑(succ m)
+    change -(↑((succ m) % n) : Int) + ↑n * -↑(succ m / n) = -↑(succ m)
     rw [Int.mul_neg, ← Int.neg_add]
     exact congrArg (-ofNat ·) (Nat.mod_add_div ..)
   | -[m+1], -[n+1] => by
-    show -(↑(succ m % succ n) : Int) + -↑(succ n) * ↑(succ m / succ n) = -↑(succ m)
+    change -(↑(succ m % succ n) : Int) + -↑(succ n) * ↑(succ m / succ n) = -↑(succ m)
     rw [Int.neg_mul, ← Int.neg_add]
     exact congrArg (-ofNat ·) (Nat.mod_add_div ..)
 
@@ -361,17 +363,17 @@ theorem fmod_add_fdiv : ∀ a b : Int, a.fmod b + b * a.fdiv b = a
   | 0, ofNat _ | 0, -[_+1] => congrArg ofNat <| by simp
   | succ _, ofNat _ => congrArg ofNat <| Nat.mod_add_div ..
   | succ m, -[n+1] => by
-    show subNatNat (m % succ n) n + (↑(succ n * (m / succ n)) + n + 1) = (m + 1)
+    change subNatNat (m % succ n) n + (↑(succ n * (m / succ n)) + n + 1) = (m + 1)
     rw [Int.add_comm _ n, ← Int.add_assoc, ← Int.add_assoc,
       Int.subNatNat_eq_coe, Int.sub_add_cancel]
     exact congrArg (ofNat · + 1) <| Nat.mod_add_div ..
   | -[_+1], 0 => by rw [fmod_zero]; rfl
   | -[m+1], succ n => by
-    show subNatNat .. - (↑(succ n * (m / succ n)) + ↑(succ n)) = -↑(succ m)
+    change subNatNat .. - (↑(succ n * (m / succ n)) + ↑(succ n)) = -↑(succ m)
     rw [Int.subNatNat_eq_coe, ← Int.sub_sub, ← Int.neg_sub, Int.sub_sub, Int.sub_sub_self]
     exact congrArg (-ofNat ·) <| Nat.succ_add .. ▸ Nat.mod_add_div .. ▸ rfl
   | -[m+1], -[n+1] => by
-    show -(↑(succ m % succ n) : Int) + -↑(succ n * (succ m / succ n)) = -↑(succ m)
+    change -(↑(succ m % succ n) : Int) + -↑(succ n * (succ m / succ n)) = -↑(succ m)
     rw [← Int.neg_add]; exact congrArg (-ofNat ·) <| Nat.mod_add_div ..
 
 /-- Variant of `fmod_add_fdiv` with the multiplication written the other way around. -/
@@ -572,7 +574,7 @@ theorem neg_one_ediv (b : Int) : -1 / b = -b.sign :=
       · refine Nat.le_trans ?_ (Nat.le_add_right _ _)
         rw [← Nat.mul_div_mul_left _ _ m.succ_pos]
         apply Nat.div_mul_le_self
-      · show m.succ * n.succ ≤ _
+      · change m.succ * n.succ ≤ _
         rw [Nat.mul_left_comm]
         apply Nat.mul_le_mul_left
         apply (Nat.div_lt_iff_lt_mul k.succ_pos).1
@@ -1410,8 +1412,7 @@ theorem mul_tmod (a b n : Int) : (a * b).tmod n = (a.tmod n * b.tmod n).tmod n :
   norm_cast at h
   rw [Nat.mod_mod_of_dvd _ h]
 
-@[simp] theorem tmod_tmod (a b : Int) : (a.tmod b).tmod b = a.tmod b :=
-  tmod_tmod_of_dvd a (Int.dvd_refl b)
+theorem tmod_tmod (a b : Int) : (a.tmod b).tmod b = a.tmod b := by simp
 
 theorem tmod_eq_zero_of_dvd : ∀ {a b : Int}, a ∣ b → tmod b a = 0
   | _, _, ⟨_, rfl⟩ => mul_tmod_right ..
@@ -1469,9 +1470,8 @@ protected theorem tdiv_mul_cancel {a b : Int} (H : b ∣ a) : a.tdiv b * b = a :
 protected theorem mul_tdiv_cancel' {a b : Int} (H : a ∣ b) : a * b.tdiv a = b := by
   rw [Int.mul_comm, Int.tdiv_mul_cancel H]
 
-@[simp] theorem neg_tmod_self (a : Int) : (-a).tmod a = 0 := by
-  rw [← dvd_iff_tmod_eq_zero, Int.dvd_neg]
-  exact Int.dvd_refl a
+theorem neg_tmod_self (a : Int) : (-a).tmod a = 0 := by
+  simp
 
 theorem lt_tdiv_add_one_mul_self (a : Int) {b : Int} (H : 0 < b) : a < (a.tdiv b + 1) * b := by
   rw [Int.add_mul, Int.one_mul, Int.mul_comm]
@@ -1568,13 +1568,11 @@ theorem dvd_tmod_sub_self {x m : Int} : m ∣ x.tmod m - x := by
 theorem dvd_self_sub_tmod {x m : Int} : m ∣ x - x.tmod m :=
   Int.dvd_neg.1 (by simpa only [Int.neg_sub] using dvd_tmod_sub_self)
 
-@[simp] theorem neg_mul_tmod_right (a b : Int) : (-(a * b)).tmod a = 0 := by
-  rw [← dvd_iff_tmod_eq_zero, Int.dvd_neg]
-  exact Int.dvd_mul_right a b
+theorem neg_mul_tmod_right (a b : Int) : (-(a * b)).tmod a = 0 := by
+  simp
 
-@[simp] theorem neg_mul_tmod_left (a b : Int) : (-(a * b)).tmod b = 0 := by
-  rw [← dvd_iff_tmod_eq_zero, Int.dvd_neg]
-  exact Int.dvd_mul_left a b
+theorem neg_mul_tmod_left (a b : Int) : (-(a * b)).tmod b = 0 := by
+  simp
 
 @[simp] protected theorem tdiv_one : ∀ a : Int, a.tdiv 1 = a
   | (n:Nat) => congrArg ofNat (Nat.div_one _)
@@ -2193,8 +2191,8 @@ theorem mul_fmod (a b n : Int) : (a * b).fmod n = (a.fmod n * b.fmod n).fmod n :
   match k, h with
   | _, ⟨t, rfl⟩ => rw [Int.mul_assoc, add_mul_fmod_self_left]
 
-@[simp] theorem fmod_fmod (a b : Int) : (a.fmod b).fmod b = a.fmod b :=
-  fmod_fmod_of_dvd _ (Int.dvd_refl b)
+theorem fmod_fmod (a b : Int) : (a.fmod b).fmod b = a.fmod b := by
+  simp
 
 theorem sub_fmod (a b n : Int) : (a - b).fmod n = (a.fmod n - b.fmod n).fmod n := by
   apply (fmod_add_cancel_right b).mp
@@ -2749,7 +2747,7 @@ theorem bmod_lt {x : Int} {m : Nat} (h : 0 < m) : bmod x m < (m + 1) / 2 := by
   split
   · assumption
   · apply Int.lt_of_lt_of_le
-    · show _ < 0
+    · change _ < 0
       have : x % m < m := emod_lt_of_pos x (natCast_pos.mpr h)
       exact Int.sub_neg_of_lt this
     · exact Int.le.intro_sub _ rfl

src/Init/Data/Int/Gcd.lean

@@ -35,6 +35,7 @@ Examples:
 * `Int.gcd 0 5 = 5`
 * `Int.gcd (-7) 0 = 7`
 -/
+@[expose]
 def gcd (m n : Int) : Nat := m.natAbs.gcd n.natAbs
 
 theorem gcd_eq_natAbs_gcd_natAbs (m n : Int) : gcd m n = Nat.gcd m.natAbs n.natAbs := rfl
@@ -428,6 +429,7 @@ Examples:
  * `Int.lcm 0 3 = 0`
  * `Int.lcm (-3) 0 = 0`
 -/
+@[expose]
 def lcm (m n : Int) : Nat := m.natAbs.lcm n.natAbs
 
 theorem lcm_eq_natAbs_lcm_natAbs (m n : Int) : lcm m n = Nat.lcm m.natAbs n.natAbs := rfl

src/Init/Data/Int/Lemmas.lean

@@ -339,7 +339,7 @@ protected theorem add_sub_assoc (a b c : Int) : a + b - c = a + (b - c) := by
   match m with
   | 0 => rfl
   | succ m =>
-    show ofNat (n - succ m) = subNatNat n (succ m)
+    change ofNat (n - succ m) = subNatNat n (succ m)
     rw [subNatNat, Nat.sub_eq_zero_of_le h]
 
 @[deprecated negSucc_eq (since := "2025-03-11")]

src/Init/Data/Int/Linear.lean

@@ -1665,7 +1665,7 @@ theorem natCast_sub (x y : Nat)
         (NatCast.natCast x : Int) + -1*NatCast.natCast y
       else
         (0 : Int) := by
-  show (↑(x - y) : Int) = if (↑y : Int) + (-1)*↑x ≤ 0 then ↑x + (-1)*↑y else 0
+  change (↑(x - y) : Int) = if (↑y : Int) + (-1)*↑x ≤ 0 then (↑x : Int) + (-1)*↑y else 0
   rw [Int.neg_mul, ← Int.sub_eq_add_neg, Int.one_mul]
   rw [Int.neg_mul, ← Int.sub_eq_add_neg, Int.one_mul]
   split

src/Init/Data/Int/Order.lean

@@ -638,7 +638,7 @@ theorem toNat_of_nonneg {a : Int} (h : 0 ≤ a) : (toNat a : Int) = a := by
 @[simp] theorem toNat_natCast (n : Nat) : toNat ↑n = n := rfl
 
 @[deprecated toNat_natCast (since := "2025-04-16")]
-theorem toNat_ofNat (n : Nat) : toNat ↑n = n := toNat_natCast n
+theorem toNat_ofNat (n : Nat) : toNat ↑n = n := rfl
 
 @[simp] theorem toNat_negSucc (n : Nat) : (Int.negSucc n).toNat = 0 := by
   simp [toNat]

src/Init/Data/Int/Pow.lean

@@ -19,6 +19,13 @@ protected theorem pow_succ (b : Int) (e : Nat) : b ^ (e+1) = (b ^ e) * b := rfl
 protected theorem pow_succ' (b : Int) (e : Nat) : b ^ (e+1) = b * (b ^ e) := by
   rw [Int.mul_comm, Int.pow_succ]
 
+protected theorem zero_pow {n : Nat} (h : n ≠ 0) : (0 : Int) ^ n = 0 := by
+  match n, h with
+  | n + 1, _ => simp [Int.pow_succ]
+
+protected theorem one_pow {n : Nat} : (1 : Int) ^ n = 1 := by
+  induction n with simp_all [Int.pow_succ]
+
 protected theorem pow_pos {n : Int} {m : Nat} : 0 < n → 0 < n ^ m := by
   induction m with
   | zero => simp

src/Init/Data/List/Attach.lean

@@ -23,6 +23,7 @@ a list `l : List α`, given a proof that every element of `l` in fact satisfies
 `O(|l|)`. `List.pmap`, named for “partial map,” is the equivalent of `List.map` for such partial
 functions.
 -/
+@[expose]
 def pmap {P : α → Prop} (f : ∀ a, P a → β) : ∀ l : List α, (H : ∀ a ∈ l, P a) → List β
   | [], _ => []
   | a :: l, H => f a (forall_mem_cons.1 H).1 :: pmap f l (forall_mem_cons.1 H).2
@@ -40,7 +41,7 @@ elements in the corresponding subtype `{ x // P x }`.
 
 `O(1)`.
 -/
-@[implemented_by attachWithImpl] def attachWith
+@[implemented_by attachWithImpl, expose] def attachWith
     (l : List α) (P : α → Prop) (H : ∀ x ∈ l, P x) : List {x // P x} := pmap Subtype.mk l H
 
 /--
@@ -54,7 +55,7 @@ recursion](lean-manual://section/well-founded-recursion) that use higher-order f
 `List.map`) to prove that an value taken from a list is smaller than the list. This allows the
 well-founded recursion mechanism to prove that the function terminates.
 -/
-@[inline] def attach (l : List α) : List {x // x ∈ l} := attachWith l _ fun _ => id
+@[inline, expose] def attach (l : List α) : List {x // x ∈ l} := attachWith l _ fun _ => id
 
 /-- Implementation of `pmap` using the zero-copy version of `attach`. -/
 @[inline] private def pmapImpl {P : α → Prop} (f : ∀ a, P a → β) (l : List α) (H : ∀ a ∈ l, P a) :
@@ -675,6 +676,7 @@ the elaboration of definitions by [well-founded
 recursion](lean-manual://section/well-founded-recursion). If this function is encountered in a proof
 state, the right approach is usually the tactic `simp [List.unattach, -List.map_subtype]`.
 -/
+@[expose]
 def unattach {α : Type _} {p : α → Prop} (l : List { x // p x }) : List α := l.map (·.val)
 
 @[simp] theorem unattach_nil {p : α → Prop} : ([] : List { x // p x }).unattach = [] := rfl

src/Init/Data/List/Basic.lean

@@ -9,6 +9,7 @@ prelude
 import Init.SimpLemmas
 import Init.Data.Nat.Basic
 import Init.Data.List.Notation
+import Init.Data.Nat.Div.Basic
 
 @[expose] section
 
@@ -586,7 +587,7 @@ Examples:
 * `[1, 2, 3, 4].reverse = [4, 3, 2, 1]`
 * `[].reverse = []`
 -/
-def reverse (as : List α) : List α :=
+@[expose] def reverse (as : List α) : List α :=
   reverseAux as []
 
 @[simp, grind] theorem reverse_nil : reverse ([] : List α) = [] := rfl
@@ -672,7 +673,7 @@ instance : Std.Associative (α := List α) (· ++ ·) := ⟨append_assoc⟩
 theorem append_cons (as : List α) (b : α) (bs : List α) : as ++ b :: bs = as ++ [b] ++ bs := by
   simp
 
-@[simp] theorem concat_eq_append {as : List α} {a : α} : as.concat a = as ++ [a] := by
+@[simp, grind =] theorem concat_eq_append {as : List α} {a : α} : as.concat a = as ++ [a] := by
   induction as <;> simp [concat, *]
 
 theorem reverseAux_eq_append {as bs : List α} : reverseAux as bs = reverseAux as [] ++ bs := by
@@ -715,7 +716,7 @@ Examples:
  * `List.singleton "green" = ["green"]`.
  * `List.singleton [1, 2, 3] = [[1, 2, 3]]`
 -/
-@[inline] protected def singleton {α : Type u} (a : α) : List α := [a]
+@[inline, expose] protected def singleton {α : Type u} (a : α) : List α := [a]
 
 /-! ### flatMap -/
 
@@ -1190,10 +1191,10 @@ def isPrefixOf [BEq α] : List α → List α → Bool
   | _,     []    => false
   | a::as, b::bs => a == b && isPrefixOf as bs
 
-@[simp] theorem isPrefixOf_nil_left [BEq α] : isPrefixOf ([] : List α) l = true := by
+@[simp, grind =] theorem isPrefixOf_nil_left [BEq α] : isPrefixOf ([] : List α) l = true := by
   simp [isPrefixOf]
-@[simp] theorem isPrefixOf_cons_nil [BEq α] : isPrefixOf (a::as) ([] : List α) = false := rfl
-theorem isPrefixOf_cons₂ [BEq α] {a : α} :
+@[simp, grind =] theorem isPrefixOf_cons_nil [BEq α] : isPrefixOf (a::as) ([] : List α) = false := rfl
+@[grind =] theorem isPrefixOf_cons₂ [BEq α] {a : α} :
     isPrefixOf (a::as) (b::bs) = (a == b && isPrefixOf as bs) := rfl
 
 /--
@@ -1229,7 +1230,7 @@ Examples:
 def isSuffixOf [BEq α] (l₁ l₂ : List α) : Bool :=
   isPrefixOf l₁.reverse l₂.reverse
 
-@[simp] theorem isSuffixOf_nil_left [BEq α] : isSuffixOf ([] : List α) l = true := by
+@[simp, grind =] theorem isSuffixOf_nil_left [BEq α] : isSuffixOf ([] : List α) l = true := by
   simp [isSuffixOf]
 
 /--
@@ -1564,8 +1565,8 @@ protected def erase {α} [BEq α] : List α → α → List α
     | true  => as
     | false => a :: List.erase as b
 
-@[simp] theorem erase_nil [BEq α] (a : α) : [].erase a = [] := rfl
-theorem erase_cons [BEq α] {a b : α} {l : List α} :
+@[simp, grind =] theorem erase_nil [BEq α] (a : α) : [].erase a = [] := rfl
+@[grind =] theorem erase_cons [BEq α] {a b : α} {l : List α} :
     (b :: l).erase a = if b == a then l else b :: l.erase a := by
   simp only [List.erase]; split <;> simp_all
 
@@ -1624,8 +1625,8 @@ def find? (p : α → Bool) : List α → Option α
     | true  => some a
     | false => find? p as
 
-@[simp] theorem find?_nil : ([] : List α).find? p = none := rfl
-theorem find?_cons : (a::as).find? p = match p a with | true => some a | false => as.find? p :=
+@[simp, grind =] theorem find?_nil : ([] : List α).find? p = none := rfl
+@[grind =]theorem find?_cons : (a::as).find? p = match p a with | true => some a | false => as.find? p :=
   rfl
 
 /-! ### findSome? -/
@@ -1845,8 +1846,8 @@ def lookup [BEq α] : α → List (α × β) → Option β
     | true  => some b
     | false => lookup a as
 
-@[simp] theorem lookup_nil [BEq α] : ([] : List (α × β)).lookup a = none := rfl
-theorem lookup_cons [BEq α] {k : α} :
+@[simp, grind =] theorem lookup_nil [BEq α] : ([] : List (α × β)).lookup a = none := rfl
+@[grind =] theorem lookup_cons [BEq α] {k : α} :
     ((k, b)::as).lookup a = match a == k with | true => some b | false => as.lookup a :=
   rfl
 
@@ -2096,7 +2097,7 @@ where
   | 0,   acc => acc
   | n+1, acc => loop n (n::acc)
 
-@[simp] theorem range_zero : range 0 = [] := rfl
+@[simp, grind =] theorem range_zero : range 0 = [] := rfl
 
 /-! ### range' -/
 

src/Init/Data/List/BasicAux.lean

@@ -27,7 +27,7 @@ Returns the `i`-th element in the list (zero-based).
 If the index is out of bounds (`i ≥ as.length`), this function returns `none`.
 Also see `get`, `getD` and `get!`.
 -/
-@[deprecated "Use `a[i]?` instead." (since := "2025-02-12")]
+@[deprecated "Use `a[i]?` instead." (since := "2025-02-12"), expose]
 def get? : (as : List α) → (i : Nat) → Option α
   | a::_,  0   => some a
   | _::as, n+1 => get? as n
@@ -61,7 +61,7 @@ Returns the `i`-th element in the list (zero-based).
 If the index is out of bounds (`i ≥ as.length`), this function panics when executed, and returns
 `default`. See `get?` and `getD` for safer alternatives.
 -/
-@[deprecated "Use `a[i]!` instead." (since := "2025-02-12")]
+@[deprecated "Use `a[i]!` instead." (since := "2025-02-12"), expose]
 def get! [Inhabited α] : (as : List α) → (i : Nat) → α
   | a::_,  0   => a
   | _::as, n+1 => get! as n
@@ -92,7 +92,7 @@ Examples:
  * `["spring", "summer", "fall", "winter"].getD 0 "never" = "spring"`
  * `["spring", "summer", "fall", "winter"].getD 4 "never" = "never"`
 -/
-def getD (as : List α) (i : Nat) (fallback : α) : α :=
+@[expose] def getD (as : List α) (i : Nat) (fallback : α) : α :=
   as[i]?.getD fallback
 
 @[simp] theorem getD_nil : getD [] n d = d := rfl
@@ -111,6 +111,7 @@ Examples:
  * `["circle", "rectangle"].getLast! = "rectangle"`
  * `["circle"].getLast! = "circle"`
 -/
+@[expose]
 def getLast! [Inhabited α] : List α → α
   | []    => panic! "empty list"
   | a::as => getLast (a::as) (fun h => List.noConfusion h)
@@ -146,7 +147,7 @@ Examples:
  * `["apple", "banana", "grape"].tail! = ["banana", "grape"]`
  * `["banana", "grape"].tail! = ["grape"]`
 -/
-def tail! : List α → List α
+@[expose] def tail! : List α → List α
   | []    => panic! "empty list"
   | _::as => as
 
@@ -254,7 +255,7 @@ pointer-equal to its argument.
 For verification purposes, `List.mapMono = List.map`.
 -/
 def mapMono (as : List α) (f : α → α) : List α :=
-  Id.run <| as.mapMonoM f
+  Id.run <| as.mapMonoM (pure <| f ·)
 
