feat: support for ground terms at DiscrTree.lean

WIP for discussing with @joehendrix

.github/ISSUE_TEMPLATE/bug_report.md

@@ -33,7 +33,7 @@ assignees: ''
 
 ### Versions
 
-[Output of `#eval Lean.versionString` or of `lean --version` in the folder that the issue occured in]
+[Output of `lean --version` in the folder that the issue occured in]
 [OS version]
 
 ### Additional Information

.github/PULL_REQUEST_TEMPLATE.md

@@ -1,13 +1,14 @@
-# Read and remove this section before submitting
+* [ ] Put an X in this bracket to confirm you have read the
+  [External Contribution Guidelines](https://github.com/leanprover/lean4/blob/master/doc/contributions.md).
 
-* 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!
-* 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.
-* Remove this section before submitting.
+* Please put the link to your `RFC` or `bug` issue here.
+  PRs missing this link will be marked as `missing RFC`.
 
-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.
+* If that issue does not already have approval from a developer,
+  please be sure to open this PR in "Draft" mode.
 
-# Summary
+* Please make sure the PR has excellent documentation and tests.
+  If we label it `missing documentation` or `missing tests` then it needs fixing!
 
-Link to `RFC` or `bug` issue:
+* 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.

.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

@@ -6,8 +6,8 @@ on:
     tags:
       - '*'
   pull_request:
-    types: [opened, synchronize, reopened, labeled]
-  merge_group:
+    branches:
+      - master
   schedule:
     - cron: '0 7 * * *'  # 8AM CET/11PM PT
 
@@ -16,185 +16,18 @@ concurrency:
   cancel-in-progress: true
 
 jobs:
-
-  # This job determines various settings for the following CI runs; see the `outputs` for details
-  configure:
+  set-nightly:
     runs-on: ubuntu-latest
     outputs:
-      # Should we run only a quick CI? Yes on a pull request without the full-ci label
-      quick: ${{ steps.set-quick.outputs.quick }}
-      # The build matrix, dynamically generated here
-      matrix: ${{ steps.set-matrix.outputs.result }}
-      # Should we make a nightly release? If so, this output contains the lean version string, else it is empty
-      nightly: ${{ steps.set-nightly.outputs.nightly }}
-      # Should this be the CI for a tagged release?
-      # Yes only if a tag is pushed to the `leanprover` repository, and the tag is "v" followed by a valid semver.
-      # It sets `set-release.outputs.RELEASE_TAG` to the tag
-      # and sets `set-release.outputs.{LEAN_VERSION_MAJOR,LEAN_VERSION_MINOR,LEAN_VERSION_PATCH,LEAN_SPECIAL_VERSION_DESC}`
-      # to the semver components parsed via regex.
-      LEAN_VERSION_MAJOR: ${{ steps.set-release.outputs.LEAN_VERSION_MAJOR }}
-      LEAN_VERSION_MINOR: ${{ steps.set-release.outputs.LEAN_VERSION_MINOR }}
-      LEAN_VERSION_PATCH: ${{ steps.set-release.outputs.LEAN_VERSION_PATCH }}
-      LEAN_SPECIAL_VERSION_DESC: ${{ steps.set-release.outputs.LEAN_SPECIAL_VERSION_DESC }}
-      RELEASE_TAG: ${{ steps.set-release.outputs.RELEASE_TAG }}
-
+      nightly: ${{ steps.set.outputs.nightly }}
     steps:
-      - name: Run quick CI?
-        id: set-quick
-        env:
-          quick: ${{
-            github.event_name == 'pull_request' && !contains( github.event.pull_request.labels.*.name, 'full-ci')
-           }}
-        run: |
-          echo "quick=${{env.quick}}" >> $GITHUB_OUTPUT
-
-      - name: Configure build matrix
-        id: set-matrix
-        uses: actions/github-script@v7
-        with:
-          script: |
-            const quick = ${{ steps.set-quick.outputs.quick }};
-            console.log(`quick: ${quick}`)
-            let matrix = [
-              {
-                // portable release build: use channel with older glibc (2.27)
-                "name": "Linux LLVM",
-                "os": "ubuntu-latest",
-                "release": false,
-                "quick": false,
-                "shell": "nix-shell --arg pkgsDist \"import (fetchTarball \\\"channel:nixos-19.03\\\") {{}}\" --run \"bash -euxo pipefail {0}\"",
-                "llvm-url": "https://github.com/leanprover/lean-llvm/releases/download/15.0.1/lean-llvm-x86_64-linux-gnu.tar.zst",
-                "prepare-llvm": "../script/prepare-llvm-linux.sh lean-llvm*",
-                "binary-check": "ldd -v",
-                // foreign code may be linked against more recent glibc
-                // reverse-ffi needs to be updated to link to LLVM libraries
-                "CTEST_OPTIONS": "-E 'foreign|leanlaketest_reverse-ffi'",
-                "CMAKE_OPTIONS": "-DLLVM=ON -DLLVM_CONFIG=${GITHUB_WORKSPACE}/build/llvm-host/bin/llvm-config"
-              },
-              {
-                "name": "Linux release",
-                "os": "ubuntu-latest",
-                "release": true,
-                "quick": true,
-                "shell": "nix-shell --arg pkgsDist \"import (fetchTarball \\\"channel:nixos-19.03\\\") {{}}\" --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",
-                "prepare-llvm": "../script/prepare-llvm-linux.sh lean-llvm*",
-                "binary-check": "ldd -v",
-                // foreign code may be linked against more recent glibc
-                "CTEST_OPTIONS": "-E 'foreign'"
-              },
-              {
-                "name": "Linux",
-                "os": "ubuntu-latest",
-                "check-stage3": true,
-                "test-speedcenter": true,
-                "quick": false,
-              },
-              {
-                "name": "Linux Debug",
-                "os": "ubuntu-latest",
-                "quick": false,
-                "CMAKE_OPTIONS": "-DCMAKE_BUILD_TYPE=Debug",
-                // exclude seriously slow tests
-                "CTEST_OPTIONS": "-E 'interactivetest|leanpkgtest|laketest|benchtest'"
-              },
-              {
-                "name": "Linux fsanitize",
-                "os": "ubuntu-latest",
-                "quick": false,
-                // turn off custom allocator & symbolic functions to make LSAN do its magic
-                "CMAKE_OPTIONS": "-DLEAN_EXTRA_CXX_FLAGS=-fsanitize=address,undefined -DLEANC_EXTRA_FLAGS='-fsanitize=address,undefined -fsanitize-link-c++-runtime' -DSMALL_ALLOCATOR=OFF -DBSYMBOLIC=OFF",
-                // exclude seriously slow/problematic tests (laketests crash)
-                "CTEST_OPTIONS": "-E 'interactivetest|leanpkgtest|laketest|benchtest'"
-              },
-              {
-                "name": "macOS",
-                "os": "macos-latest",
-                "release": true,
-                "quick": false,
-                "shell": "bash -euxo pipefail {0}",
-                "llvm-url": "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*",
-                "binary-check": "otool -L",
-                "tar": "gtar" // https://github.com/actions/runner-images/issues/2619
-              },
-              {
-                "name": "macOS aarch64",
-                "os": "macos-latest",
-                "release": true,
-                "quick": false,
-                "cross": true,
-                "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": "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
-              },
-              {
-                "name": "Windows",
-                "os": "windows-2022",
-                "release": true,
-                "quick": false,
-                "shell": "msys2 {0}",
-                "CMAKE_OPTIONS": "-G \"Unix Makefiles\" -DUSE_GMP=OFF",
-                // for reasons unknown, interactivetests are flaky on Windows
-                "CTEST_OPTIONS": "--repeat until-pass:2",
-                "llvm-url": "https://github.com/leanprover/lean-llvm/releases/download/15.0.1/lean-llvm-x86_64-w64-windows-gnu.tar.zst",
-                "prepare-llvm": "../script/prepare-llvm-mingw.sh lean-llvm*",
-                "binary-check": "ldd"
-              },
-              {
-                "name": "Linux aarch64",
-                "os": "ubuntu-latest",
-                "CMAKE_OPTIONS": "-DUSE_GMP=OFF -DLEAN_INSTALL_SUFFIX=-linux_aarch64",
-                "release": true,
-                "quick": false,
-                "cross": true,
-                "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": "EXTRA_FLAGS=--target=aarch64-unknown-linux-gnu ../script/prepare-llvm-linux.sh lean-llvm-aarch64-* lean-llvm-x86_64-*"
-              },
-              {
-                "name": "Linux 32bit",
-                "os": "ubuntu-latest",
-                // Use 32bit on stage0 and stage1 to keep oleans compatible
-                "CMAKE_OPTIONS": "-DSTAGE0_USE_GMP=OFF -DSTAGE0_LEAN_EXTRA_CXX_FLAGS='-m32' -DSTAGE0_LEANC_OPTS='-m32' -DSTAGE0_MMAP=OFF -DUSE_GMP=OFF -DLEAN_EXTRA_CXX_FLAGS='-m32' -DLEANC_OPTS='-m32' -DMMAP=OFF -DLEAN_INSTALL_SUFFIX=-linux_x86",
-                "cmultilib": true,
-                "release": true,
-                "quick": false,
-                "cross": true,
-                "shell": "bash -euxo pipefail {0}"
-              },
-              {
-                "name": "Web Assembly",
-                "os": "ubuntu-latest",
-                // Build a native 32bit binary in stage0 and use it to compile the oleans and the wasm build
-                "CMAKE_OPTIONS": "-DCMAKE_C_COMPILER_WORKS=1 -DSTAGE0_USE_GMP=OFF -DSTAGE0_LEAN_EXTRA_CXX_FLAGS='-m32' -DSTAGE0_LEANC_OPTS='-m32' -DSTAGE0_CMAKE_CXX_COMPILER=clang++ -DSTAGE0_CMAKE_C_COMPILER=clang -DSTAGE0_CMAKE_EXECUTABLE_SUFFIX=\"\" -DUSE_GMP=OFF -DMMAP=OFF -DSTAGE0_MMAP=OFF -DCMAKE_AR=../emsdk/emsdk-main/upstream/emscripten/emar -DCMAKE_TOOLCHAIN_FILE=../emsdk/emsdk-main/upstream/emscripten/cmake/Modules/Platform/Emscripten.cmake -DLEAN_INSTALL_SUFFIX=-linux_wasm32",
-                "wasm": true,
-                "cmultilib": true,
-                "release": true,
-                "quick": false,
-                "cross": true,
-                "shell": "bash -euxo pipefail {0}",
-                // Just a few selected tests because wasm is slow
-                "CTEST_OPTIONS": "-R \"leantest_1007\\.lean|leantest_Format\\.lean|leanruntest\\_1037.lean|leanruntest_ac_rfl\\.lean\""
-              }
-            ];
-            console.log(`matrix:\n${JSON.stringify(matrix, null, 2)}`)
-            if (quick) {
-              return matrix.filter((job) => job.quick)
-            } else {
-              return matrix
-            }
-
       - name: Checkout
         uses: actions/checkout@v3
         # don't schedule nightlies on forks
         if: github.event_name == 'schedule' && github.repository == 'leanprover/lean4'
       - name: Set Nightly
         if: github.event_name == 'schedule' && github.repository == 'leanprover/lean4'
-        id: set-nightly
+        id: set
         run: |
           if [[ -n '${{ secrets.PUSH_NIGHTLY_TOKEN }}' ]]; then
             git remote add nightly https://foo:'${{ secrets.PUSH_NIGHTLY_TOKEN }}'@github.com/${{ github.repository_owner }}/lean4-nightly.git
@@ -206,9 +39,26 @@ jobs:
             fi
           fi
 
+  # This job determines if this CI build is for a tagged release.
+  # It only runs when a tag is pushed to the `leanprover` repository.
+  # It sets `set-release.outputs.RELEASE_TAG` to the tag, if the tag is "v" followed by a valid semver,
+  # and sets `set-release.outputs.{LEAN_VERSION_MAJOR,LEAN_VERSION_MINOR,LEAN_VERSION_PATCH,LEAN_SPECIAL_VERSION_DESC}`
+  # to the semver components parsed via regex.
+  set-release:
+    runs-on: ubuntu-latest
+    outputs:
+      LEAN_VERSION_MAJOR: ${{ steps.set.outputs.LEAN_VERSION_MAJOR }}
+      LEAN_VERSION_MINOR: ${{ steps.set.outputs.LEAN_VERSION_MINOR }}
+      LEAN_VERSION_PATCH: ${{ steps.set.outputs.LEAN_VERSION_PATCH }}
+      LEAN_SPECIAL_VERSION_DESC: ${{ steps.set.outputs.LEAN_SPECIAL_VERSION_DESC }}
+      RELEASE_TAG: ${{ steps.set.outputs.RELEASE_TAG }}
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v3
+        if: startsWith(github.ref, 'refs/tags/') && github.repository == 'leanprover/lean4'
       - name: Check for official release
         if: startsWith(github.ref, 'refs/tags/') && github.repository == 'leanprover/lean4'
-        id: set-release
+        id: set
         run: |
           TAG_NAME=${GITHUB_REF##*/}
 
@@ -237,17 +87,98 @@ jobs:
           fi
 
   build:
-    needs: [configure]
+    needs: [set-nightly, set-release]
     if: github.event_name != 'schedule' || github.repository == 'leanprover/lean4'
-    strategy:
-      matrix:
-        include: ${{fromJson(needs.configure.outputs.matrix)}}
-      # complete all jobs
-      fail-fast: false
     runs-on: ${{ matrix.os }}
     defaults:
       run:
         shell: ${{ matrix.shell || 'nix-shell --run "bash -euxo pipefail {0}"' }}
+    strategy:
+      matrix:
+        include:
+          # portable release build: use channel with older glibc (2.27)
+          - name: Linux LLVM
+            os: ubuntu-latest
+            release: false
+            shell: nix-shell --arg pkgsDist "import (fetchTarball \"channel:nixos-19.03\") {{}}" --run "bash -euxo pipefail {0}"
+            llvm-url: https://github.com/leanprover/lean-llvm/releases/download/15.0.1/lean-llvm-x86_64-linux-gnu.tar.zst
+            prepare-llvm: ../script/prepare-llvm-linux.sh lean-llvm*
+            binary-check: ldd -v
+            # foreign code may be linked against more recent glibc
+            # reverse-ffi needs to be updated to link to LLVM libraries
+            CTEST_OPTIONS: -E 'foreign|leanlaketest_reverse-ffi'
+            CMAKE_OPTIONS: -DLLVM=ON -DLLVM_CONFIG=${GITHUB_WORKSPACE}/build/llvm-host/bin/llvm-config
+          - name: Linux release
+            os: ubuntu-latest
+            release: true
+            shell: nix-shell --arg pkgsDist "import (fetchTarball \"channel:nixos-19.03\") {{}}" --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
+            prepare-llvm: ../script/prepare-llvm-linux.sh lean-llvm*
+            binary-check: ldd -v
+            # foreign code may be linked against more recent glibc
+            CTEST_OPTIONS: -E 'foreign'
+          - name: Linux
+            os: ubuntu-latest
+            check-stage3: true
+            test-speedcenter: true
+          - name: Linux Debug
+            os: ubuntu-latest
+            CMAKE_OPTIONS: -DCMAKE_BUILD_TYPE=Debug
+            # exclude seriously slow tests
+            CTEST_OPTIONS: -E 'interactivetest|leanpkgtest|laketest|benchtest'
+          - name: Linux fsanitize
+            os: ubuntu-latest
+            # turn off custom allocator & symbolic functions to make LSAN do its magic
+            CMAKE_OPTIONS: -DLEAN_EXTRA_CXX_FLAGS=-fsanitize=address,undefined -DLEANC_EXTRA_FLAGS='-fsanitize=address,undefined -fsanitize-link-c++-runtime' -DSMALL_ALLOCATOR=OFF -DBSYMBOLIC=OFF
+            # exclude seriously slow/problematic tests (laketests crash)
+            CTEST_OPTIONS: -E 'interactivetest|leanpkgtest|laketest|benchtest'
+          - name: macOS
+            os: macos-latest
+            release: true
+            shell: bash -euxo pipefail {0}
+            llvm-url: 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*
+            binary-check: otool -L
+            tar: gtar  # https://github.com/actions/runner-images/issues/2619
+          - name: macOS aarch64
+            os: macos-latest
+            release: true
+            cross: true
+            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: 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
+          - name: Windows
+            os: windows-2022
+            release: true
+            shell: msys2 {0}
+            CMAKE_OPTIONS: -G "Unix Makefiles" -DUSE_GMP=OFF
+            # for reasons unknown, interactivetests are flaky on Windows
+            CTEST_OPTIONS: --repeat until-pass:2
+            llvm-url: https://github.com/leanprover/lean-llvm/releases/download/15.0.1/lean-llvm-x86_64-w64-windows-gnu.tar.zst
+            prepare-llvm: ../script/prepare-llvm-mingw.sh lean-llvm*
+            binary-check: ldd
+          - name: Linux aarch64
+            os: ubuntu-latest
+            CMAKE_OPTIONS: -DUSE_GMP=OFF -DLEAN_INSTALL_SUFFIX=-linux_aarch64
+            release: true
+            cross: true
+            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: EXTRA_FLAGS=--target=aarch64-unknown-linux-gnu ../script/prepare-llvm-linux.sh lean-llvm-aarch64-* lean-llvm-x86_64-*
+          - name: Web Assembly
+            os: ubuntu-latest
+            # Build a native 32bit binary in stage0 and use it to compile the oleans and the wasm build
+            CMAKE_OPTIONS: -DCMAKE_C_COMPILER_WORKS=1 -DSTAGE0_USE_GMP=OFF -DSTAGE0_LEAN_EXTRA_CXX_FLAGS='-m32' -DSTAGE0_LEANC_OPTS='-m32' -DSTAGE0_CMAKE_CXX_COMPILER=clang++ -DSTAGE0_CMAKE_C_COMPILER=clang -DSTAGE0_CMAKE_EXECUTABLE_SUFFIX="" -DUSE_GMP=OFF -DMMAP=OFF -DSTAGE0_MMAP=OFF -DUSE_GMP=OFF -DCMAKE_AR=../emsdk/emsdk-main/upstream/emscripten/emar -DCMAKE_TOOLCHAIN_FILE=../emsdk/emsdk-main/upstream/emscripten/cmake/Modules/Platform/Emscripten.cmake
+            wasm: true
+            cross: true
+            shell: bash -euxo pipefail {0}
+            # Just a few selected test because wasm is slow
+            CTEST_OPTIONS: -R "leantest_1007\.lean|leantest_Format\.lean|leanruntest\_1037.lean|leanruntest_ac_rfl\.lean"
+      # complete all jobs
+      fail-fast: false
     name: ${{ matrix.name }}
     env:
       # must be inside workspace
@@ -266,13 +197,11 @@ jobs:
         uses: actions/checkout@v3
         with:
           submodules: true
-          # the default is to use a virtual merge commit between the PR and master: just use the PR
-          ref: ${{ github.event.pull_request.head.sha }}
       - name: Install Nix
         uses: cachix/install-nix-action@v18
         with:
           install_url: https://releases.nixos.org/nix/nix-2.12.0/install
-        if: matrix.os == 'ubuntu-latest' && !matrix.cmultilib
+        if: matrix.os == 'ubuntu-latest' && !matrix.wasm
       - name: Install MSYS2
         uses: msys2/setup-msys2@v2
         with:
@@ -285,7 +214,7 @@ jobs:
           brew install ccache tree zstd coreutils gmp
         if: matrix.os == 'macos-latest'
       - name: Setup emsdk
-        uses: mymindstorm/setup-emsdk@v12
+        uses: mymindstorm/setup-emsdk@v11
         with:
           version: 3.1.44
           actions-cache-folder: emsdk
@@ -294,7 +223,7 @@ jobs:
         run: |
           sudo apt-get update
           sudo apt-get install -y gcc-multilib g++-multilib ccache
-        if: matrix.cmultilib
+        if: matrix.wasm
       - name: Cache
         uses: actions/cache@v3
         with:
@@ -319,23 +248,21 @@ jobs:
           mkdir build
           cd build
           ulimit -c unlimited # coredumps
-          # this also enables githash embedding into stage 1 library
-          OPTIONS=(-DCHECK_OLEAN_VERSION=ON)
-          OPTIONS+=(-DLEAN_EXTRA_MAKE_OPTS=-DwarningAsError=true)
+          OPTIONS=()
           if [[ -n '${{ matrix.prepare-llvm }}' ]]; then
             wget -q ${{ matrix.llvm-url }}
             PREPARE="$(${{ matrix.prepare-llvm }})"
             eval "OPTIONS+=($PREPARE)"
           fi
-          if [[ -n '${{ matrix.release }}' && -n '${{ needs.configure.outputs.nightly }}' ]]; then
-            OPTIONS+=(-DLEAN_SPECIAL_VERSION_DESC=${{ needs.configure.outputs.nightly }})
+          if [[ -n '${{ matrix.release }}' && -n '${{ needs.set-nightly.outputs.nightly }}' ]]; then
+            OPTIONS+=(-DLEAN_SPECIAL_VERSION_DESC=${{ needs.set-nightly.outputs.nightly }})
           fi
-          if [[ -n '${{ matrix.release }}' && -n '${{ needs.configure.outputs.RELEASE_TAG }}' ]]; then
-            OPTIONS+=(-DLEAN_VERSION_MAJOR=${{ needs.configure.outputs.LEAN_VERSION_MAJOR }})
-            OPTIONS+=(-DLEAN_VERSION_MINOR=${{ needs.configure.outputs.LEAN_VERSION_MINOR }})
-            OPTIONS+=(-DLEAN_VERSION_PATCH=${{ needs.configure.outputs.LEAN_VERSION_PATCH }})
+          if [[ -n '${{ matrix.release }}' && -n '${{ needs.set-release.outputs.RELEASE_TAG }}' ]]; then
+            OPTIONS+=(-DLEAN_VERSION_MAJOR=${{ needs.set-release.outputs.LEAN_VERSION_MAJOR }})
+            OPTIONS+=(-DLEAN_VERSION_MINOR=${{ needs.set-release.outputs.LEAN_VERSION_MINOR }})
+            OPTIONS+=(-DLEAN_VERSION_PATCH=${{ needs.set-release.outputs.LEAN_VERSION_PATCH }})
             OPTIONS+=(-DLEAN_VERSION_IS_RELEASE=1)
-            OPTIONS+=(-DLEAN_SPECIAL_VERSION_DESC=${{ needs.configure.outputs.LEAN_SPECIAL_VERSION_DESC }})
+            OPTIONS+=(-DLEAN_SPECIAL_VERSION_DESC=${{ needs.set-release.outputs.LEAN_SPECIAL_VERSION_DESC }})
           fi
           # contortion to support empty OPTIONS with old macOS bash
           cmake .. ${{ matrix.CMAKE_OPTIONS }} ${OPTIONS[@]+"${OPTIONS[@]}"} -DLEAN_INSTALL_PREFIX=$PWD/..
@@ -346,13 +273,13 @@ jobs:
       - name: List Install Tree
         run: |
           # omit contents of Init/, ...
-          tree --du -h lean-*-* | grep -E ' (Init|Lean|Lake|LICENSE|[a-z])'
+          tree --du -h lean-* | grep -E ' (Init|Lean|Lake|LICENSE|[a-z])'
       - name: Pack
         run: |
-          dir=$(echo lean-*-*)
+          dir=$(echo lean-*)
           mkdir pack
           # high-compression tar.zst + zip for release, fast tar.zst otherwise
-          if [[ '${{ startsWith(github.ref, 'refs/tags/') && matrix.release }}' == true || -n '${{ needs.configure.outputs.nightly }}' || -n '${{ needs.configure.outputs.RELEASE_TAG }}' ]]; then
+          if [[ '${{ startsWith(github.ref, 'refs/tags/') && matrix.release }}' == true || -n '${{ needs.set-nightly.outputs.nightly }}' || -n '${{ needs.set-release.outputs.RELEASE_TAG }}' ]]; then
             ${{ matrix.tar || 'tar' }} cf - $dir | zstd -T0 --no-progress -19 -o pack/$dir.tar.zst
             zip -rq pack/$dir.zip $dir
           else
@@ -373,22 +300,22 @@ 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
           ulimit -c unlimited # coredumps
           make -j4 stage2
-        if: matrix.test-speedcenter
+        if: matrix.build-stage2 || matrix.check-stage3
       - name: Check Stage 3
         run: |
           cd build
           ulimit -c unlimited # coredumps
           make -j4 check-stage3
-        if: matrix.test-speedcenter
+        if: matrix.check-stage3
       - name: Test Speedcenter Benchmarks
         run: |
           echo -1 | sudo tee /proc/sys/kernel/perf_event_paranoid
@@ -401,7 +328,7 @@ 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'
       - name: CCache stats
         run: ccache -s
       - name: Show stacktrace for coredumps
@@ -425,21 +352,6 @@ jobs:
             ./build/stage2/bin/lean
             ./build/stage2/lib/lean/libleanshared.so
 
-  # This job collects results from all the matrix jobs
-  # This can be made the “required” job, instead of listing each
-  # matrix job separately
-  all-done:
-    name: Build matrix complete
-    runs-on: ubuntu-latest
-    needs: build
-    if: ${{ always() }}
-    steps:
-    - if: contains(needs.*.result, 'failure') ||  contains(needs.*.result, 'cancelled')
-      uses: actions/github-script@v7
-      with:
-        script: |
-            core.setFailed('Some jobs failed')
-
   # This job creates releases from tags
   # (whether they are "unofficial" releases for experiments, or official releases when the tag is "v" followed by a semver string.)
   # We do not attempt to automatically construct a changelog here:
@@ -463,8 +375,8 @@ jobs:
   # This job creates nightly releases during the cron job.
   # It is responsible for creating the tag, and automatically generating a changelog.
   release-nightly:
-    needs: [configure, build]
-    if: needs.configure.outputs.nightly
+    needs: [set-nightly, build]
+    if: needs.set-nightly.outputs.nightly
     runs-on: ubuntu-latest
     steps:
       - name: Checkout
@@ -480,9 +392,8 @@ jobs:
         run: |
           git remote add nightly https://foo:'${{ 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 ${{ needs.configure.outputs.nightly }}
-          git push -f origin refs/tags/${{ needs.configure.outputs.nightly }}:refs/heads/nightly
+          git tag ${{ needs.set-nightly.outputs.nightly }}
+          git push nightly ${{ needs.set-nightly.outputs.nightly }}
           last_tag=$(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
@@ -497,7 +408,7 @@ jobs:
           prerelease: true
           files: artifacts/*/*
           fail_on_unmatched_files: true
-          tag_name: ${{ needs.configure.outputs.nightly }}
+          tag_name: ${{ needs.set-nightly.outputs.nightly }}
           repository: ${{ github.repository_owner }}/lean4-nightly
         env:
           GITHUB_TOKEN: ${{ secrets.PUSH_NIGHTLY_TOKEN }}

.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

@@ -6,7 +6,8 @@ on:
     tags:
       - '*'
   pull_request:
-  merge_group:
+    branches:
+      - master
 
 concurrency:
   group: ${{ github.workflow }}-${{ github.ref }}
@@ -17,7 +18,7 @@ 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 +30,18 @@ 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
+      - name: Install Nix
+        uses: cachix/install-nix-action@v18
         with:
-          # the default is to use a virtual merge commit between the PR and master: just use the PR
-          ref: ${{ github.event.pull_request.head.sha }}
+          # https://github.com/NixOS/nix/issues/6572
+          install_url: https://releases.nixos.org/nix/nix-2.7.0/install
+          extra_nix_config: |
+            extra-sandbox-paths = /nix/var/cache/ccache
+            substituters = file://${{ 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 +55,8 @@ 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 +69,7 @@ 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

.github/workflows/pr-release.yml

@@ -32,9 +32,7 @@ jobs:
           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 }}
+          ref: ${{ steps.workflow-info.outputs.targetCommitSha }}
           # We need a full checkout, so that we can push the PR commits to the `lean4-pr-releases` repo.
           fetch-depth: 0
 
@@ -79,130 +77,30 @@ jobs:
           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
-        id: most-recent-nightly-tag
-        if: ${{ steps.workflow-info.outputs.pullRequestNumber != '' }}
-        run: |
-          echo "MOST_RECENT_NIGHTLY=$(script/most-recent-nightly-tag.sh)" >> $GITHUB_ENV
-
-      - name: 'Setup jq'
-        if: ${{ steps.workflow-info.outputs.pullRequestNumber != '' }}
-        uses: dcarbone/install-jq-action@v1.0.1
-
-      # Check that the most recently nightly coincides with 'git merge-base HEAD master'
-      - name: Check merge-base and nightly-testing-YYYY-MM-DD
-        if: ${{ steps.workflow-info.outputs.pullRequestNumber != '' }}
-        id: ready
-        run: |
-          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" = "$MERGE_BASE_SHA" ]; then
-            echo "Most recent nightly tag agrees with the merge base."
-
-            REMOTE_BRANCHES=$(git ls-remote -h https://github.com/leanprover-community/mathlib4.git nightly-testing-$MOST_RECENT_NIGHTLY)
-
-            if [[ -n "$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' 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: $MERGE_BASE_SHA"
-            git log -10
-
-            MESSAGE="- ❗ Mathlib CI will not be attempted unless you rebase your PR onto the 'nightly' branch."
-          fi
-
-          if [[ -n "$MESSAGE" ]]; then
-
-            echo "Checking existing messages"
-
-            # Use GitHub API to check if a comment already exists
-            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 '.[] | 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"))"
-
-              echo "Posting message to the comments: $MESSAGE"
-
-              # Append new result to the existing comment or post a new comment
-              # It's essential we use the MATHLIB4_BOT token here, so that Mathlib CI can subsequently edit the comment.
-              if [ -z "$existing_comment_id" ]; then
-                # 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 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
-                echo "Appending to existing comment at leanprover/lean4/issues/${{ steps.workflow-info.outputs.pullRequestNumber }}/comments"
-                curl -L -s \
-                  -X PATCH \
-                  -H "Authorization: token ${{ secrets.MATHLIB4_BOT }}" \
-                  -H "Accept: application/vnd.github.v3+json" \
-                  -d "$(jq --null-input --arg existing "$existing_comment_body" --arg message "$MESSAGE" '{"body":($existing + "\n" + $message)}')" \
-                  "https://api.github.com/repos/leanprover/lean4/issues/comments/$existing_comment_id"
-              fi
-            else
-              echo "The message already exists in the comment body."
-            fi
-            echo "::set-output name=mathlib_ready::false"
-          else
-            echo "::set-output name=mathlib_ready::true"
-          fi
-
       # 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'
+        if: ${{ steps.workflow-info.outputs.pullRequestNumber != '' }}
         run: |
           sudo rm -rf *
 
       # Checkout the mathlib4 repository with all branches
       - name: Checkout mathlib4 repository
-        if: steps.workflow-info.outputs.pullRequestNumber != '' && steps.ready.outputs.mathlib_ready == 'true'
-        uses: actions/checkout@v3
+        uses: actions/checkout@v2
         with:
           repository: leanprover-community/mathlib4
           token: ${{ secrets.MATHLIB4_BOT }}
-          ref: nightly-testing
-          fetch-depth: 0 # This ensures we check out all tags and branches.
+          ref: nightly-testing # This is more likely than `master` to work with the base of this PR.
+          fetch-depth: 0
 
       - name: Check if branch exists
-        if: steps.workflow-info.outputs.pullRequestNumber != '' && steps.ready.outputs.mathlib_ready == 'true'
+        if: ${{ steps.workflow-info.outputs.pullRequestNumber != '' }}
         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 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 branch: $BASE"
-
-          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
@@ -214,12 +112,15 @@ jobs:
           else
             echo "Branch already exists, pushing an empty commit."
             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 $BASE --strategy-option ours --no-commit --allow-unrelated-histories
+            # The Mathlib `nightly-testing` branch may have moved since this branch was created, so merge their changes.
+            # If the base of this Lean4 PR becomes significantly older than the nightly being used by `nightly-testing`
+            # this will cause breakages rather than fixing them!
+            # Without cumbersome requirements that Lean4 PRs are based off nightlies, I'm not sure there is a perfect solution here.
+            git merge nightly-testing --strategy-option ours --no-commit --allow-unrelated-histories
             git commit --allow-empty -m "Trigger CI for https://github.com/leanprover/lean4/pull/${{ steps.workflow-info.outputs.pullRequestNumber }}"
           fi
 
