fix: find macOS system libraries in leanc

.github/PULL_REQUEST_TEMPLATE.md

@@ -1,14 +1,13 @@
-# Read this section before submitting
+# Read and remove this section before submitting
 
 * Ensure your PR follows the [External Contribution Guidelines](https://github.com/leanprover/lean4/blob/master/CONTRIBUTING.md).
 * Please make sure the PR has excellent documentation and tests. If we label it `missing documentation` or `missing tests` then it needs fixing!
-* Include the link to your `RFC` or `bug` issue in the description.
+* Add the link to your `RFC` or `bug` issue below.
 * If the issue does not already have approval from a developer, submit the PR as draft.
-* The PR title/description will become the commit message. Keep it up-to-date as the PR evolves.
-* If you rebase your PR onto `nightly-with-mathlib` then CI will test Mathlib against your PR.
-* You can manage the `awaiting-review`, `awaiting-author`, and `WIP` labels yourself, by writing a comment containing one of these labels on its own line.
-* Remove this section, up to and including the `---` before submitting.
+* Remove this section before submitting.
 
----
+You can manage the `awaiting-review`, `awaiting-author`, and `WIP` labels yourself, by writing a comment containing one of these labels on its own line.
 
-Closes #0000 (`RFC` or `bug` issue number fixed by this PR, if any)
+# Summary
+
+Link to `RFC` or `bug` issue:

.github/workflows/actionlint.yml

@@ -1,22 +0,0 @@
-name: Actionlint
-on:
-  push:
-    branches:
-      - 'master'
-    paths:
-      - '.github/**'
-  pull_request:
-    paths:
-      - '.github/**'
-  merge_group:
-
-jobs:
-  actionlint:
-    runs-on: ubuntu-latest
-    steps:
-    - name: Checkout
-      uses: actions/checkout@v3
-    - name: actionlint
-      uses: raven-actions/actionlint@v1
-      with:
-        pyflakes: false # we do not use python scripts

.github/workflows/changelog.yml

@@ -0,0 +1,33 @@
+name: add PR to changelog
+
+on:
+  # needs read/write GH token, do *not* execute arbitrary code from PR
+  pull_request_target:
+    types: [closed]
+
+jobs:
+  update-changelog:
+    if: |
+      github.event.pull_request.merged == true &&
+      contains(github.event.pull_request.labels.*.name, 'changelog') &&
+      github.base_ref == 'master'
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v3
+        with:
+          # needs sufficiently elevated token to override branch protection rules
+          token: ${{ secrets.PUSH_NIGHTLY_TOKEN }}
+      - name: Update changelog
+        run: |
+          set -euxo pipefail
+          escaped_link=$(sed -e 's/[\/&]/\\&/g' <<'EOF'
+          [${{ github.event.pull_request.title}}](${{ github.event.pull_request.html_url }})
+          EOF
+          )
+          # insert link below first dashes line (https://stackoverflow.com/a/9453461/161659)
+          sed -i "0,/^---*/s/^---*/\0\n\n* $escaped_link./" RELEASES.md
+          # commit as github-actions bot (https://github.com/orgs/community/discussions/26560#discussioncomment-3252339)
+          git config user.email "41898282+github-actions[bot]@users.noreply.github.com"
+          git config user.name "github-actions[bot]"
+          git commit -i RELEASES.md -m "doc: update changelog"
+          git push

.github/workflows/ci.yml

@@ -6,7 +6,6 @@ on:
     tags:
       - '*'
   pull_request:
-    types: [opened, synchronize, reopened, labeled]
   merge_group:
   schedule:
     - cron: '0 7 * * *'  # 8AM CET/11PM PT
@@ -46,11 +45,11 @@ jobs:
             github.event_name == 'pull_request' && !contains( github.event.pull_request.labels.*.name, 'full-ci')
            }}
         run: |
-          echo "quick=${{env.quick}}" >> "$GITHUB_OUTPUT"
+          echo "quick=${{env.quick}}" >> $GITHUB_OUTPUT
 
       - name: Configure build matrix
         id: set-matrix
-        uses: actions/github-script@v7
+        uses: actions/github-script@v3
         with:
           script: |
             const quick = ${{ steps.set-quick.outputs.quick }};
@@ -124,11 +123,10 @@ jobs:
                 "release": true,
                 "quick": false,
                 "cross": true,
-                "cross_target": "aarch64-apple-darwin",
                 "shell": "bash -euxo pipefail {0}",
                 "CMAKE_OPTIONS": "-DUSE_GMP=OFF -DLEAN_INSTALL_SUFFIX=-darwin_aarch64",
                 "llvm-url": "https://github.com/leanprover/lean-llvm/releases/download/15.0.1/lean-llvm-aarch64-apple-darwin.tar.zst https://github.com/leanprover/lean-llvm/releases/download/15.0.1/lean-llvm-x86_64-apple-darwin.tar.zst",
-                "prepare-llvm": "../script/prepare-llvm-macos.sh lean-llvm-aarch64-* lean-llvm-x86_64-*",
+                "prepare-llvm": "EXTRA_FLAGS=--target=aarch64-apple-darwin ../script/prepare-llvm-macos.sh lean-llvm-aarch64-* lean-llvm-x86_64-*",
                 "binary-check": "otool -L",
                 "tar": "gtar" // https://github.com/actions/runner-images/issues/2619
               },
@@ -152,10 +150,9 @@ jobs:
                 "release": true,
                 "quick": false,
                 "cross": true,
-                "cross_target": "aarch64-unknown-linux-gnu",
                 "shell": "nix-shell --arg pkgsDist \"import (fetchTarball \\\"channel:nixos-19.03\\\") {{ localSystem.config = \\\"aarch64-unknown-linux-gnu\\\"; }}\" --run \"bash -euxo pipefail {0}\"",
                 "llvm-url": "https://github.com/leanprover/lean-llvm/releases/download/15.0.1/lean-llvm-x86_64-linux-gnu.tar.zst https://github.com/leanprover/lean-llvm/releases/download/15.0.1/lean-llvm-aarch64-linux-gnu.tar.zst",
-                "prepare-llvm": "../script/prepare-llvm-linux.sh lean-llvm-aarch64-* lean-llvm-x86_64-*"
+                "prepare-llvm": "EXTRA_FLAGS=--target=aarch64-unknown-linux-gnu ../script/prepare-llvm-linux.sh lean-llvm-aarch64-* lean-llvm-x86_64-*"
               },
               {
                 "name": "Linux 32bit",
@@ -203,8 +200,8 @@ jobs:
             git fetch nightly --tags
             LEAN_VERSION_STRING="nightly-$(date -u +%F)"
             # do nothing if commit already has a different tag
-            if [[ "$(git name-rev --name-only --tags --no-undefined HEAD 2> /dev/null || echo "$LEAN_VERSION_STRING")" == "$LEAN_VERSION_STRING" ]]; then
-              echo "nightly=$LEAN_VERSION_STRING" >> "$GITHUB_OUTPUT"
+            if [[ $(git name-rev --name-only --tags --no-undefined HEAD 2> /dev/null || echo $LEAN_VERSION_STRING) == $LEAN_VERSION_STRING ]]; then
+              echo "nightly=$LEAN_VERSION_STRING" >> $GITHUB_OUTPUT
             fi
           fi
 
@@ -212,7 +209,7 @@ jobs:
         if: startsWith(github.ref, 'refs/tags/') && github.repository == 'leanprover/lean4'
         id: set-release
         run: |
-          TAG_NAME="${GITHUB_REF##*/}"
+          TAG_NAME=${GITHUB_REF##*/}
 
           # From https://github.com/fsaintjacques/semver-tool/blob/master/src/semver
 
@@ -229,13 +226,11 @@ jobs:
 
           if [[ ${TAG_NAME} =~ ${SEMVER_REGEX} ]]; then
             echo "Tag ${TAG_NAME} matches SemVer regex, with groups ${BASH_REMATCH[1]} ${BASH_REMATCH[2]} ${BASH_REMATCH[3]} ${BASH_REMATCH[4]}"
-            {
-              echo "LEAN_VERSION_MAJOR=${BASH_REMATCH[1]}"
-              echo "LEAN_VERSION_MINOR=${BASH_REMATCH[2]}"
-              echo "LEAN_VERSION_PATCH=${BASH_REMATCH[3]}"
-              echo "LEAN_SPECIAL_VERSION_DESC=${BASH_REMATCH[4]##-}"
-              echo "RELEASE_TAG=$TAG_NAME"
-            } >> "$GITHUB_OUTPUT"
+            echo "LEAN_VERSION_MAJOR=${BASH_REMATCH[1]}" >> $GITHUB_OUTPUT
+            echo "LEAN_VERSION_MINOR=${BASH_REMATCH[2]}" >> $GITHUB_OUTPUT
+            echo "LEAN_VERSION_PATCH=${BASH_REMATCH[3]}" >> $GITHUB_OUTPUT
+            echo "LEAN_SPECIAL_VERSION_DESC=${BASH_REMATCH[4]##-}" >> $GITHUB_OUTPUT
+            echo "RELEASE_TAG=$TAG_NAME" >> $GITHUB_OUTPUT
           else
             echo "Tag ${TAG_NAME} did not match SemVer regex."
           fi
@@ -323,15 +318,8 @@ jobs:
           mkdir build
           cd build
           ulimit -c unlimited # coredumps
-          # arguments passed to `cmake`
           # this also enables githash embedding into stage 1 library
           OPTIONS=(-DCHECK_OLEAN_VERSION=ON)
-          OPTIONS+=(-DLEAN_EXTRA_MAKE_OPTS=-DwarningAsError=true)
-          if [[ -n '${{ matrix.cross_target }}' ]]; then
-            # used by `prepare-llvm`
-            export EXTRA_FLAGS=--target=${{ matrix.cross_target }}
-            OPTIONS+=(-DLEAN_PLATFORM_TARGET=${{ matrix.cross_target }})
-          fi
           if [[ -n '${{ matrix.prepare-llvm }}' ]]; then
             wget -q ${{ matrix.llvm-url }}
             PREPARE="$(${{ matrix.prepare-llvm }})"
@@ -383,10 +371,10 @@ jobs:
           ulimit -c unlimited # coredumps
           # exclude nonreproducible test
           ctest -j4 --output-on-failure ${{ matrix.CTEST_OPTIONS }} < /dev/null
-        if: (matrix.wasm || !matrix.cross) && needs.configure.outputs.quick == 'false'
+        if: matrix.wasm || !matrix.cross
       - name: Check Test Binary
         run: ${{ matrix.binary-check }} tests/compiler/534.lean.out
-        if: ${{ !matrix.cross && needs.configure.outputs.quick == 'false' }}
+        if: ${{ !matrix.cross }}
       - name: Build Stage 2
         run: |
           cd build
@@ -411,11 +399,11 @@ jobs:
           cd build
           ulimit -c unlimited # coredumps
           make update-stage0 && make -j4
-        if: matrix.name == 'Linux' && needs.configure.outputs.quick == 'false'
+        if: matrix.name == 'Linux' && !needs.configure.outputs.quick
       - name: CCache stats
         run: ccache -s
       - name: Show stacktrace for coredumps
-        if: ${{ failure() && matrix.os == 'ubuntu-latest' }}
+        if: ${{ failure() }} && matrix.os == 'ubuntu-latest'
         run: |
           for c in coredumps/*; do
             progbin="$(file $c | sed "s/.*execfn: '\([^']*\)'.*/\1/")"
@@ -423,7 +411,7 @@ jobs:
           done
       - name: Upload coredumps
         uses: actions/upload-artifact@v3
-        if: ${{ failure() && matrix.os == 'ubuntu-latest' }}
+        if: ${{ failure() }} && matrix.os == 'ubuntu-latest'
         with:
           name: coredumps-${{ matrix.name }}
           path: |
@@ -445,7 +433,7 @@ jobs:
     if: ${{ always() }}
     steps:
     - if: contains(needs.*.result, 'failure') ||  contains(needs.*.result, 'cancelled')
-      uses: actions/github-script@v7
+      uses: actions/github-script@v3
       with:
         script: |
             core.setFailed('Some jobs failed')
@@ -490,16 +478,16 @@ jobs:
         run: |
           git remote add nightly https://foo:'${{ secrets.PUSH_NIGHTLY_TOKEN }}'@github.com/${{ github.repository_owner }}/lean4-nightly.git
           git fetch nightly --tags
-          git tag "${{ needs.configure.outputs.nightly }}"
-          git push nightly "${{ needs.configure.outputs.nightly }}"
+          git tag ${{ needs.configure.outputs.nightly }}
+          git push nightly ${{ needs.configure.outputs.nightly }}
           git push -f origin refs/tags/${{ needs.configure.outputs.nightly }}:refs/heads/nightly
-          last_tag="$(git log HEAD^ --simplify-by-decoration --pretty="format:%d" | grep -o "nightly-[-0-9]*" | head -n 1)"
+          last_tag=$(git log HEAD^ --simplify-by-decoration --pretty="format:%d" | grep -o "nightly-[-0-9]*" | head -n 1)
           echo -e "*Changes since ${last_tag}:*\n\n" > diff.md
-          git show "$last_tag":RELEASES.md > old.md
+          git show $last_tag:RELEASES.md > old.md
           #./script/diff_changelogs.py old.md doc/changes.md >> diff.md
           diff --changed-group-format='%>' --unchanged-group-format='' old.md RELEASES.md >> diff.md || true
           echo -e "\n*Full commit log*\n" >> diff.md
-          git log --oneline "$last_tag"..HEAD | sed 's/^/* /' >> diff.md
+          git log --oneline $last_tag..HEAD | sed 's/^/* /' >> diff.md
       - name: Release Nightly
         uses: softprops/action-gh-release@v1
         with:

.github/workflows/labels-from-comments.yml

@@ -15,7 +15,7 @@ jobs:
 
     steps:
     - name: Add label based on comment
-      uses: actions/github-script@v7
+      uses: actions/github-script@v6
       with:
         github-token: ${{ secrets.GITHUB_TOKEN }}
         script: |

.github/workflows/nix-ci.yml

@@ -17,7 +17,7 @@ jobs:
     runs-on: ${{ matrix.os }}
     defaults:
       run:
-        shell: nix run .#ciShell -- bash -euxo pipefail {0}
+        shell: nix -v --experimental-features "nix-command flakes" run .#ciShell -- bash -euxo pipefail {0}
     strategy:
       matrix:
         include:
@@ -29,13 +29,21 @@ jobs:
       fail-fast: false
     name: ${{ matrix.name }}
     env:
-      NIX_BUILD_ARGS: --print-build-logs --fallback
+      NIX_BUILD_ARGS: -v --print-build-logs --fallback
     steps:
       - name: Checkout
         uses: actions/checkout@v3
         with:
           # the default is to use a virtual merge commit between the PR and master: just use the PR
           ref: ${{ github.event.pull_request.head.sha }}
+      - name: Install Nix
+        uses: cachix/install-nix-action@v18
+        with:
+          # https://github.com/NixOS/nix/issues/6572
+          install_url: https://releases.nixos.org/nix/nix-2.7.0/install
+          extra_nix_config: |
+            extra-sandbox-paths = /nix/var/cache/ccache
+            substituters = file://${{ github.workspace }}/nix-store-cache-copy?priority=10&trusted=true https://cache.nixos.org
       - name: Set Up Nix Cache
         uses: actions/cache@v3
         with:
@@ -49,13 +57,8 @@ jobs:
         run: |
           # Nix seems to mutate the cache, so make a copy
           cp -r nix-store-cache nix-store-cache-copy || true
-      - name: Install Nix
-        uses: DeterminateSystems/nix-installer-action@main
-        with:
-          extra-conf: |
-            extra-sandbox-paths = /nix/var/cache/ccache?
-            substituters = file://${{ github.workspace }}/nix-store-cache-copy?priority=10&trusted=true https://cache.nixos.org  
       - name: Prepare CCache Cache
+        shell: bash -euxo pipefail {0}
         run: |
           sudo mkdir -m0770 -p /nix/var/cache/ccache
           sudo chown -R $USER /nix/var/cache/ccache
@@ -68,6 +71,7 @@ jobs:
           restore-keys: |
             ${{ matrix.name }}-nix-ccache
       - name: Further Set Up CCache Cache
+        shell: bash -euxo pipefail {0}
         run: |
           sudo chown -R root:nixbld /nix/var/cache
           sudo chmod -R 770 /nix/var/cache
@@ -87,17 +91,7 @@ jobs:
         run: |
           nix build $NIX_BUILD_ARGS --update-input lean --no-write-lock-file ./doc#{lean-mdbook,leanInk,alectryon,test,inked} -o push-doc
           nix build $NIX_BUILD_ARGS --update-input lean --no-write-lock-file ./doc
-          # https://github.com/netlify/cli/issues/1809
-          cp -r --dereference ./result ./dist
         if: matrix.name == 'Nix Linux'
-      - name: Check manual for broken links
-        id: lychee
-        uses: lycheeverse/lychee-action@v1.9.0
-        with:
-          fail: false  # report errors but do not block CI on temporary failures
-          # gmplib.org consistently times out from GH actions
-          # the GitHub token is to avoid rate limiting
-          args: --base './dist' --no-progress --github-token ${{ secrets.GITHUB_TOKEN }} --exclude 'gmplib.org' './dist/**/*.html'
       - name: Push to Cachix
         run: |
           [ -z "${{ secrets.CACHIX_AUTH_TOKEN }}" ] || cachix push -j4 lean4 ./push-* || true
@@ -105,29 +99,13 @@ jobs:
         run: |
           rm -rf nix-store-cache || true
           nix copy ./push-* --to file://$PWD/nix-store-cache?compression=none
-      - id: deploy-info
-        name: Compute Deployment Metadata
-        run: |
-          set -e
-          python3 -c 'import base64; print("alias="+base64.urlsafe_b64encode(bytes.fromhex("${{github.sha}}")).decode("utf-8").rstrip("="))' >> "$GITHUB_OUTPUT"
-          echo "message=`git log -1 --pretty=format:"%s"`" >> "$GITHUB_OUTPUT"
-      - name: Publish manual to Netlify
-        uses: nwtgck/actions-netlify@v2.0
-        id: publish-manual
+      - name: Publish manual
+        uses: peaceiris/actions-gh-pages@v3
         with:
-          publish-dir: ./dist
-          production-branch: master
-          github-token: ${{ secrets.GITHUB_TOKEN }}
-          deploy-message: |
-            ${{ github.event_name == 'pull_request' && format('pr#{0}: {1}', github.event.number, github.event.pull_request.title) || format('ref/{0}: {1}', github.ref_name, steps.deploy-info.outputs.message) }}
-          alias: ${{ steps.deploy-info.outputs.alias }}
-          enable-commit-comment: false
-          enable-pull-request-comment: false
-          github-deployment-environment: "lean-lang.org/lean4/doc"
-          fails-without-credentials: false
-        env:
-          NETLIFY_AUTH_TOKEN: ${{ secrets.NETLIFY_AUTH_TOKEN }}
-          NETLIFY_SITE_ID: "b8e805d2-7e9b-4f80-91fb-a84d72fc4a68"
+          github_token: ${{ secrets.GITHUB_TOKEN }}
+          publish_dir: ./result
+          destination_dir: ./doc
+        if: matrix.name == 'Nix Linux' && github.ref == 'refs/heads/master' && github.event_name == 'push'
       - name: Fixup CCache Cache
         run: |
           sudo chown -R $USER /nix/var/cache

.github/workflows/pr-release.yml

@@ -6,10 +6,6 @@
 # Instead we use `workflow_run`, which essentially allows us to escalate privileges
 # (but only runs the CI as described in the `master` branch, not in the PR branch).
 
-# The main specification/documentation for this workflow is at
-# https://leanprover-community.github.io/contribute/tags_and_branches.html
-# Keep that in sync!
-
 name: PR release
 
 on:
@@ -20,16 +16,27 @@ on:
 jobs:
   on-success:
     runs-on: ubuntu-latest
-    if: github.event.workflow_run.conclusion == 'success' && github.event.workflow_run.event == 'pull_request' && github.repository == 'leanprover/lean4'
+    if: github.event.workflow_run.conclusion == 'success' && github.repository == 'leanprover/lean4'
     steps:
       - name: Retrieve information about the original workflow
         uses: potiuk/get-workflow-origin@v1_1 # https://github.com/marketplace/actions/get-workflow-origin
-        # This action is deprecated and archived, but it seems hard to find a better solution for getting the PR number
-        # see https://github.com/orgs/community/discussions/25220 for some discussion
         id: workflow-info
         with:
           token: ${{ secrets.GITHUB_TOKEN }}
           sourceRunId: ${{ github.event.workflow_run.id }}
+      - name: Checkout
+        # Only proceed if the previous workflow had a pull request number.
+        if: ${{ steps.workflow-info.outputs.pullRequestNumber != '' }}
+        uses: actions/checkout@v3
+        with:
+          token: ${{ secrets.PR_RELEASES_TOKEN }}
+          # Since `workflow_run` runs on master, we need to specify which commit to check out,
+          # so that we tag the PR.
+          # It's important that we use `sourceHeadSha` here, not `targetCommitSha`
+          # as we *don't* want the synthetic merge with master.
+          ref: ${{ steps.workflow-info.outputs.sourceHeadSha }}
+          # We need a full checkout, so that we can push the PR commits to the `lean4-pr-releases` repo.
+          fetch-depth: 0
 
       - name: Download artifact from the previous workflow.
         if: ${{ steps.workflow-info.outputs.pullRequestNumber != '' }}
@@ -40,22 +47,14 @@ jobs:
           path: artifacts
           name: build-.*
           name_is_regexp: true
-
-      - name: Push tag
-        if: ${{ steps.workflow-info.outputs.pullRequestNumber != '' }}
-        run: |
-          git init --bare lean4.git
-          git -C lean4.git remote add origin https://github.com/${{ github.repository_owner }}/lean4.git
-          git -C lean4.git fetch -n origin master
-          git -C lean4.git fetch -n origin "${{ steps.workflow-info.outputs.sourceHeadSha }}"
-          git -C lean4.git tag -f pr-release-${{ steps.workflow-info.outputs.pullRequestNumber }} "${{ steps.workflow-info.outputs.sourceHeadSha }}"
-          git -C lean4.git remote add pr-releases https://foo:'${{ 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 }}
-      - name: Delete existing release if present
+      - name: Prepare release
         if: ${{ steps.workflow-info.outputs.pullRequestNumber != '' }}
         run: |
+          git remote add pr-releases https://foo:'${{ secrets.PR_RELEASES_TOKEN }}'@github.com/${{ github.repository_owner }}/lean4-pr-releases.git
           # Try to delete any existing release for the current PR.
           gh release delete --repo ${{ github.repository_owner }}/lean4-pr-releases pr-release-${{ steps.workflow-info.outputs.pullRequestNumber }} -y || true
+          git tag -f pr-release-${{ steps.workflow-info.outputs.pullRequestNumber }}
+          git push -f pr-releases pr-release-${{ steps.workflow-info.outputs.pullRequestNumber }}
         env:
           GH_TOKEN: ${{ secrets.PR_RELEASES_TOKEN }}
       - name: Release
@@ -73,41 +72,19 @@ jobs:
           # The token used here must have `workflow` privileges.
           GITHUB_TOKEN: ${{ secrets.PR_RELEASES_TOKEN }}
 
-      - name: Report release status
-        if: ${{ steps.workflow-info.outputs.pullRequestNumber != '' }}
-        uses: actions/github-script@v6
-        with:
-          script: |
-            await github.rest.repos.createCommitStatus({
-              owner: context.repo.owner,
-              repo: context.repo.repo,
-              sha: "${{ steps.workflow-info.outputs.sourceHeadSha }}",
-              state: "success",
-              context: "PR toolchain",
-              description: "${{ github.repository_owner }}/lean4-pr-releases:pr-release-${{ steps.workflow-info.outputs.pullRequestNumber }}",
-            });
-
       - name: Add label
         if: ${{ steps.workflow-info.outputs.pullRequestNumber != '' }}
-        uses: actions/github-script@v7
+        uses: actions-ecosystem/action-add-labels@v1
         with:
-          script: |
-            await github.rest.issues.addLabels({
-              issue_number: ${{ steps.workflow-info.outputs.pullRequestNumber }},
-              owner: context.repo.owner,
-              repo: context.repo.repo,
-              labels: ['toolchain-available']
-            })
+          number: ${{ steps.workflow-info.outputs.pullRequestNumber }}
+          labels: toolchain-available
 
       # Next, determine the most recent nightly release in this PR's history.
-      - name: Find most recent nightly in feature branch
+      - name: Find most recent nightly
         id: most-recent-nightly-tag
         if: ${{ steps.workflow-info.outputs.pullRequestNumber != '' }}
         run: |
-          git -C lean4.git remote add nightly https://github.com/leanprover/lean4-nightly.git
-          git -C lean4.git fetch nightly '+refs/tags/nightly-*:refs/tags/nightly-*'
-          git -C lean4.git tag --merged "${{ steps.workflow-info.outputs.sourceHeadSha }}" --list "nightly-*" \
-            | sort -rV | head -n 1 | sed "s/^nightly-*/MOST_RECENT_NIGHTLY=/" | tee -a "$GITHUB_ENV"
+          echo "MOST_RECENT_NIGHTLY=$(script/most-recent-nightly-tag.sh)" >> $GITHUB_ENV
 
       - name: 'Setup jq'
         if: ${{ steps.workflow-info.outputs.pullRequestNumber != '' }}
@@ -118,57 +95,43 @@ jobs:
         if: ${{ steps.workflow-info.outputs.pullRequestNumber != '' }}
         id: ready
         run: |
-          echo "Most recent nightly release in your branch: $MOST_RECENT_NIGHTLY"
-          NIGHTLY_SHA=$(git -C lean4.git rev-parse "nightly-$MOST_RECENT_NIGHTLY^{commit}")
-          echo "SHA of most recent nightly release: $NIGHTLY_SHA"
-          MERGE_BASE_SHA=$(git -C lean4.git merge-base origin/master "${{ steps.workflow-info.outputs.sourceHeadSha }}")
+          echo "Most recent nightly: $MOST_RECENT_NIGHTLY"
+          NIGHTLY_SHA=$(git rev-parse nightly-$MOST_RECENT_NIGHTLY^{commit})
+          echo "SHA of most recent nightly: $NIGHTLY_SHA"
+          MERGE_BASE_SHA=$(git merge-base origin/master HEAD)
           echo "SHA of merge-base: $MERGE_BASE_SHA"
           if [ "$NIGHTLY_SHA" = "$MERGE_BASE_SHA" ]; then
-            echo "The merge base of this PR coincides with the nightly release"
+            echo "Most recent nightly tag agrees with the merge base."
 
-            MATHLIB_REMOTE_TAGS="$(git ls-remote https://github.com/leanprover-community/mathlib4.git nightly-testing-"$MOST_RECENT_NIGHTLY")"
+            REMOTE_BRANCHES=$(git ls-remote -h https://github.com/leanprover-community/mathlib4.git nightly-testing-$MOST_RECENT_NIGHTLY)
 
-            if [[ -n "$MATHLIB_REMOTE_TAGS" ]]; then
-              echo "... and Mathlib has a 'nightly-testing-$MOST_RECENT_NIGHTLY' tag."
+            if [[ -n "$REMOTE_BRANCHES" ]]; then
+              echo "... and Mathlib has a 'nightly-testing-$MOST_RECENT_NIGHTLY' branch."
               MESSAGE=""
             else
-              echo "... but Mathlib does not yet have a 'nightly-testing-$MOST_RECENT_NIGHTLY' tag."
-              MESSAGE="- ❗ Mathlib CI can not be attempted yet, as the \`nightly-testing-$MOST_RECENT_NIGHTLY\` tag does not exist there yet. We will retry when you push more commits. If you rebase your branch onto \`nightly-with-mathlib\`, Mathlib CI should run now."
-            fi
-
-            STD_REMOTE_TAGS="$(git ls-remote https://github.com/leanprover/std4.git nightly-testing-"$MOST_RECENT_NIGHTLY")"
-
-            if [[ -n "$STD_REMOTE_TAGS" ]]; then
-              echo "... and Std has a 'nightly-testing-$MOST_RECENT_NIGHTLY' tag."
-              MESSAGE=""
-            else
-              echo "... but Std does not yet have a 'nightly-testing-$MOST_RECENT_NIGHTLY' tag."
-              MESSAGE="- ❗ Std CI can not be attempted yet, as the \`nightly-testing-$MOST_RECENT_NIGHTLY\` tag does not exist there yet. We will retry when you push more commits. If you rebase your branch onto \`nightly-with-mathlib\`, Std CI should run now."
+              echo "... but Mathlib does not yet have a 'nightly-testing-$MOST_RECENT_NIGHTLY' branch."
+              MESSAGE="- ❗ Mathlib CI can not be attempted yet, as the 'nightly-testing-$MOST_RECENT_NIGHTLY' branch does not exist there yet. We will retry when you push more commits. It may be necessary to rebase onto 'nightly' tomorrow."
             fi
 
           else
             echo "The most recently nightly tag on this branch has SHA: $NIGHTLY_SHA"
             echo "but 'git merge-base origin/master HEAD' reported: $MERGE_BASE_SHA"
-            git -C lean4.git log -10 origin/master
+            git log -10
 
-            MESSAGE="- ❗ Std/Mathlib CI will not be attempted unless your PR branches off the \`nightly-with-mathlib\` branch."
+            MESSAGE="- ❗ Mathlib CI will not be attempted unless you rebase your PR onto the 'nightly' branch."
           fi
 
           if [[ -n "$MESSAGE" ]]; then
 
             echo "Checking existing messages"
 
-            # The code for updating comments is duplicated in mathlib's
-            # scripts/lean-pr-testing-comments.sh
-            # so keep in sync
-
             # Use GitHub API to check if a comment already exists
-            existing_comment="$(curl -L -s -H "Authorization: token ${{ secrets.MATHLIB4_BOT }}" \
+            existing_comment=$(curl -L -s -H "Authorization: token ${{ secrets.MATHLIB4_BOT }}" \
                                     -H "Accept: application/vnd.github.v3+json" \
                                     "https://api.github.com/repos/leanprover/lean4/issues/${{ steps.workflow-info.outputs.pullRequestNumber }}/comments" \
-                                    | jq 'first(.[] | select(.body | test("^- . Mathlib") or startswith("Mathlib CI status")) | select(.user.login == "leanprover-community-mathlib4-bot"))')"
-            existing_comment_id="$(echo "$existing_comment" | jq -r .id)"
-            existing_comment_body="$(echo "$existing_comment" | jq -r .body)"
+                                    | jq '.[] | select(.body | startswith("- ❗ Mathlib") or startswith("- ✅ Mathlib") or startswith("- ❌ Mathlib") or startswith("- 💥 Mathlib") or startswith("- 🟡 Mathlib"))')
+            existing_comment_id=$(echo "$existing_comment" | jq -r .id)
+            existing_comment_body=$(echo "$existing_comment" | jq -r .body)
 
             if [[ "$existing_comment_body" != *"$MESSAGE"* ]]; then
               MESSAGE="$MESSAGE ($(date "+%Y-%m-%d %H:%M:%S"))"
@@ -178,14 +141,13 @@ jobs:
               # Append new result to the existing comment or post a new comment
               # It's essential we use the MATHLIB4_BOT token here, so that Mathlib CI can subsequently edit the comment.
               if [ -z "$existing_comment_id" ]; then
-                INTRO="Mathlib CI status ([docs](https://leanprover-community.github.io/contribute/tags_and_branches.html)):"
                 # Post new comment with a bullet point
                 echo "Posting as new comment at leanprover/lean4/issues/${{ steps.workflow-info.outputs.pullRequestNumber }}/comments"
                 curl -L -s \
                   -X POST \
                   -H "Authorization: token ${{ secrets.MATHLIB4_BOT }}" \
                   -H "Accept: application/vnd.github.v3+json" \
-                  -d "$(jq --null-input --arg intro "$INTRO" --arg val "$MESSAGE" '{"body":($intro + "\n" + $val)}')" \
+                  -d "$(jq --null-input --arg val "$MESSAGE" '{"body": $val}')" \
                   "https://api.github.com/repos/leanprover/lean4/issues/${{ steps.workflow-info.outputs.pullRequestNumber }}/comments"
               else
                 # Append new result to the existing comment
@@ -200,93 +162,18 @@ jobs:
             else
               echo "The message already exists in the comment body."
             fi
-            echo "mathlib_ready=false" >> "$GITHUB_OUTPUT"
+            echo "::set-output name=mathlib_ready::false"
           else
-            echo "mathlib_ready=true" >> "$GITHUB_OUTPUT"
+            echo "::set-output name=mathlib_ready::true"
           fi
 
-      - name: Report mathlib base
-        if: ${{ steps.workflow-info.outputs.pullRequestNumber != '' && steps.ready.outputs.mathlib_ready == 'true' }}
-        uses: actions/github-script@v6
-        with:
-          script: |
-            const description =
-              process.env.MOST_RECENT_NIGHTLY ?
-              "nightly-" + process.env.MOST_RECENT_NIGHTLY :
-              "not branched off nightly";
-            await github.rest.repos.createCommitStatus({
-              owner: context.repo.owner,
-              repo: context.repo.repo,
-              sha: "${{ steps.workflow-info.outputs.sourceHeadSha }}",
-              state: "success",
-              context: "PR branched off:",
-              description: description,
-            });
-
-      # We next automatically create a Std branch using this toolchain.
-      # Std doesn't itself have a mechanism to report results of CI from this branch back to Lean
-      # Instead this is taken care of by Mathlib CI, which will fail if Std fails.
-      - name: Cleanup workspace
-        if: steps.workflow-info.outputs.pullRequestNumber != '' && steps.ready.outputs.mathlib_ready == 'true'
-        run: |
-          sudo rm -rf ./*
-
-      # Checkout the Std repository with all branches
-      - name: Checkout Std repository
-        if: steps.workflow-info.outputs.pullRequestNumber != '' && steps.ready.outputs.mathlib_ready == 'true'
-        uses: actions/checkout@v3
-        with:
-          repository: leanprover/std4
-          token: ${{ secrets.MATHLIB4_BOT }}
-          ref: nightly-testing
-          fetch-depth: 0 # This ensures we check out all tags and branches.
-
-      - name: Check if tag exists
-        if: steps.workflow-info.outputs.pullRequestNumber != '' && steps.ready.outputs.mathlib_ready == 'true'
-        id: check_std_tag
-        run: |
-          git config user.name "leanprover-community-mathlib4-bot"
-          git config user.email "leanprover-community-mathlib4-bot@users.noreply.github.com"
-
-          if git ls-remote --heads --tags --exit-code origin "nightly-testing-${MOST_RECENT_NIGHTLY}" >/dev/null; then
-            BASE="nightly-testing-${MOST_RECENT_NIGHTLY}"
-          else
-            echo "This shouldn't be possible: couldn't find a 'nightly-testing-${MOST_RECENT_NIGHTLY}' tag at Std. Falling back to 'nightly-testing'."
-            BASE=nightly-testing
-          fi
-
-          echo "Using base branch: $BASE"
-
-          EXISTS="$(git ls-remote --heads origin lean-pr-testing-${{ steps.workflow-info.outputs.pullRequestNumber }} | wc -l)"
-          echo "Branch exists: $EXISTS"
-          if [ "$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-${{ steps.workflow-info.outputs.pullRequestNumber }}" > lean-toolchain
-            git add lean-toolchain
-            git commit -m "Update lean-toolchain for testing https://github.com/leanprover/lean4/pull/${{ steps.workflow-info.outputs.pullRequestNumber }}"
-          else
-            echo "Branch already exists, pushing an empty commit."
-            git switch lean-pr-testing-${{ steps.workflow-info.outputs.pullRequestNumber }}
-            # The Std `nightly-testing` or `nightly-testing-YYYY-MM-DD` branch may have moved since this branch was created, so merge their changes.
-            # (This should no longer be possible once `nightly-testing-YYYY-MM-DD` is a tag, but it is still safe to merge.)
-            git merge "$BASE" --strategy-option ours --no-commit --allow-unrelated-histories
-            git commit --allow-empty -m "Trigger CI for https://github.com/leanprover/lean4/pull/${{ steps.workflow-info.outputs.pullRequestNumber }}"
-          fi
-
-      - name: Push changes
-        if: steps.workflow-info.outputs.pullRequestNumber != '' && steps.ready.outputs.mathlib_ready == 'true'
-        run: |
-          git push origin lean-pr-testing-${{ steps.workflow-info.outputs.pullRequestNumber }}
-
-
       # We next automatically create a Mathlib branch using this toolchain.
       # Mathlib CI will be responsible for reporting back success or failure
       # to the PR comments asynchronously.
       - name: Cleanup workspace
         if: steps.workflow-info.outputs.pullRequestNumber != '' && steps.ready.outputs.mathlib_ready == 'true'
         run: |
-          sudo rm -rf ./*
+          sudo rm -rf *
 
       # Checkout the mathlib4 repository with all branches
       - name: Checkout mathlib4 repository
@@ -298,38 +185,37 @@ jobs:
           ref: nightly-testing
           fetch-depth: 0 # This ensures we check out all tags and branches.
 