 /-! ## Additional lemmas required for bootstrapping `Array`. -/
 

src/Init/Data/List/Control.lean

@@ -54,7 +54,7 @@ This implementation is tail recursive. `List.mapM'` is a a non-tail-recursive va
 more convenient to reason about. `List.forM` is the variant that discards the results and
 `List.mapA` is the variant that works with `Applicative`.
 -/
-@[inline]
+@[inline, expose]
 def mapM {m : Type u → Type v} [Monad m] {α : Type w} {β : Type u} (f : α → m β) (as : List α) : m (List β) :=
   let rec @[specialize] loop
     | [],      bs => pure bs.reverse
@@ -83,7 +83,7 @@ Applies the monadic action `f` to every element in the list, in order.
 `List.mapM` is a variant that collects results. `List.forA` is a variant that works on any
 `Applicative`.
 -/
-@[specialize]
+@[specialize, expose]
 protected def forM {m : Type u → Type v} [Monad m] {α : Type w} (as : List α) (f : α → m PUnit) : m PUnit :=
   match as with
   | []      => pure ⟨⟩
@@ -191,7 +191,7 @@ Examining 7
 [10, 14, 14]
 ```
 -/
-@[inline]
+@[inline, expose]
 def filterMapM {m : Type u → Type v} [Monad m] {α : Type w} {β : Type u} (f : α → m (Option β)) (as : List α) : m (List β) :=
   let rec @[specialize] loop
     | [],     bs => pure bs.reverse
@@ -205,7 +205,7 @@ def filterMapM {m : Type u → Type v} [Monad m] {α : Type w} {β : Type u} (f
 Applies a monadic function that returns a list to each element of a list, from left to right, and
 concatenates the resulting lists.
 -/
-@[inline]
+@[inline, expose]
 def flatMapM {m : Type u → Type v} [Monad m] {α : Type w} {β : Type u} (f : α → m (List β)) (as : List α) : m (List β) :=
   let rec @[specialize] loop
     | [],     bs => pure bs.reverse.flatten
@@ -230,7 +230,7 @@ example [Monad m] (f : α → β → m α) :
   := by rfl
 ```
 -/
-@[specialize]
+@[specialize, expose]
 def foldlM {m : Type u → Type v} [Monad m] {s : Type u} {α : Type w} : (f : s → α → m s) → (init : s) → List α → m s
   | _, s, []      => pure s
   | f, s, a :: as => do
@@ -257,7 +257,7 @@ example [Monad m] (f : α → β → m β) :
   := by rfl
 ```
 -/
-@[inline]
+@[inline, expose]
 def foldrM {m : Type u → Type v} [Monad m] {s : Type u} {α : Type w} (f : α → s → m s) (init : s) (l : List α) : m s :=
   l.reverse.foldlM (fun s a => f a s) init
 
@@ -348,9 +348,16 @@ theorem findM?_pure {m} [Monad m] [LawfulMonad m] (p : α → Bool) (as : List
     | false => simp [ih]
 
 @[simp]
-theorem findM?_id (p : α → Bool) (as : List α) : findM? (m := Id) p as = as.find? p :=
+theorem idRun_findM? (p : α → Id Bool) (as : List α) :
+    (findM? p as).run = as.find? (p · |>.run) :=
   findM?_pure _ _
 
+@[deprecated idRun_findM? (since := "2025-05-21")]
+theorem findM?_id (p : α → Id Bool) (as : List α) :
+    findM? (m := Id) p as = as.find? p :=
+  findM?_pure _ _
+
+
 /--
 Returns the first non-`none` result of applying the monadic function `f` to each element of the
 list, in order. Returns `none` if `f` returns `none` for all elements.
@@ -394,7 +401,13 @@ theorem findSomeM?_pure [Monad m] [LawfulMonad m] {f : α → Option β} {as : L
     | none   => simp [ih]
 
 @[simp]
-theorem findSomeM?_id {f : α → Option β} {as : List α} : findSomeM? (m := Id) f as = as.findSome? f :=
+theorem idRun_findSomeM? (f : α → Id (Option β)) (as : List α) :
+    (findSomeM? f as).run = as.findSome? (f · |>.run) :=
+  findSomeM?_pure
+
+@[deprecated idRun_findSomeM? (since := "2025-05-21")]
+theorem findSomeM?_id (f : α → Id (Option β)) (as : List α) :
+    findSomeM? (m := Id) f as = as.findSome? f :=
   findSomeM?_pure
 
 theorem findM?_eq_findSomeM? [Monad m] [LawfulMonad m] {p : α → m Bool} {as : List α} :
@@ -409,7 +422,7 @@ theorem findM?_eq_findSomeM? [Monad m] [LawfulMonad m] {p : α → m Bool} {as :
     intro b
     cases b <;> simp
 
-@[inline] protected def forIn' {α : Type u} {β : Type v} {m : Type v → Type w} [Monad m] (as : List α) (init : β) (f : (a : α) → a ∈ as → β → m (ForInStep β)) : m β :=
+@[inline, expose] protected def forIn' {α : Type u} {β : Type v} {m : Type v → Type w} [Monad m] (as : List α) (init : β) (f : (a : α) → a ∈ as → β → m (ForInStep β)) : m β :=
   let rec @[specialize] loop : (as' : List α) → (b : β) → Exists (fun bs => bs ++ as' = as) → m β
     | [], b, _    => pure b
     | a::as', b, h => do

src/Init/Data/List/Count.lean

@@ -10,6 +10,9 @@ import Init.Data.List.Sublist
 
 /-!
 # Lemmas about `List.countP` and `List.count`.
+
+Because we mark `countP_eq_length_filter` and `count_eq_countP` with `@[grind _=_]`,
+we don't need many other `@[grind]` annotations here.
 -/
 
 set_option linter.listVariables true -- Enforce naming conventions for `List`/`Array`/`Vector` variables.
@@ -61,7 +64,8 @@ theorem length_eq_countP_add_countP (p : α → Bool) {l : List α} : length l =
       · rfl
       · simp [h]
 
-theorem countP_eq_length_filter {l : List α} : countP p l = length (filter p l) := by
+@[grind _=_]  -- This to quite aggressive, as it introduces `filter` based reasoning whenever we see `countP`.
+theorem countP_eq_length_filter {l : List α} : countP p l = (filter p l).length := by
   induction l with
   | nil => rfl
   | cons x l ih =>
@@ -69,6 +73,7 @@ theorem countP_eq_length_filter {l : List α} : countP p l = length (filter p l)
     then rw [countP_cons_of_pos h, ih, filter_cons_of_pos h, length]
     else rw [countP_cons_of_neg h, ih, filter_cons_of_neg h]
 
+@[grind =]
 theorem countP_eq_length_filter' : countP p = length ∘ filter p := by
   funext l
   apply countP_eq_length_filter
@@ -77,7 +82,7 @@ theorem countP_le_length : countP p l ≤ l.length := by
   simp only [countP_eq_length_filter]
   apply length_filter_le
 
-@[simp] theorem countP_append {l₁ l₂ : List α} : countP p (l₁ ++ l₂) = countP p l₁ + countP p l₂ := by
+@[simp, grind =] theorem countP_append {l₁ l₂ : List α} : countP p (l₁ ++ l₂) = countP p l₁ + countP p l₂ := by
   simp only [countP_eq_length_filter, filter_append, length_append]
 
 @[simp] theorem countP_pos_iff {p} : 0 < countP p l ↔ ∃ a ∈ l, p a := by
@@ -97,6 +102,7 @@ theorem countP_replicate {p : α → Bool} {a : α} {n : Nat} :
   simp only [countP_eq_length_filter, filter_replicate]
   split <;> simp
 
+@[grind]
 theorem boole_getElem_le_countP {p : α → Bool} {l : List α} {i : Nat} (h : i < l.length) :
     (if p l[i] then 1 else 0) ≤ l.countP p := by
   induction l generalizing i with
@@ -114,12 +120,27 @@ theorem Sublist.countP_le (s : l₁ <+ l₂) : countP p l₁ ≤ countP p l₂ :
   simp only [countP_eq_length_filter]
   apply s.filter _ |>.length_le
 
+grind_pattern Sublist.countP_le => l₁ <+ l₂, countP p l₁
+grind_pattern Sublist.countP_le => l₁ <+ l₂, countP p l₂
+
 theorem IsPrefix.countP_le (s : l₁ <+: l₂) : countP p l₁ ≤ countP p l₂ := s.sublist.countP_le
+
+grind_pattern IsPrefix.countP_le => l₁ <+: l₂, countP p l₁
+grind_pattern IsPrefix.countP_le => l₁ <+: l₂, countP p l₂
+
 theorem IsSuffix.countP_le (s : l₁ <:+ l₂) : countP p l₁ ≤ countP p l₂ := s.sublist.countP_le
+
+grind_pattern IsSuffix.countP_le => l₁ <:+ l₂, countP p l₁
+grind_pattern IsSuffix.countP_le => l₁ <:+ l₂, countP p l₂
+
 theorem IsInfix.countP_le (s : l₁ <:+: l₂) : countP p l₁ ≤ countP p l₂ := s.sublist.countP_le
 
+grind_pattern IsInfix.countP_le => l₁ <:+: l₂, countP p l₁
+grind_pattern IsInfix.countP_le => l₁ <:+: l₂, countP p l₂
+
 -- See `Init.Data.List.Nat.Count` for `Sublist.le_countP : countP p l₂ - (l₂.length - l₁.length) ≤ countP p l₁`.
 
+@[grind]
 theorem countP_tail_le (l) : countP p l.tail ≤ countP p l :=
   (tail_sublist l).countP_le
 
@@ -167,7 +188,7 @@ theorem countP_flatMap {p : β → Bool} {l : List α} {f : α → List β} :
     countP p (l.flatMap f) = sum (map (countP p ∘ f) l) := by
   rw [List.flatMap, countP_flatten, map_map]
 
-@[simp] theorem countP_reverse {l : List α} : countP p l.reverse = countP p l := by
+@[simp, grind =] theorem countP_reverse {l : List α} : countP p l.reverse = countP p l := by
   simp [countP_eq_length_filter, filter_reverse]
 
 theorem countP_mono_left (h : ∀ x ∈ l, p x → q x) : countP p l ≤ countP q l := by
@@ -196,8 +217,9 @@ section count
 
 variable [BEq α]
 
-@[simp] theorem count_nil {a : α} : count a [] = 0 := rfl
+@[simp, grind =] theorem count_nil {a : α} : count a [] = 0 := rfl
 
+@[grind]
 theorem count_cons {a b : α} {l : List α} :
     count a (b :: l) = count a l + if b == a then 1 else 0 := by
   simp [count, countP_cons]
@@ -207,18 +229,40 @@ theorem count_eq_countP' {a : α} : count a = countP (· == a) := by
   funext l
   apply count_eq_countP
 
-theorem count_tail : ∀ {l : List α} (h : l ≠ []) (a : α),
-      l.tail.count a = l.count a - if l.head h == a then 1 else 0
-  | _ :: _, a, _ => by simp [count_cons]
+@[grind =]
+theorem count_eq_length_filter {a : α} {l : List α} : count a l = (filter (· == a) l).length := by
+  simp [count, countP_eq_length_filter]
+
+@[grind]
+theorem count_tail : ∀ {l : List α} {a : α},
+      l.tail.count a = l.count a - if l.head? == some a then 1 else 0
+  | [], a => by simp
+  | _ :: _, a => by simp [count_cons]
 
 theorem count_le_length {a : α} {l : List α} : count a l ≤ l.length := countP_le_length
 
+grind_pattern count_le_length => count a l
+
 theorem Sublist.count_le (a : α) (h : l₁ <+ l₂) : count a l₁ ≤ count a l₂ := h.countP_le
 
+grind_pattern Sublist.count_le => l₁ <+ l₂, count a l₁
+grind_pattern Sublist.count_le => l₁ <+ l₂, count a l₂
+
 theorem IsPrefix.count_le (a : α) (h : l₁ <+: l₂) : count a l₁ ≤ count a l₂ := h.sublist.count_le a
+
+grind_pattern IsPrefix.count_le => l₁ <+: l₂, count a l₁
+grind_pattern IsPrefix.count_le => l₁ <+: l₂, count a l₂
+
 theorem IsSuffix.count_le (a : α) (h : l₁ <:+ l₂) : count a l₁ ≤ count a l₂ := h.sublist.count_le a
+
+grind_pattern IsSuffix.count_le => l₁ <:+ l₂, count a l₁
+grind_pattern IsSuffix.count_le => l₁ <:+ l₂, count a l₂
+
 theorem IsInfix.count_le (a : α) (h : l₁ <:+: l₂) : count a l₁ ≤ count a l₂ := h.sublist.count_le a
 
+grind_pattern IsInfix.count_le => l₁ <:+: l₂, count a l₁
+grind_pattern IsInfix.count_le => l₁ <:+: l₂, count a l₂
+
 -- See `Init.Data.List.Nat.Count` for `Sublist.le_count : count a l₂ - (l₂.length - l₁.length) ≤ countP a l₁`.
 
 theorem count_tail_le {a : α} {l : List α} : count a l.tail ≤ count a l :=
@@ -232,15 +276,17 @@ theorem count_le_count_cons {a b : α} {l : List α} : count a l ≤ count a (b
 theorem count_singleton {a b : α} : count a [b] = if b == a then 1 else 0 := by
   simp [count_cons]
 
-@[simp] theorem count_append {a : α} {l₁ l₂ : List α} : count a (l₁ ++ l₂) = count a l₁ + count a l₂ :=
+@[simp, grind =] theorem count_append {a : α} {l₁ l₂ : List α} : count a (l₁ ++ l₂) = count a l₁ + count a l₂ :=
   countP_append
 
+@[grind =]
 theorem count_flatten {a : α} {l : List (List α)} : count a l.flatten = (l.map (count a)).sum := by
   simp only [count_eq_countP, countP_flatten, count_eq_countP']
 
-@[simp] theorem count_reverse {a : α} {l : List α} : count a l.reverse = count a l := by
+@[simp, grind =] theorem count_reverse {a : α} {l : List α} : count a l.reverse = count a l := by
   simp only [count_eq_countP, countP_eq_length_filter, filter_reverse, length_reverse]
 
+@[grind]
 theorem boole_getElem_le_count {a : α} {l : List α} {i : Nat} (h : i < l.length) :
     (if l[i] == a then 1 else 0) ≤ l.count a := by
   rw [count_eq_countP]
@@ -283,7 +329,7 @@ theorem count_eq_length {l : List α} : count a l = l.length ↔ ∀ b ∈ l, a
 @[simp] theorem count_replicate_self {a : α} {n : Nat} : count a (replicate n a) = n :=
   (count_eq_length.2 <| fun _ h => (eq_of_mem_replicate h).symm).trans (length_replicate ..)
 
-theorem count_replicate {a b : α} {n : Nat} : count a (replicate n b) = if b == a then n else 0 := by
+@[grind =] theorem count_replicate {a b : α} {n : Nat} : count a (replicate n b) = if b == a then n else 0 := by
   split <;> (rename_i h; simp only [beq_iff_eq] at h)
   · exact ‹b = a› ▸ count_replicate_self ..
   · exact count_eq_zero.2 <| mt eq_of_mem_replicate (Ne.symm h)
@@ -295,14 +341,18 @@ theorem filter_beq {l : List α} (a : α) : l.filter (· == a) = replicate (coun
 theorem filter_eq [DecidableEq α] {l : List α} (a : α) : l.filter (· = a) = replicate (count a l) a :=
   funext (Bool.beq_eq_decide_eq · a) ▸ filter_beq a
 
-theorem le_count_iff_replicate_sublist {l : List α} : n ≤ count a l ↔ replicate n a <+ l := by
+@[grind =] theorem replicate_sublist_iff {l : List α} : replicate n a <+ l ↔ n ≤ count a l := by
   refine ⟨fun h => ?_, fun h => ?_⟩
-  · exact ((replicate_sublist_replicate a).2 h).trans <| filter_beq a ▸ filter_sublist
   · simpa only [count_replicate_self] using h.count_le a
+  · exact ((replicate_sublist_replicate a).2 h).trans <| filter_beq a ▸ filter_sublist
+
+@[deprecated replicate_sublist_iff (since := "2025-05-26")]
+theorem le_count_iff_replicate_sublist {l : List α} : n ≤ count a l ↔ replicate n a <+ l :=
+  replicate_sublist_iff.symm
 
 theorem replicate_count_eq_of_count_eq_length {l : List α} (h : count a l = length l) :
     replicate (count a l) a = l :=
-  (le_count_iff_replicate_sublist.mp (Nat.le_refl _)).eq_of_length <| length_replicate.trans h
+  (replicate_sublist_iff.mpr (Nat.le_refl _)).eq_of_length <| length_replicate.trans h
 
 @[simp] theorem count_filter {l : List α} (h : p a) : count a (filter p l) = count a l := by
   rw [count, countP_filter]; congr; funext b
@@ -325,6 +375,7 @@ theorem count_filterMap {α} [BEq β] {b : β} {f : α → Option β} {l : List
 theorem count_flatMap {α} [BEq β] {l : List α} {f : α → List β} {x : β} :
     count x (l.flatMap f) = sum (map (count x ∘ f) l) := countP_flatMap
 
+@[grind]
 theorem count_erase {a b : α} :
     ∀ {l : List α}, count a (l.erase b) = count a l - if b == a then 1 else 0
   | [] => by simp

src/Init/Data/List/Erase.lean

@@ -23,9 +23,9 @@ open Nat
 
 /-! ### eraseP -/
 
-@[simp] theorem eraseP_nil : [].eraseP p = [] := rfl
+@[simp, grind =] theorem eraseP_nil : [].eraseP p = [] := rfl
 
-theorem eraseP_cons {a : α} {l : List α} :
+@[grind =] theorem eraseP_cons {a : α} {l : List α} :
     (a :: l).eraseP p = bif p a then l else a :: l.eraseP p := rfl
 
 @[simp] theorem eraseP_cons_of_pos {l : List α} {p} (h : p a) : (a :: l).eraseP p = l := by
@@ -92,7 +92,7 @@ theorem exists_or_eq_self_of_eraseP (p) (l : List α) :
   let ⟨_, l₁, l₂, _, _, e₁, e₂⟩ := exists_of_eraseP al pa
   rw [e₂]; simp [length_append, e₁]
 
-theorem length_eraseP {l : List α} : (l.eraseP p).length = if l.any p then l.length - 1 else l.length := by
+@[grind =] theorem length_eraseP {l : List α} : (l.eraseP p).length = if l.any p then l.length - 1 else l.length := by
   split <;> rename_i h
   · simp only [any_eq_true] at h
     obtain ⟨x, m, h⟩ := h
@@ -106,8 +106,13 @@ theorem eraseP_sublist {l : List α} : l.eraseP p <+ l := by
   | .inl h => rw [h]; apply Sublist.refl
   | .inr ⟨c, l₁, l₂, _, _, h₃, h₄⟩ => rw [h₄, h₃]; simp
 
+grind_pattern eraseP_sublist => l.eraseP p, List.Sublist
+
 theorem eraseP_subset {l : List α} : l.eraseP p ⊆ l := eraseP_sublist.subset
 
+grind_pattern eraseP_subset => l.eraseP p, List.Subset
+
+@[grind ←]
 protected theorem Sublist.eraseP : l₁ <+ l₂ → l₁.eraseP p <+ l₂.eraseP p
   | .slnil => Sublist.refl _
   | .cons a s => by
@@ -126,9 +131,10 @@ theorem le_length_eraseP {l : List α} : l.length - 1 ≤ (l.eraseP p).length :=
   rw [length_eraseP]
   split <;> simp
 
+@[grind →]
 theorem mem_of_mem_eraseP {l : List α} : a ∈ l.eraseP p → a ∈ l := (eraseP_subset ·)
 
-@[simp] theorem mem_eraseP_of_neg {l : List α} (pa : ¬p a) : a ∈ l.eraseP p ↔ a ∈ l := by
+@[simp, grind] theorem mem_eraseP_of_neg {l : List α} (pa : ¬p a) : a ∈ l.eraseP p ↔ a ∈ l := by
   refine ⟨mem_of_mem_eraseP, fun al => ?_⟩
   match exists_or_eq_self_of_eraseP p l with
   | .inl h => rw [h]; assumption
@@ -146,10 +152,12 @@ theorem mem_of_mem_eraseP {l : List α} : a ∈ l.eraseP p → a ∈ l := (erase
     · intro; obtain ⟨x, m, h⟩ := h; simp_all
   · simp_all
 
+@[grind _=_]
 theorem eraseP_map {f : β → α} : ∀ {l : List β}, (map f l).eraseP p = map f (l.eraseP (p ∘ f))
   | [] => rfl
   | b::l => by by_cases h : p (f b) <;> simp [h, eraseP_map, eraseP_cons_of_pos]
 
+@[grind =]
 theorem eraseP_filterMap {f : α → Option β} : ∀ {l : List α},
     (filterMap f l).eraseP p = filterMap f (l.eraseP (fun x => match f x with | some y => p y | none => false))
   | [] => rfl
@@ -164,6 +172,7 @@ theorem eraseP_filterMap {f : α → Option β} : ∀ {l : List α},
       · simp only [w, cond_false]
         rw [filterMap_cons_some h, eraseP_filterMap]
 
+@[grind =]
 theorem eraseP_filter {f : α → Bool} {l : List α} :
     (filter f l).eraseP p = filter f (l.eraseP (fun x => p x && f x)) := by
   rw [← filterMap_eq_filter, eraseP_filterMap]
@@ -173,18 +182,19 @@ theorem eraseP_filter {f : α → Bool} {l : List α} :
   split <;> split at * <;> simp_all
 
 theorem eraseP_append_left {a : α} (pa : p a) :
-    ∀ {l₁ : List α} l₂, a ∈ l₁ → (l₁++l₂).eraseP p = l₁.eraseP p ++ l₂
+    ∀ {l₁ : List α} l₂, a ∈ l₁ → (l₁ ++ l₂).eraseP p = l₁.eraseP p ++ l₂
   | x :: xs, l₂, h => by
     by_cases h' : p x <;> simp [h']
     rw [eraseP_append_left pa l₂ ((mem_cons.1 h).resolve_left (mt _ h'))]
     intro | rfl => exact pa
 
 theorem eraseP_append_right :
-    ∀ {l₁ : List α} l₂, (∀ b ∈ l₁, ¬p b) → eraseP p (l₁++l₂) = l₁ ++ l₂.eraseP p
+    ∀ {l₁ : List α} l₂, (∀ b ∈ l₁, ¬p b) → eraseP p (l₁ ++ l₂) = l₁ ++ l₂.eraseP p
   | [],     _, _ => rfl
   | _ :: _, _, h => by
     simp [(forall_mem_cons.1 h).1, eraseP_append_right _ (forall_mem_cons.1 h).2]
 
+@[grind =]
 theorem eraseP_append {l₁ l₂ : List α} :
     (l₁ ++ l₂).eraseP p = if l₁.any p then l₁.eraseP p ++ l₂ else l₁ ++ l₂.eraseP p := by
   split <;> rename_i h
@@ -195,6 +205,7 @@ theorem eraseP_append {l₁ l₂ : List α} :
     rw [eraseP_append_right _]
     simp_all
 
+@[grind =]
 theorem eraseP_replicate {n : Nat} {a : α} {p : α → Bool} :
     (replicate n a).eraseP p = if p a then replicate (n - 1) a else replicate n a := by
   induction n with
@@ -211,6 +222,7 @@ theorem eraseP_replicate {n : Nat} {a : α} {p : α → Bool} :
     (replicate n a).eraseP p = replicate n a := by
   rw [eraseP_of_forall_not (by simp_all)]
 
+@[grind ←]
 protected theorem IsPrefix.eraseP (h : l₁ <+: l₂) : l₁.eraseP p <+: l₂.eraseP p := by
   rw [IsPrefix] at h
   obtain ⟨t, rfl⟩ := h
@@ -257,12 +269,15 @@ theorem eraseP_eq_iff {p} {l : List α} :
         subst p
         simp_all
 
+@[grind ←]
 theorem Pairwise.eraseP (q) : Pairwise p l → Pairwise p (l.eraseP q) :=
   Pairwise.sublist <| eraseP_sublist
 
+@[grind ←]
 theorem Nodup.eraseP (p) : Nodup l → Nodup (l.eraseP p) :=
   Pairwise.eraseP p
 
+@[grind =]
 theorem eraseP_comm {l : List α} (h : ∀ a ∈ l, ¬ p a ∨ ¬ q a) :
     (l.eraseP p).eraseP q = (l.eraseP q).eraseP p := by
   induction l with
@@ -355,6 +370,7 @@ theorem exists_erase_eq [LawfulBEq α] {a : α} {l : List α} (h : a ∈ l) :
     length (l.erase a) = length l - 1 := by
   rw [erase_eq_eraseP]; exact length_eraseP_of_mem h (beq_self_eq_true a)
 
+@[grind =]
 theorem length_erase [LawfulBEq α] {a : α} {l : List α} :
     length (l.erase a) = if a ∈ l then length l - 1 else length l := by
   rw [erase_eq_eraseP, length_eraseP]
@@ -363,11 +379,17 @@ theorem length_erase [LawfulBEq α] {a : α} {l : List α} :
 theorem erase_sublist {a : α} {l : List α} : l.erase a <+ l :=
   erase_eq_eraseP' a l ▸ eraseP_sublist ..
 
+grind_pattern length_erase => l.erase a, List.Sublist
+
 theorem erase_subset {a : α} {l : List α} : l.erase a ⊆ l := erase_sublist.subset
 
+grind_pattern erase_subset => l.erase a, List.Subset
+
+@[grind ←]
 theorem Sublist.erase (a : α) {l₁ l₂ : List α} (h : l₁ <+ l₂) : l₁.erase a <+ l₂.erase a := by
   simp only [erase_eq_eraseP']; exact h.eraseP
 
+@[grind ←]
 theorem IsPrefix.erase (a : α) {l₁ l₂ : List α} (h : l₁ <+: l₂) : l₁.erase a <+: l₂.erase a := by
   simp only [erase_eq_eraseP']; exact h.eraseP
 
@@ -378,9 +400,10 @@ theorem le_length_erase [LawfulBEq α] {a : α} {l : List α} : l.length - 1 ≤
   rw [length_erase]
   split <;> simp
 
+@[grind →]
 theorem mem_of_mem_erase {a b : α} {l : List α} (h : a ∈ l.erase b) : a ∈ l := erase_subset h
 
-@[simp] theorem mem_erase_of_ne [LawfulBEq α] {a b : α} {l : List α} (ab : a ≠ b) :
+@[simp, grind] theorem mem_erase_of_ne [LawfulBEq α] {a b : α} {l : List α} (ab : a ≠ b) :
     a ∈ l.erase b ↔ a ∈ l :=
   erase_eq_eraseP b l ▸ mem_eraseP_of_neg (mt eq_of_beq ab.symm)
 
@@ -388,6 +411,7 @@ theorem mem_of_mem_erase {a b : α} {l : List α} (h : a ∈ l.erase b) : a ∈
   rw [erase_eq_eraseP', eraseP_eq_self_iff]
   simp [forall_mem_ne']
 
+@[grind _=_]
 theorem erase_filter [LawfulBEq α] {f : α → Bool} {l : List α} :
     (filter f l).erase a = filter f (l.erase a) := by
   induction l with
@@ -415,10 +439,12 @@ theorem erase_append_right [LawfulBEq α] {a : α} {l₁ : List α} (l₂ : List
   rw [erase_eq_eraseP, erase_eq_eraseP, eraseP_append_right]
   intros b h' h''; rw [eq_of_beq h''] at h; exact h h'
 
+@[grind =]
 theorem erase_append [LawfulBEq α] {a : α} {l₁ l₂ : List α} :
     (l₁ ++ l₂).erase a = if a ∈ l₁ then l₁.erase a ++ l₂ else l₁ ++ l₂.erase a := by
   simp [erase_eq_eraseP, eraseP_append]
 
+@[grind =]
 theorem erase_replicate [LawfulBEq α] {n : Nat} {a b : α} :
     (replicate n a).erase b = if b == a then replicate (n - 1) a else replicate n a := by
   rw [erase_eq_eraseP]
@@ -426,6 +452,7 @@ theorem erase_replicate [LawfulBEq α] {n : Nat} {a b : α} :
 
 -- The arguments `a b` are explicit,
 -- so they can be specified to prevent `simp` repeatedly applying the lemma.
+@[grind =]
 theorem erase_comm [LawfulBEq α] (a b : α) {l : List α} :
     (l.erase a).erase b = (l.erase b).erase a := by
   if ab : a == b then rw [eq_of_beq ab] else ?_
@@ -465,6 +492,7 @@ theorem erase_eq_iff [LawfulBEq α] {a : α} {l : List α} :
   rw [erase_of_not_mem]
   simp_all
 
+@[grind ←]
 theorem Pairwise.erase [LawfulBEq α] {l : List α} (a) : Pairwise p l → Pairwise p (l.erase a) :=
   Pairwise.sublist <| erase_sublist
 
@@ -487,6 +515,10 @@ theorem Nodup.mem_erase_iff [LawfulBEq α] {a : α} (d : Nodup l) : a ∈ l.eras
 theorem Nodup.not_mem_erase [LawfulBEq α] {a : α} (h : Nodup l) : a ∉ l.erase a := fun H => by
   simpa using ((Nodup.mem_erase_iff h).mp H).left
 
+-- Only activate `not_mem_erase` when `l.Nodup` is already available.
+grind_pattern List.Nodup.not_mem_erase => a ∈ l.erase a, l.Nodup
+
+@[grind]
 theorem Nodup.erase [LawfulBEq α] (a : α) : Nodup l → Nodup (l.erase a) :=
   Pairwise.erase a
 
@@ -513,6 +545,7 @@ end erase
 
 /-! ### eraseIdx -/
 
+@[grind =]
 theorem length_eraseIdx {l : List α} {i : Nat} :
     (l.eraseIdx i).length = if i < l.length then l.length - 1 else l.length := by
   induction l generalizing i with
@@ -530,8 +563,9 @@ theorem length_eraseIdx_of_lt {l : List α} {i} (h : i < length l) :
     (l.eraseIdx i).length = length l - 1 := by
   simp [length_eraseIdx, h]
 
-@[simp] theorem eraseIdx_zero {l : List α} : eraseIdx l 0 = l.tail := by cases l <;> rfl
+@[simp, grind =] theorem eraseIdx_zero {l : List α} : eraseIdx l 0 = l.tail := by cases l <;> rfl
 
+@[grind =]
 theorem eraseIdx_eq_take_drop_succ :
     ∀ (l : List α) (i : Nat), l.eraseIdx i = l.take i ++ l.drop (i + 1)
   | nil, _ => by simp
@@ -558,6 +592,7 @@ theorem eraseIdx_ne_nil_iff {l : List α} {i : Nat} : eraseIdx l i ≠ [] ↔ 2
 @[deprecated eraseIdx_ne_nil_iff (since := "2025-01-30")]
 abbrev eraseIdx_ne_nil := @eraseIdx_ne_nil_iff
 
+@[grind]
 theorem eraseIdx_sublist : ∀ (l : List α) (k : Nat), eraseIdx l k <+ l
   | [], _ => by simp
   | a::l, 0 => by simp
@@ -566,6 +601,7 @@ theorem eraseIdx_sublist : ∀ (l : List α) (k : Nat), eraseIdx l k <+ l
 theorem mem_of_mem_eraseIdx {l : List α} {i : Nat} {a : α} (h : a ∈ l.eraseIdx i) : a ∈ l :=
   (eraseIdx_sublist _ _).mem h
 
+@[grind]
 theorem eraseIdx_subset {l : List α} {k : Nat} : eraseIdx l k ⊆ l :=
   (eraseIdx_sublist _ _).subset
 
@@ -605,6 +641,15 @@ theorem eraseIdx_append_of_length_le {l : List α} {k : Nat} (hk : length l ≤
     | zero => simp_all
     | succ k => simp_all [eraseIdx_cons_succ, Nat.succ_sub_succ]
 
+@[grind =]
+theorem eraseIdx_append :
+    eraseIdx (l ++ l') k = if k < length l then eraseIdx l k ++ l' else l ++ eraseIdx l' (k - length l) := by
+  split <;> rename_i h
+  · simp [eraseIdx_append_of_lt_length h]
+  · rw [eraseIdx_append_of_length_le]
+    omega
+
+@[grind =]
 theorem eraseIdx_replicate {n : Nat} {a : α} {k : Nat} :
     (replicate n a).eraseIdx k = if k < n then replicate (n - 1) a else replicate n a := by
   split <;> rename_i h
@@ -616,12 +661,15 @@ theorem eraseIdx_replicate {n : Nat} {a : α} {k : Nat} :
     exact m.2
   · rw [eraseIdx_of_length_le (by simpa using h)]
 
+@[grind ←]
 theorem Pairwise.eraseIdx {l : List α} (k) : Pairwise p l → Pairwise p (l.eraseIdx k) :=
   Pairwise.sublist <| eraseIdx_sublist _ _
 
+@[grind ←]
 theorem Nodup.eraseIdx {l : List α} (k) : Nodup l → Nodup (l.eraseIdx k) :=