       - name: Push changes
-        if: steps.workflow-info.outputs.pullRequestNumber != '' && steps.ready.outputs.mathlib_ready == 'true'
+        if: ${{ steps.workflow-info.outputs.pullRequestNumber != '' }}
         run: |
           git push origin lean-pr-testing-${{ steps.workflow-info.outputs.pullRequestNumber }}

.github/workflows/pr-title.yml

@@ -1,20 +0,0 @@
-name: Check PR title for commit convention
-
-on:
-  merge_group:
-  pull_request:
-    types: [opened, synchronize, reopened, edited]
-
-jobs:
-  check-pr-title:
-    runs-on: ubuntu-latest
-    steps:
-      - name: Check PR title
-        uses: actions/github-script@v7
-        with:
-          script: |
-            const msg = context.payload.pull_request? context.payload.pull_request.title : context.payload.merge_group.head_commit.message;
-            console.log(`Message: ${msg}`)
-            if (!/^(feat|fix|doc|style|refactor|test|chore|perf): .*[^.]($|\n\n)/.test(msg)) {
-              core.setFailed('PR title does not follow the Commit Convention (https://leanprover.github.io/lean4/doc/dev/commit_convention.html).');
-            }

.github/workflows/pr.yml

@@ -0,0 +1,31 @@
+name: sanity-check opened PRs
+
+on:
+  # needs read/write GH token, do *not* execute arbitrary code from PR
+  pull_request_target:
+    types: [opened]
+
+jobs:
+  check-pr:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Check Commit Message
+        uses: actions/github-script@v6
+        with:
+          github-token: ${{ secrets.GITHUB_TOKEN }}
+          script: |
+            const { data: commits } = await github.rest.pulls.listCommits({
+              owner: context.repo.owner,
+              repo: context.repo.repo,
+              pull_number: context.issue.number,
+            });
+            console.log(commits[0].commit.message);
+            // check first commit only (and only once) since later commits might be intended to be squashed away
+            if (!/^(feat|fix|doc|style|refactor|test|chore|perf): .*[^.]($|\n\n)/.test(commits[0].commit.message)) {
+              await github.rest.issues.createComment({
+                owner: context.repo.owner,
+                repo: context.repo.repo,
+                issue_number: context.issue.number,
+                body: 'Thanks for your contribution! Please make sure to follow our [Commit Convention](https://leanprover.github.io/lean4/doc/dev/commit_convention.html).',
+              });
+            }

.gitignore

@@ -2,8 +2,6 @@
 \#*
 .#*
 *.lock
-.lake
-lake-manifest.json
 build
 !/src/lake/Lake/Build
 GPATH

.vscode/settings.json

@@ -0,0 +1,7 @@
+{
+    "files.insertFinalNewline": true,
+    "files.trimTrailingWhitespace": true,
+    "[markdown]": {
+        "rewrap.wrappingColumn": 70
+    }
+}

CMakeLists.txt

@@ -11,7 +11,7 @@ foreach(var ${vars})
     list(APPEND STAGE0_ARGS "-D${CMAKE_MATCH_1}=${${var}}")
   elseif("${currentHelpString}" MATCHES "No help, variable specified on the command line." OR "${currentHelpString}" STREQUAL "")
     list(APPEND CL_ARGS "-D${var}=${${var}}")
-    if("${var}" MATCHES "USE_GMP|CHECK_OLEAN_VERSION")
+    if("${var}" STREQUAL "USE_GMP")
       # must forward options that generate incompatible .olean format
       list(APPEND STAGE0_ARGS "-D${var}=${${var}}")
     endif()
@@ -35,8 +35,6 @@ ExternalProject_add(stage0
   SOURCE_SUBDIR src
   BINARY_DIR stage0
   # do not rebuild stage0 when git hash changes; it's not from this commit anyway
-  # (however, `CHECK_OLEAN_VERSION=ON` in CI will override this as we need to
-  # embed the githash into the stage 1 library built by stage 0)
   CMAKE_ARGS -DSTAGE=0 -DUSE_GITHASH=OFF ${PLATFORM_ARGS} ${STAGE0_ARGS}
   BUILD_ALWAYS ON  # cmake doesn't auto-detect changes without a download method
   INSTALL_COMMAND ""  # skip install

CODEOWNERS

@@ -1,22 +0,0 @@
-# Code Owners
-#
-# Documents responsible people per component.
-# Listed persons will automatically be asked by GitHub to review a PR touching these paths.
-# If multiple names are listed, a review by any of them is considered sufficient by default.
-
-/.github/ @Kha @semorrison
-/RELEASES.md @semorrison
-/src/ @leodemoura @Kha
-/src/Init/IO.lean @joehendrix
-/src/kernel/ @leodemoura
-/src/lake/ @tydeu
-/src/Lean/Compiler/ @leodemoura
-/src/Lean/Data/Lsp/ @mhuisi
-/src/Lean/Elab/Deriving/ @semorrison
-/src/Lean/Elab/Tactic/ @semorrison
-/src/Lean/Meta/Tactic/ @leodemoura
-/src/Lean/Parser/ @Kha
-/src/Lean/PrettyPrinter/ @Kha
-/src/Lean/Server/ @mhuisi
-/src/Lean/Widget/ @Vtec234
-/src/runtime/io.cpp @joehendrix

CONTRIBUTING.md

@@ -1,79 +1,61 @@
-External Contribution Guidelines
-============
+# Contribution Guidelines
 
-In the past, we accepted most pull requests. This practice produced hard to maintain code, performance problems, and bugs. In order to improve the quality and maintainability of our codebase, we've established the following guidelines for external contributions.
+Thank you for your interest in contributing to Lean! There are many ways to contribute and we appreciate all of them.
 
-Helpful links
--------
+## Bug reports
 
-* [Development Setup](./doc/dev/index.md)
-* [Testing](./doc/dev/testing.md)
-* [Commit convention](./doc/dev/commit_convention.md)
+Bug reports as new issues are always welcome. Please check the existing [issues](https://github.com/leanprover/lean4/issues) first.
+Reduce the issue to a self-contained, reproducible test case.
+If you have the chance, before reporting a bug, please search existing issues, as it's possible that
+someone else has already reported your error.
+If you're not sure if something is a bug or not, feel free to file a bug anyway. You may also want to discuss it with the Lean
+community using the [lean4 Zulip channel](https://leanprover.zulipchat.com/#narrow/stream/270676-lean4).
 
-Before You Submit a Pull Request (PR):
--------
+## Simple fixes
 
-**Start with an Issue**: Before submitting a PR, always open an issue discussing the problem you wish to solve or the feature you'd like to add. Use the prefix `RFC:` (request for comments) if you are proposing a new feature. Ask for feedback from other users. Take the time to summarize all the feedback. This allows the maintainers to evaluate your proposal more efficiently. When creating a RFC, consider the following questions:
+Simple fixes for **typos and clear bugs** are welcome.
 
-  - **User Experience**: How does this feature improve the user experience?
+# **IMPORTANT**
 
-  - **Beneficiaries**: Which Lean users and projects do benefit most from this feature/change?
+We are currently overwhelmed. We respectfully request that you hold off on submitting Pull Requests and creating Request for Comments (RFCs) at this time. Our team is actively seeking funding to expand the Lean development team and improve our capacity to review and integrate contributions. We appreciate your understanding and look forward to being able to accept contributions in the near future. In the meantime, the process described in the following sections is temporarily suspended.
 
-  - **Community Feedback**: Have you sought feedback or insights from other Lean users?
+## Documentation
 
-  - **Maintainability**: Will this change streamline code maintenance or simplify its structure?
+Tutorial-like examples are very welcome.
+They are useful for finding rough edges and bugs in Lean 4, for highlighting new features, and for showing how to use Lean.
+If you want to store your tutorial in the Lean 4 repository to make sure future changes will not break it, we suggest the following workflow:
+* Contact one of the Lean developers on Zulip, and check whether your tutorial is a good match for the Lean 4 repository.
+* Send bug reports and report rough edges. We will work with you until the tutorial looks great.
+* Add plenty of comments and make sure others will be able to follow it.
+* Create a pull request in the Lean 4 repository. After merging, we will link it to the official documentation and make sure it becomes part of our test suite.
 
-**Understand the Project**: Familiarize yourself with the project, existing issues, and latest commits. Ensure your contribution aligns with the project's direction and priorities.
+You can use `.lean` or `.md` files to create your tutorial. The `.md` files are ideal when you want to format your prose using markdown. For an example, see [this `.md` file](https://github.com/leanprover/lean4/blob/master/doc/lean3changes.md).
 
-**Stay Updated**: Regularly fetch and merge changes from the main branch to ensure your branch is up-to-date and can be smoothly integrated.
+Contributions to the reference manual are also welcome, but since Lean 4 is changing rapidly, please contact us first using Zulip
+to find out which parts are stable enough to document. We will work with you to get this kind of
+pull request merged. We are also happy to meet using Zoom, Skype or Google hangout to coordinate this kind of effort.
 
-**Help wanted**: We have issues tagged with ["help wanted"](https://github.com/leanprover/lean4/issues?q=is%3Aissue+is%3Aopen+label%3A%22help+wanted%22), if you want to contribute to the project, please take a look at them. If you are interested in one of them, post comments, ask questions, and engage with the core developers there.
+As Lean 4 matures, other forms of documentation (e.g., doc-strings) will be welcome too.
 
-Quality Over Quantity:
------
+## "Help wanted"
 
-**Focused Changes**: Each PR should address a single, clearly-defined issue or feature. Avoid making multiple unrelated changes in a single PR.
+For issues marked as [`help wanted`](https://github.com/leanprover/lean4/issues?q=is%3Aissue+is%3Aopen+label%3A%22help+wanted%22), pull requests (PR) are welcome and we will work with you to get a PR merged. Some of these issues are nontrivial. If you are interested, please consider adding comments to the issue and/or messaging the Lean developers in [Zulip](https://leanprover.zulipchat.com/#).
 
-**Write Tests**: Every new feature or bug fix should come with relevant tests. This ensures the robustness and reliability of the contribution.
+## Unexpected Pull Requests
 
-**Documentation**: Update relevant documentation, including comments in the code, to explain the logic and reasoning behind your changes.
+We have very few core developers, and we cannot review arbitrary pull requests (PRs). Moreover, many features involve subtle tradeoffs, and it may require significant time and energy to even assess a proposed design. We suggest the following workflow:
 
-Coding Standards:
-----
+* First, discuss your idea with the Lean community on Zulip. Ask the community to help collect examples, document the requirements, and detect complications.
+* If there is broad support, create a detailed issue for it on the Lean 4 repository at GitHub, and tag the issue with `RFC`.
+* Ask the community for help documenting the requirements, and for collecting examples and concerns.
+* Wait for one of the core developers to give you a "go ahead". At this point, the core developers will work with you to make sure your PR gets merged.
 
-**Follow the Code Style**: Ensure that your code follows the established coding style of the project.
+We don't want to waste your time by you implementing a feature and then us not being able to merge it.
 
-**Lean on Lean**: Use Lean's built-in features and libraries effectively, avoiding reinventions.
+## How to Contribute
 
-**Performance**: Make sure that your changes do not introduce performance regressions. If possible, optimize the solution for speed and resource usage.
-
-PR Submission:
----
-
-**Descriptive Title and Summary**: The PR title should briefly explain the purpose of the PR. The summary should give more detailed information on what changes are made and why. Links to Zulip threads are not acceptable as a summary. You are responsible for summarizing the discussion, and getting support for it.
-
-**Follow the commit convention**: Pull requests are squash merged, and the
-commit message is taken from the pull request title and body, so make sure they adhere to the [commit convention](https://github.com/leanprover/lean4/blob/master/doc/dev/commit_convention.md). Put questions and extra information, which should not be part of the final commit message, into a first comment rather than the Pull Request description.
-Because the change will be squashed, there is no need to polish the commit messages and history on the branch.
-
-**Link to Relevant Issues**: Reference any issues that your PR addresses to provide context.
-
-**Stay Responsive**: Once the PR is submitted, stay responsive to feedback and be prepared to make necessary revisions. We will close any PR that has been inactive (no response or updates from the submitter) for more than a month.
-
-Reviews and Feedback:
-----
-
-**Be Patient**: Given the limited number of full-time maintainers and the volume of PRs, reviews may take some time.
-
-**Engage Constructively**: Always approach feedback positively and constructively. Remember, reviews are about ensuring the best quality for the project, not personal criticism.
-
-**Continuous Integration**: Ensure that all CI checks pass on your PR. Failed checks will delay the review process. The maintainers will not check PRs containing failures.
-
-What to Expect:
-----
-
-**Not All PRs Get Merged**: While we appreciate every contribution, not all PRs will be merged. Ensure your changes align with the project's goals and quality standards.
-
-**Feedback is a Gift**: It helps improve the project and can also help you grow as a developer or contributor.
-
-**Community Involvement**: Engage with the Lean community on our communication channels. This can lead to better collaboration and understanding of the project's direction.
+* Always follow the [commit convention](https://lean-lang.org/lean4/doc/dev/commit_convention.html).
+* Follow the style of the surrounding code. When in doubt, look at other files using the particular syntax as well.
+* Make sure your code is documented.
+* New features or bug fixes should come with appropriate tests.
+* Ensure all tests work before submitting a PR; see [Development Setup](https://lean-lang.org/lean4/doc/make/index.html#development-setup) and [Fixing Tests](https://lean-lang.org/lean4/doc/dev/fixing_tests.html).

README.md

@@ -14,7 +14,7 @@ and have just begun regular [stable point releases](https://github.com/leanprove
 - [Manual](https://lean-lang.org/lean4/doc/)
 - [Release notes](RELEASES.md) starting at v4.0.0-m3
 - [Examples](https://lean-lang.org/lean4/doc/examples.html)
-- [External Contribution Guidelines](CONTRIBUTING.md)
+- [External Contribution Guidelines](https://github.com/leanprover/lean4/blob/master/doc/contributions.md)
 - [FAQ](https://lean-lang.org/lean4/doc/faq.html)
 
 # Installation

RELEASES.md

@@ -5,109 +5,13 @@ There is not yet a strong guarantee of backwards compatibility between versions,
 only an expectation that breaking changes will be documented in this file.
 
 This file contains work-in-progress notes for the upcoming release, as well as previous stable releases.
-Please check the [releases](https://github.com/leanprover/lean4/releases) page for the current status
-of each version.
+Please check the [releases](https://github.com/leanprover/lean4/releases) page for the current status of each version.
 
-v4.5.0 (development in progress)
----------
-
-* 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).
-
-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).
-* [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).
-
-**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).
-* 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).
-* `lake new foo.bar [std]` now generates executables named `foo-bar` and `lake new foo.bar exe` properly creates `foo/bar.lean`. See PR [#2932](https://github.com/leanprover/lean4/pull/2932).
-* Later packages and libraries in the dependency tree are now preferred over earlier ones. That is, the later ones "shadow" the earlier ones. Such an ordering is more consistent with how declarations generally work in programming languages. This will break any package that relied on the previous ordering. See issue [#2548](https://github.com/leanprover/lean4/issues/2548) and PR [#2937](https://github.com/leanprover/lean4/pull/2937).
-* Executable roots are no longer mistakenly treated as importable. They will no longer be picked up by `findModule?`. See PR [#2937](https://github.com/leanprover/lean4/pull/2937).
-
-v4.3.0
----------
-
-* `simp [f]` does not unfold partial applications of `f` anymore. See issue [#2042](https://github.com/leanprover/lean4/issues/2042).
-  To fix proofs affected by this change, use `unfold f` or `simp (config := { unfoldPartialApp := true }) [f]`.
-* By default, `simp` will no longer try to use Decidable instances to rewrite terms. In particular, not all decidable goals will be closed by `simp`, and the `decide` tactic may be useful in such cases. The `decide` simp configuration option can be used to locally restore the old `simp` behavior, as in `simp (config := {decide := true})`; this includes using Decidable instances to verify side goals such as numeric inequalities.
-
-* Many bug fixes:
-  * [Add left/right actions to term tree coercion elaborator and make `^`` a right action](https://github.com/leanprover/lean4/pull/2778)
-  * [Fix for #2775, don't catch max recursion depth errors](https://github.com/leanprover/lean4/pull/2790)
-  * [Reduction of `Decidable` instances very slow when using `cases` tactic](https://github.com/leanprover/lean4/issues/2552)
-  * [`simp` not rewriting in binder](https://github.com/leanprover/lean4/issues/1926)
-  * [`simp` unfolding `let` even with `zeta := false` option](https://github.com/leanprover/lean4/issues/2669)
-  * [`simp` (with beta/zeta disabled) and discrimination trees](https://github.com/leanprover/lean4/issues/2281)
-  * [unknown free variable introduced by `rw ... at h`](https://github.com/leanprover/lean4/issues/2711)
-  * [`dsimp` doesn't use `rfl` theorems which consist of an unapplied constant](https://github.com/leanprover/lean4/issues/2685)
-  * [`dsimp` does not close reflexive equality goals if they are wrapped in metadata](https://github.com/leanprover/lean4/issues/2514)
-  * [`rw [h]` uses `h` from the environment in preference to `h` from the local context](https://github.com/leanprover/lean4/issues/2729)
-  * [missing `withAssignableSyntheticOpaque` for `assumption` tactic](https://github.com/leanprover/lean4/issues/2361)
-  * [ignoring default value for field warning](https://github.com/leanprover/lean4/issues/2178)
-* [Cancel outstanding tasks on document edit in the language server](https://github.com/leanprover/lean4/pull/2648).
-* [Remove unnecessary `%` operations in `Fin.mod` and `Fin.div`](https://github.com/leanprover/lean4/pull/2688)
-* [Avoid `DecidableEq` in `Array.mem`](https://github.com/leanprover/lean4/pull/2774)
-* [Ensure `USize.size` unifies with `?m + 1`](https://github.com/leanprover/lean4/issues/1926)
-* [Improve compatibility with emacs eglot client](https://github.com/leanprover/lean4/pull/2721)
-
-**Lake:**
-
-* [Sensible defaults for `lake new MyProject math`](https://github.com/leanprover/lean4/pull/2770)
-* Changed `postUpdate?` configuration option to a `post_update` declaration. See the `post_update` syntax docstring for more information on the new syntax.
-* [A manifest is automatically created on workspace load if one does not exists.](https://github.com/leanprover/lean4/pull/2680).
-* The `:=` syntax for configuration declarations (i.e., `package`, `lean_lib`, and `lean_exe`) has been deprecated. For example, `package foo := {...}` is deprecated.
-* [support for overriding package URLs via `LAKE_PKG_URL_MAP`](https://github.com/leanprover/lean4/pull/2709)
-* Moved the default build directory (e.g., `build`), default packages directory (e.g., `lake-packages`), and the compiled configuration (e.g., `lakefile.olean`) into a new dedicated directory for Lake outputs, `.lake`. The cloud release build archives are also stored here, fixing [#2713](https://github.com/leanprover/lean4/issues/2713).
-* Update manifest format to version 7 (see [lean4#2801](https://github.com/leanprover/lean4/pull/2801) for details on the changes).
-* Deprecate the `manifestFile` field of a package configuration.
-* There is now a more rigorous check on `lakefile.olean` compatibility (see [#2842](https://github.com/leanprover/lean4/pull/2842) for more details).
-
-v4.2.0
+v4.3.0 (development in progress)
 ---------
 
 * [isDefEq cache for terms not containing metavariables.](https://github.com/leanprover/lean4/pull/2644).
+* [Cancel outstanding tasks on document edit in the language server](https://github.com/leanprover/lean4/pull/2648).
 * Make [`Environment.mk`](https://github.com/leanprover/lean4/pull/2604) and [`Environment.add`](https://github.com/leanprover/lean4/pull/2642) private, and add [`replay`](https://github.com/leanprover/lean4/pull/2617) as a safer alternative.
 * `IO.Process.output` no longer inherits the standard input of the caller.
 * [Do not inhibit caching](https://github.com/leanprover/lean4/pull/2612) of default-level `match` reduction.
@@ -116,6 +20,10 @@ v4.2.0
 * [Show path of failed import in Lake](https://github.com/leanprover/lean4/pull/2616).
 * [Fix linker warnings on macOS](https://github.com/leanprover/lean4/pull/2598).
 * **Lake:** Add `postUpdate?` package configuration option. Used by a package to specify some code which should be run after a successful `lake update` of the package or one of its downstream dependencies. ([lake#185](https://github.com/leanprover/lake/issues/185))
+
+v4.2.0
+---------
+
 * Improvements to Lake startup time ([#2572](https://github.com/leanprover/lean4/pull/2572), [#2573](https://github.com/leanprover/lean4/pull/2573))
 * `refine e` now replaces the main goal with metavariables which were created during elaboration of `e` and no longer captures pre-existing metavariables that occur in `e` ([#2502](https://github.com/leanprover/lean4/pull/2502)).
   * This is accomplished via changes to `withCollectingNewGoalsFrom`, which also affects `elabTermWithHoles`, `refine'`, `calc` (tactic), and `specialize`. Likewise, all of these now only include newly-created metavariables in their output.

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/contributions.md

@@ -0,0 +1,68 @@
+External Contribution Guidelines
+============
+
+**In the past, we accepted most pull requests. This practice produced hard to maintain code, performance problems, and bugs.** In order to improve the quality and maintainability of our codebase, we've established the following guidelines for external contributions.
+
+Before You Submit a Pull Request (PR):
+-------
+
+**Start with an Issue**: Before submitting a PR, always open an issue discussing the problem you wish to solve or the feature you'd like to add. Use the prefix `RFC:` (request for comments) if you are proposing a new feature. Ask for feedback from other users. Take the time to summarize all the feedback. This allows the maintainers to evaluate your proposal more efficiently. When creating a RFC, consider the following questions:
+
+  - **User Experience**: How does this feature improve the user experience?
+
+  - **Beneficiaries**: Which Lean users and projects do benefit most from this feature/change?
+
+  - **Community Feedback**: Have you sought feedback or insights from other Lean users?
+
+  - **Maintainability**: Will this change streamline code maintenance or simplify its structure?
+
+**Understand the Project**: Familiarize yourself with the project, existing issues, and latest commits. Ensure your contribution aligns with the project's direction and priorities.
+
+**Stay Updated**: Regularly fetch and merge changes from the main branch to ensure your branch is up-to-date and can be smoothly integrated.
+
+**Help wanted**: We have issues tagged with ["help wanted"](https://github.com/leanprover/lean4/issues?q=is%3Aissue+is%3Aopen+label%3A%22help+wanted%22), if you want to contribute to the project, please take a look at them. If you are interested in one of them, post comments, ask questions, and engage with the core developers there.
+
+Quality Over Quantity:
+-----
+
+**Focused Changes**: Each PR should address a single, clearly-defined issue or feature. Avoid making multiple unrelated changes in a single PR.
+
+**Write Tests**: Every new feature or bug fix should come with relevant tests. This ensures the robustness and reliability of the contribution.
+
+**Documentation**: Update relevant documentation, including comments in the code, to explain the logic and reasoning behind your changes.
+
+Coding Standards:
+----
+
+**Follow the Code Style**: Ensure that your code follows the established coding style of the project.
+
+**Lean on Lean**: Use Lean's built-in features and libraries effectively, avoiding reinventions.
+
+**Performance**: Make sure that your changes do not introduce performance regressions. If possible, optimize the solution for speed and resource usage.
+
+PR Submission:
+---
+
+**Descriptive Title and Summary**: The PR title should briefly explain the purpose of the PR. The summary should give more detailed information on what changes are made and why. Links to Zulip threads are not acceptable as a summary. You are responsible for summarizing the discussion, and getting support for it.
+
+**Link to Relevant Issues**: Reference any issues that your PR addresses to provide context.
+
+**Stay Responsive**: Once the PR is submitted, stay responsive to feedback and be prepared to make necessary revisions. We will close any PR that has been inactive (no response or updates from the submitter) for more than a month.
+
+Reviews and Feedback:
+----
+
+**Be Patient**: Given the limited number of full-time maintainers and the volume of PRs, reviews may take some time.
+
+**Engage Constructively**: Always approach feedback positively and constructively. Remember, reviews are about ensuring the best quality for the project, not personal criticism.
+
+**Continuous Integration**: Ensure that all CI checks pass on your PR. Failed checks will delay the review process. The maintainers will not check PRs containing failures.
+
+What to Expect:
+----
+
+**Not All PRs Get Merged**: While we appreciate every contribution, not all PRs will be merged. Ensure your changes align with the project's goals and quality standards.
+
+**Feedback is a Gift**: It helps improve the project and can also help you grow as a developer or contributor.
+
+**Community Involvement**: Engage with the Lean community on our communication channels. This can lead to better collaboration and understanding of the project's direction.

doc/dev/commit_convention.md

@@ -1,15 +1,10 @@
 Git Commit Convention
 =====================
 
-We are using the following convention for writing git commit messages. For pull
-requests, make sure the pull request title and description follow this
-convention, as the squash-merge commit will inherit title and body from the
-pull request.
-
-This convention is based on the one from the AngularJS project ([doc][angularjs-doc],
+We are using the following convention for writing git-commit messages.
+It is based on the one from AngularJS project([doc][angularjs-doc],
 [commits][angularjs-git]).
 
-
 [angularjs-git]: https://github.com/angular/angular.js/commits/master
 [angularjs-doc]: https://docs.google.com/document/d/1QrDFcIiPjSLDn3EL15IJygNPiHORgU1_OOAqWjiDU5Y/edit#
 

doc/dev/index.md

@@ -1,6 +1,6 @@
 # Development Workflow
 
-If you want to make changes to Lean itself, start by [building Lean](../make/index.md) from a clean checkout to make sure that everything is set up correctly.
+If you want to make changes to Lean itself, start by [building Lean](../make/index.html) from a clean checkout to make sure that everything is set up correctly.
 After that, read on below to find out how to set up your editor for changing the Lean source code, followed by further sections of the development manual where applicable such as on the [test suite](testing.md) and [commit convention](commit_convention.md).
 
 If you are planning to make any changes that may affect the compilation of Lean itself, e.g. changes to the parser, elaborator, or compiler, you should first read about the [bootstrapping pipeline](bootstrap.md).
@@ -30,14 +30,20 @@ powershell -f elan-init.ps1 --default-toolchain none
 del elan-init.ps1
 ```
 
-The `lean-toolchain` files in the Lean 4 repository are set up to use the `lean4-stage0`
-toolchain for editing files in `src` and the `lean4` toolchain for editing files in `tests`.
-
-Run the following commands to make `lean4` point at `stage1` and `lean4-stage0` point at `stage0`:
+You can use `elan toolchain link` to give a specific stage build
+directory a reference name, then use `elan override set` to associate
+such a name to the current directory. We usually want to use `stage0`
+for editing files in `src` and `stage1` for everything else (e.g.
+tests).
 ```bash
 # in the Lean rootdir
 elan toolchain link lean4 build/release/stage1
 elan toolchain link lean4-stage0 build/release/stage0
+# make `lean` etc. point to stage1 in the rootdir and subdirs
+elan override set lean4
+cd src
+# make `lean` etc. point to stage0 anywhere inside `src`
+elan override set lean4-stage0
 ```
 
 You can also use the `+toolchain` shorthand (e.g. `lean +lean4-debug`) to switch
@@ -59,15 +65,6 @@ If you push `my-tag` to a fork in your github account `my_name`,
 you can then put `my_name/lean4:my-tag` in your `lean-toolchain` file in a project using `lake`.
 (You must use a tag name that does not start with a numeral, or contain `_`).
 
-### VS Code
-
-There is a `lean.code-workspace` file that correctly sets up VS Code with workspace roots for the stage0/stage1 setup described above as well as with other settings.
-You should always load it when working on Lean, such as by invoking
-```
-code lean.code-workspace
-```
-on the command line.
-
 ### `ccache`
 
 Lean's build process uses [`ccache`](https://ccache.dev/) if it is

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
@@ -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/lexical_structure.md

@@ -79,19 +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*
 ```
 
 Char Literals
@@ -100,9 +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

@@ -14,6 +14,8 @@ Platform-Specific Setup
 - [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/setup.md

@@ -17,8 +17,6 @@ Issue reports and fixes are welcome.
 