-      - name: Check if tag exists
+      - name: Check if branch exists
         if: steps.workflow-info.outputs.pullRequestNumber != '' && steps.ready.outputs.mathlib_ready == 'true'
-        id: check_mathlib_tag
+        id: check_branch
         run: |
           git config user.name "leanprover-community-mathlib4-bot"
           git config user.email "leanprover-community-mathlib4-bot@users.noreply.github.com"
 
-          if git ls-remote --heads --tags --exit-code origin "nightly-testing-${MOST_RECENT_NIGHTLY}" >/dev/null; then
-            BASE="nightly-testing-${MOST_RECENT_NIGHTLY}"
+          if git branch -r | grep -q "nightly-testing-${MOST_RECENT_NIGHTLY}"; then
+            BASE=nightly-testing-${MOST_RECENT_NIGHTLY}
           else
             echo "This shouldn't be possible: couldn't find a 'nightly-testing-${MOST_RECENT_NIGHTLY}' branch at Mathlib. Falling back to 'nightly-testing'."
             BASE=nightly-testing
           fi
 
-          echo "Using base tag: $BASE"
+          echo "Using base branch: $BASE"
 
-          EXISTS="$(git ls-remote --heads origin lean-pr-testing-${{ steps.workflow-info.outputs.pullRequestNumber }} | wc -l)"
+          git checkout $BASE
+
+          EXISTS=$(git ls-remote --heads origin lean-pr-testing-${{ steps.workflow-info.outputs.pullRequestNumber }} | wc -l)
           echo "Branch exists: $EXISTS"
           if [ "$EXISTS" = "0" ]; then
             echo "Branch does not exist, creating it."
-            git switch -c lean-pr-testing-${{ steps.workflow-info.outputs.pullRequestNumber }} "$BASE"
+            git checkout -b lean-pr-testing-${{ steps.workflow-info.outputs.pullRequestNumber }}
             echo "leanprover/lean4-pr-releases:pr-release-${{ steps.workflow-info.outputs.pullRequestNumber }}" > lean-toolchain
             git add lean-toolchain
-            sed -i "s/require std from git \"https:\/\/github.com\/leanprover\/std4\" @ \".\+\"/require std from git \"https:\/\/github.com\/leanprover\/std4\" @ \"nightly-testing-${MOST_RECENT_NIGHTLY}\"/" lakefile.lean
-            git add lakefile.lean
             git commit -m "Update lean-toolchain for testing https://github.com/leanprover/lean4/pull/${{ steps.workflow-info.outputs.pullRequestNumber }}"
           else
             echo "Branch already exists, pushing an empty commit."
-            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
+            git checkout lean-pr-testing-${{ steps.workflow-info.outputs.pullRequestNumber }}
+            # The Mathlib `nightly-testing` or `nightly-testing-YYYY-MM-DD` branch may have moved since this branch was created, so merge their changes.
+            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 }}"
           fi
 

.github/workflows/pr-title.yml

@@ -10,7 +10,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Check PR title
-        uses: actions/github-script@v7
+        uses: actions/github-script@v6
         with:
           script: |
             const msg = context.payload.pull_request? context.payload.pull_request.title : context.payload.merge_group.head_commit.message;

.github/workflows/update-stage0.yml

@@ -1,64 +0,0 @@
-name: Update stage0
-
-# This action will update stage0 on master as soon as
-# src/stdlib_flags.h and stage0/src/stdlib_flags.h
-# are out of sync there, or when manually triggered.
-# The update bypasses the merge queue to be quick.
-# Also see <doc/dev/bootstrap.md>.
-
-on:
-  push:
-    branches:
-      - 'master'
-  workflow_dispatch:
-
-concurrency:
-  group: stage0
-  cancel-in-progress: true
-
-jobs:
-  update-stage0:
-    runs-on: ubuntu-latest
-    steps:
-    # This action should push to an otherwise protected branch, so it
-    # uses a deploy key with write permissions, as suggested at
-    # https://stackoverflow.com/a/76135647/946226
-    - uses: actions/checkout@v3
-      with:
-        ssh-key: ${{secrets.STAGE0_SSH_KEY}}
-    - run: echo "should_update_stage0=yes" >> "$GITHUB_ENV"
-    - name: Check if automatic update is needed
-      if: github.event_name == 'push'
-      run: |
-        if diff -u src/stdlib_flags.h stage0/src/stdlib_flags.h
-        then
-          echo "src/stdlib_flags.h and stage0/src/stdlib_flags.h agree, nothing to do"
-          echo "should_update_stage0=no" >> "$GITHUB_ENV"
-        fi
-    - name: Setup git user
-      if: env.should_update_stage0 == 'yes'
-      run: |
-          git config --global user.name "Lean stage0 autoupdater"
-          git config --global user.email "<>"
-    - if: env.should_update_stage0 == 'yes'
-      uses: DeterminateSystems/nix-installer-action@main
-    # 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: Install Cachix
-      uses: cachix/cachix-action@v12
-      with:
-        name: lean4
-    - if: env.should_update_stage0 == 'yes'
-      run: nix run .#update-stage0-commit
-    - if: env.should_update_stage0 == 'yes'
-      run: git show --stat
-    - if: env.should_update_stage0 == 'yes' && github.event_name == 'push'
-      name: Sanity check # to avoid loops
-      run: |
-        diff -u src/stdlib_flags.h stage0/src/stdlib_flags.h || exit 1
-    - if: env.should_update_stage0 == 'yes'
-      run: git push origin

CODEOWNERS

@@ -18,5 +18,4 @@
 /src/Lean/Parser/ @Kha
 /src/Lean/PrettyPrinter/ @Kha
 /src/Lean/Server/ @mhuisi
-/src/Lean/Widget/ @Vtec234
 /src/runtime/io.cpp @joehendrix

README.md

@@ -1,8 +1,13 @@
 This is the repository for **Lean 4**.
 
+We provide [nightly releases](https://github.com/leanprover/lean4-nightly/releases)
+and have just begun regular [stable point releases](https://github.com/leanprover/lean4/releases).
+
 # About
 
-- [Quickstart](https://lean-lang.org/lean4/doc/quickstart.html)
+- [Quickstart](https://github.com/leanprover/lean4/blob/master/doc/quickstart.md)
+- [Walkthrough installation video](https://www.youtube.com/watch?v=yZo6k48L0VY)
+- [Quick tour video](https://youtu.be/zyXtbb_eYbY)
 - [Homepage](https://lean-lang.org)
 - [Theorem Proving Tutorial](https://lean-lang.org/theorem_proving_in_lean4/)
 - [Functional Programming in Lean](https://lean-lang.org/functional_programming_in_lean/)

RELEASES.md

@@ -8,357 +8,30 @@ This file contains work-in-progress notes for the upcoming release, as well as p
 Please check the [releases](https://github.com/leanprover/lean4/releases) page for the current status
 of each version.
 
-v4.7.0 (development in progress)
+v4.5.0 (development in progress)
 ---------
 
-v4.6.0
----------
-
-* Add custom simplification procedures (aka `simproc`s) to `simp`. Simprocs can be triggered by the simplifier on a specified term-pattern. Here is an small example:
-```lean
-import Lean.Meta.Tactic.Simp.BuiltinSimprocs.Nat
-
-def foo (x : Nat) : Nat :=
-  x + 10
-
-/--
-The `simproc` `reduceFoo` is invoked on terms that match the pattern `foo _`.
--/
-simproc reduceFoo (foo _) :=
-  /- A term of type `Expr → SimpM Step -/
-  fun e => do
-    /-
-    The `Step` type has three constructors: `.done`, `.visit`, `.continue`.
-    * The constructor `.done` instructs `simp` that the result does
-      not need to be simplied further.
-    * The constructor `.visit` instructs `simp` to visit the resulting expression.
-    * The constructor `.continue` instructs `simp` to try other simplification procedures.
-
-    All three constructors take a `Result`. The `.continue` contructor may also take `none`.
-    `Result` has two fields `expr` (the new expression), and `proof?` (an optional proof).
-     If the new expression is definitionally equal to the input one, then `proof?` can be omitted or set to `none`.
-    -/
-    /- `simp` uses matching modulo reducibility. So, we ensure the term is a `foo`-application. -/
-    unless e.isAppOfArity ``foo 1 do
-      return .continue
-    /- `Nat.fromExpr?` tries to convert an expression into a `Nat` value -/
-    let some n ← Nat.fromExpr? e.appArg!
-      | return .continue
-    return .done { expr := Lean.mkNatLit (n+10) }
-```
-We disable simprocs support by using the command `set_option simprocs false`. This command is particularly useful when porting files to v4.6.0.
-Simprocs can be scoped, manually added to `simp` commands, and suppressed using `-`. They are also supported by `simp?`. `simp only` does not execute any `simproc`. Here are some examples for the `simproc` defined above.
-```lean
-example : x + foo 2 = 12 + x := by
-  set_option simprocs false in
-    /- This `simp` command does not make progress since `simproc`s are disabled. -/
-    fail_if_success simp
-  simp_arith
-
-example : x + foo 2 = 12 + x := by
-  /- `simp only` must not use the default simproc set. -/
-  fail_if_success simp only
-  simp_arith
-
-example : x + foo 2 = 12 + x := by
-  /-
-  `simp only` does not use the default simproc set,
-  but we can provide simprocs as arguments. -/
-  simp only [reduceFoo]
-  simp_arith
-
-example : x + foo 2 = 12 + x := by
-  /- We can use `-` to disable `simproc`s. -/
-  fail_if_success simp [-reduceFoo]
-  simp_arith
-```
-The command `register_simp_attr <id>` now creates a `simp` **and** a `simproc` set with the name `<id>`. The following command instructs Lean to insert the `reduceFoo` simplification procedure into the set `my_simp`. If no set is specified, Lean uses the default `simp` set.
-```lean
-simproc [my_simp] reduceFoo (foo _) := ...
-```
-
-* The syntax of the `termination_by` and `decreasing_by` termination hints is overhauled:
-
-  * They are now placed directly after the function they apply to, instead of
-    after the whole `mutual` block.
-  * Therefore, the function name no longer has to be mentioned in the hint.
-  * If the function has a `where` clause, the `termination_by` and
-    `decreasing_by` for that function come before the `where`. The
-    functions in the `where` clause can have their own termination hints, each
-    following the corresponding definition.
-  * The `termination_by` clause can only bind “extra parameters”, that are not
-    already bound by the function header, but are bound in a lambda (`:= fun x
-    y z =>`) or in patterns (`| x, n + 1 => …`). These extra parameters used to
-    be understood as a suffix of the function parameters; now it is a prefix.
-
-  Migration guide: In simple cases just remove the function name, and any
-  variables already bound at the header.
-  ```diff
-   def foo : Nat → Nat → Nat := …
-  -termination_by foo a b => a - b
-  +termination_by a b => a - b
-  ```
-  or
-  ```diff
-   def foo : Nat → Nat → Nat := …
-  -termination_by _ a b => a - b
-  +termination_by a b => a - b
-  ```
-
-  If the parameters are bound in the function header (before the `:`), remove them as well:
-  ```diff
-   def foo (a b : Nat) : Nat := …
-  -termination_by foo a b => a - b
-  +termination_by a - b
-  ```
-
-  Else, if there are multiple extra parameters, make sure to refer to the right
-  ones; the bound variables are interpreted from left to right, no longer from
-  right to left:
-  ```diff
-   def foo : Nat → Nat → Nat → Nat
-     | a, b, c => …
-  -termination_by foo b c => b
-  +termination_by a b => b
-  ```
-
-  In the case of a `mutual` block, place the termination arguments (without the
-  function name) next to the function definition:
-  ```diff
-  -mutual
-  -def foo : Nat → Nat → Nat := …
-  -def bar : Nat → Nat := …
-  -end
-  -termination_by
-  -  foo a b => a - b
-  -  bar a => a
-  +mutual
-  +def foo : Nat → Nat → Nat := …
-  +termination_by a b => a - b
-  +def bar : Nat → Nat := …
-  +termination_by a => a
-  +end
-  ```
-
-  Similarly, if you have (mutual) recursion through `where` or `let rec`, the
-  termination hints are now placed directly after the function they apply to:
-  ```diff
-  -def foo (a b : Nat) : Nat := …
-  -  where bar (x : Nat) : Nat := …
-  -termination_by
-  -  foo a b => a - b
-  -  bar x => x
-  +def foo (a b : Nat) : Nat := …
-  +termination_by a - b
-  +  where
-  +    bar (x : Nat) : Nat := …
-  +    termination_by x
-
-  -def foo (a b : Nat) : Nat :=
-  -  let rec bar (x : Nat) :  Nat := …
-  -  …
-  -termination_by
-  -  foo a b => a - b
-  -  bar x => x
-  +def foo (a b : Nat) : Nat :=
-  +  let rec bar (x : Nat) : Nat := …
-  +    termination_by x
-  +  …
-  +termination_by a - b
-  ```
-
-  In cases where a single `decreasing_by` clause applied to multiple mutually
-  recursive functions before, the tactic now has to be duplicated.
-
-* The semantics of `decreasing_by` changed; the tactic is applied to all
-  termination proof goals together, not individually.
-
-  This helps when writing termination proofs interactively, as one can focus
-  each subgoal individually, for example using `·`. Previously, the given
-  tactic script had to work for _all_ goals, and one had to resort to tactic
-  combinators like `first`:
-
-  ```diff
-   def foo (n : Nat) := … foo e1 … foo e2 …
-  -decreasing_by
-  -simp_wf
-  -first | apply something_about_e1; …
-  -      | apply something_about_e2; …
-  +decreasing_by
-  +all_goals simp_wf
-  +· apply something_about_e1; …
-  +· apply something_about_e2; …
-  ```
-
-  To obtain the old behaviour of applying a tactic to each goal individually,
-  use `all_goals`:
-  ```diff
-   def foo (n : Nat) := …
-  -decreasing_by some_tactic
-  +decreasing_by all_goals some_tactic
-  ```
-
-  In the case of mutual recursion each `decreasing_by` now applies to just its
-  function. If some functions in a recursive group do not have their own
-  `decreasing_by`, the default `decreasing_tactic` is used. If the same tactic
-  ought to be applied to multiple functions, the `decreasing_by` clause has to
-  be repeated at each of these functions.
-
-* Modify `InfoTree.context` to facilitate augmenting it with partial contexts while elaborating a command. This breaks backwards compatibility with all downstream projects that traverse the `InfoTree` manually instead of going through the functions in `InfoUtils.lean`, as well as those manually creating and saving `InfoTree`s. See [PR #3159](https://github.com/leanprover/lean4/pull/3159) for how to migrate your code.
-
-* Add language server support for [call hierarchy requests](https://www.youtube.com/watch?v=r5LA7ivUb2c) ([PR #3082](https://github.com/leanprover/lean4/pull/3082)). The change to the .ilean format in this PR means that projects must be fully rebuilt once in order to generate .ilean files with the new format before features like "find references" work correctly again.
-
-* Structure instances with multiple sources (for example `{a, b, c with x := 0}`) now have their fields filled from these sources
-  in strict left-to-right order. Furthermore, the structure instance elaborator now aggressively use sources to fill in subobject
-  fields, which prevents unnecessary eta expansion of the sources,
-  and hence greatly reduces the reliance on costly structure eta reduction. This has a large impact on mathlib,
-  reducing total CPU instructions by 3% and enabling impactful refactors like leanprover-community/mathlib4#8386
-  which reduces the build time by almost 20%.
-  See PR [#2478](https://github.com/leanprover/lean4/pull/2478) and RFC [#2451](https://github.com/leanprover/lean4/issues/2451).
-
-* Add pretty printer settings to omit deeply nested terms (`pp.deepTerms false` and `pp.deepTerms.threshold`) ([PR #3201](https://github.com/leanprover/lean4/pull/3201))
-
-* Add pretty printer options `pp.numeralTypes` and `pp.natLit`.
-  When `pp.numeralTypes` is true, then natural number literals, integer literals, and rational number literals
-  are pretty printed with type ascriptions, such as `(2 : Rat)`, `(-2 : Rat)`, and `(-2 / 3 : Rat)`.
-  When `pp.natLit` is true, then raw natural number literals are pretty printed as `nat_lit 2`.
-  [PR #2933](https://github.com/leanprover/lean4/pull/2933) and [RFC #3021](https://github.com/leanprover/lean4/issues/3021).
-
-Lake updates:
-* improved platform information & control [#3226](https://github.com/leanprover/lean4/pull/3226)
-* `lake update` from unsupported manifest versions [#3149](https://github.com/leanprover/lean4/pull/3149)
-
-Other improvements:
-* make `intro` be aware of `let_fun` [#3115](https://github.com/leanprover/lean4/pull/3115)
-* produce simpler proof terms in `rw` [#3121](https://github.com/leanprover/lean4/pull/3121)
-* fuse nested `mkCongrArg` calls in proofs generated by `simp` [#3203](https://github.com/leanprover/lean4/pull/3203)
-* `induction using` followed by a general term [#3188](https://github.com/leanprover/lean4/pull/3188)
-* allow generalization in `let` [#3060](https://github.com/leanprover/lean4/pull/3060, fixing [#3065](https://github.com/leanprover/lean4/issues/3065)
-* reducing out-of-bounds `swap!` should return `a`, not `default`` [#3197](https://github.com/leanprover/lean4/pull/3197), fixing [#3196](https://github.com/leanprover/lean4/issues/3196)
-* derive `BEq` on structure with `Prop`-fields [#3191](https://github.com/leanprover/lean4/pull/3191), fixing [#3140](https://github.com/leanprover/lean4/issues/3140)
-* refine through more `casesOnApp`/`matcherApp` [#3176](https://github.com/leanprover/lean4/pull/3176), fixing [#3175](https://github.com/leanprover/lean4/pull/3175)
-* do not strip dotted components from lean module names [#2994](https://github.com/leanprover/lean4/pull/2994), fixing [#2999](https://github.com/leanprover/lean4/issues/2999)
-* fix `deriving` only deriving the first declaration for some handlers [#3058](https://github.com/leanprover/lean4/pull/3058), fixing [#3057](https://github.com/leanprover/lean4/issues/3057)
-* do not instantiate metavariables in kabstract/rw for disallowed occurrences [#2539](https://github.com/leanprover/lean4/pull/2539), fixing [#2538](https://github.com/leanprover/lean4/issues/2538)
-* hover info for `cases h : ...` [#3084](https://github.com/leanprover/lean4/pull/3084)
-
-v4.5.0
----------
-
-* Modify the lexical syntax of string literals to have string gaps, which are escape sequences of the form `"\" newline whitespace*`.
-  These have the interpetation of an empty string and allow a string to flow across multiple lines without introducing additional whitespace.
-  The following is equivalent to `"this is a string"`.
-  ```lean
-  "this is \
-     a string"
-  ```
-  [PR #2821](https://github.com/leanprover/lean4/pull/2821) and [RFC #2838](https://github.com/leanprover/lean4/issues/2838).
-
-* Add raw string literal syntax. For example, `r"\n"` is equivalent to `"\\n"`, with no escape processing.
-  To include double quote characters in a raw string one can add sufficiently many `#` characters before and after
-  the bounding `"`s, as in `r#"the "the" is in quotes"#` for `"the \"the\" is in quotes"`.
-  [PR #2929](https://github.com/leanprover/lean4/pull/2929) and [issue #1422](https://github.com/leanprover/lean4/issues/1422).
-
-* The low-level `termination_by'` clause is no longer supported.
-
-  Migration guide: Use `termination_by` instead, e.g.:
-  ```diff
-  -termination_by' measure (fun ⟨i, _⟩ => as.size - i)
-  +termination_by i _ => as.size - i
-  ```
-
-  If the well-founded relation you want to use is not the one that the
-  `WellFoundedRelation` type class would infer for your termination argument,
-  you can use `WellFounded.wrap` from the std libarary to explicitly give one:
-  ```diff
-  -termination_by' ⟨r, hwf⟩
-  +termination_by x => hwf.wrap x
-  ```
-
-* Support snippet edits in LSP `TextEdit`s. See `Lean.Lsp.SnippetString` for more details.
-
-* Deprecations and changes in the widget API.
-  - `Widget.UserWidgetDefinition` is deprecated in favour of `Widget.Module`. The annotation `@[widget]` is deprecated in favour of `@[widget_module]`. To migrate a definition of type `UserWidgetDefinition`, remove the `name` field and replace the type with `Widget.Module`. Removing the `name` results in a title bar no longer being drawn above your panel widget. To add it back, draw it as part of the component using `<details open=true><summary class='mv2 pointer'>{name}</summary>{rest_of_widget}</details>`. See an example migration [here](https://github.com/leanprover/std4/pull/475/files#diff-857376079661a0c28a53b7ff84701afabbdf529836a6944d106c5294f0e68109R43-R83).
-  - The new command `show_panel_widgets` allows displaying always-on and locally-on panel widgets.
-  - `RpcEncodable` widget props can now be stored in the infotree.
-  - See [RFC 2963](https://github.com/leanprover/lean4/issues/2963) for more details and motivation.
-
-* If no usable lexicographic order can be found automatically for a termination proof, explain why.
-  See [feat: GuessLex: if no measure is found, explain why](https://github.com/leanprover/lean4/pull/2960).
-
-* Option to print [inferred termination argument](https://github.com/leanprover/lean4/pull/3012).
-  With `set_option showInferredTerminationBy true` you will get messages like
-  ```
-  Inferred termination argument:
-  termination_by
-  ackermann n m => (sizeOf n, sizeOf m)
-  ```
-  for automatically generated `termination_by` clauses.
-
-* More detailed error messages for [invalid mutual blocks](https://github.com/leanprover/lean4/pull/2949).
-
-* [Multiple](https://github.com/leanprover/lean4/pull/2923) [improvements](https://github.com/leanprover/lean4/pull/2969) to the output of `simp?` and `simp_all?`.
-
-* Tactics with `withLocation *` [no longer fail](https://github.com/leanprover/lean4/pull/2917) if they close the main goal.
-
-* Implementation of a `test_extern` command for writing tests for `@[extern]` and `@[implemented_by]` functions.
-  Usage is
-  ```
-  import Lean.Util.TestExtern
-
-  test_extern Nat.add 17 37
-  ```
-  The head symbol must be the constant with the `@[extern]` or `@[implemented_by]` attribute. The return type must have a `DecidableEq` instance.
-
-Bug fixes for
-[#2853](https://github.com/leanprover/lean4/issues/2853), [#2953](https://github.com/leanprover/lean4/issues/2953), [#2966](https://github.com/leanprover/lean4/issues/2966),
-[#2971](https://github.com/leanprover/lean4/issues/2971), [#2990](https://github.com/leanprover/lean4/issues/2990), [#3094](https://github.com/leanprover/lean4/issues/3094).
-
-Bug fix for [eager evaluation of default value](https://github.com/leanprover/lean4/pull/3043) in `Option.getD`.
-Avoid [panic in `leanPosToLspPos`](https://github.com/leanprover/lean4/pull/3071) when file source is unavailable.
-Improve [short-circuiting behavior](https://github.com/leanprover/lean4/pull/2972) for `List.all` and `List.any`.
-
-Several Lake bug fixes: [#3036](https://github.com/leanprover/lean4/issues/3036), [#3064](https://github.com/leanprover/lean4/issues/3064), [#3069](https://github.com/leanprover/lean4/issues/3069).
-
 v4.4.0
 ---------
 
-* Lake and the language server now support per-package server options using the `moreServerOptions` config field, as well as options that apply to both the language server and `lean` using the `leanOptions` config field. Setting either of these fields instead of `moreServerArgs` ensures that viewing files from a dependency uses the options for that dependency. Additionally, `moreServerArgs` is being deprecated in favor of the `moreGlobalServerArgs` field. See PR [#2858](https://github.com/leanprover/lean4/pull/2858).
-
-  A Lakefile with the following deprecated package declaration:
-  ```lean
-  def moreServerArgs := #[
-    "-Dpp.unicode.fun=true"
-  ]
-  def moreLeanArgs := moreServerArgs
-
-  package SomePackage where
-    moreServerArgs := moreServerArgs
-    moreLeanArgs := moreLeanArgs
-  ```
-
-  ... can be updated to the following package declaration to use per-package options:
-  ```lean
-  package SomePackage where
-    leanOptions := #[⟨`pp.unicode.fun, true⟩]
-  ```
 * [Rename request handler](https://github.com/leanprover/lean4/pull/2462).
 * [Import auto-completion](https://github.com/leanprover/lean4/pull/2904).
 * [`pp.beta`` to apply beta reduction when pretty printing](https://github.com/leanprover/lean4/pull/2864).
+* [Per-package server options](https://github.com/leanprover/lean4/pull/2858).
 * [Embed and check githash in .olean](https://github.com/leanprover/lean4/pull/2766).
 * [Guess lexicographic order for well-founded recursion](https://github.com/leanprover/lean4/pull/2874).
 * [Allow trailing comma in tuples, lists, and tactics](https://github.com/leanprover/lean4/pull/2643).
 
-Bug fixes for [#2628](https://github.com/leanprover/lean4/issues/2628), [#2883](https://github.com/leanprover/lean4/issues/2883),
-[#2810](https://github.com/leanprover/lean4/issues/2810), [#2925](https://github.com/leanprover/lean4/issues/2925), and [#2914](https://github.com/leanprover/lean4/issues/2914).
+Bug fixes for [#2628](https://github.com/leanprover/lean4/issue/2628), [#2883](https://github.com/leanprover/lean4/issue/2883),
+[#2810](https://github.com/leanprover/lean4/issue/2810), [#2925](https://github.com/leanprover/lean4/issue/2925), and [#2914](https://github.com/leanprover/lean4/issue/2914).
 