   Pairwise.eraseIdx k
 
+@[grind ←]
 protected theorem IsPrefix.eraseIdx {l l' : List α} (h : l <+: l') (k : Nat) :
     eraseIdx l k <+: eraseIdx l' k := by
   rcases h with ⟨t, rfl⟩

src/Init/Data/List/FinRange.lean

@@ -6,7 +6,8 @@ Authors: François G. Dorais
 module
 
 prelude
-import Init.Data.List.OfFn
+import all Init.Data.List.OfFn
+import Init.Data.List.Monadic
 
 set_option linter.listVariables true -- Enforce naming conventions for `List`/`Array`/`Vector` variables.
 set_option linter.indexVariables true -- Enforce naming conventions for index variables.
@@ -22,14 +23,14 @@ Examples:
 -/
 def finRange (n : Nat) : List (Fin n) := ofFn fun i => i
 
-@[simp] theorem length_finRange {n : Nat} : (List.finRange n).length = n := by
+@[simp, grind =] theorem length_finRange {n : Nat} : (List.finRange n).length = n := by
   simp [List.finRange]
 
-@[simp] theorem getElem_finRange {i : Nat} (h : i < (List.finRange n).length) :
+@[simp, grind =] theorem getElem_finRange {i : Nat} (h : i < (List.finRange n).length) :
     (finRange n)[i] = Fin.cast length_finRange ⟨i, h⟩ := by
   simp [List.finRange]
 
-@[simp] theorem finRange_zero : finRange 0 = [] := by simp [finRange]
+@[simp, grind =] theorem finRange_zero : finRange 0 = [] := by simp [finRange]
 
 theorem finRange_succ {n} : finRange (n+1) = 0 :: (finRange n).map Fin.succ := by
   apply List.ext_getElem; simp; intro i; cases i <;> simp
@@ -45,6 +46,7 @@ theorem finRange_succ_last {n} :
     · rfl
     · next h => exact Fin.eq_last_of_not_lt h
 
+@[grind _=_]
 theorem finRange_reverse {n} : (finRange n).reverse = (finRange n).map Fin.rev := by
   induction n with
   | zero => simp
@@ -57,3 +59,50 @@ theorem finRange_reverse {n} : (finRange n).reverse = (finRange n).map Fin.rev :
     simp [Fin.rev_succ]
 
 end List
+
+namespace Fin
+
+theorem foldlM_eq_foldlM_finRange [Monad m] (f : α → Fin n → m α) (x : α) :
+    foldlM n f x = (List.finRange n).foldlM f x := by
+  induction n generalizing x with
+  | zero => simp
+  | succ n ih =>
+    simp [foldlM_succ, List.finRange_succ, List.foldlM_cons]
+    congr 1
+    funext y
+    simp [ih, List.foldlM_map]
+
+theorem foldrM_eq_foldrM_finRange [Monad m] [LawfulMonad m] (f : Fin n → α → m α) (x : α) :
+    foldrM n f x = (List.finRange n).foldrM f x := by
+  induction n generalizing x with
+  | zero => simp
+  | succ n ih =>
+    simp [foldrM_succ, List.finRange_succ, ih, List.foldrM_map]
+
+theorem foldl_eq_finRange_foldl (f : α → Fin n → α) (x : α) :
+    foldl n f x = (List.finRange n).foldl f x := by
+  induction n generalizing x with
+  | zero => simp
+  | succ n ih =>
+    simp [foldl_succ, List.finRange_succ, ih, List.foldl_map]
+
+theorem foldr_eq_finRange_foldr (f : Fin n → α → α) (x : α) :
+    foldr n f x = (List.finRange n).foldr f x := by
+  induction n generalizing x with
+  | zero => simp
+  | succ n ih =>
+    simp [foldr_succ, List.finRange_succ, ih, List.foldr_map]
+
+end Fin
+
+namespace List
+
+theorem ofFnM_succ {n} [Monad m] [LawfulMonad m] {f : Fin (n + 1) → m α} :
+    ofFnM f = (do
+      let a ← f 0
+      let as ← ofFnM fun i => f i.succ
+      pure (a :: as)) := by
+  simp [ofFnM, Fin.foldlM_eq_foldlM_finRange, List.finRange_succ, List.foldlM_cons_eq_append,
+    List.foldlM_map]
+
+end List

src/Init/Data/List/Find.lean

@@ -45,7 +45,7 @@ theorem exists_of_findSome?_eq_some {l : List α} {f : α → Option β} (w : l.
     simp_all only [findSome?_cons, mem_cons, exists_eq_or_imp]
     split at w <;> simp_all
 
-@[simp] theorem findSome?_eq_none_iff : findSome? p l = none ↔ ∀ x ∈ l, p x = none := by
+@[simp, grind =] theorem findSome?_eq_none_iff : findSome? p l = none ↔ ∀ x ∈ l, p x = none := by
   induction l <;> simp [findSome?_cons]; split <;> simp [*]
 
 @[simp] theorem findSome?_isSome_iff {f : α → Option β} {l : List α} :
@@ -91,7 +91,7 @@ theorem findSome?_eq_some_iff {f : α → Option β} {l : List α} {b : β} :
           obtain ⟨⟨rfl, rfl⟩, rfl⟩ := h₁
           exact ⟨l₁, a, l₂, rfl, h₂, fun a' w => h₃ a' (mem_cons_of_mem p w)⟩
 
-@[simp] theorem findSome?_guard {l : List α} : findSome? (Option.guard fun x => p x) l = find? p l := by
+@[simp, grind =] theorem findSome?_guard {l : List α} : findSome? (Option.guard p) l = find? p l := by
   induction l with
   | nil => simp
   | cons x xs ih =>
@@ -103,32 +103,33 @@ theorem findSome?_eq_some_iff {f : α → Option β} {l : List α} {b : β} :
     · simp only [Option.guard_eq_none_iff] at h
       simp [ih, h]
 
-theorem find?_eq_findSome?_guard {l : List α} : find? p l = findSome? (Option.guard fun x => p x) l :=
+theorem find?_eq_findSome?_guard {l : List α} : find? p l = findSome? (Option.guard p) l :=
   findSome?_guard.symm
 
-@[simp] theorem head?_filterMap {f : α → Option β} {l : List α} : (l.filterMap f).head? = l.findSome? f := by
+@[simp, grind =] theorem head?_filterMap {f : α → Option β} {l : List α} : (l.filterMap f).head? = l.findSome? f := by
   induction l with
   | nil => simp
   | cons x xs ih =>
     simp only [filterMap_cons, findSome?_cons]
     split <;> simp [*]
 
-@[simp] theorem head_filterMap {f : α → Option β} {l : List α} (h) :
+@[simp, grind =] theorem head_filterMap {f : α → Option β} {l : List α} (h) :
     (l.filterMap f).head h = (l.findSome? f).get (by simp_all [Option.isSome_iff_ne_none]) := by
   simp [head_eq_iff_head?_eq_some]
 
-@[simp] theorem getLast?_filterMap {f : α → Option β} {l : List α} : (l.filterMap f).getLast? = l.reverse.findSome? f := by
+@[simp, grind =] theorem getLast?_filterMap {f : α → Option β} {l : List α} : (l.filterMap f).getLast? = l.reverse.findSome? f := by
   rw [getLast?_eq_head?_reverse]
   simp [← filterMap_reverse]
 
-@[simp] theorem getLast_filterMap {f : α → Option β} {l : List α} (h) :
+@[simp, grind =] theorem getLast_filterMap {f : α → Option β} {l : List α} (h) :
     (l.filterMap f).getLast h = (l.reverse.findSome? f).get (by simp_all [Option.isSome_iff_ne_none]) := by
   simp [getLast_eq_iff_getLast?_eq_some]
 
-@[simp] theorem map_findSome? {f : α → Option β} {g : β → γ} {l : List α} :
+@[simp, grind _=_] theorem map_findSome? {f : α → Option β} {g : β → γ} {l : List α} :
     (l.findSome? f).map g = l.findSome? (Option.map g ∘ f) := by
   induction l <;> simp [findSome?_cons]; split <;> simp [*]
 
+@[grind _=_]
 theorem findSome?_map {f : β → γ} {l : List β} : findSome? p (l.map f) = l.findSome? (p ∘ f) := by
   induction l with
   | nil => simp
@@ -136,15 +137,18 @@ theorem findSome?_map {f : β → γ} {l : List β} : findSome? p (l.map f) = l.
     simp only [map_cons, findSome?]
     split <;> simp_all
 
+@[grind =]
 theorem head_flatten {L : List (List α)} (h : ∃ l, l ∈ L ∧ l ≠ []) :
-    (flatten L).head (by simpa using h) = (L.findSome? fun l => l.head?).get (by simpa using h) := by
+    (flatten L).head (by simpa using h) = (L.findSome? head?).get (by simpa using h) := by
   simp [head_eq_iff_head?_eq_some, head?_flatten]
 
+@[grind =]
 theorem getLast_flatten {L : List (List α)} (h : ∃ l, l ∈ L ∧ l ≠ []) :
     (flatten L).getLast (by simpa using h) =
-      (L.reverse.findSome? fun l => l.getLast?).get (by simpa using h) := by
+      (L.reverse.findSome? getLast?).get (by simpa using h) := by
   simp [getLast_eq_iff_getLast?_eq_some, getLast?_flatten]
 
+@[grind =]
 theorem findSome?_replicate : findSome? f (replicate n a) = if n = 0 then none else f a := by
   cases n with
   | zero => simp
@@ -174,6 +178,9 @@ theorem Sublist.findSome?_isSome {l₁ l₂ : List α} (h : l₁ <+ l₂) :
     · simp_all
     · exact ih
 
+grind_pattern Sublist.findSome?_isSome => l₁ <+ l₂, l₁.findSome? f
+grind_pattern Sublist.findSome?_isSome => l₁ <+ l₂, l₂.findSome? f
+
 theorem Sublist.findSome?_eq_none {l₁ l₂ : List α} (h : l₁ <+ l₂) :
     l₂.findSome? f = none → l₁.findSome? f = none := by
   simp only [List.findSome?_eq_none_iff, Bool.not_eq_true]
@@ -185,16 +192,30 @@ theorem IsPrefix.findSome?_eq_some {l₁ l₂ : List α} {f : α → Option β}
   obtain ⟨t, rfl⟩ := h
   simp +contextual [findSome?_append]
 
+grind_pattern IsPrefix.findSome?_eq_some => l₁ <+: l₂, l₁.findSome? f, some b
+grind_pattern IsPrefix.findSome?_eq_some => l₁ <+: l₂, l₂.findSome? f, some b
+
 theorem IsPrefix.findSome?_eq_none {l₁ l₂ : List α} {f : α → Option β} (h : l₁ <+: l₂) :
     List.findSome? f l₂ = none → List.findSome? f l₁ = none :=
   h.sublist.findSome?_eq_none
+
+grind_pattern IsPrefix.findSome?_eq_none => l₁ <+: l₂, l₂.findSome? f
+grind_pattern IsPrefix.findSome?_eq_none => l₁ <+: l₂, l₁.findSome? f
+
 theorem IsSuffix.findSome?_eq_none {l₁ l₂ : List α} {f : α → Option β} (h : l₁ <:+ l₂) :
     List.findSome? f l₂ = none → List.findSome? f l₁ = none :=
   h.sublist.findSome?_eq_none
+
+grind_pattern IsSuffix.findSome?_eq_none => l₁ <+: l₂, l₂.findSome? f
+grind_pattern IsSuffix.findSome?_eq_none => l₁ <+: l₂, l₁.findSome? f
+
 theorem IsInfix.findSome?_eq_none {l₁ l₂ : List α} {f : α → Option β} (h : l₁ <:+: l₂) :
     List.findSome? f l₂ = none → List.findSome? f l₁ = none :=
   h.sublist.findSome?_eq_none
 
+grind_pattern IsInfix.findSome?_eq_none => l₁ <+: l₂, l₂.findSome? f
+grind_pattern IsInfix.findSome?_eq_none => l₁ <+: l₂, l₁.findSome? f
+
 /-! ### find? -/
 
 @[simp] theorem find?_cons_of_pos {l} (h : p a) : find? p (a :: l) = some a := by
@@ -203,7 +224,7 @@ theorem IsInfix.findSome?_eq_none {l₁ l₂ : List α} {f : α → Option β} (
 @[simp] theorem find?_cons_of_neg {l} (h : ¬p a) : find? p (a :: l) = find? p l := by
   simp [find?, h]
 
-@[simp] theorem find?_eq_none : find? p l = none ↔ ∀ x ∈ l, ¬ p x := by
+@[simp, grind =] theorem find?_eq_none : find? p l = none ↔ ∀ x ∈ l, ¬ p x := by
   induction l <;> simp [find?_cons]; split <;> simp [*]
 
 theorem find?_eq_some_iff_append :
@@ -243,33 +264,33 @@ theorem find?_eq_some_iff_append :
           cases h₁
           simp
 
-@[deprecated find?_eq_some_iff_append (since := "2024-11-06")]
-abbrev find?_eq_some := @find?_eq_some_iff_append
-
 @[simp]
 theorem find?_cons_eq_some : (a :: xs).find? p = some b ↔ (p a ∧ a = b) ∨ (!p a ∧ xs.find? p = some b) := by
   rw [find?_cons]
   split <;> simp_all
 
-@[simp] theorem find?_isSome {xs : List α} {p : α → Bool} : (xs.find? p).isSome ↔ ∃ x, x ∈ xs ∧ p x := by
+@[simp, grind =] theorem find?_isSome {xs : List α} {p : α → Bool} : (xs.find? p).isSome ↔ ∃ x, x ∈ xs ∧ p x := by
   induction xs with
   | nil => simp
   | cons x xs ih =>
     simp only [find?_cons, mem_cons, exists_eq_or_imp]
     split <;> simp_all
 
+@[grind →]
 theorem find?_some : ∀ {l}, find? p l = some a → p a
   | b :: l, H => by
     by_cases h : p b <;> simp [find?, h] at H
     · exact H ▸ h
     · exact find?_some H
 
+@[grind →]
 theorem mem_of_find?_eq_some : ∀ {l}, find? p l = some a → a ∈ l
   | b :: l, H => by
     by_cases h : p b <;> simp [find?, h] at H
     · exact H ▸ .head _
     · exact .tail _ (mem_of_find?_eq_some H)
 
+@[grind]
 theorem get_find?_mem {xs : List α} {p : α → Bool} (h) : (xs.find? p).get h ∈ xs := by
   induction xs with
   | nil => simp at h
@@ -281,7 +302,7 @@ theorem get_find?_mem {xs : List α} {p : α → Bool} (h) : (xs.find? p).get h
       right
       apply ih
 
-@[simp] theorem find?_filter {xs : List α} {p : α → Bool} {q : α → Bool} :
+@[simp, grind =] theorem find?_filter {xs : List α} {p : α → Bool} {q : α → Bool} :
     (xs.filter p).find? q = xs.find? (fun a => p a ∧ q a) := by
   induction xs with
   | nil => simp
@@ -291,22 +312,22 @@ theorem get_find?_mem {xs : List α} {p : α → Bool} (h) : (xs.find? p).get h
     · simp only [find?_cons]
       split <;> simp_all
 
-@[simp] theorem head?_filter {p : α → Bool} {l : List α} : (l.filter p).head? = l.find? p := by
+@[simp, grind =] theorem head?_filter {p : α → Bool} {l : List α} : (l.filter p).head? = l.find? p := by
   rw [← filterMap_eq_filter, head?_filterMap, findSome?_guard]
 
-@[simp] theorem head_filter {p : α → Bool} {l : List α} (h) :
+@[simp, grind =] theorem head_filter {p : α → Bool} {l : List α} (h) :
     (l.filter p).head h = (l.find? p).get (by simp_all [Option.isSome_iff_ne_none]) := by
   simp [head_eq_iff_head?_eq_some]
 
-@[simp] theorem getLast?_filter {p : α → Bool} {l : List α} : (l.filter p).getLast? = l.reverse.find? p := by
+@[simp, grind =] theorem getLast?_filter {p : α → Bool} {l : List α} : (l.filter p).getLast? = l.reverse.find? p := by
   rw [getLast?_eq_head?_reverse]
   simp [← filter_reverse]
 
-@[simp] theorem getLast_filter {p : α → Bool} {l : List α} (h) :
+@[simp, grind =] theorem getLast_filter {p : α → Bool} {l : List α} (h) :
     (l.filter p).getLast h = (l.reverse.find? p).get (by simp_all [Option.isSome_iff_ne_none]) := by
   simp [getLast_eq_iff_getLast?_eq_some]
 
-@[simp] theorem find?_filterMap {xs : List α} {f : α → Option β} {p : β → Bool} :
+@[simp, grind =] theorem find?_filterMap {xs : List α} {f : α → Option β} {p : β → Bool} :
     (xs.filterMap f).find? p = (xs.find? (fun a => (f a).any p)).bind f := by
   induction xs with
   | nil => simp
@@ -316,15 +337,15 @@ theorem get_find?_mem {xs : List α} {p : α → Bool} (h) : (xs.find? p).get h
     · simp only [find?_cons]
       split <;> simp_all
 
-@[simp] theorem find?_map {f : β → α} {l : List β} : find? p (l.map f) = (l.find? (p ∘ f)).map f := by
+@[simp, grind =] theorem find?_map {f : β → α} {l : List β} : find? p (l.map f) = (l.find? (p ∘ f)).map f := by
   induction l with
   | nil => simp
   | cons x xs ih =>
     simp only [map_cons, find?]
     by_cases h : p (f x) <;> simp [h, ih]
 
-@[simp] theorem find?_flatten {xss : List (List α)} {p : α → Bool} :
-    xss.flatten.find? p = xss.findSome? (·.find? p) := by
+@[simp, grind _=_] theorem find?_flatten {xss : List (List α)} {p : α → Bool} :
+    xss.flatten.find? p = xss.findSome? (find? p) := by
   induction xss with
   | nil => simp
   | cons _ _ ih =>
@@ -381,7 +402,7 @@ theorem find?_flatten_eq_some_iff {xs : List (List α)} {p : α → Bool} {a :
 @[deprecated find?_flatten_eq_some_iff (since := "2025-02-03")]
 abbrev find?_flatten_eq_some := @find?_flatten_eq_some_iff
 
-@[simp] theorem find?_flatMap {xs : List α} {f : α → List β} {p : β → Bool} :
+@[simp, grind =] theorem find?_flatMap {xs : List α} {f : α → List β} {p : β → Bool} :
     (xs.flatMap f).find? p = xs.findSome? (fun x => (f x).find? p) := by
   simp [flatMap_def, findSome?_map]; rfl
 
@@ -389,6 +410,7 @@ theorem find?_flatMap_eq_none_iff {xs : List α} {f : α → List β} {p : β
     (xs.flatMap f).find? p = none ↔ ∀ x ∈ xs, ∀ y ∈ f x, !p y := by
   simp
 
+@[grind =]
 theorem find?_replicate : find? p (replicate n a) = if n = 0 then none else if p a then some a else none := by
   cases n
   · simp
@@ -433,6 +455,9 @@ theorem Sublist.find?_isSome {l₁ l₂ : List α} (h : l₁ <+ l₂) : (l₁.fi
     · simp
     · simpa using ih
 
+grind_pattern Sublist.find?_isSome => l₁ <+ l₂, l₁.find? p
+grind_pattern Sublist.find?_isSome => l₁ <+ l₂, l₂.find? p
+
 theorem Sublist.find?_eq_none {l₁ l₂ : List α} (h : l₁ <+ l₂) : l₂.find? p = none → l₁.find? p = none := by
   simp only [List.find?_eq_none, Bool.not_eq_true]
   exact fun w x m => w x (Sublist.mem m h)
@@ -443,16 +468,31 @@ theorem IsPrefix.find?_eq_some {l₁ l₂ : List α} {p : α → Bool} (h : l₁
   obtain ⟨t, rfl⟩ := h
   simp +contextual [find?_append]
 
+grind_pattern IsPrefix.find?_eq_some => l₁ <+: l₂, l₁.find? p, some b
+grind_pattern IsPrefix.find?_eq_some => l₁ <+: l₂, l₂.find? p, some b
+
 theorem IsPrefix.find?_eq_none {l₁ l₂ : List α} {p : α → Bool} (h : l₁ <+: l₂) :
     List.find? p l₂ = none → List.find? p l₁ = none :=
   h.sublist.find?_eq_none
+
+grind_pattern Sublist.find?_eq_none => l₁ <+ l₂, l₂.find? p
+grind_pattern Sublist.find?_eq_none => l₁ <+ l₂, l₁.find? p
+
 theorem IsSuffix.find?_eq_none {l₁ l₂ : List α} {p : α → Bool} (h : l₁ <:+ l₂) :
     List.find? p l₂ = none → List.find? p l₁ = none :=
   h.sublist.find?_eq_none
+
+grind_pattern IsPrefix.find?_eq_none => l₁ <+: l₂, l₂.find? p
+grind_pattern IsPrefix.find?_eq_none => l₁ <+: l₂, l₁.find? p
+
 theorem IsInfix.find?_eq_none {l₁ l₂ : List α} {p : α → Bool} (h : l₁ <:+: l₂) :
     List.find? p l₂ = none → List.find? p l₁ = none :=
   h.sublist.find?_eq_none
 
+grind_pattern IsSuffix.find?_eq_none => l₁ <:+ l₂, l₂.find? p
+grind_pattern IsSuffix.find?_eq_none => l₁ <:+ l₂, l₁.find? p
+
+@[grind =]
 theorem find?_pmap {P : α → Prop} {f : (a : α) → P a → β} {xs : List α}
     (H : ∀ (a : α), a ∈ xs → P a) {p : β → Bool} :
     (xs.pmap f H).find? p = (xs.attach.find? (fun ⟨a, m⟩ => p (f a (H a m)))).map fun ⟨a, m⟩ => f a (H a m) := by
@@ -485,9 +525,9 @@ private theorem findIdx?_go_eq {p : α → Bool} {xs : List α} {i : Nat} :
       ext
       simp only [Nat.add_comm i, Function.comp_apply, Nat.add_assoc]
 
-@[simp] theorem findIdx?_nil : ([] : List α).findIdx? p = none := rfl
+@[simp, grind =] theorem findIdx?_nil : ([] : List α).findIdx? p = none := rfl
 
-theorem findIdx?_cons :
+@[grind =] theorem findIdx?_cons :
     (x :: xs).findIdx? p = if p x then some 0 else (xs.findIdx? p).map fun i => i + 1 := by
   simp [findIdx?, findIdx?_go_eq]
 
@@ -496,6 +536,7 @@ theorem findIdx?_cons :
 
 /-! ### findIdx -/
 
+@[grind =]
 theorem findIdx_cons {p : α → Bool} {b : α} {l : List α} :
     (b :: l).findIdx p = bif p b then 0 else (l.findIdx p) + 1 := by
   cases H : p b with
@@ -514,6 +555,7 @@ where
 @[simp] theorem findIdx_singleton {a : α} {p : α → Bool} : [a].findIdx p = if p a then 0 else 1 := by
   simp [findIdx_cons, findIdx_nil]
 
+@[grind →]
 theorem findIdx_of_getElem?_eq_some {xs : List α} (w : xs[xs.findIdx p]? = some y) : p y := by
   induction xs with
   | nil => simp_all
@@ -523,6 +565,8 @@ theorem findIdx_getElem {xs : List α} {w : xs.findIdx p < xs.length} :
     p xs[xs.findIdx p] :=
   xs.findIdx_of_getElem?_eq_some (getElem?_eq_getElem w)
 
+grind_pattern findIdx_getElem => xs[xs.findIdx p]
+
 theorem findIdx_lt_length_of_exists {xs : List α} (h : ∃ x ∈ xs, p x) :
     xs.findIdx p < xs.length := by
   induction xs with
@@ -561,6 +605,8 @@ theorem findIdx_le_length {p : α → Bool} {xs : List α} : xs.findIdx p ≤ xs
   · simp at e
     exact Nat.le_of_eq (findIdx_eq_length.mpr e)
 
+grind_pattern findIdx_le_length => xs.findIdx p, xs.length
+
 @[simp]
 theorem findIdx_lt_length {p : α → Bool} {xs : List α} :
     xs.findIdx p < xs.length ↔ ∃ x ∈ xs, p x := by
@@ -570,6 +616,8 @@ theorem findIdx_lt_length {p : α → Bool} {xs : List α} :
   rw [← this, findIdx_eq_length, not_exists]
   simp only [Bool.not_eq_true, not_and]
 
+grind_pattern findIdx_lt_length => xs.findIdx p, xs.length
+
 /-- `p` does not hold for elements with indices less than `xs.findIdx p`. -/
 theorem not_of_lt_findIdx {p : α → Bool} {xs : List α} {i : Nat} (h : i < xs.findIdx p) :
     p (xs[i]'(Nat.le_trans h findIdx_le_length)) = false := by
@@ -594,6 +642,8 @@ theorem not_of_lt_findIdx {p : α → Bool} {xs : List α} {i : Nat} (h : i < xs
       rw [← ipm, Nat.succ_lt_succ_iff] at h
       simpa using ih h
 
+grind_pattern not_of_lt_findIdx => xs.findIdx p, xs[i]
+
 /-- If `¬ p xs[j]` for all `j < i`, then `i ≤ xs.findIdx p`. -/
 theorem le_findIdx_of_not {p : α → Bool} {xs : List α} {i : Nat} (h : i < xs.length)
     (h2 : ∀ j (hji : j < i), p (xs[j]'(Nat.lt_trans hji h)) = false) : i ≤ xs.findIdx p := by
@@ -621,6 +671,7 @@ theorem findIdx_eq {p : α → Bool} {xs : List α} {i : Nat} (h : i < xs.length
   simp at h3
   simp_all [not_of_lt_findIdx h3]
 
+@[grind =]
 theorem findIdx_append {p : α → Bool} {l₁ l₂ : List α} :
     (l₁ ++ l₂).findIdx p =
       if l₁.findIdx p < l₁.length then l₁.findIdx p else l₂.findIdx p + l₁.length := by
@@ -642,6 +693,9 @@ theorem IsPrefix.findIdx_le {l₁ l₂ : List α} {p : α → Bool} (h : l₁ <+
   · exact Nat.le_refl ..
   · simp_all [findIdx_eq_length_of_false]
 
+grind_pattern IsPrefix.findIdx_le => l₁ <:+ l₂, l₁.findIdx p
+grind_pattern IsPrefix.findIdx_le => l₁ <:+ l₂, l₂.findIdx p
+
 theorem IsPrefix.findIdx_eq_of_findIdx_lt_length {l₁ l₂ : List α} {p : α → Bool} (h : l₁ <+: l₂)
     (lt : l₁.findIdx p < l₁.length) : l₂.findIdx p = l₁.findIdx p := by
   rw [IsPrefix] at h
@@ -651,6 +705,8 @@ theorem IsPrefix.findIdx_eq_of_findIdx_lt_length {l₁ l₂ : List α} {p : α
   · rfl
   · simp_all
 
+grind_pattern IsPrefix.findIdx_eq_of_findIdx_lt_length => l₁ <:+ l₂, l₁.findIdx p, l₂.findIdx p
+
 theorem findIdx_le_findIdx {l : List α} {p q : α → Bool} (h : ∀ x ∈ l, p x → q x) : l.findIdx q ≤ l.findIdx p := by
   induction l with
   | nil => simp
@@ -674,7 +730,7 @@ theorem findIdx_le_findIdx {l : List α} {p q : α → Bool} (h : ∀ x ∈ l, p
 
 /-! ### findIdx? -/
 
-@[simp]
+@[simp, grind =]
 theorem findIdx?_eq_none_iff {xs : List α} {p : α → Bool} :
     xs.findIdx? p = none ↔ ∀ x, x ∈ xs → p x = false := by
   induction xs with
@@ -683,7 +739,7 @@ theorem findIdx?_eq_none_iff {xs : List α} {p : α → Bool} :
     simp only [findIdx?_cons]
     split <;> simp_all [cond_eq_if]
 
-@[simp]
+@[simp, grind =]
 theorem findIdx?_isSome {xs : List α} {p : α → Bool} :
     (xs.findIdx? p).isSome = xs.any p := by
   induction xs with
@@ -692,7 +748,7 @@ theorem findIdx?_isSome {xs : List α} {p : α → Bool} :
     simp only [findIdx?_cons]
     split <;> simp_all
 
-@[simp]
+@[simp, grind =]
 theorem findIdx?_isNone {xs : List α} {p : α → Bool} :
     (xs.findIdx? p).isNone = xs.all (¬p ·) := by
   induction xs with
@@ -798,14 +854,14 @@ theorem of_findIdx?_eq_none {xs : List α} {p : α → Bool} (w : xs.findIdx? p
 @[deprecated of_findIdx?_eq_none (since := "2025-02-02")]
 abbrev findIdx?_of_eq_none := @of_findIdx?_eq_none
 
-@[simp] theorem findIdx?_map {f : β → α} {l : List β} : findIdx? p (l.map f) = l.findIdx? (p ∘ f) := by
+@[simp, grind _=_] theorem findIdx?_map {f : β → α} {l : List β} : findIdx? p (l.map f) = l.findIdx? (p ∘ f) := by
   induction l with
   | nil => simp
   | cons x xs ih =>
     simp only [map_cons, findIdx?_cons]
     split <;> simp_all
 
-@[simp] theorem findIdx?_append :
+@[simp, grind =] theorem findIdx?_append :
     (xs ++ ys : List α).findIdx? p =
       (xs.findIdx? p).or ((ys.findIdx? p).map fun i => i + xs.length) := by
   induction xs with simp [findIdx?_cons]
@@ -827,7 +883,7 @@ theorem findIdx?_flatten {l : List (List α)} {p : α → Bool} :
     · rw [Option.or_of_isNone (by simp_all [findIdx?_isNone])]
       simp [Function.comp_def, Nat.add_comm, Nat.add_assoc]
 
-@[simp] theorem findIdx?_replicate :
+@[simp, grind =] theorem findIdx?_replicate :
     (replicate n a).findIdx? p = if 0 < n ∧ p a then some 0 else none := by
   cases n with
   | zero => simp
@@ -881,22 +937,38 @@ theorem Sublist.findIdx?_eq_none {l₁ l₂ : List α} (h : l₁ <+ l₂) :
   simp only [findIdx?_eq_none_iff]
   exact fun w x m => w x (h.mem m)
 
+grind_pattern Sublist.findIdx?_eq_none => l₁ <+ l₂, l₁.findIdx? p
+grind_pattern Sublist.findIdx?_eq_none => l₁ <+ l₂, l₂.findIdx? p
+
 theorem IsPrefix.findIdx?_eq_some {l₁ l₂ : List α} {p : α → Bool} (h : l₁ <+: l₂) :
     List.findIdx? p l₁ = some i → List.findIdx? p l₂ = some i := by
   rw [IsPrefix] at h
   obtain ⟨t, rfl⟩ := h
   intro h
   simp [findIdx?_append, h]
+
 theorem IsPrefix.findIdx?_eq_none {l₁ l₂ : List α} {p : α → Bool} (h : l₁ <+: l₂) :
     List.findIdx? p l₂ = none → List.findIdx? p l₁ = none :=
   h.sublist.findIdx?_eq_none
+
+grind_pattern IsPrefix.findIdx?_eq_none => l₁ <+: l₂, l₁.findIdx? p
+grind_pattern IsPrefix.findIdx?_eq_none => l₁ <+: l₂, l₂.findIdx? p
+
 theorem IsSuffix.findIdx?_eq_none {l₁ l₂ : List α} {p : α → Bool} (h : l₁ <:+ l₂) :
     List.findIdx? p l₂ = none → List.findIdx? p l₁ = none :=
   h.sublist.findIdx?_eq_none
+
+grind_pattern IsSuffix.findIdx?_eq_none => l₁ <:+ l₂, l₁.findIdx? p
+grind_pattern IsSuffix.findIdx?_eq_none => l₁ <:+ l₂, l₂.findIdx? p
+
 theorem IsInfix.findIdx?_eq_none {l₁ l₂ : List α} {p : α → Bool} (h : l₁ <:+: l₂) :
     List.findIdx? p l₂ = none → List.findIdx? p l₁ = none :=
   h.sublist.findIdx?_eq_none
 
+grind_pattern IsInfix.findIdx?_eq_none => l₁ <:+: l₂, l₁.findIdx? p
+grind_pattern IsInfix.findIdx?_eq_none => l₁ <:+: l₂, l₂.findIdx? p
+
+@[grind =]
 theorem findIdx_eq_getD_findIdx? {xs : List α} {p : α → Bool} :
     xs.findIdx p = (xs.findIdx? p).getD xs.length := by
   induction xs with
@@ -917,7 +989,7 @@ theorem findIdx_eq_getD_findIdx? {xs : List α} {p : α → Bool} :
 
 /-! ### findFinIdx? -/
 
-@[simp] theorem findFinIdx?_nil {p : α → Bool} : findFinIdx? p [] = none := rfl
+@[simp, grind =] theorem findFinIdx?_nil {p : α → Bool} : findFinIdx? p [] = none := rfl
 
 theorem findIdx?_go_eq_map_findFinIdx?_go_val {xs : List α} {p : α → Bool} {i : Nat} {h} :
     List.findIdx?.go p xs i =
@@ -943,6 +1015,7 @@ theorem findFinIdx?_eq_pmap_findIdx? {xs : List α} {p : α → Bool} :
         (fun i h => h) := by
   simp [findIdx?_eq_map_findFinIdx?_val, Option.pmap_map]
 
+@[grind =]
 theorem findFinIdx?_cons {p : α → Bool} {x : α} {xs : List α} :