 * aarch64 Linux with glibc 2.27+
 * aarch64 (Apple Silicon) macOS
-* x86 (32-bit) Linux
-* Emscripten Web Assembly
 
 <!--
 ### Tier 3

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.

lean-toolchain

@@ -1 +0,0 @@
-lean4

lean.code-workspace

@@ -1,52 +0,0 @@
-{
-	"folders": [
-		{
-			"path": "."
-		},
-		{
-			"path": "src"
-		},
-		{
-			"path": "tests"
-		}
-	],
-	"settings": {
-		"files.insertFinalNewline": true,
-		"files.trimTrailingWhitespace": true,
-		"cmake.buildDirectory": "${workspaceFolder}/build/release",
-		"cmake.generator": "Unix Makefiles",
-		"[markdown]": {
-			"rewrap.wrappingColumn": 70
-		},
-		"[lean4]": {
-			"editor.rulers": [
-				100
-			]
-		}
-	},
-	"tasks": {
-		"version": "2.0.0",
-		"tasks": [
-			{
-				"label": "build",
-				"type": "shell",
-				"command": "make -C build/release -j$(nproc 2>/dev/null || sysctl -n hw.logicalcpu 2>/dev/null || echo 4)",
-				"problemMatcher": [],
-				"group": {
-					"kind": "build",
-					"isDefault": true
-				}
-			},
-			{
-				"label": "test",
-				"type": "shell",
-				"command": "NPROC=$(nproc 2>/dev/null || sysctl -n hw.logicalcpu 2>/dev/null || echo 4); CTEST_OUTPUT_ON_FAILURE=1 make -C build/release test -j$NPROC ARGS=\"-j$NPROC\"",
-				"problemMatcher": [],
-				"group": {
-					"kind": "test",
-					"isDefault": true
-				}
-			}
-		]
-	}
-}

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' ]; };

nix/lake-dev.in

@@ -10,7 +10,7 @@ function pebkac() {
 [[ $# -gt 0 ]] || pebkac
 case $1 in
     --version)
-        # minimum version for `lake serve` with fallback
+        # minimum version for `lake server` with fallback
         echo 3.1.0
         ;;
     print-paths)

script/most-recent-nightly-tag.sh

@@ -1,16 +0,0 @@
-#!/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 5)
+set(LEAN_VERSION_MINOR 3)
 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'")
@@ -64,10 +64,10 @@ option(BSYMBOLIC "Link with -Bsymbolic to reduce call overhead in shared librari
 option(USE_GMP "USE_GMP" ON)
 
 # development-specific options
-option(CHECK_OLEAN_VERSION "Only load .olean files compiled with the current version of Lean" OFF)
+option(CHECK_OLEAN_VERSION "Only load .olean files compiled with the current version of Lean" ON)
 
 set(LEAN_EXTRA_MAKE_OPTS  ""                           CACHE STRING "extra options to lean --make")
-set(LEANC_CC              ${CMAKE_C_COMPILER}          CACHE STRING "C compiler to use in `leanc`")
+set(LEANC_CC              "cc"                         CACHE STRING "C compiler to use in `leanc`")
 
 if ("${LAZY_RC}" MATCHES "ON")
   set(LEAN_LAZY_RC "#define LEAN_LAZY_RC")
@@ -93,9 +93,8 @@ if ("${RUNTIME_STATS}" MATCHES "ON")
   string(APPEND LEAN_EXTRA_CXX_FLAGS " -D LEAN_RUNTIME_STATS")
 endif()
 
-if ("${CHECK_OLEAN_VERSION}" MATCHES "ON")
-  set(USE_GITHASH ON)
-  string(APPEND LEAN_EXTRA_CXX_FLAGS " -D LEAN_CHECK_OLEAN_VERSION")
+if (NOT("${CHECK_OLEAN_VERSION}" MATCHES "ON"))
+  string(APPEND LEAN_EXTRA_CXX_FLAGS " -D LEAN_IGNORE_OLEAN_VERSION")
 endif()
 
 if(${CMAKE_SYSTEM_NAME} MATCHES "Emscripten")
@@ -402,17 +401,26 @@ if(MULTI_THREAD AND NOT MSVC AND (NOT ("${CMAKE_SYSTEM_NAME}" MATCHES "Darwin"))
 endif()
 
 # Git HASH
+set(LEAN_PACKAGE_VERSION "NOT-FOUND")
 if(USE_GITHASH)
   include(GetGitRevisionDescription)
   get_git_head_revision(GIT_REFSPEC GIT_SHA1)
   if(${GIT_SHA1} MATCHES "GITDIR-NOTFOUND")
     message(STATUS "Failed to read git_sha1")
     set(GIT_SHA1 "")
+    if(EXISTS "${LEAN_SOURCE_DIR}/bin/package_version")
+      file(STRINGS "${LEAN_SOURCE_DIR}/bin/package_version" LEAN_PACKAGE_VERSION)
+      message(STATUS "Package version detected: ${LEAN_PACKAGE_VERSION}")
+    endif()
   else()
     message(STATUS "git commit sha1: ${GIT_SHA1}")
   endif()
 else()
   set(GIT_SHA1 "")
+  if(EXISTS "${LEAN_SOURCE_DIR}/bin/package_version")
+    file(STRINGS "${LEAN_SOURCE_DIR}/bin/package_version" LEAN_PACKAGE_VERSION)
+    message(STATUS "Package version detected: ${LEAN_PACKAGE_VERSION}")
+  endif()
 endif()
 configure_file("${LEAN_SOURCE_DIR}/githash.h.in" "${LEAN_BINARY_DIR}/githash.h")
 
@@ -439,13 +447,12 @@ include_directories(${LEAN_SOURCE_DIR})
 include_directories(${CMAKE_BINARY_DIR})  # version.h etc., "private" headers
 include_directories(${CMAKE_BINARY_DIR}/include)  # config.h etc., "public" headers
 
-# Use CMake profile C++ flags for building Lean libraries, but do not embed in `leanc`
 string(TOUPPER "${CMAKE_BUILD_TYPE}" uppercase_CMAKE_BUILD_TYPE)
+# These are used in lean.mk (and libleanrt) and passed through by stdlib.make
+# They are not embedded into `leanc` since they are build profile/machine specific
 string(APPEND LEANC_OPTS " ${CMAKE_CXX_FLAGS_${uppercase_CMAKE_BUILD_TYPE}}")
-
-# Do embed flag for finding system libraries in dev builds
 if(CMAKE_OSX_SYSROOT AND NOT LEAN_STANDALONE)
-  string(APPEND LEANC_EXTRA_FLAGS " ${CMAKE_CXX_SYSROOT_FLAG}${CMAKE_OSX_SYSROOT}")
+  string(APPEND LEANC_OPTS " ${CMAKE_CXX_SYSROOT_FLAG}${CMAKE_OSX_SYSROOT}")
 endif()
 
 if(${STAGE} GREATER 1)

src/Init.lean

@@ -17,7 +17,6 @@ import Init.System
 import Init.Util
 import Init.Dynamic
 import Init.ShareCommon
-import Init.MetaTypes
 import Init.Meta
 import Init.NotationExtra
 import Init.SimpLemmas

src/Init/Data/Array/Basic.lean

@@ -468,9 +468,6 @@ def elem [BEq α] (a : α) (as : Array α) : Bool :=
     else
       (true, r)
 
-/-- Convert a `Array α` into an `List α`. This is O(n) in the size of the array.  -/
--- This function is exported to C, where it is called by `Array.data`
--- (the projection) to implement this functionality.
 @[export lean_array_to_list]
 def toList (as : Array α) : List α :=
   as.foldr List.cons []

src/Init/Data/Array/Mem.lean

@@ -1,7 +1,7 @@
 /-
 Copyright (c) 2022 Microsoft Corporation. All rights reserved.
 Released under Apache 2.0 license as described in the file LICENSE.
-Authors: Leonardo de Moura, Joachim Breitner
+Authors: Leonardo de Moura
 -/
 prelude
 import Init.Data.Array.Basic
@@ -20,26 +20,32 @@ theorem List.sizeOf_get_lt [SizeOf α] (as : List α) (i : Fin as.length) : size
 
 namespace Array
 
-/-- `a ∈ as` is a predicate which asserts that `a` is in the array `as`. -/
--- NB: This is defined as a structure rather than a plain def so that a lemma
--- like `sizeOf_lt_of_mem` will not apply with no actual arrays around.
-structure Mem (a : α) (as : Array α) : Prop where
-  val : a ∈ as.data
-
-instance : Membership α (Array α) where
-  mem a as := Mem a as
+instance [DecidableEq α] : Membership α (Array α) where
+  mem a as := as.contains a
 
 theorem sizeOf_get_lt [SizeOf α] (as : Array α) (i : Fin as.size) : sizeOf (as.get i) < sizeOf as := by
-  cases as with | _ as =>
-  exact Nat.lt_trans (List.sizeOf_get_lt as i) (by simp_arith)
+  cases as; rename_i as
+  simp [get]
+  have ih := List.sizeOf_get_lt as i
+  exact Nat.lt_trans ih (by simp_arith)
 
-theorem sizeOf_lt_of_mem [SizeOf α] {as : Array α} (h : a ∈ as) : sizeOf a < sizeOf as := by
-  cases as with | _ as =>
-  exact Nat.lt_trans (List.sizeOf_lt_of_mem h.val) (by simp_arith)
+theorem sizeOf_lt_of_mem [DecidableEq α] [SizeOf α] {as : Array α} (h : a ∈ as) : sizeOf a < sizeOf as := by
+  simp [Membership.mem, contains, any, Id.run, BEq.beq, anyM] at h
+  let rec aux (j : Nat) (h : anyM.loop (m := Id) (fun b => decide (a = b)) as as.size (Nat.le_refl ..) j = true) : sizeOf a < sizeOf as := by
+    unfold anyM.loop at h
+    split at h
+    · simp [Bind.bind, pure] at h; split at h
+      next he => subst a; apply sizeOf_get_lt
+      next => have ih := aux (j+1) h; assumption
+    · contradiction
+  apply aux 0 h
+termination_by aux j _ => as.size - j
 
 @[simp] theorem sizeOf_get [SizeOf α] (as : Array α) (i : Fin as.size) : sizeOf (as.get i) < sizeOf as := by
-  cases as with | _ as =>
-  exact Nat.lt_trans (List.sizeOf_get ..) (by simp_arith)
+  cases as
+  simp [get]
+  apply Nat.lt_trans (List.sizeOf_get ..)
+  simp_arith
 
 /-- This tactic, added to the `decreasing_trivial` toolbox, proves that
 `sizeOf arr[i] < sizeOf arr`, which is useful for well founded recursions
@@ -51,17 +57,4 @@ macro "array_get_dec" : tactic =>
 
 macro_rules | `(tactic| decreasing_trivial) => `(tactic| array_get_dec)
 
-/-- This tactic, added to the `decreasing_trivial` toolbox, proves that `sizeOf a < sizeOf arr`
-provided that `a ∈ arr` which is useful for well founded recursions over a nested inductive like
-`inductive T | mk : Array T → T`. -/
--- NB: This is analogue to tactic `sizeOf_list_dec`
-macro "array_mem_dec" : tactic =>
-  `(tactic| first
-    | apply Array.sizeOf_lt_of_mem; assumption; done
-    | apply Nat.lt_trans (Array.sizeOf_lt_of_mem ?h)
-      case' h => assumption
-      simp_arith)
-
-macro_rules | `(tactic| decreasing_trivial) => `(tactic| array_mem_dec)
-
 end Array

src/Init/Data/Fin/Basic.lean

@@ -45,19 +45,19 @@ protected def sub : Fin n → Fin n → Fin n
   | ⟨a, h⟩, ⟨b, _⟩ => ⟨(a + (n - b)) % n, mlt h⟩
 
 /-!
-Remark: land/lor can be defined without using (% n), but
+Remark: mod/div/modn/land/lor can be defined without using (% n), but
 we are trying to minimize the number of Nat theorems
 needed to bootstrap Lean.
 -/
 
 protected def mod : Fin n → Fin n → Fin n
-  | ⟨a, h⟩, ⟨b, _⟩ => ⟨a % b,  Nat.lt_of_le_of_lt (Nat.mod_le _ _) h⟩
+  | ⟨a, h⟩, ⟨b, _⟩ => ⟨(a % b) % n, mlt h⟩
 
 protected def div : Fin n → Fin n → Fin n
-  | ⟨a, h⟩, ⟨b, _⟩ => ⟨a / b, Nat.lt_of_le_of_lt (Nat.div_le_self _ _) h⟩
+  | ⟨a, h⟩, ⟨b, _⟩ => ⟨(a / b) % n, mlt h⟩
 
 def modn : Fin n → Nat → Fin n
-  | ⟨a, h⟩, m => ⟨a % m, Nat.lt_of_le_of_lt (Nat.mod_le _ _) h⟩
+  | ⟨a, h⟩, m => ⟨(a % m) % n, mlt h⟩
 
 def land : Fin n → Fin n → Fin n
   | ⟨a, h⟩, ⟨b, _⟩ => ⟨(Nat.land a b) % n, mlt h⟩
@@ -110,7 +110,7 @@ theorem val_ne_of_ne {i j : Fin n} (h : i ≠ j) : val i ≠ val j :=
   fun h' => absurd (eq_of_val_eq h') h
 
 theorem modn_lt : ∀ {m : Nat} (i : Fin n), m > 0 → (modn i m).val < m
-  | _, ⟨_, _⟩, hp =>  by simp [modn]; apply Nat.mod_lt; assumption
+  | _, ⟨_, _⟩, hp =>  Nat.lt_of_le_of_lt (mod_le _ _) (mod_lt _ hp)
 
 theorem val_lt_of_le (i : Fin b) (h : b ≤ n) : i.val < n :=
   Nat.lt_of_lt_of_le i.isLt h

src/Init/Data/Float.lean

@@ -132,7 +132,7 @@ instance : ReprAtom Float  := ⟨⟩
 @[extern "round"] opaque Float.round : Float → Float
 @[extern "fabs"] opaque Float.abs : Float → Float
 
-instance : HomogeneousPow Float := ⟨Float.pow⟩
+instance : Pow Float Float := ⟨Float.pow⟩
 
 instance : Min Float := minOfLe
 

src/Init/Data/List/Basic.lean

@@ -6,48 +6,9 @@ Author: Leonardo de Moura
 prelude
 import Init.SimpLemmas
 import Init.Data.Nat.Basic
-import Init.Data.Nat.Div
 set_option linter.missingDocs true -- keep it documented
 open Decidable List
 
-/--
-The syntax `[a, b, c]` is shorthand for `a :: b :: c :: []`, or
-`List.cons a (List.cons b (List.cons c List.nil))`. It allows conveniently constructing
-list literals.
-
-For lists of length at least 64, an alternative desugaring strategy is used
-which uses let bindings as intermediates as in
-`let left := [d, e, f]; a :: b :: c :: left` to avoid creating very deep expressions.
-Note that this changes the order of evaluation, although it should not be observable
-unless you use side effecting operations like `dbg_trace`.
--/
-syntax "[" withoutPosition(term,*,?) "]"  : term
-
-/--
-Auxiliary syntax for implementing `[$elem,*]` list literal syntax.
-The syntax `%[a,b,c|tail]` constructs a value equivalent to `a::b::c::tail`.
-It uses binary partitioning to construct a tree of intermediate let bindings as in
-`let left := [d, e, f]; a :: b :: c :: left` to avoid creating very deep expressions.
--/
-syntax "%[" withoutPosition(term,*,? " | " term) "]" : term
-
-namespace Lean
-
-macro_rules
-  | `([ $elems,* ]) => do
-    -- NOTE: we do not have `TSepArray.getElems` yet at this point
-    let rec expandListLit (i : Nat) (skip : Bool) (result : TSyntax `term) : MacroM Syntax := do
-      match i, skip with
-      | 0,   _     => pure result
-      | i+1, true  => expandListLit i false result
-      | i+1, false => expandListLit i true  (← ``(List.cons $(⟨elems.elemsAndSeps.get! i⟩) $result))
-    let size := elems.elemsAndSeps.size
-    if size < 64 then
-      expandListLit size (size % 2 == 0) (← ``(List.nil))
-    else
-      `(%[ $elems,* | List.nil ])
-end Lean
-
 universe u v w
 
 variable {α : Type u} {β : Type v} {γ : Type w}
@@ -395,7 +356,7 @@ inductive Mem (a : α) : List α → Prop
 instance : Membership α (List α) where
   mem := Mem
 
-theorem mem_of_elem_eq_true [BEq α] [LawfulBEq α] {a : α} {as : List α} : elem a as = true → a ∈ as := by
+theorem mem_of_elem_eq_true [DecidableEq α] {a : α} {as : List α} : elem a as = true → a ∈ as := by
   match as with
   | [] => simp [elem]
   | a'::as =>
@@ -404,12 +365,12 @@ theorem mem_of_elem_eq_true [BEq α] [LawfulBEq α] {a : α} {as : List α} : el
     next h => intros; simp [BEq.beq] at h; subst h; apply Mem.head
     next _ => intro h; exact Mem.tail _ (mem_of_elem_eq_true h)
 
-theorem elem_eq_true_of_mem [BEq α] [LawfulBEq α] {a : α} {as : List α} (h : a ∈ as) : elem a as = true := by
+theorem elem_eq_true_of_mem [DecidableEq α] {a : α} {as : List α} (h : a ∈ as) : elem a as = true := by
   induction h with
   | head _ => simp [elem]
   | tail _ _ ih => simp [elem]; split; rfl; assumption
 
-instance [BEq α] [LawfulBEq α] (a : α) (as : List α) : Decidable (a ∈ as) :=
+instance [DecidableEq α] (a : α) (as : List α) : Decidable (a ∈ as) :=
   decidable_of_decidable_of_iff (Iff.intro mem_of_elem_eq_true elem_eq_true_of_mem)
 
 theorem mem_append_of_mem_left {a : α} {as : List α} (bs : List α) : a ∈ as → a ∈ as ++ bs := by

src/Init/Data/Nat/Basic.lean

@@ -629,7 +629,7 @@ protected theorem sub_lt_sub_left : ∀ {k m n : Nat}, k < m → k < n → m - n
 @[simp] protected theorem zero_sub (n : Nat) : 0 - n = 0 := by
   induction n with
   | zero => rfl
-  | succ n ih => simp only [ih, Nat.sub_succ]; decide
+  | succ n ih => simp [ih, Nat.sub_succ]
 
 protected theorem sub_self_add (n m : Nat) : n - (n + m) = 0 := by
   show (n + 0) - (n + m) = 0

src/Init/Data/UInt/Basic.lean

@@ -285,7 +285,7 @@ instance : Max UInt64 := maxOfLe
 instance : Min UInt64 := minOfLe
 
 theorem usize_size_gt_zero : USize.size > 0 :=
-  Nat.zero_lt_succ ..
+  Nat.pos_pow_of_pos System.Platform.numBits (Nat.zero_lt_succ _)
 
 @[extern "lean_usize_of_nat"]
 def USize.ofNat (n : @& Nat) : USize := ⟨Fin.ofNat' n usize_size_gt_zero⟩

src/Init/Meta.lean

@@ -6,7 +6,6 @@ Authors: Leonardo de Moura and Sebastian Ullrich
 Additional goodies for writing macros
 -/
 prelude
-import Init.MetaTypes
 import Init.Data.Array.Basic
 import Init.Data.Option.BasicAux
 
@@ -65,15 +64,6 @@ def toolchain :=
 @[extern "lean_internal_is_stage0"]
 opaque Internal.isStage0 (u : Unit) : Bool
 
-/--
-This function can be used to detect whether the compiler has support for
-generating LLVM instead of C. It is used by lake instead of the --features
-flag in order to avoid having to run a compiler for this every time on startup.
-See #2572.
--/
-@[extern "lean_internal_has_llvm_backend"]
-opaque Internal.hasLLVMBackend (u : Unit) : Bool
-
 /-- Valid identifier names -/
 def isGreek (c : Char) : Bool :=
   0x391 ≤ c.val && c.val ≤ 0x3dd
@@ -227,6 +217,11 @@ instance : DecidableEq Name :=
 
 end Name
 
+structure NameGenerator where
+  namePrefix : Name := `_uniq
+  idx        : Nat  := 1
+  deriving Inhabited
+
 namespace NameGenerator
 
 @[inline] def curr (g : NameGenerator) : Name :=
@@ -457,6 +452,11 @@ end Syntax
   | none => x
   | some ref => withRef ref x
 
+/-- Syntax objects for a Lean module. -/
+structure Module where
+  header   : Syntax
+  commands : Array Syntax
+
 /--
   Expand macros in the given syntax.
   A node with kind `k` is visited only if `p k` is true.
@@ -773,16 +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
@@ -791,12 +781,8 @@ 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)
 
@@ -1176,12 +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⟩ ""
@@ -1221,7 +1203,88 @@ end TSyntax
 
 namespace Meta
 
-deriving instance Repr for TransparencyMode, EtaStructMode, DSimp.Config, Simp.Config
+inductive TransparencyMode where
+  | all | default | reducible | instances
+  deriving Inhabited, BEq, Repr
+
+inductive EtaStructMode where
+  /-- Enable eta for structure and classes. -/
+  | all
+  /-- Enable eta only for structures that are not classes. -/
+  | notClasses
+  /-- Disable eta for structures and classes. -/
+  | none
+  deriving Inhabited, BEq, Repr
+
+namespace DSimp
+
+structure Config where
+  zeta              : Bool := true
+  beta              : Bool := true
+  eta               : Bool := true
+  etaStruct         : EtaStructMode := .all
+  iota              : Bool := true
+  proj              : Bool := true
+  decide            : Bool := false
+  autoUnfold        : Bool := false
+  /-- If `failIfUnchanged := true`, then calls to `simp`, `dsimp`, or `simp_all`
+  will fail if they do not make progress. -/
+  failIfUnchanged   : Bool := true
+  deriving Inhabited, BEq, Repr
+
+end DSimp
+
+namespace Simp
+
+def defaultMaxSteps := 100000
+
+structure Config where
+  maxSteps          : Nat  := defaultMaxSteps
+  maxDischargeDepth : Nat  := 2
+  contextual        : Bool := false
+  memoize           : Bool := true
+  singlePass        : Bool := false
+  zeta              : Bool := true
+  beta              : Bool := true
+  eta               : Bool := true
+  etaStruct         : EtaStructMode := .all
+  iota              : Bool := true
+  proj              : Bool := true
+  decide            : Bool := true
+  arith             : Bool := false
+  autoUnfold        : Bool := false
+  /--
+    If `dsimp := true`, then switches to `dsimp` on dependent arguments where there is no congruence theorem that allows
+    `simp` to visit them. If `dsimp := false`, then argument is not visited.
+  -/
+  dsimp             : Bool := true
+  /-- If `failIfUnchanged := true`, then calls to `simp`, `dsimp`, or `simp_all`
+  will fail if they do not make progress. -/
+  failIfUnchanged   : Bool := true
+  deriving Inhabited, BEq, Repr
+
+-- Configuration object for `simp_all`
+structure ConfigCtx extends Config where
+  contextual := true
+
+def neutralConfig : Simp.Config := {
+  zeta              := false
+  beta              := false
+  eta               := false
+  iota              := false
+  proj              := false
+  decide            := false
+  arith             := false
+  autoUnfold        := false
+}
+
+end Simp
+
+inductive Occurrences where
+  | all
+  | pos (idxs : List Nat)
+  | neg (idxs : List Nat)
+  deriving Inhabited, BEq
 
 def Occurrences.contains : Occurrences → Nat → Bool
   | all,      _   => true
@@ -1279,14 +1342,14 @@ This will rewrite with all equation lemmas, which can be used to
 partially evaluate many definitions. -/
 declare_simp_like_tactic simpAutoUnfold "simp! " fun (c : Lean.Meta.Simp.Config) => { c with autoUnfold := true }
 
-/-- `simp_arith` is shorthand for `simp` with `arith := true` and `decide := true`.
+/-- `simp_arith` is shorthand for `simp` with `arith := true`.
 This enables the use of normalization by linear arithmetic. -/
-declare_simp_like_tactic simpArith "simp_arith " fun (c : Lean.Meta.Simp.Config) => { c with arith := true, decide := true }
+declare_simp_like_tactic simpArith "simp_arith " fun (c : Lean.Meta.Simp.Config) => { c with arith := true }
 
 /-- `simp_arith!` is shorthand for `simp_arith` with `autoUnfold := true`.
 This will rewrite with all equation lemmas, which can be used to
 partially evaluate many definitions. -/
-declare_simp_like_tactic simpArithAutoUnfold "simp_arith! " fun (c : Lean.Meta.Simp.Config) => { c with arith := true, autoUnfold := true, decide := true }
+declare_simp_like_tactic simpArithAutoUnfold "simp_arith! " fun (c : Lean.Meta.Simp.Config) => { c with arith := true, autoUnfold := true }
 
 /-- `simp_all!` is shorthand for `simp_all` with `autoUnfold := true`.
 This will rewrite with all equation lemmas, which can be used to
@@ -1294,10 +1357,10 @@ partially evaluate many definitions. -/
 declare_simp_like_tactic (all := true) simpAllAutoUnfold "simp_all! " fun (c : Lean.Meta.Simp.ConfigCtx) => { c with autoUnfold := true }
 
 /-- `simp_all_arith` combines the effects of `simp_all` and `simp_arith`. -/
-declare_simp_like_tactic (all := true) simpAllArith "simp_all_arith " fun (c : Lean.Meta.Simp.ConfigCtx) => { c with arith := true, decide := true }
+declare_simp_like_tactic (all := true) simpAllArith "simp_all_arith " fun (c : Lean.Meta.Simp.ConfigCtx) => { c with arith := true }
 
 /-- `simp_all_arith!` combines the effects of `simp_all`, `simp_arith` and `simp!`. -/
-declare_simp_like_tactic (all := true) simpAllArithAutoUnfold "simp_all_arith! " fun (c : Lean.Meta.Simp.ConfigCtx) => { c with arith := true, autoUnfold := true, decide := true }
+declare_simp_like_tactic (all := true) simpAllArithAutoUnfold "simp_all_arith! " fun (c : Lean.Meta.Simp.ConfigCtx) => { c with arith := true, autoUnfold := true }
 
 /-- `dsimp!` is shorthand for `dsimp` with `autoUnfold := true`.
 This will rewrite with all equation lemmas, which can be used to

src/Init/MetaTypes.lean

@@ -1,124 +0,0 @@
-/-
-Copyright (c) Leonardo de Moura. All rights reserved.
-Released under Apache 2.0 license as described in the file LICENSE.
-Authors: Leonardo de Moura
--/
-prelude
-import Init.Core
-
-namespace Lean
-
-structure NameGenerator where
-  namePrefix : Name := `_uniq
-  idx        : Nat  := 1
-  deriving Inhabited
-
-/-- Syntax objects for a Lean module. -/
-structure Module where
-  header   : Syntax
-  commands : Array Syntax
-
-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
-  deriving Inhabited, BEq
-
-inductive EtaStructMode where
-  /-- Enable eta for structure and classes. -/
-  | all
-  /-- Enable eta only for structures that are not classes. -/
-  | notClasses
-  /-- Disable eta for structures and classes. -/
-  | none
-  deriving Inhabited, BEq
-
-namespace DSimp
-
-structure Config where
-  zeta              : Bool := true
-  beta              : Bool := true
-  eta               : Bool := true
-  etaStruct         : EtaStructMode := .all
-  iota              : Bool := true
-  proj              : Bool := true
-  decide            : Bool := false
-  autoUnfold        : Bool := false
-  /-- If `failIfUnchanged := true`, then calls to `simp`, `dsimp`, or `simp_all`
-  will fail if they do not make progress. -/
-  failIfUnchanged   : Bool := true
-  /-- If `unfoldPartialApp := true`, then calls to `simp`, `dsimp`, or `simp_all`
-  will unfold even partial applications of `f` when we request `f` to be unfolded. -/
-  unfoldPartialApp  : Bool := false
-  deriving Inhabited, BEq
-
-end DSimp
-
-namespace Simp
-
-def defaultMaxSteps := 100000
-
-structure Config where
-  maxSteps          : Nat  := defaultMaxSteps
-  maxDischargeDepth : Nat  := 2
-  contextual        : Bool := false
-  memoize           : Bool := true
-  singlePass        : Bool := false
-  zeta              : Bool := true
-  beta              : Bool := true
-  eta               : Bool := true
-  etaStruct         : EtaStructMode := .all
-  iota              : Bool := true
-  proj              : Bool := true
-  decide            : Bool := false
-  arith             : Bool := false
-  autoUnfold        : Bool := false
-  /--
-    If `dsimp := true`, then switches to `dsimp` on dependent arguments where there is no congruence theorem that allows
-    `simp` to visit them. If `dsimp := false`, then argument is not visited.
-  -/
-  dsimp             : Bool := true
-  /-- If `failIfUnchanged := true`, then calls to `simp`, `dsimp`, or `simp_all`
-  will fail if they do not make progress. -/
-  failIfUnchanged   : Bool := true
-  /-- If `ground := true`, then ground terms are reduced. A term is ground when
-  it does not contain free or meta variables. Reduction is interrupted at a function application `f ...`
-  if `f` is marked to not be unfolded. -/
-  ground            : Bool := false
-  /-- If `unfoldPartialApp := true`, then calls to `simp`, `dsimp`, or `simp_all`
-  will unfold even partial applications of `f` when we request `f` to be unfolded. -/
-  unfoldPartialApp  : Bool := false
-  deriving Inhabited, BEq
-
--- Configuration object for `simp_all`
-structure ConfigCtx extends Config where
-  contextual := true
-
-def neutralConfig : Simp.Config := {
-  zeta              := false
-  beta              := false
-  eta               := false
-  iota              := false
-  proj              := false
-  decide            := false
-  arith             := false
-  autoUnfold        := false
-  ground            := false
-}
-
-end Simp
-
-inductive Occurrences where
-  | all
-  | pos (idxs : List Nat)
-  | neg (idxs : List Nat)
-  deriving Inhabited, BEq
-
-end Lean.Meta

src/Init/Notation.lean

@@ -295,8 +295,7 @@ macro_rules | `($x - $y)   => `(binop% HSub.hSub $x $y)
 macro_rules | `($x * $y)   => `(binop% HMul.hMul $x $y)
 macro_rules | `($x / $y)   => `(binop% HDiv.hDiv $x $y)
 macro_rules | `($x % $y)   => `(binop% HMod.hMod $x $y)
--- exponentiation should be considered a right action (#2220)
-macro_rules | `($x ^ $y)   => `(rightact% HPow.hPow $x $y)
+macro_rules | `($x ^ $y)   => `(binop% HPow.hPow $x $y)
 macro_rules | `($x ++ $y)  => `(binop% HAppend.hAppend $x $y)
 macro_rules | `(- $x)      => `(unop% Neg.neg $x)
 
@@ -461,8 +460,42 @@ expected type is known. So, `without_expected_type` is not effective in this cas
 -/
 macro "without_expected_type " x:term : term => `(let aux := $x; aux)
 
+/--
+The syntax `[a, b, c]` is shorthand for `a :: b :: c :: []`, or
+`List.cons a (List.cons b (List.cons c List.nil))`. It allows conveniently constructing
+list literals.
+
+For lists of length at least 64, an alternative desugaring strategy is used
+which uses let bindings as intermediates as in
+`let left := [d, e, f]; a :: b :: c :: left` to avoid creating very deep expressions.
+Note that this changes the order of evaluation, although it should not be observable
+unless you use side effecting operations like `dbg_trace`.
+-/
+syntax "[" withoutPosition(term,*) "]"  : term
+
+/--
+Auxiliary syntax for implementing `[$elem,*]` list literal syntax.
+The syntax `%[a,b,c|tail]` constructs a value equivalent to `a::b::c::tail`.
+It uses binary partitioning to construct a tree of intermediate let bindings as in
+`let left := [d, e, f]; a :: b :: c :: left` to avoid creating very deep expressions.
+-/
+syntax "%[" withoutPosition(term,* " | " term) "]" : term
+
 namespace Lean
 
+macro_rules
+  | `([ $elems,* ]) => do
+    -- NOTE: we do not have `TSepArray.getElems` yet at this point
+    let rec expandListLit (i : Nat) (skip : Bool) (result : TSyntax `term) : MacroM Syntax := do
+      match i, skip with
+      | 0,   _     => pure result
+      | i+1, true  => expandListLit i false result
+      | i+1, false => expandListLit i true  (← ``(List.cons $(⟨elems.elemsAndSeps.get! i⟩) $result))
+    if elems.elemsAndSeps.size < 64 then
+      expandListLit elems.elemsAndSeps.size false (← ``(List.nil))
+    else
+      `(%[ $elems,* | List.nil ])
+
 /--
 Category for carrying raw syntax trees between macros; any content is printed as is by the pretty printer.
 The only accepted parser for this category is an antiquotation.

src/Init/Prelude.lean

@@ -806,12 +806,6 @@ decidability instance instead of the proposition, which has no code).
 
 If a proposition `p` is `Decidable`, then `(by decide : p)` will prove it by
 evaluating the decidability instance to `isTrue h` and returning `h`.
-
-Because `Decidable` carries data,
-when writing `@[simp]` lemmas which include a `Decidable` instance on the LHS,
-it is best to use `{_ : Decidable p}` rather than `[Decidable p]`
-so that non-canonical instances can be found via unification rather than
-typeclass search.
 -/
 class inductive Decidable (p : Prop) where
   /-- Prove that `p` is decidable by supplying a proof of `¬p` -/
@@ -926,9 +920,7 @@ or derive `i < arr.size` from some other proposition that we are checking in the
 return `t` or `e` depending on whether `c` is true or false. The explicit argument
 `c : Prop` does not have any actual computational content, but there is an additional
 `[Decidable c]` argument synthesized by typeclass inference which actually
-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.
+determines how to evaluate `c` to true or false.
 
 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
@@ -1305,38 +1297,11 @@ class Mod (α : Type u) where
 The homogeneous version of `HPow`: `a ^ b : α` where `a : α`, `b : β`.
 (The right argument is not the same as the left since we often want this even
 in the homogeneous case.)
-
-Types can choose to subscribe to particular defaulting behavior by providing
-an instance to either `NatPow` or `HomogeneousPow`:
-- `NatPow` is for types whose exponents is preferentially a `Nat`.
-- `HomogeneousPow` is for types whose base and exponent are preferentially the same.
 -/
 class Pow (α : Type u) (β : Type v) where
   /-- `a ^ b` computes `a` to the power of `b`. See `HPow`. -/
   pow : α → β → α
 
-/-- The homogenous version of `Pow` where the exponent is a `Nat`.
-The purpose of this class is that it provides a default `Pow` instance,
-which can be used to specialize the exponent to `Nat` during elaboration.
-
-For example, if `x ^ 2` should preferentially elaborate with `2 : Nat` then `x`'s type should
-provide an instance for this class. -/
-class NatPow (α : Type u) where
-  /-- `a ^ n` computes `a` to the power of `n` where `n : Nat`. See `Pow`. -/
-  protected pow : α → Nat → α
-
-/-- The completely homogeneous version of `Pow` where the exponent has the same type as the base.
-The purpose of this class is that it provides a default `Pow` instance,
-which can be used to specialize the exponent to have the same type as the base's type during elaboration.
-This is to say, a type should provide an instance for this class in case `x ^ y` should be elaborated
-with both `x` and `y` having the same type.
-
-For example, the `Float` type provides an instance of this class, which causes expressions
-such as `(2.2 ^ 2.2 : Float)` to elaborate. -/
-class HomogeneousPow (α : Type u) where
-  /-- `a ^ b` computes `a` to the power of `b` where `a` and `b` both have the same type. -/
-  protected pow : α → α → α
-
 /-- The homogeneous version of `HAppend`: `a ++ b : α` where `a b : α`. -/
 class Append (α : Type u) where
   /-- `a ++ b` is the result of concatenation of `a` and `b`. See `HAppend`. -/
@@ -1420,14 +1385,6 @@ instance [Mod α] : HMod α α α where
 instance [Pow α β] : HPow α β α where
   hPow a b := Pow.pow a b
 
-@[default_instance]
-instance [NatPow α] : Pow α Nat where
-  pow a n := NatPow.pow a n
-
-@[default_instance]
-instance [HomogeneousPow α] : Pow α α where
-  pow a b := HomogeneousPow.pow a b
-
 @[default_instance]
 instance [Append α] : HAppend α α α where
   hAppend a b := Append.append a b
@@ -1523,7 +1480,8 @@ protected def Nat.pow (m : @& Nat) : (@& Nat) → Nat
   | 0      => 1
   | succ n => Nat.mul (Nat.pow m n) m
 
-instance : NatPow Nat := ⟨Nat.pow⟩
+instance : Pow Nat Nat where
+  pow := Nat.pow
 
 set_option bootstrap.genMatcherCode false in
 /--
@@ -1816,7 +1774,7 @@ instance Fin.decLt {n} (a b : Fin n) : Decidable (LT.lt a b) := Nat.decLt ..
 instance Fin.decLe {n} (a b : Fin n) : Decidable (LE.le a b) := Nat.decLe ..
 