 **Lake:**
 
 * `lake init .` and a bare `lake init` and will now use the current directory as the package name. [#2890](https://github.com/leanprover/lean4/pull/2890)
-* `lake new` and `lake init` will now produce errors on invalid package names such as `..`, `foo/bar`, `Init`, `Lean`, `Lake`, and `Main`. See issue [#2637](https://github.com/leanprover/lean4/issues/2637) and PR [#2890](https://github.com/leanprover/lean4/pull/2890).
-* `lean_lib` no longer converts its name to upper camel case (e.g., `lean_lib bar` will include modules named `bar.*` rather than `Bar.*`). See issue [#2567](https://github.com/leanprover/lean4/issues/2567) and PR [#2889](https://github.com/leanprover/lean4/pull/2889).
-* Lean and Lake now properly support non-identifier library names (e.g., `lake new 123-hello` and `import «123Hello»` now work correctly). See issue [#2865](https://github.com/leanprover/lean4/issues/2865) and PR [#2889](https://github.com/leanprover/lean4/pull/2888).
-* Lake now filters the environment extensions loaded from a compiled configuration (`lakefile.olean`) to include only those relevant to Lake's workspace loading process. This resolves segmentation faults caused by environment extension type mismatches (e.g., when defining custom elaborators via `elab` in configurations). See issue [#2632](https://github.com/leanprover/lean4/issues/2632) and PR [#2896](https://github.com/leanprover/lean4/pull/2896).
+* `lake new` and `lake init` will now produce errors on invalid package names such as `..`, `foo/bar`, `Init`, `Lean`, `Lake`, and `Main`. See issue [#2637](https://github.com/leanprover/lean4/issue/2637) and PR [#2890](https://github.com/leanprover/lean4/pull/2890).
+* `lean_lib` no longer converts its name to upper camel case (e.g., `lean_lib bar` will include modules named `bar.*` rather than `Bar.*`). See issue [#2567](https://github.com/leanprover/lean4/issue/2567) and PR [#2889](https://github.com/leanprover/lean4/pull/2889).
+* Lean and Lake now properly support non-identifier library names (e.g., `lake new 123-hello` and `import «123Hello»` now work correctly). See issue [#2865](https://github.com/leanprover/lean4/issue/2865) and PR [#2889](https://github.com/leanprover/lean4/pull/2888).
+* Lake now filters the environment extensions loaded from a compiled configuration (`lakefile.olean`) to include only those relevant to Lake's workspace loading process. This resolves segmentation faults caused by environment extension type mismatches (e.g., when defining custom elaborators via `elab` in configurations). See issue [#2632](https://github.com/leanprover/lean4/issue/2632) and PR [#2896](https://github.com/leanprover/lean4/pull/2896).
 * Cloud releases will now properly be re-unpacked if the build directory is removed. See PR [#2928](https://github.com/leanprover/lean4/pull/2928).
 * Lake's `math` template has been simplified. See PR [#2930](https://github.com/leanprover/lean4/pull/2930).
 * `lake exe <target>` now parses `target` like a build target (as the help text states it should) rather than as a basic name. For example, `lake exe @mathlib/runLinter` should now work. See PR [#2932](https://github.com/leanprover/lean4/pull/2932).

doc/SUMMARY.md

@@ -4,6 +4,7 @@
 - [Tour of Lean](./tour.md)
 - [Setting Up Lean](./quickstart.md)
   - [Extended Setup Notes](./setup.md)
+  - [Nix Setup](./setup/nix.md)
 - [Theorem Proving in Lean](./tpil.md)
 - [Functional Programming in Lean](fplean.md)
 - [Examples](./examples.md)
@@ -85,6 +86,7 @@
   - [macOS Setup](./make/osx-10.9.md)
   - [Windows MSYS2 Setup](./make/msys2.md)
   - [Windows with WSL](./make/wsl.md)
+  - [Nix Setup (*Experimental*)](./make/nix.md)
 - [Bootstrapping](./dev/bootstrap.md)
 - [Testing](./dev/testing.md)
 - [Debugging](./dev/debugging.md)

doc/declarations.md

@@ -483,43 +483,7 @@ def baz : Char → Nat
 | _   => 3
 ```
 
-The case where patterns are matched against an argument whose type is an inductive family is known as *dependent pattern matching*. This is more complicated, because the type of the function being defined can impose constraints on the patterns that are matched. In this case, the equation compiler will detect inconsistent cases and rule them out.
-
-```lean
-universe u
-
-inductive Vector (α : Type u) : Nat → Type u
-  | nil  : Vector α 0
-  | cons : α → Vector α n → Vector α (n+1)
-
-namespace Vector
-
-def head : Vector α (n+1) → α
-  | cons h t => h
-
-def tail : Vector α (n+1) → Vector α n
-  | cons h t => t
-
-def map (f : α → β → γ) : Vector α n → Vector β n → Vector γ n
-  | nil, nil => nil
-  | cons a va, cons b vb => cons (f a b) (map f va vb)
-
-end Vector
-```
-
-.. _recursive_functions:
-
-Recursive functions
-===================
-
-Lean must ensure that a recursive function terminates, for which there are two strategies: _structural recursion_, in which all recursive calls are made on smaller parts of the input data, and _well-founded recursion_, in which recursive calls are justified by showing that arguments to recursive calls are smaller according to some other measure.
-
-Structural recursion
---------------------
-
-If the definition of a function contains recursive calls, Lean first tries to interpret the definition as a structural recursion. In order for that to succeed, the recursive arguments must be subterms of the corresponding arguments on the left-hand side.
-
-The function is then defined using a *course of values* recursion, using automatically generated functions ``below`` and ``brec`` in the namespace corresponding to the inductive type of the recursive argument. In this case the defining equations hold definitionally, possibly with additional case splits.
+If any of the terms ``tᵢ`` in the template above contain a recursive call to ``foo``, the equation compiler tries to interpret the definition as a structural recursion. In order for that to succeed, the recursive arguments must be subterms of the corresponding arguments on the left-hand side. The function is then defined using a *course of values* recursion, using automatically generated functions ``below`` and ``brec`` in the namespace corresponding to the inductive type of the recursive argument. In this case the defining equations hold definitionally, possibly with additional case splits.
 
 ```lean
 namespace Hide
@@ -540,12 +504,7 @@ example : append [(1 : Nat), 2, 3] [4, 5] = [1, 2, 3, 4, 5] => rfl
 end Hide
 ```
 
-Well-founded recursion
----------------------
-
-If structural recursion fails, the equation compiler falls back on well-founded recursion. It tries to infer an instance of ``SizeOf`` for the type of each argument, and then tries to find a permutation of the arguments such that each recursive call is decreasing under the lexicographic order with respect to ``sizeOf`` measures.  Lean uses information in the local context, so you can often provide the relevant proof manually using ``have`` in the body of the definition.
-
-In the case of well-founded recursion, the equation used to declare the function holds only propositionally, but not definitionally, and can be accessed using ``unfold``, ``simp`` and ``rewrite`` with the function name (for example ``unfold foo`` or ``simp [foo]``, where ``foo`` is the function defined with well-founded recursion).
+If structural recursion fails, the equation compiler falls back on well-founded recursion. It tries to infer an instance of ``SizeOf`` for the type of each argument, and then show that each recursive call is decreasing under the lexicographic order of the arguments with respect to ``sizeOf`` measure. If it fails, the error message provides information as to the goal that Lean tried to prove. Lean uses information in the local context, so you can often provide the relevant proof manually using ``have`` in the body of the definition. In this case of well-founded recursion, the defining equations hold only propositionally, and can be accessed using ``simp`` and ``rewrite`` with the name ``foo``.
 
 ```lean
 namespace Hide
@@ -569,53 +528,9 @@ by rw [div]; rfl
 end Hide
 ```
 
-If Lean cannot find a permutation of the arguments for which all recursive calls are decreasing, it will print a table that contains, for every recursive call, which arguments Lean could prove to be decreasing. For example, a function with three recursive calls and four parameters might cause the following message to be printed
-
-```
-example.lean:37:0-43:31: error: Could not find a decreasing measure.
-The arguments relate at each recursive call as follows:
-(<, ≤, =: relation proved, ? all proofs failed, _: no proof attempted)
-           x1 x2 x3 x4
-1) 39:6-27  =  =  _  =
-2) 40:6-25  =  ?  _  <
-3) 41:6-25  <  _  _  _
-Please use `termination_by` to specify a decreasing measure.
-```
-
-This table should be read as follows:
-
- * In the first recursive call, in line 39, arguments 1, 2 and 4 are equal to the function's parameters.
- * The second recursive call, in line 40, has an equal first argument, a smaller fourth argument, and nothing could be inferred for the second argument.
- * The third recursive call, in line 41, has a decreasing first argument.
- * No other proofs were attempted, either because the parameter has a type without a non-trivial ``WellFounded`` instance (parameter 3), or because it is already clear that no decreasing measure can be found.
-
-
-Lean will print the termination argument it found if ``set_option showInferredTerminationBy true`` is set.
-
-If Lean does not find the termination argument, or if you want to be explicit, you can append a `termination_by` clause to the function definition, after the function's body, but before the `where` clause if present. It is of the form
-```
-termination_by e
-```
-where ``e`` is an expression that depends on the parameters of the function and should be decreasing at each recursive call. The type of `e` should be an instance of the class ``WellFoundedRelation``, which determines how to compare two values of that type.
-
-If ``f`` has parameters “after the ``:``” (for example when defining functions via patterns using `|`), then these can be brought into scope using the syntax
-```
-termination_by a₁ … aₙ => e
-```
-
-By default, Lean uses the tactic ``decreasing_tactic`` when proving that an argument is decreasing; see its documentation for how to globally extend it. You can also choose to use a different tactic for a given function definition with the clause
-```
-decreasing_by <tac>
-```
-which should come after ``termination_by`, if present.
-
-
 Note that recursive definitions can in general require nested recursions, that is, recursion on different arguments of ``foo`` in the template above. The equation compiler handles this by abstracting later arguments, and recursively defining higher-order functions to meet the specification.
 
-Mutual recursion
-----------------
-
-The equation compiler also allows mutual recursive definitions, with a syntax similar to that of [Mutual and Nested Inductive Definitions](#mutual-and-nested-inductive-definitions). Mutual definitions are always compiled using well-founded recursion, and so once again the defining equations hold only propositionally.
+The equation compiler also allows mutual recursive definitions, with a syntax similar to that of [Mutual and Nested Inductive Definitions](#mutual-and-nested-inductive-definitions). They are compiled using well-founded recursion, and so once again the defining equations hold only propositionally.
 
 ```lean
 mutual
@@ -672,31 +587,29 @@ def num_consts_lst : List Term → Nat
 end
 ```
 
-In a set of mutually recursive function, either all or no functions must have an explicit termination argument (``termination_by``). A change of the default termination tactic (``decreasing_by``) only affects the proofs about the recursive calls of that function, not the other functions in the group.
+The case where patterns are matched against an argument whose type is an inductive family is known as *dependent pattern matching*. This is more complicated, because the type of the function being defined can impose constraints on the patterns that are matched. In this case, the equation compiler will detect inconsistent cases and rule them out.
 
-```
-mutual
-theorem even_of_odd_succ : ∀ n, Odd (n + 1) → Even n
-| _, odd_succ n h => h
-termination_by n h => h
-decreasing_by decreasing_tactic
+```lean
+universe u
 
-theorem odd_of_even_succ : ∀ n, Even (n + 1) → Odd n
-| _, even_succ n h => h
-termination_by n h => h
-end
-```
+inductive Vector (α : Type u) : Nat → Type u
+| nil  : Vector α 0
+| cons : α → Vector α n → Vector α (n+1)
 
-Another way to express mutual recursion is using local function definitions in ``where`` or ``let rec`` clauses: these can be mutually recursive with each other and their containing function:
+namespace Vector
 
-```
-theorem even_of_odd_succ : ∀ n, Odd (n + 1) → Even n
-  | _, odd_succ n h => h
-termination_by n h => h
-  where
-    theorem odd_of_even_succ : ∀ n, Even (n + 1) → Odd n
-      | _, even_succ n h => h
-    termination_by n h => h
+def head {α : Type} : Vector α (n+1) → α
+| cons h t => h
+
+def tail {α : Type} : Vector α (n+1) → Vector α n
+| cons h t => t
+
+def map {α β γ : Type} (f : α → β → γ) :
+  ∀ {n}, Vector α n → Vector β n → Vector γ n
+| 0,   nil,       nil       => nil
+| n+1, cons a va, cons b vb => cons (f a b) (map f va vb)
+
+end Vector
 ```
 
 .. _match_expressions:

doc/dev/bootstrap.md

@@ -65,36 +65,16 @@ You now have a Lean binary and library that include your changes, though their
 own compilation was not influenced by them, that you can use to test your
 changes on test programs whose compilation *will* be influenced by the changes.
 
-## Updating stage0
-
 Finally, when we want to use new language features in the library, we need to
-update the archived C source code of the stage 0 compiler in `stage0/src`.
+update the stage 0 compiler, which can be done via `make -C stageN update-stage0`.
+`make update-stage0` without `-C` defaults to stage1.
 
-The github repository will automatically update stage0 on `master` once
-`src/stdlib_flags.h` and `stage0/src/stdlib_flags.h` are out of sync.
-
-If you have write access to the lean4 repository, you can also also manually
-trigger that process, for example to be able to use new features in the compiler itself.
-You can do that on <https://github.com/nomeata/lean4/actions/workflows/update-stage0.yml>
-or using Github CLI with
-```
-gh workflow run update-stage0.yml
-```
-
-Leaving stage0 updates to the CI automation is preferrable, but should you need
-to do it locally, you can use `make update-stage0` in `build/release`, to
-update `stage0` from `stage1`, `make -C stageN update-stage0` to update from
-another stage, or `nix run .#update-stage0-commit` to update using nix.
-
-Updates to `stage0` should be their own commits in the Git history. So should
-you have to include the stage0 update in your PR (rather than using above
-automation after merging changes), commit your work before running `make
-update-stage0`, commit the updated `stage0` compiler code with the commit
-message:
+Updates to `stage0` should be their own commits in the Git history. In
+other words, before running `make update-stage0`, please commit your
+work. Then, commit the updated `stage0` compiler code with the commit message:
 ```
 chore: update stage0
 ```
-and coordinate with the admins to not squash your PR.
 
 ## Further Bootstrapping Complications
 

doc/dev/ffi.md

@@ -121,4 +121,4 @@ Thus to e.g. run `#eval` on such a declaration, you need to
 Note that it is not sufficient to load the foreign library containing the external symbol because the interpreter depends on code that is emitted for each `@[extern]` declaration.
 Thus it is not possible to interpret an `@[extern]` declaration in the same file.
 
-See [`tests/compiler/foreign`](https://github.com/leanprover/lean4/tree/master/tests/compiler/foreign/) for an example.
+See `tests/compiler/foreign` for an example.

doc/dev/testing.md

@@ -5,6 +5,7 @@ After [building Lean](../make/index.md) you can run all the tests using
 cd build/release
 make test ARGS=-j4
 ```
+
 Change the 4 to the maximum number of parallel tests you want to
 allow. The best choice is the number of CPU cores on your machine as
 the tests are mostly CPU bound.  You can find the number of processors
@@ -16,12 +17,6 @@ adding the `-C stageN` argument. The default when run as above is stage 1.  The
 Lean tests will automatically use that stage's corresponding Lean
 executables
 
-Running `make test` will not pick up new test files; run
-```bash
-cmake build/release/stage1
-```
-to update the list of tests.
-
 You can also use `ctest` directly if you are in the right folder.  So
 to run stage1 tests with a 300 second timeout run this:
 
@@ -29,9 +24,6 @@ to run stage1 tests with a 300 second timeout run this:
 cd build/release/stage1
 ctest -j 4 --output-on-failure --timeout 300
 ```
-Useful `ctest` flags are `-R <name of test>` to run a single test, and
-`--rerun-failed` to run all tests that failed during the last run.
-You can also pass `ctest` flags via `make test ARGS="--rerun-failed"`.
 
 To get verbose output from ctest pass the `--verbose` command line
 option. Test output is normally suppressed and only summary
@@ -41,17 +33,17 @@ information is displayed. This option will show all test output.
 
 All these tests are included by [src/shell/CMakeLists.txt](https://github.com/leanprover/lean4/blob/master/src/shell/CMakeLists.txt):
 
-- [`tests/lean`](https://github.com/leanprover/lean4/tree/master/tests/lean/): contains tests that come equipped with a
-  .lean.expected.out file. The driver script [`test_single.sh`](https://github.com/leanprover/lean4/tree/master/tests/lean/test_single.sh) runs
+- `tests/lean`: contains tests that come equipped with a
+  .lean.expected.out file. The driver script `test_single.sh` runs
   each test and checks the actual output (*.produced.out) with the
   checked in expected output.
 
-- [`tests/lean/run`](https://github.com/leanprover/lean4/tree/master/tests/lean/run/): contains tests that are run through the lean
+- `tests/lean/run`: contains tests that are run through the lean
   command line one file at a time. These tests only look for error
   codes and do not check the expected output even though output is
   produced, it is ignored.
 
-- [`tests/lean/interactive`](https://github.com/leanprover/lean4/tree/master/tests/lean/interactive/): are designed to test server requests at a
+- `tests/lean/interactive`: are designed to test server requests at a
   given position in the input file. Each .lean file contains comments
   that indicate how to simulate a client request at that position.
   using a `--^` point to the line position. Example:
@@ -61,7 +53,7 @@ All these tests are included by [src/shell/CMakeLists.txt](https://github.com/le
     Bla.
       --^ textDocument/completion
     ```
-    In this example, the test driver [`test_single.sh`](https://github.com/leanprover/lean4/tree/master/tests/lean/interactive/test_single.sh) will simulate an
+    In this example, the test driver `test_single.sh` will simulate an
     auto-completion request at `Bla.`. The expected output is stored in
     a .lean.expected.out in the json format that is part of the
     [Language Server
@@ -78,21 +70,21 @@ All these tests are included by [src/shell/CMakeLists.txt](https://github.com/le
     --^ collectDiagnostics
     ```
 
-- [`tests/lean/server`](https://github.com/leanprover/lean4/tree/master/tests/lean/server/): Tests more of the Lean `--server` protocol.
+- `tests/lean/server`: Tests more of the Lean `--server` protocol.
   There are just a few of them, and it uses .log files containing
   JSON.
 
-- [`tests/compiler`](https://github.com/leanprover/lean4/tree/master/tests/compiler/): contains tests that will run the Lean compiler and
+- `tests/compiler`: contains tests that will run the Lean compiler and
   build an executable that is executed and the output is compared to
   the .lean.expected.out file. This test also contains a subfolder
-  [`foreign`](https://github.com/leanprover/lean4/tree/master/tests/compiler/foreign/) which shows how to extend Lean using C++.
+  `foreign` which shows how to extend Lean using C++.
 
-- [`tests/lean/trust0`](https://github.com/leanprover/lean4/tree/master/tests/lean/trust0): tests that run Lean in a mode that Lean doesn't
+- `tests/lean/trust0`: tests that run Lean in a mode that Lean doesn't
   even trust the .olean files (i.e., trust 0).
 
-- [`tests/bench`](https://github.com/leanprover/lean4/tree/master/tests/bench/): contains performance tests.
+- `tests/bench`: contains performance tests.
 
-- [`tests/plugin`](https://github.com/leanprover/lean4/tree/master/tests/plugin/): tests that compiled Lean code can be loaded into
+- `tests/plugin`: tests that compiled Lean code can be loaded into
   `lean` via the `--plugin` command line option.
 
 ## Writing Good Tests
@@ -103,7 +95,7 @@ Every test file should contain:
   and, if not 100% clear, why that is the desirable behavior
 
 At the time of writing, most tests do not follow these new guidelines yet.
-For an example of a conforming test, see [`tests/lean/1971.lean`](https://github.com/leanprover/lean4/tree/master/tests/lean/1971.lean).
+For an example of a conforming test, see `tests/lean/1971.lean`.
 
 ## Fixing Tests
 
@@ -119,7 +111,7 @@ First, we must install [meld](http://meldmerge.org/). On Ubuntu, we can do it by
 sudo apt-get install meld
 ```
 
-Now, suppose `bad_class.lean` test is broken. We can see the problem by going to [`tests/lean`](https://github.com/leanprover/lean4/tree/master/tests/lean) directory and
+Now, suppose `bad_class.lean` test is broken. We can see the problem by going to `tests/lean` directory and
 executing
 
 ```
@@ -132,3 +124,8 @@ outputs. `meld` can also be used to repair the problems.
 
 In Emacs, we can also execute `M-x lean4-diff-test-file` to check/diff the file of the current buffer.
 To mass-copy all `.produced.out` files to the respective `.expected.out` file, use `tests/lean/copy-produced`.
+When using the Nix setup, add `--keep-failed` to the `nix build` call and then call
+```sh
+tests/lean/copy-produced <build-dir>/source/tests/lean
+```
+instead where `<build-dir>` is the path printed out by `nix build`.

doc/examples/palindromes.lean

@@ -82,7 +82,7 @@ theorem List.palindrome_ind (motive : List α → Prop)
     have ih := palindrome_ind motive h₁ h₂ h₃ (a₂::as').dropLast
     have : [a₁] ++ (a₂::as').dropLast ++ [(a₂::as').last (by simp)] = a₁::a₂::as' := by simp
     this ▸ h₃ _ _ _ ih
-termination_by as.length
+termination_by _ as => as.length
 
 /-!
 We use our new induction principle to prove that if `as.reverse = as`, then `Palindrome as` holds.

doc/examples/widgets.lean

@@ -15,8 +15,9 @@ sections of a Lean document. User widgets are rendered in the Lean infoview.
 To try it out, simply type in the following code and place your cursor over the `#widget` command.
 -/
 
-@[widget_module]
-def helloWidget : Widget.Module where
+@[widget]
+def helloWidget : UserWidgetDefinition where
+  name := "Hello"
   javascript := "
     import * as React from 'react';
     export default function(props) {
@@ -24,7 +25,7 @@ def helloWidget : Widget.Module where
       return React.createElement('p', {}, name + '!')
     }"
 
-#widget helloWidget
+#widget helloWidget .null
 
 /-!
 If you want to dive into a full sample right away, check out
@@ -55,11 +56,7 @@ to the React component. In our first invocation of `#widget`, we set it to `.nul
 happens when you type in:
 -/
 
-structure HelloWidgetProps where
-  name? : Option String := none
-  deriving Server.RpcEncodable
-
-#widget helloWidget with { name? := "<your name here>" : HelloWidgetProps }
+#widget helloWidget (Json.mkObj [("name", "<your name here>")])
 
 /-!
 💡 NOTE: The RPC system presented below does not depend on JavaScript. However the primary use case
@@ -135,8 +132,9 @@ on this we either display an `InteractiveCode` with the type, `mapRpcError` the
 to turn it into a readable message, or show a `Loading..` message, respectively.
 -/
 
-@[widget_module]
-def checkWidget : Widget.Module where
+@[widget]
+def checkWidget : UserWidgetDefinition where
+  name := "#check as a service"
   javascript := "
 import * as React from 'react';
 const e = React.createElement;
@@ -162,7 +160,7 @@ export default function(props) {
 Finally we can try out the widget.
 -/
 
-#widget checkWidget
+#widget checkWidget .null
 
 /-!
 ![`#check` as a service](../images/widgets_caas.png)
@@ -195,8 +193,9 @@ interact with the text editor.
 You can see the full API for this [here](https://github.com/leanprover/vscode-lean4/blob/master/lean4-infoview-api/src/infoviewApi.ts#L52)
 -/
 
-@[widget_module]
-def insertTextWidget : Widget.Module where
+@[widget]
+def insertTextWidget : UserWidgetDefinition where
+  name := "textInserter"
   javascript := "
 import * as React from 'react';
 const e = React.createElement;
@@ -214,4 +213,4 @@ export default function(props) {
 
 /-! Finally, we can try this out: -/
 
-#widget insertTextWidget
+#widget insertTextWidget .null

doc/flake.lock

@@ -69,16 +69,15 @@
     "leanInk": {
       "flake": false,
       "locked": {
-        "lastModified": 1704976501,
-        "narHash": "sha256-FSBUsbX0HxakSnYRYzRBDN2YKmH9EkA0q9p7TSPEJTI=",
-        "owner": "leanprover",
+        "lastModified": 1666154782,
+        "narHash": "sha256-0ELqEca6jZT4BW/mqkDD+uYuxW5QlZUFlNwZkvugsg8=",
+        "owner": "digama0",
         "repo": "LeanInk",
-        "rev": "51821e3c2c032c88e4b2956483899d373ec090c4",
+        "rev": "12a2aec9b5f4aa84e84fb01a9af1da00d8aaff4e",
         "type": "github"
       },
       "original": {
         "owner": "leanprover",
-        "ref": "refs/pull/57/merge",
         "repo": "LeanInk",
         "type": "github"
       }

doc/flake.nix

@@ -12,7 +12,7 @@
     flake = false;
   };
   inputs.leanInk = {
-    url = "github:leanprover/LeanInk/refs/pull/57/merge";
+    url = "github:leanprover/LeanInk";
     flake = false;
   };
 

doc/functions.md

@@ -32,8 +32,8 @@ def fact x :=
 
 #eval fact 100
 ```
-By default, Lean only accepts total functions.
-The `partial` keyword may be used to define a recursive function without a termination proof; `partial` functions compute in compiled programs, but are opaque in proofs and during type checking.
+By default, Lean only accepts total functions. The `partial` keyword should be used when Lean cannot
+establish that a function always terminates.
 ```lean
 partial def g (x : Nat) (p : Nat -> Bool) : Nat :=
   if p x then

doc/lexical_structure.md

@@ -8,7 +8,7 @@ A Lean program consists of a stream of UTF-8 tokens where each token
 is one of the following:
 
 ```
-   token: symbol | command | ident | string | raw_string | char | numeral |
+   token: symbol | command | ident | string | char | numeral |
         : decimal | doc_comment | mod_doc_comment | field_notation
 ```
 
@@ -79,35 +79,15 @@ special characters:
 [Unicode table](https://unicode-table.com/en/) so "\xA9 Copyright 2021" is "© Copyright 2021".
 - `\uHHHH` puts the character represented by the 4 digit hexadecimal into the string, so the following
 string "\u65e5\u672c" will become "日本" which means "Japan".
-- `\` followed by a newline and then any amount of whitespace is a "gap" that is equivalent to the empty string,
-useful for letting a string literal span across multiple lines. Gaps spanning multiple lines can be confusing,
-so the parser raises an error if the trailing whitespace contains any newlines.
 
 So the complete syntax is:
 
 ```
    string       : '"' string_item '"'
-   string_item  : string_char | char_escape | string_gap
-   string_char  : [^"\\]
-   char_escape  : "\" ("\" | '"' | "'" | "n" | "t" | "x" hex_char{2} | "u" hex_char{4})
+   string_item  : string_char | string_escape
+   string_char  : [^\\]
+   string_escape: "\" ("\" | '"' | "'" | "n" | "t" | "x" hex_char{2} | "u" hex_char{4} )
    hex_char     : [0-9a-fA-F]
-   string_gap   : "\" newline whitespace*
-```
-
-Raw String Literals
-===================
-
-Raw string literals are string literals without any escape character processing.
-They begin with `r##...#"` (with zero or more `#` characters) and end with `"#...##` (with the same number of `#` characters).
-The contents of a raw string literal may contain `"##..#` so long as the number of `#` characters
-is less than the number of `#` characters used to begin the raw string literal.
-
-```
-   raw_string          : raw_string_aux(0) | raw_string_aux(1) | raw_string_aux(2) | ...
-   raw_string_aux(n)   : 'r' '#'{n} '"' raw_string_item '"' '#'{n}
-   raw_string_item(n)  : raw_string_char | raw_string_quote(n)
-   raw_string_char     : [^"]
-   raw_string_quote(n) : '"' '#'{0..n-1}
 ```
 
 Char Literals
@@ -116,9 +96,7 @@ Char Literals
 Char literals are enclosed by single quotes (``'``).
 
 ```
-   char      : "'" char_item "'"
-   char_item : char_char | char_escape
-   char_char : [^'\\]
+   char: "'" string_item "'"
 ```
 
 Numeric Literals

doc/make/index.md

@@ -10,9 +10,12 @@ Platform-Specific Setup
 
 - [Linux (Ubuntu)](ubuntu.md)
 - [Windows (msys2)](msys2.md)
+- [Windows (Visual Studio)](msvc.md)
 - [Windows (WSL)](wsl.md)
 - [macOS (homebrew)](osx-10.9.md)
 - Linux/macOS/WSL via [Nix](https://nixos.org/nix/): Call `nix-shell` in the project root. That's it.
+- There is also an [**experimental** setup based purely on Nix](nix.md) that works fundamentally differently from the
+  make/CMake setup described on this page.
 
 Generic Build Instructions
 --------------------------

doc/make/nix.md

@@ -0,0 +1,110 @@
+# Building with Nix
+
+While [Nix](https://nixos.org/nix/) can be used to quickly open a shell with all dependencies for the [standard setup](index.md) installed, the user-facing [Nix Setup](../setup.md#nix-setup) can also be used to work *on* Lean.
+
+## Setup
+
+Follow the setup in the link above; to open the Lean shell inside a Lean checkout, you can also use
+```bash
+# in the Lean root directory
+$ nix-shell -A nix
+```
+
+On top of the local and remote Nix cache, we do still rely on CCache as well to make C/C++ build steps incremental, which are atomic steps from Nix's point of view.
+To enable CCache, add the following line to the config file mentioned in the setup:
+```bash
+extra-sandbox-paths = /nix/var/cache/ccache
+```
+Then set up that directory as follows:
+```bash
+sudo mkdir -m0770 -p /nix/var/cache/ccache
+# macOS standard chown doesn't support --reference
+nix shell .#nixpkgs.coreutils -c sudo chown --reference=/nix/store /nix/var/cache/ccache
+```
+
+## Basic Build Commands
+
+From the Lean root directory inside the Lean shell:
+```bash
+nix build .#stage1  # build this stage's stdlib & executable
+nix build .#stage1.test  # run all tests
+nix run .#stage1.update-stage0  # update ./stage0 from this stage
+nix run .#stage1.update-stage0-commit  # ...and commit the results
+```
+The `stage1.` part in each command is optional:
+```bash
+nix build .#test  # run tests for stage 1
+nix build .  # build stage 1
+nix build  # ditto
+```
+
+## Build Process Description
+
+The Nix build process conceptually works the same as described in [Lean Build Pipeline](index.md#lean-build-pipeline).
+However, there are two important differences in practice apart from the standard Nix properties (hermeneutic, reproducible builds stored in a global hash-indexed store etc.):
+* Only files tracked by git (using `git add` or at least `git add --intent-to-add`) are compiled.
+This is actually a general property of Nix flakes, and has the benefit of making it basically impossible to forget to commit a file (at least in `src/`).
+* Only files reachable from `src/Lean.lean` are compiled.
+This is because modules are discovered not from a directory listing anymore but by recursively compiling all dependencies of that top module.
+
+## Editor Integration
+
+As in the standard Nix setup.
+After adding `src/` as an LSP workspace, it should automatically fall back to using stage 0 in there.
+
+Note that the UX of `{emacs,vscode}-dev` is quite different from the Make-based setup regarding the compilation of dependencies:
+there is no mutable directory incrementally filled by the build that we could point the editor at for .olean files.
+Instead, `emacs-dev` will gather the individual dependency outputs from the Nix store when checking a file -- and build them on the fly when necessary.
+However, it will only ever load changes saved to disk, not ones opened in other buffers.
+
+The absence of a mutable output directory also means that the Lean server will not automatically pick up `.ilean` metadata from newly compiled files.
+Instead, you can run `nix run .#link-ilean` to symlink the `.ilean` tree of the stdlib state at that point in time to `src/build/lib`, where the server should automatically find them.
+
+## Other Fun Stuff to Do with Nix
+
+Open Emacs with Lean set up from an arbitrary commit (without even cloning Lean beforehand... if your Nix is new enough):
+```bash
+nix run github:leanprover/lean4/7e4edeb#emacs-package
+```
+
+Open a shell with `lean` and `LEAN_PATH` set up for compiling a specific module (this is exactly what `emacs-dev` is doing internally):
+```bash
+nix develop .#mods.\"Lean.Parser.Basic\"
+# alternatively, directly pass a command to execute:
+nix develop .#stage2.mods.\"Init.Control.Basic\" -c bash -c 'lean $src -Dtrace.Elab.command=true'
+```
+
+Not sure what you just broke? Run Lean from (e.g.) the previous commit on a file:
+```bash
+nix run .\?rev=$(git rev-parse @^) scratch.lean
+```
+
+Work on two adjacent stages at the same time without the need for repeatedly updating and reverting `stage0/`:
+```bash
+# open an editor that will use only committed changes (so first commit them when changing files)
+nix run .#HEAD-as-stage1.emacs-dev&
+# open a second editor that will use those committed changes as stage 0
+# (so don't commit changes done here until you are done and ran a final `update-stage0-commit`)
+nix run .#HEAD-as-stage0.emacs-dev&
+```
+To run `nix build` on the second stage outside of the second editor, use
+```bash
+nix build .#stage0-from-input --override-input lean-stage0 .\?rev=$(git rev-parse HEAD)
+```
+This setup will inadvertently change your `flake.lock` file, which you can revert when you are done.
+
+...more surely to come...
+
+## Debugging
+
+Since Nix copies all source files before compilation, you will need to map debug symbols back to the original path using `set substitute-path` in GDB.
+For example, for a build on Linux with the Nix sandbox activated:
+```bash
+(gdb) f
+#1  0x0000000000d23a4f in lean_inc (o=0x1) at /build/source/build/include/lean/lean.h:562
+562	/build/source/build/include/lean/lean.h: No such file or directory.
+(gdb) set substitute-path /build/source/build src
+(gdb) f
+#1  0x0000000000d23a4f in lean_inc (o=0x1) at /build/source/build/include/lean/lean.h:562
+562	static inline void lean_inc(lean_object * o) { if (!lean_is_scalar(o)) lean_inc_ref(o); }
+```

doc/metaprogramming-arith.md

@@ -60,7 +60,7 @@ While parsing `a * (b + c)`, `(b + c)` is assigned a precedence `60` by the addi
 the right argument to have precedence **at least** 71. Thus, this parse is invalid. In contrast, `(a * b) + c` assigns
 a precedence of `70` to `(a * b)`. This is compatible with addition which expects the left argument to have precedence
 **at least `60` ** (`70` is greater than `60`). Thus, the string `a * b + c` is parsed as `(a * b) + c`.
-For more details, please look at the [Lean manual on syntax extensions](./notation.md#notations-and-precedence).
+For more details, please look at the [Lean manual on syntax extensions](../syntax.md#notations-and-precedence).
 