     findFinIdx? p (x :: xs) = if p x then some 0 else (findFinIdx? p xs).map Fin.succ := by
   rw [← Option.map_inj_right (f := Fin.val) (fun a b => Fin.eq_of_val_eq)]
@@ -953,6 +1026,7 @@ theorem findFinIdx?_cons {p : α → Bool} {x : α} {xs : List α} :
   · rw [findIdx?_eq_map_findFinIdx?_val]
     simp [Function.comp_def]
 
+@[grind =]
 theorem findFinIdx?_append {xs ys : List α} {p : α → Bool} :
     (xs ++ ys).findFinIdx? p =
       ((xs.findFinIdx? p).map (Fin.castLE (by simp))).or
@@ -962,11 +1036,11 @@ theorem findFinIdx?_append {xs ys : List α} {p : α → Bool} :
   · simp [h, Option.pmap_map, Option.map_pmap, Nat.add_comm]
   · simp [h]
 
-@[simp] theorem findFinIdx?_singleton {a : α} {p : α → Bool} :
+@[simp, grind =] theorem findFinIdx?_singleton {a : α} {p : α → Bool} :
     [a].findFinIdx? p = if p a then some ⟨0, by simp⟩ else none := by
   simp [findFinIdx?_cons, findFinIdx?_nil]
 
-@[simp] theorem findFinIdx?_eq_none_iff {l : List α} {p : α → Bool} :
+@[simp, grind =] theorem findFinIdx?_eq_none_iff {l : List α} {p : α → Bool} :
     l.findFinIdx? p = none ↔ ∀ x ∈ l, ¬ p x := by
   simp [findFinIdx?_eq_pmap_findIdx?]
 
@@ -982,7 +1056,7 @@ theorem findFinIdx?_eq_some_iff {xs : List α} {p : α → Bool} {i : Fin xs.len
   · rintro ⟨h, w⟩
     exact ⟨i, ⟨i.2, h, fun j hji => w ⟨j, by omega⟩ hji⟩, rfl⟩
 
-@[simp]
+@[simp, grind =]
 theorem isSome_findFinIdx? {l : List α} {p : α → Bool} :
     (l.findFinIdx? p).isSome = l.any p := by
   induction l with
@@ -991,7 +1065,7 @@ theorem isSome_findFinIdx? {l : List α} {p : α → Bool} :
     simp only [findFinIdx?_cons]
     split <;> simp_all
 
-@[simp]
+@[simp, grind =]
 theorem isNone_findFinIdx? {l : List α} {p : α → Bool} :
     (l.findFinIdx? p).isNone = l.all (fun x => ¬ p x) := by
   induction l with
@@ -1016,6 +1090,7 @@ The verification API for `idxOf` is still incomplete.
 The lemmas below should be made consistent with those for `findIdx` (and proved using them).
 -/
 
+@[grind =]
 theorem idxOf_cons [BEq α] :
     (x :: xs : List α).idxOf y = bif x == y then 0 else xs.idxOf y + 1 := by
   dsimp [idxOf]
@@ -1030,6 +1105,7 @@ abbrev indexOf_cons := @idxOf_cons
 @[deprecated idxOf_cons_self (since := "2025-01-29")]
 abbrev indexOf_cons_self := @idxOf_cons_self
 
+@[grind =]
 theorem idxOf_append [BEq α] [LawfulBEq α] {l₁ l₂ : List α} {a : α} :
     (l₁ ++ l₂).idxOf a = if a ∈ l₁ then l₁.idxOf a else l₂.idxOf a + l₁.length := by
   rw [idxOf, findIdx_append]
@@ -1053,7 +1129,7 @@ theorem idxOf_eq_length [BEq α] [LawfulBEq α] {l : List α} (h : a ∉ l) : l.
 @[deprecated idxOf_eq_length (since := "2025-01-29")]
 abbrev indexOf_eq_length := @idxOf_eq_length
 
-theorem idxOf_lt_length [BEq α] [EquivBEq α] {l : List α} (h : a ∈ l) : l.idxOf a < l.length := by
+theorem idxOf_lt_length_of_mem [BEq α] [EquivBEq α] {l : List α} (h : a ∈ l) : l.idxOf a < l.length := by
   induction l with
   | nil => simp at h
   | cons x xs ih =>
@@ -1066,8 +1142,23 @@ theorem idxOf_lt_length [BEq α] [EquivBEq α] {l : List α} (h : a ∈ l) : l.i
       · exact zero_lt_succ xs.length
       · exact Nat.add_lt_add_right ih 1
 
-@[deprecated idxOf_lt_length (since := "2025-01-29")]
-abbrev indexOf_lt_length := @idxOf_lt_length
+theorem idxOf_le_length [BEq α] [LawfulBEq α] {l : List α} {a : α} :
+    l.idxOf a ≤ l.length := by
+  simpa [idxOf] using findIdx_le_length
+
+grind_pattern idxOf_le_length => l.idxOf a, l.length
+
+theorem idxOf_lt_length_iff [BEq α] [LawfulBEq α] {l : List α} {a : α} :
+    l.idxOf a < l.length ↔ a ∈ l := by
+  constructor
+  · intro h
+    simpa [idxOf] using h
+  · exact idxOf_lt_length_of_mem
+
+grind_pattern idxOf_lt_length_iff => l.idxOf a, l.length
+
+@[deprecated idxOf_lt_length_of_mem (since := "2025-01-29")]
+abbrev indexOf_lt_length := @idxOf_lt_length_of_mem
 
 /-! ### finIdxOf?
 
@@ -1079,14 +1170,14 @@ theorem idxOf?_eq_map_finIdxOf?_val [BEq α] {xs : List α} {a : α} :
     xs.idxOf? a = (xs.finIdxOf? a).map (·.val) := by
   simp [idxOf?, finIdxOf?, findIdx?_eq_map_findFinIdx?_val]
 
-@[simp] theorem finIdxOf?_nil [BEq α] : ([] : List α).finIdxOf? a = none := rfl
+@[simp, grind =] theorem finIdxOf?_nil [BEq α] : ([] : List α).finIdxOf? a = none := rfl
 
-theorem finIdxOf?_cons [BEq α] {a : α} {xs : List α} :
+@[grind =] theorem finIdxOf?_cons [BEq α] {a : α} {xs : List α} :
     (a :: xs).finIdxOf? b =
       if a == b then some ⟨0, by simp⟩ else (xs.finIdxOf? b).map (·.succ) := by
   simp [finIdxOf?, findFinIdx?_cons]
 
-@[simp] theorem finIdxOf?_eq_none_iff [BEq α] [LawfulBEq α] {l : List α} {a : α} :
+@[simp, grind =] theorem finIdxOf?_eq_none_iff [BEq α] [LawfulBEq α] {l : List α} {a : α} :
     l.finIdxOf? a = none ↔ a ∉ l := by
   simp only [finIdxOf?, findFinIdx?_eq_none_iff, beq_iff_eq]
   constructor
@@ -1099,23 +1190,19 @@ theorem finIdxOf?_cons [BEq α] {a : α} {xs : List α} :
     l.finIdxOf? a = some i ↔ l[i] = a ∧ ∀ j (_ : j < i), ¬l[j] = a := by
   simp only [finIdxOf?, findFinIdx?_eq_some_iff, beq_iff_eq]
 
-@[simp]
-theorem isSome_finIdxOf? [BEq α] [LawfulBEq α] {l : List α} {a : α} :
-    (l.finIdxOf? a).isSome ↔ a ∈ l := by
+@[simp, grind =]
+theorem isSome_finIdxOf? [BEq α] [PartialEquivBEq α] {l : List α} {a : α} :
+    (l.finIdxOf? a).isSome = l.contains a := by
   induction l with
   | nil => simp
   | cons x xs ih =>
     simp only [finIdxOf?_cons]
-    split <;> simp_all [@eq_comm _ x a]
+    split <;> simp_all [BEq.comm]
 
 @[simp]
-theorem isNone_finIdxOf? [BEq α] [LawfulBEq α] {l : List α} {a : α} :
-    (l.finIdxOf? a).isNone = ¬ a ∈ l := by
-  induction l with
-  | nil => simp
-  | cons x xs ih =>
-    simp only [finIdxOf?_cons]
-    split <;> simp_all [@eq_comm _ x a]
+theorem isNone_finIdxOf? [BEq α] [PartialEquivBEq α] {l : List α} {a : α} :
+    (l.finIdxOf? a).isNone = !l.contains a := by
+  rw [← isSome_finIdxOf?, Option.not_isSome]
 
 /-! ### idxOf?
 
@@ -1123,16 +1210,16 @@ The verification API for `idxOf?` is still incomplete.
 The lemmas below should be made consistent with those for `findIdx?` (and proved using them).
 -/
 
-@[simp] theorem idxOf?_nil [BEq α] : ([] : List α).idxOf? a = none := rfl
+@[simp, grind =] theorem idxOf?_nil [BEq α] : ([] : List α).idxOf? a = none := rfl
 
-theorem idxOf?_cons [BEq α] {a : α} {xs : List α} {b : α} :
+@[grind =] theorem idxOf?_cons [BEq α] {a : α} {xs : List α} {b : α} :
     (a :: xs).idxOf? b = if a == b then some 0 else (xs.idxOf? b).map (· + 1) := by
   simp [idxOf?, findIdx?_cons]
 
 @[simp] theorem idxOf?_singleton [BEq α] {a b : α} : [a].idxOf? b = if a == b then some 0 else none := by
   simp [idxOf?_cons, idxOf?_nil]
 
-@[simp] theorem idxOf?_eq_none_iff [BEq α] [LawfulBEq α] {l : List α} {a : α} :
+@[simp, grind =] theorem idxOf?_eq_none_iff [BEq α] [LawfulBEq α] {l : List α} {a : α} :
     l.idxOf? a = none ↔ a ∉ l := by
   simp only [idxOf?, findIdx?_eq_none_iff, beq_eq_false_iff_ne, ne_eq]
   constructor
@@ -1145,7 +1232,7 @@ theorem idxOf?_cons [BEq α] {a : α} {xs : List α} {b : α} :
 @[deprecated idxOf?_eq_none_iff (since := "2025-01-29")]
 abbrev indexOf?_eq_none_iff := @idxOf?_eq_none_iff
 
-@[simp]
+@[simp, grind =]
 theorem isSome_idxOf? [BEq α] [LawfulBEq α] {l : List α} {a : α} :
     (l.idxOf? a).isSome ↔ a ∈ l := by
   induction l with
@@ -1154,15 +1241,10 @@ theorem isSome_idxOf? [BEq α] [LawfulBEq α] {l : List α} {a : α} :
     simp only [idxOf?_cons]
     split <;> simp_all [@eq_comm _ x a]
 
-@[simp]
+@[grind =]
 theorem isNone_idxOf? [BEq α] [LawfulBEq α] {l : List α} {a : α} :
     (l.idxOf? a).isNone = ¬ a ∈ l := by
-  induction l with
-  | nil => simp
-  | cons x xs ih =>
-    simp only [idxOf?_cons]
-    split <;> simp_all [@eq_comm _ x a]
-
+  simp
 
 /-! ### lookup -/
 
@@ -1186,7 +1268,7 @@ theorem lookup_eq_findSome? {l : List (α × β)} {k : α} :
       simp only [lookup_cons, findSome?_cons]
       split <;> simp_all
 
-@[simp] theorem lookup_eq_none_iff {l : List (α × β)} {k : α} :
+@[simp, grind =] theorem lookup_eq_none_iff {l : List (α × β)} {k : α} :
     l.lookup k = none ↔ ∀ p ∈ l, k != p.1 := by
   simp [lookup_eq_findSome?]
 
@@ -1206,10 +1288,12 @@ theorem lookup_eq_some_iff {l : List (α × β)} {k : α} {b : β} :
   · rintro ⟨l₁, l₂, rfl, h⟩
     exact ⟨l₁, (k, b), l₂, rfl, by simp, by simpa using h⟩
 
+@[grind =]
 theorem lookup_append {l₁ l₂ : List (α × β)} {k : α} :
     (l₁ ++ l₂).lookup k = (l₁.lookup k).or (l₂.lookup k) := by
   simp [lookup_eq_findSome?, findSome?_append]
 
+@[grind =]
 theorem lookup_replicate {k : α} :
     (replicate n (a,b)).lookup k = if n = 0 then none else if k == a then some b else none := by
   induction n with
@@ -1244,6 +1328,9 @@ theorem Sublist.lookup_eq_none {l₁ l₂ : List (α × β)} (h : l₁ <+ l₂)
   simp only [lookup_eq_findSome?]
   exact h.findSome?_eq_none
 
+grind_pattern Sublist.lookup_isSome => l₁ <+ l₂, l₁.lookup k
+grind_pattern Sublist.lookup_isSome => l₁ <+ l₂, l₂.lookup k
+
 theorem IsPrefix.lookup_eq_some {l₁ l₂ : List (α × β)} (h : l₁ <+: l₂) :
     List.lookup k l₁ = some b → List.lookup k l₂ = some b := by
   simp only [lookup_eq_findSome?]
@@ -1252,13 +1339,24 @@ theorem IsPrefix.lookup_eq_some {l₁ l₂ : List (α × β)} (h : l₁ <+: l₂
 theorem IsPrefix.lookup_eq_none {l₁ l₂ : List (α × β)} (h : l₁ <+: l₂) :
     List.lookup k l₂ = none → List.lookup k l₁ = none :=
   h.sublist.lookup_eq_none
+
+grind_pattern IsPrefix.lookup_eq_none => l₁ <+: l₂, l₁.lookup k
+grind_pattern IsPrefix.lookup_eq_none => l₁ <+: l₂, l₂.lookup k
+
 theorem IsSuffix.lookup_eq_none {l₁ l₂ : List (α × β)} (h : l₁ <:+ l₂) :
     List.lookup k l₂ = none → List.lookup k l₁ = none :=
   h.sublist.lookup_eq_none
+
+grind_pattern IsSuffix.lookup_eq_none => l₁ <:+ l₂, l₁.lookup k
+grind_pattern IsSuffix.lookup_eq_none => l₁ <:+ l₂, l₂.lookup k
+
 theorem IsInfix.lookup_eq_none {l₁ l₂ : List (α × β)} (h : l₁ <:+: l₂) :
     List.lookup k l₂ = none → List.lookup k l₁ = none :=
   h.sublist.lookup_eq_none
 
+grind_pattern IsInfix.lookup_eq_none => l₁ <:+: l₂, l₁.lookup k
+grind_pattern IsInfix.lookup_eq_none => l₁ <:+: l₂, l₂.lookup k
+
 end lookup
 
 end List

src/Init/Data/List/Impl.lean

@@ -109,7 +109,7 @@ Example:
   let rec go : ∀ as acc, filterMapTR.go f as acc = acc.toList ++ as.filterMap f
     | [], acc => by simp [filterMapTR.go, filterMap]
     | a::as, acc => by
-      simp only [filterMapTR.go, go as, Array.push_toList, append_assoc, singleton_append,
+      simp only [filterMapTR.go, go as, Array.toList_push, append_assoc, singleton_append,
         filterMap]
       split <;> simp [*]
   exact (go l #[]).symm
@@ -261,11 +261,11 @@ Examples:
 /-- Tail recursive implementation of `findRev?`. This is only used at runtime. -/
 def findRev?TR (p : α → Bool) (l : List α) : Option α := l.reverse.find? p
 
-@[simp] theorem find?_singleton {a : α} : [a].find? p = if p a then some a else none := by
+@[simp, grind =] theorem find?_singleton {a : α} : [a].find? p = if p a then some a else none := by
   simp only [find?]
   split <;> simp_all
 
-@[simp] theorem find?_append {xs ys : List α} : (xs ++ ys).find? p = (xs.find? p).or (ys.find? p) := by
+@[simp, grind =] theorem find?_append {xs ys : List α} : (xs ++ ys).find? p = (xs.find? p).or (ys.find? p) := by
   induction xs with
   | nil => simp [find?]
   | cons x xs ih =>
@@ -287,12 +287,12 @@ def findRev?TR (p : α → Bool) (l : List α) : Option α := l.reverse.find? p
 /-- Tail recursive implementation of `finSomedRev?`. This is only used at runtime. -/
 def findSomeRev?TR (f : α → Option β) (l : List α) : Option β := l.reverse.findSome? f
 
-@[simp] theorem findSome?_singleton {a : α} :
+@[simp, grind =] theorem findSome?_singleton {a : α} :
     [a].findSome? f = f a := by
   simp only [findSome?_cons, findSome?_nil]
   split <;> simp_all
 
-@[simp] theorem findSome?_append {xs ys : List α} : (xs ++ ys).findSome? f = (xs.findSome? f).or (ys.findSome? f) := by
+@[simp, grind =] theorem findSome?_append {xs ys : List α} : (xs ++ ys).findSome? f = (xs.findSome? f).or (ys.findSome? f) := by
   induction xs with
   | nil => simp [findSome?]
   | cons x xs ih =>
@@ -550,7 +550,7 @@ def zipIdxTR (l : List α) (n : Nat := 0) : List (α × Nat) :=
   (as.foldr (fun a (n, acc) => (n-1, (a, n-1) :: acc)) (n + as.size, [])).2
 
 @[csimp] theorem zipIdx_eq_zipIdxTR : @zipIdx = @zipIdxTR := by
-  funext α l n; simp only [zipIdxTR, size_toArray]
+  funext α l n; simp only [zipIdxTR]
   let f := fun (a : α) (n, acc) => (n-1, (a, n-1) :: acc)
   let rec go : ∀ l i, l.foldr f (i + l.length, []) = (i, zipIdx l i)
     | [], n => rfl
@@ -571,7 +571,7 @@ def enumFromTR (n : Nat) (l : List α) : List (Nat × α) :=
 set_option linter.deprecated false in
 @[deprecated zipIdx_eq_zipIdxTR (since := "2025-01-21"), csimp]
 theorem enumFrom_eq_enumFromTR : @enumFrom = @enumFromTR := by
-  funext α n l; simp only [enumFromTR, size_toArray]
+  funext α n l; simp only [enumFromTR]
   let f := fun (a : α) (n, acc) => (n-1, (n-1, a) :: acc)
   let rec go : ∀ l n, l.foldr f (n + l.length, []) = (n, enumFrom n l)
     | [], n => rfl

src/Init/Data/List/Lemmas.lean

@@ -109,9 +109,11 @@ abbrev length_eq_zero := @length_eq_zero_iff
 theorem eq_nil_iff_length_eq_zero : l = [] ↔ length l = 0 :=
   length_eq_zero_iff.symm
 
-@[grind →] theorem length_pos_of_mem {a : α} : ∀ {l : List α}, a ∈ l → 0 < length l
+theorem length_pos_of_mem {a : α} : ∀ {l : List α}, a ∈ l → 0 < length l
   | _::_, _ => Nat.zero_lt_succ _
 
+grind_pattern length_pos_of_mem => a ∈ l, length l
+
 theorem exists_mem_of_length_pos : ∀ {l : List α}, 0 < length l → ∃ a, a ∈ l
   | _::_, _ => ⟨_, .head ..⟩
 
@@ -272,13 +274,13 @@ theorem getElem_of_getElem? {l : List α} : l[i]? = some a → ∃ h : i < l.len
 theorem some_eq_getElem?_iff {l : List α} : some a = l[i]? ↔ ∃ h : i < l.length, l[i] = a := by
   rw [eq_comm, getElem?_eq_some_iff]
 
-@[simp] theorem some_getElem_eq_getElem?_iff {xs : List α} {i : Nat} (h : i < xs.length) :
+theorem some_getElem_eq_getElem?_iff {xs : List α} {i : Nat} (h : i < xs.length) :
     (some xs[i] = xs[i]?) ↔ True := by
-  simp [h]
+  simp
 
-@[simp] theorem getElem?_eq_some_getElem_iff {xs : List α} {i : Nat} (h : i < xs.length) :
+theorem getElem?_eq_some_getElem_iff {xs : List α} {i : Nat} (h : i < xs.length) :
     (xs[i]? = some xs[i]) ↔ True := by
-  simp [h]
+  simp
 
 theorem getElem_eq_iff {l : List α} {i : Nat} (h : i < l.length) : l[i] = x ↔ l[i]? = some x := by
   simp only [getElem?_eq_some_iff]
@@ -296,7 +298,7 @@ theorem getD_getElem? {l : List α} {i : Nat} {d : α} :
     have p : i ≥ l.length := Nat.le_of_not_gt h
     simp [getElem?_eq_none p, h]
 
-@[simp] theorem getElem_singleton {a : α} {i : Nat} (h : i < 1) : [a][i] = a :=
+@[simp] theorem getElem_singleton {a : α} {i : Nat} (h : i < 1) : [a][i] = a := by
   match i, h with
   | 0, _ => rfl
 
@@ -434,8 +436,8 @@ theorem eq_nil_iff_forall_not_mem {l : List α} : l = [] ↔ ∀ a, a ∉ l := b
 theorem eq_of_mem_singleton : a ∈ [b] → a = b
   | .head .. => rfl
 
-@[simp] theorem mem_singleton {a b : α} : a ∈ [b] ↔ a = b :=
-  ⟨eq_of_mem_singleton, (by simp [·])⟩
+theorem mem_singleton {a b : α} : a ∈ [b] ↔ a = b := by
+  simp
 
 theorem forall_mem_cons {p : α → Prop} {a : α} {l : List α} :
     (∀ x, x ∈ a :: l → p x) ↔ p a ∧ ∀ x, x ∈ l → p x :=
@@ -575,9 +577,9 @@ theorem isEmpty_iff_length_eq_zero {l : List α} : l.isEmpty ↔ l.length = 0 :=
 
 /-! ### any / all -/
 
-theorem any_eq {l : List α} : l.any p = decide (∃ x, x ∈ l ∧ p x) := by induction l <;> simp [*]
+@[grind =] theorem any_eq {l : List α} : l.any p = decide (∃ x, x ∈ l ∧ p x) := by induction l <;> simp [*]
 
-theorem all_eq {l : List α} : l.all p = decide (∀ x, x ∈ l → p x) := by induction l <;> simp [*]
+@[grind =] theorem all_eq {l : List α} : l.all p = decide (∀ x, x ∈ l → p x) := by induction l <;> simp [*]
 
 theorem decide_exists_mem {l : List α} {p : α → Prop} [DecidablePred p] :
     decide (∃ x, x ∈ l ∧ p x) = l.any p := by
@@ -834,7 +836,7 @@ theorem getElem_length_sub_one_eq_getLast {l : List α} (h : l.length - 1 < l.le
   rw [← getLast_eq_getElem]
 
 @[simp, grind] theorem getLast_cons_cons {a : α} {l : List α} :
-    getLast (a :: b :: l) (by simp) = getLast (b :: l) (by simp) := by
+    getLast (a :: b :: l) (by simp) = getLast (b :: l) (by simp) :=
   rfl
 
 theorem getLast_cons {a : α} {l : List α} : ∀ (h : l ≠ nil),
@@ -1128,7 +1130,8 @@ theorem map_singleton {f : α → β} {a : α} : map f [a] = [f a] := rfl
 
 -- We use a lower priority here as there are more specific lemmas in downstream libraries
 -- which should be able to fire first.
-@[simp 500] theorem mem_map {f : α → β} : ∀ {l : List α}, b ∈ l.map f ↔ ∃ a, a ∈ l ∧ f a = b
+@[simp 500, grind =] theorem mem_map {f : α → β} :
+    ∀ {l : List α}, b ∈ l.map f ↔ ∃ a, a ∈ l ∧ f a = b
   | [] => by simp
   | _ :: l => by simp [mem_map (l := l), eq_comm (a := b)]
 
@@ -1252,7 +1255,7 @@ theorem tailD_map {f : α → β} {l l' : List α} :
 theorem getLastD_map {f : α → β} {l : List α} {a : α} : (map f l).getLastD (f a) = f (l.getLastD a) := by
   simp
 
-@[simp] theorem map_map {g : β → γ} {f : α → β} {l : List α} :
+@[simp, grind _=_] theorem map_map {g : β → γ} {f : α → β} {l : List α} :
     map g (map f l) = map (g ∘ f) l := by induction l <;> simp_all
 
 /-! ### filter -/
@@ -1317,6 +1320,19 @@ theorem forall_mem_filter {l : List α} {p : α → Bool} {P : α → Prop} :
     (∀ (i) (_ : i ∈ l.filter p), P i) ↔ ∀ (j) (_ : j ∈ l), p j → P j := by
   simp
 
+@[grind] theorem getElem_filter {xs : List α} {p : α → Bool} {i : Nat} (h : i < (xs.filter p).length) :
+    p (xs.filter p)[i] :=
+  (mem_filter.mp (getElem_mem h)).2
+
+theorem getElem?_filter {xs : List α} {p : α → Bool} {i : Nat} (h : i < (xs.filter p).length)
+    (w : (xs.filter p)[i]? = some a) : p a := by
+  rw [getElem?_eq_getElem] at w
+  simp only [Option.some.injEq] at w
+  rw [← w]
+  apply getElem_filter h
+
+grind_pattern getElem?_filter => (xs.filter p)[i]?, some a
+
 @[simp] theorem filter_filter : ∀ {l}, filter p (filter q l) = filter (fun a => p a && q a) l
   | [] => rfl
   | a :: l => by by_cases hp : p a <;> by_cases hq : q a <;> simp [hp, hq, filter_filter]
@@ -1337,7 +1353,7 @@ theorem foldr_filter {p : α → Bool} {f : α → β → β} {l : List α} {ini
     simp only [filter_cons, foldr_cons]
     split <;> simp [ih]
 
-theorem filter_map {f : β → α} {p : α → Bool} {l : List β} :
+@[grind _=_] theorem filter_map {f : β → α} {p : α → Bool} {l : List β} :
     filter p (map f l) = map f (filter (p ∘ f) l) := by
   induction l with
   | nil => rfl
@@ -1572,9 +1588,6 @@ theorem not_mem_append {a : α} {s t : List α} (h₁ : a ∉ s) (h₂ : a ∉ t
 theorem mem_append_eq {a : α} {s t : List α} : (a ∈ s ++ t) = (a ∈ s ∨ a ∈ t) :=
   propext mem_append
 
-@[deprecated mem_append_left (since := "2024-11-20")] abbrev mem_append_of_mem_left := @mem_append_left
-@[deprecated mem_append_right (since := "2024-11-20")] abbrev mem_append_of_mem_right := @mem_append_right
-
 /--
 See also `eq_append_cons_of_mem`, which proves a stronger version
 in which the initial list must not contain the element.
@@ -1685,8 +1698,8 @@ theorem getLast_concat {a : α} : ∀ {l : List α}, getLast (l ++ [a]) (by simp
 
 @[deprecated append_eq_nil_iff (since := "2025-01-13")] abbrev append_eq_nil := @append_eq_nil_iff
 
-@[simp] theorem nil_eq_append_iff : [] = a ++ b ↔ a = [] ∧ b = [] := by
-  rw [eq_comm, append_eq_nil_iff]
+theorem nil_eq_append_iff : [] = a ++ b ↔ a = [] ∧ b = [] := by
+  simp
 
 @[grind →]
 theorem eq_nil_of_append_eq_nil {l₁ l₂ : List α} (h : l₁ ++ l₂ = []) : l₁ = [] ∧ l₂ = [] :=
@@ -1882,7 +1895,7 @@ theorem eq_nil_or_concat : ∀ l : List α, l = [] ∨ ∃ l' b, l = concat l' b
 
 /-! ### flatten -/
 
-@[simp] theorem length_flatten {L : List (List α)} : L.flatten.length = (L.map length).sum := by
+@[simp, grind _=_] theorem length_flatten {L : List (List α)} : L.flatten.length = (L.map length).sum := by
   induction L with
   | nil => rfl
   | cons =>
@@ -1897,8 +1910,8 @@ theorem eq_nil_or_concat : ∀ l : List α, l = [] ∨ ∃ l' b, l = concat l' b
 @[simp] theorem flatten_eq_nil_iff {L : List (List α)} : L.flatten = [] ↔ ∀ l ∈ L, l = [] := by
   induction L <;> simp_all
 
-@[simp] theorem nil_eq_flatten_iff {L : List (List α)} : [] = L.flatten ↔ ∀ l ∈ L, l = [] := by
-  rw [eq_comm, flatten_eq_nil_iff]
+theorem nil_eq_flatten_iff {L : List (List α)} : [] = L.flatten ↔ ∀ l ∈ L, l = [] := by
+  simp
 
 theorem flatten_ne_nil_iff {xss : List (List α)} : xss.flatten ≠ [] ↔ ∃ xs, xs ∈ xss ∧ xs ≠ [] := by
   simp
@@ -2052,7 +2065,7 @@ theorem eq_iff_flatten_eq : ∀ {L L' : List (List α)},
 
 /-! ### flatMap -/
 
-theorem flatMap_def {l : List α} {f : α → List β} : l.flatMap f = flatten (map f l) := rfl
+@[grind _=_] theorem flatMap_def {l : List α} {f : α → List β} : l.flatMap f = flatten (map f l) := rfl
 
 @[simp] theorem flatMap_id {L : List (List α)} : L.flatMap id = L.flatten := by simp [flatMap_def]
 
@@ -2541,17 +2554,25 @@ theorem flatten_reverse {L : List (List α)} :
   induction l generalizing b <;> simp [*]
 
 theorem foldl_eq_foldlM {f : β → α → β} {b : β} {l : List α} :
-    l.foldl f b = l.foldlM (m := Id) f b := by
-  induction l generalizing b <;> simp [*, foldl]
+    l.foldl f b = (l.foldlM (m := Id) (pure <| f · ·) b).run := by
+  simp
 
 theorem foldr_eq_foldrM {f : α → β → β} {b : β} {l : List α} :
-    l.foldr f b = l.foldrM (m := Id) f b := by
-  induction l <;> simp [*, foldr]
+    l.foldr f b = (l.foldrM (m := Id) (pure <| f · ·) b).run := by
+  simp
 
-@[simp] theorem id_run_foldlM {f : β → α → Id β} {b : β} {l : List α} :
+theorem idRun_foldlM {f : β → α → Id β} {b : β} {l : List α} :
+    Id.run (l.foldlM f b) = l.foldl (f · · |>.run) b := foldl_eq_foldlM.symm
+
+@[deprecated idRun_foldlM (since := "2025-05-21")]
+theorem id_run_foldlM {f : β → α → Id β} {b : β} {l : List α} :
     Id.run (l.foldlM f b) = l.foldl f b := foldl_eq_foldlM.symm
 
-@[simp] theorem id_run_foldrM {f : α → β → Id β} {b : β} {l : List α} :
+theorem idRun_foldrM {f : α → β → Id β} {b : β} {l : List α} :
+    Id.run (l.foldrM f b) = l.foldr (f · · |>.run) b := foldr_eq_foldrM.symm
+
+@[deprecated idRun_foldrM (since := "2025-05-21")]
+theorem id_run_foldrM {f : α → β → Id β} {b : β} {l : List α} :
     Id.run (l.foldrM f b) = l.foldr f b := foldr_eq_foldrM.symm
 
 @[simp] theorem foldlM_reverse [Monad m] {l : List α} {f : β → α → m β} {b : β} :
@@ -2576,6 +2597,11 @@ theorem foldr_eq_foldrM {f : α → β → β} {b : β} {l : List α} :
     l.foldl (fun xs y => f y :: xs) l' = (l.map f).reverse ++ l' := by
   induction l generalizing l' <;> simp [*]
 
+/-- Variant of `foldl_flip_cons_eq_append` specalized to `f = id`. -/
+@[grind] theorem foldl_flip_cons_eq_append' {l l' : List α} :
+    l.foldl (fun xs y => y :: xs) l' = l.reverse ++ l' := by
+  simp
+
 @[simp, grind] theorem foldr_append_eq_append {l : List α} {f : α → List β} {l' : List β} :
     l.foldr (f · ++ ·) l' = (l.map f).flatten ++ l' := by
   induction l <;> simp [*]
@@ -2641,10 +2667,10 @@ theorem foldr_map_hom {g : α → β} {f : α → α → α} {f' : β → β →
   induction l <;> simp [*]
 
 @[simp, grind _=_] theorem foldl_append {β : Type _} {f : β → α → β} {b : β} {l l' : List α} :
-    (l ++ l').foldl f b = l'.foldl f (l.foldl f b) := by simp [foldl_eq_foldlM]
+    (l ++ l').foldl f b = l'.foldl f (l.foldl f b) := by simp [foldl_eq_foldlM, -foldlM_pure]
 
 @[simp, grind _=_] theorem foldr_append {f : α → β → β} {b : β} {l l' : List α} :
-    (l ++ l').foldr f b = l.foldr f (l'.foldr f b) := by simp [foldr_eq_foldrM]
+    (l ++ l').foldr f b = l.foldr f (l'.foldr f b) := by simp [foldr_eq_foldrM, -foldrM_pure]
 
 @[grind] theorem foldl_flatten {f : β → α → β} {b : β} {L : List (List α)} :
     (flatten L).foldl f b = L.foldl (fun b l => l.foldl f b) b := by
@@ -2655,7 +2681,8 @@ theorem foldr_map_hom {g : α → β} {f : α → α → α} {f' : β → β →
   induction L <;> simp_all
 
 @[simp, grind] theorem foldl_reverse {l : List α} {f : β → α → β} {b : β} :
-    l.reverse.foldl f b = l.foldr (fun x y => f y x) b := by simp [foldl_eq_foldlM, foldr_eq_foldrM]
+    l.reverse.foldl f b = l.foldr (fun x y => f y x) b := by
+  simp [foldl_eq_foldlM, foldr_eq_foldrM, -foldrM_pure]
 
 @[simp, grind] theorem foldr_reverse {l : List α} {f : α → β → β} {b : β} :
     l.reverse.foldr f b = l.foldl (fun x y => f y x) b :=
@@ -2707,6 +2734,7 @@ example {xs : List Nat} : xs.foldl (· + ·) 1 > 0 := by
     intros; omega
 ```
 -/
+@[expose]
 def foldlRecOn {motive : β → Sort _} : ∀ (l : List α) (op : β → α → β) {b : β} (_ : motive b)
     (_ : ∀ (b : β) (_ : motive b) (a : α) (_ : a ∈ l), motive (op b a)), motive (List.foldl op b l)
   | [], _, _, hb, _ => hb
@@ -2714,11 +2742,11 @@ def foldlRecOn {motive : β → Sort _} : ∀ (l : List α) (op : β → α →
     foldlRecOn tl op (hl b hb hd mem_cons_self)
       fun y hy x hx => hl y hy x (mem_cons_of_mem hd hx)
 