 /-- The size of type `UInt8`, that is, `2^8 = 256`. -/
-abbrev UInt8.size : Nat := 256
+def UInt8.size : Nat := 256
 
 /--
 The type of unsigned 8-bit integers. This type has special support in the
@@ -1855,7 +1813,7 @@ instance : Inhabited UInt8 where
   default := UInt8.ofNatCore 0 (by decide)
 
 /-- The size of type `UInt16`, that is, `2^16 = 65536`. -/
-abbrev UInt16.size : Nat := 65536
+def UInt16.size : Nat := 65536
 
 /--
 The type of unsigned 16-bit integers. This type has special support in the
@@ -1894,7 +1852,7 @@ instance : Inhabited UInt16 where
   default := UInt16.ofNatCore 0 (by decide)
 
 /-- The size of type `UInt32`, that is, `2^32 = 4294967296`. -/
-abbrev UInt32.size : Nat := 4294967296
+def UInt32.size : Nat := 4294967296
 
 /--
 The type of unsigned 32-bit integers. This type has special support in the
@@ -1971,7 +1929,7 @@ instance : Max UInt32 := maxOfLe
 instance : Min UInt32 := minOfLe
 
 /-- The size of type `UInt64`, that is, `2^64 = 18446744073709551616`. -/
-abbrev UInt64.size : Nat := 18446744073709551616
+def UInt64.size : Nat := 18446744073709551616
 /--
 The type of unsigned 64-bit integers. This type has special support in the
 compiler to make it actually 64 bits rather than wrapping a `Nat`.
@@ -2011,26 +1969,11 @@ instance : Inhabited UInt64 where
 /--
 The size of type `UInt16`, that is, `2^System.Platform.numBits`, which may
 be either `2^32` or `2^64` depending on the platform's architecture.
-
-Remark: we define `USize.size` using `(2^numBits - 1) + 1` to ensure the
-Lean unifier can solve contraints such as `?m + 1 = USize.size`. Recall that
-`numBits` does not reduce to a numeral in the Lean kernel since it is platform
-specific. Without this trick, the following definition would be rejected by the
-Lean type checker.
-```
-def one: Fin USize.size := 1
-```
-Because Lean would fail to synthesize instance `OfNat (Fin USize.size) 1`.
-Recall that the `OfNat` instance for `Fin` is
-```
-instance : OfNat (Fin (n+1)) i where
-  ofNat := Fin.ofNat i
-```
 -/
-abbrev USize.size : Nat := Nat.succ (Nat.sub (hPow 2 System.Platform.numBits) 1)
+def USize.size : Nat := hPow 2 System.Platform.numBits
 
 theorem usize_size_eq : Or (Eq USize.size 4294967296) (Eq USize.size 18446744073709551616) :=
-  show Or (Eq (Nat.succ (Nat.sub (hPow 2 System.Platform.numBits) 1)) 4294967296) (Eq (Nat.succ (Nat.sub (hPow 2 System.Platform.numBits) 1)) 18446744073709551616) from
+  show Or (Eq (hPow 2 System.Platform.numBits) 4294967296) (Eq (hPow 2 System.Platform.numBits) 18446744073709551616) from
   match System.Platform.numBits, System.Platform.numBits_eq with
   | _, Or.inl rfl => Or.inl (by decide)
   | _, Or.inr rfl => Or.inr (by decide)
@@ -2548,22 +2491,13 @@ 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.
-
-From the point of view of proofs `Array α` is just a wrapper around `List α`.
 -/
 structure Array (α : Type u) where
-  /--
-  Converts a `List α` into an `Array α`.
-
-  At runtime, this constructor is implemented by `List.toArray` and is O(n) in the length of the
-  list.
-  -/
+  /-- Convert a `List α` into an `Array α`. This function is overridden
+  to `List.toArray` and is O(n) in the length of the list. -/
   mk ::
-  /--
-  Converts a `Array α` into an `List α`.
-
-  At runtime, this projection is implemented by `Array.toList` and is O(n) in the length of the
-  array. -/
+  /-- Convert an `Array α` into a `List α`. This function is overridden
+  to `Array.toList` and is O(n) in the length of the list. -/
   data : List α
 
 attribute [extern "lean_array_data"] Array.data
@@ -2711,9 +2645,12 @@ def List.redLength : List α → Nat
   | nil       => 0
   | cons _ as => as.redLength.succ
 
-/-- Convert a `List α` into an `Array α`. This is O(n) in the length of the list.  -/
--- This function is exported to C, where it is called by `Array.mk`
--- (the constructor) to implement this functionality.
+/--
+Convert a `List α` into an `Array α`. This is O(n) in the length of the list.
+
+This function is exported to C, where it is called by `Array.mk`
+(the constructor) to implement this functionality.
+-/
 @[inline, match_pattern, export lean_list_to_array]
 def List.toArray (as : List α) : Array α :=
   as.toArrayAux (Array.mkEmpty as.redLength)

src/Init/SimpLemmas.lean

@@ -41,12 +41,6 @@ theorem implies_congr_ctx {p₁ p₂ q₁ q₂ : Prop} (h₁ : p₁ = p₂) (h
 theorem forall_congr {α : Sort u} {p q : α → Prop} (h : ∀ a, p a = q a) : (∀ a, p a) = (∀ a, q a) :=
   (funext h : p = q) ▸ rfl
 
-theorem forall_prop_domain_congr {p₁ p₂ : Prop} {q₁ : p₁ → Prop} {q₂ : p₂ → Prop}
-    (h₁ : p₁ = p₂)
-    (h₂ : ∀ a : p₂, q₁ (h₁.substr a) = q₂ a)
-    : (∀ a : p₁, q₁ a) = (∀ a : p₂, q₂ a) := by
-  subst h₁; simp [← h₂]
-
 theorem let_congr {α : Sort u} {β : Sort v} {a a' : α} {b b' : α → β}
     (h₁ : a = a') (h₂ : ∀ x, b x = b' x) : (let x := a; b x) = (let x := a'; b' x) :=
   h₁ ▸ (funext h₂ : b = b') ▸ rfl
@@ -104,7 +98,6 @@ theorem dite_congr {_ : Decidable b} [Decidable c]
 @[simp] theorem implies_true (α : Sort u) : (α → True) = True := eq_true fun _ => trivial
 @[simp] theorem true_implies (p : Prop) : (True → p) = p := propext ⟨(· trivial), (fun _ => ·)⟩
 @[simp] theorem not_false_eq_true : (¬ False) = True := eq_true False.elim
-@[simp] theorem not_true_eq_false : (¬ True) = False := by decide
 
 @[simp] theorem Bool.or_false (b : Bool) : (b || false) = b  := by cases b <;> rfl
 @[simp] theorem Bool.or_true (b : Bool) : (b || true) = true := by cases b <;> rfl
@@ -143,9 +136,9 @@ theorem Bool.or_assoc (a b c : Bool) : (a || b || c) = (a || (b || c)) := by
 @[simp] theorem Bool.not_eq_true (b : Bool) : (¬(b = true)) = (b = false) := by cases b <;> decide
 @[simp] theorem Bool.not_eq_false (b : Bool) : (¬(b = false)) = (b = true) := by cases b <;> decide
 
-@[simp] theorem decide_eq_true_eq {_ : Decidable p} : (decide p = true) = p := propext <| Iff.intro of_decide_eq_true decide_eq_true
-@[simp] theorem decide_not {h : Decidable p} : decide (¬ p) = !decide p := by cases h <;> rfl
-@[simp] theorem not_decide_eq_true {h : Decidable p} : ((!decide p) = true) = ¬ p := by cases h <;> simp [decide, *]
+@[simp] theorem decide_eq_true_eq [Decidable p] : (decide p = true) = p := propext <| Iff.intro of_decide_eq_true decide_eq_true
+@[simp] theorem decide_not [h : Decidable p] : decide (¬ p) = !decide p := by cases h <;> rfl
+@[simp] theorem not_decide_eq_true [h : Decidable p] : ((!decide p) = true) = ¬ p := by cases h <;> simp [decide, *]
 
 @[simp] theorem heq_eq_eq {α : Sort u} (a b : α) : HEq a b = (a = b) := propext <| Iff.intro eq_of_heq heq_of_eq
 
@@ -159,7 +152,7 @@ theorem Bool.or_assoc (a b c : Bool) : (a || b || c) = (a || (b || c)) := by
 @[simp] theorem bne_self_eq_false' [DecidableEq α] (a : α) : (a != a) = false := by simp [bne]
 
 @[simp] theorem Nat.le_zero_eq (a : Nat) : (a ≤ 0) = (a = 0) :=
-  propext ⟨fun h => Nat.le_antisymm h (Nat.zero_le ..), fun h => by rw [h]; decide⟩
+  propext ⟨fun h => Nat.le_antisymm h (Nat.zero_le ..), fun h => by simp [h]⟩
 
 @[simp] theorem decide_False : decide False = false := rfl
 @[simp] theorem decide_True : decide True = true := rfl

src/Init/System/IO.lean

@@ -328,41 +328,7 @@ namespace FS
 namespace Handle
 
 @[extern "lean_io_prim_handle_mk"] opaque mk (fn : @& FilePath) (mode : FS.Mode) : IO Handle
-
-/--
-Acquires an exclusive or shared lock on the handle.
-Will block to wait for the lock if necessary.
-
-**NOTE:** Acquiring a exclusive lock while already possessing a shared lock
-will NOT reliably succeed (i.e., it works on Unix but not on Windows).
--/
-@[extern "lean_io_prim_handle_lock"] opaque lock (h : @& Handle) (exclusive := true) : IO Unit
-/--
-Tries to acquire an exclusive or shared lock on the handle.
-Will NOT block for the lock, but instead return `false`.
-
-**NOTE:** Acquiring a exclusive lock while already possessing a shared lock
-will NOT reliably succeed (i.e., it works on Unix but not on Windows).
--/
-@[extern "lean_io_prim_handle_try_lock"] opaque tryLock (h : @& Handle) (exclusive := true) : IO Bool
-/--
-Releases any previously acquired lock on the handle.
-Will succeed even if no lock has been acquired.
--/
-@[extern "lean_io_prim_handle_unlock"] opaque unlock (h : @& Handle) : IO Unit
-
 @[extern "lean_io_prim_handle_flush"] opaque flush (h : @& Handle) : IO Unit
-/-- Rewinds the read/write cursor to the beginning of the handle. -/
-@[extern "lean_io_prim_handle_rewind"] opaque rewind (h : @& Handle) : IO Unit
-/--
-Truncates the handle to the read/write cursor.
-
-Does not automatically flush. Usually this is fine because the read/write
-cursor includes buffered writes. However, the combination of buffered writes,
-then `rewind`, then `truncate`, then close may lead to a file with content.
-If unsure, flush before truncating.
--/
-@[extern "lean_io_prim_handle_truncate"] opaque truncate (h : @& Handle) : IO Unit
 /--
 Read up to the given number of bytes from the handle.
 If the returned array is empty, an end-of-file marker has been reached.

src/Init/Tactics.lean

@@ -250,7 +250,7 @@ macro:1 x:tactic tk:" <;> " y:tactic:2 : tactic => `(tactic|
     all_goals $y:tactic)
 
 /-- `eq_refl` is equivalent to `exact rfl`, but has a few optimizations. -/
-syntax (name := eqRefl) "eq_refl" : tactic
+syntax (name := refl) "eq_refl" : tactic
 
 /--
 `rfl` tries to close the current goal using reflexivity.
@@ -435,14 +435,14 @@ non-dependent hypotheses. It has many variants:
   other hypotheses.
 -/
 syntax (name := simp) "simp" (config)? (discharger)? (&" only")?
-  (" [" withoutPosition((simpStar <|> simpErase <|> simpLemma),*,?) "]")? (location)? : tactic
+  (" [" withoutPosition((simpStar <|> simpErase <|> simpLemma),*) "]")? (location)? : tactic
 /--
 `simp_all` is a stronger version of `simp [*] at *` where the hypotheses and target
 are simplified multiple times until no simplification is applicable.
 Only non-dependent propositional hypotheses are considered.
 -/
 syntax (name := simpAll) "simp_all" (config)? (discharger)? (&" only")?
-  (" [" withoutPosition((simpErase <|> simpLemma),*,?) "]")? : tactic
+  (" [" withoutPosition((simpErase <|> simpLemma),*) "]")? : tactic
 
 /--
 The `dsimp` tactic is the definitional simplifier. It is similar to `simp` but only
@@ -450,7 +450,7 @@ applies theorems that hold by reflexivity. Thus, the result is guaranteed to be
 definitionally equal to the input.
 -/
 syntax (name := dsimp) "dsimp" (config)? (discharger)? (&" only")?
-  (" [" withoutPosition((simpErase <|> simpLemma),*,?) "]")? (location)? : tactic
+  (" [" withoutPosition((simpErase <|> simpLemma),*) "]")? (location)? : tactic
 
 /--
 `delta id1 id2 ...` delta-expands the definitions `id1`, `id2`, ....

src/Init/Util.lean

@@ -85,21 +85,3 @@ private def outOfBounds [Inhabited α] : α :=
 
 macro:max x:term noWs "[" i:term "]" noWs "?" : term => `(getElem? $x $i)
 macro:max x:term noWs "[" i:term "]" noWs "!" : term => `(getElem! $x $i)
-
-/--
-  Marks given value and its object graph closure as multi-threaded if currently
-  marked single-threaded. This will make reference counter updates atomic and
-  thus more costly. It can still be useful to do eagerly when the value will be
-  shared between threads later anyway and there is available time budget to mark
-  it now. -/
-@[extern "lean_runtime_mark_multi_threaded"]
-def Runtime.markMultiThreaded (a : α) : α := a
-
-/--
-  Marks given value and its object graph closure as persistent. This will remove
-  reference counter updates but prevent the closure from being deallocated until
-  the end of the process! It can still be useful to do eagerly when the value
-  will be marked persistent later anyway and there is available time budget to
-  mark it now or it would be unnecessarily marked multi-threaded in between. -/
-@[extern "lean_runtime_mark_persistent"]
-def Runtime.markPersistent (a : α) : α := a

src/Init/WFTactics.lean

@@ -5,13 +5,12 @@ Author: Leonardo de Moura
 -/
 prelude
 import Init.SizeOf
-import Init.MetaTypes
 import Init.WF
 
 /-- Unfold definitions commonly used in well founded relation definitions.
 This is primarily intended for internal use in `decreasing_tactic`. -/
 macro "simp_wf" : tactic =>
-  `(tactic| try simp (config := { unfoldPartialApp := true }) [invImage, InvImage, Prod.lex, sizeOfWFRel, measure, Nat.lt_wfRel, WellFoundedRelation.rel])
+  `(tactic| try simp [invImage, InvImage, Prod.lex, sizeOfWFRel, measure, Nat.lt_wfRel, WellFoundedRelation.rel])
 
 /-- Extensible helper tactic for `decreasing_tactic`. This handles the "base case"
 reasoning after applying lexicographic order lemmas.

src/Lean/Compiler/IR/EmitC.lean

@@ -472,7 +472,6 @@ def quoteString (s : String) : String :=
       else if c == '\t' then "\\t"
       else if c == '\\' then "\\\\"
       else if c == '\"' then "\\\""
-      else if c == '?' then "\\?" -- avoid trigraphs
       else if c.toNat <= 31 then
         "\\x" ++ toHexDigit (c.toNat / 16) ++ toHexDigit (c.toNat % 16)
       -- TODO(Leo): we should use `\unnnn` for escaping unicode characters.

src/Lean/Compiler/IR/EmitLLVM.lean

@@ -1541,6 +1541,15 @@ end EmitLLVM
 def getLeanHBcPath : IO System.FilePath := do
   return (← getLibDir (← getBuildDir)) / "lean.h.bc"
 
+def optimizeLLVMModule (mod : LLVM.Module ctx) : IO Unit := do
+  let pm  ← LLVM.createPassManager
+  let pmb ← LLVM.createPassManagerBuilder
+  pmb.setOptLevel 3
+  pmb.populateModulePassManager pm
+  LLVM.runPassManager pm mod
+  LLVM.disposePassManager pm
+  LLVM.disposePassManagerBuilder pmb
+
 /-- Get the names of all global symbols in the module -/
 partial def getModuleGlobals (mod : LLVM.Module llvmctx) : IO (Array (LLVM.Value llvmctx)) := do
   let rec go (v : LLVM.Value llvmctx) (acc : Array (LLVM.Value llvmctx)) : IO (Array (LLVM.Value llvmctx)) := do
@@ -1559,7 +1568,7 @@ partial def getModuleFunctions (mod : LLVM.Module llvmctx) : IO (Array (LLVM.Val
 `emitLLVM` is the entrypoint for the lean shell to code generate LLVM.
 -/
 @[export lean_ir_emit_llvm]
-def emitLLVM (env : Environment) (modName : Name) (filepath : String) : IO Unit := do
+def emitLLVM (env : Environment) (modName : Name) (filepath : String) (tripleStr? : Option String) : IO Unit := do
   LLVM.llvmInitializeTargetInfo
   let llvmctx ← LLVM.createContext
   let module ← LLVM.createModule llvmctx modName.toString
@@ -1592,7 +1601,17 @@ def emitLLVM (env : Environment) (modName : Name) (filepath : String) : IO Unit
            let some fn ← LLVM.getNamedFunction emitLLVMCtx.llvmmodule name
               | throw <| IO.Error.userError s!"ERROR: linked module must have function from runtime module: '{name}'"
            LLVM.setLinkage fn LLVM.Linkage.internal
+
+         optimizeLLVMModule emitLLVMCtx.llvmmodule
          LLVM.writeBitcodeToFile emitLLVMCtx.llvmmodule filepath
+         let tripleStr := tripleStr?.getD (← LLVM.getDefaultTargetTriple)
+         let target ← LLVM.getTargetFromTriple tripleStr
+         let cpu := "generic"
+         let features := ""
+         let targetMachine ← LLVM.createTargetMachine target tripleStr cpu features
+         let codegenType := LLVM.CodegenFileType.ObjectFile
+         LLVM.targetMachineEmitToFile targetMachine emitLLVMCtx.llvmmodule (filepath ++ ".o") codegenType
          LLVM.disposeModule emitLLVMCtx.llvmmodule
+         LLVM.disposeTargetMachine targetMachine
   | .error err => throw (IO.Error.userError err)
 end Lean.IR

src/Lean/Compiler/LCNF/PassManager.lean

@@ -46,7 +46,7 @@ structure Pass where
   Resulting phase.
   -/
   phaseOut : Phase := phase
-  phaseInv : phaseOut ≥ phase := by simp_arith
+  phaseInv : phaseOut ≥ phase := by simp
   /--
   The name of the `Pass`
   -/

src/Lean/CoreM.lean

@@ -65,12 +65,6 @@ structure Context where
   initHeartbeats : Nat := 0
   maxHeartbeats  : Nat := getMaxHeartbeats options
   currMacroScope : MacroScope := firstFrontendMacroScope
-  /--
-  If `catchRuntimeEx = false`, then given `try x catch ex => h ex`,
-  an runtime exception occurring in `x` is not handled by `h`.
-  Recall that runtime exceptions are `maxRecDepth` or `maxHeartbeats`.
-  -/
-  catchRuntimeEx : Bool := false
   deriving Nonempty
 
 /-- CoreM is a monad for manipulating the Lean environment.
@@ -356,42 +350,4 @@ def ImportM.runCoreM (x : CoreM α) : ImportM α := do
   let (a, _) ← x.toIO { options := ctx.opts, fileName := "<ImportM>", fileMap := default } { env := ctx.env }
   return a
 
-/-- Return `true` if the exception was generated by one our resource limits. -/
-def Exception.isRuntime (ex : Exception) : Bool :=
-  ex.isMaxHeartbeat || ex.isMaxRecDepth
-
-/--
-Custom `try-catch` for all monads based on `CoreM`. We don't want to catch "runtime exceptions"
-in these monads, but on `CommandElabM`. See issues #2775 and #2744
--/
-@[inline] protected def Core.tryCatch (x : CoreM α) (h : Exception → CoreM α) : CoreM α := do
-  try
-    x
-  catch ex =>
-    if ex.isRuntime && !(← read).catchRuntimeEx then
-      throw ex
-    else
-      h ex
-
-instance : MonadExceptOf Exception CoreM where
-  throw    := throw
-  tryCatch := Core.tryCatch
-
-@[inline] def Core.withCatchingRuntimeEx (flag : Bool) (x : CoreM α) : CoreM α :=
-  withReader (fun ctx => { ctx with catchRuntimeEx := flag }) x
-
-@[inline] def mapCoreM [MonadControlT CoreM m] [Monad m] (f : forall {α}, CoreM α → CoreM α) {α} (x : m α) : m α :=
-  controlAt CoreM fun runInBase => f <| runInBase x
-
-/--
-Execute `x` with `catchRuntimeEx = flag`. That is, given `try x catch ex => h ex`,
-if `x` throws a runtime exception, the handler `h` will be invoked if `flag = true`
-Recall that
--/
-@[inline] def withCatchingRuntimeEx [MonadControlT CoreM m] [Monad m] (x : m α) : m α :=
-  mapCoreM (Core.withCatchingRuntimeEx true) x
-
-@[inline] def withoutCatchingRuntimeEx [MonadControlT CoreM m] [Monad m] (x : m α) : m α :=
-  mapCoreM (Core.withCatchingRuntimeEx false) x
-
 end Lean

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]'h1.2
-      let xj := a[j]'h2.2
-      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]'h.2)
-  return a'
-
-end Array

src/Lean/Data/JsonRpc.lean

@@ -305,7 +305,7 @@ section
         throw $ userError s!"Expected method '{expectedMethod}', got method '{method}'"
     | _ => throw $ userError s!"Expected JSON-RPC notification, got: '{(toJson m).compress}'"
 
-  def readResponseAs (h : FS.Stream) (nBytes : Nat) (expectedID : RequestID) (α) [FromJson α] : IO (Response α) := do
+  partial def readResponseAs (h : FS.Stream) (nBytes : Nat) (expectedID : RequestID) (α) [FromJson α] : IO (Response α) := do
     let m ← h.readMessage nBytes
     match m with
     | Message.response id result =>
@@ -315,6 +315,7 @@ section
         | Except.error inner => throw $ userError s!"Unexpected result '{result.compress}'\n{inner}"
       else
         throw $ userError s!"Expected id {expectedID}, got id {id}"
+    | Message.notification .. => readResponseAs h nBytes expectedID α
     | _ => throw $ userError s!"Expected JSON-RPC response, got: '{(toJson m).compress}'"
 end
 

src/Lean/Data/KVMap.lean

@@ -97,10 +97,6 @@ def insert : KVMap → Name → DataValue → KVMap
 def contains (m : KVMap) (n : Name) : Bool :=
   (m.find n).isSome
 
-/-- Erase an entry from the map -/
-def erase : KVMap → Name → KVMap
-  | ⟨m⟩, k => ⟨m.filter fun a => a.1 ≠ k⟩
-
 def getString (m : KVMap) (k : Name) (defVal := "") : String :=
   match m.find k with
   | some (DataValue.ofString v) => v
@@ -149,30 +145,6 @@ def setName (m : KVMap) (k : Name) (v : Name) : KVMap :=
 def setSyntax (m : KVMap) (k : Name) (v : Syntax) : KVMap :=
   m.insert k (DataValue.ofSyntax v)
 
-/-- Update a `String` entry based on its current value. -/
-def updateString (m : KVMap) (k : Name) (f : String → String) : KVMap :=
-  m.insert k <| DataValue.ofString <| f <| m.getString k
-
-/-- Update a `Nat` entry based on its current value. -/
-def updateNat (m : KVMap) (k : Name) (f : Nat → Nat) : KVMap :=
-  m.insert k <| DataValue.ofNat <| f <| m.getNat k
-
-/-- Update an `Int` entry based on its current value. -/
-def updateInt (m : KVMap) (k : Name) (f : Int → Int) : KVMap :=
-  m.insert k <| DataValue.ofInt <| f <| m.getInt k
-
-/-- Update a `Bool` entry based on its current value. -/
-def updateBool (m : KVMap) (k : Name) (f : Bool → Bool) : KVMap :=
-  m.insert k <| DataValue.ofBool <| f <| m.getBool k
-
-/-- Update a `Name` entry based on its current value. -/
-def updateName (m : KVMap) (k : Name) (f : Name → Name) : KVMap :=
-  m.insert k <| DataValue.ofName <| f <| m.getName k
-
-/-- Update a `Syntax` entry based on its current value. -/
-def updateSyntax (m : KVMap) (k : Name) (f : Syntax → Syntax) : KVMap :=
-  m.insert k <| DataValue.ofSyntax <| f <| m.getSyntax k
-
 @[inline] protected def forIn.{w, w'} {δ : Type w} {m : Type w → Type w'} [Monad m]
   (kv : KVMap) (init : δ) (f : Name × DataValue → δ → m (ForInStep δ)) : m δ :=
   kv.entries.forIn init f
@@ -190,16 +162,6 @@ def subsetAux : List (Name × DataValue) → KVMap → Bool
 def subset : KVMap → KVMap → Bool
   | ⟨m₁⟩, m₂ => subsetAux m₁ m₂
 
-def mergeBy (mergeFn : Name → DataValue → DataValue → DataValue) (l r : KVMap)
-    : KVMap := Id.run do
-  let mut result := l
-  for ⟨k, vᵣ⟩ in r do
-    if let some vₗ := result.find k then
-      result := result.insert k (mergeFn k vₗ vᵣ)
-    else
-      result := result.insert k vᵣ
-  return result
-
 def eqv (m₁ m₂ : KVMap) : Bool :=
   subset m₁ m₂ && subset m₂ m₁
 
@@ -219,11 +181,6 @@ class Value (α : Type) where
 @[inline] def set {α : Type} [Value α] (m : KVMap) (k : Name) (v : α) : KVMap :=
   m.insert k (Value.toDataValue v)
 
-@[inline] def update {α : Type} [Value α] (m : KVMap) (k : Name) (f : Option α → Option α) : KVMap :=
-  match f (m.get? k) with
-  | some a => m.set k a
-  | none => m.erase k
-
 instance : Value DataValue where
   toDataValue  := id
   ofDataValue? := some

src/Lean/Data/Lsp/Basic.lean

@@ -206,7 +206,7 @@ instance : FromJson DocumentChange where
 [reference](https://microsoft.github.io/language-server-protocol/specifications/lsp/3.17/specification/#workspaceEdit) -/
 structure WorkspaceEdit where
   /-- Changes to existing resources. -/
-  changes? : Option (RBMap DocumentUri TextEditBatch compare) := none
+  changes : RBMap DocumentUri TextEditBatch compare := ∅
   /-- Depending on the client capability
     `workspace.workspaceEdit.resourceOperations` document changes are either
     an array of `TextDocumentEdit`s to express changes to n different text
@@ -220,14 +220,14 @@ structure WorkspaceEdit where
     If a client neither supports `documentChanges` nor
     `workspace.workspaceEdit.resourceOperations` then only plain `TextEdit`s
     using the `changes` property are supported. -/
-  documentChanges? : Option (Array DocumentChange) := none
+  documentChanges : Array DocumentChange := ∅
   /-- A map of change annotations that can be referenced in
       `AnnotatedTextEdit`s or create, rename and delete file / folder
       operations.
 
       Whether clients honor this property depends on the client capability
       `workspace.changeAnnotationSupport`. -/
-  changeAnnotations? : Option (RBMap String ChangeAnnotation compare) := none
+  changeAnnotations : RBMap String ChangeAnnotation compare := ∅
   deriving ToJson, FromJson
 
 namespace WorkspaceEdit
@@ -236,24 +236,24 @@ instance : EmptyCollection WorkspaceEdit := ⟨{}⟩
 
 instance : Append WorkspaceEdit where
   append x y := {
-    changes?           :=
-      match x.changes?, y.changes? with
-      | v, none | none, v => v
-      | some x, some y => x.mergeBy (fun _ v₁ v₂ => v₁ ++ v₂) y
-    documentChanges?   :=
-      match x.documentChanges?, y.documentChanges? with
-      | v, none | none, v => v
-      | some x, some y => x ++ y
-    changeAnnotations? :=
-      match x.changeAnnotations?, y.changeAnnotations? with
-      | v, none | none, v => v
-      | some x, some y => x.mergeBy (fun _ _v₁ v₂ => v₂) y
+    changes           := x.changes.mergeBy (fun _ v₁ v₂ => v₁ ++ v₂) y.changes
+    documentChanges   := x.documentChanges ++ y.documentChanges
+    changeAnnotations := x.changeAnnotations.mergeBy (fun _ _v₁ v₂ => v₂) y.changeAnnotations
   }
 
 def ofTextDocumentEdit (e : TextDocumentEdit) : WorkspaceEdit :=
-  { documentChanges? := #[DocumentChange.edit e]}
+  { documentChanges := #[DocumentChange.edit e]}
 
-def ofTextEdit (doc : VersionedTextDocumentIdentifier) (te : TextEdit) : WorkspaceEdit :=
+def ofTextEdit (uri : DocumentUri) (te : TextEdit) : WorkspaceEdit :=
+  /- [note], there is a bug in vscode where not including the version will cause an error,
+  even though the version field is not used to validate the change.
+
+  References:
+  - [a fix in the wild](https://github.com/stylelint/vscode-stylelint/pull/330/files).
+    Note that the version field needs to be present, even if the value is `undefined`.
+  - [angry comment](https://github.com/tsqllint/tsqllint-vscode-extension/blob/727026fce9f8c6a33d113373666d0776f8f6c23c/server/src/server.ts#L70)
+  -/
+  let doc := {uri, version? := some 0}
   ofTextDocumentEdit { textDocument := doc, edits := #[te]}
 
 end WorkspaceEdit

src/Lean/Data/Lsp/Capabilities.lean

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

src/Lean/Data/Lsp/Ipc.lean

@@ -62,23 +62,8 @@ def readMessage : IpcM JsonRpc.Message := do
 def readRequestAs (expectedMethod : String) (α) [FromJson α] : IpcM (Request α) := do
   (←stdout).readLspRequestAs expectedMethod α
 
-/--
-  Reads response, discarding notifications in between. This function is meant
-  purely for testing where we use `collectDiagnostics` explicitly if we do care
-  about such notifications. -/
-partial def readResponseAs (expectedID : RequestID) (α) [FromJson α] :
-    IpcM (Response α) := do
-  let m ← (←stdout).readLspMessage
-  match m with
-  | Message.response id result =>
-    if id == expectedID then
-      match fromJson? result with
-      | Except.ok v => pure ⟨expectedID, v⟩
-      | Except.error inner => throw $ userError s!"Unexpected result '{result.compress}'\n{inner}"
-    else
-      throw $ userError s!"Expected id {expectedID}, got id {id}"
-  | .notification .. => readResponseAs expectedID α
-  | _ => throw $ userError s!"Expected JSON-RPC response, got: '{(toJson m).compress}'"
+def readResponseAs (expectedID : RequestID) (α) [FromJson α] : IpcM (Response α) := do
+  (←stdout).readLspResponseAs expectedID α
 
 def waitForExit : IpcM UInt32 := do
   (←read).wait

src/Lean/Data/Lsp/LanguageFeatures.lean

@@ -351,16 +351,5 @@ structure FoldingRange where
   kind? : Option FoldingRangeKind := none
   deriving ToJson
 
-structure RenameOptions where
-  prepareProvider : Bool := false
-  deriving FromJson, ToJson
-
-structure RenameParams extends TextDocumentPositionParams where
-  newName : String
-  deriving FromJson, ToJson
-
-structure PrepareRenameParams extends TextDocumentPositionParams
-  deriving FromJson, ToJson
-
 end Lsp
 end Lean

src/Lean/Data/NameTrie.lean

@@ -69,10 +69,4 @@ def NameTrie.forMatchingM [Monad m] (t : NameTrie β) (k : Name) (f : β → m U
 def NameTrie.forM [Monad m] (t : NameTrie β) (f : β → m Unit) : m Unit :=
   t.forMatchingM Name.anonymous f
 
-def NameTrie.matchingToArray (t : NameTrie β) (k : Name) : Array β :=
-  Id.run <| t.foldMatchingM k #[] fun v acc => acc.push v
-
-def NameTrie.toArray (t : NameTrie β) : Array β :=
-  Id.run <| t.foldM #[] fun v acc => acc.push v
-
 end Lean

src/Lean/Elab/App.lean

@@ -1261,7 +1261,7 @@ def elabExplicitUnivs (lvls : Array Syntax) : TermElabM (List Level) := do
 - When we elaborate choice nodes (and overloaded identifiers), we track multiple results using the `observing x` combinator.
   The `observing x` executes `x` and returns a `TermElabResult`.
 