 To go from strings into `Arith`, we define a macro to
 translate the syntax category `arith` into an `Arith` inductive value that

doc/quickstart.md

@@ -1,18 +1,55 @@
 # Quickstart
 
-These instructions will walk you through setting up Lean 4 together with VS Code as an editor for Lean 4.
-See [Setup](./setup.md) for supported platforms and other ways to set up Lean 4.
+These instructions will walk you through setting up Lean using the "basic" setup and VS Code as the editor.
+See [Setup](./setup.md) for other ways, supported platforms, and more details on setting up Lean.
+
+See quick [walkthrough demo video](https://www.youtube.com/watch?v=yZo6k48L0VY).
 
 1. Install [VS Code](https://code.visualstudio.com/).
 
-1. Launch VS Code and install the `lean4` extension by clicking on the "Extensions" sidebar entry and searching for "lean4".
+1. Launch VS Code and install the `lean4` extension.
 
     ![installing the vscode-lean4 extension](images/code-ext.png)
 
-1. Open the Lean 4 setup guide by creating a new text file using "File > New Text File" (`Ctrl+N`), clicking on the ∀-symbol in the top right and selecting "Documentation… > Setup: Show Setup Guide".
+1. Create a new file using "File > New Text File" (`Ctrl+N`). Click the `Select a language` prompt, type in `lean4`, and hit ENTER.  You should see the following popup:
+    ![elan](images/install_elan.png)
 
-    ![show setup guide](images/show-setup-guide.png)
+    Click the "Install Lean using Elan" button. You should see some progress output like this:
 
-1. Follow the Lean 4 setup guide. It will walk you through learning resources for Lean 4, teach you how to set up Lean's dependencies on your platform, install Lean 4 for you at the click of a button and help you set up your first project.
+    ```
+    info: syncing channel updates for 'stable'
+    info: latest update on stable, lean version v4.0.0
+    info: downloading component 'lean'
+    ```
+    If there is no popup, you probably have Elan installed already.
+    You may want to make sure that your default toolchain is Lean 4 in this case by running `elan default leanprover/lean4:stable` and reopen the file, as the next step will fail otherwise.
 
-    ![setup guide](images/setup_guide.png)
+1. While it is installing, you can paste the following Lean program into the new file:
+
+    ```lean
+    #eval Lean.versionString
+    ```
+
+    When the installation has finished, the Lean Language Server should start automatically and you should get syntax-highlighting and a "Lean Infoview" popping up on the right.  You will see the output of the `#eval` statement when
+    you place your cursor at the end of the statement.
+
+    ![successful setup](images/code-success.png)
+
+You are set up!
+
+## Create a Lean Project
+
+*If your goal is to contribute to [mathlib4](https://github.com/leanprover-community/mathlib4) or use it as a dependency, please see its readme for specific instructions on how to do that.*
+
+You can now create a Lean project in a new folder. Run `lake init foo` from "View > Terminal" to create a package, followed by `lake build` to get an executable version of your Lean program.
+On Linux/macOS, you first have to follow the instructions printed by the Lean installation or log out and in again for the Lean executables to be available in you terminal.
+
+Note: Packages **have** to be opened using "File > Open Folder..." for imports to work.
+Saved changes are visible in other files after running "Lean 4: Refresh File Dependencies" (`Ctrl+Shift+X`).
+
+## Troubleshooting
+
+**The InfoView says "Waiting for Lean server to start..." forever.**
+
+Check that the VS Code Terminal is not showing some installation errors from `elan`.
+If that doesn't work, try also running the VS Code command `Developer: Reload Window`.

doc/setup.md

@@ -2,7 +2,7 @@
 
 ### Tier 1
 
-Platforms built & tested by our CI, available as binary releases via elan (see below)
+Platforms built & tested by our CI, available as nightly releases via elan (see below)
 
 * x86-64 Linux with glibc 2.27+
 * x86-64 macOS 10.15+
@@ -10,7 +10,7 @@ Platforms built & tested by our CI, available as binary releases via elan (see b
 
 ### Tier 2
 
-Platforms cross-compiled but not tested by our CI, available as binary releases
+Platforms cross-compiled but not tested by our CI, available as nightly releases
 
 Releases may be silently broken due to the lack of automated testing.
 Issue reports and fixes are welcome.
@@ -50,10 +50,10 @@ Foo.lean       # main file, import via `import Foo`
 Foo/
   A.lean       # further files, import via e.g. `import Foo.A`
   A/...        # further nesting
-.lake/         # `lake` build output directory
+build/         # `lake` build output directory
 ```
 
-After running `lake build` you will see a binary named `./.lake/build/bin/foo` and when you run it you should see the output:
+After running `lake build` you will see a binary named `./build/bin/foo` and when you run it you should see the output:
 ```
 Hello, world!
 ```

doc/setup/nix.md

@@ -0,0 +1,71 @@
+# Nix Setup
+
+An alternative setup based on Nix provides a perfectly reproducible development environment for your project from the Lean version down to the editor and Lean extension.
+However, it is still experimental and subject to change; in particular, it is heavily based on an unreleased version of Nix enabling [Nix Flakes](https://www.tweag.io/blog/2020-05-25-flakes/). The setup has been tested on NixOS, other Linux distributions, and macOS.
+
+After installing (any version of) Nix (<https://nixos.org/download.html>), you can easily open a shell with the particular pre-release version of Nix needed by and tested with our setup (called the "Lean shell" from here on):
+```bash
+$ nix-shell https://github.com/leanprover/lean4/archive/master.tar.gz -A nix
+```
+While this shell is sufficient for executing the steps below, it is recommended to also set the following options in `/etc/nix/nix.conf` (`nix.extraOptions` in NixOS):
+```
+max-jobs = auto  # Allow building multiple derivations in parallel
+keep-outputs = true  # Do not garbage-collect build time-only dependencies (e.g. clang)
+# Allow fetching build results from the Lean Cachix cache
+trusted-substituters = https://lean4.cachix.org/
+trusted-public-keys = cache.nixos.org-1:6NCHdD59X431o0gWypbMrAURkbJ16ZPMQFGspcDShjY= lean4.cachix.org-1:mawtxSxcaiWE24xCXXgh3qnvlTkyU7evRRnGeAhD4Wk=
+```
+On a multi-user installation of Nix (the default), you need to restart the Nix daemon afterwards:
+```bash
+sudo pkill nix-daemon
+```
+
+The [Cachix](https://cachix.org/) integration will magically beam any build steps already executed by the CI right onto your machine when calling Nix commands in the shell opened above.
+It can be set up analogously as a cache for your own project.
+
+Note: Your system Nix might print warnings about not knowing some of the settings used by the Lean shell Nix, which can be ignored.
+
+## Basic Commands
+
+From a Lean shell, run
+```bash
+$ nix flake new mypkg -t github:leanprover/lean4
+```
+to create a new Lean package in directory `mypkg` using the latest commit of Lean 4.
+Such packages follow the same directory layout as described in the standard setup, except for a `lakefile.lean` replaced by a `flake.nix` file set up so you can run Nix commands on it, for example:
+```bash
+$ nix build  # build package and all dependencies
+$ nix build .#executable  # compile `main` definition into executable (after you've added one)
+$ nix run .#emacs-dev  # open a pinned version of Emacs with lean4-mode fully set up
+$ nix run .#emacs-dev MyPackage.lean  # arguments can be passed as well, e.g. the file to open
+$ nix run .#vscode-dev MyPackage.lean  # ditto, using VS Code
+```
+Note that if you rename `MyPackage.lean`, you also have to adjust the `name` attribute in `flake.nix` accordingly.
+Also note that if you turn the package into a Git repository, only tracked files will be visible to Nix.
+
+As in the standard setup, changes need to be saved to be visible in other files, which have then to be invalidated via an editor command.
+
+If you don't want to or cannot start the pinned editor from Nix, e.g. because you're running Lean inside WSL/a container/on a different machine, you can manually point your editor at the `lean` wrapper script the commands above use internally:
+```bash
+$ nix build .#lean-dev -o result-lean-dev
+```
+The resulting `./result-lean-dev/bin/lean` script essentially runs `nix run .#lean` in the current project's root directory when you open a Lean file or use the "refresh dependencies" command such that the correct Lean version for that project is executed.
+This includes selecting the correct stage of Lean (which it will compile on the fly, though without progress output) if you are [working on Lean itself](./make/nix.md#editor-integration).
+
+Package dependencies can be added as further input flakes and passed to the `deps` list of `buildLeanPackage`. Example: <https://github.com/Kha/testpkg2/blob/master/flake.nix#L5>
+
+For hacking, it can be useful to temporarily override an input with a local checkout/different version of a dependency:
+```bash
+$ nix build --override-input somedep path/to/somedep
+```
+
+On a build error, Nix will show the last 10 lines of the output by default. You can pass `-L` to `nix build` to show all lines, or pass the shown `*.drv` path to `nix log` to show the full log after the fact.
+
+Keeping all outputs ever built on a machine alive can accumulate to quite impressive amounts of disk space, so you might want to trigger the Nix GC when `/nix/store/` has grown too large:
+```bash
+nix-collect-garbage
+```
+This will remove everything not reachable from "GC roots" such as the `./result` symlink created by `nix build`.
+
+Note that the package information in `flake.nix` is currently completely independent from `lakefile.lean` used in the standard setup.
+Unifying the two formats is TBD.

doc/syntax_highlight_in_latex.md

@@ -67,9 +67,6 @@ theorem funext {f₁ f₂ : ∀ (x : α), β x} (h : ∀ x, f₁ x = f₂ x) : f
 \end{document}
 ```
 
-If your version of `minted` is v2.7 or newer, but before v3.0,
-you will additionally need to follow the workaround described in https://github.com/gpoore/minted/issues/360.
-
 You can then compile `test.tex` by executing the following command:
 
 ```bash

doc/tour.md

@@ -15,7 +15,7 @@ The most fundamental pieces of any Lean program are functions organized into nam
 [Functions](./functions.md) perform work on inputs to produce outputs,
 and they are organized under [namespaces](./namespaces.md),
 which are the primary way you group things in Lean.
-They are defined using the `def` command,
+They are defined using the [`def`](./definitions.md) command,
 which give the function a name and define its arguments.
 
 ```lean

doc/typeclass.md

@@ -99,11 +99,11 @@ Let us start with the first step of the program above, declaring an appropriate
 
 ```lean
 # namespace Ex
-class Inhabited (a : Sort u) where
+class Inhabited (a : Type u) where
   default : a
 
 #check @Inhabited.default
--- Inhabited.default : {a : Sort u} → [self : Inhabited a] → a
+-- Inhabited.default : {a : Type u} → [self : Inhabited a] → a
 # end Ex
 ```
 Note `Inhabited.default` doesn't have any explicit argument.
@@ -114,7 +114,7 @@ Now we populate the class with some instances:
 
 ```lean
 # namespace Ex
-# class Inhabited (a : Sort _) where
+# class Inhabited (a : Type _) where
 #  default : a
 instance : Inhabited Bool where
   default := true
@@ -138,7 +138,7 @@ instance : Inhabited Prop where
 You can use the command `export` to create the alias `default` for `Inhabited.default`
 ```lean
 # namespace Ex
-# class Inhabited (a : Sort _) where
+# class Inhabited (a : Type _) where
 #  default : a
 # instance : Inhabited Bool where
 #  default := true
@@ -174,7 +174,7 @@ instance [Inhabited a] [Inhabited b] : Inhabited (a × b) where
 With this added to the earlier instance declarations, type class instance can infer, for example, a default element of ``Nat × Bool``:
 ```lean
 # namespace Ex
-# class Inhabited (a : Sort u) where
+# class Inhabited (a : Type u) where
 #  default : a
 # instance : Inhabited Bool where
 #  default := true
@@ -191,14 +191,8 @@ instance [Inhabited a] [Inhabited b] : Inhabited (a × b) where
 ```
 Similarly, we can inhabit type function with suitable constant functions:
 ```lean
-# namespace Ex
-# class Inhabited (a : Sort u) where
-#  default : a
-# opaque default [Inhabited a] : a :=
-#  Inhabited.default
 instance [Inhabited b] : Inhabited (a -> b) where
   default := fun _ => default
-# end Ex
 ```
 As an exercise, try defining default instances for other types, such as `List` and `Sum` types.
 

doc/whatIsLean.md

@@ -37,6 +37,6 @@ Lean has numerous features, including:
 - [Extensible syntax](./syntax.md)
 - Hygienic macros
 - [Dependent types](https://lean-lang.org/theorem_proving_in_lean4/dependent_type_theory.html)
-- [Metaprogramming](./macro_overview.md)
+- [Metaprogramming](./metaprogramming.md)
 - Multithreading
 - Verification: you can prove properties of your functions using Lean itself

lean.code-workspace

@@ -13,8 +13,6 @@
 	"settings": {
 		"files.insertFinalNewline": true,
 		"files.trimTrailingWhitespace": true,
-		"cmake.buildDirectory": "${workspaceFolder}/build/release",
-		"cmake.generator": "Unix Makefiles",
 		"[markdown]": {
 			"rewrap.wrappingColumn": 70
 		},
@@ -48,10 +46,5 @@
 				}
 			}
 		]
-	},
-	"extensions": {
-		"recommendations": [
-			"leanprover.lean4"
-		]
 	}
 }

nix/bootstrap.nix

@@ -83,13 +83,13 @@ rec {
         # use same stage for retrieving dependencies
         lean-leanDeps = stage0;
         lean-final = self;
+        leanFlags = [ "-DwarningAsError=true" ];
       } ({
         src = src + "/src";
         roots = [ { mod = args.name; glob = "andSubmodules"; } ];
         fullSrc = src;
         srcPath = "$PWD/src:$PWD/src/lake";
         inherit debug;
-        leanFlags = [ "-DwarningAsError=true" ];
       } // args);
       Init' = build { name = "Init"; deps = []; };
       Lean' = build { name = "Lean"; deps = [ Init' ]; };

script/most-recent-nightly-tag.sh

@@ -0,0 +1,16 @@
+#!/bin/bash
+
+# Prefix for tags to search for
+tag_prefix="nightly-"
+
+# Fetch all tags from the remote repository
+git fetch https://github.com/leanprover/lean4-nightly.git --tags > /dev/null
+
+# Get the most recent commit that has a matching tag
+tag_name=$(git tag --merged HEAD --list "${tag_prefix}*" | sort -rV | head -n 1 | sed "s/^$tag_prefix//")
+
+if [ -z "$tag_name" ]; then
+    exit 1
+fi
+
+echo "$tag_name"

src/CMakeLists.txt

@@ -9,7 +9,7 @@ endif()
 include(ExternalProject)
 project(LEAN CXX C)
 set(LEAN_VERSION_MAJOR 4)
-set(LEAN_VERSION_MINOR 7)
+set(LEAN_VERSION_MINOR 5)
 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'")
@@ -18,14 +18,6 @@ if (LEAN_SPECIAL_VERSION_DESC)
   string(APPEND LEAN_VERSION_STRING "-${LEAN_SPECIAL_VERSION_DESC}")
 endif()
 
-set(LEAN_PLATFORM_TARGET "" CACHE STRING "LLVM triple of the target platform")
-if (NOT LEAN_PLATFORM_TARGET)
-  # this may fail when the compiler is not clang, but this should only happen in local builds where
-  # the value of the variable is not of immediate relevance
-  execute_process(COMMAND ${CMAKE_C_COMPILER} --print-target-triple
-    OUTPUT_VARIABLE LEAN_PLATFORM_TARGET OUTPUT_STRIP_TRAILING_WHITESPACE)
-endif()
-
 set(LEAN_EXTRA_LINKER_FLAGS "" CACHE STRING "Additional flags used by the linker")
 set(LEAN_EXTRA_CXX_FLAGS "" CACHE STRING "Additional flags used by the C++ compiler")
 set(LEAN_TEST_VARS "LEAN_CC=${CMAKE_C_COMPILER}" CACHE STRING "Additional environment variables used when running tests")

src/Init.lean

@@ -23,5 +23,4 @@ import Init.NotationExtra
 import Init.SimpLemmas
 import Init.Hints
 import Init.Conv
-import Init.Simproc
 import Init.SizeOfLemmas

src/Init/Classical.lean

@@ -22,7 +22,7 @@ noncomputable def choose {α : Sort u} {p : α → Prop} (h : ∃ x, p x) : α :
 theorem choose_spec {α : Sort u} {p : α → Prop} (h : ∃ x, p x) : p (choose h) :=
   (indefiniteDescription p h).property
 
-/-- **Diaconescu's theorem**: excluded middle from choice, Function extensionality and propositional extensionality. -/
+/-- Diaconescu's theorem: excluded middle from choice, Function extensionality and propositional extensionality. -/
 theorem em (p : Prop) : p ∨ ¬p :=
   let U (x : Prop) : Prop := x = True ∨ p
   let V (x : Prop) : Prop := x = False ∨ p

src/Init/Core.lean

@@ -411,10 +411,9 @@ set_option linter.unusedVariables.funArgs false in
 be available and then calls `f` on the result.
 
 `prio`, if provided, is the priority of the task.
-If `sync` is set to true, `f` is executed on the current thread if `x` has already finished.
 -/
 @[noinline, extern "lean_task_map"]
-protected def map (f : α → β) (x : Task α) (prio := Priority.default) (sync := false) : Task β :=
+protected def map {α : Type u} {β : Type v} (f : α → β) (x : Task α) (prio := Priority.default) : Task β :=
   ⟨f x.get⟩
 
 set_option linter.unusedVariables.funArgs false in
@@ -425,11 +424,9 @@ for the value of `x` to be available and then calls `f` on the result,
 resulting in a new task which is then run for a result.
 
 `prio`, if provided, is the priority of the task.
-If `sync` is set to true, `f` is executed on the current thread if `x` has already finished.
 -/
 @[noinline, extern "lean_task_bind"]
-protected def bind (x : Task α) (f : α → Task β) (prio := Priority.default) (sync := false) :
-    Task β :=
+protected def bind {α : Type u} {β : Type v} (x : Task α) (f : α → Task β) (prio := Priority.default) : Task β :=
   ⟨(f x.get).get⟩
 
 end Task
@@ -1683,92 +1680,40 @@ So, you are mainly losing the capability of type checking your development using
 -/
 axiom ofReduceNat (a b : Nat) (h : reduceNat a = b) : a = b
 
-end Lean
-
-namespace Std
-variable {α : Sort u}
-
 /--
-`Associative op` indicates `op` is an associative operation,
-i.e. `(a ∘ b) ∘ c = a ∘ (b ∘ c)`.
+`IsAssociative op` says that `op` is an associative operation,
+i.e. `(a ∘ b) ∘ c = a ∘ (b ∘ c)`. It is used by the `ac_rfl` tactic.
 -/
-class Associative (op : α → α → α) : Prop where
+class IsAssociative {α : Sort u} (op : α → α → α) where
   /-- An associative operation satisfies `(a ∘ b) ∘ c = a ∘ (b ∘ c)`. -/
   assoc : (a b c : α) → op (op a b) c = op a (op b c)
 
 /--
-`Commutative op` says that `op` is a commutative operation,
-i.e. `a ∘ b = b ∘ a`.
+`IsCommutative op` says that `op` is a commutative operation,
+i.e. `a ∘ b = b ∘ a`. It is used by the `ac_rfl` tactic.
 -/
-class Commutative (op : α → α → α) : Prop where
+class IsCommutative {α : Sort u} (op : α → α → α) where
   /-- A commutative operation satisfies `a ∘ b = b ∘ a`. -/
   comm : (a b : α) → op a b = op b a
 
 /--
-`IdempotentOp op` indicates `op` is an idempotent binary operation.
-i.e. `a ∘ a = a`.
+`IsIdempotent op` says that `op` is an idempotent operation,
+i.e. `a ∘ a = a`. It is used by the `ac_rfl` tactic
+(which also simplifies up to idempotence when available).
 -/
-class IdempotentOp (op : α → α → α) : Prop where
+class IsIdempotent {α : Sort u} (op : α → α → α) where
   /-- An idempotent operation satisfies `a ∘ a = a`. -/
   idempotent : (x : α) → op x x = x
 
 /--
-`LeftIdentify op o` indicates `o` is a left identity of `op`.
-
-This class does not require a proof that `o` is an identity, and
-is used primarily for infering the identity using class resoluton.
+`IsNeutral op e` says that `e` is a neutral operation for `op`,
+i.e. `a ∘ e = a = e ∘ a`. It is used by the `ac_rfl` tactic
+(which also simplifies neutral elements when available).
 -/
-class LeftIdentity (op : α → β → β) (o : outParam α) : Prop
+class IsNeutral {α : Sort u} (op : α → α → α) (neutral : α) where
+  /-- A neutral element can be cancelled on the left: `e ∘ a = a`. -/
+  left_neutral : (a : α) → op neutral a = a
+  /-- A neutral element can be cancelled on the right: `a ∘ e = a`. -/
+  right_neutral : (a : α) → op a neutral = a
 
-/--
-`LawfulLeftIdentify op o` indicates `o` is a verified left identity of
-`op`.
--/
-class LawfulLeftIdentity (op : α → β → β) (o : outParam α) extends LeftIdentity op o : Prop where
-  /-- Left identity `o` is an identity. -/
-  left_id : ∀ a, op o a = a
-
-/--
-`RightIdentify op o` indicates `o` is a right identity `o` of `op`.
-
-This class does not require a proof that `o` is an identity, and is used
-primarily for infering the identity using class resoluton.
--/
-class RightIdentity (op : α → β → α) (o : outParam β) : Prop
-
-/--
-`LawfulRightIdentify op o` indicates `o` is a verified right identity of
-`op`.
--/
-class LawfulRightIdentity (op : α → β → α) (o : outParam β) extends RightIdentity op o : Prop where
-  /-- Right identity `o` is an identity. -/
-  right_id : ∀ a, op a o = a
-
-/--
-`Identity op o` indicates `o` is a left and right identity of `op`.
-
-This class does not require a proof that `o` is an identity, and is used
-primarily for infering the identity using class resoluton.
--/
-class Identity (op : α → α → α) (o : outParam α) extends LeftIdentity op o, RightIdentity op o : Prop
-
-/--
-`LawfulIdentity op o` indicates `o` is a verified left and right
-identity of `op`.
--/
-class LawfulIdentity (op : α → α → α) (o : outParam α) extends Identity op o, LawfulLeftIdentity op o, LawfulRightIdentity op o : Prop
-
-/--
-`LawfulCommIdentity` can simplify defining instances of `LawfulIdentity`
-on commutative functions by requiring only a left or right identity
-proof.
-
-This class is intended for simplifying defining instances of
-`LawfulIdentity` and functions needed commutative operations with
-identity should just add a `LawfulIdentity` constraint.
--/
-class LawfulCommIdentity (op : α → α → α) (o : outParam α) [hc : Commutative op] extends LawfulIdentity op o : Prop where
-  left_id a := Eq.trans (hc.comm o a) (right_id a)
-  right_id a := Eq.trans (hc.comm a o) (left_id a)
-
-end Std
+end Lean

src/Init/Data/AC.lean

@@ -14,17 +14,15 @@ inductive Expr
   | op (lhs rhs : Expr)
   deriving Inhabited, Repr, BEq
 
-open Std
-
 structure Variable {α : Sort u} (op : α → α → α) : Type u where
   value : α
-  neutral : Option $ PLift (LawfulIdentity op value)
+  neutral : Option $ IsNeutral op value
 
 structure Context (α : Sort u) where
   op : α → α → α
-  assoc : Associative op
-  comm : Option $ PLift $ Commutative op
-  idem : Option $ PLift $ IdempotentOp op
+  assoc : IsAssociative op
+  comm : Option $ IsCommutative op
+  idem : Option $ IsIdempotent op
   vars : List (Variable op)
   arbitrary : α
 
@@ -130,14 +128,7 @@ theorem Context.mergeIdem_head2 (h : x ≠ y) : mergeIdem (x :: y :: ys) = x ::
   simp [mergeIdem, mergeIdem.loop, h]
 
 theorem Context.evalList_mergeIdem (ctx : Context α) (h : ContextInformation.isIdem ctx) (e : List Nat) : evalList α ctx (mergeIdem e) = evalList α ctx e := by
-  have h : IdempotentOp ctx.op := by
-    simp [ContextInformation.isIdem, Option.isSome] at h;
-    match h₂ : ctx.idem with
-    | none =>
-      simp [h₂] at h
-    | some val =>
-      simp [h₂] at h
-      exact val.down
+  have h : IsIdempotent ctx.op := by simp [ContextInformation.isIdem, Option.isSome] at h; cases h₂ : ctx.idem <;> simp [h₂] at h; assumption
   induction e using List.two_step_induction with
   | empty => rfl
   | single => rfl
@@ -178,7 +169,7 @@ theorem Context.sort_loop_nonEmpty (xs : List Nat) (h : xs ≠ []) : sort.loop x
 
 theorem Context.evalList_insert
   (ctx : Context α)
-  (h : Commutative ctx.op)
+  (h : IsCommutative ctx.op)
   (x : Nat)
   (xs : List Nat)
   : evalList α ctx (insert x xs) = evalList α ctx (x::xs) := by
@@ -199,7 +190,7 @@ theorem Context.evalList_insert
 
 theorem Context.evalList_sort_congr
   (ctx : Context α)
-  (h : Commutative ctx.op)
+  (h : IsCommutative ctx.op)
   (h₂ : evalList α ctx a = evalList α ctx b)
   (h₃ : a ≠ [])
   (h₄ : b ≠ [])
@@ -218,7 +209,7 @@ theorem Context.evalList_sort_congr
 
 theorem Context.evalList_sort_loop_swap
   (ctx : Context α)
-  (h : Commutative ctx.op)
+  (h : IsCommutative ctx.op)
   (xs ys : List Nat)
   : evalList α ctx (sort.loop xs (y::ys)) = evalList α ctx (sort.loop (y::xs) ys) := by
   induction ys generalizing y xs with
@@ -233,7 +224,7 @@ theorem Context.evalList_sort_loop_swap
 
 theorem Context.evalList_sort_cons
   (ctx : Context α)
-  (h : Commutative ctx.op)
+  (h : IsCommutative ctx.op)
   (x : Nat)
   (xs : List Nat)
   : evalList α ctx (sort (x :: xs)) = evalList α ctx (x :: sort xs) := by
@@ -256,14 +247,7 @@ theorem Context.evalList_sort_cons
     all_goals simp [insert_nonEmpty]
 
 theorem Context.evalList_sort (ctx : Context α) (h : ContextInformation.isComm ctx) (e : List Nat) : evalList α ctx (sort e) = evalList α ctx e := by
-  have h : Commutative ctx.op := by
-    simp [ContextInformation.isComm, Option.isSome] at h
-    match h₂ : ctx.comm with
-    | none =>
-      simp only [h₂] at h
-    | some val =>
-      simp [h₂] at h
-      exact val.down
+  have h : IsCommutative ctx.op := by simp [ContextInformation.isComm, Option.isSome] at h; cases h₂ : ctx.comm <;> simp [h₂] at h; assumption
   induction e using List.two_step_induction with
   | empty => rfl
   | single => rfl
@@ -285,12 +269,10 @@ theorem Context.toList_nonEmpty (e : Expr) : e.toList ≠ [] := by
 theorem Context.unwrap_isNeutral
   {ctx : Context α}
   {x : Nat}
-  : ContextInformation.isNeutral ctx x = true → LawfulIdentity (EvalInformation.evalOp ctx) (EvalInformation.evalVar (β := α) ctx x) := by
+  : ContextInformation.isNeutral ctx x = true → IsNeutral (EvalInformation.evalOp ctx) (EvalInformation.evalVar (β := α) ctx x) := by
   simp [ContextInformation.isNeutral, Option.isSome, EvalInformation.evalOp, EvalInformation.evalVar]
   match (var ctx x).neutral with
-  | some hn =>
-    intro
-    exact hn.down
+  | some hn => intro; assumption
   | none => intro; contradiction
 
 theorem Context.evalList_removeNeutrals (ctx : Context α) (e : List Nat) : evalList α ctx (removeNeutrals ctx e) = evalList α ctx e := by
@@ -301,12 +283,10 @@ theorem Context.evalList_removeNeutrals (ctx : Context α) (e : List Nat) : eval
     case h_1 => rfl
     case h_2 h => split at h <;> simp_all
   | step x y ys ih =>
-    cases h₁ : ContextInformation.isNeutral ctx x <;>
-    cases h₂ : ContextInformation.isNeutral ctx y <;>
-    cases h₃ : removeNeutrals.loop ctx ys
+    cases h₁ : ContextInformation.isNeutral ctx x <;> cases h₂ : ContextInformation.isNeutral ctx y <;> cases h₃ : removeNeutrals.loop ctx ys
     <;> simp [removeNeutrals, removeNeutrals.loop, h₁, h₂, h₃, evalList, ←ih]
-    <;> (try simp [unwrap_isNeutral h₂ |>.right_id])
-    <;> (try simp [unwrap_isNeutral h₁ |>.left_id])
+    <;> (try simp [unwrap_isNeutral h₂ |>.2])
+    <;> (try simp [unwrap_isNeutral h₁ |>.1])
 
 theorem Context.evalList_append
   (ctx : Context α)

src/Init/Data/Array/Basic.lean

@@ -21,21 +21,6 @@ def mkArray {α : Type u} (n : Nat) (v : α) : Array α := {
   data := List.replicate n v
 }
 
-/--
-`ofFn f` with `f : Fin n → α` returns the list whose ith element is `f i`.
-```
-ofFn f = #[f 0, f 1, ... , f(n - 1)]
-``` -/
-def ofFn {n} (f : Fin n → α) : Array α := go 0 (mkEmpty n) where
-  /-- Auxiliary for `ofFn`. `ofFn.go f i acc = acc ++ #[f i, ..., f(n - 1)]` -/
-  go (i : Nat) (acc : Array α) : Array α :=
-    if h : i < n then go (i+1) (acc.push (f ⟨i, h⟩)) else acc
-termination_by n - i
-
-/-- The array `#[0, 1, ..., n - 1]`. -/
-def range (n : Nat) : Array Nat :=
-  n.fold (flip Array.push) (mkEmpty n)
-
 @[simp] theorem size_mkArray (n : Nat) (v : α) : (mkArray n v).size = n :=
   List.length_replicate ..
 