-@[simp] theorem foldlRecOn_nil {motive : β → Sort _} {op : β → α → β} (hb : motive b)
+@[simp, grind =] theorem foldlRecOn_nil {motive : β → Sort _} {op : β → α → β} (hb : motive b)
     (hl : ∀ (b : β) (_ : motive b) (a : α) (_ : a ∈ []), motive (op b a)) :
     foldlRecOn [] op hb hl = hb := rfl
 
-@[simp] theorem foldlRecOn_cons {motive : β → Sort _} {op : β → α → β} (hb : motive b)
+@[simp, grind =] theorem foldlRecOn_cons {motive : β → Sort _} {op : β → α → β} (hb : motive b)
     (hl : ∀ (b : β) (_ : motive b) (a : α) (_ : a ∈ x :: l), motive (op b a)) :
     foldlRecOn (x :: l) op hb hl =
       foldlRecOn l op (hl b hb x mem_cons_self)
@@ -2741,6 +2769,7 @@ example {xs : List Nat} : xs.foldr (· + ·) 1 > 0 := by
     intros; omega
 ```
 -/
+@[expose]
 def foldrRecOn {motive : β → Sort _} : ∀ (l : List α) (op : α → β → β) {b : β} (_ : motive b)
     (_ : ∀ (b : β) (_ : motive b) (a : α) (_ : a ∈ l), motive (op a b)), motive (List.foldr op b l)
   | nil, _, _, hb, _ => hb
@@ -2748,11 +2777,11 @@ def foldrRecOn {motive : β → Sort _} : ∀ (l : List α) (op : α → β →
     hl (foldr op b l)
       (foldrRecOn l op hb fun b c a m => hl b c a (mem_cons_of_mem x m)) x mem_cons_self
 
-@[simp] theorem foldrRecOn_nil {motive : β → Sort _} {op : α → β → β} (hb : motive b)
+@[simp, grind =] theorem foldrRecOn_nil {motive : β → Sort _} {op : α → β → β} (hb : motive b)
     (hl : ∀ (b : β) (_ : motive b) (a : α) (_ : a ∈ []), motive (op a b)) :
     foldrRecOn [] op hb hl = hb := rfl
 
-@[simp] theorem foldrRecOn_cons {motive : β → Sort _} {op : α → β → β} (hb : motive b)
+@[simp, grind =] theorem foldrRecOn_cons {motive : β → Sort _} {op : α → β → β} (hb : motive b)
     (hl : ∀ (b : β) (_ : motive b) (a : α) (_ : a ∈ x :: l), motive (op a b)) :
     foldrRecOn (x :: l) op hb hl =
       hl _ (foldrRecOn l op hb fun b c a m => hl b c a (mem_cons_of_mem x m))
@@ -2764,8 +2793,8 @@ We can prove that two folds over the same list are related (by some arbitrary re
 if we know that the initial elements are related and the folding function, for each element of the list,
 preserves the relation.
 -/
-theorem foldl_rel {l : List α} {f g : β → α → β} {a b : β} {r : β → β → Prop}
-    (h : r a b) (h' : ∀ (a : α), a ∈ l → ∀ (c c' : β), r c c' → r (f c a) (g c' a)) :
+theorem foldl_rel {l : List α} {f : β → α → β} {g : γ → α → γ} {a : β} {b : γ} {r : β → γ → Prop}
+    (h : r a b) (h' : ∀ (a : α), a ∈ l → ∀ (c : β) (c' : γ), r c c' → r (f c a) (g c' a)) :
     r (l.foldl (fun acc a => f acc a) a) (l.foldl (fun acc a => g acc a) b) := by
   induction l generalizing a b with
   | nil => simp_all
@@ -2780,8 +2809,8 @@ We can prove that two folds over the same list are related (by some arbitrary re
 if we know that the initial elements are related and the folding function, for each element of the list,
 preserves the relation.
 -/
-theorem foldr_rel {l : List α} {f g : α → β → β} {a b : β} {r : β → β → Prop}
-    (h : r a b) (h' : ∀ (a : α), a ∈ l → ∀ (c c' : β), r c c' → r (f a c) (g a c')) :
+theorem foldr_rel {l : List α} {f : α → β → β} {g : α → γ → γ} {a : β} {b : γ} {r : β → γ → Prop}
+    (h : r a b) (h' : ∀ (a : α), a ∈ l → ∀ (c : β) (c' : γ), r c c' → r (f a c) (g a c')) :
     r (l.foldr (fun a acc => f a acc) a) (l.foldr (fun a acc => g a acc) b) := by
   induction l generalizing a b with
   | nil => simp_all
@@ -2888,13 +2917,13 @@ theorem getLast_filterMap_of_eq_some {f : α → Option β} {l : List α} (w : l
   rw [head_filterMap_of_eq_some (by simp_all)]
   simp_all
 
-theorem getLast?_flatMap {l : List α} {f : α → List β} :
+@[grind =] theorem getLast?_flatMap {l : List α} {f : α → List β} :
     (l.flatMap f).getLast? = l.reverse.findSome? fun a => (f a).getLast? := by
   simp only [← head?_reverse, reverse_flatMap]
   rw [head?_flatMap]
   rfl
 
-theorem getLast?_flatten {L : List (List α)} :
+@[grind =] theorem getLast?_flatten {L : List (List α)} :
     (flatten L).getLast? = L.reverse.findSome? fun l => l.getLast? := by
   simp [← flatMap_id, getLast?_flatMap]
 
@@ -2909,7 +2938,7 @@ theorem getLast?_replicate {a : α} {n : Nat} : (replicate n a).getLast? = if n
 /-! ### leftpad -/
 
 -- We unfold `leftpad` and `rightpad` for verification purposes.
-attribute [simp] leftpad rightpad
+attribute [simp, grind] leftpad rightpad
 
 -- `length_leftpad` and `length_rightpad` are in `Init.Data.List.Nat.Basic`.
 
@@ -2938,7 +2967,7 @@ theorem contains_iff_exists_mem_beq [BEq α] {l : List α} {a : α} :
     l.contains a ↔ ∃ a' ∈ l, a == a' := by
   induction l <;> simp_all
 
-@[grind]
+@[grind _=_]
 theorem contains_iff_mem [BEq α] [LawfulBEq α] {l : List α} {a : α} :
     l.contains a ↔ a ∈ l := by
   simp
@@ -3013,6 +3042,9 @@ we do not separately develop much theory about it.
 theorem mem_partition : a ∈ l ↔ a ∈ (partition p l).1 ∨ a ∈ (partition p l).2 := by
   by_cases p a <;> simp_all
 
+grind_pattern mem_partition => a ∈ (partition p l).1
+grind_pattern mem_partition => a ∈ (partition p l).2
+
 /-! ### dropLast
 
 `dropLast` is the specification for `Array.pop`, so theorems about `List.dropLast`
@@ -3084,7 +3116,7 @@ theorem dropLast_concat_getLast : ∀ {l : List α} (h : l ≠ []), dropLast l +
     congr
     exact dropLast_concat_getLast (cons_ne_nil b l)
 
-@[simp] theorem map_dropLast {f : α → β} {l : List α} : l.dropLast.map f = (l.map f).dropLast := by
+@[simp, grind _=_] theorem map_dropLast {f : α → β} {l : List α} : l.dropLast.map f = (l.map f).dropLast := by
   induction l with
   | nil => rfl
   | cons x xs ih => cases xs <;> simp [ih]
@@ -3096,6 +3128,7 @@ theorem dropLast_concat_getLast : ∀ {l : List α} (h : l ≠ []), dropLast l +
     rw [cons_append, dropLast, dropLast_append_of_ne_nil h, cons_append]
     simp [h]
 
+@[grind =]
 theorem dropLast_append {l₁ l₂ : List α} :
     (l₁ ++ l₂).dropLast = if l₂.isEmpty then l₁.dropLast else l₁ ++ l₂.dropLast := by
   split <;> simp_all
@@ -3103,9 +3136,9 @@ theorem dropLast_append {l₁ l₂ : List α} :
 theorem dropLast_append_cons : dropLast (l₁ ++ b :: l₂) = l₁ ++ dropLast (b :: l₂) := by
   simp
 
-@[simp] theorem dropLast_concat : dropLast (l₁ ++ [b]) = l₁ := by simp
+@[simp, grind =] theorem dropLast_concat : dropLast (l₁ ++ [b]) = l₁ := by simp
 
-@[simp] theorem dropLast_replicate {n : Nat} {a : α} : dropLast (replicate n a) = replicate (n - 1) a := by
+@[simp, grind =] theorem dropLast_replicate {n : Nat} {a : α} : dropLast (replicate n a) = replicate (n - 1) a := by
   match n with
   | 0 => simp
   | 1 => simp [replicate_succ]
@@ -3118,7 +3151,7 @@ theorem dropLast_append_cons : dropLast (l₁ ++ b :: l₂) = l₁ ++ dropLast (
     dropLast (a :: replicate n a) = replicate n a := by
   rw [← replicate_succ, dropLast_replicate, Nat.add_sub_cancel]
 
-@[simp] theorem tail_reverse {l : List α} : l.reverse.tail = l.dropLast.reverse := by
+@[simp, grind _=_] theorem tail_reverse {l : List α} : l.reverse.tail = l.dropLast.reverse := by
   apply ext_getElem
   · simp
   · intro i h₁ h₂
@@ -3358,6 +3391,7 @@ theorem replace_append_right [LawfulBEq α] {l₁ l₂ : List α} (h : ¬ a ∈
     (l₁ ++ l₂).replace a b = l₁ ++ l₂.replace a b := by
   simp [replace_append, h]
 
+@[grind _=_]
 theorem replace_take {l : List α} {i : Nat} :
     (l.take i).replace a b = (l.replace a b).take i := by
   induction l generalizing i with
@@ -3413,8 +3447,8 @@ variable [LawfulBEq α]
     | Or.inr h' => exact h'
   else rw [insert_of_not_mem h, mem_cons]
 
-@[simp] theorem mem_insert_self {a : α} {l : List α} : a ∈ l.insert a :=
-  mem_insert_iff.2 (Or.inl rfl)
+theorem mem_insert_self {a : α} {l : List α} : a ∈ l.insert a := by
+  simp
 
 theorem mem_insert_of_mem {l : List α} (h : a ∈ l) : a ∈ l.insert b :=
   mem_insert_iff.2 (Or.inr h)
@@ -3524,10 +3558,10 @@ end insert
 
 /-! ### `removeAll` -/
 
-@[simp] theorem removeAll_nil [BEq α] {xs : List α} : xs.removeAll [] = xs := by
+@[simp, grind =] theorem removeAll_nil [BEq α] {xs : List α} : xs.removeAll [] = xs := by
   simp [removeAll]
 
-theorem cons_removeAll [BEq α] {x : α} {xs ys : List α} :
+@[grind =] theorem cons_removeAll [BEq α] {x : α} {xs ys : List α} :
     (x :: xs).removeAll ys =
       if ys.contains x = false then
         x :: xs.removeAll ys
@@ -3535,6 +3569,7 @@ theorem cons_removeAll [BEq α] {x : α} {xs ys : List α} :
         xs.removeAll ys := by
   simp [removeAll, filter_cons]
 
+@[grind =]
 theorem removeAll_cons [BEq α] {xs : List α} {y : α} {ys : List α} :
     xs.removeAll (y :: ys) = (xs.filter fun x => !x == y).removeAll ys := by
   simp [removeAll, Bool.and_comm]
@@ -3554,7 +3589,7 @@ theorem removeAll_cons [BEq α] {xs : List α} {y : α} {ys : List α} :
 
 /-! ### `eraseDupsBy` and `eraseDups` -/
 
-@[simp] theorem eraseDupsBy_nil : ([] : List α).eraseDupsBy r = [] := rfl
+@[simp, grind =] theorem eraseDupsBy_nil : ([] : List α).eraseDupsBy r = [] := rfl
 
 private theorem eraseDupsBy_loop_cons {as bs : List α} {r : α → α → Bool} :
     eraseDupsBy.loop r as bs = bs.reverse ++ eraseDupsBy.loop r (as.filter fun a => !bs.any (r a)) [] := by
@@ -3574,17 +3609,19 @@ private theorem eraseDupsBy_loop_cons {as bs : List α} {r : α → α → Bool}
       simp
 termination_by as.length
 
+@[grind =]
 theorem eraseDupsBy_cons :
     (a :: as).eraseDupsBy r = a :: (as.filter fun b => r b a = false).eraseDupsBy r := by
   simp only [eraseDupsBy, eraseDupsBy.loop, any_nil]
   rw [eraseDupsBy_loop_cons]
   simp
 
-@[simp] theorem eraseDups_nil [BEq α] : ([] : List α).eraseDups = [] := rfl
-theorem eraseDups_cons [BEq α] {a : α} {as : List α} :
+@[simp, grind =] theorem eraseDups_nil [BEq α] : ([] : List α).eraseDups = [] := rfl
+@[grind =] theorem eraseDups_cons [BEq α] {a : α} {as : List α} :
     (a :: as).eraseDups = a :: (as.filter fun b => !b == a).eraseDups := by
   simp [eraseDups, eraseDupsBy_cons]
 
+@[grind =]
 theorem eraseDups_append [BEq α] [LawfulBEq α] {as bs : List α} :
     (as ++ bs).eraseDups = as.eraseDups ++ (bs.removeAll as).eraseDups := by
   match as with
@@ -3690,17 +3727,6 @@ theorem mem_iff_get? {a} {l : List α} : a ∈ l ↔ ∃ n, l.get? n = some a :=
 
 /-! ### Deprecations -/
 
-@[deprecated get?_eq_none (since := "2024-11-29")] abbrev get?_len_le := @getElem?_eq_none
-@[deprecated getElem?_eq_some_iff (since := "2024-11-29")]
-abbrev getElem?_eq_some := @getElem?_eq_some_iff
-@[deprecated get?_eq_some_iff (since := "2024-11-29")]
-abbrev get?_eq_some := @getElem?_eq_some_iff
-@[deprecated LawfulGetElem.getElem?_def (since := "2024-11-29")]
-theorem getElem?_eq (l : List α) (i : Nat) :
-    l[i]? = if h : i < l.length then some l[i] else none :=
-  getElem?_def _ _
-@[deprecated getElem?_eq_none (since := "2024-11-29")] abbrev getElem?_len_le := @getElem?_eq_none
-
 @[deprecated _root_.isSome_getElem? (since := "2024-12-09")]
 theorem isSome_getElem? {l : List α} {i : Nat} : l[i]?.isSome ↔ i < l.length := by
   simp

src/Init/Data/List/MapIdx.lean

@@ -27,7 +27,7 @@ that the index is valid.
 
 `List.mapIdx` is a variant that does not provide the function with evidence that the index is valid.
 -/
-@[inline] def mapFinIdx (as : List α) (f : (i : Nat) → α → (h : i < as.length) → β) : List β :=
+@[inline, expose] def mapFinIdx (as : List α) (f : (i : Nat) → α → (h : i < as.length) → β) : List β :=
   go as #[] (by simp)
 where
   /-- Auxiliary for `mapFinIdx`:
@@ -44,7 +44,7 @@ returning the list of results.
 `List.mapFinIdx` is a variant that additionally provides the function with a proof that the index
 is valid.
 -/
-@[inline] def mapIdx (f : Nat → α → β) (as : List α) : List β := go as #[] where
+@[inline, expose] def mapIdx (f : Nat → α → β) (as : List α) : List β := go as #[] where
   /-- Auxiliary for `mapIdx`:
   `mapIdx.go [a₀, a₁, ...] acc = acc.toList ++ [f acc.size a₀, f (acc.size + 1) a₁, ...]` -/
   @[specialize] go : List α → Array β → List β
@@ -91,7 +91,7 @@ is valid.
   subst w
   rfl
 
-@[simp]
+@[simp, grind =]
 theorem mapFinIdx_nil {f : (i : Nat) → α → (h : i < 0) → β} : mapFinIdx [] f = [] :=
   rfl
 
@@ -101,7 +101,7 @@ theorem mapFinIdx_nil {f : (i : Nat) → α → (h : i < 0) → β} : mapFinIdx
   | nil => simpa using h
   | cons _ _ ih => simp [mapFinIdx.go, ih]
 
-@[simp] theorem length_mapFinIdx {as : List α} {f : (i : Nat) → α → (h : i < as.length) → β} :
+@[simp, grind =] theorem length_mapFinIdx {as : List α} {f : (i : Nat) → α → (h : i < as.length) → β} :
     (as.mapFinIdx f).length = as.length := by
   simp [mapFinIdx, length_mapFinIdx_go]
 
@@ -129,7 +129,7 @@ theorem getElem_mapFinIdx_go {as : List α} {f : (i : Nat) → α → (h : i < a
     · have h₃ : i - acc.size = (i - (acc.size + 1)) + 1 := by omega
       simp [h₃]
 
-@[simp] theorem getElem_mapFinIdx {as : List α} {f : (i : Nat) → α → (h : i < as.length) → β} {i : Nat} {h} :
+@[simp, grind =] theorem getElem_mapFinIdx {as : List α} {f : (i : Nat) → α → (h : i < as.length) → β} {i : Nat} {h} :
     (as.mapFinIdx f)[i] = f i (as[i]'(by simp at h; omega)) (by simp at h; omega) := by
   simp [mapFinIdx, getElem_mapFinIdx_go]
 
@@ -137,18 +137,19 @@ theorem mapFinIdx_eq_ofFn {as : List α} {f : (i : Nat) → α → (h : i < as.l
     as.mapFinIdx f = List.ofFn fun i : Fin as.length => f i as[i] i.2 := by
   apply ext_getElem <;> simp
 
-@[simp] theorem getElem?_mapFinIdx {l : List α} {f : (i : Nat) → α → (h : i < l.length) → β} {i : Nat} :
+@[simp, grind =] theorem getElem?_mapFinIdx {l : List α} {f : (i : Nat) → α → (h : i < l.length) → β} {i : Nat} :
     (l.mapFinIdx f)[i]? = l[i]?.pbind fun x m => some <| f i x (by simp [getElem?_eq_some_iff] at m; exact m.1) := by
   simp only [getElem?_def, length_mapFinIdx, getElem_mapFinIdx]
   split <;> simp
 
-@[simp]
+@[simp, grind =]
 theorem mapFinIdx_cons {l : List α} {a : α} {f : (i : Nat) → α → (h : i < l.length + 1) → β} :
     mapFinIdx (a :: l) f = f 0 a (by omega) :: mapFinIdx l (fun i a h => f (i + 1) a (by omega)) := by
   apply ext_getElem
   · simp
   · rintro (_|i) h₁ h₂ <;> simp
 
+@[grind =]
 theorem mapFinIdx_append {xs ys : List α} {f : (i : Nat) → α → (h : i < (xs ++ ys).length) → β} :
     (xs ++ ys).mapFinIdx f =
       xs.mapFinIdx (fun i a h => f i a (by simp; omega)) ++
@@ -165,7 +166,7 @@ theorem mapFinIdx_append {xs ys : List α} {f : (i : Nat) → α → (h : i < (x
       congr
       omega
 
-@[simp] theorem mapFinIdx_concat {l : List α} {e : α} {f : (i : Nat) → α → (h : i < (l ++ [e]).length) → β}:
+@[simp, grind =] theorem mapFinIdx_concat {l : List α} {e : α} {f : (i : Nat) → α → (h : i < (l ++ [e]).length) → β}:
     (l ++ [e]).mapFinIdx f = l.mapFinIdx (fun i a h => f i a (by simp; omega)) ++ [f l.length e (by simp)] := by
   simp [mapFinIdx_append]
 
@@ -201,7 +202,7 @@ theorem exists_of_mem_mapFinIdx {b : β} {l : List α} {f : (i : Nat) → α →
   obtain ⟨h', rfl⟩ := h
   exact ⟨i, h', rfl⟩
 
-@[simp] theorem mem_mapFinIdx {b : β} {l : List α} {f : (i : Nat) → α → (h : i < l.length) → β} :
+@[simp, grind =] theorem mem_mapFinIdx {b : β} {l : List α} {f : (i : Nat) → α → (h : i < l.length) → β} :
     b ∈ l.mapFinIdx f ↔ ∃ (i : Nat) (h : i < l.length), f i l[i] h = b := by
   constructor
   · intro h
@@ -287,7 +288,7 @@ theorem mapFinIdx_eq_mapFinIdx_iff {l : List α} {f g : (i : Nat) → α → (h
   rw [eq_comm, mapFinIdx_eq_iff]
   simp [Fin.forall_iff]
 
-@[simp] theorem mapFinIdx_mapFinIdx {l : List α}
+@[simp, grind =] theorem mapFinIdx_mapFinIdx {l : List α}
     {f : (i : Nat) → α → (h : i < l.length) → β}
     {g : (i : Nat) → β → (h : i < (l.mapFinIdx f).length) → γ} :
     (l.mapFinIdx f).mapFinIdx g = l.mapFinIdx (fun i a h => g i (f i a h) (by simpa)) := by
@@ -303,7 +304,7 @@ theorem mapFinIdx_eq_replicate_iff {l : List α} {f : (i : Nat) → α → (h :
   · rintro w b i h rfl
     exact w i h
 
-@[simp] theorem mapFinIdx_reverse {l : List α} {f : (i : Nat) → α → (h : i < l.reverse.length) → β} :
+@[simp, grind =] theorem mapFinIdx_reverse {l : List α} {f : (i : Nat) → α → (h : i < l.reverse.length) → β} :
     l.reverse.mapFinIdx f =
       (l.mapFinIdx (fun i a h => f (l.length - 1 - i) a (by simp; omega))).reverse := by
   simp [mapFinIdx_eq_iff]
@@ -313,14 +314,14 @@ theorem mapFinIdx_eq_replicate_iff {l : List α} {f : (i : Nat) → α → (h :
 
 /-! ### mapIdx -/
 
-@[simp]
+@[simp, grind =]
 theorem mapIdx_nil {f : Nat → α → β} : mapIdx f [] = [] :=
   rfl
 
 theorem mapIdx_go_length {acc : Array β} :
     length (mapIdx.go f l acc) = length l + acc.size := by
   induction l generalizing acc with
-  | nil => simp only [mapIdx.go, length_nil, Nat.zero_add]
+  | nil => simp [mapIdx.go]
   | cons _ _ ih =>
     simp only [mapIdx.go, ih, Array.size_push, Nat.add_succ, length_cons, Nat.add_comm]
 
@@ -333,7 +334,7 @@ theorem length_mapIdx_go : ∀ {l : List α} {acc : Array β},
     simp
     omega
 
-@[simp] theorem length_mapIdx {l : List α} : (l.mapIdx f).length = l.length := by
+@[simp, grind =] theorem length_mapIdx {l : List α} : (l.mapIdx f).length = l.length := by
   simp [mapIdx, length_mapIdx_go]
 
 theorem getElem?_mapIdx_go : ∀ {l : List α} {acc : Array β} {i : Nat},
@@ -348,7 +349,7 @@ theorem getElem?_mapIdx_go : ∀ {l : List α} {acc : Array β} {i : Nat},
     split <;> split
     · simp only [Option.some.injEq]
       rw [← Array.getElem_toList]
-      simp only [Array.push_toList]
+      simp only [Array.toList_push]
       rw [getElem_append_left, ← Array.getElem_toList]
     · have : i = acc.size := by omega
       simp_all
@@ -356,11 +357,11 @@ theorem getElem?_mapIdx_go : ∀ {l : List α} {acc : Array β} {i : Nat},
     · have : i - acc.size = i - (acc.size + 1) + 1 := by omega
       simp_all
 
-@[simp] theorem getElem?_mapIdx {l : List α} {i : Nat} :
+@[simp, grind =] theorem getElem?_mapIdx {l : List α} {i : Nat} :
     (l.mapIdx f)[i]? = Option.map (f i) l[i]? := by
   simp [mapIdx, getElem?_mapIdx_go]
 
-@[simp] theorem getElem_mapIdx {l : List α} {f : Nat → α → β} {i : Nat} {h : i < (l.mapIdx f).length} :
+@[simp, grind =] theorem getElem_mapIdx {l : List α} {f : Nat → α → β} {i : Nat} {h : i < (l.mapIdx f).length} :
     (l.mapIdx f)[i] = f i (l[i]'(by simpa using h)) := by
   apply Option.some_inj.mp
   rw [← getElem?_eq_getElem, getElem?_mapIdx, getElem?_eq_getElem (by simpa using h)]
@@ -384,18 +385,19 @@ theorem mapIdx_eq_zipIdx_map {l : List α} {f : Nat → α → β} :
 @[deprecated mapIdx_eq_zipIdx_map (since := "2025-01-21")]
 abbrev mapIdx_eq_enum_map := @mapIdx_eq_zipIdx_map
 
-@[simp]
+@[simp, grind =]
 theorem mapIdx_cons {l : List α} {a : α} :
     mapIdx f (a :: l) = f 0 a :: mapIdx (fun i => f (i + 1)) l := by
   simp [mapIdx_eq_zipIdx_map, List.zipIdx_succ]
 
+@[grind =]
 theorem mapIdx_append {xs ys : List α} :
     (xs ++ ys).mapIdx f = xs.mapIdx f ++ ys.mapIdx fun i => f (i + xs.length) := by
   induction xs generalizing f with
   | nil => rfl
   | cons _ _ ih => simp [ih (f := fun i => f (i + 1)), Nat.add_assoc]
 
-@[simp] theorem mapIdx_concat {l : List α} {e : α} :
+@[simp, grind =] theorem mapIdx_concat {l : List α} {e : α} :
     mapIdx f (l ++ [e]) = mapIdx f l ++ [f l.length e] := by
   simp [mapIdx_append]
 
@@ -415,7 +417,7 @@ theorem exists_of_mem_mapIdx {b : β} {l : List α}
   rw [mapIdx_eq_mapFinIdx] at h
   simpa [Fin.exists_iff] using exists_of_mem_mapFinIdx h
 
-@[simp] theorem mem_mapIdx {b : β} {l : List α} :
+@[simp, grind =] theorem mem_mapIdx {b : β} {l : List α} :
     b ∈ mapIdx f l ↔ ∃ (i : Nat) (h : i < l.length), f i l[i] = b := by
   constructor
   · intro h
@@ -470,7 +472,7 @@ theorem mapIdx_eq_mapIdx_iff {l : List α} :
     · intro i h₁ h₂
       simp [w]
 
-@[simp] theorem mapIdx_set {l : List α} {i : Nat} {a : α} :
+@[simp, grind =] theorem mapIdx_set {l : List α} {i : Nat} {a : α} :
     (l.set i a).mapIdx f = (l.mapIdx f).set i (f i a) := by
   simp only [mapIdx_eq_iff, getElem?_set, length_mapIdx, getElem?_mapIdx]
   intro i
@@ -478,16 +480,16 @@ theorem mapIdx_eq_mapIdx_iff {l : List α} :
   · split <;> simp_all
   · rfl
 
-@[simp] theorem head_mapIdx {l : List α} {f : Nat → α → β} {w : mapIdx f l ≠ []} :
+@[simp, grind =] theorem head_mapIdx {l : List α} {f : Nat → α → β} {w : mapIdx f l ≠ []} :
     (mapIdx f l).head w = f 0 (l.head (by simpa using w)) := by
   cases l with
   | nil => simp at w
   | cons _ _ => simp
 
-@[simp] theorem head?_mapIdx {l : List α} {f : Nat → α → β} : (mapIdx f l).head? = l.head?.map (f 0) := by
+@[simp, grind =] theorem head?_mapIdx {l : List α} {f : Nat → α → β} : (mapIdx f l).head? = l.head?.map (f 0) := by
   cases l <;> simp
 
-@[simp] theorem getLast_mapIdx {l : List α} {f : Nat → α → β} {h} :
+@[simp, grind =] theorem getLast_mapIdx {l : List α} {f : Nat → α → β} {h} :
     (mapIdx f l).getLast h = f (l.length - 1) (l.getLast (by simpa using h)) := by
   cases l with
   | nil => simp at h
@@ -498,13 +500,13 @@ theorem mapIdx_eq_mapIdx_iff {l : List α} :
     simp only [← mapIdx_cons, getElem_mapIdx]
     simp
 
-@[simp] theorem getLast?_mapIdx {l : List α} {f : Nat → α → β} :
+@[simp, grind =] theorem getLast?_mapIdx {l : List α} {f : Nat → α → β} :
     (mapIdx f l).getLast? = (getLast? l).map (f (l.length - 1)) := by
   cases l
   · simp
   · rw [getLast?_eq_getLast, getLast?_eq_getLast, getLast_mapIdx] <;> simp
 
-@[simp] theorem mapIdx_mapIdx {l : List α} {f : Nat → α → β} {g : Nat → β → γ} :
+@[simp, grind =] theorem mapIdx_mapIdx {l : List α} {f : Nat → α → β} {g : Nat → β → γ} :
     (l.mapIdx f).mapIdx g = l.mapIdx (fun i => g i ∘ f i) := by
   simp [mapIdx_eq_iff]
 
@@ -517,7 +519,7 @@ theorem mapIdx_eq_replicate_iff {l : List α} {f : Nat → α → β} {b : β} :
   · rintro w _ i h rfl
     exact w i h
 
-@[simp] theorem mapIdx_reverse {l : List α} {f : Nat → α → β} :
+@[simp, grind =] theorem mapIdx_reverse {l : List α} {f : Nat → α → β} :
     l.reverse.mapIdx f = (mapIdx (fun i => f (l.length - 1 - i)) l).reverse := by
   simp [mapIdx_eq_iff]
   intro i

src/Init/Data/List/Monadic.lean

@@ -8,6 +8,8 @@ module
 prelude
 import Init.Data.List.TakeDrop
 import Init.Data.List.Attach
+import Init.Data.List.OfFn
+import Init.Data.Array.Bootstrap
 import all Init.Data.List.Control
 
 /-!
@@ -42,6 +44,7 @@ This is a non-tail-recursive variant of `List.mapM` that's easier to reason abou
 as the main definition and replaced by the tail-recursive version because they can only be proved