-`observing x` does not check for synthetic sorry's, just an exception. Thus, it may think `x` worked when it didn't
+`observing `x does not check for synthetic sorry's, just an exception. Thus, it may think `x` worked when it didn't
 if a synthetic sorry was introduced. We decided that checking for synthetic sorrys at `observing` is not a good solution
 because it would not be clear to decide what the "main" error message for the alternative is. When the result contains
 a synthetic `sorry`, it is not clear which error message corresponds to the `sorry`. Moreover, while executing `x`, many

src/Lean/Elab/BuiltinCommand.lean

@@ -118,64 +118,6 @@ private partial def elabChoiceAux (cmds : Array Syntax) (i : Nat) : CommandElabM
 @[builtin_command_elab choice] def elabChoice : CommandElab := fun stx =>
   elabChoiceAux stx.getArgs 0
 
-/-- Declares one or more universe variables.
-
-`universe u v`
-
-`Prop`, `Type`, `Type u` and `Sort u` are types that classify other types, also known as
-*universes*. In `Type u` and `Sort u`, the variable `u` stands for the universe's *level*, and a
-universe at level `u` can only classify universes that are at levels lower than `u`. For more
-details on type universes, please refer to [the relevant chapter of Theorem Proving in Lean][tpil
-universes].
-
-Just as type arguments allow polymorphic definitions to be used at many different types, universe
-parameters, represented by universe variables, allow a definition to be used at any required level.
-While Lean mostly handles universe levels automatically, declaring them explicitly can provide more
-control when writing signatures. The `universe` keyword allows the declared universe variables to be
-used in a collection of definitions, and Lean will ensure that these definitions use them
-consistently.
-
-[tpil universes]: https://lean-lang.org/theorem_proving_in_lean4/dependent_type_theory.html#types-as-objects
-(Type universes on Theorem Proving in Lean)
-
-```lean
-/- Explicit type-universe parameter. -/
-def id₁.{u} (α : Type u) (a : α) := a
-
-/- Implicit type-universe parameter, equivalent to `id₁`.
-  Requires option `autoImplicit true`, which is the default. -/
-def id₂ (α : Type u) (a : α) := a
-
-/- Explicit standalone universe variable declaration, equivalent to `id₁` and `id₂`. -/
-universe u
-def id₃ (α : Type u) (a : α) := a
-```
-
-On a more technical note, using a universe variable only in the right-hand side of a definition
-causes an error if the universe has not been declared previously.
-
-```lean
-def L₁.{u} := List (Type u)
-
--- def L₂ := List (Type u) -- error: `unknown universe level 'u'`
-
-universe u
-def L₃ := List (Type u)
-```
-
-## Examples
-
-```lean
-universe u v w
-
-structure Pair (α : Type u) (β : Type v) : Type (max u v) where
-  a : α
-  b : β
-
-#check Pair.{v, w}
--- Pair : Type v → Type w → Type (max v w)
-```
--/
 @[builtin_command_elab «universe»] def elabUniverse : CommandElab := fun n => do
   n[1].forArgsM addUnivLevel
 
@@ -184,30 +126,6 @@ structure Pair (α : Type u) (β : Type v) : Type (max u v) where
   | Except.ok env   => setEnv env
   | Except.error ex => throwError (ex.toMessageData (← getOptions))
 
-/-- Adds names from other namespaces to the current namespace.
-
-The command `export Some.Namespace (name₁ name₂)` makes `name₁` and `name₂`:
-
-- visible in the current namespace without prefix `Some.Namespace`, like `open`, and
-- visible from outside the current namespace `N` as `N.name₁` and `N.name₂`.
-
-## Examples
-
-```lean
-namespace Morning.Sky
-  def star := "venus"
-end Morning.Sky
-
-namespace Evening.Sky
-  export Morning.Sky (star)
-  -- `star` is now in scope
-  #check star
-end Evening.Sky
-
--- `star` is visible in `Evening.Sky`
-#check Evening.Sky.star
-```
--/
 @[builtin_command_elab «export»] def elabExport : CommandElab := fun stx => do
   let `(export $ns ($ids*)) := stx | throwUnsupportedSyntax
   let nss ← resolveNamespace ns
@@ -217,123 +135,9 @@ end Evening.Sky
   for idStx in ids do
     let id := idStx.getId
     let declName ← resolveNameUsingNamespaces nss idStx
-    if (← getInfoState).enabled then
-      addConstInfo idStx declName
     aliases := aliases.push (currNamespace ++ id, declName)
   modify fun s => { s with env := aliases.foldl (init := s.env) fun env p => addAlias env p.1 p.2 }
 
-/-- Makes names from other namespaces visible without writing the namespace prefix.
-
-Names that are made available with `open` are visible within the current `section` or `namespace`
-block. This makes referring to (type) definitions and theorems easier, but note that it can also
-make [scoped instances], notations, and attributes from a different namespace available.
-
-The `open` command can be used in a few different ways:
-
-* `open Some.Namespace.Path1 Some.Namespace.Path2` makes all non-protected names in
-  `Some.Namespace.Path1` and `Some.Namespace.Path2` available without the prefix, so that
-  `Some.Namespace.Path1.x` and `Some.Namespace.Path2.y` can be referred to by writing only `x` and
-  `y`.
-
-* `open Some.Namespace.Path hiding def1 def2` opens all non-protected names in `Some.Namespace.Path`
-  except `def1` and `def2`.
-
-* `open Some.Namespace.Path (def1 def2)` only makes `Some.Namespace.Path.def1` and
-  `Some.Namespace.Path.def2` available without the full prefix, so `Some.Namespace.Path.def3` would
-  be unaffected.
-
-  This works even if `def1` and `def2` are `protected`.
-
-* `open Some.Namespace.Path renaming def1 → def1', def2 → def2'` same as `open Some.Namespace.Path
-  (def1 def2)` but `def1`/`def2`'s names are changed to `def1'`/`def2'`.
-
-  This works even if `def1` and `def2` are `protected`.
-
-* `open scoped Some.Namespace.Path1 Some.Namespace.Path2` **only** opens [scoped instances],
-  notations, and attributes from `Namespace1` and `Namespace2`; it does **not** make any other name
-  available.
-
-* `open <any of the open shapes above> in` makes the names `open`-ed visible only in the next
-  command or expression.
-
-[scoped instance]: https://lean-lang.org/theorem_proving_in_lean4/type_classes.html#scoped-instances
-(Scoped instances in Theorem Proving in Lean)
-
-
-## Examples
-
-```lean
-/-- SKI combinators https://en.wikipedia.org/wiki/SKI_combinator_calculus -/
-namespace Combinator.Calculus
-  def I (a : α) : α := a
-  def K (a : α) : β → α := fun _ => a
-  def S (x : α → β → γ) (y : α → β) (z : α) : γ := x z (y z)
-end Combinator.Calculus
-
-section
-  -- open everything under `Combinator.Calculus`, *i.e.* `I`, `K` and `S`,
-  -- until the section ends
-  open Combinator.Calculus
-
-  theorem SKx_eq_K : S K x = I := rfl
-end
-
--- open everything under `Combinator.Calculus` only for the next command (the next `theorem`, here)
-open Combinator.Calculus in
-theorem SKx_eq_K' : S K x = I := rfl
-
-section
-  -- open only `S` and `K` under `Combinator.Calculus`
-  open Combinator.Calculus (S K)
-
-  theorem SKxy_eq_y : S K x y = y := rfl
-
-  -- `I` is not in scope, we have to use its full path
-  theorem SKxy_eq_Iy : S K x y = Combinator.Calculus.I y := rfl
-end
-
-section
-  open Combinator.Calculus
-    renaming
-      I → identity,
-      K → konstant
-
-  #check identity
-  #check konstant
-end
-
-section
-  open Combinator.Calculus
-    hiding S
-
-  #check I
-  #check K
-end
-
-section
-  namespace Demo
-    inductive MyType
-    | val
-
-    namespace N1
-      scoped infix:68 " ≋ " => BEq.beq
-
-      scoped instance : BEq MyType where
-        beq _ _ := true
-
-      def Alias := MyType
-    end N1
-  end Demo
-
-  -- bring `≋` and the instance in scope, but not `Alias`
-  open scoped Demo.N1
-
-  #check Demo.MyType.val == Demo.MyType.val
-  #check Demo.MyType.val ≋ Demo.MyType.val
-  -- #check Alias -- unknown identifier 'Alias'
-end
-```
--/
 @[builtin_command_elab «open»] def elabOpen : CommandElab
   | `(open $decl:openDecl) => do
     let openDecls ← elabOpenDecl decl
@@ -419,102 +223,6 @@ private def replaceBinderAnnotation (binder : TSyntax ``Parser.Term.bracketedBin
   else
     return #[binder]
 
-/-- Declares one or more typed variables, or modifies whether already-declared variables are
-implicit.
-
-Introduces variables that can be used in definitions within the same `namespace` or `section` block.
-When a definition mentions a variable, Lean will add it as an argument of the definition. The
-`variable` command is also able to add typeclass parameters. This is useful in particular when
-writing many definitions that have parameters in common (see below for an example).
-
-Variable declarations have the same flexibility as regular function paramaters. In particular they
-can be [explicit, implicit][binder docs], or [instance implicit][tpil classes] (in which case they
-can be anonymous). This can be changed, for instance one can turn explicit variable `x` into an
-implicit one with `variable {x}`. Note that currently, you should avoid changing how variables are
-bound and declare new variables at the same time; see [issue 2789] for more on this topic.
-
-See [*Variables and Sections* from Theorem Proving in Lean][tpil vars] for a more detailed
-discussion.
-
-[tpil vars]: https://lean-lang.org/theorem_proving_in_lean4/dependent_type_theory.html#variables-and-sections
-(Variables and Sections on Theorem Proving in Lean)
-[tpil classes]: https://lean-lang.org/theorem_proving_in_lean4/type_classes.html
-(Type classes on Theorem Proving in Lean)
-[binder docs]: https://leanprover-community.github.io/mathlib4_docs/Lean/Expr.html#Lean.BinderInfo
-(Documentation for the BinderInfo type)
-[issue 2789]: https://github.com/leanprover/lean4/issues/2789
-(Issue 2789 on github)
-
-## Examples
-
-```lean
-section
-  variable
-    {α : Type u}      -- implicit
-    (a : α)           -- explicit
-    [instBEq : BEq α] -- instance implicit, named
-    [Hashable α]      -- instance implicit, anonymous
-
-  def isEqual (b : α) : Bool :=
-    a == b
-
-  #check isEqual
-  -- isEqual.{u} {α : Type u} (a : α) [instBEq : BEq α] (b : α) : Bool
-
-  variable
-    {a} -- `a` is implicit now
-
-  def eqComm {b : α} := a == b ↔ b == a
-
-  #check eqComm
-  -- eqComm.{u} {α : Type u} {a : α} [instBEq : BEq α] {b : α} : Prop
-end
-```
-
-The following shows a typical use of `variable` to factor out definition arguments:
-
-```lean
-variable (Src : Type)
-
-structure Logger where
-  trace : List (Src × String)
-#check Logger
--- Logger (Src : Type) : Type
-
-namespace Logger
-  -- switch `Src : Type` to be implicit until the `end Logger`
-  variable {Src}
-
-  def empty : Logger Src where
-    trace := []
-  #check empty
-  -- Logger.empty {Src : Type} : Logger Src
-
-  variable (log : Logger Src)
-
-  def len :=
-    log.trace.length
-  #check len
-  -- Logger.len {Src : Type} (log : Logger Src) : Nat
-
-  variable (src : Src) [BEq Src]
-
-  -- at this point all of `log`, `src`, `Src` and the `BEq` instance can all become arguments
-
-  def filterSrc :=
-    log.trace.filterMap
-      fun (src', str') => if src' == src then some str' else none
-  #check filterSrc
-  -- Logger.filterSrc {Src : Type} (log : Logger Src) (src : Src) [inst✝ : BEq Src] : List String
-
-  def lenSrc :=
-    log.filterSrc src |>.length
-  #check lenSrc
-  -- Logger.lenSrc {Src : Type} (log : Logger Src) (src : Src) [inst✝ : BEq Src] : Nat
-end Logger
-```
-
--/
 @[builtin_command_elab «variable»] def elabVariable : CommandElab
   | `(variable $binders*) => do
     -- Try to elaborate `binders` for sanity checking

src/Lean/Elab/BuiltinNotation.lean

@@ -252,21 +252,11 @@ def elabCDotFunctionAlias? (stx : Term) : TermElabM (Option Expr) := do
       try Term.resolveId? f catch _ => return none
     else
       return none
-  | `(fun $binders* => binop% $f $a $b)
-  | `(fun $binders* => binop_lazy% $f $a $b)
-  | `(fun $binders* => leftact% $f $a $b)
-  | `(fun $binders* => rightact% $f $a $b)
-  | `(fun $binders* => binrel% $f $a $b)
-  | `(fun $binders* => binrel_no_prop% $f $a $b) =>
+  | `(fun $binders* => binop% $f $a $b) =>
     if binders == #[a, b] then
       try Term.resolveId? f catch _ => return none
     else
       return none
-  | `(fun $binders* => unop% $f $a) =>
-    if binders == #[a] then
-      try Term.resolveId? f catch _ => return none
-    else
-      return none
   | _ => return none
 where
   expandCDotArg? (stx : Term) : MacroM (Option Term) :=

src/Lean/Elab/Declaration.lean

@@ -348,7 +348,7 @@ def elabMutual : CommandElab := fun stx => do
         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/Deriving/DecEq.lean

@@ -24,15 +24,15 @@ where
     | [] => ``(isTrue rfl)
     | (a, b, recField, isProof) :: todo => withFreshMacroScope do
       let rhs ← if isProof then
-        `(have h : @$a = @$b := rfl; by subst h; exact $(← mkSameCtorRhs todo):term)
+        `(have h : $a = $b := rfl; by subst h; exact $(← mkSameCtorRhs todo):term)
       else
-        `(if h : @$a = @$b then
+        `(if h : $a = $b then
            by subst h; exact $(← mkSameCtorRhs todo):term
           else
            isFalse (by intro n; injection n; apply h _; assumption))
       if let some auxFunName := recField then
         -- add local instance for `a = b` using the function being defined `auxFunName`
-        `(let inst := $(mkIdent auxFunName) @$a @$b; $rhs)
+        `(let inst := $(mkIdent auxFunName) $a $b; $rhs)
       else
         return rhs
 
@@ -113,11 +113,7 @@ def mkDecEq (declName : Name) : CommandElabM Bool := do
     return false -- nested inductive types are not supported yet
   else
     let cmds ← liftTermElabM <| mkDecEqCmds indVal
-    -- `cmds` can have a number of syntax nodes quadratic in the number of constructors
-    -- and thus create as many info tree nodes, which we never make use of but which can
-    -- significantly slow down e.g. the unused variables linter; avoid creating them
-    withEnableInfoTree false do
-      cmds.forM elabCommand
+    cmds.forM elabCommand
     return true
 
 partial def mkEnumOfNat (declName : Name) : MetaM Unit := do

src/Lean/Elab/Extra.lean

@@ -1,7 +1,7 @@
 /-
 Copyright (c) 2021 Microsoft Corporation. All rights reserved.
 Released under Apache 2.0 license as described in the file LICENSE.
-Authors: Leonardo de Moura, Kyle Miller, Sebastian Ullrich
+Authors: Leonardo de Moura
 -/
 import Lean.Elab.App
 import Lean.Elab.BuiltinNotation
@@ -79,30 +79,13 @@ private def throwForInFailure (forInInstance : Expr) : TermElabM Expr :=
 namespace Op
 /-!
 
-The elaborator for expression trees of `binop%`, `binop_lazy%`, `leftact%`, `rightact%`, and `unop%` terms.
+The elaborator for `binop%`, `binop_lazy%`, and `unop%` terms.
 
-At a high level, the elaborator tries to solve for a type that each of the operands in the expression tree
-can be coerced to, while taking into account the expected type for the entire expression tree.
-Once this type is computed (and if it exists), it inserts coercions where needed.
-
-Here are brief descriptions of each of the operator types:
-- `binop% f a b` elaborates `f a b` as a binary operator with two operands `a` and `b`,
-  and each operand participates in the protocol.
-- `binop_lazy% f a b` is like `binop%` but elaborates as `f a (fun () => b)`.
-- `unop% f a` elaborates `f a` as a unary operator with one operand `a`, which participates in the protocol.
-- `leftact% f a b` elaborates `f a b` as a left action (the `a` operand "acts upon" the `b` operand).
-  Only `b` participates in the protocol since `a` can have an unrelated type, for example scalar multiplication of vectors.
-- `rightact% f a b` elaborates `f a b` as a right action (the `b` operand "acts upon" the `a` operand).
-  Only `a` participates in the protocol since `b` can have an unrelated type.
-  This is used by `HPow` since, for example, there are both `Real -> Nat -> Real` and `Real -> Real -> Real`
-  exponentiation functions, and we prefer the former in the case of `x ^ 2`, but `binop%` would choose the latter. (#2220)
-- There are also `binrel%` and `binrel_no_prop%` (see the docstring for `elabBinRelCore`).
-
-The elaborator works as follows:
+It works as follows:
 
 1- Expand macros.
-2- Convert `Syntax` object corresponding to the `binop%/...` term into a `Tree`.
-   The `toTree` method visits nested `binop%/...` terms and parentheses.
+2- Convert `Syntax` object corresponding to the `binop%` (`binop_lazy%` and `unop%`) term into a `Tree`.
+   The `toTree` method visits nested `binop%` (`binop_lazy%` and `unop%`) terms and parentheses.
 3- Synthesize pending metavariables without applying default instances and using the
    `(mayPostpone := true)`.
 4- Tries to compute a maximal type for the tree computed at step 2.
@@ -134,29 +117,18 @@ coercions inside of a `HAdd` instance.
 
 Remarks:
 
-* In the new `binop%` and related elaborators the decision whether a coercion will be inserted or not
-  is made at `binop%` elaboration time. This was not the case in the old elaborator.
-  For example, an instance, such as `HAdd Int ?m ?n`, could be created when executing
-  the `binop%` elaborator, and only resolved much later. We try to minimize this problem
-  by synthesizing pending metavariables at step 3.
+In the new `binop%` and related elaborators the decision whether a coercion will be inserted or not
+is made at `binop%` elaboration time. This was not the case in the old elaborator.
+For example, an instance, such as `HAdd Int ?m ?n`, could be created when executing
+the `binop%` elaborator, and only resolved much later. We try to minimize this problem
+by synthesizing pending metavariables at step 3.
 
-* For types containing heterogeneous operators (e.g., matrix multiplication), step 4 will fail
-  and we will skip coercion insertion. For example, `x : Matrix Real 5 4` and `y : Matrix Real 4 8`,
-  there is no coercion `Matrix Real 5 4` from `Matrix Real 4 8` and vice-versa, but
-  `x * y` is elaborated successfully and has type `Matrix Real 5 8`.
-
-* The `leftact%` and `rightact%` elaborators are to handle binary operations where only one of
-  the arguments participates in the protocol. For example, in `2 ^ n + y` with `n : Nat` and `y : Real`,
-  we do not want to coerce `n` to be a real as well, but we do want to elaborate `2 : Real`.
+For types containing heterogeneous operators (e.g., matrix multiplication), step 4 will fail
+and we will skip coercion insertion. For example, `x : Matrix Real 5 4` and `y : Matrix Real 4 8`,
+there is no coercion `Matrix Real 5 4` from `Matrix Real 4 8` and vice-versa, but
+`x * y` is elaborated successfully and has type `Matrix Real 5 8`.
 -/
 
-private inductive BinOpKind where
-  | regular   -- `binop%`
-  | lazy      -- `binop_lazy%`
-  | leftact   -- `leftact%`
-  | rightact  -- `rightact%`
-deriving BEq
-
 private inductive Tree where
   /--
   Leaf of the tree.
@@ -165,9 +137,9 @@ private inductive Tree where
   -/
   | term (ref : Syntax) (infoTrees : PersistentArray InfoTree) (val : Expr)
   /--
-  `ref` is the original syntax that expanded into `binop%/...`.
+  `ref` is the original syntax that expanded into `binop%`.
   -/
-  | binop (ref : Syntax) (kind : BinOpKind) (f : Expr) (lhs rhs : Tree)
+  | binop (ref : Syntax) (lazy : Bool) (f : Expr) (lhs rhs : Tree)
   /--
   `ref` is the original syntax that expanded into `unop%`.
   -/
@@ -192,11 +164,9 @@ private partial def toTree (s : Syntax) : TermElabM Tree := do
 where
   go (s : Syntax) := do
     match s with
-    | `(binop% $f $lhs $rhs) => processBinOp s .regular f lhs rhs
-    | `(binop_lazy% $f $lhs $rhs) => processBinOp s .lazy f lhs rhs
+    | `(binop% $f $lhs $rhs) => processBinOp (lazy := false) s f lhs rhs
+    | `(binop_lazy% $f $lhs $rhs) => processBinOp (lazy := true) s f lhs rhs
     | `(unop% $f $arg) => processUnOp s f arg
-    | `(leftact% $f $lhs $rhs) => processBinOp s .leftact f lhs rhs
-    | `(rightact% $f $lhs $rhs) => processBinOp s .rightact f lhs rhs
     | `(($e)) =>
       if hasCDot e then
         processLeaf s
@@ -211,12 +181,9 @@ where
             return .macroExpansion macroName s s' (← go s')
         | none => processLeaf s
 
-  processBinOp (ref : Syntax) (kind : BinOpKind) (f lhs rhs : Syntax) := do
+  processBinOp (ref : Syntax) (f lhs rhs : Syntax) (lazy : Bool) := do
     let some f ← resolveId? f | throwUnknownConstant f.getId
-    -- treat corresponding argument as leaf for `leftact/rightact`
-    let lhs ← if kind == .leftact then processLeaf lhs else go lhs
-    let rhs ← if kind == .rightact then processLeaf rhs else go rhs
-    return .binop ref kind f lhs rhs
+    return .binop (lazy := lazy) ref f (← go lhs) (← go rhs)
 
   processUnOp (ref : Syntax) (f arg : Syntax) := do
     let some f ← resolveId? f | throwUnknownConstant f.getId
@@ -262,8 +229,6 @@ where
      unless (← get).hasUncomparable do
        match t with
        | .macroExpansion _ _ _ nested => go nested
-       | .binop _ .leftact  _ _ rhs => go rhs
-       | .binop _ .rightact _ lhs _ => go lhs
        | .binop _ _ _ lhs rhs => go lhs; go rhs
        | .unop _ _ arg => go arg
        | .term _ _ val =>
@@ -294,9 +259,9 @@ private def toExprCore (t : Tree) : TermElabM Expr := do
   match t with
   | .term _ trees e =>
     modifyInfoState (fun s => { s with trees := s.trees ++ trees }); return e
-  | .binop ref kind f lhs rhs =>
+  | .binop ref lazy f lhs rhs =>
     withRef ref <| withInfoContext' ref (mkInfo := mkTermInfo .anonymous ref) do
-      mkBinOp (kind == .lazy) f (← toExprCore lhs) (← toExprCore rhs)
+      mkBinOp lazy f (← toExprCore lhs) (← toExprCore rhs)
   | .unop ref f arg =>
     withRef ref <| withInfoContext' ref (mkInfo := mkTermInfo .anonymous ref) do
       mkUnOp f (← toExprCore arg)
@@ -382,11 +347,7 @@ mutual
   where
     go (t : Tree) (f? : Option Expr) (lhs : Bool) (isPred : Bool) : TermElabM Tree := do
       match t with
-      | .binop ref .leftact f lhs rhs =>
-        return .binop ref .leftact f lhs (← go rhs none false false)
-      | .binop ref .rightact f lhs rhs =>
-        return .binop ref .rightact f (← go lhs none false false) rhs
-      | .binop ref kind f lhs rhs =>
+      | .binop ref lazy f lhs rhs =>
         /-
           We only keep applying coercions to `maxType` if `f` is predicate or
           `f` has a homogenous instance with `maxType`. See `hasHomogeneousInstance` for additional details.
@@ -394,10 +355,10 @@ mutual
           Remark: We assume `binrel%` elaborator is only used with homogenous predicates.
         -/
         if (← pure isPred <||> hasHomogeneousInstance f maxType) then
-          return .binop ref kind f (← go lhs f true false) (← go rhs f false false)
+          return .binop ref lazy f (← go lhs f true false) (← go rhs f false false)
         else
           let r ← withRef ref do
-            mkBinOp (kind == .lazy) f (← toExpr lhs none) (← toExpr rhs none)
+            mkBinOp lazy f (← toExpr lhs none) (← toExpr rhs none)
           let infoTrees ← getResetInfoTrees
           return .term ref infoTrees r
       | .unop ref f arg =>
@@ -435,24 +396,22 @@ end
 def elabOp : TermElab := fun stx expectedType? => do
   toExpr (← toTree stx) expectedType?
 
-@[builtin_term_elab binop] def elabBinOp : TermElab := elabOp
-@[builtin_term_elab binop_lazy] def elabBinOpLazy : TermElab := elabOp
-@[builtin_term_elab leftact] def elabLeftact : TermElab := elabOp
-@[builtin_term_elab rightact] def elabRightact : TermElab := elabOp
-@[builtin_term_elab unop] def elabUnOp : TermElab := elabOp
+@[builtin_term_elab binop]
+def elabBinOp : TermElab := elabOp
+
+@[builtin_term_elab binop_lazy]
+def elabBinOpLazy : TermElab := elabOp
+
+@[builtin_term_elab unop]
+def elabUnOp : TermElab := elabOp
 
 /--
-  Elaboration functions for `binrel%` and `binrel_no_prop%` notations.
+  Elaboration functionf for `binrel%` and `binrel_no_prop%` notations.
   We use the infrastructure for `binop%` to make sure we propagate information between the left and right hand sides
   of a binary relation.
 