@@ -86,12 +71,6 @@ abbrev getLit {α : Type u} {n : Nat} (a : Array α) (i : Nat) (h₁ : a.size =
 def uset (a : Array α) (i : USize) (v : α) (h : i.toNat < a.size) : Array α :=
   a.set ⟨i.toNat, h⟩ v
 
-/--
-Swaps two entries in an array.
-
-This will perform the update destructively provided that `a` has a reference
-count of 1 when called.
--/
 @[extern "lean_array_fswap"]
 def swap (a : Array α) (i j : @& Fin a.size) : Array α :=
   let v₁ := a.get i
@@ -99,18 +78,12 @@ def swap (a : Array α) (i j : @& Fin a.size) : Array α :=
   let a'  := a.set i v₂
   a'.set (size_set a i v₂ ▸ j) v₁
 
-/--
-Swaps two entries in an array, or panics if either 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_swap"]
 def swap! (a : Array α) (i j : @& Nat) : Array α :=
   if h₁ : i < a.size then
   if h₂ : j < a.size then swap a ⟨i, h₁⟩ ⟨j, h₂⟩
-  else a
-  else a
+  else panic! "index out of bounds"
+  else panic! "index out of bounds"
 
 @[inline] def swapAt (a : Array α) (i : Fin a.size) (v : α) : α × Array α :=
   let e := a.get i
@@ -303,8 +276,8 @@ def mapM {α : Type u} {β : Type v} {m : Type v → Type w} [Monad m] (f : α
       map (i+1) (r.push (← f as[i]))
     else
       pure r
-  termination_by as.size - i
   map 0 (mkEmpty as.size)
+termination_by map => as.size - i
 
 @[inline]
 def mapIdxM {α : Type u} {β : Type v} {m : Type v → Type w} [Monad m] (as : Array α) (f : Fin as.size → α → m β) : m (Array β) :=
@@ -375,12 +348,12 @@ def anyM {α : Type u} {m : Type → Type w} [Monad m] (p : α → m Bool) (as :
           loop (j+1)
       else
         pure false
-      termination_by stop - j
     loop start
   if h : stop ≤ as.size then
     any stop h
   else
     any as.size (Nat.le_refl _)
+termination_by loop i j => stop - j
 
 @[inline]
 def allM {α : Type u} {m : Type → Type w} [Monad m] (p : α → m Bool) (as : Array α) (start := 0) (stop := as.size) : m Bool :=
@@ -428,10 +401,6 @@ def map {α : Type u} {β : Type v} (f : α → β) (as : Array α) : Array β :
 def mapIdx {α : Type u} {β : Type v} (as : Array α) (f : Fin as.size → α → β) : Array β :=
   Id.run <| as.mapIdxM f
 
-/-- Turns `#[a, b]` into `#[(a, 0), (b, 1)]`. -/
-def zipWithIndex (arr : Array α) : Array (α × Nat) :=
-  arr.mapIdx fun i a => (a, i)
-
 @[inline]
 def find? {α : Type} (as : Array α) (p : α → Bool) : Option α :=
   Id.run <| as.findM? p
@@ -506,11 +475,6 @@ def elem [BEq α] (a : α) (as : Array α) : Bool :=
 def toList (as : Array α) : List α :=
   as.foldr List.cons []
 
-/-- Prepends an `Array α` onto the front of a list.  Equivalent to `as.toList ++ l`. -/
-@[inline]
-def toListAppend (as : Array α) (l : List α) : List α :=
-  as.foldr List.cons l
-
 instance {α : Type u} [Repr α] : Repr (Array α) where
   reprPrec a _ :=
     let _ : Std.ToFormat α := ⟨repr⟩
@@ -540,13 +504,6 @@ def concatMapM [Monad m] (f : α → m (Array β)) (as : Array α) : m (Array β
 def concatMap (f : α → Array β) (as : Array α) : Array β :=
   as.foldl (init := empty) fun bs a => bs ++ f a
 
-/-- Joins array of array into a single array.
-
-`flatten #[#[a₁, a₂, ⋯], #[b₁, b₂, ⋯], ⋯]` = `#[a₁, a₂, ⋯, b₁, b₂, ⋯]`
--/
-def flatten (as : Array (Array α)) : Array α :=
-  as.foldl (init := empty) fun r a => r ++ a
-
 end Array
 
 export Array (mkArray)
@@ -566,7 +523,7 @@ def isEqvAux (a b : Array α) (hsz : a.size = b.size) (p : α → α → Bool) (
      p a[i] b[i] && isEqvAux a b hsz p (i+1)
   else
     true
-termination_by a.size - i
+termination_by _ => a.size - i
 
 @[inline] def isEqv (a b : Array α) (p : α → α → Bool) : Bool :=
   if h : a.size = b.size then
@@ -670,7 +627,7 @@ def indexOfAux [BEq α] (a : Array α) (v : α) (i : Nat) : Option (Fin a.size)
     if a.get idx == v then some idx
     else indexOfAux a v (i+1)
   else none
-termination_by a.size - i
+termination_by _ => a.size - i
 
 def indexOf? [BEq α] (a : Array α) (v : α) : Option (Fin a.size) :=
   indexOfAux a v 0
@@ -702,7 +659,7 @@ where
       loop as (i+1) ⟨j-1, this⟩
     else
       as
-termination_by j - i
+termination_by _ => j - i
 
 def popWhile (p : α → Bool) (as : Array α) : Array α :=
   if h : as.size > 0 then
@@ -712,7 +669,7 @@ def popWhile (p : α → Bool) (as : Array α) : Array α :=
       as
   else
     as
-termination_by as.size
+termination_by popWhile as => as.size
 
 def takeWhile (p : α → Bool) (as : Array α) : Array α :=
   let rec go (i : Nat) (r : Array α) : Array α :=
@@ -724,8 +681,8 @@ def takeWhile (p : α → Bool) (as : Array α) : Array α :=
         r
     else
       r
-    termination_by as.size - i
   go 0 #[]
+termination_by go i r => as.size - i
 
 def eraseIdxAux (i : Nat) (a : Array α) : Array α :=
   if h : i < a.size then
@@ -735,7 +692,7 @@ def eraseIdxAux (i : Nat) (a : Array α) : Array α :=
     eraseIdxAux (i+1) a'
   else
     a.pop
-termination_by a.size - i
+termination_by _ => a.size - i
 
 def feraseIdx (a : Array α) (i : Fin a.size) : Array α :=
   eraseIdxAux (i.val + 1) a
@@ -750,7 +707,7 @@ def eraseIdxSzAux (a : Array α) (i : Nat) (r : Array α) (heq : r.size = a.size
     eraseIdxSzAux a (i+1) (r.swap idx idx1) ((size_swap r idx idx1).trans heq)
   else
     ⟨r.pop, (size_pop r).trans (heq ▸ rfl)⟩
-termination_by r.size - i
+termination_by _ => r.size - i
 
 def eraseIdx' (a : Array α) (i : Fin a.size) : { r : Array α // r.size = a.size - 1 } :=
   eraseIdxSzAux a (i.val + 1) a rfl
@@ -769,10 +726,10 @@ def erase [BEq α] (as : Array α) (a : α) : Array α :=
       loop as ⟨j', by rw [size_swap]; exact j'.2⟩
     else
       as
-    termination_by j.1
   let j := as.size
   let as := as.push a
   loop as ⟨j, size_push .. ▸ j.lt_succ_self⟩
+termination_by loop j => j.1
 
 /-- Insert element `a` at position `i`. Panics if `i` is not `i ≤ as.size`. -/
 def insertAt! (as : Array α) (i : Nat) (a : α) : Array α :=
@@ -822,7 +779,7 @@ def isPrefixOfAux [BEq α] (as bs : Array α) (hle : as.size ≤ bs.size) (i : N
       false
   else
     true
-termination_by as.size - i
+termination_by _ => as.size - i
 
 /-- Return true iff `as` is a prefix of `bs`.
 That is, `bs = as ++ t` for some `t : List α`.-/
@@ -843,7 +800,7 @@ private def allDiffAux [BEq α] (as : Array α) (i : Nat) : Bool :=
     allDiffAuxAux as as[i] i h && allDiffAux as (i+1)
   else
     true
-termination_by as.size - i
+termination_by _ => as.size - i
 
 def allDiff [BEq α] (as : Array α) : Bool :=
   allDiffAux as 0
@@ -858,7 +815,7 @@ def allDiff [BEq α] (as : Array α) : Bool :=
       cs
   else
     cs
-termination_by as.size - i
+termination_by _ => as.size - i
 
 @[inline] def zipWith (as : Array α) (bs : Array β) (f : α → β → γ) : Array γ :=
   zipWithAux f as bs 0 #[]

src/Init/Data/Array/BasicAux.lean

@@ -47,7 +47,7 @@ where
       have hlt : i < as.size := Nat.lt_of_le_of_ne hle h
       let b ← f as[i]
       go (i+1) ⟨acc.val.push b, by simp [acc.property]⟩ hlt
-  termination_by as.size - i
+termination_by go i _ _ => as.size - i
 
 @[inline] private unsafe def mapMonoMImp [Monad m] (as : Array α) (f : α → m α) : m (Array α) :=
   go 0 as

src/Init/Data/Array/DecidableEq.lean

@@ -20,7 +20,7 @@ theorem eq_of_isEqvAux [DecidableEq α] (a b : Array α) (hsz : a.size = b.size)
   · have heq : i = a.size := Nat.le_antisymm hi (Nat.ge_of_not_lt h)
     subst heq
     exact absurd (Nat.lt_of_lt_of_le high low) (Nat.lt_irrefl j)
-termination_by a.size - i
+termination_by _ => a.size - i
 
 theorem eq_of_isEqv [DecidableEq α] (a b : Array α) : Array.isEqv a b (fun x y => x = y) → a = b := by
   simp [Array.isEqv]
@@ -36,7 +36,7 @@ theorem isEqvAux_self [DecidableEq α] (a : Array α) (i : Nat) : Array.isEqvAux
   split
   case inl h => simp [h, isEqvAux_self a (i+1)]
   case inr h => simp [h]
-termination_by a.size - i
+termination_by _ => a.size - i
 
 theorem isEqv_self [DecidableEq α] (a : Array α) : Array.isEqv a a (fun x y => x = y) = true := by
   simp [isEqv, isEqvAux_self]

src/Init/Data/Array/QSort.lean

@@ -26,8 +26,8 @@ def qpartition (as : Array α) (lt : α → α → Bool) (lo hi : Nat) : Nat ×
     else
       let as := as.swap! i hi
       (i, as)
-    termination_by hi - j
   loop as lo lo
+termination_by _ => hi - j
 
 @[inline] partial def qsort (as : Array α) (lt : α → α → Bool) (low := 0) (high := as.size - 1) : Array α :=
   let rec @[specialize] sort (as : Array α) (low high : Nat) :=

src/Init/Data/ByteArray/Basic.lean

@@ -81,7 +81,7 @@ def isEmpty (s : ByteArray) : Bool :=
   If `exact` is `false`, the capacity will be doubled when grown. -/
 @[extern "lean_byte_array_copy_slice"]
 def copySlice (src : @& ByteArray) (srcOff : Nat) (dest : ByteArray) (destOff len : Nat) (exact : Bool := true) : ByteArray :=
-  ⟨dest.data.extract 0 destOff ++ src.data.extract srcOff (srcOff + len) ++ dest.data.extract (destOff + min len (src.data.size - srcOff)) dest.data.size⟩
+  ⟨dest.data.extract 0 destOff ++ src.data.extract srcOff (srcOff + len) ++ dest.data.extract (destOff + len) dest.data.size⟩
 
 def extract (a : ByteArray) (b e : Nat) : ByteArray :=
   a.copySlice b empty 0 (e - b)

src/Init/Data/Fin/Basic.lean

@@ -100,7 +100,7 @@ instance : ShiftLeft (Fin n) where
 instance : ShiftRight (Fin n) where
   shiftRight := Fin.shiftRight
 
-instance instOfNat : OfNat (Fin (no_index (n+1))) i where
+instance : OfNat (Fin (no_index (n+1))) i where
   ofNat := Fin.ofNat i
 
 instance : Inhabited (Fin (no_index (n+1))) where

src/Init/Data/Float.lean

@@ -26,8 +26,6 @@ opaque floatSpec : FloatSpec := {
   decLe := fun _ _ => inferInstanceAs (Decidable True)
 }
 
-/-- Native floating point type, corresponding to the IEEE 754 *binary64* format
-(`double` in C or `f64` in Rust). -/
 structure Float where
   val : floatSpec.float
 

src/Init/Data/Format/Basic.lean

@@ -300,18 +300,11 @@ instance : MonadPrettyFormat (StateM State) where
   startTag _         := return ()
   endTags _          := return ()
 
-/--
-Renders a `Format` to a string.
-* `width`: the total width
-* `indent`: the initial indentation to use for wrapped lines
-  (subsequent wrapping may increase the indentation)
-* `column`: begin the first line wrap `column` characters earlier than usual
-  (this is useful when the output String will be printed starting at `column`)
--/
+/-- Pretty-print a `Format` object as a string with expected width `w`. -/
 @[export lean_format_pretty]
-def pretty (f : Format) (width : Nat := defWidth) (indent : Nat := 0) (column := 0) : String :=
-  let act : StateM State Unit := prettyM f width indent
-  State.out <| act (State.mk "" column) |>.snd
+def pretty (f : Format) (w : Nat := defWidth) : String :=
+  let act: StateM State Unit := prettyM f w
+  act {} |>.snd.out
 
 end Format
 

src/Init/Data/Int/Basic.lean

@@ -49,7 +49,7 @@ attribute [extern "lean_int_neg_succ_of_nat"] Int.negSucc
 
 instance : Coe Nat Int := ⟨Int.ofNat⟩
 
-instance instOfNat : OfNat Int n where
+instance : OfNat Int n where
   ofNat := Int.ofNat n
 
 namespace Int

src/Init/Data/List/Basic.lean

@@ -124,8 +124,7 @@ def appendTR (as bs : List α) : List α :=
   induction as with
   | nil  => rfl
   | cons a as ih =>
-    rw [reverseAux, reverseAux_reverseAux]
-    simp [List.append, ih, reverseAux]
+    simp [reverseAux, List.append, ih, reverseAux_reverseAux]
 
 instance : Append (List α) := ⟨List.append⟩
 
@@ -558,22 +557,16 @@ def takeWhile (p : α → Bool) : (xs : List α) → List α
 /--
 `O(|l|)`. Returns true if `p` is true for any element of `l`.
 * `any p [a, b, c] = p a || p b || p c`
-
-Short-circuits upon encountering the first `true`.
 -/
-def any : List α -> (α → Bool) -> Bool
-  | [], _ => false
-  | h :: t, p => p h || any t p
+@[inline] def any (l : List α) (p : α → Bool) : Bool :=
+  foldr (fun a r => p a || r) false l
 
 /--
 `O(|l|)`. Returns true if `p` is true for every element of `l`.
 * `all p [a, b, c] = p a && p b && p c`
-
-Short-circuits upon encountering the first `false`.
 -/
-def all : List α -> (α → Bool) -> Bool
-  | [], _ => true
-  | h :: t, p => p h && all t p
+@[inline] def all (l : List α) (p : α → Bool) : Bool :=
+  foldr (fun a r => p a && r) true l
 
 /--
 `O(|l|)`. Returns true if `true` is an element of the list of booleans `l`.

src/Init/Data/Nat/Gcd.lean

@@ -8,14 +8,14 @@ import Init.Data.Nat.Div
 
 namespace Nat
 
+private def gcdF (x : Nat) : (∀ x₁, x₁ < x → Nat → Nat) → Nat → Nat :=
+  match x with
+  | 0      => fun _ y => y
+  | succ x => fun f y => f (y % succ x) (mod_lt _ (zero_lt_succ  _)) (succ x)
+
 @[extern "lean_nat_gcd"]
-def gcd (m n : @& Nat) : Nat :=
-  if m = 0 then
-    n
-  else
-    gcd (n % m) m
-termination_by m
-decreasing_by simp_wf; apply mod_lt _ (zero_lt_of_ne_zero _); assumption
+def gcd (a b : @& Nat) : Nat :=
+  WellFounded.fix (measure id).wf gcdF a b
 
 @[simp] theorem gcd_zero_left (y : Nat) : gcd 0 y = y :=
   rfl

src/Init/Data/Nat/Power2.lean

@@ -21,8 +21,8 @@ where
       go (power * 2) (Nat.mul_pos h (by decide))
     else
       power
-  termination_by n - power
-  decreasing_by simp_wf; apply nextPowerOfTwo_dec <;> assumption
+termination_by go p h => n - p
+decreasing_by simp_wf; apply nextPowerOfTwo_dec <;> assumption
 
 def isPowerOfTwo (n : Nat) := ∃ k, n = 2 ^ k
 
@@ -48,7 +48,7 @@ where
     split
     . exact isPowerOfTwo_go (power*2) (Nat.mul_pos h₁ (by decide)) (Nat.mul2_isPowerOfTwo_of_isPowerOfTwo h₂)
     . assumption
-  termination_by n - power
-  decreasing_by simp_wf; apply nextPowerOfTwo_dec <;> assumption
+termination_by isPowerOfTwo_go p _ _ => n - p
+decreasing_by simp_wf; apply nextPowerOfTwo_dec <;> assumption
 
 end Nat

src/Init/Data/OfScientific.lean

@@ -6,7 +6,7 @@ Authors: Leonardo de Moura
 prelude
 import Init.Meta
 import Init.Data.Float
-import Init.Data.Nat.Log2
+import Init.Data.Nat
 
 /-- For decimal and scientific numbers (e.g., `1.23`, `3.12e10`).
    Examples:

src/Init/Data/Range.lean

@@ -76,12 +76,10 @@ macro_rules
 end Range
 end Std
 
-theorem Membership.mem.upper {i : Nat} {r : Std.Range} (h : i ∈ r) : i < r.stop := h.2
+theorem Membership.mem.upper {i : Nat} {r : Std.Range} (h : i ∈ r) : i < r.stop := by
+  simp [Membership.mem] at h
+  exact h.2
 
-theorem Membership.mem.lower {i : Nat} {r : Std.Range} (h : i ∈ r) : r.start ≤ i := h.1
-
-theorem Membership.get_elem_helper {i n : Nat} {r : Std.Range} (h₁ : i ∈ r) (h₂ : r.stop = n) :
-    i < n := h₂ ▸ h₁.2
-
-macro_rules
-  | `(tactic| get_elem_tactic_trivial) => `(tactic| apply Membership.get_elem_helper; assumption; rfl)
+theorem Membership.mem.lower {i : Nat} {r : Std.Range} (h : i ∈ r) : r.start ≤ i := by
+  simp [Membership.mem] at h
+  exact h.1

src/Init/Data/String/Basic.lean

@@ -159,7 +159,7 @@ def posOfAux (s : String) (c : Char) (stopPos : Pos) (pos : Pos) : Pos :=
       have := Nat.sub_lt_sub_left h (lt_next s pos)
       posOfAux s c stopPos (s.next pos)
   else pos
-termination_by stopPos.1 - pos.1
+termination_by _ => stopPos.1 - pos.1
 
 @[inline] def posOf (s : String) (c : Char) : Pos :=
   posOfAux s c s.endPos 0
@@ -171,7 +171,7 @@ def revPosOfAux (s : String) (c : Char) (pos : Pos) : Option Pos :=
     let pos := s.prev pos
     if s.get pos == c then some pos
     else revPosOfAux s c pos
-termination_by pos.1
+termination_by _ => pos.1
 
 def revPosOf (s : String) (c : Char) : Option Pos :=
   revPosOfAux s c s.endPos
@@ -183,7 +183,7 @@ def findAux (s : String) (p : Char → Bool) (stopPos : Pos) (pos : Pos) : Pos :
       have := Nat.sub_lt_sub_left h (lt_next s pos)
       findAux s p stopPos (s.next pos)
   else pos
-termination_by stopPos.1 - pos.1
+termination_by _ => stopPos.1 - pos.1
 
 @[inline] def find (s : String) (p : Char → Bool) : Pos :=
   findAux s p s.endPos 0
@@ -195,7 +195,7 @@ def revFindAux (s : String) (p : Char → Bool) (pos : Pos) : Option Pos :=
     let pos := s.prev pos
     if p (s.get pos) then some pos
     else revFindAux s p pos
-termination_by pos.1
+termination_by _ => pos.1
 
 def revFind (s : String) (p : Char → Bool) : Option Pos :=
   revFindAux s p s.endPos
@@ -213,8 +213,8 @@ def firstDiffPos (a b : String) : Pos :=
         have := Nat.sub_lt_sub_left h (lt_next a i)
         loop (a.next i)
     else i
-    termination_by stopPos.1 - i.1
   loop 0
+termination_by loop => stopPos.1 - i.1
 
 @[extern "lean_string_utf8_extract"]
 def extract : (@& String) → (@& Pos) → (@& Pos) → String
@@ -240,7 +240,7 @@ where
       splitAux s p i' i' (s.extract b i :: r)
     else
       splitAux s p b (s.next i) r
-termination_by s.endPos.1 - i.1
+termination_by _ => s.endPos.1 - i.1
 
 @[specialize] def split (s : String) (p : Char → Bool) : List String :=
   splitAux s p 0 0 []
@@ -260,7 +260,7 @@ def splitOnAux (s sep : String) (b : Pos) (i : Pos) (j : Pos) (r : List String)
         splitOnAux s sep b i j r
     else
       splitOnAux s sep b (s.next i) 0 r
-termination_by s.endPos.1 - i.1
+termination_by _ => s.endPos.1 - i.1
 
 def splitOn (s : String) (sep : String := " ") : List String :=
   if sep == "" then [s] else splitOnAux s sep 0 0 0 []
@@ -369,7 +369,7 @@ def offsetOfPosAux (s : String) (pos : Pos) (i : Pos) (offset : Nat) : Nat :=
   else
     have := Nat.sub_lt_sub_left (Nat.gt_of_not_le (mt decide_eq_true h)) (lt_next s _)
     offsetOfPosAux s pos (s.next i) (offset+1)
-termination_by s.endPos.1 - i.1
+termination_by _ => s.endPos.1 - i.1
 
 def offsetOfPos (s : String) (pos : Pos) : Nat :=
   offsetOfPosAux s pos 0 0
@@ -379,7 +379,7 @@ def offsetOfPos (s : String) (pos : Pos) : Nat :=
     have := Nat.sub_lt_sub_left h (lt_next s i)
     foldlAux f s stopPos (s.next i) (f a (s.get i))
   else a
-termination_by stopPos.1 - i.1
+termination_by _ => stopPos.1 - i.1
 
 @[inline] def foldl {α : Type u} (f : α → Char → α) (init : α) (s : String) : α :=
   foldlAux f s s.endPos 0 init
@@ -392,7 +392,7 @@ termination_by stopPos.1 - i.1
     let a := f (s.get i) a
     foldrAux f a s i begPos
   else a
-termination_by i.1
+termination_by _ => i.1
 
 @[inline] def foldr {α : Type u} (f : Char → α → α) (init : α) (s : String) : α :=
   foldrAux f init s s.endPos 0
@@ -404,7 +404,7 @@ termination_by i.1
       have := Nat.sub_lt_sub_left h (lt_next s i)
       anyAux s stopPos p (s.next i)
   else false
-termination_by stopPos.1 - i.1
+termination_by _ => stopPos.1 - i.1
 
 @[inline] def any (s : String) (p : Char → Bool) : Bool :=
   anyAux s s.endPos p 0
@@ -463,7 +463,7 @@ theorem mapAux_lemma (s : String) (i : Pos) (c : Char) (h : ¬s.atEnd i) :
     have := mapAux_lemma s i c h
     let s := s.set i c
     mapAux f (s.next i) s
-termination_by s.endPos.1 - i.1
+termination_by _ => s.endPos.1 - i.1
 
 @[inline] def map (f : Char → Char) (s : String) : String :=
   mapAux f 0 s
@@ -490,7 +490,7 @@ where
       have := Nat.sub_lt_sub_left h (Nat.add_lt_add_left (one_le_csize c₁) off1.1)
       c₁ == c₂ && loop (off1 + c₁) (off2 + c₂) stop1
     else true
-  termination_by stop1.1 - off1.1
+termination_by loop => stop1.1 - off1.1
 
 /-- Return true iff `p` is a prefix of `s` -/
 def isPrefixOf (p : String) (s : String) : Bool :=
@@ -512,8 +512,8 @@ def replace (s pattern replacement : String) : String :=
         else
           have := Nat.sub_lt_sub_left this (lt_next s pos)
           loop acc accStop (s.next pos)
-      termination_by s.endPos.1 - pos.1
     loop "" 0 0
+termination_by loop => s.endPos.1 - pos.1
 
 end String
 
@@ -612,8 +612,8 @@ def splitOn (s : Substring) (sep : String := " ") : List Substring :=
         else
           s.extract b i :: r
         r.reverse
-      termination_by s.bsize - i.1
     loop 0 0 0 []
+termination_by loop => s.bsize - i.1
 
 @[inline] def foldl {α : Type u} (f : α → Char → α) (init : α) (s : Substring) : α :=
   match s with
@@ -640,7 +640,7 @@ def contains (s : Substring) (c : Char) : Bool :=
       takeWhileAux s stopPos p (s.next i)
     else i
   else i
-termination_by stopPos.1 - i.1
+termination_by _ => stopPos.1 - i.1
 
 @[inline] def takeWhile : Substring → (Char → Bool) → Substring
   | ⟨s, b, e⟩, p =>
@@ -661,7 +661,7 @@ termination_by stopPos.1 - i.1
     if !p c then i
     else takeRightWhileAux s begPos p i'
   else i
-termination_by i.1
+termination_by _ => i.1
 
 @[inline] def takeRightWhile : Substring → (Char → Bool) → Substring
   | ⟨s, b, e⟩, p =>

src/Init/Data/UInt/Basic.lean

@@ -5,6 +5,7 @@ Authors: Leonardo de Moura
 -/
 prelude
 import Init.Data.Fin.Basic
+import Init.System.Platform
 
 open Nat
 
@@ -38,7 +39,7 @@ def UInt8.shiftRight (a b : UInt8) : UInt8 := ⟨a.val >>> (modn b 8).val⟩
 def UInt8.lt (a b : UInt8) : Prop := a.val < b.val
 def UInt8.le (a b : UInt8) : Prop := a.val ≤ b.val
 
-instance UInt8.instOfNat : OfNat UInt8 n := ⟨UInt8.ofNat n⟩
+instance : OfNat UInt8 n   := ⟨UInt8.ofNat n⟩
 instance : Add UInt8       := ⟨UInt8.add⟩
 instance : Sub UInt8       := ⟨UInt8.sub⟩
 instance : Mul UInt8       := ⟨UInt8.mul⟩
@@ -109,7 +110,8 @@ def UInt16.shiftRight (a b : UInt16) : UInt16 := ⟨a.val >>> (modn b 16).val⟩
 def UInt16.lt (a b : UInt16) : Prop := a.val < b.val
 def UInt16.le (a b : UInt16) : Prop := a.val ≤ b.val
 
-instance UInt16.instOfNat : OfNat UInt16 n := ⟨UInt16.ofNat n⟩
+
+instance : OfNat UInt16 n   := ⟨UInt16.ofNat n⟩
 instance : Add UInt16       := ⟨UInt16.add⟩
 instance : Sub UInt16       := ⟨UInt16.sub⟩
 instance : Mul UInt16       := ⟨UInt16.mul⟩
@@ -150,14 +152,6 @@ instance : Min UInt16 := minOfLe
 def UInt32.ofNat (n : @& Nat) : UInt32 := ⟨Fin.ofNat n⟩
 @[extern "lean_uint32_of_nat"]
 def UInt32.ofNat' (n : Nat) (h : n < UInt32.size) : UInt32 := ⟨⟨n, h⟩⟩
-/--
-Converts the given natural number to `UInt32`, but returns `2^32 - 1` for natural numbers `>= 2^32`.
--/
-def UInt32.ofNatTruncate (n : Nat) : UInt32 :=
-  if h : n < UInt32.size then
-    UInt32.ofNat' n h
-  else
-    UInt32.ofNat' (UInt32.size - 1) (by decide)
 abbrev Nat.toUInt32 := UInt32.ofNat
 @[extern "lean_uint32_add"]
 def UInt32.add (a b : UInt32) : UInt32 := ⟨a.val + b.val⟩
@@ -190,7 +184,7 @@ def UInt8.toUInt32 (a : UInt8) : UInt32 := a.toNat.toUInt32
 @[extern "lean_uint16_to_uint32"]
 def UInt16.toUInt32 (a : UInt16) : UInt32 := a.toNat.toUInt32
 
-instance UInt32.instOfNat : OfNat UInt32 n := ⟨UInt32.ofNat n⟩
+instance : OfNat UInt32 n   := ⟨UInt32.ofNat n⟩
 instance : Add UInt32       := ⟨UInt32.add⟩
 instance : Sub UInt32       := ⟨UInt32.sub⟩
 instance : Mul UInt32       := ⟨UInt32.mul⟩
@@ -250,7 +244,7 @@ def UInt16.toUInt64 (a : UInt16) : UInt64 := a.toNat.toUInt64
 @[extern "lean_uint32_to_uint64"]
 def UInt32.toUInt64 (a : UInt32) : UInt64 := a.toNat.toUInt64
 
-instance UInt64.instOfNat : OfNat UInt64 n := ⟨UInt64.ofNat n⟩
+instance : OfNat UInt64 n   := ⟨UInt64.ofNat n⟩
 instance : Add UInt64       := ⟨UInt64.add⟩
 instance : Sub UInt64       := ⟨UInt64.sub⟩
 instance : Mul UInt64       := ⟨UInt64.mul⟩
@@ -328,7 +322,7 @@ def USize.toUInt32 (a : USize) : UInt32 := a.toNat.toUInt32
 def USize.lt (a b : USize) : Prop := a.val < b.val
 def USize.le (a b : USize) : Prop := a.val ≤ b.val
 
-instance USize.instOfNat : OfNat USize n := ⟨USize.ofNat n⟩
+instance : OfNat USize n   := ⟨USize.ofNat n⟩
 instance : Add USize       := ⟨USize.add⟩
 instance : Sub USize       := ⟨USize.sub⟩
 instance : Mul USize       := ⟨USize.mul⟩

src/Init/Meta.lean

@@ -563,17 +563,8 @@ def SepArray.ofElemsUsingRef [Monad m] [MonadRef m] {sep} (elems : Array Syntax)
 instance : Coe (Array Syntax) (SepArray sep) where
   coe := SepArray.ofElems
 
-/--
-Constructs a typed separated array from elements.
-The given array does not include the separators.
-
-Like `Syntax.SepArray.ofElems` but for typed syntax.
--/
-def TSepArray.ofElems {sep} (elems : Array (TSyntax k)) : TSepArray k sep :=
-  .mk (SepArray.ofElems (sep := sep) (TSyntaxArray.raw elems)).1
-
 instance : Coe (TSyntaxArray k) (TSepArray k sep) where
-  coe := TSepArray.ofElems
+  coe a := ⟨mkSepArray a.raw (mkAtom sep)⟩
 
 /-- Create syntax representing a Lean term application, but avoid degenerate empty applications. -/
 def mkApp (fn : Term) : (args : TSyntaxArray `term) → Term
@@ -782,16 +773,6 @@ def decodeQuotedChar (s : String) (i : String.Pos) : Option (Char × String.Pos)
   else
     none
 
-/--
-Decodes a valid string gap after the `\`.
-Note that this function matches `"\" whitespace+` rather than
-the more restrictive `"\" newline whitespace*` since this simplifies the implementation.
-Justification: this does not overlap with any other sequences beginning with `\`.
--/
-def decodeStringGap (s : String) (i : String.Pos) : Option String.Pos := do
-  guard <| (s.get i).isWhitespace
-  s.nextWhile Char.isWhitespace (s.next i)
-
 partial def decodeStrLitAux (s : String) (i : String.Pos) (acc : String) : Option String := do
   let c := s.get i
   let i := s.next i
@@ -800,49 +781,14 @@ partial def decodeStrLitAux (s : String) (i : String.Pos) (acc : String) : Optio
   else if s.atEnd i then
     none
   else if c == '\\' then do
-    if let some (c, i) := decodeQuotedChar s i then
-      decodeStrLitAux s i (acc.push c)
-    else if let some i := decodeStringGap s i then
-      decodeStrLitAux s i acc
-    else
-      none
+    let (c, i) ← decodeQuotedChar s i
+    decodeStrLitAux s i (acc.push c)
   else
     decodeStrLitAux s i (acc.push c)
 
-/--
-Takes a raw string literal, counts the number of `#`'s after the `r`, and interprets it as a string.
-The position `i` should start at `1`, which is the character after the leading `r`.
-The algorithm is simple: we are given `r##...#"...string..."##...#` with zero or more `#`s.
-By counting the number of leading `#`'s, we can extract the `...string...`.
--/
-partial def decodeRawStrLitAux (s : String) (i : String.Pos) (num : Nat) : String :=
-  let c := s.get i
-  let i := s.next i
-  if c == '#' then
-    decodeRawStrLitAux s i (num + 1)
-  else
-    s.extract i ⟨s.utf8ByteSize - (num + 1)⟩
-
-/--
-Takes the string literal lexical syntax parsed by the parser and interprets it as a string.
-This is where escape sequences are processed for example.
-The string `s` is is either a plain string literal or a raw string literal.
-
-If it returns `none` then the string literal is ill-formed, which indicates a bug in the parser.
-The function is not required to return `none` if the string literal is ill-formed.
--/
 def decodeStrLit (s : String) : Option String :=
-  if s.get 0 == 'r' then
-    decodeRawStrLitAux s ⟨1⟩ 0
-  else
-    decodeStrLitAux s ⟨1⟩ ""
+  decodeStrLitAux s ⟨1⟩ ""
 
-/--
-If the provided `Syntax` is a string literal, returns the string it represents.
-
-Even if the `Syntax` is a `str` node, the function may return `none` if its internally ill-formed.
-The parser should always create well-formed `str` nodes.
--/
 def isStrLit? (stx : Syntax) : Option String :=
   match isLit? strLitKind stx with
   | some val => decodeStrLit val
@@ -1048,7 +994,7 @@ where
       go (i+1) (args.push (quote xs[i]))
     else
       Syntax.mkCApp (Name.mkStr2 "Array" ("mkArray" ++ toString xs.size)) args
-  termination_by xs.size - i
+termination_by go i _ => xs.size - i
 
 instance [Quote α `term] : Quote (Array α) `term where
   quote := quoteArray
@@ -1216,12 +1162,8 @@ private partial def decodeInterpStrLit (s : String) : Option String :=
     else if s.atEnd i then
       none
     else if c == '\\' then do
-      if let some (c, i) := decodeInterpStrQuotedChar s i then
-        loop i (acc.push c)
-      else if let some i := decodeStringGap s i then
-        loop i acc
-      else
-        none
+      let (c, i) ← decodeInterpStrQuotedChar s i
+      loop i (acc.push c)
     else
       loop i (acc.push c)
   loop ⟨1⟩ ""

src/Init/MetaTypes.lean

@@ -21,14 +21,7 @@ structure Module where
 namespace Meta
 
 inductive TransparencyMode where
-  /-- unfold all constants, even those tagged as `@[irreducible]`. -/
-  | all
-  /-- unfold all constants except those tagged as `@[irreducible]`. -/
-  | default
-  /-- unfold only constants tagged with the `@[reducible]` attribute. -/
-  | reducible
-  /-- unfold reducible constants and constants tagged with the `@[instance]` attribute. -/
-  | instances
+  | all | default | reducible | instances
   deriving Inhabited, BEq
 
 inductive EtaStructMode where

src/Init/NotationExtra.lean

@@ -170,20 +170,6 @@ See [Theorem Proving in Lean 4][tpil4] for more information.
 -/
 syntax (name := calcTactic) "calc" calcSteps : tactic
 
-/--
-Denotes a term that was omitted by the pretty printer.
-This is only used for pretty printing, and it cannot be elaborated.
-The presence of `⋯` is controlled by the `pp.deepTerms` and `pp.deepTerms.threshold`
-options.
--/
-syntax "⋯" : term
-
-macro_rules | `(⋯) => Macro.throwError "\
-  Error: The '⋯' token is used by the pretty printer to indicate omitted terms, \
-  and it cannot be elaborated. \
-  Its presence in pretty printing output is controlled by the 'pp.deepTerms' and \
-  `pp.deepTerms.threshold` options."
-
 @[app_unexpander Unit.unit] def unexpandUnit : Lean.PrettyPrinter.Unexpander
   | `($(_)) => `(())
 
@@ -191,13 +177,9 @@ macro_rules | `(⋯) => Macro.throwError "\
   | `($(_)) => `([])
 
 @[app_unexpander List.cons] def unexpandListCons : Lean.PrettyPrinter.Unexpander
-  | `($(_) $x $tail) =>
-    match tail with
-    | `([])      => `([$x])
-    | `([$xs,*]) => `([$x, $xs,*])
-    | `(⋯)       => `([$x, $tail]) -- Unexpands to `[x, y, z, ⋯]` for `⋯ : List α`
-    | _          => throw ()
-  | _ => throw ()
+  | `($(_) $x [])      => `([$x])
+  | `($(_) $x [$xs,*]) => `([$x, $xs,*])
+  | _                  => throw ()
 
 @[app_unexpander List.toArray] def unexpandListToArray : Lean.PrettyPrinter.Unexpander
   | `($(_) [$xs,*]) => `(#[$xs,*])

src/Init/Prelude.lean

@@ -9,9 +9,9 @@ set_option linter.missingDocs true -- keep it documented
 /-!
 # Init.Prelude
 
-This is the first file in the Lean import hierarchy. It is responsible for setting
-up basic definitions, most of which Lean already has "built in knowledge" about,
-so it is important that they be set up in exactly this way. (For example, Lean will
+This is the first file in the lean import hierarchy. It is responsible for setting
+up basic definitions, most of which lean already has "built in knowledge" about,
+so it is important that they be set up in exactly this way. (For example, lean will
 use `PUnit` in the desugaring of `do` notation, or in the pattern match compiler.)
 