 equal when `m` is a `LawfulMonad`.
 -/
+@[expose]
 def mapM' [Monad m] (f : α → m β) : List α → m (List β)
   | [] => pure []
   | a :: l => return (← f a) :: (← l.mapM' f)
@@ -66,16 +69,24 @@ theorem mapM'_eq_mapM [Monad m] [LawfulMonad m] {f : α → m β} {l : List α}
     l.mapM (m := m) (pure <| f ·) = pure (l.map f) := by
   induction l <;> simp_all
 
-@[simp] theorem mapM_id {l : List α} {f : α → Id β} : l.mapM f = l.map f :=
+@[simp] theorem idRun_mapM {l : List α} {f : α → Id β} : (l.mapM f).run = l.map (f · |>.run) :=
   mapM_pure
 
+@[deprecated idRun_mapM (since := "2025-05-21")]
+theorem mapM_id {l : List α} {f : α → Id β} : (l.mapM f).run = l.map (f · |>.run) :=
+  mapM_pure
+
+@[simp] theorem mapM_map [Monad m] [LawfulMonad m] {f : α → β} {g : β → m γ} {l : List α} :
+    (l.map f).mapM g = l.mapM (g ∘ f) := by
+  induction l <;> simp_all
+
 @[simp] theorem mapM_append [Monad m] [LawfulMonad m] {f : α → m β} {l₁ l₂ : List α} :
     (l₁ ++ l₂).mapM f = (return (← l₁.mapM f) ++ (← l₂.mapM f)) := by induction l₁ <;> simp [*]
 
 /-- Auxiliary lemma for `mapM_eq_reverse_foldlM_cons`. -/
 theorem foldlM_cons_eq_append [Monad m] [LawfulMonad m] {f : α → m β} {as : List α} {b : β} {bs : List β} :
-    (as.foldlM (init := b :: bs) fun acc a => return ((← f a) :: acc)) =
-      (· ++ b :: bs) <$> as.foldlM (init := []) fun acc a => return ((← f a) :: acc) := by
+    (as.foldlM (init := b :: bs) fun acc a => (· :: acc) <$> f a) =
+      (· ++ b :: bs) <$> as.foldlM (init := []) fun acc a => (· :: acc) <$> f a := by
   induction as generalizing b bs with
   | nil => simp
   | cons a as ih =>
@@ -83,7 +94,7 @@ theorem foldlM_cons_eq_append [Monad m] [LawfulMonad m] {f : α → m β} {as :
     simp [ih, _root_.map_bind, Functor.map_map, Function.comp_def]
 
 theorem mapM_eq_reverse_foldlM_cons [Monad m] [LawfulMonad m] {f : α → m β} {l : List α} :
-    mapM f l = reverse <$> (l.foldlM (fun acc a => return ((← f a) :: acc)) []) := by
+    mapM f l = reverse <$> (l.foldlM (fun acc a => (· :: acc) <$> f a) []) := by
   rw [← mapM'_eq_mapM]
   induction l with
   | nil => simp
@@ -339,12 +350,18 @@ theorem forIn'_eq_foldlM [Monad m] [LawfulMonad m]
   simp only [forIn'_eq_foldlM]
   induction l.attach generalizing init <;> simp_all
 
-@[simp] theorem forIn'_yield_eq_foldl
+@[simp] theorem idRun_forIn'_yield_eq_foldl
+    (l : List α) (f : (a : α) → a ∈ l → β → Id β) (init : β) :
+    (forIn' l init (fun a m b => .yield <$> f a m b)).run =
+      l.attach.foldl (fun b ⟨a, h⟩ => f a h b |>.run) init :=
+  forIn'_pure_yield_eq_foldl _ _
+
+@[deprecated idRun_forIn'_yield_eq_foldl (since := "2025-05-21")]
+theorem forIn'_yield_eq_foldl
     {l : List α} (f : (a : α) → a ∈ l → β → β) (init : β) :
     forIn' (m := Id) l init (fun a m b => .yield (f a m b)) =
-      l.attach.foldl (fun b ⟨a, h⟩ => f a h b) init := by
-  simp only [forIn'_eq_foldlM]
-  induction l.attach generalizing init <;> simp_all
+      l.attach.foldl (fun b ⟨a, h⟩ => f a h b) init :=
+  forIn'_pure_yield_eq_foldl _ _
 
 @[simp] theorem forIn'_map [Monad m] [LawfulMonad m]
     {l : List α} (g : α → β) (f : (b : β) → b ∈ l.map g → γ → m (ForInStep γ)) :
@@ -392,12 +409,18 @@ theorem forIn_eq_foldlM [Monad m] [LawfulMonad m]
   simp only [forIn_eq_foldlM]
   induction l generalizing init <;> simp_all
 
-@[simp] theorem forIn_yield_eq_foldl
+@[simp] theorem idRun_forIn_yield_eq_foldl
+    (l : List α) (f : α → β → Id β) (init : β) :
+    (forIn l init (fun a b => .yield <$> f a b)).run =
+      l.foldl (fun b a => f a b |>.run) init :=
+  forIn_pure_yield_eq_foldl _ _
+
+@[deprecated idRun_forIn_yield_eq_foldl (since := "2025-05-21")]
+theorem forIn_yield_eq_foldl
     {l : List α} (f : α → β → β) (init : β) :
     forIn (m := Id) l init (fun a b => .yield (f a b)) =
-      l.foldl (fun b a => f a b) init := by
-  simp only [forIn_eq_foldlM]
-  induction l generalizing init <;> simp_all
+      l.foldl (fun b a => f a b) init :=
+  forIn_pure_yield_eq_foldl _ _
 
 @[simp] theorem forIn_map [Monad m] [LawfulMonad m]
     {l : List α} {g : α → β} {f : β → γ → m (ForInStep γ)} :

src/Init/Data/List/Nat/Basic.lean

@@ -26,6 +26,7 @@ namespace List
 
 /-! ### dropLast -/
 
+@[grind _=_]
 theorem tail_dropLast {l : List α} : tail (dropLast l) = dropLast (tail l) := by
   ext1
   simp only [getElem?_tail, getElem?_dropLast, length_tail]
@@ -35,7 +36,7 @@ theorem tail_dropLast {l : List α} : tail (dropLast l) = dropLast (tail l) := b
   · omega
   · rfl
 
-@[simp] theorem dropLast_reverse {l : List α} : l.reverse.dropLast = l.tail.reverse := by
+@[simp, grind _=_] theorem dropLast_reverse {l : List α} : l.reverse.dropLast = l.tail.reverse := by
   apply ext_getElem
   · simp
   · intro i h₁ h₂
@@ -114,7 +115,7 @@ section intersperse
 
 variable {l : List α} {sep : α} {i : Nat}
 
-@[simp] theorem length_intersperse : (l.intersperse sep).length = 2 * l.length - 1 := by
+@[simp, grind =] theorem length_intersperse : (l.intersperse sep).length = 2 * l.length - 1 := by
   fun_induction intersperse <;> simp only [intersperse, length_cons, length_nil] at *
   rename_i h _
   have := length_pos_iff.mpr h

src/Init/Data/List/Nat/Count.lean

@@ -16,6 +16,7 @@ namespace List
 
 open Nat
 
+@[grind =]
 theorem countP_set {p : α → Bool} {l : List α} {i : Nat} {a : α} (h : i < l.length) :
     (l.set i a).countP p = l.countP p - (if p l[i] then 1 else 0) + (if p a then 1 else 0) := by
   induction l generalizing i with
@@ -29,10 +30,12 @@ theorem countP_set {p : α → Bool} {l : List α} {i : Nat} {a : α} (h : i < l
       have : (if p l[i] = true then 1 else 0) ≤ l.countP p := boole_getElem_le_countP (p := p) h
       omega
 
+@[grind =]
 theorem count_set [BEq α] {a b : α} {l : List α} {i : Nat} (h : i < l.length) :
     (l.set i a).count b = l.count b - (if l[i] == b then 1 else 0) + (if a == b then 1 else 0) := by
   simp [count_eq_countP, countP_set, h]
 
+@[grind =]
 theorem countP_replace [BEq α] [LawfulBEq α] {a b : α} {l : List α} {p : α → Bool} :
     (l.replace a b).countP p =
       if l.contains a then l.countP p + (if p b then 1 else 0) - (if p a then 1 else 0) else l.countP p := by
@@ -55,11 +58,31 @@ theorem countP_replace [BEq α] [LawfulBEq α] {a b : α} {l : List α} {p : α
           omega
       · omega
 
+@[grind =]
 theorem count_replace [BEq α] [LawfulBEq α] {a b c : α} {l : List α} :
     (l.replace a b).count c =
       if l.contains a then l.count c + (if b == c then 1 else 0) - (if a == c then 1 else 0) else l.count c := by
   simp [count_eq_countP, countP_replace]
 
+@[grind =] theorem count_insert [BEq α] [LawfulBEq α] {a b : α} {l : List α} :
+    count a (List.insert b l) = max (count a l) (if b == a then 1 else 0) := by
+  simp only [List.insert, contains_eq_mem, decide_eq_true_eq, beq_iff_eq]
+  split <;> rename_i h
+  · split <;> rename_i h'
+    · rw [Nat.max_def]
+      simp only [beq_iff_eq] at h'
+      split
+      · have := List.count_pos_iff.mpr (h' ▸ h)
+        omega
+      · rfl
+    · simp [h']
+  · rw [count_cons]
+    split <;> rename_i h'
+    · simp only [beq_iff_eq] at h'
+      rw [count_eq_zero.mpr (h' ▸ h)]
+      simp [h']
+    · simp
+
 /--
 The number of elements satisfying a predicate in a sublist is at least the number of elements satisfying the predicate in the list,
 minus the difference in the lengths.
@@ -98,6 +121,8 @@ theorem le_countP_tail {l} : countP p l - 1 ≤ countP p l.tail := by
   simp only [length_tail] at this
   omega
 
+grind_pattern le_countP_tail => countP p l.tail
+
 variable [BEq α]
 
 theorem Sublist.le_count (s : l₁ <+ l₂) (a : α) : count a l₂ - (l₂.length - l₁.length) ≤ count a l₁ :=
@@ -115,4 +140,6 @@ theorem IsInfix.le_count (s : l₁ <:+: l₂) (a : α) : count a l₂ - (l₂.le
 theorem le_count_tail {a : α} {l : List α} : count a l - 1 ≤ count a l.tail :=
   le_countP_tail
 
+grind_pattern le_count_tail => count a l.tail
+
 end List

src/Init/Data/List/Nat/Erase.lean

@@ -14,6 +14,7 @@ set_option linter.indexVariables true -- Enforce naming conventions for index va
 
 namespace List
 
+@[grind =]
 theorem getElem?_eraseIdx {l : List α} {i : Nat} {j : Nat} :
     (l.eraseIdx i)[j]? = if j < i then l[j]? else l[j + 1]? := by
   rw [eraseIdx_eq_take_drop_succ, getElem?_append]
@@ -49,6 +50,7 @@ theorem getElem?_eraseIdx_of_ge {l : List α} {i : Nat} {j : Nat} (h : i ≤ j)
   intro h'
   omega
 
+@[grind =]
 theorem getElem_eraseIdx {l : List α} {i : Nat} {j : Nat} (h : j < (l.eraseIdx i).length) :
     (l.eraseIdx i)[j] = if h' : j < i then
         l[j]'(by have := length_eraseIdx_le l i; omega)
@@ -123,6 +125,48 @@ theorem eraseIdx_set_gt {l : List α} {i : Nat} {j : Nat} {a : α} (h : i < j) :
       · have t : i ≠ n := by omega
         simp [t]
 
+@[grind =]
+theorem eraseIdx_set {xs : List α} {i : Nat} {a : α} {j : Nat} :
+    (xs.set i a).eraseIdx j =
+      if j < i then
+        (xs.eraseIdx j).set (i - 1) a
+      else if j = i then
+        xs.eraseIdx i
+      else
+        (xs.eraseIdx j).set i a := by
+  split <;> rename_i h'
+  · rw [eraseIdx_set_lt]
+    omega
+  · split <;> rename_i h''
+    · subst h''
+      rw [eraseIdx_set_eq]
+    · rw [eraseIdx_set_gt]
+      omega
+
+theorem set_eraseIdx_le {xs : List α} {i : Nat} {j : Nat} {a : α} (h : i ≤ j) :
+    (xs.eraseIdx i).set j a = (xs.set (j + 1) a).eraseIdx i := by
+  rw [eraseIdx_set_lt]
+  · simp
+  · omega
+
+theorem set_eraseIdx_gt {xs : List α} {i : Nat} {j : Nat} {a : α} (h : j < i) :
+    (xs.eraseIdx i).set j a = (xs.set j a).eraseIdx i := by
+  rw [eraseIdx_set_gt]
+  omega
+
+@[grind =]
+theorem set_eraseIdx {xs : List α} {i : Nat} {j : Nat} {a : α} :
+    (xs.eraseIdx i).set j a =
+      if i ≤ j then
+        (xs.set (j + 1) a).eraseIdx i
+      else
+        (xs.set j a).eraseIdx i := by
+  split <;> rename_i h'
+  · rw [set_eraseIdx_le]
+    omega
+  · rw [set_eraseIdx_gt]
+    omega
+
 @[simp] theorem set_getElem_succ_eraseIdx_succ
     {l : List α} {i : Nat} (h : i + 1 < l.length) :
     (l.eraseIdx (i + 1)).set i l[i + 1] = l.eraseIdx i := by
@@ -143,7 +187,7 @@ theorem eraseIdx_set_gt {l : List α} {i : Nat} {j : Nat} {a : α} (h : i < j) :
       · have t : ¬ n < i := by omega
         simp [t]
 
-@[simp] theorem eraseIdx_length_sub_one {l : List α} :
+@[simp, grind =] theorem eraseIdx_length_sub_one {l : List α} :
     (l.eraseIdx (l.length - 1)) = l.dropLast := by
   apply ext_getElem
   · simp [length_eraseIdx]

src/Init/Data/List/Nat/InsertIdx.lean

@@ -30,19 +30,20 @@ section InsertIdx
 
 variable {a : α}
 
-@[simp]
+@[simp, grind =]
 theorem insertIdx_zero {xs : List α} {x : α} : xs.insertIdx 0 x = x :: xs :=
   rfl
 
-@[simp]
+@[simp, grind =]
 theorem insertIdx_succ_nil {n : Nat} {a : α} : ([] : List α).insertIdx (n + 1) a = [] :=
   rfl
 
-@[simp]
+@[simp, grind =]
 theorem insertIdx_succ_cons {xs : List α} {hd x : α} {i : Nat} :
     (hd :: xs).insertIdx (i + 1) x = hd :: xs.insertIdx i x :=
   rfl
 
+@[grind =]
 theorem length_insertIdx : ∀ {i} {as : List α}, (as.insertIdx i a).length = if i ≤ as.length then as.length + 1 else as.length
   | 0, _ => by simp
   | n + 1, [] => by simp
@@ -56,14 +57,9 @@ theorem length_insertIdx_of_le_length (h : i ≤ length as) (a : α) : (as.inser
 theorem length_insertIdx_of_length_lt (h : length as < i) (a : α) : (as.insertIdx i a).length = as.length := by
   simp [length_insertIdx, h]
 
-@[simp]
-theorem eraseIdx_insertIdx {i : Nat} {l : List α} (a : α) : (l.insertIdx i a).eraseIdx i = l := by
-  rw [eraseIdx_eq_modifyTailIdx, insertIdx, modifyTailIdx_modifyTailIdx_self]
-  exact modifyTailIdx_id _ _
-
 theorem insertIdx_eraseIdx_of_ge :
-    ∀ {i m as},
-      i < length as → i ≤ m → (as.eraseIdx i).insertIdx m a = (as.insertIdx (m + 1) a).eraseIdx i
+    ∀ {i j as},
+      i < length as → i ≤ j → (as.eraseIdx i).insertIdx j a = (as.insertIdx (j + 1) a).eraseIdx i
   | 0, 0, [], has, _ => (Nat.lt_irrefl _ has).elim
   | 0, 0, _ :: as, _, _ => by simp [eraseIdx, insertIdx]
   | 0, _ + 1, _ :: _, _, _ => rfl
@@ -79,6 +75,15 @@ theorem insertIdx_eraseIdx_of_le :
     congrArg (cons a) <|
       insertIdx_eraseIdx_of_le (Nat.lt_of_succ_lt_succ has) (Nat.le_of_succ_le_succ hmn)
 
+@[grind =]
+theorem insertIdx_eraseIdx (h : i < length as) :
+    (as.eraseIdx i).insertIdx j a =
+      if i ≤ j then (as.insertIdx (j + 1) a).eraseIdx i else (as.insertIdx j a).eraseIdx (i + 1) := by
+  split <;> rename_i h'
+  · rw [insertIdx_eraseIdx_of_ge h h']
+  · rw [insertIdx_eraseIdx_of_le h (by omega)]
+
+@[grind =]
 theorem insertIdx_comm (a b : α) :
     ∀ {i j : Nat} {l : List α} (_ : i ≤ j) (_ : j ≤ length l),
       (l.insertIdx i a).insertIdx (j + 1) b = (l.insertIdx j b).insertIdx i a
@@ -110,6 +115,11 @@ theorem insertIdx_of_length_lt {l : List α} {x : α} {i : Nat} (h : l.length <
     · simp only [Nat.succ_lt_succ_iff, length] at h
       simpa using ih h
 
+@[simp, grind =]
+theorem eraseIdx_insertIdx_self {i : Nat} {l : List α} (a : α) : (l.insertIdx i a).eraseIdx i = l := by
+  rw [eraseIdx_eq_modifyTailIdx, insertIdx, modifyTailIdx_modifyTailIdx_self]
+  exact modifyTailIdx_id _ _
+
 @[simp]
 theorem insertIdx_length_self {l : List α} {x : α} : l.insertIdx l.length x = l ++ [x] := by
   induction l with
@@ -185,6 +195,7 @@ theorem getElem_insertIdx_of_gt {l : List α} {x : α} {i j : Nat} (hn : i < j)
 @[deprecated getElem_insertIdx_of_gt (since := "2025-02-04")]
 abbrev getElem_insertIdx_of_ge := @getElem_insertIdx_of_gt
 
+@[grind =]
 theorem getElem_insertIdx {l : List α} {x : α} {i j : Nat} (h : j < (l.insertIdx i x).length) :
     (l.insertIdx i x)[j] =
       if h₁ : j < i then
@@ -201,6 +212,7 @@ theorem getElem_insertIdx {l : List α} {x : α} {i j : Nat} (h : j < (l.insertI
       rw [getElem_insertIdx_self h]
     · rw [getElem_insertIdx_of_gt (by omega)]
 
+@[grind =]
 theorem getElem?_insertIdx {l : List α} {x : α} {i j : Nat} :
     (l.insertIdx i x)[j]? =
       if j < i then

src/Init/Data/List/Nat/Modify.lean

@@ -17,7 +17,7 @@ namespace List
 
 /-! ### modifyHead -/
 
-@[simp] theorem length_modifyHead {f : α → α} {l : List α} : (l.modifyHead f).length = l.length := by
+@[simp, grind =] theorem length_modifyHead {f : α → α} {l : List α} : (l.modifyHead f).length = l.length := by
   cases l <;> simp [modifyHead]
 
 theorem modifyHead_eq_set [Inhabited α] (f : α → α) (l : List α) :
@@ -26,9 +26,10 @@ theorem modifyHead_eq_set [Inhabited α] (f : α → α) (l : List α) :
 @[simp] theorem modifyHead_eq_nil_iff {f : α → α} {l : List α} :
     l.modifyHead f = [] ↔ l = [] := by cases l <;> simp [modifyHead]
 
-@[simp] theorem modifyHead_modifyHead {l : List α} {f g : α → α} :
+@[simp, grind =] theorem modifyHead_modifyHead {l : List α} {f g : α → α} :
     (l.modifyHead f).modifyHead g = l.modifyHead (g ∘ f) := by cases l <;> simp [modifyHead]
 
+@[grind =]
 theorem getElem_modifyHead {l : List α} {f : α → α} {i} (h : i < (l.modifyHead f).length) :
     (l.modifyHead f)[i] = if h' : i = 0 then f (l[0]'(by simp at h; omega)) else l[i]'(by simpa using h) := by
   cases l with
@@ -41,6 +42,7 @@ theorem getElem_modifyHead {l : List α} {f : α → α} {i} (h : i < (l.modifyH
 @[simp] theorem getElem_modifyHead_succ {l : List α} {f : α → α} {n} (h : n + 1 < (l.modifyHead f).length) :
     (l.modifyHead f)[n + 1] = l[n + 1]'(by simpa using h) := by simp [getElem_modifyHead]
 
+@[grind =]
 theorem getElem?_modifyHead {l : List α} {f : α → α} {i} :
     (l.modifyHead f)[i]? = if i = 0 then l[i]?.map f else l[i]? := by
   cases l with
@@ -53,19 +55,19 @@ theorem getElem?_modifyHead {l : List α} {f : α → α} {i} :
 @[simp] theorem getElem?_modifyHead_succ {l : List α} {f : α → α} {n} :
     (l.modifyHead f)[n + 1]? = l[n + 1]? := by simp [getElem?_modifyHead]
 
-@[simp] theorem head_modifyHead (f : α → α) (l : List α) (h) :
+@[simp, grind =] theorem head_modifyHead (f : α → α) (l : List α) (h) :
     (l.modifyHead f).head h = f (l.head (by simpa using h)) := by
   cases l with
   | nil => simp at h
   | cons hd tl => simp
 
-@[simp] theorem head?_modifyHead {l : List α} {f : α → α} :
+@[simp, grind =] theorem head?_modifyHead {l : List α} {f : α → α} :
     (l.modifyHead f).head? = l.head?.map f := by cases l <;> simp
 
-@[simp] theorem tail_modifyHead {f : α → α} {l : List α} :
+@[simp, grind =] theorem tail_modifyHead {f : α → α} {l : List α} :
     (l.modifyHead f).tail = l.tail := by cases l <;> simp
 
-@[simp] theorem take_modifyHead {f : α → α} {l : List α} {i} :
+@[simp, grind =] theorem take_modifyHead {f : α → α} {l : List α} {i} :
     (l.modifyHead f).take i = (l.take i).modifyHead f := by
   cases l <;> cases i <;> simp
 
@@ -73,6 +75,7 @@ theorem getElem?_modifyHead {l : List α} {f : α → α} {i} :
     (l.modifyHead f).drop i = l.drop i := by
   cases l <;> cases i <;> simp_all
 
+@[grind =]
 theorem eraseIdx_modifyHead_zero {f : α → α} {l : List α} :
     (l.modifyHead f).eraseIdx 0 = l.eraseIdx 0 := by simp
 
@@ -81,7 +84,7 @@ theorem eraseIdx_modifyHead_zero {f : α → α} {l : List α} :
 
 @[simp] theorem modifyHead_id : modifyHead (id : α → α) = id := by funext l; cases l <;> simp
 
-@[simp] theorem modifyHead_dropLast {l : List α} {f : α → α} :
+@[simp, grind _=_] theorem modifyHead_dropLast {l : List α} {f : α → α} :
     l.dropLast.modifyHead f = (l.modifyHead f).dropLast := by
   rcases l with _|⟨a, l⟩
   · simp
@@ -99,7 +102,7 @@ theorem eraseIdx_eq_modifyTailIdx : ∀ i (l : List α), eraseIdx l i = l.modify
   | _+1, [] => rfl
   | _+1, _ :: _ => congrArg (cons _) (eraseIdx_eq_modifyTailIdx _ _)
 
-@[simp] theorem length_modifyTailIdx (f : List α → List α) (H : ∀ l, (f l).length = l.length) :
+@[simp, grind =] theorem length_modifyTailIdx (f : List α → List α) (H : ∀ l, (f l).length = l.length) :
     ∀ (l : List α) i, (l.modifyTailIdx i f).length = l.length
   | _, 0 => H _
   | [], _+1 => rfl
@@ -142,7 +145,7 @@ theorem modifyTailIdx_modifyTailIdx_self {f g : List α → List α} (i : Nat) (
 
 /-! ### modify -/
 
-@[simp] theorem modify_nil (f : α → α) (i) : [].modify i f = [] := by cases i <;> rfl
+@[simp, grind =] theorem modify_nil (f : α → α) (i) : [].modify i f = [] := by cases i <;> rfl
 
 @[simp] theorem modify_zero_cons (f : α → α) (a : α) (l : List α) :
     (a :: l).modify 0 f = f a :: l := rfl
@@ -150,13 +153,22 @@ theorem modifyTailIdx_modifyTailIdx_self {f g : List α → List α} (i : Nat) (
 @[simp] theorem modify_succ_cons (f : α → α) (a : α) (l : List α) (i) :
     (a :: l).modify (i + 1) f = a :: l.modify i f := rfl
 
+@[grind =]
+theorem modify_cons {f : α → α} {a : α} {l : List α} {i : Nat} :
+    (a :: l).modify i f =
+      if i = 0 then f a :: l else a :: l.modify (i - 1) f := by
+  split <;> rename_i h
+  · subst h
+    simp
+  · match i, h with | i + 1, _ => simp
+
 theorem modifyHead_eq_modify_zero (f : α → α) (l : List α) :
     l.modifyHead f = l.modify 0 f := by cases l <;> simp
 
 @[simp] theorem modify_eq_nil_iff {f : α → α} {i} {l : List α} :
     l.modify i f = [] ↔ l = [] := by cases l <;> cases i <;> simp
 
-theorem getElem?_modify (f : α → α) :
+@[grind =] theorem getElem?_modify (f : α → α) :
     ∀ i (l : List α) j, (l.modify i f)[j]? = (fun a => if i = j then f a else a) <$> l[j]?
   | n, l, 0 => by cases l <;> cases n <;> simp
   | n, [], _+1 => by cases n <;> rfl
@@ -167,7 +179,7 @@ theorem getElem?_modify (f : α → α) :
     cases h' : l[j]? <;> by_cases h : i = j <;>
       simp [h, if_pos, if_neg, Option.map, mt Nat.succ.inj, not_false_iff, h']
 
-@[simp] theorem length_modify (f : α → α) : ∀ (l : List α) i, (l.modify i f).length = l.length :=
+@[simp, grind =] theorem length_modify (f : α → α) : ∀ (l : List α) i, (l.modify i f).length = l.length :=
   length_modifyTailIdx _ fun l => by cases l <;> rfl
 
 @[simp] theorem getElem?_modify_eq (f : α → α) (i) (l : List α) :
@@ -178,7 +190,7 @@ theorem getElem?_modify (f : α → α) :
     (l.modify i f)[j]? = l[j]? := by
   simp only [getElem?_modify, if_neg h, id_map']
 
-theorem getElem_modify (f : α → α) (i) (l : List α) (j) (h : j < (l.modify i f).length) :
+@[grind =] theorem getElem_modify (f : α → α) (i) (l : List α) (j) (h : j < (l.modify i f).length) :
     (l.modify i f)[j] =
       if i = j then f (l[j]'(by simp at h; omega)) else l[j]'(by simp at h; omega) := by
   rw [getElem_eq_iff, getElem?_modify]
@@ -200,6 +212,7 @@ theorem modify_eq_self {f : α → α} {i} {l : List α} (h : l.length ≤ i) :
     intro h
     omega
 
+@[grind =]
 theorem modify_modify_eq (f g : α → α) (i) (l : List α) :
     (l.modify i f).modify i g = l.modify i (g ∘ f) := by
   apply ext_getElem
@@ -245,6 +258,7 @@ theorem exists_of_modify (f : α → α) {i} {l : List α} (h : i < l.length) :
 @[simp] theorem modify_id (i) (l : List α) : l.modify i id = l := by
   simp [modify]
 
+@[grind _=_]
 theorem take_modify (f : α → α) (i j) (l : List α) :
     (l.modify i f).take j = (l.take j).modify i f := by
   induction j generalizing l i with
@@ -257,6 +271,7 @@ theorem take_modify (f : α → α) (i j) (l : List α) :
       | zero => simp
       | succ i => simp [ih]
 
+@[grind =]
 theorem drop_modify_of_lt (f : α → α) (i j) (l : List α) (h : i < j) :
     (l.modify i f).drop j = l.drop j := by
   apply ext_getElem
@@ -266,6 +281,7 @@ theorem drop_modify_of_lt (f : α → α) (i j) (l : List α) (h : i < j) :
     intro h'
     omega
 
+@[grind =]
 theorem drop_modify_of_ge (f : α → α) (i j) (l : List α) (h : i ≥ j) :
     (l.modify i f).drop j = (l.drop j).modify (i - j) f  := by
   apply ext_getElem

src/Init/Data/List/Nat/Pairwise.lean

@@ -55,7 +55,7 @@ theorem sublist_eq_map_getElem {l l' : List α} (h : l' <+ l) : ∃ is : List (F
     simp [Function.comp_def, pairwise_map, IH, ← get_eq_getElem, get_cons_zero, get_cons_succ']
 
 set_option linter.listVariables false in
-theorem pairwise_iff_getElem : Pairwise R l ↔
+theorem pairwise_iff_getElem {l : List α} : Pairwise R l ↔
     ∀ (i j : Nat) (_hi : i < l.length) (_hj : j < l.length) (_hij : i < j), R l[i] l[j] := by
   rw [pairwise_iff_forall_sublist]
   constructor <;> intro h

src/Init/Data/List/Nat/Range.lean

@@ -27,11 +27,12 @@ open Nat
 
 /-! ### range' -/
 
-@[simp] theorem mem_range'_1 : m ∈ range' s n ↔ s ≤ m ∧ m < s + n := by