-  - `binrel% R x y` elaborates `R x y` using the `binop%/...` expression trees in both `x` and `y`.
-    It is similar to how `binop% R x y` elaborates but with a significant difference:
-    it does not use the expected type when computing the types of the operads.
-  - `binrel_no_prop% R x y` elaborates `R x y` like `binrel% R x y`, but if the resulting type for `x` and `y`
-    is `Prop` they are coerced to `Bool`.
-    This is used for relations such as `==` which do not support `Prop`, but we still want
-    to be able to write `(5 > 2) == (2 > 1)` for example.
+  Recall that the `binrel_no_prop%` notation is used for relations such as `==` which do not support `Prop`, but
+  we still want to be able to write `(5 > 2) == (2 > 1)`.
 -/
 def elabBinRelCore (noProp : Bool) (stx : Syntax) (expectedType? : Option Expr) : TermElabM Expr :=  do
   match (← resolveId? stx[1]) with
@@ -489,7 +448,7 @@ def elabBinRelCore (noProp : Bool) (stx : Syntax) (expectedType? : Option Expr)
     -/
     let lhs ← withRef stx[2] <| toTree stx[2]
     let rhs ← withRef stx[3] <| toTree stx[3]
-    let tree := .binop stx .regular f lhs rhs
+    let tree := .binop (lazy := false) stx f lhs rhs
     let r ← analyze tree none
     trace[Elab.binrel] "hasUncomparable: {r.hasUncomparable}, maxType: {r.max?}"
     if r.hasUncomparable || r.max?.isNone then

src/Lean/Elab/Frontend.lean

@@ -102,8 +102,7 @@ def runFrontend
     : IO (Environment × Bool) := do
   let inputCtx := Parser.mkInputContext input fileName
   let (header, parserState, messages) ← Parser.parseHeader inputCtx
-  -- allow `env` to be leaked, which would live until the end of the process anyway
-  let (env, messages) ← processHeader (leakEnv := true) header opts messages inputCtx trustLevel
+  let (env, messages) ← processHeader header opts messages inputCtx trustLevel
   let env := env.setMainModule mainModuleName
   let mut commandState := Command.mkState env messages opts
 

src/Lean/Elab/Import.lean

@@ -16,11 +16,10 @@ def headerToImports (header : Syntax) : Array Import :=
     let id      := stx[2].getId
     { module := id, runtimeOnly := runtime }
 
-def processHeader (header : Syntax) (opts : Options) (messages : MessageLog)
-    (inputCtx : Parser.InputContext) (trustLevel : UInt32 := 0) (leakEnv := false)
+def processHeader (header : Syntax) (opts : Options) (messages : MessageLog) (inputCtx : Parser.InputContext) (trustLevel : UInt32 := 0)
     : IO (Environment × MessageLog) := do
   try
-    let env ← importModules (leakEnv := leakEnv) (headerToImports header) opts trustLevel
+    let env ← importModules (headerToImports header) opts trustLevel
     pure (env, messages)
   catch e =>
     let env ← mkEmptyEnvironment

src/Lean/Elab/Open.lean

@@ -57,7 +57,7 @@ private def resolveNameUsingNamespacesCore (nss : List Name) (idStx : Syntax) :
   else
     withRef idStx do throwError "ambiguous identifier '{idStx.getId}', possible interpretations: {result.map mkConst}"
 
-def elabOpenDecl [MonadResolveName m] [MonadInfoTree m] (stx : TSyntax ``Parser.Command.openDecl) : m (List OpenDecl) := do
+def elabOpenDecl [MonadResolveName m] (stx : TSyntax ``Parser.Command.openDecl) : m (List OpenDecl) := do
   StateRefT'.run' (s := { openDecls := (← getOpenDecls), currNamespace := (← getCurrNamespace) }) do
     match stx with
     | `(Parser.Command.openDecl| $nss*) =>
@@ -73,25 +73,18 @@ def elabOpenDecl [MonadResolveName m] [MonadInfoTree m] (stx : TSyntax ``Parser.
       let nss ← resolveNamespace ns
       for idStx in ids do
         let declName ← resolveNameUsingNamespacesCore nss idStx
-        if (← getInfoState).enabled then
-          addConstInfo idStx declName
         addOpenDecl (OpenDecl.explicit idStx.getId declName)
     | `(Parser.Command.openDecl| $ns hiding $ids*) =>
       let ns ← resolveUniqueNamespace ns
       activateScoped ns
       for id in ids do
-        let declName ← resolveId ns id
-        if (← getInfoState).enabled then
-          addConstInfo id declName
+        let _ ← resolveId ns id
       let ids := ids.map (·.getId) |>.toList
       addOpenDecl (OpenDecl.simple ns ids)
     | `(Parser.Command.openDecl| $ns renaming $[$froms -> $tos],*) =>
       let ns ← resolveUniqueNamespace ns
       for («from», to) in froms.zip tos do
         let declName ← resolveId ns «from»
-        if (← getInfoState).enabled then
-          addConstInfo «from» declName
-          addConstInfo to declName
         addOpenDecl (OpenDecl.explicit to.getId declName)
     | _ => throwUnsupportedSyntax
     return (← get).openDecls

src/Lean/Elab/PreDefinition/Basic.lean

@@ -62,7 +62,7 @@ def applyAttributesOf (preDefs : Array PreDefinition) (applicationTime : Attribu
   for preDef in preDefs do
     applyAttributesAt preDef.declName preDef.modifiers.attrs applicationTime
 
-def abstractNestedProofs (preDef : PreDefinition) : MetaM PreDefinition := withRef preDef.ref do
+def abstractNestedProofs (preDef : PreDefinition) : MetaM PreDefinition :=
   if preDef.kind.isTheorem || preDef.kind.isExample then
     pure preDef
   else do

src/Lean/Elab/PreDefinition/Structural/BRecOn.lean

@@ -113,12 +113,12 @@ private partial def replaceRecApps (recFnName : Name) (recArgInfo : RecArgInfo)
     | Expr.letE n type val body _ =>
       withLetDecl n (← loop below type) (← loop below val) fun x => do
         mkLetFVars #[x] (← loop below (body.instantiate1 x)) (usedLetOnly := false)
-    | Expr.mdata d b =>
-      if let some stx := getRecAppSyntax? e then
-        withRef stx <| loop below b
+    | Expr.mdata d b     =>
+      if let some _ := getRecAppSyntax? e then
+        loop below b
       else
         return mkMData d (← loop below b)
-    | Expr.proj n i e => return mkProj n i (← loop below e)
+    | Expr.proj n i e    => return mkProj n i (← loop below e)
     | Expr.app _ _ =>
       let processApp (e : Expr) : StateRefT (HasConstCache recFnName) M Expr :=
         e.withApp fun f args => do

src/Lean/Elab/PreDefinition/Structural/IndPred.lean

@@ -23,11 +23,7 @@ private partial def replaceIndPredRecApps (recFnName : Name) (recArgInfo : RecAr
     | Expr.letE n type val body _ =>
       withLetDecl n (← loop type) (← loop val) fun x => do
         mkLetFVars #[x] (← loop (body.instantiate1 x))
-    | Expr.mdata d b => do
-      if let some stx := getRecAppSyntax? e then
-        withRef stx <| loop b
-      else
-        return mkMData d (← loop b)
+    | Expr.mdata d e     => return mkMData d (← loop e)
     | Expr.proj n i e    => return mkProj n i (← loop e)
     | Expr.app _ _ =>
       let processApp (e : Expr) : M Expr := do

src/Lean/Elab/PreDefinition/Structural/Main.lean

@@ -83,22 +83,19 @@ def structuralRecursion (preDefs : Array PreDefinition) : TermElabM Unit :=
   else do
     let ((recArgPos, preDefNonRec), state) ← run <| elimRecursion preDefs[0]!
     let preDefNonRec ← eraseRecAppSyntax preDefNonRec
-    let mut preDef ← eraseRecAppSyntax preDefs[0]!
+    let preDef ← eraseRecAppSyntax preDefs[0]!
     state.addMatchers.forM liftM
-    mapError (addNonRec preDefNonRec (applyAttrAfterCompilation := false)) fun msg =>
-      m!"structural recursion failed, produced type incorrect term{indentD msg}"
-    -- We create the `_unsafe_rec` before we abstract nested proofs.
-    -- Reason: the nested proofs may be referring to the _unsafe_rec.
-    addAndCompilePartialRec #[preDef]
     unless preDef.kind.isTheorem do
       unless (← isProp preDef.type) do
-        preDef ← abstractNestedProofs preDef
         /-
         Don't save predefinition info for equation generator
         for theorems and definitions that are propositions.
         See issue #2327
         -/
         registerEqnsInfo preDef recArgPos
+    mapError (addNonRec preDefNonRec (applyAttrAfterCompilation := false)) fun msg =>
+      m!"structural recursion failed, produced type incorrect term{indentD msg}"
+    addAndCompilePartialRec #[preDef]
     addSmartUnfoldingDef preDef recArgPos
     applyAttributesOf #[preDefNonRec] AttributeApplicationTime.afterCompilation
 

src/Lean/Elab/PreDefinition/Structural/Preprocess.lean

@@ -4,7 +4,6 @@ Released under Apache 2.0 license as described in the file LICENSE.
 Authors: Leonardo de Moura
 -/
 import Lean.Meta.Transform
-import Lean.Elab.RecAppSyntax
 
 namespace Lean.Elab.Structural
 open Meta
@@ -16,39 +15,21 @@ private def shouldBetaReduce (e : Expr) (recFnName : Name) : Bool :=
     false
 
 /--
-Preprocesses the expessions to improve the effectiveness of `elimRecursion`.
-
-* Beta reduce terms where the recursive function occurs in the lambda term.
+  Beta reduce terms where the recursive function occurs in the lambda term.
+  This is useful to improve the effectiveness of `elimRecursion`.
   Example:
   ```
   def f : Nat → Nat
     | 0 => 1
     | i+1 => (fun x => f x) i
   ```
-
-* Floats out the RecApp markers.
-  Example:
-  ```
-  def f : Nat → Nat
-    | 0 => 1
-    | i+1 => (f x) i
-  ```
 -/
 def preprocess (e : Expr) (recFnName : Name) : CoreM Expr :=
   Core.transform e
-    (pre := fun e =>
-      if shouldBetaReduce e recFnName then
-        return .visit e.headBeta
-      else
-        return .continue)
-    (post := fun e =>
-      match e with
-      | .app (.mdata m f) a =>
-        if m.isRecApp then
-          return .done (.mdata m (.app f a))
-        else
-          return .done e
-      | _ => return .done e)
-
+   fun e =>
+     if shouldBetaReduce e recFnName then
+       return .visit e.headBeta
+     else
+       return .continue
 
 end Lean.Elab.Structural

src/Lean/Elab/PreDefinition/WF/Fix.lean

@@ -13,25 +13,28 @@ import Lean.Elab.RecAppSyntax
 import Lean.Elab.PreDefinition.Basic
 import Lean.Elab.PreDefinition.Structural.Basic
 import Lean.Elab.PreDefinition.Structural.BRecOn
-import Lean.Data.Array
 
 namespace Lean.Elab.WF
 open Meta
 
-/-
-Creates a subgoal for a recursive call, as an unsolved `MVar`. The goal is cleaned up, and
-the current syntax reference is stored in the `MVar`’s type as a `RecApp` marker, for
-use by `solveDecreasingGoals` below.
--/
-private def mkDecreasingProof (decreasingProp : Expr) : TermElabM Expr := do
-  -- We store the current Ref in the MVar as a RecApp annotation around the type
-  let ref ← getRef
-  let mvar ← mkFreshExprSyntheticOpaqueMVar (mkRecAppWithSyntax decreasingProp ref)
-  let mvarId := mvar.mvarId!
-  let _mvarId ← mvarId.cleanup
-  return mvar
+private def applyDefaultDecrTactic (mvarId : MVarId) : TermElabM Unit := do
+  let remainingGoals ← Tactic.run mvarId do
+    Tactic.evalTactic (← `(tactic| decreasing_tactic))
+  remainingGoals.forM fun mvarId => Term.reportUnsolvedGoals [mvarId]
 
-private partial def replaceRecApps (recFnName : Name) (fixedPrefixSize : Nat) (F : Expr) (e : Expr) : TermElabM Expr := do
+private def mkDecreasingProof (decreasingProp : Expr) (decrTactic? : Option Syntax) : TermElabM Expr := do
+  let mvar ← mkFreshExprSyntheticOpaqueMVar decreasingProp
+  let mvarId := mvar.mvarId!
+  let mvarId ← mvarId.cleanup
+  match decrTactic? with
+  | none => applyDefaultDecrTactic mvarId
+  | some decrTactic =>
+    -- make info from `runTactic` available
+    pushInfoTree (.hole mvarId)
+    Term.runTactic mvarId decrTactic
+  instantiateMVars mvar
+
+private partial def replaceRecApps (recFnName : Name) (fixedPrefixSize : Nat) (decrTactic? : Option Syntax) (F : Expr) (e : Expr) : TermElabM Expr := do
   trace[Elab.definition.wf] "replaceRecApps:{indentExpr e}"
   trace[Elab.definition.wf] "{F} : {← inferType F}"
   loop F e |>.run' {}
@@ -43,7 +46,7 @@ where
       let args := e.getAppArgs
       let r := mkApp F (← loop F args[fixedPrefixSize]!)
       let decreasingProp := (← whnf (← inferType r)).bindingDomain!
-      let r := mkApp r (← mkDecreasingProof decreasingProp)
+      let r := mkApp r (← mkDecreasingProof decreasingProp decrTactic?)
       return mkAppN r (← args[fixedPrefixSize+1:].toArray.mapM (loop F))
 
   processApp (F : Expr) (e : Expr) : StateRefT (HasConstCache recFnName) TermElabM Expr := do
@@ -160,47 +163,6 @@ private partial def processPSigmaCasesOn (x F val : Expr) (k : (F : Expr) → (v
   else
     k F val
 
-private def applyDefaultDecrTactic (mvarId : MVarId) : TermElabM Unit := do
-  let remainingGoals ← Tactic.run mvarId do
-    Tactic.evalTactic (← `(tactic| decreasing_tactic))
-  unless remainingGoals.isEmpty do
-    Term.reportUnsolvedGoals remainingGoals
-
-/-
-Given an array of MVars, assign MVars with equal type and subsumed local context to each other.
-Returns those MVar that did not get assigned.
--/
-def assignSubsumed (mvars : Array MVarId) : MetaM (Array MVarId) :=
-  mvars.filterPairsM fun mv₁ mv₂ => do
-    let mvdecl₁ ← mv₁.getDecl
-    let mvdecl₂ ← mv₂.getDecl
-    if mvdecl₁.type == mvdecl₂.type then
-      -- same goals; check contexts.
-        if mvdecl₁.lctx.isSubPrefixOf mvdecl₂.lctx then
-          -- mv₁ is better
-          mv₂.assign (.mvar mv₁)
-          return (true, false)
-        if mvdecl₂.lctx.isSubPrefixOf mvdecl₁.lctx then
-          -- mv₂ is better
-          mv₁.assign (.mvar mv₂)
-          return (false, true)
-    return (true, true)
-
-def solveDecreasingGoals (decrTactic? : Option Syntax) (value : Expr) : MetaM Expr := do
-  let goals ← getMVarsNoDelayed value
-  let goals ← assignSubsumed goals
-  goals.forM fun goal => Lean.Elab.Term.TermElabM.run' <|
-    match decrTactic? with
-    | none => do
-      let some ref := getRecAppSyntax? (← goal.getType)
-        | throwError "MVar does not look like like a recursive call"
-        withRef ref <| applyDefaultDecrTactic goal
-    | some decrTactic => do
-      -- make info from `runTactic` available
-      pushInfoTree (.hole goal)
-      Term.runTactic goal decrTactic
-  instantiateMVars value
-
 def mkFix (preDef : PreDefinition) (prefixArgs : Array Expr) (wfRel : Expr) (decrTactic? : Option Syntax) : TermElabM Expr := do
   let type ← instantiateForall preDef.type prefixArgs
   let (wfFix, varName) ← forallBoundedTelescope type (some 1) fun x type => do
@@ -223,8 +185,7 @@ def mkFix (preDef : PreDefinition) (prefixArgs : Array Expr) (wfRel : Expr) (dec
       let F   := xs[1]!
       let val := preDef.value.beta (prefixArgs.push x)
       let val ← processSumCasesOn x F val fun x F val => do
-        processPSigmaCasesOn x F val (replaceRecApps preDef.declName prefixArgs.size)
-      let val ← solveDecreasingGoals decrTactic? val
+        processPSigmaCasesOn x F val (replaceRecApps preDef.declName prefixArgs.size decrTactic?)
       mkLambdaFVars prefixArgs (mkApp wfFix (← mkLambdaFVars #[x, F] val))
 
 end Lean.Elab.WF

src/Lean/Elab/PreDefinition/WF/GuessLex.lean

@@ -1,744 +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 Lean.Util.HasConstCache
-import Lean.Meta.CasesOn
-import Lean.Meta.Match.Match
-import Lean.Meta.Tactic.Cleanup
-import Lean.Meta.Tactic.Refl
-import Lean.Elab.Quotation
-import Lean.Elab.RecAppSyntax
-import Lean.Elab.PreDefinition.Basic
-import Lean.Elab.PreDefinition.Structural.Basic
-import Lean.Elab.PreDefinition.WF.TerminationHint
-import Lean.Data.Array
-
-
-/-!
-This module finds lexicographic termination arguments for well-founded recursion.
-
-Starting with basic measures (`sizeOf xᵢ` for all parameters `xᵢ`), it tries all combinations
-until it finds one where all proof obligations go through with the given tactic (`decerasing_by`),
-if given, or the default `decreasing_tactic`.
-
-For mutual recursion, a single measure is not just one parameter, but one from each recursive
-function. Enumerating these can lead to a combinatoric explosion, so we bound
-the nubmer of measures tried.
-
-In addition to measures derived from `sizeOf xᵢ`, it also considers measures
-that assign an order to the functions themselves. This way we can support mutual
-function definitions where no arguments decrease from one function to another.
-
-
-The result of this module is a `TerminationWF`, which is then passed on to `wfRecursion`; this
-design is crucial so that whatever we infer in this module could also be written manually by the
-user. It would be bad if there are function definitions that can only be processed with the
-guessed lexicographic order.
-
-The following optimizations are applied to make this feasible:
-
-1. The crucial optimiziation is to look at each argument of each recursive call
-   _once_, try to prove `<` and (if that fails `≤`), and then look at that table to
-   pick a suitable measure.
-
-2. The next-crucial optimization is to fill that table lazily.  This way, we run the (likely
-   expensive) tactics as few times as possible, while still being able to consider a possibly
-   large number of combinations.
-
-3. Before we even try to prove `<`, we check if the arguments are equal (`=`). No well-founded
-   measure will relate equal terms, likely this check is faster than firing up the tactic engine,
-   and it adds more signal to the output.
-
-4. Instead of traversing the whole function body over and over, we traverse it once and store
-   the arguments (in unpacked form) and the local `MetaM` state at each recursive call
-   (see `collectRecCalls`), which we then re-use for the possibly many proof attempts.
-
-The logic here is based on “Finding Lexicographic Orders for Termination Proofs in Isabelle/HOL”
-by Lukas Bulwahn, Alexander Krauss, and Tobias Nipkow, 10.1007/978-3-540-74591-4_5
-<https://www21.in.tum.de/~nipkow/pubs/tphols07.pdf>.
--/
-
-set_option autoImplicit false
-
-open Lean Meta Elab
-
-namespace Lean.Elab.WF.GuessLex
-
-register_builtin_option showInferredTerminationBy : Bool := {
-  defValue := false
-  descr    := "In recursive definitions, show the inferred `termination_by` measure."
-}
-
-/--
-Given a predefinition, find good variable names for its parameters.
-Use user-given parameter names if present; use x1...xn otherwise.
-
-The length of the returned array is also used to determine the arity
-of the function, so it should match what `packDomain` does.
-
-The names ought to accessible (no macro scopes) and still fresh wrt to the current environment,
-so that with `showInferredTerminationBy` we can print them to the user reliably.
-We do that by appending `'` as needed.
--/
-partial
-def naryVarNames (fixedPrefixSize : Nat) (preDef : PreDefinition) : MetaM (Array Name):= do
-  lambdaTelescope preDef.value fun xs _ => do
-    let xs := xs.extract fixedPrefixSize xs.size
-    let mut ns : Array Name := #[]
-    for h : i in [:xs.size] do
-      let n ← (xs[i]'h.2).fvarId!.getUserName
-      let n := if n.hasMacroScopes then .mkSimple s!"x{i+1}" else n
-      ns := ns.push (← freshen ns n)
-    return ns
-  where
-    freshen  (ns : Array Name) (n : Name): MetaM Name := do
-      if !(ns.elem n) && (← resolveGlobalName n).isEmpty then
-        return n
-      else
-        freshen ns (n.appendAfter "'")
-
-
-/-- Internal monad used by `withRecApps` -/
-abbrev M (recFnName : Name) (α β : Type) : Type :=
-  StateRefT (Array α) (StateRefT (HasConstCache recFnName) MetaM) β
-
-/--
-Traverses the given expression `e`, and invokes the continuation `k`
-at every saturated call to `recFnName`.
-
-The expression `param` is passed along, and refined when going under a matcher
-or `casesOn` application.
--/
-partial def withRecApps {α} (recFnName : Name) (fixedPrefixSize : Nat) (param : Expr) (e : Expr)
-    (k : Expr → Array Expr → MetaM α) : MetaM (Array α) := do
-  trace[Elab.definition.wf] "withRecApps: {indentExpr e}"
-  let (_, as) ← loop param e |>.run #[] |>.run' {}
-  return as
-where
-  processRec (param : Expr) (e : Expr) : M recFnName α Unit := do
-    if e.getAppNumArgs < fixedPrefixSize + 1 then
-      loop param (← etaExpand e)
-    else
-      let a ← k param e.getAppArgs
-      modifyThe (Array α) (·.push a)
-
-  processApp (param : Expr) (e : Expr) : M recFnName α Unit := do
-    e.withApp fun f args => do
-      args.forM (loop param)
-      if f.isConstOf recFnName then
-        processRec param e
-      else
-        loop param f
-
-  containsRecFn (e : Expr) : M recFnName α Bool := do
-    modifyGetThe (HasConstCache recFnName) (·.contains e)
-
-  loop (param : Expr) (e : Expr) : M recFnName α Unit := do
-    if !(← containsRecFn e) then
-      return
-    match e with
-    | Expr.lam n d b c =>
-      loop param d
-      withLocalDecl n c d fun x => do
-        loop param (b.instantiate1 x)
-    | Expr.forallE n d b c =>
-      loop param d
-      withLocalDecl n c d fun x => do
-        loop param (b.instantiate1 x)
-    | Expr.letE n type val body _ =>
-      loop param type
-      loop param val
-      withLetDecl n type val fun x => do
-        loop param (body.instantiate1 x)
-    | Expr.mdata _d b =>
-      if let some stx := getRecAppSyntax? e then
-        withRef stx <| loop param b
-      else
-        loop param b
-    | Expr.proj _n _i e => loop param e
-    | Expr.const .. => if e.isConstOf recFnName then processRec param e
-    | Expr.app .. =>
-      match (← matchMatcherApp? e) with
-      | some matcherApp =>
-        if !Structural.recArgHasLooseBVarsAt recFnName fixedPrefixSize e then
-          processApp param e
-        else
-          if let some altParams ← matcherApp.refineThrough? param then
-            (Array.zip matcherApp.alts (Array.zip matcherApp.altNumParams altParams)).forM
-              fun (alt, altNumParam, altParam) =>
-                lambdaTelescope altParam fun xs altParam => do
-                  -- TODO: Use boundedLambdaTelescope
-                  unless altNumParam = xs.size do
-                    throwError "unexpected `casesOn` application alternative{indentExpr alt}\nat application{indentExpr e}"
-                  let altBody := alt.beta xs
-                  loop altParam altBody
-          else
-            processApp param e
-      | none =>
-      match (← toCasesOnApp? e) with
-      | some casesOnApp =>
-        if !Structural.recArgHasLooseBVarsAt recFnName fixedPrefixSize e then
-          processApp param e
-        else
-          if let some altParams ← casesOnApp.refineThrough? param then
-          (Array.zip casesOnApp.alts (Array.zip casesOnApp.altNumParams altParams)).forM
-            fun (alt, altNumParam, altParam) =>
-              lambdaTelescope altParam fun xs altParam => do
-                -- TODO: Use boundedLambdaTelescope
-                unless altNumParam = xs.size do
-                  throwError "unexpected `casesOn` application alternative{indentExpr alt}\nat application{indentExpr e}"
-                let altBody := alt.beta xs
-                loop altParam altBody
-          else
-            processApp param e
-      | none => processApp param e
-    | e => do
-      let _ ← ensureNoRecFn recFnName e
-
-/--
-A `SavedLocalContext` captures the state and local context of a `MetaM`, to be continued later.
--/
-structure SavedLocalContext where
-  savedLocalContext : LocalContext
-  savedLocalInstances : LocalInstances
-  savedState : Meta.SavedState
-
-/-- Capture the `MetaM` state including local context. -/
-def SavedLocalContext.create : MetaM SavedLocalContext := do
-  let savedLocalContext ← getLCtx
-  let savedLocalInstances ← getLocalInstances
-  let savedState ← saveState
-  return { savedLocalContext, savedLocalInstances, savedState }
-
-/-- Run a `MetaM` action in the saved state. -/
-def SavedLocalContext.run {α} (slc : SavedLocalContext) (k : MetaM α) :
-    MetaM α :=
-  withoutModifyingState $ do
-    withLCtx slc.savedLocalContext slc.savedLocalInstances do
-      slc.savedState.restore
-      k
-
-/-- A `RecCallWithContext` focuses on a single recursive call in a unary predefinition,
-and runs the given action in the context of that call.  -/
-structure RecCallWithContext where
-  /-- Syntax location of reursive call -/
-  ref : Syntax
-  /-- Function index of caller -/
-  caller : Nat
-  /-- Parameters of caller -/
-  params : Array Expr
-  /-- Function index of callee -/
-  callee : Nat
-  /-- Arguments to callee -/
-  args : Array Expr
-  ctxt : SavedLocalContext
-
-/-- Store the current recursive call and its context. -/
-def RecCallWithContext.create (ref : Syntax) (caller : Nat) (params : Array Expr) (callee : Nat)
-    (args : Array Expr) : MetaM RecCallWithContext := do
-  return { ref, caller, params, callee, args, ctxt := (← SavedLocalContext.create) }
-
-
-/--
-The elaborator is prone to duplicate terms, including recursive calls, even if the user
-only wrote a single one. This duplication is wasteful if we run the tactics on duplicated
-calls, and confusing in the output of GuessLex. So prune the list of recursive calls,
-and remove those where another call exists that has the same goal and context that is no more
-specific.
--/
-def filterSubsumed (rcs : Array RecCallWithContext ) : Array RecCallWithContext := Id.run do
-  rcs.filterPairsM fun rci rcj => do
-    if rci.caller == rcj.caller && rci.callee == rcj.callee &&
-      rci.params == rcj.params && rci.args == rcj.args then
-      -- same goals; check contexts.
-        let lci := rci.ctxt.savedLocalContext
-        let lcj := rcj.ctxt.savedLocalContext
-        if lci.isSubPrefixOf lcj then
-          -- rci is better
-          return (true, false)
-        else if lcj.isSubPrefixOf lci then
-          -- rcj is better
-          return (false, true)
-    return (true, true)
-
-/-- Given the packed argument of a (possibly) mutual and (possibly) nary call,
-return the function index that is called and the arguments individually.
-
-We expect precisely the expressions produced by `packMutual`, with manifest
-`PSum.inr`, `PSum.inl` and `PSigma.mk` constructors, and thus take them apart
-rather than using projectinos. -/
-def unpackArg {m} [Monad m] [MonadError m] (arities : Array Nat) (e : Expr) :
-    m (Nat × Array Expr) := do
-  -- count PSum injections to find out which function is doing the call
-  let mut funidx := 0
-  let mut e := e
-  while funidx + 1 < arities.size do
-    if e.isAppOfArity ``PSum.inr 3 then
-      e := e.getArg! 2
-      funidx := funidx + 1
-    else if e.isAppOfArity ``PSum.inl 3 then
-      e := e.getArg! 2
-      break
-    else
-      throwError "Unexpected expression while unpacking mutual argument"
-
-  -- now unpack PSigmas
-  let arity := arities[funidx]!
-  let mut args := #[]
-  while args.size + 1 < arity do
-    if e.isAppOfArity ``PSigma.mk 4 then
-      args := args.push (e.getArg! 2)
-      e := e.getArg! 3
-    else
-      throwError "Unexpected expression while unpacking n-ary argument"
-  args := args.push e
-  return (funidx, args)
-
-/-- Traverse a unary PreDefinition, and returns a `WithRecCall` closure for each recursive
-call site.
--/
-def collectRecCalls (unaryPreDef : PreDefinition) (fixedPrefixSize : Nat) (arities : Array Nat)
-    : MetaM (Array RecCallWithContext) := withoutModifyingState do
-  addAsAxiom unaryPreDef
-  lambdaTelescope unaryPreDef.value fun xs body => do
-    unless xs.size == fixedPrefixSize + 1 do
-      -- Maybe cleaner to have lambdaBoundedTelescope?
-      throwError "Unexpected number of lambdas in unary pre-definition"
-    -- trace[Elab.definition.wf] "collectRecCalls: {xs} {body}"
-    let param := xs[fixedPrefixSize]!
-    withRecApps unaryPreDef.declName fixedPrefixSize param body fun param args => do
-      unless args.size ≥ fixedPrefixSize + 1 do
-        throwError "Insufficient arguments in recursive call"
-      let arg := args[fixedPrefixSize]!
-      let (caller, params) ← unpackArg arities param
-      let (callee, args) ← unpackArg arities arg
-      RecCallWithContext.create (← getRef) caller params callee args
-
-/-- A `GuessLexRel` described how a recursive call affects a measure; whether it
-decreases strictly, non-strictly, is equal, or else.  -/
-inductive GuessLexRel | lt | eq | le | no_idea
-deriving Repr, DecidableEq
-
-instance : ToString GuessLexRel where
-  toString | .lt => "<"
-           | .eq => "="
-           | .le => "≤"
-           | .no_idea => "?"
-
-instance : ToFormat GuessLexRel where
-  format r := toString r
-
-/-- Given a `GuessLexRel`, produce a binary `Expr` that relates two `Nat` values accordingly. -/
-def GuessLexRel.toNatRel : GuessLexRel → Expr
-  | lt => mkAppN (mkConst ``LT.lt [levelZero]) #[mkConst ``Nat, mkConst ``instLTNat]
-  | eq => mkAppN (mkConst ``Eq [levelOne]) #[mkConst ``Nat]
-  | le => mkAppN (mkConst ``LE.le [levelZero]) #[mkConst ``Nat, mkConst ``instLENat]
-  | no_idea => unreachable!
-
-/-- Given an expression `e`, produce `sizeOf e` with a suitable instance. -/
-def mkSizeOf (e : Expr) : MetaM Expr := do
-  let ty ← inferType e
-  let lvl ← getLevel ty
-  let inst ← synthInstance (mkAppN (mkConst ``SizeOf [lvl]) #[ty])
-  let res := mkAppN (mkConst ``sizeOf [lvl]) #[ty,  inst, e]
-  check res
-  return res
-
-/--
-For a given recursive call, and a choice of parameter and argument index,
-try to prove equality, < or ≤.
--/
-def evalRecCall (decrTactic? : Option Syntax) (rcc : RecCallWithContext) (paramIdx argIdx : Nat) :
-    MetaM GuessLexRel := do
-  rcc.ctxt.run do
-    let param := rcc.params[paramIdx]!
-    let arg := rcc.args[argIdx]!
-    trace[Elab.definition.wf] "inspectRecCall: {rcc.caller} ({param}) → {rcc.callee} ({arg})"
-    let arg ← mkSizeOf rcc.args[argIdx]!
-    let param ← mkSizeOf rcc.params[paramIdx]!
-    for rel in [GuessLexRel.eq, .lt, .le] do
-      let goalExpr := mkAppN rel.toNatRel #[arg, param]
-      trace[Elab.definition.wf] "Goal for {rel}: {goalExpr}"
-      check goalExpr
-
-      let mvar ← mkFreshExprSyntheticOpaqueMVar goalExpr
-      let mvarId := mvar.mvarId!
-      let mvarId ← mvarId.cleanup
-      -- logInfo m!"Remaining goals: {goalsToMessageData [mvarId]}"
-      try
-        if rel = .eq then
-          MVarId.refl mvarId
-        else do
-          Lean.Elab.Term.TermElabM.run' do
-            match decrTactic? with
-            | none =>
-              let remainingGoals ← Tactic.run mvarId do
-                Tactic.evalTactic (← `(tactic| decreasing_tactic))
-              remainingGoals.forM fun mvarId => Term.reportUnsolvedGoals [mvarId]
-              -- trace[Elab.definition.wf] "Found {rel} proof: {← instantiateMVars mvar}"
-              pure ()
-            | some decrTactic => Term.withoutErrToSorry do
-              -- make info from `runTactic` available
-              pushInfoTree (.hole mvarId)
-              Term.runTactic mvarId decrTactic
-              -- trace[Elab.definition.wf] "Found {rel} proof: {← instantiateMVars mvar}"
-              pure ()
-        trace[Elab.definition.wf] "inspectRecCall: success!"
-        return rel
-      catch _e =>
-        trace[Elab.definition.wf] "Did not find {rel} proof: {goalsToMessageData [mvarId]}"
-        continue
-    return .no_idea
-
-/- A cache for `evalRecCall` -/
-structure RecCallCache where mk'' ::
-  decrTactic? : Option Syntax
-  rcc : RecCallWithContext
-  cache : IO.Ref (Array (Array (Option GuessLexRel)))
-
-/-- Create a cache to memoize calls to `evalRecCall descTactic? rcc` -/
-def RecCallCache.mk (decrTactic? : Option Syntax) (rcc : RecCallWithContext) :
-    BaseIO RecCallCache := do
-  let cache ← IO.mkRef <| Array.mkArray rcc.params.size (Array.mkArray rcc.args.size Option.none)
-  return { decrTactic?, rcc, cache }
-
-/-- Run `evalRecCall` and cache there result -/
-def RecCallCache.eval (rc: RecCallCache) (paramIdx argIdx : Nat) : MetaM GuessLexRel := do
-  -- Check the cache first
-  if let Option.some res := (← rc.cache.get)[paramIdx]![argIdx]! then
-    return res
-  else
-    let res ← evalRecCall rc.decrTactic? rc.rcc paramIdx argIdx
-    rc.cache.modify (·.modify paramIdx (·.set! argIdx res))
-    return res
-
-
-/-- Print a single cache entry as a string, without forcing it -/
-def RecCallCache.prettyEntry (rcc : RecCallCache) (paramIdx argIdx : Nat) : MetaM String := do
-  let cachedEntries ← rcc.cache.get
-  return match cachedEntries[paramIdx]![argIdx]! with
-  | .some rel => toString rel
-  | .none => "_"
-
-/-- The measures that we order lexicographically can be comparing arguments,
-or numbering the functions -/
-inductive MutualMeasure where
-  /-- For every function, the given argument index -/
-  | args : Array Nat → MutualMeasure
-  /-- The given function index is assigned 1, the rest 0 -/
-  | func : Nat → MutualMeasure
-
-/-- Evaluate a recursive call at a given `MutualMeasure` -/
-def inspectCall (rc : RecCallCache) : MutualMeasure → MetaM GuessLexRel
-  | .args argIdxs => do
-    let paramIdx := argIdxs[rc.rcc.caller]!
-    let argIdx := argIdxs[rc.rcc.callee]!
-    rc.eval paramIdx argIdx
-  | .func funIdx => do
-    if rc.rcc.caller == funIdx && rc.rcc.callee != funIdx then
-      return .lt
-    if rc.rcc.caller != funIdx && rc.rcc.callee == funIdx then
-      return .no_idea
-    else
-      return .eq
-
-/--
-Given a predefinition with value `fun (x_₁ ... xₙ) (y_₁ : α₁)... (yₘ : αₘ) => ...`,
-where `n = fixedPrefixSize`, return an array `A` s.t. `i ∈ A` iff `sizeOf yᵢ` reduces to a literal.
-This is the case for types such as `Prop`, `Type u`, etc.
-These arguments should not be considered when guessing a well-founded relation.
-See `generateCombinations?`
--/
-def getForbiddenByTrivialSizeOf (fixedPrefixSize : Nat) (preDef : PreDefinition) : MetaM (Array Nat) :=
-  lambdaTelescope preDef.value fun xs _ => do
-    let mut result := #[]
-    for x in xs[fixedPrefixSize:], i in [:xs.size] do
-      try
-        let sizeOf ← whnfD (← mkAppM ``sizeOf #[x])
-        if sizeOf.isLit then
-         result := result.push i
-      catch _ =>
-        result := result.push i
-    return result
-
-
-/--
-Generate all combination of arguments, skipping those that are forbidden.
-
-Sorts the uniform combinations ([0,0,0], [1,1,1]) to the front; they are commonly most useful to
-try first, when the mutually recursive functions have similar argument structures
--/
-partial def generateCombinations? (forbiddenArgs : Array (Array Nat)) (numArgs : Array Nat)
-    (threshold : Nat := 32) : Option (Array (Array Nat)) :=
-  (do goUniform 0; go 0 #[]) |>.run #[] |>.2
-where
-  isForbidden (fidx : Nat) (argIdx : Nat) : Bool :=
-    if h : fidx < forbiddenArgs.size then
-       forbiddenArgs[fidx] |>.contains argIdx
-    else
-      false
-
-  -- Enumerate all permissible uniform combinations
-  goUniform (argIdx : Nat) : OptionT (StateM (Array (Array Nat))) Unit  := do
-    if numArgs.all (argIdx < ·) then
-      unless forbiddenArgs.any (·.contains argIdx) do
-        modify (·.push (Array.mkArray numArgs.size argIdx))
-      goUniform (argIdx + 1)
-
-  -- Enumerate all other permissible combinations
-  go (fidx : Nat) : OptionT (ReaderT (Array Nat) (StateM (Array (Array Nat)))) Unit := do
-    if h : fidx < numArgs.size then
-      let n := numArgs[fidx]
-      for argIdx in [:n] do
-        unless isForbidden fidx argIdx do
-          withReader (·.push argIdx) (go (fidx + 1))
-    else
-      let comb ← read
-      unless comb.all (· == comb[0]!) do
-        modify (·.push comb)
-      if (← get).size > threshold then
-        failure
-
-
-/--
-Enumerate all meausures we want to try: All arguments (resp. combinations thereof) and
-possible orderings of functions (if more than one)
--/
-def generateMeasures (forbiddenArgs : Array (Array Nat)) (arities : Array Nat) :
-    MetaM (Array MutualMeasure) := do
-  let some arg_measures := generateCombinations? forbiddenArgs arities
-      | throwError "Too many combinations"
-
-  let func_measures :=
-    if arities.size > 1 then
-      (List.range arities.size).toArray
-    else
-      #[]
-
-  return arg_measures.map .args ++ func_measures.map .func
-
-/--
-The core logic of guessing the lexicographic order
-Given a matrix that for each call and measure indicates whether that measure is
-decreasing, equal, less-or-equal or unknown, It finds a sequence of measures
-that is lexicographically decreasing.
-
-The matrix is implemented here as an array of monadic query methods only so that
-we can fill is lazily. Morally, this is a pure function
--/
-partial def solve {m} {α} [Monad m] (measures : Array α)
-  (calls : Array (α → m GuessLexRel)) : m (Option (Array α)) := do
-  go measures calls #[]
-  where
-  go (measures : Array α) (calls : Array (α → m GuessLexRel)) (acc : Array α) := do
-    if calls.isEmpty then return .some acc
-
-    -- Find the first measure that has at least one < and otherwise only = or <=
-    for h : measureIdx in [:measures.size] do
-      let measure := measures[measureIdx]'h.2
-      let mut has_lt := false
-      let mut all_le := true
-      let mut todo := #[]
-      for call in calls do
-        let entry ← call measure
-        if entry = .lt then
-          has_lt := true
-        else
-          todo := todo.push call
-          if entry != .le && entry != .eq then
-            all_le := false
-            break
-      -- No progress here? Try the next measure
-      if not (has_lt && all_le) then continue
-      -- We found a suitable measure, remove it from the list (mild optimization)
-      let measures' := measures.eraseIdx measureIdx
-      return ← go measures' todo (acc.push measure)
-    -- None found, we have to give up
-    return .none
-
-/--
-Create Tuple syntax (`()` if the array is empty, and just the value if its a singleton)
--/
-def mkTupleSyntax : Array Term → MetaM Term
-  | #[]  => `(())
-  | #[e] => return e
-  | es   => `(($(es[0]!), $(es[1:]),*))
-
-/--
-Given an array of `MutualMeasures`, creates a `TerminationWF` that specifies the lexicographic
-combination of these measures.
--/
-def buildTermWF (declNames : Array Name) (varNamess : Array (Array Name))
-    (measures : Array MutualMeasure) : MetaM TerminationWF := do
-  let mut termByElements := #[]
-  for h : funIdx in [:varNamess.size] do
-    let vars := (varNamess[funIdx]'h.2).map mkIdent
-    let body ← mkTupleSyntax (← measures.mapM fun
-      | .args varIdxs => do
-          let v := vars.get! (varIdxs[funIdx]!)
-          let sizeOfIdent := mkIdent (← unresolveNameGlobal ``sizeOf)
-          `($sizeOfIdent $v)
-      | .func funIdx' => if funIdx' == funIdx then `(1) else `(0)
-      )
-    let declName := declNames[funIdx]!
-
-    termByElements := termByElements.push
-      { ref := .missing
-        declName, vars, body,
-        implicit := true
-      }
-  return .ext termByElements
-
-
-/--
-Given a matrix (row-major) of strings, arranges them in tabular form.
-First column is left-aligned, others right-aligned.
-Single space as column separator.
--/
-def formatTable : Array (Array String) → String := fun xss => Id.run do
-  let mut colWidths := xss[0]!.map (fun _ => 0)
-  for i in [:xss.size] do
-    for j in [:xss[i]!.size] do
-      if xss[i]![j]!.length > colWidths[j]! then
-        colWidths := colWidths.set! j xss[i]![j]!.length
-  let mut str := ""
-  for i in [:xss.size] do
-    for j in [:xss[i]!.size] do
-      let s := xss[i]![j]!
-      if j > 0 then -- right-align
-        for _ in [:colWidths[j]! - s.length] do
-          str := str ++ " "
-      str := str ++ s
-      if j = 0 then -- left-align
-        for _ in [:colWidths[j]! - s.length] do
-          str := str ++ " "
-      if j + 1 < xss[i]!.size then
-        str := str ++ " "
-    if i + 1 < xss.size then
-      str := str ++ "\n"
-  return str
-
-/-- Concise textual representation of the source location of a recursive call  -/
-def RecCallWithContext.posString (rcc : RecCallWithContext) : MetaM String := do
-  let fileMap ← getFileMap
-  let .some pos := rcc.ref.getPos? | return ""
-  let position := fileMap.toPosition pos
-  let endPosStr := match rcc.ref.getTailPos? with
-  | some endPos =>
-    let endPosition := fileMap.toPosition endPos
-    if endPosition.line = position.line then
-      s!"-{endPosition.column}"
-    else
-      s!"-{endPosition.line}:{endPosition.column}"
-  | none        => ""
-  return s!"{position.line}:{position.column}{endPosStr}"
-
-
-/-- Explain what we found out about the recursive calls (non-mutual case) -/
-def explainNonMutualFailure (varNames : Array Name) (rcs : Array RecCallCache) : MetaM Format := do
-  let header := varNames.map (·.eraseMacroScopes.toString)
-  let mut table : Array (Array String) := #[#[""] ++ header]
-  for i in [:rcs.size], rc in rcs do
-    let mut row := #[s!"{i+1}) {← rc.rcc.posString}"]
-    for argIdx in [:varNames.size] do
-      row := row.push (← rc.prettyEntry argIdx argIdx)
-    table := table.push row
-
-  return formatTable table
-
-/-- Explain what we found out about the recursive calls (mutual case) -/
-def explainMutualFailure (declNames : Array Name) (varNamess : Array (Array Name))
-    (rcs : Array RecCallCache) : MetaM Format := do
-  let mut r := Format.nil
-
-  for rc in rcs do
-    let caller := rc.rcc.caller
-    let callee := rc.rcc.callee
-    r := r ++ f!"Call from {declNames[caller]!} to {declNames[callee]!} " ++
-      f!"at {← rc.rcc.posString}:\n"
-
-    let header := varNamess[caller]!.map (·.eraseMacroScopes.toString)
-    let mut table : Array (Array String) := #[#[""] ++ header]
-    if caller = callee then
-      -- For self-calls, only the diagonal is interesting, so put it into one row
-      let mut row := #[""]
-      for argIdx in [:varNamess[caller]!.size] do
-        row := row.push (← rc.prettyEntry argIdx argIdx)
-      table := table.push row
-    else
-      for argIdx in [:varNamess[callee]!.size] do
-        let mut row := #[]
-        row := row.push varNamess[callee]![argIdx]!.eraseMacroScopes.toString
-        for paramIdx in [:varNamess[caller]!.size] do
-          row := row.push (← rc.prettyEntry paramIdx argIdx)
-        table := table.push row
-    r := r ++ formatTable table ++ "\n"
-
-  return r
-
-def explainFailure (declNames : Array Name) (varNamess : Array (Array Name))
-    (rcs : Array RecCallCache) : MetaM Format := do
-  let mut r : Format := "The arguments relate at each recursive call as follows:\n" ++
-    "(<, ≤, =: relation proved, ? all proofs failed, _: no proof attempted)\n"
-  if declNames.size = 1 then
-    r := r ++ (← explainNonMutualFailure varNamess[0]! rcs)
-  else
-    r := r ++ (← explainMutualFailure declNames varNamess rcs)
-  return r
-
-end Lean.Elab.WF.GuessLex
-
-namespace Lean.Elab.WF
-
-open Lean.Elab.WF.GuessLex
-
-/--
-Main entry point of this module:
-
-Try to find a lexicographic ordering of the arguments for which the recursive definition
-terminates. See the module doc string for a high-level overview.
--/
-def guessLex (preDefs : Array PreDefinition)  (unaryPreDef : PreDefinition)
-    (fixedPrefixSize : Nat) (decrTactic? : Option Syntax) :
-    MetaM TerminationWF := do
-  let varNamess ← preDefs.mapM (naryVarNames fixedPrefixSize ·)
-  let arities := varNamess.map (·.size)
-  trace[Elab.definition.wf] "varNames is: {varNamess}"
-
-  let forbiddenArgs ← preDefs.mapM fun preDef =>
-    getForbiddenByTrivialSizeOf fixedPrefixSize preDef
-
-  -- The list of measures, including the measures that order functions.
-  -- The function ordering measures come last
-  let measures ← generateMeasures forbiddenArgs arities
-
-  -- If there is only one plausible measure, use that
-  if let #[solution] := measures then
-    return ← buildTermWF (preDefs.map (·.declName)) varNamess #[solution]
-
-  -- Collect all recursive calls and extract their context
-  let recCalls ← collectRecCalls unaryPreDef fixedPrefixSize arities
-  let recCalls := filterSubsumed recCalls
-  let rcs ← recCalls.mapM (RecCallCache.mk decrTactic? ·)
-  let callMatrix := rcs.map (inspectCall ·)
-
-  match ← liftMetaM <| solve measures callMatrix with
-  | .some solution => do
-    let wf ← buildTermWF (preDefs.map (·.declName)) varNamess solution
-
-    let wfStx ← withoutModifyingState do
-      preDefs.forM (addAsAxiom ·)
-      wf.unexpand
-
-    if showInferredTerminationBy.get (← getOptions) then
-      logInfo m!"Inferred termination argument:{wfStx}"
-
-    return wf
-  | .none =>
-    let explanation ← explainFailure (preDefs.map (·.declName)) varNamess rcs
-    Lean.throwError <| "Could not find a decreasing measure.\n" ++
-      explanation ++ "\n" ++
-      "Please use `termination_by` to specify a decreasing measure."