 -/
@@ -24,7 +24,7 @@ The identity function. `id` takes an implicit argument `α : Sort u`
 
 Although this may look like a useless function, one application of the identity
 function is to explicitly put a type on an expression. If `e` has type `T`,
-and `T'` is definitionally equal to `T`, then `@id T' e` typechecks, and Lean
+and `T'` is definitionally equal to `T`, then `@id T' e` typechecks, and lean
 knows that this expression has type `T'` rather than `T`. This can make a
 difference for typeclass inference, since `T` and `T'` may have different
 typeclass instances on them. `show T' from e` is sugar for an `@id T' e`
@@ -66,19 +66,6 @@ example (b : Bool) : Function.const Bool 10 b = 10 :=
 @[inline] def Function.const {α : Sort u} (β : Sort v) (a : α) : β → α :=
   fun _ => a
 
-/--
-The encoding of `let_fun x := v; b` is `letFun v (fun x => b)`.
-This is equal to `(fun x => b) v`, so the value of `x` is not accessible to `b`.
-This is in contrast to `let x := v; b`, where the value of `x` is accessible to `b`.
-
-There is special support for `letFun`.
-Both WHNF and `simp` are aware of `letFun` and can reduce it when zeta reduction is enabled,
-despite the fact it is marked `irreducible`.
-For metaprogramming, the function `Lean.Expr.letFun?` can be used to recognize a `let_fun` expression
-to extract its parts as if it were a `let` expression.
--/
-@[irreducible] def letFun {α : Sort u} {β : α → Sort v} (v : α) (f : (x : α) → β x) : β v := f v
-
 set_option checkBinderAnnotations false in
 /--
 `inferInstance` synthesizes a value of any target type by typeclass
@@ -287,9 +274,9 @@ inductive Eq : α → α → Prop where
 same as `Eq.refl` except that it takes `a` implicitly instead of explicitly.
 
 This is a more powerful theorem than it may appear at first, because although
-the statement of the theorem is `a = a`, Lean will allow anything that is
+the statement of the theorem is `a = a`, lean will allow anything that is
 definitionally equal to that type. So, for instance, `2 + 2 = 4` is proven in
-Lean by `rfl`, because both sides are the same up to definitional equality.
+lean by `rfl`, because both sides are the same up to definitional equality.
 -/
 @[match_pattern] def rfl {α : Sort u} {a : α} : Eq a a := Eq.refl a
 
@@ -597,7 +584,7 @@ For example, the `Membership` class is defined as:
 class Membership (α : outParam (Type u)) (γ : Type v)
 ```
 This means that whenever a typeclass goal of the form `Membership ?α ?γ` comes
-up, Lean will wait to solve it until `?γ` is known, but then it will run
+up, lean will wait to solve it until `?γ` is known, but then it will run
 typeclass inference, and take the first solution it finds, for any value of `?α`,
 which thereby determines what `?α` should be.
 
@@ -712,13 +699,13 @@ nonempty, then `fun i => Classical.choice (h i) : ∀ i, α i` is a family of
 chosen elements. This is actually a bit stronger than the ZFC choice axiom;
 this is sometimes called "[global choice](https://en.wikipedia.org/wiki/Axiom_of_global_choice)".
 
-In Lean, we use the axiom of choice to derive the law of excluded middle
+In lean, we use the axiom of choice to derive the law of excluded middle
 (see `Classical.em`), so it will often show up in axiom listings where you
 may not expect. You can use `#print axioms my_thm` to find out if a given
 theorem depends on this or other axioms.
 
 This axiom can be used to construct "data", but obviously there is no algorithm
-to compute it, so Lean will require you to mark any definition that would
+to compute it, so lean will require you to mark any definition that would
 involve executing `Classical.choice` or other axioms as `noncomputable`, and
 will not produce any executable code for such definitions.
 -/
@@ -943,7 +930,7 @@ determines how to evaluate `c` to true or false. Write `if h : c then t else e`
 instead for a "dependent if-then-else" `dite`, which allows `t`/`e` to use the fact
 that `c` is true/false.
 
-Because Lean uses a strict (call-by-value) evaluation strategy, the signature of this
+Because lean uses a strict (call-by-value) evaluation strategy, the signature of this
 function is problematic in that it would require `t` and `e` to be evaluated before
 calling the `ite` function, which would cause both sides of the `if` to be evaluated.
 Even if the result is discarded, this would be a big performance problem,
@@ -1033,7 +1020,7 @@ You can prove a theorem `P n` about `n : Nat` by `induction n`, which will
 expect a proof of the theorem for `P 0`, and a proof of `P (succ i)` assuming
 a proof of `P i`. The same method also works to define functions by recursion
 on natural numbers: induction and recursion are two expressions of the same
-operation from Lean's point of view.
+operation from lean's point of view.
 
 ```
 open Nat
@@ -1069,14 +1056,14 @@ instance : Inhabited Nat where
 
 /--
 The class `OfNat α n` powers the numeric literal parser. If you write
-`37 : α`, Lean will attempt to synthesize `OfNat α 37`, and will generate
+`37 : α`, lean will attempt to synthesize `OfNat α 37`, and will generate
 the term `(OfNat.ofNat 37 : α)`.
 
 There is a bit of infinite regress here since the desugaring apparently
 still contains a literal `37` in it. The type of expressions contains a
 primitive constructor for "raw natural number literals", which you can directly
 access using the macro `nat_lit 37`. Raw number literals are always of type `Nat`.
-So it would be more correct to say that Lean looks for an instance of
+So it would be more correct to say that lean looks for an instance of
 `OfNat α (nat_lit 37)`, and it generates the term `(OfNat.ofNat (nat_lit 37) : α)`.
 -/
 class OfNat (α : Type u) (_ : Nat) where
@@ -1780,7 +1767,7 @@ Gets the word size of the platform. That is, whether the platform is 64 or 32 bi
 
 This function is opaque because we cannot guarantee at compile time that the target
 will have the same size as the host, and also because we would like to avoid
-typechecking being architecture-dependent. Nevertheless, Lean only works on
+typechecking being architecture-dependent. Nevertheless, lean only works on
 64 and 32 bit systems so we can encode this as a fact available for proof purposes.
 -/
 @[extern "lean_system_platform_nbits"] opaque System.Platform.getNumBits : Unit → Subtype fun (n : Nat) => Or (Eq n 32) (Eq n 64) :=
@@ -2226,10 +2213,9 @@ returns `a` if `opt = some a` and `dflt` otherwise.
 This function is `@[macro_inline]`, so `dflt` will not be evaluated unless
 `opt` turns out to be `none`.
 -/
-@[macro_inline] def Option.getD (opt : Option α) (dflt : α) : α :=
-  match opt with
-  | some x => x
-  | none => dflt
+@[macro_inline] def Option.getD : Option α → α → α
+  | some x, _ => x
+  | none,   e => e
 
 /--
 Map a function over an `Option` by applying the function to the contained
@@ -2518,7 +2504,7 @@ attribute [nospecialize] Inhabited
 
 /--
 The class `GetElem cont idx elem dom` implements the `xs[i]` notation.
-When you write this, given `xs : cont` and `i : idx`, Lean looks for an instance
+When you write this, given `xs : cont` and `i : idx`, lean looks for an instance
 of `GetElem cont idx elem dom`. Here `elem` is the type of `xs[i]`, while
 `dom` is whatever proof side conditions are required to make this applicable.
 For example, the instance for arrays looks like
@@ -2558,7 +2544,7 @@ export GetElem (getElem)
 with elements from `α`. This type has special support in the runtime.
 
 An array has a size and a capacity; the size is `Array.size` but the capacity
-is not observable from Lean code. Arrays perform best when unshared; as long
+is not observable from lean code. Arrays perform best when unshared; as long
 as they are used "linearly" all updates will be performed destructively on the
 array, so it has comparable performance to mutable arrays in imperative
 programming languages.
@@ -3231,7 +3217,7 @@ instance (σ : Type u) (m : Type u → Type v) [MonadStateOf σ m] : MonadState
 /--
 `modify (f : σ → σ)` applies the function `f` to the state.
 
-It is equivalent to `do set (f (← get))`, but `modify f` may be preferable
+It is equivalent to `do put (f (← get))`, but `modify f` may be preferable
 because the former does not use the state linearly (without sufficient inlining).
 -/
 @[always_inline, inline]

src/Init/SimpLemmas.lean

@@ -10,7 +10,6 @@ import Init.Core
 set_option linter.missingDocs true -- keep it documented
 
 theorem of_eq_true (h : p = True) : p := h ▸ trivial
-theorem of_eq_false (h : p = False) : ¬ p := fun hp => False.elim (h.mp hp)
 
 theorem eq_true (h : p) : p = True :=
   propext ⟨fun _ => trivial, fun _ => h⟩
@@ -85,13 +84,6 @@ theorem dite_congr {_ : Decidable b} [Decidable c]
 @[simp] theorem ite_false (a b : α) : (if False then a else b) = b := rfl
 @[simp] theorem dite_true {α : Sort u} {t : True → α} {e : ¬ True → α} : (dite True t e) = t True.intro := rfl
 @[simp] theorem dite_false {α : Sort u} {t : False → α} {e : ¬ False → α} : (dite False t e) = e not_false := rfl
-section SimprocHelperLemmas
-set_option simprocs false
-theorem ite_cond_eq_true {α : Sort u} {c : Prop} {_ : Decidable c} (a b : α) (h : c = True) : (if c then a else b) = a := by simp [h]
-theorem ite_cond_eq_false {α : Sort u} {c : Prop} {_ : Decidable c} (a b : α) (h : c = False) : (if c then a else b) = b := by simp [h]
-theorem dite_cond_eq_true {α : Sort u} {c : Prop} {_ : Decidable c} {t : c → α} {e : ¬ c → α} (h : c = True) : (dite c t e) = t (of_eq_true h) := by simp [h]
-theorem dite_cond_eq_false {α : Sort u} {c : Prop} {_ : Decidable c} {t : c → α} {e : ¬ c → α} (h : c = False) : (dite c t e) = e (of_eq_false h) := by simp [h]
-end SimprocHelperLemmas
 @[simp] theorem ite_self {α : Sort u} {c : Prop} {d : Decidable c} (a : α) : ite c a a = a := by cases d <;> rfl
 @[simp] theorem and_self (p : Prop) : (p ∧ p) = p := propext ⟨(·.1), fun h => ⟨h, h⟩⟩
 @[simp] theorem and_true (p : Prop) : (p ∧ True) = p := propext ⟨(·.1), (⟨·, trivial⟩)⟩

src/Init/Simproc.lean

@@ -1,129 +0,0 @@
-/-
-Copyright (c) 2023 Amazon.com, Inc. or its affiliates. All Rights Reserved.
-Released under Apache 2.0 license as described in the file LICENSE.
-Authors: Leonardo de Moura
--/
-prelude
-import Init.NotationExtra
-
-namespace Lean.Parser
-/--
-A user-defined simplification procedure used by the `simp` tactic, and its variants.
-Here is an example.
-```lean
-simproc reduce_add (_ + _) := fun e => do
-  unless (e.isAppOfArity ``HAdd.hAdd 6) do return none
-  let some n ← getNatValue? (e.getArg! 4) | return none
-  let some m ← getNatValue? (e.getArg! 5) | return none
-  return some (.done { expr := mkNatLit (n+m) })
-```
-The `simp` tactic invokes `reduce_add` whenever it finds a term of the form `_ + _`.
-The simplification procedures are stored in an (imperfect) discrimination tree.
-The procedure should **not** assume the term `e` perfectly matches the given pattern.
-The body of a simplification procedure must have type `Simproc`, which is an alias for
-`Expr → SimpM (Option Step)`.
-You can instruct the simplifier to apply the procedure before its sub-expressions
-have been simplified by using the modifier `↓` before the procedure name. Example.
-```lean
-simproc ↓ reduce_add (_ + _) := fun e => ...
-```
-Simplification procedures can be also scoped or local.
--/
-syntax (docComment)? attrKind "simproc " (Tactic.simpPre <|> Tactic.simpPost)? ("[" ident,* "]")? ident " (" term ")" " := " term : command
-
-/--
-A user-defined simplification procedure declaration. To activate this procedure in `simp` tactic,
-we must provide it as an argument, or use the command `attribute` to set its `[simproc]` attribute.
--/
-syntax (docComment)? "simproc_decl " ident " (" term ")" " := " term : command
-
-/--
-A builtin simplification procedure.
--/
-syntax (docComment)? attrKind "builtin_simproc " (Tactic.simpPre <|> Tactic.simpPost)? ("[" ident,* "]")? ident " (" term ")" " := " term : command
-
-/--
-A builtin simplification procedure declaration.
--/
-syntax (docComment)? "builtin_simproc_decl " ident " (" term ")" " := " term : command
-
-/--
-Auxiliary command for associating a pattern with a simplification procedure.
--/
-syntax (name := simprocPattern) "simproc_pattern% " term " => " ident : command
-
-/--
-Auxiliary command for associating a pattern with a builtin simplification procedure.
--/
-syntax (name := simprocPatternBuiltin) "builtin_simproc_pattern% " term " => " ident : command
-
-namespace Attr
-/--
-Auxiliary attribute for simplification procedures.
--/
-syntax (name := simprocAttr) "simproc" (Tactic.simpPre <|> Tactic.simpPost)? : attr
-
-/--
-Auxiliary attribute for symbolic evaluation procedures.
--/
-syntax (name := sevalprocAttr) "sevalproc" (Tactic.simpPre <|> Tactic.simpPost)? : attr
-
-/--
-Auxiliary attribute for builtin simplification procedures.
--/
-syntax (name := simprocBuiltinAttr) "builtin_simproc" (Tactic.simpPre <|> Tactic.simpPost)? : attr
-
-/--
-Auxiliary attribute for builtin symbolic evaluation procedures.
--/
-syntax (name := sevalprocBuiltinAttr) "builtin_sevalproc" (Tactic.simpPre <|> Tactic.simpPost)? : attr
-
-end Attr
-
-macro_rules
-  | `($[$doc?:docComment]? simproc_decl $n:ident ($pattern:term) := $body) => do
-    let simprocType := `Lean.Meta.Simp.Simproc
-    `($[$doc?:docComment]? def $n:ident : $(mkIdent simprocType) := $body
-      simproc_pattern% $pattern => $n)
-
-macro_rules
-  | `($[$doc?:docComment]? builtin_simproc_decl $n:ident ($pattern:term) := $body) => do
-    let simprocType := `Lean.Meta.Simp.Simproc
-    `($[$doc?:docComment]? def $n:ident : $(mkIdent simprocType) := $body
-      builtin_simproc_pattern% $pattern => $n)
-
-macro_rules
-  | `($[$doc?:docComment]? $kind:attrKind simproc $[$pre?]? $[ [ $ids?:ident,* ] ]? $n:ident ($pattern:term) := $body) => do
-     let mut cmds := #[(← `($[$doc?:docComment]? simproc_decl $n ($pattern) := $body))]
-     let pushDefault (cmds : Array (TSyntax `command)) : MacroM (Array (TSyntax `command)) := do
-       return cmds.push (← `(attribute [$kind simproc $[$pre?]?] $n))
-     if let some ids := ids? then
-       for id in ids.getElems do
-         let idName := id.getId
-         let (attrName, attrKey) :=
-           if idName == `simp then
-             (`simprocAttr, "simproc")
-           else if idName == `seval then
-             (`sevalprocAttr, "sevalproc")
-           else
-             let idName := idName.appendAfter "_proc"
-             (`Parser.Attr ++ idName, idName.toString)
-         let attrStx : TSyntax `attr := ⟨mkNode attrName #[mkAtom attrKey, mkOptionalNode pre?]⟩
-         cmds := cmds.push (← `(attribute [$kind $attrStx] $n))
-     else
-       cmds ← pushDefault cmds
-     return mkNullNode cmds
-
-macro_rules
-  | `($[$doc?:docComment]? $kind:attrKind builtin_simproc $[$pre?]? $n:ident ($pattern:term) := $body) => do
-    `($[$doc?:docComment]? builtin_simproc_decl $n ($pattern) := $body
-      attribute [$kind builtin_simproc $[$pre?]?] $n)
-  | `($[$doc?:docComment]? $kind:attrKind builtin_simproc $[$pre?]? [seval] $n:ident ($pattern:term) := $body) => do
-    `($[$doc?:docComment]? builtin_simproc_decl $n ($pattern) := $body
-      attribute [$kind builtin_sevalproc $[$pre?]?] $n)
-  | `($[$doc?:docComment]? $kind:attrKind builtin_simproc $[$pre?]? [simp, seval] $n:ident ($pattern:term) := $body) => do
-    `($[$doc?:docComment]? builtin_simproc_decl $n ($pattern) := $body
-      attribute [$kind builtin_simproc $[$pre?]?] $n
-      attribute [$kind builtin_sevalproc $[$pre?]?] $n)
-
-end Lean.Parser

src/Init/System/FilePath.lean

@@ -101,21 +101,6 @@ def withFileName (p : FilePath) (fname : String) : FilePath :=
   | none => ⟨fname⟩
   | some p => p / fname
 
-/-- Appends the extension `ext` to a path `p`.
-
-`ext` should not contain a leading `.`, as this function adds one.
-If `ext` is the empty string, no `.` is added.
-
-Unlike `System.FilePath.withExtension`, this does not remove any existing extension. -/
-def addExtension (p : FilePath) (ext : String) : FilePath :=
-  match p.fileName with
-  | none => p
-  | some fname => p.withFileName (if ext.isEmpty then fname else fname ++ "." ++ ext)
-
-/-- Replace the current extension in a path `p` with `ext`.
-
-`ext` should not contain a `.`, as this function adds one.
-If `ext` is the empty string, no `.` is added. -/
 def withExtension (p : FilePath) (ext : String) : FilePath :=
   match p.fileStem with
   | none => p

src/Init/System/IO.lean

@@ -117,23 +117,20 @@ opaque asTask (act : BaseIO α) (prio := Task.Priority.default) : BaseIO (Task
 
 /-- See `BaseIO.asTask`. -/
 @[extern "lean_io_map_task"]
-opaque mapTask (f : α → BaseIO β) (t : Task α) (prio := Task.Priority.default) (sync := false) :
-    BaseIO (Task β) :=
+opaque mapTask (f : α → BaseIO β) (t : Task α) (prio := Task.Priority.default) : BaseIO (Task β) :=
   Task.pure <$> f t.get
 
 /-- See `BaseIO.asTask`. -/
 @[extern "lean_io_bind_task"]
-opaque bindTask (t : Task α) (f : α → BaseIO (Task β)) (prio := Task.Priority.default)
-    (sync := false) : BaseIO (Task β) :=
+opaque bindTask (t : Task α) (f : α → BaseIO (Task β)) (prio := Task.Priority.default) : BaseIO (Task β) :=
   f t.get
 
-def mapTasks (f : List α → BaseIO β) (tasks : List (Task α)) (prio := Task.Priority.default)
-    (sync := false) : BaseIO (Task β) :=
+def mapTasks (f : List α → BaseIO β) (tasks : List (Task α)) (prio := Task.Priority.default) : BaseIO (Task β) :=
   go tasks []
 where
   go
     | t::ts, as =>
-      BaseIO.bindTask t (fun a => go ts (a :: as)) prio sync
+      BaseIO.bindTask t (fun a => go ts (a :: as)) prio
     | [], as => f as.reverse |>.asTask prio
 
 end BaseIO
@@ -145,20 +142,16 @@ namespace EIO
   act.toBaseIO.asTask prio
 
 /-- `EIO` specialization of `BaseIO.mapTask`. -/
-@[inline] def mapTask (f : α → EIO ε β) (t : Task α) (prio := Task.Priority.default)
-    (sync := false) : BaseIO (Task (Except ε β)) :=
-  BaseIO.mapTask (fun a => f a |>.toBaseIO) t prio sync
+@[inline] def mapTask (f : α → EIO ε β) (t : Task α) (prio := Task.Priority.default) : BaseIO (Task (Except ε β)) :=
+  BaseIO.mapTask (fun a => f a |>.toBaseIO) t prio
 
 /-- `EIO` specialization of `BaseIO.bindTask`. -/
-@[inline] def bindTask (t : Task α) (f : α → EIO ε (Task (Except ε β)))
-    (prio := Task.Priority.default) (sync := false) : BaseIO (Task (Except ε β)) :=
-  BaseIO.bindTask t (fun a => f a |>.catchExceptions fun e => return Task.pure <| Except.error e)
-    prio sync
+@[inline] def bindTask (t : Task α) (f : α → EIO ε (Task (Except ε β))) (prio := Task.Priority.default) : BaseIO (Task (Except ε β)) :=
+  BaseIO.bindTask t (fun a => f a |>.catchExceptions fun e => return Task.pure <| Except.error e) prio
 
 /-- `EIO` specialization of `BaseIO.mapTasks`. -/
-@[inline] def mapTasks (f : List α → EIO ε β) (tasks : List (Task α))
-    (prio := Task.Priority.default) (sync := false) : BaseIO (Task (Except ε β)) :=
-  BaseIO.mapTasks (fun as => f as |>.toBaseIO) tasks prio sync
+@[inline] def mapTasks (f : List α → EIO ε β) (tasks : List (Task α)) (prio := Task.Priority.default) : BaseIO (Task (Except ε β)) :=
+  BaseIO.mapTasks (fun as => f as |>.toBaseIO) tasks prio
 
 end EIO
 
@@ -191,19 +184,16 @@ def sleep (ms : UInt32) : BaseIO Unit :=
   EIO.asTask act prio
 
 /-- `IO` specialization of `EIO.mapTask`. -/
-@[inline] def mapTask (f : α → IO β) (t : Task α) (prio := Task.Priority.default) (sync := false) :
-    BaseIO (Task (Except IO.Error β)) :=
-  EIO.mapTask f t prio sync
+@[inline] def mapTask (f : α → IO β) (t : Task α) (prio := Task.Priority.default) : BaseIO (Task (Except IO.Error β)) :=
+  EIO.mapTask f t prio
 
 /-- `IO` specialization of `EIO.bindTask`. -/
-@[inline] def bindTask (t : Task α) (f : α → IO (Task (Except IO.Error β)))
-    (prio := Task.Priority.default) (sync := false) : BaseIO (Task (Except IO.Error β)) :=
-  EIO.bindTask t f prio sync
+@[inline] def bindTask (t : Task α) (f : α → IO (Task (Except IO.Error β))) (prio := Task.Priority.default) : BaseIO (Task (Except IO.Error β)) :=
+  EIO.bindTask t f prio
 
 /-- `IO` specialization of `EIO.mapTasks`. -/
-@[inline] def mapTasks (f : List α → IO β) (tasks : List (Task α)) (prio := Task.Priority.default)
-    (sync := false) : BaseIO (Task (Except IO.Error β)) :=
-  EIO.mapTasks f tasks prio sync
+@[inline] def mapTasks (f : List α → IO β) (tasks : List (Task α)) (prio := Task.Priority.default) : BaseIO (Task (Except IO.Error β)) :=
+  EIO.mapTasks f tasks prio
 
 /-- Check if the task's cancellation flag has been set by calling `IO.cancel` or dropping the last reference to the task. -/
 @[extern "lean_io_check_canceled"] opaque checkCanceled : BaseIO Bool

src/Init/System/Platform.lean

@@ -5,7 +5,6 @@ Authors: Leonardo de Moura
 -/
 prelude
 import Init.Data.Nat.Basic
-import Init.Data.String.Basic
 
 namespace System
 namespace Platform
@@ -18,10 +17,5 @@ def isWindows : Bool := getIsWindows ()
 def isOSX : Bool := getIsOSX ()
 def isEmscripten : Bool := getIsEmscripten ()
 
-@[extern "lean_system_platform_target"] opaque getTarget : Unit → String
-
-/-- The LLVM target triple of the current platform. Empty if missing at Lean compile time. -/
-def target : String := getTarget ()
-
 end Platform
 end System

src/Init/Tactics.lean

@@ -39,75 +39,8 @@ be a `let` or function type.
 syntax (name := intro) "intro" notFollowedBy("|") (ppSpace colGt term:max)* : tactic
 
 /--
-Introduces zero or more hypotheses, optionally naming them.
-
-- `intros` is equivalent to repeatedly applying `intro`
-  until the goal is not an obvious candidate for `intro`, which is to say
-  that so long as the goal is a `let` or a pi type (e.g. an implication, function, or universal quantifier),
-  the `intros` tactic will introduce an anonymous hypothesis.
-  This tactic does not unfold definitions.
-
-- `intros x y ...` is equivalent to `intro x y ...`,
-  introducing hypotheses for each supplied argument and unfolding definitions as necessary.
-  Each argument can be either an identifier or a `_`.
-  An identifier indicates a name to use for the corresponding introduced hypothesis,
-  and a `_` indicates that the hypotheses should be introduced anonymously.
-
-## Examples
-
-Basic properties:
-```lean
-def AllEven (f : Nat → Nat) := ∀ n, f n % 2 = 0
-
--- Introduces the two obvious hypotheses automatically
-example : ∀ (f : Nat → Nat), AllEven f → AllEven (fun k => f (k + 1)) := by
-  intros
-  /- Tactic state
-     f✝ : Nat → Nat
-     a✝ : AllEven f✝
-     ⊢ AllEven fun k => f✝ (k + 1) -/
-  sorry
-
--- Introduces exactly two hypotheses, naming only the first
-example : ∀ (f : Nat → Nat), AllEven f → AllEven (fun k => f (k + 1)) := by
-  intros g _
-  /- Tactic state
-     g : Nat → Nat
-     a✝ : AllEven g
-     ⊢ AllEven fun k => g (k + 1) -/
-  sorry
-
--- Introduces exactly three hypotheses, which requires unfolding `AllEven`
-example : ∀ (f : Nat → Nat), AllEven f → AllEven (fun k => f (k + 1)) := by
-  intros f h n
-  /- Tactic state
-     f : Nat → Nat
-     h : AllEven f
-     n : Nat
-     ⊢ (fun k => f (k + 1)) n % 2 = 0 -/
-  apply h
-```
-
-Implications:
-```lean
-example (p q : Prop) : p → q → p := by
-  intros
-  /- Tactic state
-     a✝¹ : p
-     a✝ : q
-     ⊢ p      -/
-  assumption
-```
-
-Let bindings:
-```lean
-example : let n := 1; let k := 2; n + k = 3 := by
-  intros
-  /- n✝ : Nat := 1
-     k✝ : Nat := 2
-     ⊢ n✝ + k✝ = 3 -/
-  rfl
-```
+`intros x...` behaves like `intro x...`, but then keeps introducing (anonymous)
+hypotheses until goal is not of a function type.
 -/
 syntax (name := intros) "intros" (ppSpace colGt (ident <|> hole))* : tactic
 
@@ -335,8 +268,8 @@ macro "rfl'" : tactic => `(tactic| set_option smartUnfolding false in with_unfol
 /--
 `ac_rfl` proves equalities up to application of an associative and commutative operator.
 ```
-instance : Associative (α := Nat) (.+.) := ⟨Nat.add_assoc⟩
-instance : Commutative (α := Nat) (.+.) := ⟨Nat.add_comm⟩
+instance : IsAssociative (α := Nat) (.+.) := ⟨Nat.add_assoc⟩
+instance : IsCommutative (α := Nat) (.+.) := ⟨Nat.add_comm⟩
 
 example (a b c d : Nat) : a + b + c + d = d + (b + c) + a := by ac_rfl
 ```
@@ -422,9 +355,9 @@ Using `rw (config := {occs := .pos L}) [e]`,
 where `L : List Nat`, you can control which "occurrences" are rewritten.
 (This option applies to each rule, so usually this will only be used with a single rule.)
 Occurrences count from `1`.
-At each allowed occurrence, arguments of the rewrite rule `e` may be instantiated,
+At the first occurrence, whether allowed or not,
+arguments of the rewrite rule `e` may be instantiated,
 restricting which later rewrites can be found.
-(Disallowed occurrences do not result in instantiation.)
 `{occs := .neg L}` allows skipping specified occurrences.
 -/
 syntax (name := rewriteSeq) "rewrite" (config)? rwRuleSeq (location)? : tactic
@@ -626,7 +559,7 @@ You can use `with` to provide the variables names for each constructor.
 - `induction e`, where `e` is an expression instead of a variable,
   generalizes `e` in the goal, and then performs induction on the resulting variable.
 - `induction e using r` allows the user to specify the principle of induction that should be used.
-  Here `r` should be a term whose result type must be of the form `C t`,
+  Here `r` should be a theorem whose result type must be of the form `C t`,
   where `C` is a bound variable and `t` is a (possibly empty) sequence of bound variables
 - `induction e generalizing z₁ ... zₙ`, where `z₁ ... zₙ` are variables in the local context,
   generalizes over `z₁ ... zₙ` before applying the induction but then introduces them in each goal.
@@ -634,7 +567,7 @@ You can use `with` to provide the variables names for each constructor.
 - Given `x : Nat`, `induction x with | zero => tac₁ | succ x' ih => tac₂`
   uses tactic `tac₁` for the `zero` case, and `tac₂` for the `succ` case.
 -/
-syntax (name := induction) "induction " term,+ (" using " term)?
+syntax (name := induction) "induction " term,+ (" using " ident)?
   (" generalizing" (ppSpace colGt term:max)+)? (inductionAlts)? : tactic
 