+@[simp, grind =] theorem mem_range'_1 : m ∈ range' s n ↔ s ≤ m ∧ m < s + n := by
   simp [mem_range']; exact ⟨
     fun ⟨i, h, e⟩ => e ▸ ⟨Nat.le_add_right .., Nat.add_lt_add_left h _⟩,
     fun ⟨h₁, h₂⟩ => ⟨m - s, Nat.sub_lt_left_of_lt_add h₁ h₂, (Nat.add_sub_cancel' h₁).symm⟩⟩
 
+@[grind =]
 theorem getLast?_range' {n : Nat} : (range' s n).getLast? = if n = 0 then none else some (s + n - 1) := by
   induction n generalizing s with
   | zero => simp
@@ -43,7 +44,7 @@ theorem getLast?_range' {n : Nat} : (range' s n).getLast? = if n = 0 then none e
     · rw [if_neg h]
       simp
 
-@[simp] theorem getLast_range' {n : Nat} (h) : (range' s n).getLast h = s + n - 1 := by
+@[simp, grind =] theorem getLast_range' {n : Nat} (h) : (range' s n).getLast h = s + n - 1 := by
   cases n with
   | zero => simp at h
   | succ n => simp [getLast?_range', getLast_eq_iff_getLast?_eq_some]
@@ -158,6 +159,26 @@ theorem erase_range' :
       simp [p]
       omega
 
+@[simp, grind =]
+theorem count_range' {a s n step} (h : 0 < step := by simp) :
+    count a (range' s n step) = if ∃ i, i < n ∧ a = s + step * i then 1 else 0 := by
+  rw [(nodup_range' step h).count]
+  simp only [mem_range']
+
+@[simp, grind =]
+theorem count_range_1' {a s n} :
+    count a (range' s n) = if s ≤ a ∧ a < s + n then 1 else 0 := by
+  rw [count_range' (by simp)]
+  split <;> rename_i h
+  · obtain ⟨i, h, rfl⟩ := h
+    simp [h]
+  · simp at h
+    rw [if_neg]
+    simp only [not_and, Nat.not_lt]
+    intro w
+    specialize h (a - s)
+    omega
+
 /-! ### range -/
 
 theorem reverse_range' : ∀ {s n : Nat}, reverse (range' s n) = map (s + n - 1 - ·) (range n)
@@ -167,7 +188,7 @@ theorem reverse_range' : ∀ {s n : Nat}, reverse (range' s n) = map (s + n - 1
       show s + (n + 1) - 1 = s + n from rfl, map, map_map]
     simp [reverse_range', Nat.sub_right_comm, Nat.sub_sub]
 
-@[simp]
+@[simp, grind =]
 theorem mem_range {m n : Nat} : m ∈ range n ↔ m < n := by
   simp only [range_eq_range', mem_range'_1, Nat.zero_le, true_and, Nat.zero_add]
 
@@ -181,7 +202,7 @@ theorem pairwise_lt_range {n : Nat} : Pairwise (· < ·) (range n) := by
 theorem pairwise_le_range {n : Nat} : Pairwise (· ≤ ·) (range n) :=
   Pairwise.imp Nat.le_of_lt pairwise_lt_range
 
-@[simp] theorem take_range {i n : Nat} : take i (range n) = range (min i n) := by
+@[simp, grind =] theorem take_range {i n : Nat} : take i (range n) = range (min i n) := by
   apply List.ext_getElem
   · simp
   · simp +contextual [getElem_take, Nat.lt_min]
@@ -189,10 +210,11 @@ theorem pairwise_le_range {n : Nat} : Pairwise (· ≤ ·) (range n) :=
 theorem nodup_range {n : Nat} : Nodup (range n) := by
   simp +decide only [range_eq_range', nodup_range']
 
-@[simp] theorem find?_range_eq_some {n : Nat} {i : Nat} {p : Nat → Bool} :
+@[simp, grind] theorem find?_range_eq_some {n : Nat} {i : Nat} {p : Nat → Bool} :
     (range n).find? p = some i ↔ p i ∧ i ∈ range n ∧ ∀ j, j < i → !p j := by
   simp [range_eq_range']
 
+@[grind]
 theorem find?_range_eq_none {n : Nat} {p : Nat → Bool} :
     (range n).find? p = none ↔ ∀ i, i < n → !p i := by
   simp
@@ -200,6 +222,12 @@ theorem find?_range_eq_none {n : Nat} {p : Nat → Bool} :
 theorem erase_range : (range n).erase i = range (min n i) ++ range' (i + 1) (n - (i + 1)) := by
   simp [range_eq_range', erase_range']
 
+@[simp, grind =]
+theorem count_range {a n} :
+    count a (range n) = if a < n then 1 else 0 := by
+  rw [range_eq_range', count_range_1']
+  simp
+
 /-! ### iota -/
 
 section
@@ -348,15 +376,15 @@ end
 
 /-! ### zipIdx -/
 
-@[simp]
+@[simp, grind =]
 theorem zipIdx_singleton {x : α} {k : Nat} : zipIdx [x] k = [(x, k)] :=
   rfl
 
-@[simp] theorem head?_zipIdx {l : List α} {k : Nat} :
+@[simp, grind =] theorem head?_zipIdx {l : List α} {k : Nat} :
     (zipIdx l k).head? = l.head?.map fun a => (a, k) := by
   simp [head?_eq_getElem?]
 
-@[simp] theorem getLast?_zipIdx {l : List α} {k : Nat} :
+@[simp, grind =] theorem getLast?_zipIdx {l : List α} {k : Nat} :
     (zipIdx l k).getLast? = l.getLast?.map fun a => (a, k + l.length - 1) := by
   simp [getLast?_eq_getElem?]
   cases l <;> simp
@@ -379,6 +407,7 @@ to avoid the inequality and the subtraction. -/
 theorem mk_mem_zipIdx_iff_getElem? {i : Nat} {x : α} {l : List α} : (x, i) ∈ zipIdx l ↔ l[i]? = some x := by
   simp [mk_mem_zipIdx_iff_le_and_getElem?_sub]
 
+@[grind =]
 theorem mem_zipIdx_iff_le_and_getElem?_sub {x : α × Nat} {l : List α} {k : Nat} :
     x ∈ zipIdx l k ↔ k ≤ x.2 ∧ l[x.2 - k]? = some x.1 := by
   cases x
@@ -441,6 +470,7 @@ theorem zipIdx_map {l : List α} {k : Nat} {f : α → β} :
     rw [map_cons, zipIdx_cons', zipIdx_cons', map_cons, map_map, IH, map_map]
     rfl
 
+@[grind =]
 theorem zipIdx_append {xs ys : List α} {k : Nat} :
     zipIdx (xs ++ ys) k = zipIdx xs k ++ zipIdx ys (k + xs.length) := by
   induction xs generalizing ys k with
@@ -617,9 +647,6 @@ set_option linter.deprecated false
 @[deprecated zipIdx_eq_nil_iff (since := "2025-01-21"), simp]
 theorem enum_eq_nil_iff {l : List α} : List.enum l = [] ↔ l = [] := enumFrom_eq_nil
 
-@[deprecated zipIdx_eq_nil_iff (since := "2024-11-04")]
-theorem enum_eq_nil {l : List α} : List.enum l = [] ↔ l = [] := enum_eq_nil_iff
-
 @[deprecated zipIdx_singleton (since := "2025-01-21"), simp]
 theorem enum_singleton (x : α) : enum [x] = [(0, x)] := rfl
 

src/Init/Data/List/Nat/Sublist.lean

@@ -30,7 +30,7 @@ theorem IsSuffix.getElem {xs ys : List α} (h : xs <:+ ys) {i} (hn : i < xs.leng
   have := h.length_le
   omega
 
-theorem isSuffix_iff : l₁ <:+ l₂ ↔
+theorem suffix_iff_getElem? {l₁ l₂ : List α} : l₁ <:+ l₂ ↔
     l₁.length ≤ l₂.length ∧ ∀ i (h : i < l₁.length), l₂[i + l₂.length - l₁.length]? = some l₁[i] := by
   suffices l₁.length ≤ l₂.length ∧ l₁ <:+ l₂ ↔
       l₁.length ≤ l₂.length ∧ ∀ i (h : i < l₁.length), l₂[i + l₂.length - l₁.length]? = some l₁[i] by
@@ -41,7 +41,7 @@ theorem isSuffix_iff : l₁ <:+ l₂ ↔
       exact (this.mpr h).2
   simp only [and_congr_right_iff]
   intro le
-  rw [← reverse_prefix, isPrefix_iff]
+  rw [← reverse_prefix, prefix_iff_getElem?]
   simp only [length_reverse]
   constructor
   · intro w i h
@@ -60,15 +60,33 @@ theorem isSuffix_iff : l₁ <:+ l₂ ↔
     rw [w, getElem_reverse]
     exact Nat.lt_of_lt_of_le h le
 
-theorem isInfix_iff : l₁ <:+: l₂ ↔
+@[deprecated suffix_iff_getElem? (since := "2025-05-27")]
+abbrev isSuffix_iff := @suffix_iff_getElem?
+
+theorem suffix_iff_getElem {l₁ l₂ : List α} :
+    l₁ <:+ l₂ ↔ ∃ (_ : l₁.length ≤ l₂.length), ∀ i (_ : i < l₁.length), l₂[i + l₂.length - l₁.length] = l₁[i] := by
+  rw [suffix_iff_getElem?]
+  constructor
+  · rintro ⟨h, w⟩
+    refine ⟨h, fun i h => ?_⟩
+    specialize w i h
+    rw [getElem?_eq_getElem] at w
+    simpa using w
+  · rintro ⟨h, w⟩
+    refine ⟨h, fun i h => ?_⟩
+    specialize w i h
+    rw [getElem?_eq_getElem]
+    simpa using w
+
+theorem infix_iff_getElem? {l₁ l₂ : List α} : l₁ <:+: l₂ ↔
     ∃ k, l₁.length + k ≤ l₂.length ∧ ∀ i (h : i < l₁.length), l₂[i + k]? = some l₁[i] := by
   constructor
   · intro h
     obtain ⟨t, p, s⟩ := infix_iff_suffix_prefix.mp h
     refine ⟨t.length - l₁.length, by have := p.length_le; have := s.length_le; omega, ?_⟩
-    rw [isSuffix_iff] at p
+    rw [suffix_iff_getElem?] at p
     obtain ⟨p', p⟩ := p
-    rw [isPrefix_iff] at s
+    rw [prefix_iff_getElem?] at s
     intro i h
     rw [s _ (by omega)]
     specialize p i (by omega)
@@ -93,10 +111,14 @@ theorem isInfix_iff : l₁ <:+: l₂ ↔
       simp_all
       omega
 
+@[deprecated infix_iff_getElem? (since := "2025-05-27")]
+abbrev isInfix_iff := @infix_iff_getElem?
+
 theorem suffix_iff_eq_append : l₁ <:+ l₂ ↔ take (length l₂ - length l₁) l₂ ++ l₁ = l₂ :=
   ⟨by rintro ⟨r, rfl⟩; simp only [length_append, Nat.add_sub_cancel_right, take_left], fun e =>
     ⟨_, e⟩⟩
 
+@[grind =]
 theorem prefix_take_iff {xs ys : List α} {i : Nat} : xs <+: ys.take i ↔ xs <+: ys ∧ xs.length ≤ i := by
   constructor
   · intro h
@@ -115,7 +137,7 @@ theorem suffix_iff_eq_drop : l₁ <:+ l₂ ↔ l₁ = drop (length l₂ - length
   ⟨fun h => append_cancel_left <| (suffix_iff_eq_append.1 h).trans (take_append_drop _ _).symm,
     fun e => e.symm ▸ drop_suffix _ _⟩
 
-theorem prefix_take_le_iff {xs : List α} (hm : i < xs.length) :
+@[grind =] theorem prefix_take_le_iff {xs : List α} (hm : i < xs.length) :
     xs.take i <+: xs.take j ↔ i ≤ j := by
   simp only [prefix_iff_eq_take, length_take]
   induction i generalizing xs j with

src/Init/Data/List/Nat/TakeDrop.lean

@@ -56,7 +56,7 @@ theorem getElem?_take_eq_none {l : List α} {i j : Nat} (h : i ≤ j) :
     (l.take i)[j]? = none :=
   getElem?_eq_none <| Nat.le_trans (length_take_le _ _) h
 
-@[grind =]theorem getElem?_take {l : List α} {i j : Nat} :
+@[grind =] theorem getElem?_take {l : List α} {i j : Nat} :
     (l.take i)[j]? = if j < i then l[j]? else none := by
   split
   · next h => exact getElem?_take_of_lt h
@@ -99,6 +99,7 @@ theorem getLast_take {l : List α} (h : l.take i ≠ []) :
   · rw [getElem?_eq_none (by omega), getLast_eq_getElem]
     simp
 
+@[grind =]
 theorem take_take : ∀ {i j} {l : List α}, take i (take j l) = take (min i j) l
   | n, 0, l => by rw [Nat.min_zero, take_zero, take_nil]
   | 0, m, l => by rw [Nat.zero_min, take_zero, take_zero]
@@ -117,19 +118,19 @@ theorem take_set_of_le {a : α} {i j : Nat} {l : List α} (h : j ≤ i) :
 @[deprecated take_set_of_le (since := "2025-02-04")]
 abbrev take_set_of_lt := @take_set_of_le
 
-@[simp] theorem take_replicate {a : α} : ∀ {i n : Nat}, take i (replicate n a) = replicate (min i n) a
+@[simp, grind =] theorem take_replicate {a : α} : ∀ {i n : Nat}, take i (replicate n a) = replicate (min i n) a
   | n, 0 => by simp [Nat.min_zero]
   | 0, m => by simp [Nat.zero_min]
   | succ n, succ m => by simp [replicate_succ, succ_min_succ, take_replicate]
 
-@[simp] theorem drop_replicate {a : α} : ∀ {i n : Nat}, drop i (replicate n a) = replicate (n - i) a
+@[simp, grind =] theorem drop_replicate {a : α} : ∀ {i n : Nat}, drop i (replicate n a) = replicate (n - i) a
   | n, 0 => by simp
   | 0, m => by simp
   | succ n, succ m => by simp [replicate_succ, succ_sub_succ, drop_replicate]
 
 /-- Taking the first `i` elements in `l₁ ++ l₂` is the same as appending the first `i` elements
 of `l₁` to the first `n - l₁.length` elements of `l₂`. -/
-theorem take_append_eq_append_take {l₁ l₂ : List α} {i : Nat} :
+theorem take_append {l₁ l₂ : List α} {i : Nat} :
     take i (l₁ ++ l₂) = take i l₁ ++ take (i - l₁.length) l₂ := by
   induction l₁ generalizing i
   · simp
@@ -140,15 +141,18 @@ theorem take_append_eq_append_take {l₁ l₂ : List α} {i : Nat} :
       congr 1
       omega
 
+@[deprecated take_append (since := "2025-06-16")]
+abbrev take_append_eq_append_take := @take_append
+
 theorem take_append_of_le_length {l₁ l₂ : List α} {i : Nat} (h : i ≤ l₁.length) :
     (l₁ ++ l₂).take i = l₁.take i := by
-  simp [take_append_eq_append_take, Nat.sub_eq_zero_of_le h]
+  simp [take_append, Nat.sub_eq_zero_of_le h]
 
 /-- Taking the first `l₁.length + i` elements in `l₁ ++ l₂` is the same as appending the first
 `i` elements of `l₂` to `l₁`. -/
-theorem take_append {l₁ l₂ : List α} (i : Nat) :
+theorem take_length_add_append {l₁ l₂ : List α} (i : Nat) :
     take (l₁.length + i) (l₁ ++ l₂) = l₁ ++ take i l₂ := by
-  rw [take_append_eq_append_take, take_of_length_le (Nat.le_add_right _ _), Nat.add_sub_cancel_left]
+  rw [take_append, take_of_length_le (Nat.le_add_right _ _), Nat.add_sub_cancel_left]
 
 @[simp]
 theorem take_eq_take_iff :
@@ -162,11 +166,12 @@ theorem take_eq_take_iff :
 @[deprecated take_eq_take_iff (since := "2025-02-16")]
 abbrev take_eq_take := @take_eq_take_iff
 
+@[grind =]
 theorem take_add {l : List α} {i j : Nat} : l.take (i + j) = l.take i ++ (l.drop i).take j := by
   suffices take (i + j) (take i l ++ drop i l) = take i l ++ take j (drop i l) by
     rw [take_append_drop] at this
     assumption
-  rw [take_append_eq_append_take, take_of_length_le, append_right_inj]
+  rw [take_append, take_of_length_le, append_right_inj]
   · simp only [take_eq_take_iff, length_take, length_drop]
     omega
   apply Nat.le_trans (m := i)
@@ -199,7 +204,7 @@ theorem take_eq_dropLast {l : List α} {i : Nat} (h : i + 1 = l.length) :
         simpa using h
 
 theorem take_prefix_take_left {l : List α} {i j : Nat} (h : i ≤ j) : take i l <+: take j l := by
-  rw [isPrefix_iff]
+  rw [prefix_iff_getElem?]
   intro i w
   rw [getElem?_take_of_lt, getElem_take, getElem?_eq_getElem]
   simp only [length_take] at w
@@ -236,7 +241,7 @@ dropping the first `i` elements. Version designed to rewrite from the small list
       exact Nat.add_lt_of_lt_sub (length_drop ▸ h)) := by
   rw [getElem_drop']
 
-@[simp]
+@[simp, grind =]
 theorem getElem?_drop {xs : List α} {i j : Nat} : (xs.drop i)[j]? = xs[i + j]? := by
   ext
   simp only [getElem?_eq_some_iff, getElem_drop]
@@ -285,7 +290,7 @@ theorem getLast?_drop {l : List α} : (l.drop i).getLast? = if l.length ≤ i th
     congr
     omega
 
-@[simp] theorem getLast_drop {l : List α} (h : l.drop i ≠ []) :
+@[simp, grind =] theorem getLast_drop {l : List α} (h : l.drop i ≠ []) :
     (l.drop i).getLast h = l.getLast (ne_nil_of_length_pos (by simp at h; omega)) := by
   simp only [ne_eq, drop_eq_nil_iff] at h
   apply Option.some_inj.1
@@ -306,7 +311,8 @@ theorem drop_length_cons {l : List α} (h : l ≠ []) (a : α) :
 
 /-- Dropping the elements up to `i` in `l₁ ++ l₂` is the same as dropping the elements up to `i`
 in `l₁`, dropping the elements up to `i - l₁.length` in `l₂`, and appending them. -/
-theorem drop_append_eq_append_drop {l₁ l₂ : List α} {i : Nat} :
+@[grind =]
+theorem drop_append {l₁ l₂ : List α} {i : Nat} :
     drop i (l₁ ++ l₂) = drop i l₁ ++ drop (i - l₁.length) l₂ := by
   induction l₁ generalizing i
   · simp
@@ -316,15 +322,18 @@ theorem drop_append_eq_append_drop {l₁ l₂ : List α} {i : Nat} :
       congr 1
       omega
 
+@[deprecated drop_append (since := "2025-06-16")]
+abbrev drop_append_eq_append_drop := @drop_append
+
 theorem drop_append_of_le_length {l₁ l₂ : List α} {i : Nat} (h : i ≤ l₁.length) :
     (l₁ ++ l₂).drop i = l₁.drop i ++ l₂ := by
-  simp [drop_append_eq_append_drop, Nat.sub_eq_zero_of_le h]
+  simp [drop_append, Nat.sub_eq_zero_of_le h]
 
 /-- Dropping the elements up to `l₁.length + i` in `l₁ + l₂` is the same as dropping the elements
 up to `i` in `l₂`. -/
 @[simp]
-theorem drop_append {l₁ l₂ : List α} (i : Nat) : drop (l₁.length + i) (l₁ ++ l₂) = drop i l₂ := by
-  rw [drop_append_eq_append_drop, drop_eq_nil_of_le] <;>
+theorem drop_length_add_append {l₁ l₂ : List α} (i : Nat) : drop (l₁.length + i) (l₁ ++ l₂) = drop i l₂ := by
+  rw [drop_append, drop_eq_nil_of_le] <;>
     simp [Nat.add_sub_cancel_left, Nat.le_add_right]
 
 theorem set_eq_take_append_cons_drop {l : List α} {i : Nat} {a : α} :
@@ -458,7 +467,7 @@ theorem false_of_mem_take_findIdx {xs : List α} {p : α → Bool} (h : x ∈ xs
   obtain ⟨i, h, rfl⟩ := h
   exact not_of_lt_findIdx (by omega)
 
-@[simp] theorem findIdx_take {xs : List α} {i : Nat} {p : α → Bool} :
+@[simp, grind =] theorem findIdx_take {xs : List α} {i : Nat} {p : α → Bool} :
     (xs.take i).findIdx p = min i (xs.findIdx p) := by
   induction xs generalizing i with
   | nil => simp
@@ -470,7 +479,7 @@ theorem false_of_mem_take_findIdx {xs : List α} {p : α → Bool} (h : x ∈ xs
       · simp
       · rw [Nat.add_min_add_right]
 
-@[simp] theorem min_findIdx_findIdx {xs : List α} {p q : α → Bool} :
+@[simp, grind =] theorem min_findIdx_findIdx {xs : List α} {p q : α → Bool} :
     min (xs.findIdx p) (xs.findIdx q) = xs.findIdx (fun a => p a || q a) := by
   induction xs with
   | nil => simp
@@ -512,7 +521,7 @@ theorem dropWhile_eq_drop_findIdx_not {xs : List α} {p : α → Bool} :
 
 /-! ### rotateLeft -/
 
-@[simp] theorem rotateLeft_replicate {n} {a : α} : rotateLeft (replicate m a) n = replicate m a := by
+@[simp, grind =] theorem rotateLeft_replicate {n} {a : α} : rotateLeft (replicate m a) n = replicate m a := by
   cases n with
   | zero => simp
   | succ n =>
@@ -525,7 +534,7 @@ theorem dropWhile_eq_drop_findIdx_not {xs : List α} {p : α → Bool} :
 
 /-! ### rotateRight -/
 
-@[simp] theorem rotateRight_replicate {n} {a : α} : rotateRight (replicate m a) n = replicate m a := by
+@[simp, grind =] theorem rotateRight_replicate {n} {a : α} : rotateRight (replicate m a) n = replicate m a := by
   cases n with
   | zero => simp
   | succ n =>
@@ -538,7 +547,7 @@ theorem dropWhile_eq_drop_findIdx_not {xs : List α} {p : α → Bool} :
 
 /-! ### zipWith -/
 
-@[simp] theorem length_zipWith {f : α → β → γ} {l₁ : List α} {l₂ : List β} :
+@[simp, grind =] theorem length_zipWith {f : α → β → γ} {l₁ : List α} {l₂ : List β} :
     length (zipWith f l₁ l₂) = min (length l₁) (length l₂) := by
   induction l₁ generalizing l₂ <;> cases l₂ <;>
     simp_all [succ_min_succ, Nat.zero_min, Nat.min_zero]
@@ -549,7 +558,7 @@ theorem lt_length_left_of_zipWith {f : α → β → γ} {i : Nat} {l : List α}
 theorem lt_length_right_of_zipWith {f : α → β → γ} {i : Nat} {l : List α} {l' : List β}
     (h : i < (zipWith f l l').length) : i < l'.length := by rw [length_zipWith] at h; omega
 
-@[simp]
+@[simp, grind =]
 theorem getElem_zipWith {f : α → β → γ} {l : List α} {l' : List β}
     {i : Nat} {h : i < (zipWith f l l').length} :
     (zipWith f l l')[i] =
@@ -566,6 +575,7 @@ theorem zipWith_eq_zipWith_take_min : ∀ {l₁ : List α} {l₂ : List β},
   | _, [] => by simp
   | a :: l₁, b :: l₂ => by simp [succ_min_succ, zipWith_eq_zipWith_take_min (l₁ := l₁) (l₂ := l₂)]
 
+@[grind =]
 theorem reverse_zipWith (h : l.length = l'.length) :
     (zipWith f l l').reverse = zipWith f l.reverse l'.reverse := by
   induction l generalizing l' with
@@ -578,14 +588,14 @@ theorem reverse_zipWith (h : l.length = l'.length) :
       have : tl.reverse.length = tl'.reverse.length := by simp [h]
       simp [hl h, zipWith_append this]
 
-@[simp] theorem zipWith_replicate {a : α} {b : β} {m n : Nat} :
+@[simp, grind =] theorem zipWith_replicate {a : α} {b : β} {m n : Nat} :
     zipWith f (replicate m a) (replicate n b) = replicate (min m n) (f a b) := by
   rw [zipWith_eq_zipWith_take_min]
   simp
 
 /-! ### zip -/
 
-@[simp] theorem length_zip {l₁ : List α} {l₂ : List β} :
+@[simp, grind =] theorem length_zip {l₁ : List α} {l₂ : List β} :
     length (zip l₁ l₂) = min (length l₁) (length l₂) := by
   simp [zip]
 
@@ -597,7 +607,7 @@ theorem lt_length_right_of_zip {i : Nat} {l : List α} {l' : List β} (h : i < (
     i < l'.length :=
   lt_length_right_of_zipWith h
 
-@[simp]
+@[simp, grind =]
 theorem getElem_zip {l : List α} {l' : List β} {i : Nat} {h : i < (zip l l').length} :
     (zip l l')[i] =
       (l[i]'(lt_length_left_of_zip h), l'[i]'(lt_length_right_of_zip h)) :=
@@ -609,7 +619,7 @@ theorem zip_eq_zip_take_min : ∀ {l₁ : List α} {l₂ : List β},
   | _, [] => by simp
   | a :: l₁, b :: l₂ => by simp [succ_min_succ, zip_eq_zip_take_min (l₁ := l₁) (l₂ := l₂)]
 
-@[simp] theorem zip_replicate {a : α} {b : β} {m n : Nat} :
+@[simp, grind =] theorem zip_replicate {a : α} {b : β} {m n : Nat} :
     zip (replicate m a) (replicate n b) = replicate (min m n) (a, b) := by
   rw [zip_eq_zip_take_min]
   simp

src/Init/Data/List/Notation.lean

@@ -6,7 +6,7 @@ Author: Leonardo de Moura
 module
 
 prelude
-import Init.Data.Nat.Div.Basic
+meta import Init.Data.Nat.Div.Basic
 
 /-!
 # Notation for `List` literals.

src/Init/Data/List/OfFn.lean

@@ -27,14 +27,21 @@ Examples:
 -/
 def ofFn {n} (f : Fin n → α) : List α := Fin.foldr n (f · :: ·) []
 
-@[simp]
+/--
+Creates a list wrapped in a monad by applying the monadic function `f : Fin n → m α`
+to each potential index in order, starting at `0`.
+-/
+def ofFnM {n} [Monad m] (f : Fin n → m α) : m (List α) :=
+  List.reverse <$> Fin.foldlM n (fun xs i => (· :: xs) <$> f i) []
+
+@[simp, grind =]
 theorem length_ofFn {f : Fin n → α} : (ofFn f).length = n := by
   simp only [ofFn]
   induction n with
   | zero => simp
   | succ n ih => simp [Fin.foldr_succ, ih]
 
-@[simp]
+@[simp, grind =]
 protected theorem getElem_ofFn {f : Fin n → α} (h : i < (ofFn f).length) :
     (ofFn f)[i] = f ⟨i, by simp_all⟩ := by
   simp only [ofFn]
@@ -48,8 +55,9 @@ protected theorem getElem_ofFn {f : Fin n → α} (h : i < (ofFn f).length) :
       apply ih
       simp_all
 
-@[simp]
-protected theorem getElem?_ofFn {f : Fin n → α} : (ofFn f)[i]? = if h : i < n then some (f ⟨i, h⟩) else none :=
+@[simp, grind =]
+protected theorem getElem?_ofFn {f : Fin n → α} :
+    (ofFn f)[i]? = if h : i < n then some (f ⟨i, h⟩) else none :=
   if h : i < (ofFn f).length
   then by
     rw [getElem?_eq_getElem h, List.getElem_ofFn]
@@ -59,9 +67,9 @@ protected theorem getElem?_ofFn {f : Fin n → α} : (ofFn f)[i]? = if h : i < n
     simpa using h
 
 /-- `ofFn` on an empty domain is the empty list. -/
-@[simp]
-theorem ofFn_zero {f : Fin 0 → α} : ofFn f = [] :=
-  ext_get (by simp) (fun i hi₁ hi₂ => by contradiction)
+@[simp, grind =]
+theorem ofFn_zero {f : Fin 0 → α} : ofFn f = [] := by
+  rw [ofFn, Fin.foldr_zero]
 
 @[simp]
 theorem ofFn_succ {n} {f : Fin (n + 1) → α} : ofFn f = f 0 :: ofFn fun i => f i.succ :=
@@ -70,11 +78,27 @@ theorem ofFn_succ {n} {f : Fin (n + 1) → α} : ofFn f = f 0 :: ofFn fun i => f
     · simp
     · simp)
 
+theorem ofFn_succ_last {n} {f : Fin (n + 1) → α} :
+    ofFn f = (ofFn fun i => f i.castSucc) ++ [f (Fin.last n)] := by
+  induction n with
+  | zero => simp [ofFn_succ]
+  | succ n ih =>
+    rw [ofFn_succ]
+    conv => rhs; rw [ofFn_succ]
+    rw [ih]
+    simp
+
+theorem ofFn_add {n m} {f : Fin (n + m) → α} :
+    ofFn f = (ofFn fun i => f (i.castLE (Nat.le_add_right n m))) ++ (ofFn fun i => f (i.natAdd n)) := by
+  induction m with
+  | zero => simp
+  | succ m ih => simp [-ofFn_succ, ofFn_succ_last, ih]
+
 @[simp]
 theorem ofFn_eq_nil_iff {f : Fin n → α} : ofFn f = [] ↔ n = 0 := by
   cases n <;> simp only [ofFn_zero, ofFn_succ, eq_self_iff_true, Nat.succ_ne_zero, reduceCtorEq]
 
-@[simp 500]
+@[simp 500, grind =]
 theorem mem_ofFn {n} {f : Fin n → α} {a : α} : a ∈ ofFn f ↔ ∃ i, f i = a := by
   constructor
   · intro w