src/Lean/Elab/PreDefinition/WF/Main.lean

@@ -7,12 +7,10 @@ import Lean.Elab.PreDefinition.Basic
 import Lean.Elab.PreDefinition.WF.TerminationHint
 import Lean.Elab.PreDefinition.WF.PackDomain
 import Lean.Elab.PreDefinition.WF.PackMutual
-import Lean.Elab.PreDefinition.WF.Preprocess
 import Lean.Elab.PreDefinition.WF.Rel
 import Lean.Elab.PreDefinition.WF.Fix
 import Lean.Elab.PreDefinition.WF.Eqns
 import Lean.Elab.PreDefinition.WF.Ite
-import Lean.Elab.PreDefinition.WF.GuessLex
 
 namespace Lean.Elab
 open WF
@@ -81,7 +79,6 @@ private def isOnlyOneUnaryDef (preDefs : Array PreDefinition) (fixedPrefixSize :
     return false
 
 def wfRecursion (preDefs : Array PreDefinition) (wf? : Option TerminationWF) (decrTactic? : Option Syntax) : TermElabM Unit := do
-  let preDefs ← preDefs.mapM fun preDef => return { preDef with value := (← preprocess preDef.value) }
   let (unaryPreDef, fixedPrefixSize) ← withoutModifyingEnv do
     for preDef in preDefs do
       addAsAxiom preDef
@@ -90,17 +87,10 @@ def wfRecursion (preDefs : Array PreDefinition) (wf? : Option TerminationWF) (de
     let preDefsDIte ← preDefs.mapM fun preDef => return { preDef with value := (← iteToDIte preDef.value) }
     let unaryPreDefs ← packDomain fixedPrefixSize preDefsDIte
     return (← packMutual fixedPrefixSize preDefs unaryPreDefs, fixedPrefixSize)
-
-  let wf ←
-    if let .some wf := wf? then
-      pure wf
-    else
-      guessLex preDefs unaryPreDef fixedPrefixSize decrTactic?
-
   let preDefNonRec ← forallBoundedTelescope unaryPreDef.type fixedPrefixSize fun prefixArgs type => do
     let type ← whnfForall type
     let packedArgType := type.bindingDomain!
-    elabWFRel preDefs unaryPreDef.declName fixedPrefixSize packedArgType wf fun wfRel => do
+    elabWFRel preDefs unaryPreDef.declName fixedPrefixSize packedArgType wf? fun wfRel => do
       trace[Elab.definition.wf] "wfRel: {wfRel}"
       let (value, envNew) ← withoutModifyingEnv' do
         addAsAxiom unaryPreDef
@@ -117,13 +107,10 @@ def wfRecursion (preDefs : Array PreDefinition) (wf? : Option TerminationWF) (de
     withEnableInfoTree false do
       addNonRec preDefNonRec (applyAttrAfterCompilation := false)
     addNonRecPreDefs preDefs preDefNonRec fixedPrefixSize
-  -- We create the `_unsafe_rec` before we abstract nested proofs.
-  -- Reason: the nested proofs may be referring to the _unsafe_rec.
-  addAndCompilePartialRec preDefs
-  let preDefs ← preDefs.mapM (abstractNestedProofs ·)
   registerEqnsInfo preDefs preDefNonRec.declName fixedPrefixSize
   for preDef in preDefs do
     applyAttributesOf #[preDef] AttributeApplicationTime.afterCompilation
+  addAndCompilePartialRec preDefs
 
 builtin_initialize registerTraceClass `Elab.definition.wf
 

src/Lean/Elab/PreDefinition/WF/PackDomain.lean

@@ -124,8 +124,7 @@ where
       let args := e.getAppArgs
       let fNew := mkConst preDefsNew[funIdx]!.declName f.constLevels!
       let fNew := mkAppN fNew args[:fixedPrefix]
-      let Expr.forallE _ d .. ← whnf (← inferType fNew) | unreachable!
-      -- NB: Use whnf in case the type is not a manifest forall, but a definition around it
+      let Expr.forallE _ d .. ← inferType fNew | unreachable!
       let argNew ← mkUnaryArg d args[fixedPrefix:]
       return mkApp fNew argNew
     let rec

src/Lean/Elab/PreDefinition/WF/PackMutual.lean

@@ -51,13 +51,13 @@ private partial def mkNewCoDomain (preDefsOriginal : Array PreDefinition) (preDe
       let casesOn := mkAppN casesOn xTypeArgs -- parameters
       let casesOn := mkApp casesOn (← mkLambdaFVars #[x] (mkSort u)) -- motive
       let casesOn := mkApp casesOn x -- major
-      let minor1 ← withLocalDeclD (← mkFreshUserName `_x) xTypeArgs[0]! fun x => do
-        mkLambdaFVars #[x] ((← whnf preDefTypes[i]!).bindingBody!.instantiate1 x)
+      let minor1 ← withLocalDeclD (← mkFreshUserName `_x) xTypeArgs[0]! fun x =>
+        mkLambdaFVars #[x] (preDefTypes[i]!.bindingBody!.instantiate1 x)
       let minor2 ← withLocalDeclD (← mkFreshUserName `_x) xTypeArgs[1]! fun x => do
         mkLambdaFVars #[x] (← go x (i+1))
       return mkApp2 casesOn minor1 minor2
     else
-      return (← whnf preDefTypes[i]!).bindingBody!.instantiate1 x
+      return preDefTypes[i]!.bindingBody!.instantiate1 x
   go x 0
 
 /--
@@ -90,52 +90,34 @@ private partial def packValues (x : Expr) (codomain : Expr) (preDefValues : Arra
   go mvar.mvarId! x.fvarId! 0
   instantiateMVars mvar
 
-/--
-  Pass the first `n` arguments of `e` to the continuation, and apply the result to the
-  remaining arguments. If `e` does not have enough arguments, it is eta-expanded as needed.
-
-  Unlike `Meta.etaExpand` does not use `withDefault`.
--/
-def withAppN (n : Nat) (e : Expr) (k : Array Expr → MetaM Expr) : MetaM Expr := do
-  let args := e.getAppArgs
-  if n ≤ args.size then
-    let e' ← k args[:n]
-    return mkAppN e' args[n:]
-  else
-    let missing := n - args.size
-    forallBoundedTelescope (← inferType e) missing fun xs _ => do
-      if xs.size < missing then
-        throwError "Failed to eta-expand partial application"
-      let e' ← k (args ++ xs)
-      mkLambdaFVars xs e'
-
 /--
   Auxiliary function for replacing nested `preDefs` recursive calls in `e` with the new function `newFn`.
   See: `packMutual`
 -/
 private partial def post (fixedPrefix : Nat) (preDefs : Array PreDefinition) (domain : Expr) (newFn : Name) (e : Expr) : MetaM TransformStep := do
+  if e.getAppNumArgs != fixedPrefix + 1 then
+    return TransformStep.done e
   let f := e.getAppFn
   if !f.isConst then
     return TransformStep.done e
   let declName := f.constName!
   let us       := f.constLevels!
   if let some fidx := preDefs.findIdx? (·.declName == declName) then
-    let e' ← withAppN (fixedPrefix + 1) e fun args => do
-      let fixedArgs := args[:fixedPrefix]
-      let arg  := args[fixedPrefix]!
-      let rec mkNewArg (i : Nat) (type : Expr) : MetaM Expr := do
-        if i == preDefs.size - 1 then
-          return arg
-        else
-          (← whnfD type).withApp fun f args => do
-            assert! args.size == 2
-            if i == fidx then
-              return mkApp3 (mkConst ``PSum.inl f.constLevels!) args[0]! args[1]! arg
-            else
-              let r ← mkNewArg (i+1) args[1]!
-              return mkApp3 (mkConst ``PSum.inr f.constLevels!) args[0]! args[1]! r
-      return mkApp (mkAppN (mkConst newFn us) fixedArgs) (← mkNewArg 0 domain)
-    return TransformStep.done e'
+    let args := e.getAppArgs
+    let fixedArgs := args[:fixedPrefix]
+    let arg  := args.back
+    let rec mkNewArg (i : Nat) (type : Expr) : MetaM Expr := do
+      if i == preDefs.size - 1 then
+        return arg
+      else
+        (← whnfD type).withApp fun f args => do
+          assert! args.size == 2
+          if i == fidx then
+            return mkApp3 (mkConst ``PSum.inl f.constLevels!) args[0]! args[1]! arg
+          else
+            let r ← mkNewArg (i+1) args[1]!
+            return mkApp3 (mkConst ``PSum.inr f.constLevels!) args[0]! args[1]! r
+    return TransformStep.done <| mkApp (mkAppN (mkConst newFn us) fixedArgs) (← mkNewArg 0 domain)
   return TransformStep.done e
 
 partial def withFixedPrefix (fixedPrefix : Nat) (preDefs : Array PreDefinition) (k : Array Expr → Array Expr → Array Expr → MetaM α) : MetaM α :=
@@ -192,7 +174,7 @@ where
 def packMutual (fixedPrefix : Nat) (preDefsOriginal : Array PreDefinition) (preDefs : Array PreDefinition) : MetaM PreDefinition := do
   if preDefs.size == 1 then return preDefs[0]!
   withFixedPrefix fixedPrefix preDefs fun ys types vals => do
-    let domains ← types.mapM fun type => do pure (← whnf type).bindingDomain!
+    let domains := types.map fun type => type.bindingDomain!
     let domain ← mkNewDomain domains
     withLocalDeclD (← mkFreshUserName `_x) domain fun x => do
       let codomain ← mkNewCoDomain preDefsOriginal types x
@@ -201,7 +183,7 @@ def packMutual (fixedPrefix : Nat) (preDefsOriginal : Array PreDefinition) (preD
       let newFn := preDefs[0]!.declName ++ `_mutual
       let preDefNew := { preDefs[0]! with declName := newFn, type, value }
       addAsAxiom preDefNew
-      let value ← transform value (skipConstInApp := true) (post := post fixedPrefix preDefs domain newFn)
+      let value ← transform value (post := post fixedPrefix preDefs domain newFn)
       let value ← mkLambdaFVars (ys.push x) value
       return { preDefNew with value }
 

src/Lean/Elab/PreDefinition/WF/Preprocess.lean

@@ -1,37 +0,0 @@
-/-
-Copyright (c) 2021 Microsoft Corporation. All rights reserved.
-Released under Apache 2.0 license as described in the file LICENSE.
-Authors: Leonardo de Moura
--/
-import Lean.Meta.Transform
-import Lean.Elab.RecAppSyntax
-
-namespace Lean.Elab.WF
-open Meta
-
-/--
-Preprocesses the expessions to improve the effectiveness of `wfRecursion`.
-
-* Floats out the RecApp markers.
-  Example:
-  ```
-  def f : Nat → Nat
-    | 0 => 1
-    | i+1 => (f x) i
-  ```
-
-Unlike `Lean.Elab.Structural.preprocess`, do _not_ beta-reduce, as it could
-remove `let_fun`-lambdas that contain explicit termination proofs.
--/
-def preprocess (e : Expr) : CoreM Expr :=
-  Core.transform e
-    (post := fun e =>
-      match e with
-      | .app (.mdata m f) a =>
-        if m.isRecApp then
-          return .done (.mdata m (.app f a))
-        else
-          return .done e
-      | _ => return .done e)
-
-end Lean.Elab.WF

src/Lean/Elab/PreDefinition/WF/Rel.lean

@@ -53,21 +53,67 @@ private partial def unpackUnary (preDef : PreDefinition) (prefixSize : Nat) (mva
       mvarId.rename fvarId varNames.back
   go 0 mvarId fvarId
 
-def elabWFRel (preDefs : Array PreDefinition) (unaryPreDefName : Name) (fixedPrefixSize : Nat)
-    (argType : Expr) (wf : TerminationWF) (k : Expr → TermElabM α) : TermElabM α := do
+def getNumCandidateArgs (fixedPrefixSize : Nat) (preDefs : Array PreDefinition) : MetaM (Array Nat) := do
+  preDefs.mapM fun preDef =>
+    lambdaTelescope preDef.value fun xs _ =>
+      return xs.size - fixedPrefixSize
+
+/--
+  Given a predefinition with value `fun (x_₁ ... xₙ) (y_₁ : α₁)... (yₘ : αₘ) => ...`,
+  where `n = fixedPrefixSize`, return an array `A` s.t. `i ∈ A` iff `sizeOf yᵢ` reduces to a literal.
+  This is the case for types such as `Prop`, `Type u`, etc.
+  This arguments should not be considered when guessing a well-founded relation.
+  See `generateCombinations?`
+-/
+def getForbiddenByTrivialSizeOf (fixedPrefixSize : Nat) (preDef : PreDefinition) : MetaM (Array Nat) :=
+  lambdaTelescope preDef.value fun xs _ => do
+    let mut result := #[]
+    for x in xs[fixedPrefixSize:], i in [:xs.size] do
+      try
+        let sizeOf ← whnfD (← mkAppM ``sizeOf #[x])
+        if sizeOf.isLit then
+         result := result.push i
+      catch _ =>
+        result := result.push i
+    return result
+
+def generateCombinations? (forbiddenArgs : Array (Array Nat)) (numArgs : Array Nat) (threshold : Nat := 32) : Option (Array (Array Nat)) :=
+  go 0 #[] |>.run #[] |>.2
+where
+  isForbidden (fidx : Nat) (argIdx : Nat) : Bool :=
+    if h : fidx < forbiddenArgs.size then
+       forbiddenArgs.get ⟨fidx, h⟩ |>.contains argIdx
+    else
+      false
+
+  go (fidx : Nat) : OptionT (ReaderT (Array Nat) (StateM (Array (Array Nat)))) Unit := do
+    if h : fidx < numArgs.size then
+      let n := numArgs.get ⟨fidx, h⟩
+      for argIdx in [:n] do
+        unless isForbidden fidx argIdx do
+          withReader (·.push argIdx) (go (fidx + 1))
+    else
+      modify (·.push (← read))
+      if (← get).size > threshold then
+        failure
+termination_by _ fidx => numArgs.size - fidx
+
+def elabWFRel (preDefs : Array PreDefinition) (unaryPreDefName : Name) (fixedPrefixSize : Nat) (argType : Expr) (wf? : Option TerminationWF) (k : Expr → TermElabM α) : TermElabM α := do
   let α := argType
   let u ← getLevel α
   let expectedType := mkApp (mkConst ``WellFoundedRelation [u]) α
   trace[Elab.definition.wf] "elabWFRel start: {(← mkFreshTypeMVar).mvarId!}"
-  withDeclName unaryPreDefName do
-  match wf with
-  | TerminationWF.core wfStx =>
+  match wf? with
+  | some (TerminationWF.core wfStx) => withDeclName unaryPreDefName do
       let wfRel ← instantiateMVars (← withSynthesize <| elabTermEnsuringType wfStx expectedType)
       let pendingMVarIds ← getMVars wfRel
       discard <| logUnassignedUsingErrorInfos pendingMVarIds
       k wfRel
-  | TerminationWF.ext elements =>
-    withRef (getRefFromElems elements) do
+  | some (TerminationWF.ext elements) => go expectedType elements
+  | none => guess expectedType
+where
+  go (expectedType : Expr) (elements : Array TerminationByElement) : TermElabM α :=
+    withDeclName unaryPreDefName <| withRef (getRefFromElems elements) do
       let mainMVarId := (← mkFreshExprSyntheticOpaqueMVar expectedType).mvarId!
       let [fMVarId, wfRelMVarId, _] ← mainMVarId.apply (← mkConstWithFreshMVarLevels ``invImage) | throwError "failed to apply 'invImage'"
       let (d, fMVarId) ← fMVarId.intro1
@@ -81,4 +127,38 @@ def elabWFRel (preDefs : Array PreDefinition) (unaryPreDefName : Name) (fixedPre
       wfRelMVarId.assign wfRelVal
       k (← instantiateMVars (mkMVar mainMVarId))
 
+  generateElements (numArgs : Array Nat) (argCombination : Array Nat) : TermElabM (Array TerminationByElement) := do
+    let mut result := #[]
+    let var ← `(x)
+    let hole ← `(_)
+    for preDef in preDefs, numArg in numArgs, argIdx in argCombination, i in [:preDefs.size] do
+      let mut vars := #[var]
+      for _ in [:numArg - argIdx - 1] do
+        vars := vars.push hole
+      -- TODO: improve this.
+      -- The following trick allows a function `f` in a mutual block to invoke `g` appearing before it with the input argument.
+      -- We should compute the "right" order (if there is one) in the future.
+      let body ← if preDefs.size > 1 then `((sizeOf x, $(quote i))) else `(sizeOf x)
+      result := result.push {
+        ref := preDef.ref
+        declName := preDef.declName
+        vars := vars
+        body := body
+        implicit := false
+      }
+    return result
+
+  guess (expectedType : Expr) : TermElabM α := do
+    -- TODO: add support for lex
+    let numArgs ← getNumCandidateArgs fixedPrefixSize preDefs
+    -- TODO: include in `forbiddenArgs` arguments that are fixed but are not in the fixed prefix
+    let forbiddenArgs ← preDefs.mapM fun preDef => getForbiddenByTrivialSizeOf fixedPrefixSize preDef
+    -- TODO: add option to control the maximum number of cases to try
+    if let some combs := generateCombinations? forbiddenArgs numArgs then
+      for comb in combs do
+        let elements ← generateElements numArgs comb
+        if let some r ← observing? (go expectedType elements) then
+          return r
+    throwError "failed to prove termination, use `termination_by` to specify a well-founded relation"
+
 end Lean.Elab.WF

src/Lean/Elab/PreDefinition/WF/TerminationHint.lean

@@ -20,38 +20,31 @@ inductive TerminationHint where
   | many (map : NameMap TerminationHintValue)
   deriving Inhabited
 
-open Parser.Command in
-/--
-This function takes a user-specified `decreasing_by` or `termination_by'` clause (as `Sytnax`).
-If it is a `terminathionHintMany` (a set of clauses guarded by the function name) then
-* checks that all mentioned names exist in the current declaration
-* check that at most one function from each clique is mentioned
-and sort the entries by function name.
--/
 def expandTerminationHint (terminationHint? : Option Syntax) (cliques : Array (Array Name)) : MacroM TerminationHint := do
-  let some terminationHint := terminationHint? | return TerminationHint.none
-  let ref := terminationHint
-  match terminationHint with
-  | `(terminationByCore|termination_by' $hint1:terminationHint1)
-  | `(decreasingBy|decreasing_by $hint1:terminationHint1) =>
-    return TerminationHint.one { ref, value := hint1.raw[0] }
-  | `(terminationByCore|termination_by' $hints:terminationHintMany)
-  | `(decreasingBy|decreasing_by $hints:terminationHintMany) => do
-    let m ← hints.raw[0].getArgs.foldlM (init := {}) fun m arg =>
-      let declName? := cliques.findSome? fun clique => clique.findSome? fun declName =>
-        if arg[0].getId.isSuffixOf declName then some declName else none
-      match declName? with
-      | none => Macro.throwErrorAt arg[0] s!"function '{arg[0].getId}' not found in current declaration"
-      | some declName => return m.insert declName { ref := arg, value := arg[2] }
-    for clique in cliques do
-      let mut found? := Option.none
-      for declName in clique do
-        if let some { ref, .. } := m.find? declName then
-          if let some found := found? then
-            Macro.throwErrorAt ref s!"invalid termination hint element, '{declName}' and '{found}' are in the same clique"
-          found? := some declName
-    return TerminationHint.many m
-  | _ => Macro.throwUnsupported
+  if let some terminationHint := terminationHint? then
+    let ref := terminationHint
+    let terminationHint := terminationHint[1]
+    if terminationHint.getKind == ``Parser.Command.terminationHint1 then
+      return TerminationHint.one { ref, value := terminationHint[0] }
+    else if terminationHint.getKind == ``Parser.Command.terminationHintMany then
+      let m ← terminationHint[0].getArgs.foldlM (init := {}) fun m arg =>
+        let declName? := cliques.findSome? fun clique => clique.findSome? fun declName =>
+          if arg[0].getId.isSuffixOf declName then some declName else none
+        match declName? with
+        | none => Macro.throwErrorAt arg[0] s!"function '{arg[0].getId}' not found in current declaration"
+        | some declName => return m.insert declName { ref := arg, value := arg[2] }
+      for clique in cliques do
+        let mut found? := Option.none
+        for declName in clique do
+          if let some { ref, .. } := m.find? declName then
+            if let some found := found? then
+              Macro.throwErrorAt ref s!"invalid termination hint element, '{declName}' and '{found}' are in the same clique"
+            found? := some declName
+      return TerminationHint.many m
+    else
+      Macro.throwUnsupported
+  else
+    return TerminationHint.none
 
 def TerminationHint.markAsUsed (t : TerminationHint) (clique : Array Name) : TerminationHint :=
   match t with
@@ -60,6 +53,7 @@ def TerminationHint.markAsUsed (t : TerminationHint) (clique : Array Name) : Ter
   | TerminationHint.many m => Id.run do
     for declName in clique do
       if m.contains declName then
+        let m := m.erase declName
         let m := m.erase declName
         if m.isEmpty then
           return TerminationHint.none
@@ -79,9 +73,8 @@ def TerminationHint.ensureAllUsed (t : TerminationHint) : MacroM Unit := do
   | TerminationHint.many m  => m.forM fun _ v => Macro.throwErrorAt v.ref "unused termination hint element"
   | _ => pure ()
 