 /-- A `generalize` argument, of the form `term = x` or `h : term = x`. -/
@@ -677,7 +610,7 @@ You can use `with` to provide the variables names for each constructor.
   performs cases on `e` as above, but also adds a hypothesis `h : e = ...` to each hypothesis,
   where `...` is the constructor instance for that particular case.
 -/
-syntax (name := cases) "cases " casesTarget,+ (" using " term)? (inductionAlts)? : tactic
+syntax (name := cases) "cases " casesTarget,+ (" using " ident)? (inductionAlts)? : tactic
 
 /-- `rename_i x_1 ... x_n` renames the last `n` inaccessible names using the given names. -/
 syntax (name := renameI) "rename_i" (ppSpace colGt binderIdent)+ : tactic
@@ -820,7 +753,7 @@ end Tactic
 
 namespace Attr
 /--
-Theorems tagged with the `simp` attribute are used by the simplifier
+Theorems tagged with the `simp` attribute are by the simplifier
 (i.e., the `simp` tactic, and its variants) to simplify expressions occurring in your goals.
 We call theorems tagged with the `simp` attribute "simp theorems" or "simp lemmas".
 Lean maintains a database/index containing all active simp theorems.

src/Lean/Attributes.lean

@@ -330,7 +330,7 @@ private def AttributeExtension.mkInitial : IO AttributeExtensionState := do
 
 unsafe def mkAttributeImplOfConstantUnsafe (env : Environment) (opts : Options) (declName : Name) : Except String AttributeImpl :=
   match env.find? declName with
-  | none      => throw ("unknown constant '" ++ toString declName ++ "'")
+  | none      => throw ("unknow constant '" ++ toString declName ++ "'")
   | some info =>
     match info.type with
     | Expr.const `Lean.AttributeImpl _ => env.evalConst AttributeImpl opts declName

src/Lean/Compiler/LCNF/AlphaEqv.lean

@@ -75,10 +75,10 @@ def eqvLetValue (e₁ e₂ : LetValue) : EqvM Bool := do
           go (i+1)
       else
         x
-      termination_by params₁.size - i
     go 0
   else
     return false
+termination_by go i => params₁.size - i
 
 def sortAlts (alts : Array Alt) : Array Alt :=
   alts.qsort fun
@@ -133,4 +133,4 @@ Return `true` if `c₁` and `c₂` are alpha equivalent.
 def Code.alphaEqv (c₁ c₂ : Code) : Bool :=
   AlphaEqv.eqv c₁ c₂ |>.run {}
 
-end Lean.Compiler.LCNF
+end Lean.Compiler.LCNF

src/Lean/Compiler/LCNF/Specialize.lean

@@ -181,8 +181,8 @@ def expandCodeDecls (decls : Array CodeDecl) (body : LetValue) : CompilerM Expr
       go (i+1) (subst.push value)
     else
       (body.toExpr.abstract xs).instantiateRev subst
-    termination_by values.size - i
   return go 0 #[]
+termination_by go => values.size - i
 
 /--
 Create the "key" that uniquely identifies a code specialization.

src/Lean/Compiler/LCNF/ToLCNF.lean

@@ -658,9 +658,7 @@ where
       visit (f.beta e.getAppArgs)
 
   visitApp (e : Expr) : M Arg := do
-    if let some (args, n, t, v, b) := e.letFunAppArgs? then
-      visitCore <| mkAppN (.letE n t v b (nonDep := true)) args
-    else if let .const declName _ := e.getAppFn then
+    if let .const declName _ := e.getAppFn then
       if declName == ``Quot.lift then
         visitQuotLift e
       else if declName == ``Quot.mk then
@@ -727,8 +725,11 @@ where
       pushElement (.fun funDecl)
       return .fvar funDecl.fvarId
 
-  visitMData (_mdata : MData) (e : Expr) : M Arg := do
-    visit e
+  visitMData (mdata : MData) (e : Expr) : M Arg := do
+    if let some (.app (.lam n t b ..) v) := letFunAnnotation? (.mdata mdata e) then
+      visitLet (.letE n t v b (nonDep := true)) #[]
+    else
+      visit e
 
   visitProj (s : Name) (i : Nat) (e : Expr) : M Arg := do
     match (← visit e) with

src/Lean/Compiler/LCNF/Types.lean

@@ -234,7 +234,7 @@ where
         throwError "invalid instantiateForall, too many parameters"
     else
       return type
-  termination_by ps.size - i
+termination_by go i _ => ps.size - i
 
 /--
 Return `true` if `type` is a predicate.

src/Lean/CoreM.lean

@@ -315,7 +315,7 @@ private def checkUnsupported [Monad m] [MonadEnv m] [MonadError m] (decl : Decla
     | _ => pure ()
 
 register_builtin_option compiler.enableNew : Bool := {
-  defValue := false
+  defValue := true
   group    := "compiler"
   descr    := "(compiler) enable the new code generator, this should have no significant effect on your code but it does help to test the new code generator; unset to only use the old code generator instead"
 }

src/Lean/Data/Array.lean

@@ -1,46 +0,0 @@
-/-
-Copyright (c) 2023 Lean FRO, LLC. All rights reserved.
-Released under Apache 2.0 license as described in the file LICENSE.
-Authors: Joachim Breitner
--/
-
-import Init.Data.Array
-
-namespace Array
-
-/-!
-This module contains utility functions involving Arrays that are useful in a few places
-of the lean code base, but too specialized to live in `Init.Data.Array`, which arguably
-is part of the public, user-facing standard library.
--/
-
-/--
-Given an array `a`, runs `f xᵢ xⱼ` for all `i < j`, removes those entries for which `f` returns
-`false` (and will subsequently skip pairs if one element is removed), and returns the array of
-remaining elements.
-
-This can be used to remove elements from an array where a “better” element, in some partial
-order, exists in the array.
--/
-def filterPairsM {m} [Monad m] {α} (a : Array α) (f : α → α → m (Bool × Bool)) :
-    m (Array α) := do
-  let mut removed := Array.mkArray a.size false
-  let mut numRemoved := 0
-  for h1 : i in [:a.size] do for h2 : j in [i+1:a.size] do
-    unless removed[i]! || removed[j]! do
-      let xi := a[i]
-      let xj := a[j]
-      let (keepi, keepj) ← f xi xj
-      unless keepi do
-        numRemoved := numRemoved + 1
-        removed := removed.set! i true
-      unless keepj do
-        numRemoved := numRemoved + 1
-        removed := removed.set! j true
-  let mut a' := Array.mkEmpty numRemoved
-  for h : i in [:a.size] do
-    unless removed[i]! do
-      a' := a'.push a[i]
-  return a'
-
-end Array

src/Lean/Data/HashMap.lean

@@ -89,7 +89,7 @@ def moveEntries [Hashable α] (i : Nat) (source : Array (AssocList α β)) (targ
      let target                := es.foldl (reinsertAux hash) target
      moveEntries (i+1) source target
   else target
-termination_by source.size - i
+termination_by _ i source _ => source.size - i
 
 def expand [Hashable α] (size : Nat) (buckets : HashMapBucket α β) : HashMapImp α β :=
   let bucketsNew : HashMapBucket α β := ⟨
@@ -227,17 +227,3 @@ def ofListWith (l : List (α × β)) (f : β → β → β) : HashMap α β :=
       match m.find? p.fst with
         | none   => m.insert p.fst p.snd
         | some v => m.insert p.fst $ f v p.snd)
-end Lean.HashMap
-
-/--
-Groups all elements `x`, `y` in `xs` with `key x == key y` into the same array
-`(xs.groupByKey key).find! (key x)`. Groups preserve the relative order of elements in `xs`.
--/
-def Array.groupByKey [BEq α] [Hashable α] (key : β → α) (xs : Array β)
-    : Lean.HashMap α (Array β) := Id.run do
-  let mut groups := ∅
-  for x in xs do
-    let group := groups.findD (key x) #[]
-    groups := groups.erase (key x) -- make `group` referentially unique
-    groups := groups.insert (key x) (group.push x)
-  return groups

src/Lean/Data/HashSet.lean

@@ -80,7 +80,7 @@ def moveEntries [Hashable α] (i : Nat) (source : Array (List α)) (target : Has
      moveEntries (i+1) source target
   else
     target
-termination_by source.size - i
+termination_by _ i source _ => source.size - i
 
 def expand [Hashable α] (size : Nat) (buckets : HashSetBucket α) : HashSetImp α :=
   let bucketsNew : HashSetBucket α := ⟨

src/Lean/Data/Json.lean

@@ -8,4 +8,3 @@ import Lean.Data.Json.Stream
 import Lean.Data.Json.Printer
 import Lean.Data.Json.Parser
 import Lean.Data.Json.FromToJson
-import Lean.Data.Json.Elab

src/Lean/Data/Json/Elab.lean

@@ -1,79 +0,0 @@
-/-
- Copyright (c) 2022 E.W.Ayers. All rights reserved.
- Released under Apache 2.0 license as described in the file LICENSE.
- Authors: E.W.Ayers, Wojciech Nawrocki
--/
-import Lean.Data.Json.FromToJson
-import Lean.Syntax
-
-/-!
-# JSON-like syntax for Lean.
-
-Now you can write
-
-```lean
-open Lean.Json
-
-#eval json% {
-  hello : "world",
-  cheese : ["edam", "cheddar", {kind : "spicy", rank : 100.2}],
-  lemonCount : 100e30,
-  isCool : true,
-  isBug : null,
-  lookACalc: $(23 + 54 * 2)
-}
-```
--/
-
-namespace Lean.Json
-
-/-- Json syntactic category -/
-declare_syntax_cat json (behavior := symbol)
-/-- Json null value syntax. -/
-syntax "null" : json
-/-- Json true value syntax. -/
-syntax "true" : json
-/-- Json false value syntax. -/
-syntax "false" : json
-/-- Json string syntax. -/
-syntax str : json
-/-- Json number negation syntax for ordinary numbers. -/
-syntax "-"? num : json
-/-- Json number negation syntax for scientific numbers. -/
-syntax "-"? scientific : json
-/-- Json array syntax. -/
-syntax "[" json,* "]" : json
-/-- Json identifier syntax. -/
-syntax jsonIdent := ident <|> str
-/-- Json key/value syntax. -/
-syntax jsonField := jsonIdent ": " json
-/-- Json object syntax. -/
-syntax "{" jsonField,* "}" : json
-/-- Allows to use Json syntax in a Lean file. -/
-syntax "json% " json : term
-
-
-macro_rules
-  | `(json% null)           => `(Lean.Json.null)
-  | `(json% true)           => `(Lean.Json.bool Bool.true)
-  | `(json% false)          => `(Lean.Json.bool Bool.false)
-  | `(json% $n:str)         => `(Lean.Json.str $n)
-  | `(json% $n:num)         => `(Lean.Json.num $n)
-  | `(json% $n:scientific)  => `(Lean.Json.num $n)
-  | `(json% -$n:num)        => `(Lean.Json.num (-$n))
-  | `(json% -$n:scientific) => `(Lean.Json.num (-$n))
-  | `(json% [$[$xs],*])     => `(Lean.Json.arr #[$[json% $xs],*])
-  | `(json% {$[$ks:jsonIdent : $vs:json],*}) => do
-    let ks : Array (TSyntax `term) ← ks.mapM fun
-      | `(jsonIdent| $k:ident) => pure (k.getId |> toString |> quote)
-      | `(jsonIdent| $k:str)   => pure k
-      | _                     => Macro.throwUnsupported
-    `(Lean.Json.mkObj [$[($ks, json% $vs)],*])
-  | `(json% $stx)           =>
-    if stx.raw.isAntiquot then
-      let stx := ⟨stx.raw.getAntiquotTerm⟩
-      `(Lean.toJson $stx)
-    else
-      Macro.throwUnsupported
-
-end Lean.Json

src/Lean/Data/Lsp/Basic.lean

@@ -78,38 +78,6 @@ structure Command where
   arguments? : Option (Array Json) := none
   deriving ToJson, FromJson
 
-/-- A snippet is a string that gets inserted into a document,
-and can afterwards be edited by the user in a structured way.
-
-Snippets contain instructions that
-specify how this structured editing should proceed.
-They are expressed in a domain-specific language
-based on one from TextMate,
-including the following constructs:
-- Designated positions for subsequent user input,
-  called "tab stops" after their most frequently-used keybinding.
-  They are denoted with `$1`, `$2`, and so forth.
-  `$0` denotes where the cursor should be positioned after all edits are completed,
-  defaulting to the end of the string.
-  Snippet tab stops are unrelated to tab stops used for indentation.
-- Tab stops with default values, called _placeholders_, written `${1:default}`.
-  The default may itself contain a tab stop or a further placeholder
-  and multiple options to select from may be provided
-  by surrounding them with `|`s and separating them with `,`,
-  as in `${1|if $2 then $3 else $4,if let $2 := $3 then $4 else $5|}`.
-- One of a set of predefined variables that are replaced with their values.
-  This includes the current line number (`$TM_LINE_NUMBER`)
-  or the text that was selected when the snippet was invoked (`$TM_SELECTED_TEXT`).
-- Formatting instructions to modify variables using regular expressions
-  or a set of predefined filters.
-
-The full syntax and semantics of snippets,
-including the available variables and the rules for escaping control characters,
-are described in the [LSP specification](https://microsoft.github.io/language-server-protocol/specifications/lsp/3.17/specification/#snippet_syntax). -/
-structure SnippetString where
-  value : String
-  deriving ToJson, FromJson
-
 /-- A textual edit applicable to a text document.
 
 [reference](https://microsoft.github.io/language-server-protocol/specifications/lsp/3.17/specification/#textEdit) -/
@@ -119,21 +87,6 @@ structure TextEdit where
   range : Range
   /-- The string to be inserted. For delete operations use an empty string. -/
   newText : String
-  /-- If this field is present and the editor supports it,
-  `newText` is ignored
-  and an interactive snippet edit is performed instead.
-
-  The use of snippets in `TextEdit`s
-  is a Lean-specific extension to the LSP standard,
-  so `newText` should still be set to a correct value
-  as fallback in case the editor does not support this feature.
-  Even editors that support snippets may not always use them;
-  for instance, if the file is not already open,
-  VS Code will perform a normal text edit in the background instead. -/
-  /- NOTE: Similar functionality may be added to LSP in the future:
-  see [issue #592](https://github.com/microsoft/language-server-protocol/issues/592).
-  If such an addition occurs, this field should be deprecated. -/
-  leanExtSnippet? : Option SnippetString := none
   /-- Identifier for annotated edit.
 
     `WorkspaceEdit` has a `changeAnnotations` field that maps these identifiers to a `ChangeAnnotation`.

src/Lean/Data/Lsp/Capabilities.lean

@@ -74,7 +74,6 @@ structure ServerCapabilities where
   declarationProvider       : Bool                           := false
   typeDefinitionProvider    : Bool                           := false
   referencesProvider        : Bool                           := false
-  callHierarchyProvider     : Bool                           := false
   renameProvider?           : Option RenameOptions           := none
   workspaceSymbolProvider   : Bool                           := false
   foldingRangeProvider      : Bool                           := false

src/Lean/Data/Lsp/Internal.lean

@@ -8,8 +8,6 @@ Authors: Joscha Mennicken
 import Lean.Expr
 import Lean.Data.Lsp.Basic
 
-set_option linter.missingDocs true -- keep it documented
-
 /-! This file contains types for communication between the watchdog and the
 workers. These messages are not visible externally to users of the LSP server.
 -/
@@ -19,27 +17,17 @@ namespace Lean.Lsp
 /-! Most reference-related types have custom FromJson/ToJson implementations to
 reduce the size of the resulting JSON. -/
 
-/--
-Identifier of a reference.
--/
 inductive RefIdent where
-  /-- Named identifier. These are used in all references that are globally available. -/
   | const : Name → RefIdent
-  /-- Unnamed identifier. These are used for all local references. -/
-  | fvar  : FVarId → RefIdent
+  | fvar : FVarId → RefIdent
   deriving BEq, Hashable, Inhabited
 
 namespace RefIdent
 
-/-- Converts the reference identifier to a string by prefixing it with a symbol. -/
 def toString : RefIdent → String
   | RefIdent.const n => s!"c:{n}"
   | RefIdent.fvar id => s!"f:{id.name}"
 
-/--
-Converts the string representation of a reference identifier back to a reference identifier.
-The string representation must have been created by `RefIdent.toString`.
--/
 def fromString (s : String) : Except String RefIdent := do
   let sPrefix := s.take 2
   let sName := s.drop 2
@@ -55,92 +43,33 @@ def fromString (s : String) : Except String RefIdent := do
     | "f:" => return RefIdent.fvar <| FVarId.mk name
     | _ => throw "string must start with 'c:' or 'f:'"
 
-instance : FromJson RefIdent where
-  fromJson?
-    | (s : String) => fromString s
-    | j => Except.error s!"expected a String, got {j}"
-
-instance : ToJson RefIdent where
-  toJson ident := toString ident
-
 end RefIdent
 
-/-- Information about the declaration surrounding a reference. -/
-structure RefInfo.ParentDecl where
-  /-- Name of the declaration surrounding a reference. -/
-  name           : Name
-  /-- Range of the declaration surrounding a reference. -/
-  range          : Lsp.Range
-  /-- Selection range of the declaration surrounding a reference. -/
-  selectionRange : Lsp.Range
-  deriving ToJson
-
-/--
-Denotes the range of a reference, as well as the parent declaration of the reference.
-If the reference is itself a declaration, then it contains no parent declaration.
--/
-structure RefInfo.Location where
-  /-- Range of the reference. -/
-  range       : Lsp.Range
-  /-- Parent declaration of the reference. `none` if the reference is itself a declaration. -/
-  parentDecl? : Option RefInfo.ParentDecl
-
-/-- Definition site and usage sites of a reference. Obtained from `Lean.Server.RefInfo`. -/
 structure RefInfo where
-  /-- Definition site of the reference. May be `none` when we cannot find a definition site. -/
-  definition? : Option RefInfo.Location
-  /-- Usage sites of the reference. -/
-  usages      : Array RefInfo.Location
+  definition : Option Lsp.Range
+  usages : Array Lsp.Range
 
 instance : ToJson RefInfo where
   toJson i :=
     let rangeToList (r : Lsp.Range) : List Nat :=
       [r.start.line, r.start.character, r.end.line, r.end.character]
-    let parentDeclToList (d : RefInfo.ParentDecl) : List Json :=
-      let name := d.name.toString |> toJson
-      let range := rangeToList d.range |>.map toJson
-      let selectionRange := rangeToList d.selectionRange |>.map toJson
-      [name] ++ range ++ selectionRange
-    let locationToList (l : RefInfo.Location) : List Json :=
-      let range := rangeToList l.range |>.map toJson
-      let parentDecl := l.parentDecl?.map parentDeclToList |>.getD []
-      range ++ parentDecl
     Json.mkObj [
-      ("definition", toJson $ i.definition?.map locationToList),
-      ("usages", toJson $ i.usages.map locationToList)
+      ("definition", toJson $ i.definition.map rangeToList),
+      ("usages", toJson $ i.usages.map rangeToList)
     ]
 
 instance : FromJson RefInfo where
   fromJson? j := do
-    let toRange : List Nat → Except String Lsp.Range
+    let listToRange (l : List Nat) : Except String Lsp.Range := match l with
       | [sLine, sChar, eLine, eChar] => pure ⟨⟨sLine, sChar⟩, ⟨eLine, eChar⟩⟩
-      | l => throw s!"Expected list of length 4, not {l.length}"
-    let toParentDecl (a : Array Json) : Except String RefInfo.ParentDecl := do
-      let name := String.toName <| ← fromJson? a[0]!
-      let range ← a[1:5].toArray.toList |>.mapM fromJson?
-      let range ← toRange range
-      let selectionRange ← a[5:].toArray.toList |>.mapM fromJson?
-      let selectionRange ← toRange selectionRange
-      return ⟨name, range, selectionRange⟩
-    let toLocation (l : List Json) : Except String RefInfo.Location := do
-      let l := l.toArray
-      if l.size != 4 && l.size != 13 then
-        .error "Expected list of length 4 or 13, not {l.size}"
-      let range ← l[:4].toArray.toList |>.mapM fromJson?
-      let range ← toRange range
-      if l.size == 13 then
-        let parentDecl ← toParentDecl l[4:].toArray
-        return ⟨range, parentDecl⟩
-      else
-        return ⟨range, none⟩
-
-    let definition? ← j.getObjValAs? (Option $ List Json) "definition"
-    let definition? ← match definition? with
+      | _ => throw s!"Expected list of length 4, not {l.length}"
+    let definition ← j.getObjValAs? (Option $ List Nat) "definition"
+    let definition ← match definition with
       | none => pure none
-      | some list => some <$> toLocation list
-    let usages ← j.getObjValAs? (Array $ List Json) "usages"
-    let usages ← usages.mapM toLocation
-    pure { definition?, usages }
+      | some list => some <$> listToRange list
+    let usages ← j.getObjValAs? (Array $ List Nat) "usages"
+    let usages ← usages.mapM listToRange
+    pure { definition, usages }
 
 /-- References from a single module/file -/
 def ModuleRefs := HashMap RefIdent RefInfo
@@ -159,8 +88,7 @@ instance : FromJson ModuleRefs where
 Contains the file's definitions and references. -/
 structure LeanIleanInfoParams where
   /-- Version of the file these references are from. -/
-  version    : Nat
-  /-- All references for the file. -/
+  version : Nat
   references : ModuleRefs
   deriving FromJson, ToJson
 

src/Lean/Data/Lsp/LanguageFeatures.lean

@@ -36,16 +36,16 @@ instance : FromJson CompletionItemKind where
 
 structure InsertReplaceEdit where
   newText : String
-  insert  : Range
+  insert : Range
   replace : Range
   deriving FromJson, ToJson
 
 structure CompletionItem where
-  label          : String
-  detail?        : Option String := none
+  label : String
+  detail? : Option String := none
   documentation? : Option MarkupContent := none
-  kind?          : Option CompletionItemKind := none
-  textEdit?      : Option InsertReplaceEdit := none
+  kind? : Option CompletionItemKind := none
+  textEdit? : Option InsertReplaceEdit := none
   /-
   tags? : CompletionItemTag[]
   deprecated? : boolean
@@ -63,7 +63,7 @@ structure CompletionItem where
 
 structure CompletionList where
   isIncomplete : Bool
-  items        : Array CompletionItem
+  items : Array CompletionItem
   deriving FromJson, ToJson
 
 structure CompletionParams extends TextDocumentPositionParams where
@@ -74,7 +74,7 @@ structure Hover where
   /- NOTE we should also accept MarkedString/MarkedString[] here
   but they are deprecated, so maybe can get away without. -/
   contents : MarkupContent
-  range?   : Option Range := none
+  range? : Option Range := none
   deriving ToJson, FromJson
 
 structure HoverParams extends TextDocumentPositionParams
@@ -153,76 +153,45 @@ inductive SymbolKind where
   | event
   | operator
   | typeParameter
-  deriving BEq, Hashable, Inhabited
-
-instance : FromJson SymbolKind where
-  fromJson?
-    | 1  => .ok .file
-    | 2  => .ok .module
-    | 3  => .ok .namespace
-    | 4  => .ok .package
-    | 5  => .ok .class
-    | 6  => .ok .method
-    | 7  => .ok .property
-    | 8  => .ok .field
-    | 9  => .ok .constructor
-    | 10 => .ok .enum
-    | 11 => .ok .interface
-    | 12 => .ok .function
-    | 13 => .ok .variable
-    | 14 => .ok .constant
-    | 15 => .ok .string
-    | 16 => .ok .number
-    | 17 => .ok .boolean
-    | 18 => .ok .array
-    | 19 => .ok .object
-    | 20 => .ok .key
-    | 21 => .ok .null
-    | 22 => .ok .enumMember
-    | 23 => .ok .struct
-    | 24 => .ok .event
-    | 25 => .ok .operator
-    | 26 => .ok .typeParameter
-    | j  => .error s!"invalid symbol kind {j}"
 
 instance : ToJson SymbolKind where
-  toJson
-    | .file          => 1
-    | .module        => 2
-    | .namespace     => 3
-    | .package       => 4
-    | .class         => 5
-    | .method        => 6
-    | .property      => 7
-    | .field         => 8
-    | .constructor   => 9
-    | .enum          => 10
-    | .interface     => 11
-    | .function      => 12
-    | .variable      => 13
-    | .constant      => 14
-    | .string        => 15
-    | .number        => 16
-    | .boolean       => 17
-    | .array         => 18
-    | .object        => 19
-    | .key           => 20
-    | .null          => 21
-    | .enumMember    => 22
-    | .struct        => 23
-    | .event         => 24
-    | .operator      => 25
-    | .typeParameter => 26
+ toJson
+   | SymbolKind.file => 1
+   | SymbolKind.module => 2
+   | SymbolKind.namespace => 3
+   | SymbolKind.package => 4
+   | SymbolKind.class => 5
+   | SymbolKind.method => 6
+   | SymbolKind.property => 7
+   | SymbolKind.field => 8
+   | SymbolKind.constructor => 9
+   | SymbolKind.enum => 10
+   | SymbolKind.interface => 11
+   | SymbolKind.function => 12
+   | SymbolKind.variable => 13
+   | SymbolKind.constant => 14
+   | SymbolKind.string => 15
+   | SymbolKind.number => 16
+   | SymbolKind.boolean => 17
+   | SymbolKind.array => 18
+   | SymbolKind.object => 19
+   | SymbolKind.key => 20
+   | SymbolKind.null => 21
+   | SymbolKind.enumMember => 22
+   | SymbolKind.struct => 23
+   | SymbolKind.event => 24
+   | SymbolKind.operator => 25
+   | SymbolKind.typeParameter => 26
 
 structure DocumentSymbolAux (Self : Type) where
-  name           : String
-  detail?        : Option String := none
-  kind           : SymbolKind
+  name : String
+  detail? : Option String := none
+  kind : SymbolKind
   -- tags? : Array SymbolTag
-  range          : Range
+  range : Range
   selectionRange : Range
-  children?      : Option (Array Self) := none
-  deriving FromJson, ToJson
+  children? : Option (Array Self) := none
+  deriving ToJson
 
 inductive DocumentSymbol where
   | mk (sym : DocumentSymbolAux DocumentSymbol)
@@ -243,56 +212,18 @@ instance : ToJson DocumentSymbolResult where
 
 inductive SymbolTag where
   | deprecated
-  deriving BEq, Hashable, Inhabited
-
-instance : FromJson SymbolTag where
-  fromJson?
-    | 1 => .ok .deprecated
-    | j => .error s!"unknown symbol tag {j}"
 
 instance : ToJson SymbolTag where
-  toJson
-    | .deprecated => 1
+ toJson
+   | SymbolTag.deprecated => 1
 
 structure SymbolInformation where
-  name           : String
-  kind           : SymbolKind
-  tags           : Array SymbolTag := #[]
-  location       : Location
+  name : String
+  kind : SymbolKind
+  tags : Array SymbolTag := #[]
+  location : Location
   containerName? : Option String := none
-  deriving FromJson, ToJson
-
-structure CallHierarchyPrepareParams extends TextDocumentPositionParams
-  deriving FromJson, ToJson
-
-structure CallHierarchyItem where
-  name           : String
-  kind           : SymbolKind
-  tags?          : Option (Array SymbolTag) := none
-  detail?        : Option String := none
-  uri            : DocumentUri
-  range          : Range
-  selectionRange : Range
-  -- data? : Option unknown
-  deriving FromJson, ToJson, BEq, Hashable, Inhabited
-
-structure CallHierarchyIncomingCallsParams where
-  item : CallHierarchyItem
-  deriving FromJson, ToJson
-
-structure CallHierarchyIncomingCall where
-  «from»     : CallHierarchyItem
-  fromRanges : Array Range
-  deriving FromJson, ToJson, Inhabited
-
-structure CallHierarchyOutgoingCallsParams where
-  item : CallHierarchyItem
-  deriving FromJson, ToJson
-
-structure CallHierarchyOutgoingCall where
-  to         : CallHierarchyItem
-  fromRanges : Array Range
-  deriving FromJson, ToJson, Inhabited
+  deriving ToJson
 
 inductive SemanticTokenType where
   -- Used by Lean
@@ -373,14 +304,14 @@ example {v : SemanticTokenModifier} : open SemanticTokenModifier in
   cases v <;> native_decide
 
 structure SemanticTokensLegend where
-  tokenTypes     : Array String
+  tokenTypes : Array String
   tokenModifiers : Array String
   deriving FromJson, ToJson
 
 structure SemanticTokensOptions where
   legend : SemanticTokensLegend
-  range  : Bool
-  full   : Bool /- | {
+  range : Bool
+  full : Bool /- | {
     delta?: boolean;
   } -/
   deriving FromJson, ToJson
@@ -391,12 +322,12 @@ structure SemanticTokensParams where
 
 structure SemanticTokensRangeParams where
   textDocument : TextDocumentIdentifier
-  range        : Range
+  range : Range
   deriving FromJson, ToJson
 
 structure SemanticTokens where
   resultId? : Option String := none
-  data      : Array Nat
+  data : Array Nat
   deriving FromJson, ToJson
 
 structure FoldingRangeParams where
@@ -412,12 +343,12 @@ instance : ToJson FoldingRangeKind where
   toJson
     | FoldingRangeKind.comment => "comment"
     | FoldingRangeKind.imports => "imports"
-    | FoldingRangeKind.region  => "region"
+    | FoldingRangeKind.region => "region"
 
 structure FoldingRange where
   startLine : Nat
-  endLine   : Nat
-  kind?     : Option FoldingRangeKind := none
+  endLine : Nat
+  kind? : Option FoldingRangeKind := none
   deriving ToJson
 
 structure RenameOptions where

src/Lean/Data/Lsp/Utf16.lean

@@ -8,7 +8,6 @@ import Init.Data.String
 import Init.Data.Array
 import Lean.Data.Lsp.Basic
 import Lean.Data.Position
-import Lean.DeclarationRange
 
 /-! LSP uses UTF-16 for indexing, so we need to provide some primitives
 to interact with Lean strings using UTF-16 indices. -/
@@ -63,37 +62,24 @@ end String
 namespace Lean
 namespace FileMap
 