@@ -83,13 +107,74 @@ theorem mem_ofFn {n} {f : Fin n → α} {a : α} : a ∈ ofFn f ↔ ∃ i, f i =
   · rintro ⟨i, rfl⟩
     apply mem_of_getElem (i := i) <;> simp
 
-theorem head_ofFn {n} {f : Fin n → α} (h : ofFn f ≠ []) :
+@[grind =] theorem head_ofFn {n} {f : Fin n → α} (h : ofFn f ≠ []) :
     (ofFn f).head h = f ⟨0, Nat.pos_of_ne_zero (mt ofFn_eq_nil_iff.2 h)⟩ := by
   rw [← getElem_zero (length_ofFn ▸ Nat.pos_of_ne_zero (mt ofFn_eq_nil_iff.2 h)),
     List.getElem_ofFn]
 
-theorem getLast_ofFn {n} {f : Fin n → α} (h : ofFn f ≠ []) :
+@[grind =]theorem getLast_ofFn {n} {f : Fin n → α} (h : ofFn f ≠ []) :
     (ofFn f).getLast h = f ⟨n - 1, Nat.sub_one_lt (mt ofFn_eq_nil_iff.2 h)⟩ := by
   simp [getLast_eq_getElem, length_ofFn, List.getElem_ofFn]
 
+/-- `ofFnM` on an empty domain is the empty list. -/
+@[simp, grind =]
+theorem ofFnM_zero [Monad m] [LawfulMonad m] {f : Fin 0 → m α} : ofFnM f = pure [] := by
+  simp [ofFnM]
+
+/-! See `Init.Data.List.FinRange` for the `ofFnM_succ` variant. -/
+
+theorem ofFnM_succ_last {n} [Monad m] [LawfulMonad m] {f : Fin (n + 1) → m α} :
+    ofFnM f = (do
+      let as ← ofFnM fun i => f i.castSucc
+      let a  ← f (Fin.last n)
+      pure (as ++ [a])) := by
+  simp [ofFnM, Fin.foldlM_succ_last]
+
+theorem ofFnM_add {n m} [Monad m] [LawfulMonad m] {f : Fin (n + k) → m α} :
+    ofFnM f = (do
+      let as ← ofFnM fun i : Fin n => f (i.castLE (Nat.le_add_right n k))
+      let bs ← ofFnM fun i : Fin k => f (i.natAdd n)
+      pure (as ++ bs)) := by
+  induction k with
+  | zero => simp
+  | succ k ih => simp [ofFnM_succ_last, ih]
+
+
+end List
+
+namespace Fin
+
+theorem foldl_cons_eq_append {f : Fin n → α} {xs : List α} :
+    Fin.foldl n (fun xs i => f i :: xs) xs = (List.ofFn f).reverse ++ xs := by
+  induction n generalizing xs with
+  | zero => simp
+  | succ n ih => simp [Fin.foldl_succ, List.ofFn_succ, ih]
+
+theorem foldr_cons_eq_append {f : Fin n → α} {xs : List α} :
+    Fin.foldr n (fun i xs => f i :: xs) xs = List.ofFn f ++ xs:= by
+  induction n generalizing xs with
+  | zero => simp
+  | succ n ih => simp [Fin.foldr_succ, List.ofFn_succ, ih]
+
+end Fin
+
+namespace List
+
+@[simp]
+theorem ofFnM_pure_comp [Monad m] [LawfulMonad m] {n} {f : Fin n → α} :
+    ofFnM (pure ∘ f) = (pure (ofFn f) : m (List α)) := by
+  simp [ofFnM, Fin.foldlM_pure, Fin.foldl_cons_eq_append]
+
+-- Variant of `ofFnM_pure_comp` using a lambda.
+-- This is not marked a `@[simp]` as it would match on every occurrence of `ofFnM`.
+theorem ofFnM_pure [Monad m] [LawfulMonad m] {n} {f : Fin n → α} :
+    ofFnM (fun i => pure (f i)) = (pure (ofFn f) : m (List α)) :=
+  ofFnM_pure_comp
+
+@[simp, grind =] theorem idRun_ofFnM {f : Fin n → Id α} :
+    Id.run (ofFnM f) = ofFn (fun i => Id.run (f i)) := by
+  induction n with
+  | zero => simp
+  | succ n ih => simp [-ofFn_succ, ofFnM_succ_last, ofFn_succ_last, ih]
+
 end List

src/Init/Data/List/Pairwise.lean

@@ -24,7 +24,7 @@ open Nat
 
 /-! ### Pairwise -/
 
-theorem Pairwise.sublist : l₁ <+ l₂ → l₂.Pairwise R → l₁.Pairwise R
+@[grind →] theorem Pairwise.sublist : l₁ <+ l₂ → l₂.Pairwise R → l₁.Pairwise R
   | .slnil, h => h
   | .cons _ s, .cons _ h₂ => h₂.sublist s
   | .cons₂ _ s, .cons h₁ h₂ => (h₂.sublist s).cons fun _ h => h₁ _ (s.subset h)
@@ -37,11 +37,11 @@ theorem Pairwise.imp {α R S} (H : ∀ {a b}, R a b → S a b) :
 theorem rel_of_pairwise_cons (p : (a :: l).Pairwise R) : ∀ {a'}, a' ∈ l → R a a' :=
   (pairwise_cons.1 p).1 _
 
-theorem Pairwise.of_cons (p : (a :: l).Pairwise R) : Pairwise R l :=
+@[grind →] theorem Pairwise.of_cons (p : (a :: l).Pairwise R) : Pairwise R l :=
   (pairwise_cons.1 p).2
 
 set_option linter.unusedVariables false in
-theorem Pairwise.tail : ∀ {l : List α} (h : Pairwise R l), Pairwise R l.tail
+@[grind] theorem Pairwise.tail : ∀ {l : List α} (h : Pairwise R l), Pairwise R l.tail
   | [], h => h
   | _ :: _, h => h.of_cons
 
@@ -101,11 +101,11 @@ theorem Pairwise.forall_of_forall_of_flip (h₁ : ∀ x ∈ l, R x x) (h₂ : Pa
     · exact h₃.1 _ hx
     · exact ih (fun x hx => h₁ _ <| mem_cons_of_mem _ hx) h₂.2 h₃.2 hx hy
 
-theorem pairwise_singleton (R) (a : α) : Pairwise R [a] := by simp
+@[grind] theorem pairwise_singleton (R) (a : α) : Pairwise R [a] := by simp
 
-theorem pairwise_pair {a b : α} : Pairwise R [a, b] ↔ R a b := by simp
+@[grind =] theorem pairwise_pair {a b : α} : Pairwise R [a, b] ↔ R a b := by simp
 
-theorem pairwise_map {l : List α} :
+@[grind =] theorem pairwise_map {l : List α} :
     (l.map f).Pairwise R ↔ l.Pairwise fun a b => R (f a) (f b) := by
   induction l
   · simp
@@ -115,11 +115,11 @@ theorem Pairwise.of_map {S : β → β → Prop} (f : α → β) (H : ∀ a b :
     (p : Pairwise S (map f l)) : Pairwise R l :=
   (pairwise_map.1 p).imp (H _ _)
 
-theorem Pairwise.map {S : β → β → Prop} (f : α → β) (H : ∀ a b : α, R a b → S (f a) (f b))
+@[grind] theorem Pairwise.map {S : β → β → Prop} (f : α → β) (H : ∀ a b : α, R a b → S (f a) (f b))
     (p : Pairwise R l) : Pairwise S (map f l) :=
   pairwise_map.2 <| p.imp (H _ _)
 
-theorem pairwise_filterMap {f : β → Option α} {l : List β} :
+@[grind =] theorem pairwise_filterMap {f : β → Option α} {l : List β} :
     Pairwise R (filterMap f l) ↔ Pairwise (fun a a' : β => ∀ b, f a = some b → ∀ b', f a' = some b' → R b b') l := by
   let _S (a a' : β) := ∀ b, f a = some b → ∀ b', f a' = some b' → R b b'
   induction l with
@@ -134,20 +134,20 @@ theorem pairwise_filterMap {f : β → Option α} {l : List β} :
     simpa [IH, e] using fun _ =>
       ⟨fun h a ha b hab => h _ _ ha hab, fun h a b ha hab => h _ ha _ hab⟩
 
-theorem Pairwise.filterMap {S : β → β → Prop} (f : α → Option β)
+@[grind] theorem Pairwise.filterMap {S : β → β → Prop} (f : α → Option β)
     (H : ∀ a a' : α, R a a' → ∀ b, f a = some b → ∀ b', f a' = some b' → S b b') {l : List α} (p : Pairwise R l) :
     Pairwise S (filterMap f l) :=
   pairwise_filterMap.2 <| p.imp (H _ _)
 
-theorem pairwise_filter {p : α → Prop} [DecidablePred p] {l : List α} :
+@[grind =] theorem pairwise_filter {p : α → Bool} {l : List α} :
     Pairwise R (filter p l) ↔ Pairwise (fun x y => p x → p y → R x y) l := by
   rw [← filterMap_eq_filter, pairwise_filterMap]
   simp
 
-theorem Pairwise.filter (p : α → Bool) : Pairwise R l → Pairwise R (filter p l) :=
+@[grind] theorem Pairwise.filter (p : α → Bool) : Pairwise R l → Pairwise R (filter p l) :=
   Pairwise.sublist filter_sublist
 
-theorem pairwise_append {l₁ l₂ : List α} :
+@[grind =] theorem pairwise_append {l₁ l₂ : List α} :
     (l₁ ++ l₂).Pairwise R ↔ l₁.Pairwise R ∧ l₂.Pairwise R ∧ ∀ a ∈ l₁, ∀ b ∈ l₂, R a b := by
   induction l₁ <;> simp [*, or_imp, forall_and, and_assoc, and_left_comm]
 
@@ -157,13 +157,13 @@ theorem pairwise_append_comm {R : α → α → Prop} (s : ∀ {x y}, R x y →
     (x : α) (xm : x ∈ l₂) (y : α) (ym : y ∈ l₁) : R x y := s (H y ym x xm)
   simp only [pairwise_append, and_left_comm]; rw [Iff.intro (this l₁ l₂) (this l₂ l₁)]
 
-theorem pairwise_middle {R : α → α → Prop} (s : ∀ {x y}, R x y → R y x) {a : α} {l₁ l₂ : List α} :
+@[grind =] theorem pairwise_middle {R : α → α → Prop} (s : ∀ {x y}, R x y → R y x) {a : α} {l₁ l₂ : List α} :
     Pairwise R (l₁ ++ a :: l₂) ↔ Pairwise R (a :: (l₁ ++ l₂)) := by
-  show Pairwise R (l₁ ++ ([a] ++ l₂)) ↔ Pairwise R ([a] ++ l₁ ++ l₂)
+  change Pairwise R (l₁ ++ ([a] ++ l₂)) ↔ Pairwise R ([a] ++ l₁ ++ l₂)
   rw [← append_assoc, pairwise_append, @pairwise_append _ _ ([a] ++ l₁), pairwise_append_comm s]
   simp only [mem_append, or_comm]
 
-theorem pairwise_flatten {L : List (List α)} :
+@[grind =] theorem pairwise_flatten {L : List (List α)} :
     Pairwise R (flatten L) ↔
       (∀ l ∈ L, Pairwise R l) ∧ Pairwise (fun l₁ l₂ => ∀ x ∈ l₁, ∀ y ∈ l₂, R x y) L := by
   induction L with
@@ -174,16 +174,16 @@ theorem pairwise_flatten {L : List (List α)} :
     rw [and_comm, and_congr_left_iff]
     intros; exact ⟨fun h l' b c d e => h c d e l' b, fun h c d e l' b => h l' b c d e⟩
 
-theorem pairwise_flatMap {R : β → β → Prop} {l : List α} {f : α → List β} :
+@[grind =] theorem pairwise_flatMap {R : β → β → Prop} {l : List α} {f : α → List β} :
     List.Pairwise R (l.flatMap f) ↔
       (∀ a ∈ l, Pairwise R (f a)) ∧ Pairwise (fun a₁ a₂ => ∀ x ∈ f a₁, ∀ y ∈ f a₂, R x y) l := by
   simp [List.flatMap, pairwise_flatten, pairwise_map]
 
-theorem pairwise_reverse {l : List α} :
+@[grind =] theorem pairwise_reverse {l : List α} :
     l.reverse.Pairwise R ↔ l.Pairwise (fun a b => R b a) := by
   induction l <;> simp [*, pairwise_append, and_comm]
 
-@[simp] theorem pairwise_replicate {n : Nat} {a : α} :
+@[simp, grind =] theorem pairwise_replicate {n : Nat} {a : α} :
     (replicate n a).Pairwise R ↔ n ≤ 1 ∨ R a a := by
   induction n with
   | zero => simp
@@ -205,12 +205,13 @@ theorem pairwise_reverse {l : List α} :
         simp
       · exact ⟨fun _ => h, Or.inr h⟩
 
-theorem Pairwise.drop {l : List α} {i : Nat} (h : List.Pairwise R l) : List.Pairwise R (l.drop i) :=
+@[grind] theorem Pairwise.drop {l : List α} {i : Nat} (h : List.Pairwise R l) : List.Pairwise R (l.drop i) :=
   h.sublist (drop_sublist _ _)
 
-theorem Pairwise.take {l : List α} {i : Nat} (h : List.Pairwise R l) : List.Pairwise R (l.take i) :=
+@[grind] theorem Pairwise.take {l : List α} {i : Nat} (h : List.Pairwise R l) : List.Pairwise R (l.take i) :=
   h.sublist (take_sublist _ _)
 
+@[grind =]
 theorem pairwise_iff_forall_sublist : l.Pairwise R ↔ (∀ {a b}, [a,b] <+ l → R a b) := by
   induction l with
   | nil => simp
@@ -247,7 +248,7 @@ theorem pairwise_of_forall_mem_list {l : List α} {r : α → α → Prop} (h :
   intro a b hab
   apply h <;> (apply hab.subset; simp)
 
-theorem pairwise_pmap {p : β → Prop} {f : ∀ b, p b → α} {l : List β} (h : ∀ x ∈ l, p x) :
+@[grind =] theorem pairwise_pmap {p : β → Prop} {f : ∀ b, p b → α} {l : List β} (h : ∀ x ∈ l, p x) :
     Pairwise R (l.pmap f h) ↔
       Pairwise (fun b₁ b₂ => ∀ (h₁ : p b₁) (h₂ : p b₂), R (f b₁ h₁) (f b₂ h₂)) l := by
   induction l with
@@ -259,7 +260,7 @@ theorem pairwise_pmap {p : β → Prop} {f : ∀ b, p b → α} {l : List β} (h
     rintro H _ b hb rfl
     exact H b hb _ _
 
-theorem Pairwise.pmap {l : List α} (hl : Pairwise R l) {p : α → Prop} {f : ∀ a, p a → β}
+@[grind] theorem Pairwise.pmap {l : List α} (hl : Pairwise R l) {p : α → Prop} {f : ∀ a, p a → β}
     (h : ∀ x ∈ l, p x) {S : β → β → Prop}
     (hS : ∀ ⦃x⦄ (hx : p x) ⦃y⦄ (hy : p y), R x y → S (f x hx) (f y hy)) :
     Pairwise S (l.pmap f h) := by
@@ -268,17 +269,26 @@ theorem Pairwise.pmap {l : List α} (hl : Pairwise R l) {p : α → Prop} {f :
 
 /-! ### Nodup -/
 
-@[simp]
+@[grind =] theorem nodup_iff_pairwise_ne : List.Nodup l ↔ List.Pairwise (· ≠ ·) l := Iff.rfl
+
+@[simp, grind]
 theorem nodup_nil : @Nodup α [] :=
   Pairwise.nil
 
-@[simp]
+@[simp, grind =]
 theorem nodup_cons {a : α} {l : List α} : Nodup (a :: l) ↔ a ∉ l ∧ Nodup l := by
   simp only [Nodup, pairwise_cons, forall_mem_ne]
 
+@[grind =] theorem nodup_append {l₁ l₂ : List α} :
+    (l₁ ++ l₂).Nodup ↔ l₁.Nodup ∧ l₂.Nodup ∧ ∀ a ∈ l₁, ∀ b ∈ l₂, a ≠ b :=
+  pairwise_append
+
 theorem Nodup.sublist : l₁ <+ l₂ → Nodup l₂ → Nodup l₁ :=
   Pairwise.sublist
 
+grind_pattern Nodup.sublist => l₁ <+ l₂, Nodup l₁
+grind_pattern Nodup.sublist => l₁ <+ l₂, Nodup l₂
+
 theorem Sublist.nodup : l₁ <+ l₂ → Nodup l₂ → Nodup l₁ :=
   Nodup.sublist
 
@@ -303,7 +313,51 @@ theorem getElem?_inj {xs : List α}
       rw [mem_iff_getElem?]
     exact ⟨_, h₂⟩; exact ⟨_ , h₂.symm⟩
 
-@[simp] theorem nodup_replicate {n : Nat} {a : α} :
+@[simp, grind =] theorem nodup_replicate {n : Nat} {a : α} :
     (replicate n a).Nodup ↔ n ≤ 1 := by simp [Nodup]
 
+theorem Nodup.count [BEq α] [LawfulBEq α] {a : α} {l : List α} (h : Nodup l) : count a l = if a ∈ l then 1 else 0 := by
+  split <;> rename_i h'
+  · obtain ⟨s, t, rfl⟩ := List.append_of_mem h'
+    rw [nodup_append] at h
+    simp_all
+    rw [count_eq_zero.mpr ?_, count_eq_zero.mpr ?_]
+    · exact h.2.1.1
+    · intro w
+      simpa using h.2.2 _ w
+  · rw [count_eq_zero_of_not_mem h']
+
+grind_pattern Nodup.count => count a l, Nodup l
+
+@[grind =]
+theorem nodup_iff_count [BEq α] [LawfulBEq α] {l : List α} : l.Nodup ↔ ∀ a, count a l ≤ 1 := by
+  induction l with
+  | nil => simp
+  | cons x l ih =>
+    constructor
+    · intro h a
+      simp at h
+      rw [count_cons]
+      split <;> rename_i h'
+      · simp at h'
+        rw [count_eq_zero.mpr ?_]
+        · exact Nat.le_refl _
+        · exact h' ▸ h.1
+      · simp at h'
+        refine ih.mp h.2 a
+    · intro h
+      simp only [count_cons] at h
+      simp only [nodup_cons]
+      constructor
+      · intro w
+        specialize h x
+        simp at h
+        have := count_pos_iff.mpr w
+        replace h := le_of_lt_succ h
+        apply Nat.lt_irrefl _ (Nat.lt_of_lt_of_le this h)
+      · rw [ih]
+        intro a
+        specialize h a
+        exact le_of_add_right_le h
+
 end List

src/Init/Data/List/Perm.lean

@@ -23,8 +23,7 @@ The notation `~` is used for permutation equivalence.
 -/
 
 set_option linter.listVariables true -- Enforce naming conventions for `List`/`Array`/`Vector` variables.
--- TODO: restore after an update-stage0
--- set_option linter.indexVariables true -- Enforce naming conventions for index variables.
+set_option linter.indexVariables true -- Enforce naming conventions for index variables.
 
 open Nat
 
@@ -90,6 +89,9 @@ theorem Perm.mem_iff {a : α} {l₁ l₂ : List α} (p : l₁ ~ l₂) : a ∈ l
   | swap => simp only [mem_cons, or_left_comm]
   | trans _ _ ih₁ ih₂ => simp only [ih₁, ih₂]
 
+grind_pattern Perm.mem_iff => l₁ ~ l₂, a ∈ l₁
+grind_pattern Perm.mem_iff => l₁ ~ l₂, a ∈ l₂
+
 theorem Perm.subset {l₁ l₂ : List α} (p : l₁ ~ l₂) : l₁ ⊆ l₂ := fun _ => p.mem_iff.mp
 
 theorem Perm.append_right {l₁ l₂ : List α} (t₁ : List α) (p : l₁ ~ l₂) : l₁ ++ t₁ ~ l₂ ++ t₁ := by
@@ -106,9 +108,15 @@ theorem Perm.append_left {t₁ t₂ : List α} : ∀ l : List α, t₁ ~ t₂
 theorem Perm.append {l₁ l₂ t₁ t₂ : List α} (p₁ : l₁ ~ l₂) (p₂ : t₁ ~ t₂) : l₁ ++ t₁ ~ l₂ ++ t₂ :=
   (p₁.append_right t₁).trans (p₂.append_left l₂)
 
+grind_pattern Perm.append => l₁ ~ l₂, t₁ ~ t₂, l₁ ++ t₁
+grind_pattern Perm.append => l₁ ~ l₂, t₁ ~ t₂, l₂ ++ t₂
+
 theorem Perm.append_cons (a : α) {l₁ l₂ r₁ r₂ : List α} (p₁ : l₁ ~ l₂) (p₂ : r₁ ~ r₂) :
     l₁ ++ a :: r₁ ~ l₂ ++ a :: r₂ := p₁.append (p₂.cons a)
 
+grind_pattern Perm.append_cons => l₁ ~ l₂, r₁ ~ r₂, l₁ ++ a :: r₁
+grind_pattern Perm.append_cons => l₁ ~ l₂, r₁ ~ r₂, l₂ ++ a :: r₂
+
 @[simp] theorem perm_middle {a : α} : ∀ {l₁ l₂ : List α}, l₁ ++ a :: l₂ ~ a :: (l₁ ++ l₂)
   | [], _ => .refl _
   | b :: _, _ => (Perm.cons _ perm_middle).trans (swap a b _)
@@ -194,9 +202,15 @@ theorem Perm.filterMap (f : α → Option β) {l₁ l₂ : List α} (p : l₁ ~
   | swap x y l₂ => cases hx : f x <;> cases hy : f y <;> simp [hx, hy, filterMap_cons, swap]
   | trans _p₁ _p₂ IH₁ IH₂ => exact IH₁.trans IH₂
 
+grind_pattern Perm.filterMap => l₁ ~ l₂, filterMap f l₁
+grind_pattern Perm.filterMap => l₁ ~ l₂, filterMap f l₂
+
 theorem Perm.map (f : α → β) {l₁ l₂ : List α} (p : l₁ ~ l₂) : map f l₁ ~ map f l₂ :=
   filterMap_eq_map ▸ p.filterMap _
 
+grind_pattern Perm.map => l₁ ~ l₂, map f l₁
+grind_pattern Perm.map => l₁ ~ l₂, map f l₂
+
 theorem Perm.pmap {p : α → Prop} (f : ∀ a, p a → β) {l₁ l₂ : List α} (p : l₁ ~ l₂) {H₁ H₂} :
     pmap f l₁ H₁ ~ pmap f l₂ H₂ := by
   induction p with
@@ -205,12 +219,18 @@ theorem Perm.pmap {p : α → Prop} (f : ∀ a, p a → β) {l₁ l₂ : List α
   | swap x y => simp [swap]
   | trans _p₁ p₂ IH₁ IH₂ => exact IH₁.trans (IH₂ (H₁ := fun a m => H₂ a (p₂.subset m)))
 
+grind_pattern Perm.pmap => l₁ ~ l₂, pmap f l₁ H₁
+grind_pattern Perm.pmap => l₁ ~ l₂, pmap f l₂ H₂
+
 theorem Perm.unattach {α : Type u} {p : α → Prop} {l₁ l₂ : List { x // p x }} (h : l₁ ~ l₂) :
     l₁.unattach.Perm l₂.unattach := h.map _
 
 theorem Perm.filter (p : α → Bool) {l₁ l₂ : List α} (s : l₁ ~ l₂) :
     filter p l₁ ~ filter p l₂ := by rw [← filterMap_eq_filter]; apply s.filterMap
 
+grind_pattern Perm.filter => l₁ ~ l₂, filter p l₁
+grind_pattern Perm.filter => l₁ ~ l₂, filter p l₂
+
 theorem filter_append_perm (p : α → Bool) (l : List α) :
     filter p l ++ filter (fun x => !p x) l ~ l := by
   induction l with
@@ -388,12 +408,16 @@ theorem Perm.erase (a : α) {l₁ l₂ : List α} (p : l₁ ~ l₂) : l₁.erase
     have h₂ : a ∉ l₂ := mt p.mem_iff.2 h₁
     rw [erase_of_not_mem h₁, erase_of_not_mem h₂]; exact p
 
+grind_pattern Perm.erase => l₁ ~ l₂, l₁.erase a
+grind_pattern Perm.erase => l₁ ~ l₂, l₂.erase a
+
 theorem cons_perm_iff_perm_erase {a : α} {l₁ l₂ : List α} :
     a :: l₁ ~ l₂ ↔ a ∈ l₂ ∧ l₁ ~ l₂.erase a := by
   refine ⟨fun h => ?_, fun ⟨m, h⟩ => (h.cons a).trans (perm_cons_erase m).symm⟩
   have : a ∈ l₂ := h.subset mem_cons_self
   exact ⟨this, (h.trans <| perm_cons_erase this).cons_inv⟩
 
+@[grind =]
 theorem perm_iff_count {l₁ l₂ : List α} : l₁ ~ l₂ ↔ ∀ a, count a l₁ = count a l₂ := by
   refine ⟨Perm.count_eq, fun H => ?_⟩
   induction l₁ generalizing l₂ with
@@ -410,6 +434,12 @@ theorem perm_iff_count {l₁ l₂ : List α} : l₁ ~ l₂ ↔ ∀ a, count a l
     rw [(perm_cons_erase this).count_eq] at H
     by_cases h : b = a <;> simpa [h, count_cons, Nat.succ_inj] using H
 
+theorem Perm.count (h : l₁ ~ l₂) (a : α) : count a l₁ = count a l₂ := by
+  rw [perm_iff_count.mp h]
+
+grind_pattern Perm.count => l₁ ~ l₂, count a l₁
+grind_pattern Perm.count => l₁ ~ l₂, count a l₂
+
 theorem isPerm_iff : ∀ {l₁ l₂ : List α}, l₁.isPerm l₂ ↔ l₁ ~ l₂
   | [], [] => by simp [isPerm, isEmpty]
   | [], _ :: _ => by simp [isPerm, isEmpty, Perm.nil_eq]
@@ -425,6 +455,9 @@ protected theorem Perm.insert (a : α) {l₁ l₂ : List α} (p : l₁ ~ l₂) :
     have := p.cons a
     simpa [h, mt p.mem_iff.2 h] using this
 
+grind_pattern Perm.insert => l₁ ~ l₂, l₁.insert a
+grind_pattern Perm.insert => l₁ ~ l₂, l₂.insert a
+
 theorem perm_insert_swap (x y : α) (l : List α) :
     List.insert x (List.insert y l) ~ List.insert y (List.insert x l) := by
   by_cases xl : x ∈ l <;> by_cases yl : y ∈ l <;> simp [xl, yl]
@@ -491,6 +524,9 @@ theorem Perm.nodup {l l' : List α} (hl : l ~ l') (hR : l.Nodup) : l'.Nodup := h
 theorem Perm.nodup_iff {l₁ l₂ : List α} : l₁ ~ l₂ → (Nodup l₁ ↔ Nodup l₂) :=
   Perm.pairwise_iff <| @Ne.symm α
 
+grind_pattern Perm.nodup_iff => l₁ ~ l₂, Nodup l₁
+grind_pattern Perm.nodup_iff => l₁ ~ l₂, Nodup l₂
+
 theorem Perm.flatten {l₁ l₂ : List (List α)} (h : l₁ ~ l₂) : l₁.flatten ~ l₂.flatten := by
   induction h with
   | nil => rfl
@@ -541,20 +577,30 @@ theorem perm_insertIdx {α} (x : α) (l : List α) {i} (h : i ≤ l.length) :
 
 namespace Perm
 
-theorem take {l₁ l₂ : List α} (h : l₁ ~ l₂) {n : Nat} (w : l₁.drop n ~ l₂.drop n) :
-    l₁.take n ~ l₂.take n := by
+theorem take {l₁ l₂ : List α} (h : l₁ ~ l₂) {i : Nat} (w : l₁.drop i ~ l₂.drop i) :
+    l₁.take i ~ l₂.take i := by
   classical
   rw [perm_iff_count] at h w ⊢
-  rw [← take_append_drop n l₁, ← take_append_drop n l₂] at h
+  rw [← take_append_drop i l₁, ← take_append_drop i l₂] at h
   simpa only [count_append, w, Nat.add_right_cancel_iff] using h
 
-theorem drop {l₁ l₂ : List α} (h : l₁ ~ l₂) {n : Nat} (w : l₁.take n ~ l₂.take n) :
-    l₁.drop n ~ l₂.drop n := by
+theorem drop {l₁ l₂ : List α} (h : l₁ ~ l₂) {i : Nat} (w : l₁.take i ~ l₂.take i) :
+    l₁.drop i ~ l₂.drop i := by
   classical
   rw [perm_iff_count] at h w ⊢
-  rw [← take_append_drop n l₁, ← take_append_drop n l₂] at h
+  rw [← take_append_drop i l₁, ← take_append_drop i l₂] at h
   simpa only [count_append, w, Nat.add_left_cancel_iff] using h
 
+theorem sum_nat {l₁ l₂ : List Nat} (h : l₁ ~ l₂) : l₁.sum = l₂.sum := by
+  induction h with
+  | nil => simp
+  | cons _ _ ih => simp [ih]
+  | swap => simpa [List.sum_cons] using Nat.add_left_comm ..
+  | trans _ _ ih₁ ih₂ => simp [ih₁, ih₂]
+
+grind_pattern Perm.sum_nat => l₁ ~ l₂, l₁.sum
+grind_pattern Perm.sum_nat => l₁ ~ l₂, l₂.sum
+
 end Perm
 
 end List

src/Init/Data/List/Range.lean

@@ -142,6 +142,8 @@ theorem range'_eq_cons_iff : range' s n = a :: xs ↔ s = a ∧ 0 < n ∧ xs = r
 
 /-! ### range -/
 
+@[simp, grind =] theorem range_one : range 1 = [0] := rfl
+
 theorem range_loop_range' : ∀ s n, range.loop s (range' s n) = range' 0 (n + s)
   | 0, _ => rfl
   | s + 1, n => by rw [← Nat.add_assoc, Nat.add_right_comm n s 1]; exact range_loop_range' s (n + 1)
@@ -223,7 +225,7 @@ theorem zipIdx_eq_nil_iff {l : List α} {i : Nat} : List.zipIdx l i = [] ↔ l =
   | [], _ => rfl
   | _ :: _, _ => congrArg Nat.succ length_zipIdx
 
-@[simp]
+@[simp, grind =]
 theorem getElem?_zipIdx :
     ∀ {l : List α} {i j}, (zipIdx l i)[j]? = l[j]?.map fun a => (a, i + j)
   | [], _, _ => rfl
@@ -232,7 +234,7 @@ theorem getElem?_zipIdx :
     simp only [zipIdx_cons, getElem?_cons_succ]
     exact getElem?_zipIdx.trans <| by rw [Nat.add_right_comm]; rfl
 
-@[simp]
+@[simp, grind =]
 theorem getElem_zipIdx {l : List α} (h : i < (l.zipIdx j).length) :
     (l.zipIdx j)[i] = (l[i]'(by simpa [length_zipIdx] using h), j + i) := by
   simp only [length_zipIdx] at h
@@ -240,7 +242,7 @@ theorem getElem_zipIdx {l : List α} (h : i < (l.zipIdx j).length) :
   simp only [getElem?_zipIdx, getElem?_eq_getElem h]
   simp
 
-@[simp]
+@[simp, grind =]
 theorem tail_zipIdx {l : List α} {i : Nat} : (zipIdx l i).tail = zipIdx l.tail (i + 1) := by
   induction l generalizing i with
   | nil => simp

src/Init/Data/List/Sort/Impl.lean

@@ -153,12 +153,12 @@ where
     mergeTR (run' r) (run l) le
 
 theorem splitRevInTwo'_fst (l : { l : List α // l.length = n }) :
-    (splitRevInTwo' l).1 = ⟨(splitInTwo ⟨l.1.reverse, by simpa using l.2⟩).2.1, by simp; omega⟩ := by
+    (splitRevInTwo' l).1 = ⟨(splitInTwo (n := n) ⟨l.1.reverse, by simpa using l.2⟩).2.1, by simp; omega⟩ := by
   simp only [splitRevInTwo', splitRevAt_eq, reverse_take, splitInTwo_snd]
   congr
   omega
 theorem splitRevInTwo'_snd (l : { l : List α // l.length = n }) :
-    (splitRevInTwo' l).2 = ⟨(splitInTwo ⟨l.1.reverse, by simpa using l.2⟩).1.1.reverse, by simp; omega⟩ := by
+    (splitRevInTwo' l).2 = ⟨(splitInTwo (n := n) ⟨l.1.reverse, by simpa using l.2⟩).1.1.reverse, by simp; omega⟩ := by
   simp only [splitRevInTwo', splitRevAt_eq, reverse_take, splitInTwo_fst, reverse_reverse]
   congr 2
   simp