-private def lineStartPos (text : FileMap) (line : Nat) : String.Pos :=
-  if h : line < text.positions.size then
-    text.positions.get ⟨line, h⟩
-  else if text.positions.isEmpty then
-    0
-  else
-    text.positions.back
-
 /-- Computes an UTF-8 offset into `text.source`
 from an LSP-style 0-indexed (ln, col) position. -/
 def lspPosToUtf8Pos (text : FileMap) (pos : Lsp.Position) : String.Pos :=
-  let lineStartPos := lineStartPos text pos.line
-  let chr := text.source.utf16PosToCodepointPosFrom pos.character lineStartPos
-  text.source.codepointPosToUtf8PosFrom lineStartPos chr
+  let colPos :=
+    if h : pos.line < text.positions.size then
+      text.positions.get ⟨pos.line, h⟩
+    else if text.positions.isEmpty then
+      0
+    else
+      text.positions.back
+  let chr := text.source.utf16PosToCodepointPosFrom pos.character colPos
+  text.source.codepointPosToUtf8PosFrom colPos chr
 
 def leanPosToLspPos (text : FileMap) : Lean.Position → Lsp.Position
-  | ⟨line, col⟩ =>
-    ⟨line - 1, text.source.codepointPosToUtf16PosFrom col (lineStartPos text (line - 1))⟩
+  | ⟨ln, col⟩ => ⟨ln-1, text.source.codepointPosToUtf16PosFrom col (text.positions.get! $ ln - 1)⟩
 
 def utf8PosToLspPos (text : FileMap) (pos : String.Pos) : Lsp.Position :=
   text.leanPosToLspPos (text.toPosition pos)
 
 end FileMap
 end Lean
-
-/--
-Convert the Lean `DeclarationRange` to an LSP `Range` by turning the 1-indexed line numbering into a
-0-indexed line numbering and converting the character offset within the line to a UTF-16 indexed
-offset.
--/
-def Lean.DeclarationRange.toLspRange (r : Lean.DeclarationRange) : Lsp.Range := {
-  start := ⟨r.pos.line - 1, r.charUtf16⟩
-  «end» := ⟨r.endPos.line - 1, r.endCharUtf16⟩
-}

src/Lean/Data/Name.lean

@@ -96,12 +96,6 @@ def quickCmp (n₁ n₂ : Name) : Ordering :=
 def quickLt (n₁ n₂ : Name) : Bool :=
   quickCmp n₁ n₂ == Ordering.lt
 
-/-- Returns true if the name has any numeric components. -/
-def hasNum : Name → Bool
-  | .anonymous => false
-  | .str p _ => p.hasNum
-  | .num _ _ => true
-
 /-- The frontend does not allow user declarations to start with `_` in any of its parts.
    We use name parts starting with `_` internally to create auxiliary names (e.g., `_private`). -/
 def isInternal : Name → Bool
@@ -109,17 +103,6 @@ def isInternal : Name → Bool
   | num p _ => isInternal p
   | _       => false
 
-/--
-The frontend does not allow user declarations to start with `_` in any of its parts.
-We use name parts starting with `_` internally to create auxiliary names (e.g., `_private`).
-
-This function checks if any component of the name starts with `_`, or is numeric.
--/
-def isInternalOrNum : Name → Bool
-  | .str p s => s.get 0 == '_' || isInternalOrNum p
-  | .num _ _ => true
-  | _       => false
-
 /--
 Checks whether the name is an implementation-detail hypothesis name.
 

src/Lean/Data/Position.lean

@@ -29,16 +29,9 @@ instance : ToExpr Position where
 
 end Position
 
-/-- Content of a file together with precalculated positions of newlines. -/
 structure FileMap where
-  /-- The content of the file. -/
   source    : String
-  /-- The positions of newline characters.
-  The first entry is always `0` and the last always the index of the last character.
-  In particular, if the last character is a newline, that index will appear twice. -/
   positions : Array String.Pos
-  /-- The line numbers associated with the `positions`.
-  Has the same length as `positions` and is always of the form `#[1, 2, …, n-1, n-1]`. -/
   lines     : Array Nat
   deriving Inhabited
 

src/Lean/Data/RBMap.lean

@@ -159,7 +159,7 @@ def appendTrees :  RBNode α β → RBNode α β → RBNode α β
      | bc                   => balLeft a kx vx (node black bc ky vy d)
    | a, node red b kx vx c   => node red (appendTrees a b) kx vx c
    | node red a kx vx b,   c => node red a kx vx (appendTrees b c)
-termination_by x y => x.size + y.size
+termination_by _ x y => x.size + y.size
 
 section Erase
 

src/Lean/Data/SMap.lean

@@ -97,7 +97,7 @@ def toList (m : SMap α β) : List (α × β) :=
 
 end SMap
 
-def _root_.List.toSMap [BEq α] [Hashable α] (es : List (α × β)) : SMap α β :=
+def List.toSMap [BEq α] [Hashable α] (es : List (α × β)) : SMap α β :=
   es.foldl (init := {}) fun s (a, b) => s.insert a b
 
 instance {_ : BEq α} {_ : Hashable α} [Repr α] [Repr β] : Repr (SMap α β) where

src/Lean/DocString.lean

@@ -36,12 +36,13 @@ where
        if it.atEnd then r
        else if it.curr == ' ' || it.curr == '\t' then consumeSpaces n it.next r
        else saveLine it r
-  termination_by (it, 1)
   saveLine (it : String.Iterator) (r : String) : String :=
     if it.atEnd then r
     else if it.curr == '\n' then consumeSpaces n it.next (r.push '\n')
     else saveLine it.next (r.push it.curr)
-  termination_by (it, 0)
+termination_by
+  consumeSpaces n it r => (it, 1)
+  saveLine it r => (it, 0)
 
 def removeLeadingSpaces (s : String) : String :=
   let n := findLeadingSpacesSize s

src/Lean/Elab/App.lean

@@ -690,10 +690,10 @@ builtin_initialize elabAsElim : TagAttribute ←
     (applicationTime := .afterCompilation)
     fun declName => do
       let go : MetaM Unit := do
+        discard <| getElimInfo declName
         let info ← getConstInfo declName
         if (← hasOptAutoParams info.type) then
           throwError "[elab_as_elim] attribute cannot be used in declarations containing optional and auto parameters"
-        discard <| getElimInfo declName
       go.run' {} {}
 
 /-! # Eliminator-like function application elaborator -/
@@ -937,7 +937,6 @@ def elabAppArgs (f : Expr) (namedArgs : Array NamedArg) (args : Array Arg)
 where
   /-- Return `some info` if we should elaborate as an eliminator. -/
   elabAsElim? : TermElabM (Option ElimInfo) := do
-    unless (← read).heedElabAsElim do return none
     if explicit || ellipsis then return none
     let .const declName _ := f | return none
     unless (← shouldElabAsElim declName) do return none
@@ -958,7 +957,8 @@ where
   The idea is that the contribute to motive inference. See comment at `ElamElim.Context.extraArgsPos`.
   -/
   getElabAsElimExtraArgsPos (elimInfo : ElimInfo) : MetaM (Array Nat) := do
-    forallTelescope elimInfo.elimType fun xs type => do
+    let cinfo ← getConstInfo elimInfo.name
+    forallTelescope cinfo.type fun xs type => do
       let resultArgs := type.getAppArgs
       let mut extraArgsPos := #[]
       for i in [:xs.size] do

src/Lean/Elab/Binders.lean

@@ -6,7 +6,6 @@ Authors: Leonardo de Moura
 import Lean.Elab.Quotation.Precheck
 import Lean.Elab.Term
 import Lean.Elab.BindersUtil
-import Lean.Elab.PreDefinition.WF.TerminationHint
 
 namespace Lean.Elab.Term
 open Meta
@@ -571,8 +570,7 @@ def expandMatchAltsIntoMatchTactic (ref : Syntax) (matchAlts : Syntax) : MacroM
 -/
 def expandMatchAltsWhereDecls (matchAltsWhereDecls : Syntax) : MacroM Syntax :=
   let matchAlts     := matchAltsWhereDecls[0]
-  -- matchAltsWhereDecls[1] is the termination hints, collected elsewhere
-  let whereDeclsOpt := matchAltsWhereDecls[2]
+  let whereDeclsOpt := matchAltsWhereDecls[1]
   let rec loop (i : Nat) (discrs : Array Syntax) : MacroM Syntax :=
     match i with
     | 0   => do
@@ -670,11 +668,12 @@ def elabLetDeclAux (id : Syntax) (binders : Array Syntax) (typeStx : Syntax) (va
       let body ← instantiateMVars body
       mkLetFVars #[x] body (usedLetOnly := usedLetOnly)
   else
-    withLocalDecl id.getId (kind := kind) .default type fun x => do
+    let f ← withLocalDecl id.getId (kind := kind) .default type fun x => do
       addLocalVarInfo id x
       let body ← elabTermEnsuringType body expectedType?
       let body ← instantiateMVars body
-      mkLetFun x val body
+      mkLambdaFVars #[x] body (usedLetOnly := false)
+    pure <| mkLetFunAnnotation (mkApp f val)
   if elabBodyFirst then
     forallBoundedTelescope type binders.size fun xs type => do
       -- the original `fvars` from above are gone, so add back info manually

src/Lean/Elab/BuiltinNotation.lean

@@ -241,8 +241,7 @@ where
 
 /--
   Helper method for elaborating terms such as `(.+.)` where a constant name is expected.
-  This method is usually used to implement tactics that take function names as arguments
-  (e.g., `simp`).
+  This method is usually used to implement tactics that function names as arguments (e.g., `simp`).
 -/
 def elabCDotFunctionAlias? (stx : Term) : TermElabM (Option Expr) := do
   let some stx ← liftMacroM <| expandCDotArg? stx | pure none

src/Lean/Elab/Command.lean

@@ -238,11 +238,10 @@ private def mkInfoTree (elaborator : Name) (stx : Syntax) (trees : PersistentArr
   let s ← get
   let scope := s.scopes.head!
   let tree := InfoTree.node (Info.ofCommandInfo { elaborator, stx }) trees
-  let ctx := PartialContextInfo.commandCtx {
+  return InfoTree.context {
     env := s.env, fileMap := ctx.fileMap, mctx := {}, currNamespace := scope.currNamespace,
     openDecls := scope.openDecls, options := scope.opts, ngen := s.ngen
-  }
-  return InfoTree.context ctx tree
+  } tree
 
 private def elabCommandUsing (s : State) (stx : Syntax) : List (KeyedDeclsAttribute.AttributeEntry CommandElab) → CommandElabM Unit
   | []                => withInfoTreeContext (mkInfoTree := mkInfoTree `no_elab stx) <| throwError "unexpected syntax{indentD stx}"

src/Lean/Elab/Declaration.lean

@@ -187,6 +187,15 @@ def elabClassInductive (modifiers : Modifiers) (stx : Syntax) : CommandElabM Uni
   let v ← classInductiveSyntaxToView modifiers stx
   elabInductiveViews #[v]
 
+def getTerminationHints (stx : Syntax) : TerminationHints :=
+  let decl := stx[1]
+  let k := decl.getKind
+  if k == ``Parser.Command.def || k == ``Parser.Command.abbrev || k == ``Parser.Command.theorem || k == ``Parser.Command.instance then
+    let args := decl.getArgs
+    { terminationBy? := args[args.size - 2]!.getOptional?, decreasingBy? := args[args.size - 1]!.getOptional? }
+  else
+    {}
+
 @[builtin_command_elab declaration]
 def elabDeclaration : CommandElab := fun stx => do
   match (← liftMacroM <| expandDeclNamespace? stx) with
@@ -210,7 +219,7 @@ def elabDeclaration : CommandElab := fun stx => do
       let modifiers ← elabModifiers stx[0]
       elabStructure modifiers decl
     else if isDefLike decl then
-      elabMutualDef #[stx]
+      elabMutualDef #[stx] (getTerminationHints stx)
     else
       throwError "unexpected declaration"
 
@@ -323,12 +332,23 @@ def expandMutualPreamble : Macro := fun stx =>
 
 @[builtin_command_elab «mutual»]
 def elabMutual : CommandElab := fun stx => do
+  let hints := { terminationBy? := stx[3].getOptional?, decreasingBy? := stx[4].getOptional? }
   if isMutualInductive stx then
+    if let some bad := hints.terminationBy? then
+      throwErrorAt bad "invalid 'termination_by' in mutually inductive datatype declaration"
+    if let some bad := hints.decreasingBy? then
+      throwErrorAt bad "invalid 'decreasing_by' in mutually inductive datatype declaration"
     elabMutualInductive stx[1].getArgs
   else if isMutualDef stx then
-    elabMutualDef stx[1].getArgs
+    for arg in stx[1].getArgs do
+      let argHints := getTerminationHints arg
+      if let some bad := argHints.terminationBy? then
+        throwErrorAt bad "invalid 'termination_by' in 'mutual' block, it must be used after the 'end' keyword"
+      if let some bad := argHints.decreasingBy? then
+        throwErrorAt bad "invalid 'decreasing_by' in 'mutual' block, it must be used after the 'end' keyword"
+    elabMutualDef stx[1].getArgs hints
   else
-    throwError "invalid mutual block: either all elements of the block must be inductive declarations, or they must all be definitions/theorems/abbrevs"
+    throwError "invalid mutual block"
 
 /- leading_parser "attribute " >> "[" >> sepBy1 (eraseAttr <|> Term.attrInstance) ", " >> "]" >> many1 ident -/
 @[builtin_command_elab «attribute»] def elabAttr : CommandElab := fun stx => do

src/Lean/Elab/DefView.lean

@@ -124,7 +124,7 @@ def mkDefViewOfOpaque (modifiers : Modifiers) (stx : Syntax) : CommandElabM DefV
     | some val => pure val
     | none     =>
       let val ← if modifiers.isUnsafe then `(default_or_ofNonempty% unsafe) else `(default_or_ofNonempty%)
-      `(Parser.Command.declValSimple| := $val)
+      pure <| mkNode ``Parser.Command.declValSimple #[ mkAtomFrom stx ":=", val ]
   return {
     ref := stx, kind := DefKind.opaque, modifiers := modifiers,
     declId := stx[1], binders := binders, type? := some type, value := val

src/Lean/Elab/Deriving/BEq.lean

@@ -57,10 +57,7 @@ where
             let b := mkIdent (← mkFreshUserName `b)
             ctorArgs1 := ctorArgs1.push a
             ctorArgs2 := ctorArgs2.push b
-            let xType ← inferType x
-            if (← isProp xType) then
-              continue
-            if xType.isAppOf indVal.name then
+            if (← inferType x).isAppOf indVal.name then
               rhs ← `($rhs && $(mkIdent auxFunName):ident $a:ident $b:ident)
             else
               rhs ← `($rhs && $a:ident == $b:ident)
@@ -94,9 +91,9 @@ def mkMutualBlock (ctx : Context) : TermElabM Syntax := do
      $auxDefs:command*
     end)
 
-private def mkBEqInstanceCmds (declName : Name) : TermElabM (Array Syntax) := do
-  let ctx ← mkContext "beq" declName
-  let cmds := #[← mkMutualBlock ctx] ++ (← mkInstanceCmds ctx `BEq #[declName])
+private def mkBEqInstanceCmds (declNames : Array Name) : TermElabM (Array Syntax) := do
+  let ctx ← mkContext "beq" declNames[0]!
+  let cmds := #[← mkMutualBlock ctx] ++ (← mkInstanceCmds ctx `BEq declNames)
   trace[Elab.Deriving.beq] "\n{cmds}"
   return cmds
 
@@ -112,18 +109,14 @@ private def mkBEqEnumCmd (name : Name): TermElabM (Array Syntax) := do
 
 open Command
 
-def mkBEqInstance (declName : Name) : CommandElabM Unit := do
-    let cmds ← liftTermElabM <|
-      if (← isEnumType declName) then
-        mkBEqEnumCmd declName
-      else
-         mkBEqInstanceCmds declName
-    cmds.forM elabCommand
-
 def mkBEqInstanceHandler (declNames : Array Name) : CommandElabM Bool := do
-  if (← declNames.allM isInductive) then
-    for declName in declNames do
-      mkBEqInstance declName
+  if declNames.size == 1 && (← isEnumType declNames[0]!) then
+    let cmds ← liftTermElabM <| mkBEqEnumCmd declNames[0]!
+    cmds.forM elabCommand
+    return true
+  else if (← declNames.allM isInductive) && declNames.size > 0 then
+    let cmds ← liftTermElabM <| mkBEqInstanceCmds declNames
+    cmds.forM elabCommand
     return true
   else
     return false

src/Lean/Elab/Deriving/DecEq.lean

@@ -67,12 +67,11 @@ where
                 let b := mkIdent (← mkFreshUserName `b)
                 ctorArgs1 := ctorArgs1.push a
                 ctorArgs2 := ctorArgs2.push b
-                let xType ← inferType x
                 let indValNum :=
                   ctx.typeInfos.findIdx?
-                  (xType.isAppOf ∘ ConstantVal.name ∘ InductiveVal.toConstantVal)
+                  ((← inferType x).isAppOf ∘ ConstantVal.name ∘ InductiveVal.toConstantVal)
                 let recField  := indValNum.map (ctx.auxFunNames[·]!)
-                let isProof ← isProp xType
+                let isProof   := (← inferType (← inferType x)).isProp
                 todo := todo.push (a, b, recField, isProof)
             patterns := patterns.push (← `(@$(mkIdent ctorName₁):ident $ctorArgs1:term*))
             patterns := patterns.push (← `(@$(mkIdent ctorName₁):ident $ctorArgs2:term*))
@@ -187,15 +186,12 @@ def mkDecEqEnum (declName : Name) : CommandElabM Unit := do
   trace[Elab.Deriving.decEq] "\n{cmd}"
   elabCommand cmd
 
-def mkDecEqInstance (declName : Name) : CommandElabM Bool := do
-  if (← isEnumType declName) then
-    mkDecEqEnum declName
+def mkDecEqInstanceHandler (declNames : Array Name) : CommandElabM Bool := do
+  if (← isEnumType declNames[0]!) then
+    mkDecEqEnum declNames[0]!
     return true
   else
-    mkDecEq declName
-
-def mkDecEqInstanceHandler (declNames : Array Name) : CommandElabM Bool := do
-  declNames.foldlM (fun b n => andM (pure b) (mkDecEqInstance n)) true
+    mkDecEq declNames[0]!
 
 builtin_initialize
   registerDerivingHandler `DecidableEq mkDecEqInstanceHandler

src/Lean/Elab/Deriving/FromToJson.lean

@@ -19,58 +19,60 @@ def mkJsonField (n : Name) : CoreM (Bool × Term) := do
   let s₁ := s.dropRightWhile (· == '?')
   return (s != s₁, Syntax.mkStrLit s₁)
 
-def mkToJsonInstance (declName : Name) : CommandElabM Bool := do
-  if isStructure (← getEnv) declName then
-    let cmds ← liftTermElabM do
-      let ctx ← mkContext "toJson" declName
-      let header ← mkHeader ``ToJson 1 ctx.typeInfos[0]!
-      let fields := getStructureFieldsFlattened (← getEnv) declName (includeSubobjectFields := false)
-      let fields ← fields.mapM fun field => do
-        let (isOptField, nm) ← mkJsonField field
-        let target := mkIdent header.targetNames[0]!
-        if isOptField then ``(opt $nm ($target).$(mkIdent field))
-        else ``([($nm, toJson ($target).$(mkIdent field))])
-      let cmd ← `(private def $(mkIdent ctx.auxFunNames[0]!):ident $header.binders:bracketedBinder* : Json :=
-        mkObj <| List.join [$fields,*])
-      return #[cmd] ++ (← mkInstanceCmds ctx ``ToJson #[declName])
-    cmds.forM elabCommand
-    return true
+def mkToJsonInstanceHandler (declNames : Array Name) : CommandElabM Bool := do
+  if declNames.size == 1 then
+    if isStructure (← getEnv) declNames[0]! then
+      let cmds ← liftTermElabM do
+        let ctx ← mkContext "toJson" declNames[0]!
+        let header ← mkHeader ``ToJson 1 ctx.typeInfos[0]!
+        let fields := getStructureFieldsFlattened (← getEnv) declNames[0]! (includeSubobjectFields := false)
+        let fields ← fields.mapM fun field => do
+          let (isOptField, nm) ← mkJsonField field
+          let target := mkIdent header.targetNames[0]!
+          if isOptField then ``(opt $nm ($target).$(mkIdent field))
+          else ``([($nm, toJson ($target).$(mkIdent field))])
+        let cmd ← `(private def $(mkIdent ctx.auxFunNames[0]!):ident $header.binders:bracketedBinder* : Json :=
+          mkObj <| List.join [$fields,*])
+        return #[cmd] ++ (← mkInstanceCmds ctx ``ToJson declNames)
+      cmds.forM elabCommand
+      return true
+    else
+      let indVal ← getConstInfoInduct declNames[0]!
+      let cmds ← liftTermElabM do
+        let ctx ← mkContext "toJson" declNames[0]!
+        let toJsonFuncId := mkIdent ctx.auxFunNames[0]!
+        -- Return syntax to JSONify `id`, either via `ToJson` or recursively
+        -- if `id`'s type is the type we're deriving for.
+        let mkToJson (id : Ident) (type : Expr) : TermElabM Term := do
+          if type.isAppOf indVal.name then `($toJsonFuncId:ident $id:ident)
+          else ``(toJson $id:ident)
+        let header ← mkHeader ``ToJson 1 ctx.typeInfos[0]!
+        let discrs ← mkDiscrs header indVal
+        let alts ← mkAlts indVal fun ctor args userNames => do
+          let ctorStr := ctor.name.eraseMacroScopes.getString!
+          match args, userNames with
+          | #[], _ => ``(toJson $(quote ctorStr))
+          | #[(x, t)], none => ``(mkObj [($(quote ctorStr), $(← mkToJson x t))])
+          | xs, none =>
+            let xs ← xs.mapM fun (x, t) => mkToJson x t
+            ``(mkObj [($(quote ctorStr), Json.arr #[$[$xs:term],*])])
+          | xs, some userNames =>
+            let xs ← xs.mapIdxM fun idx (x, t) => do
+              `(($(quote userNames[idx]!.eraseMacroScopes.getString!), $(← mkToJson x t)))
+            ``(mkObj [($(quote ctorStr), mkObj [$[$xs:term],*])])
+        let auxTerm ← `(match $[$discrs],* with $alts:matchAlt*)
+        let auxCmd ←
+          if ctx.usePartial then
+            let letDecls ← mkLocalInstanceLetDecls ctx ``ToJson header.argNames
+            let auxTerm ← mkLet letDecls auxTerm
+            `(private partial def $toJsonFuncId:ident $header.binders:bracketedBinder* : Json := $auxTerm)
+          else
+            `(private def $toJsonFuncId:ident $header.binders:bracketedBinder* : Json := $auxTerm)
+        return #[auxCmd] ++ (← mkInstanceCmds ctx ``ToJson declNames)
+      cmds.forM elabCommand
+      return true
   else
-    let indVal ← getConstInfoInduct declName
-    let cmds ← liftTermElabM do
-      let ctx ← mkContext "toJson" declName
-      let toJsonFuncId := mkIdent ctx.auxFunNames[0]!
-      -- Return syntax to JSONify `id`, either via `ToJson` or recursively
-      -- if `id`'s type is the type we're deriving for.
-      let mkToJson (id : Ident) (type : Expr) : TermElabM Term := do
-        if type.isAppOf indVal.name then `($toJsonFuncId:ident $id:ident)
-        else ``(toJson $id:ident)
-      let header ← mkHeader ``ToJson 1 ctx.typeInfos[0]!
-      let discrs ← mkDiscrs header indVal
-      let alts ← mkAlts indVal fun ctor args userNames => do
-        let ctorStr := ctor.name.eraseMacroScopes.getString!
-        match args, userNames with
-        | #[], _ => ``(toJson $(quote ctorStr))
-        | #[(x, t)], none => ``(mkObj [($(quote ctorStr), $(← mkToJson x t))])
-        | xs, none =>
-          let xs ← xs.mapM fun (x, t) => mkToJson x t
-          ``(mkObj [($(quote ctorStr), Json.arr #[$[$xs:term],*])])
-        | xs, some userNames =>
-          let xs ← xs.mapIdxM fun idx (x, t) => do
-            `(($(quote userNames[idx]!.eraseMacroScopes.getString!), $(← mkToJson x t)))
-          ``(mkObj [($(quote ctorStr), mkObj [$[$xs:term],*])])
-      let auxTerm ← `(match $[$discrs],* with $alts:matchAlt*)
-      let auxCmd ←
-        if ctx.usePartial then
-          let letDecls ← mkLocalInstanceLetDecls ctx ``ToJson header.argNames
-          let auxTerm ← mkLet letDecls auxTerm
-          `(private partial def $toJsonFuncId:ident $header.binders:bracketedBinder* : Json := $auxTerm)
-        else
-          `(private def $toJsonFuncId:ident $header.binders:bracketedBinder* : Json := $auxTerm)
-      return #[auxCmd] ++ (← mkInstanceCmds ctx ``ToJson #[declName])
-    cmds.forM elabCommand
-    return true
-
+    return false
 where
   mkAlts
     (indVal : InductiveVal)
@@ -101,51 +103,54 @@ where
       let rhs ← rhs ctorInfo binders (if userNames.size == binders.size then some userNames else none)
       `(matchAltExpr| | $[$patterns:term],* => $rhs:term)
 
-def mkFromJsonInstance (declName : Name) : CommandElabM Bool := do
-  if isStructure (← getEnv) declName then
-    let cmds ← liftTermElabM do
-      let ctx ← mkContext "fromJson" declName
-      let header ← mkHeader ``FromJson 0 ctx.typeInfos[0]!
-      let fields := getStructureFieldsFlattened (← getEnv) declName (includeSubobjectFields := false)
-      let getters ← fields.mapM (fun field => do
-        let getter ← `(getObjValAs? j _ $(Prod.snd <| ← mkJsonField field))
-        let getter ← `(doElem| Except.mapError (fun s => (toString $(quote declName)) ++ "." ++ (toString $(quote field)) ++ ": " ++ s) <| $getter)
-        return getter
-      )
-      let fields := fields.map mkIdent
-      let cmd ← `(private def $(mkIdent ctx.auxFunNames[0]!):ident $header.binders:bracketedBinder* (j : Json)
-        : Except String $(← mkInductiveApp ctx.typeInfos[0]! header.argNames) := do
-        $[let $fields:ident ← $getters]*
-        return { $[$fields:ident := $(id fields)],* })
-      return #[cmd] ++ (← mkInstanceCmds ctx ``FromJson #[declName])
-    cmds.forM elabCommand
-    return true
+def mkFromJsonInstanceHandler (declNames : Array Name) : CommandElabM Bool := do
+  if declNames.size == 1 then
+    let declName := declNames[0]!
+    if isStructure (← getEnv) declName then
+      let cmds ← liftTermElabM do
+        let ctx ← mkContext "fromJson" declName
+        let header ← mkHeader ``FromJson 0 ctx.typeInfos[0]!
+        let fields := getStructureFieldsFlattened (← getEnv) declName (includeSubobjectFields := false)
+        let getters ← fields.mapM (fun field => do
+          let getter ← `(getObjValAs? j _ $(Prod.snd <| ← mkJsonField field))
+          let getter ← `(doElem| Except.mapError (fun s => (toString $(quote declName)) ++ "." ++ (toString $(quote field)) ++ ": " ++ s) <| $getter)
+          return getter
+        )
+        let fields := fields.map mkIdent
+        let cmd ← `(private def $(mkIdent ctx.auxFunNames[0]!):ident $header.binders:bracketedBinder* (j : Json)
+          : Except String $(← mkInductiveApp ctx.typeInfos[0]! header.argNames) := do
+          $[let $fields:ident ← $getters]*
+          return { $[$fields:ident := $(id fields)],* })
+        return #[cmd] ++ (← mkInstanceCmds ctx ``FromJson declNames)
+      cmds.forM elabCommand
+      return true
+    else
+      let indVal ← getConstInfoInduct declName
+      let cmds ← liftTermElabM do
+        let ctx ← mkContext "fromJson" declName
+        let header ← mkHeader ``FromJson 0 ctx.typeInfos[0]!
+        let fromJsonFuncId := mkIdent ctx.auxFunNames[0]!
+        let alts ← mkAlts indVal fromJsonFuncId
+        let mut auxTerm ← alts.foldrM (fun xs x => `(Except.orElseLazy $xs (fun _ => $x))) (← `(Except.error "no inductive constructor matched"))
+        if ctx.usePartial then
+          let letDecls ← mkLocalInstanceLetDecls ctx ``FromJson header.argNames
+          auxTerm ← mkLet letDecls auxTerm
+        -- FromJson is not structurally recursive even non-nested recursive inductives,
+        -- so we also use `partial` then.
+        let auxCmd ←
+          if ctx.usePartial || indVal.isRec then
+            `(private partial def $fromJsonFuncId:ident $header.binders:bracketedBinder* (json : Json)
+                  : Except String $(← mkInductiveApp ctx.typeInfos[0]! header.argNames) :=
+                $auxTerm)
+          else
+            `(private def $fromJsonFuncId:ident $header.binders:bracketedBinder* (json : Json)
+                  : Except String $(← mkInductiveApp ctx.typeInfos[0]! header.argNames) :=
+                $auxTerm)
+        return #[auxCmd] ++ (← mkInstanceCmds ctx ``FromJson declNames)
+      cmds.forM elabCommand
+      return true
   else
-    let indVal ← getConstInfoInduct declName
-    let cmds ← liftTermElabM do
-      let ctx ← mkContext "fromJson" declName
-      let header ← mkHeader ``FromJson 0 ctx.typeInfos[0]!
-      let fromJsonFuncId := mkIdent ctx.auxFunNames[0]!
-      let alts ← mkAlts indVal fromJsonFuncId
-      let mut auxTerm ← alts.foldrM (fun xs x => `(Except.orElseLazy $xs (fun _ => $x))) (← `(Except.error "no inductive constructor matched"))
-      if ctx.usePartial then
-        let letDecls ← mkLocalInstanceLetDecls ctx ``FromJson header.argNames
-        auxTerm ← mkLet letDecls auxTerm
-      -- FromJson is not structurally recursive even non-nested recursive inductives,
-      -- so we also use `partial` then.
-      let auxCmd ←
-        if ctx.usePartial || indVal.isRec then
-          `(private partial def $fromJsonFuncId:ident $header.binders:bracketedBinder* (json : Json)
-                : Except String $(← mkInductiveApp ctx.typeInfos[0]! header.argNames) :=
-              $auxTerm)
-        else
-          `(private def $fromJsonFuncId:ident $header.binders:bracketedBinder* (json : Json)
-                : Except String $(← mkInductiveApp ctx.typeInfos[0]! header.argNames) :=
-              $auxTerm)
-      return #[auxCmd] ++ (← mkInstanceCmds ctx ``FromJson #[declName])
-    cmds.forM elabCommand
-    return true
-
+    return false
 where
   mkAlts (indVal : InductiveVal) (fromJsonFuncId : Ident) : TermElabM (Array Term) := do
   let alts ←
@@ -183,12 +188,6 @@ where
   let alts := alts.qsort (fun (_, x) (_, y) => x < y)
   return alts.map Prod.fst
 
-def mkToJsonInstanceHandler (declNames : Array Name) : CommandElabM Bool := do
-  declNames.foldlM (fun b n => andM (pure b) (mkToJsonInstance n)) true
-
-def mkFromJsonInstanceHandler (declNames : Array Name) : CommandElabM Bool := do
-  declNames.foldlM (fun b n => andM (pure b) (mkFromJsonInstance n)) true
-
 builtin_initialize
   registerDerivingHandler ``ToJson mkToJsonInstanceHandler
   registerDerivingHandler ``FromJson mkFromJsonInstanceHandler

src/Lean/Elab/Deriving/Hashable.lean

@@ -75,17 +75,16 @@ def mkHashFuncs (ctx : Context) : TermElabM Syntax := do
     auxDefs := auxDefs.push (← mkAuxFunction ctx i)
   `(mutual $auxDefs:command* end)
 
-private def mkHashableInstanceCmds (declName : Name) : TermElabM (Array Syntax) := do
-  let ctx ← mkContext "hash" declName
-  let cmds := #[← mkHashFuncs ctx] ++ (← mkInstanceCmds ctx `Hashable #[declName])
+private def mkHashableInstanceCmds (declNames : Array Name) : TermElabM (Array Syntax) := do
+  let ctx ← mkContext "hash" declNames[0]!
+  let cmds := #[← mkHashFuncs ctx] ++ (← mkInstanceCmds ctx `Hashable declNames)
   trace[Elab.Deriving.hashable] "\n{cmds}"
   return cmds
 
 def mkHashableHandler (declNames : Array Name) : CommandElabM Bool := do
-  if (← declNames.allM isInductive)  then
-    for declName in declNames do
-      let cmds ← liftTermElabM <| mkHashableInstanceCmds declName
-      cmds.forM elabCommand
+  if (← declNames.allM isInductive) && declNames.size > 0 then
+    let cmds ← liftTermElabM <| mkHashableInstanceCmds declNames
+    cmds.forM elabCommand
     return true
   else
     return false