-/-! # Support for `termination_by` and `termination_by'` notation -/
+/-! # Support for `termination_by` notation -/
 
-/-- A single `termination_by` clause -/
 structure TerminationByElement where
   ref       : Syntax
   declName  : Name
@@ -90,76 +83,53 @@ structure TerminationByElement where
   implicit  : Bool
   deriving Inhabited
 
-/-- `terminatoin_by` clauses, grouped by clique -/
 structure TerminationByClique where
   elements : Array TerminationByElement
   used     : Bool := false
 
-/--
-A `termination_by'` or `termination_by` hint, as specified by the user
--/
 inductive TerminationBy where
-  /-- `termination_by'` -/
   | core (hint : TerminationHint)
-  /-- `termination_by` -/
   | ext  (cliques : Array TerminationByClique)
   deriving Inhabited
 
-/--
-A `termination_by'` or `termination_by` hint, as applicable to a single clique
--/
 inductive TerminationWF where
   | core (stx : Syntax)
   | ext  (clique : Array TerminationByElement)
 
 /-
-Expands the syntax for a `termination_by` clause, checking that
-* each function is mentioned once
-* each function mentioned actually occurs in the current declaration
-* if anything is specified, then all functions have a clause
-* the else-case (`_`) occurs only once, and only when needed
-
-NB:
 ```
 def terminationByElement   := leading_parser ppLine >> (ident <|> hole) >> many (ident <|> hole) >> " => " >> termParser >> optional ";"
 def terminationBy          := leading_parser ppLine >> "termination_by " >> many1chIndent terminationByElement
 ```
 -/
-open Parser.Command in
 private def expandTerminationByNonCore (hint : Syntax) (cliques : Array (Array Name)) : MacroM TerminationBy := do
-  let `(terminationBy|termination_by $elementStxs*) := hint | Macro.throwUnsupported
+  let elementStxs := hint[1].getArgs
   let mut alreadyFound : NameSet := {}
   let mut elseElemStx? := none
   for elementStx in elementStxs do
-    match elementStx with
-    | `(terminationByElement|$ident:ident $_* => $_) =>
-      let declSuffix := ident.getId
+    let declStx := elementStx[0]
+    if declStx.isIdent then
+      let declSuffix := declStx.getId
       if alreadyFound.contains declSuffix then
         withRef elementStx <| Macro.throwError s!"invalid `termination_by` syntax, `{declSuffix}` case has already been provided"
       alreadyFound := alreadyFound.insert declSuffix
       if cliques.all fun clique => clique.all fun declName => !declSuffix.isSuffixOf declName then
         withRef elementStx <| Macro.throwError s!"function '{declSuffix}' not found in current declaration"
-    | `(terminationByElement|_ $_vars* => $_term) =>
-      if elseElemStx?.isSome then
-        withRef elementStx <| Macro.throwError "invalid `termination_by` syntax, the else-case (i.e., `_ ... => ...`) has already been specified"
-      else
-        elseElemStx? := some elementStx
-    | _ => Macro.throwUnsupported
-  let toElement (declName : Name) (elementStx : TSyntax ``terminationByElement) : TerminationByElement :=
-    match elementStx with
-    | `(terminationByElement|$ioh $vars* => $body:term) =>
-    let implicit := !ioh.raw.isIdent
+    else if elseElemStx?.isSome then
+      withRef elementStx <| Macro.throwError "invalid `termination_by` syntax, the else-case (i.e., `_ ... => ...`) has already been specified"
+    else
+      elseElemStx? := some elementStx
+  let toElement (declName : Name) (elementStx : Syntax) : TerminationByElement :=
+    let vars     := elementStx[1].getArgs
+    let implicit := !elementStx[0].isIdent
+    let body     := elementStx[3]
     { ref := elementStx, declName, vars, implicit, body }
-    | _ => unreachable!
-  let elementAppliesTo (declName : Name) : TSyntax ``terminationByElement → Bool
-    | `(terminationByElement|$ident:ident $_* => $_) => ident.getId.isSuffixOf declName
-    | _ => false
   let mut result := #[]
   let mut usedElse := false
   for clique in cliques do
     let mut elements := #[]
     for declName in clique do
-      if let some elementStx := elementStxs.find? (elementAppliesTo declName) then
+      if let some elementStx := elementStxs.find? fun elementStx => elementStx[0].isIdent && elementStx[0].getId.isSuffixOf declName then
         elements := elements.push (toElement declName elementStx)
       else if let some elseElemStx := elseElemStx? then
         elements := elements.push (toElement declName elseElemStx)
@@ -172,9 +142,6 @@ private def expandTerminationByNonCore (hint : Syntax) (cliques : Array (Array N
     withRef elseElemStx?.get! <| Macro.throwError s!"invalid `termination_by` syntax, unnecessary else-case"
   return TerminationBy.ext result
 
-/--
-Expands the syntax for a `termination_by` or `termination_by'` clause, using the appropriate function
--/
 def expandTerminationBy (hint? : Option Syntax) (cliques : Array (Array Name)) : MacroM TerminationBy :=
   if let some hint := hint? then
     if hint.isOfKind ``Parser.Command.terminationByCore then
@@ -186,17 +153,6 @@ def expandTerminationBy (hint? : Option Syntax) (cliques : Array (Array Name)) :
   else
       return TerminationBy.core TerminationHint.none
 
-open Parser.Command in
-def TerminationWF.unexpand : TerminationWF → MetaM Syntax
-  | .ext elements => do
-    let elementStxs ← elements.mapM fun element => do
-      let fn : Ident := mkIdent (← unresolveNameGlobal element.declName)
-      let body : Term := ⟨element.body⟩
-      let vars : Array Ident := element.vars.map TSyntax.mk
-      `(terminationByElement|$fn $vars* => $body)
-    `(terminationBy|termination_by $elementStxs*)
-  | .core _ => unreachable! -- we don't synthetize termination_by' syntax
-
 def TerminationBy.markAsUsed (t : TerminationBy) (cliqueNames : Array Name) : TerminationBy :=
   match t with
   | core hint   => core (hint.markAsUsed cliqueNames)

src/Lean/Elab/RecAppSyntax.lean

@@ -27,10 +27,4 @@ def getRecAppSyntax? (e : Expr) : Option Syntax :=
     | _ => none
   | _                => none
 
-/--
-  Checks if the `MData` is for a recursive applciation.
--/
-def MData.isRecApp (d : MData) : Bool :=
-  d.contains recAppKey
-
 end Lean

src/Lean/Elab/Structure.lean

@@ -101,9 +101,8 @@ leading_parser try (declModifiers >> ident >> " :: ")
 private def expandCtor (structStx : Syntax) (structModifiers : Modifiers) (structDeclName : Name) : TermElabM StructCtorView := do
   let useDefault := do
     let declName := structDeclName ++ defaultCtorName
-    let ref := structStx[1].mkSynthetic
-    addAuxDeclarationRanges declName ref ref
-    pure { ref, modifiers := {}, name := defaultCtorName, declName }
+    addAuxDeclarationRanges declName structStx[2] structStx[2]
+    pure { ref := structStx, modifiers := {}, name := defaultCtorName, declName }
   if structStx[5].isNone then
     useDefault
   else
@@ -124,7 +123,7 @@ private def expandCtor (structStx : Syntax) (structModifiers : Modifiers) (struc
       let declName ← applyVisibility ctorModifiers.visibility declName
       addDocString' declName ctorModifiers.docString?
       addAuxDeclarationRanges declName ctor[1] ctor[1]
-      pure { ref := ctor[1], name, modifiers := ctorModifiers, declName }
+      pure { ref := ctor, name, modifiers := ctorModifiers, declName }
 
 def checkValidFieldModifier (modifiers : Modifiers) : TermElabM Unit := do
   if modifiers.isNoncomputable then
@@ -411,15 +410,14 @@ where
         | none =>
           let some fieldInfo := getFieldInfo? (← getEnv) parentStructName fieldName | unreachable!
           let addNewField : TermElabM α := do
+            let value? ← copyDefaultValue? fieldMap expandedStructNames parentStructName fieldName
             withLocalDecl fieldName fieldInfo.binderInfo fieldType fun fieldFVar => do
-              let fieldMap := fieldMap.insert fieldName fieldFVar
-              let value? ← copyDefaultValue? fieldMap expandedStructNames parentStructName fieldName
               let fieldDeclName := structDeclName ++ fieldName
               let fieldDeclName ← applyVisibility (← toVisibility fieldInfo) fieldDeclName
               addDocString' fieldDeclName (← findDocString? (← getEnv) fieldInfo.projFn)
               let infos := infos.push { name := fieldName, declName := fieldDeclName, fvar := fieldFVar, value?,
                                         kind := StructFieldKind.copiedField }
-              copy (i+1) infos fieldMap expandedStructNames
+              copy (i+1) infos (fieldMap.insert fieldName fieldFVar) expandedStructNames
           if fieldInfo.subobject?.isSome then
             let fieldParentStructName ← getStructureName fieldType
             if (← findExistingField? infos fieldParentStructName).isSome then
@@ -841,8 +839,8 @@ private def elabStructureView (view : StructView) : TermElabM Unit := do
           pure (info.isSubobject && decl.binderInfo.isInstImplicit)
         withSaveInfoContext do  -- save new env
           Term.addLocalVarInfo view.ref[1] (← mkConstWithLevelParams view.declName)
-          if let some _ := view.ctor.ref.getPos? (canonicalOnly := true) then
-            Term.addTermInfo' view.ctor.ref (← mkConstWithLevelParams view.ctor.declName) (isBinder := true)
+          if let some _ := view.ctor.ref[1].getPos? (canonicalOnly := true) then
+            Term.addTermInfo' view.ctor.ref[1] (← mkConstWithLevelParams view.ctor.declName) (isBinder := true)
           for field in view.fields do
             -- may not exist if overriding inherited field
             if (← getEnv).contains field.declName then

src/Lean/Elab/SyntheticMVars.lean

@@ -231,7 +231,7 @@ private def reportStuckSyntheticMVars (ignoreStuckTC := false) : TermElabM Unit
   for mvarId in pendingMVars do
     reportStuckSyntheticMVar mvarId ignoreStuckTC
 
-private def getSomeSyntheticMVarsRef : TermElabM Syntax := do
+private def getSomeSynthethicMVarsRef : TermElabM Syntax := do
   for mvarId in (← get).pendingMVars do
     if let some decl ← getSyntheticMVarDecl? mvarId then
       if decl.stx.getPos?.isSome then
@@ -395,7 +395,7 @@ mutual
   -/
   partial def synthesizeSyntheticMVars (mayPostpone := true) (ignoreStuckTC := false) : TermElabM Unit := do
     let rec loop (_ : Unit) : TermElabM Unit := do
-      withRef (← getSomeSyntheticMVarsRef) <| withIncRecDepth do
+      withRef (← getSomeSynthethicMVarsRef) <| withIncRecDepth do
         unless (← get).pendingMVars.isEmpty do
           if ← synthesizeSyntheticMVarsStep (postponeOnError := false) (runTactics := false) then
             loop ()

src/Lean/Elab/Tactic/BuiltinTactic.lean

@@ -232,15 +232,12 @@ partial def evalChoiceAux (tactics : Array Syntax) (i : Nat) : TacticM Unit :=
   | some msg => withRef stx[0] <| addRawTrace msg
 
 @[builtin_tactic Lean.Parser.Tactic.assumption] def evalAssumption : Tactic := fun _ =>
-  -- The `withAssignableSyntheticOpaque` is needed here to accommodate
-  -- `assumption` after `refine`.
-  -- See https://github.com/leanprover/lean4/issues/2361
-  liftMetaTactic fun mvarId => withAssignableSyntheticOpaque do mvarId.assumption; pure []
+  liftMetaTactic fun mvarId => do mvarId.assumption; pure []
 
 @[builtin_tactic Lean.Parser.Tactic.contradiction] def evalContradiction : Tactic := fun _ =>
   liftMetaTactic fun mvarId => do mvarId.contradiction; pure []
 
-@[builtin_tactic Lean.Parser.Tactic.eqRefl] def evalRefl : Tactic := fun _ =>
+@[builtin_tactic Lean.Parser.Tactic.refl] def evalRefl : Tactic := fun _ =>
   liftMetaTactic fun mvarId => do mvarId.refl; pure []
 
 @[builtin_tactic Lean.Parser.Tactic.intro] def evalIntro : Tactic := fun stx => do

src/Lean/Elab/Tactic/ElabTerm.lean

@@ -92,7 +92,7 @@ def sortMVarIdsByIndex [MonadMCtx m] [Monad m] (mvarIds : List MVarId) : m (List
 def withCollectingNewGoalsFrom (k : TacticM Expr) (tagSuffix : Name) (allowNaturalHoles := false) : TacticM (Expr × List MVarId) :=
   /-
   When `allowNaturalHoles = true`, unassigned holes should become new metavariables, including `_`s.
-  Thus, we set `holesAsSyntheticOpaque` to true if it is not already set to `true`.
+  Thus, we set `holesAsSynthethicOpaque` to true if it is not already set to `true`.
   See issue #1681. We have the tactic
   ```
   `refine' (fun x => _)
@@ -246,7 +246,7 @@ def elabTermForApply (stx : Syntax) (mayPostpone := true) : TacticM Expr := do
 
     By disabling "error to sorry", we also limit ourselves to at most one error at `t[h']`.
 
-    By disabling "error to sorry", we also miss the opportunity to catch mistakes in tactic code such as
+    By disabling "error to sorry", we also miss the opportunity to catch mistakes is tactic code such as
       `first | apply nonsensical-term | assumption`
 
     This should not be a big problem for the `apply` tactic since we usually provide small terms there.
@@ -317,7 +317,7 @@ def evalApplyLikeTactic (tac : MVarId → Expr → MetaM (List MVarId)) (e : Syn
   withTransparency TransparencyMode.all <| evalTactic stx[1]
 
 /--
-  Elaborate `stx`. If it is a free variable, return it. Otherwise, assert it, and return the free variable.
+  Elaborate `stx`. If it a free variable, return it. Otherwise, assert it, and return the free variable.
   Note that, the main goal is updated when `Meta.assert` is used in the second case. -/
 def elabAsFVar (stx : Syntax) (userName? : Option Name := none) : TacticM FVarId :=
   withMainContext do

src/Lean/Elab/Tactic/Induction.lean

@@ -264,6 +264,7 @@ def reorderAlts (alts : Array Alt) (altsSyntax : Array Syntax) : Array Alt := Id
 def evalAlts (elimInfo : ElimInfo) (alts : Array Alt) (optPreTac : Syntax) (altsSyntax : Array Syntax)
     (initialInfo : Info)
     (numEqs : Nat := 0) (numGeneralized : Nat := 0) (toClear : Array FVarId := #[]) : TacticM Unit := do
+  checkAltNames alts altsSyntax
   let hasAlts := altsSyntax.size > 0
   if hasAlts then
     -- default to initial state outside of alts
@@ -275,7 +276,6 @@ def evalAlts (elimInfo : ElimInfo) (alts : Array Alt) (optPreTac : Syntax) (alts
   else go
 where
   go := do
-    checkAltNames alts altsSyntax
     let alts := reorderAlts alts altsSyntax
     let hasAlts := altsSyntax.size > 0
     let mut usedWildcard := false

src/Lean/Elab/Tactic/Location.lean

@@ -39,16 +39,9 @@ def expandOptLocation (stx : Syntax) : Location :=
 
 open Meta
 
-/--
-Runs the given `atLocal` and `atTarget` methods on each of the locations selected by the given `loc`.
-
-* If `loc` is a list of locations, runs at each specified hypothesis (and finally the goal if `⊢` is included),
-  and fails if any of the tactic applications fail.
-* If `loc` is `*`, runs at the target first and then the hypotheses in reverse order.
-  If all tactic applications fail, `withLocation` with call `failed` with the main goal mvar.
-  If the tactic application closes the main goal, `withLocation` will then fail with `no goals to be solved`
-  upon reaching the first hypothesis.
--/
+/-- Runs the given `atLocal` and `atTarget` methods on each of the locations selected by the given `loc`.
+If any of the selected tactic applications fail, it will call `failed` with the main goal mvar.
+ -/
 def withLocation (loc : Location) (atLocal : FVarId → TacticM Unit) (atTarget : TacticM Unit) (failed : MVarId → TacticM Unit) : TacticM Unit := do
   match loc with
   | Location.targets hyps type =>

src/Lean/Elab/Tactic/Rewrite.lean

@@ -19,15 +19,13 @@ def rewriteTarget (stx : Syntax) (symm : Bool) (config : Rewrite.Config := {}) :
     replaceMainGoal (mvarId' :: r.mvarIds)
 
 def rewriteLocalDecl (stx : Syntax) (symm : Bool) (fvarId : FVarId) (config : Rewrite.Config := {}) :
-    TacticM Unit := withMainContext do
-  -- Note: we cannot execute `replaceLocalDecl` inside `Term.withSynthesize`.
-  -- See issues #2711 and #2727.
-  let rwResult ← Term.withSynthesize <| withMainContext do
+    TacticM Unit := do
+  Term.withSynthesize <| withMainContext do
     let e ← elabTerm stx none true
     let localDecl ← fvarId.getDecl
-    (← getMainGoal).rewrite localDecl.type e symm (config := config)
-  let replaceResult ← (← getMainGoal).replaceLocalDecl fvarId rwResult.eNew rwResult.eqProof
-  replaceMainGoal (replaceResult.mvarId :: rwResult.mvarIds)
+    let rwResult ← (← getMainGoal).rewrite localDecl.type e symm (config := config)
+    let replaceResult ← (← getMainGoal).replaceLocalDecl fvarId rwResult.eNew rwResult.eqProof
+    replaceMainGoal (replaceResult.mvarId :: rwResult.mvarIds)
 
 def withRWRulesSeq (token : Syntax) (rwRulesSeqStx : Syntax) (x : (symm : Bool) → (term : Syntax) → TacticM Unit) : TacticM Unit := do
   let lbrak := rwRulesSeqStx[0]
@@ -45,18 +43,14 @@ def withRWRulesSeq (token : Syntax) (rwRulesSeqStx : Syntax) (x : (symm : Bool)
         let symm := !rule[0].isNone
         let term := rule[1]
         let processId (id : Syntax) : TacticM Unit := do
-          -- See if we can interpret `id` as a hypothesis first.
-          if (← optional <| getFVarId id).isSome then
-            x symm term
-          else
-            -- Try to get equation theorems for `id`.
-            let declName ← try resolveGlobalConstNoOverload id catch _ => return (← x symm term)
-            let some eqThms ← getEqnsFor? declName (nonRec := true) | x symm term
-            let rec go : List Name →  TacticM Unit
-              | [] => throwError "failed to rewrite using equation theorems for '{declName}'"
-              | eqThm::eqThms => (x symm (mkIdentFrom id eqThm)) <|> go eqThms
-            go eqThms.toList
-            discard <| Term.addTermInfo id (← mkConstWithFreshMVarLevels declName) (lctx? := ← getLCtx)
+          -- Try to get equation theorems for `id` first
+          let declName ← try resolveGlobalConstNoOverload id catch _ => return (← x symm term)
+          let some eqThms ← getEqnsFor? declName (nonRec := true) | x symm term
+          let rec go : List Name →  TacticM Unit
+            | [] => throwError "failed to rewrite using equation theorems for '{declName}'"
+            | eqThm::eqThms => (x symm (mkIdentFrom id eqThm)) <|> go eqThms
+          go eqThms.toList
+          discard <| Term.addTermInfo id (← mkConstWithFreshMVarLevels declName) (lctx? := ← getLCtx)
         match term with
         | `($id:ident)  => processId id
         | `(@$id:ident) => processId id

src/Lean/Elab/Tactic/Simp.lean

@@ -101,17 +101,6 @@ private def addDeclToUnfoldOrTheorem (thms : Meta.SimpTheorems) (id : Origin) (e
         return thms.addDeclToUnfoldCore declName
       else
         thms.addDeclToUnfold declName
-  else if e.isFVar then
-    let fvarId := e.fvarId!
-    let decl ← fvarId.getDecl
-    if (← isProp decl.type) then
-      thms.add id #[] e (post := post) (inv := inv)
-    else if !decl.isLet then
-      throwError "invalid argument, variable is not a proposition or let-declaration"
-    else if inv then
-      throwError "invalid '←' modifier, '{e}' is a let-declaration name to be unfolded"
-    else
-      return thms.addLetDeclToUnfold fvarId
   else
     thms.add id #[] e (post := post) (inv := inv)
 
@@ -248,10 +237,6 @@ def mkSimpContext (stx : Syntax) (eraseLocal : Bool) (kind := SimpKind.simp) (ig
   else
     let ctx := r.ctx
     let mut simpTheorems := ctx.simpTheorems
-    /-
-    When using `zeta := false`, we do not expand let-declarations when using `[*]`.
-    Users must explicitly include it in the list.
-    -/
     let hs ← getPropHyps
     for h in hs do
       unless simpTheorems.isErased (.fvar h) do
@@ -283,7 +268,7 @@ def traceSimpCall (stx : Syntax) (usedSimps : UsedSimps) : MetaM Unit := do
     | .fvar fvarId => -- local hypotheses in the context
       if let some ldecl := lctx.find? fvarId then
         localsOrStar := localsOrStar.bind fun locals =>
-          if !ldecl.userName.isInaccessibleUserName && !ldecl.userName.hasMacroScopes &&
+          if !ldecl.userName.isInaccessibleUserName &&
               (lctx.findFromUserName? ldecl.userName).get!.fvarId == ldecl.fvarId then
             some (locals.push ldecl.userName)
           else
@@ -337,14 +322,14 @@ where
 /-
   "simp " (config)? (discharger)? ("only ")? ("[" simpLemma,* "]")? (location)?
 -/
-@[builtin_tactic Lean.Parser.Tactic.simp] def evalSimp : Tactic := fun stx => withMainContext do
-  let { ctx, dischargeWrapper } ← mkSimpContext stx (eraseLocal := false)
+@[builtin_tactic Lean.Parser.Tactic.simp] def evalSimp : Tactic := fun stx => do
+  let { ctx, dischargeWrapper } ← withMainContext <| mkSimpContext stx (eraseLocal := false)
   let usedSimps ← dischargeWrapper.with fun discharge? =>
     simpLocation ctx discharge? (expandOptLocation stx[5])
   if tactic.simp.trace.get (← getOptions) then
     traceSimpCall stx usedSimps
 
-@[builtin_tactic Lean.Parser.Tactic.simpAll] def evalSimpAll : Tactic := fun stx => withMainContext do
+@[builtin_tactic Lean.Parser.Tactic.simpAll] def evalSimpAll : Tactic := fun stx => do
   let { ctx, .. } ← mkSimpContext stx (eraseLocal := true) (kind := .simpAll) (ignoreStarArg := true)
   let (result?, usedSimps) ← simpAll (← getMainGoal) ctx
   match result? with
@@ -370,7 +355,7 @@ where
     | none => replaceMainGoal []
     | some mvarId => replaceMainGoal [mvarId]
     if tactic.simp.trace.get (← getOptions) then
-      mvarId.withContext <| traceSimpCall (← getRef) usedSimps
+      traceSimpCall (← getRef) usedSimps
 
 @[builtin_tactic Lean.Parser.Tactic.dsimp] def evalDSimp : Tactic := fun stx => do
   let { ctx, .. } ← withMainContext <| mkSimpContext stx (eraseLocal := false) (kind := .dsimp)

src/Lean/Elab/Term.lean

@@ -211,7 +211,7 @@ structure Context where
   saveRecAppSyntax : Bool := true
   /--
   If `holesAsSyntheticOpaque` is `true`, then we mark metavariables associated
-  with `_`s as `syntheticOpaque` if they do not occur in patterns.
+  with `_`s as `synthethicOpaque` if they do not occur in patterns.
   This option is useful when elaborating terms in tactics such as `refine'` where
   we want holes there to become new goals. See issue #1681, we have
   `refine' (fun x => _)

src/Lean/Elab/Util.lean

@@ -50,7 +50,7 @@ def getBetterRef (ref : Syntax) (macroStack : MacroStack) : Syntax :=
 register_builtin_option pp.macroStack : Bool := {
   defValue := false
   group    := "pp"
-  descr    := "display macro expansion stack"
+  descr    := "dispaly macro expansion stack"
 }
 
 def addMacroStack {m} [Monad m] [MonadOptions m] (msgData : MessageData) (macroStack : MacroStack) : m MessageData := do

src/Lean/Environment.lean

@@ -255,20 +255,20 @@ structure EnvExtensionInterface where
   ext          : Type → Type
   inhabitedExt : Inhabited σ → Inhabited (ext σ)
   registerExt  (mkInitial : IO σ) : IO (ext σ)
-  setState     (e : ext σ) (exts : Array EnvExtensionState) : σ → Array EnvExtensionState
-  modifyState  (e : ext σ) (exts : Array EnvExtensionState) : (σ → σ) → Array EnvExtensionState
-  getState     [Inhabited σ] (e : ext σ) (exts : Array EnvExtensionState) : σ
+  setState     (e : ext σ) (env : Environment) : σ → Environment
+  modifyState  (e : ext σ) (env : Environment) : (σ → σ) → Environment
+  getState     [Inhabited σ] (e : ext σ) (env : Environment) : σ
   mkInitialExtStates : IO (Array EnvExtensionState)
-  ensureExtensionsSize : Array EnvExtensionState → IO (Array EnvExtensionState)
+  ensureExtensionsSize : Environment → IO Environment
 
 instance : Inhabited EnvExtensionInterface where
   default := {
     ext                  := id
     inhabitedExt         := id
-    ensureExtensionsSize := fun exts => pure exts
+    ensureExtensionsSize := fun env => pure env
     registerExt          := fun mk => mk
-    setState             := fun _ exts _ => exts
-    modifyState          := fun _ exts _ => exts
+    setState             := fun _ env _ => env
+    modifyState          := fun _ env _ => env
     getState             := fun ext _ => ext
     mkInitialExtStates   := pure #[]
   }
@@ -290,40 +290,41 @@ private builtin_initialize envExtensionsRef : IO.Ref (Array (Ext EnvExtensionSta
   user-defined environment extensions. When this happens, we must adjust the size of the `env.extensions`.
   This method is invoked when processing `import`s.
 -/
-partial def ensureExtensionsArraySize (exts : Array EnvExtensionState) : IO (Array EnvExtensionState) := do
-  loop exts.size exts
+partial def ensureExtensionsArraySize (env : Environment) : IO Environment := do
+  loop env.extensions.size env
 where
-  loop (i : Nat) (exts : Array EnvExtensionState) : IO (Array EnvExtensionState) := do
+  loop (i : Nat) (env : Environment) : IO Environment := do
     let envExtensions ← envExtensionsRef.get
     if i < envExtensions.size then
       let s ← envExtensions[i]!.mkInitial
-      let exts := exts.push s
-      loop (i + 1) exts
+      let env := { env with extensions := env.extensions.push s }
+      loop (i + 1) env
     else
-      return exts
+      return env
 
 private def invalidExtMsg := "invalid environment extension has been accessed"
 
-unsafe def setState {σ} (ext : Ext σ) (exts : Array EnvExtensionState) (s : σ) : Array EnvExtensionState :=
-  if h : ext.idx < exts.size then
-    exts.set ⟨ext.idx, h⟩ (unsafeCast s)
+unsafe def setState {σ} (ext : Ext σ) (env : Environment) (s : σ) : Environment :=
+  if h : ext.idx < env.extensions.size then
+    { env with extensions := env.extensions.set ⟨ext.idx, h⟩ (unsafeCast s) }
   else
-    have : Inhabited (Array EnvExtensionState) := ⟨exts⟩
+    have : Inhabited Environment := ⟨env⟩
     panic! invalidExtMsg
 
-@[inline] unsafe def modifyState {σ : Type} (ext : Ext σ) (exts : Array EnvExtensionState) (f : σ → σ) : Array EnvExtensionState :=
-  if ext.idx < exts.size then
-    exts.modify ext.idx fun s =>
-      let s : σ := unsafeCast s
-      let s : σ := f s
-      unsafeCast s
+@[inline] unsafe def modifyState {σ : Type} (ext : Ext σ) (env : Environment) (f : σ → σ) : Environment :=
+  if ext.idx < env.extensions.size then
+    { env with
+      extensions := env.extensions.modify ext.idx fun s =>
+        let s : σ := unsafeCast s
+        let s : σ := f s
+        unsafeCast s }
   else
-    have : Inhabited (Array EnvExtensionState) := ⟨exts⟩
+    have : Inhabited Environment := ⟨env⟩
     panic! invalidExtMsg
 
-unsafe def getState {σ} [Inhabited σ] (ext : Ext σ) (exts : Array EnvExtensionState) : σ :=
-  if h : ext.idx < exts.size then
-    let s : EnvExtensionState := exts.get ⟨ext.idx, h⟩
+unsafe def getState {σ} [Inhabited σ] (ext : Ext σ) (env : Environment) : σ :=
+  if h : ext.idx < env.extensions.size then
+    let s : EnvExtensionState := env.extensions.get ⟨ext.idx, h⟩
     unsafeCast s
   else
     panic! invalidExtMsg
@@ -362,22 +363,14 @@ opaque EnvExtensionInterfaceImp : EnvExtensionInterface
 
 def EnvExtension (σ : Type) : Type := EnvExtensionInterfaceImp.ext σ
 
-private def ensureExtensionsArraySize (env : Environment) : IO Environment := do
-  let exts ← EnvExtensionInterfaceImp.ensureExtensionsSize env.extensions
-  return { env with extensions := exts }
+private def ensureExtensionsArraySize (env : Environment) : IO Environment :=
+  EnvExtensionInterfaceImp.ensureExtensionsSize env
 
 namespace EnvExtension
 instance {σ} [s : Inhabited σ] : Inhabited (EnvExtension σ) := EnvExtensionInterfaceImp.inhabitedExt s
-
-def setState {σ : Type} (ext : EnvExtension σ) (env : Environment) (s : σ) : Environment :=
-  { env with extensions := EnvExtensionInterfaceImp.setState ext env.extensions s }
-
-def modifyState {σ : Type} (ext : EnvExtension σ) (env : Environment) (f : σ → σ) : Environment :=
-  { env with extensions := EnvExtensionInterfaceImp.modifyState ext env.extensions f }
-
-def getState {σ : Type} [Inhabited σ] (ext : EnvExtension σ) (env : Environment) : σ :=
-  EnvExtensionInterfaceImp.getState ext env.extensions
-
+def setState {σ : Type} (ext : EnvExtension σ) (env : Environment) (s : σ) : Environment := EnvExtensionInterfaceImp.setState ext env s
+def modifyState {σ : Type} (ext : EnvExtension σ) (env : Environment) (f : σ → σ) : Environment := EnvExtensionInterfaceImp.modifyState ext env f
+def getState {σ : Type} [Inhabited σ] (ext : EnvExtension σ) (env : Environment) : σ := EnvExtensionInterfaceImp.getState ext env
 end EnvExtension
 
 /-- Environment extensions can only be registered during initialization.
@@ -765,17 +758,7 @@ partial def importModulesCore (imports : Array Import) : ImportStateM Unit := do
       moduleNames := s.moduleNames.push i.module
     }
 
-/--
-  Construct environment from `importModulesCore` results.
-
-  If `leakEnv` is true, we mark the environment as persistent, which means it
-  will not be freed. We set this when the object would survive until the end of
-  the process anyway. In exchange, RC updates are avoided, which is especially
-  important when they would be atomic because the environment is shared across
-  threads (potentially, storing it in an `IO.Ref` is sufficient for marking it
-  as such). -/
-def finalizeImport (s : ImportState) (imports : Array Import) (opts : Options) (trustLevel : UInt32 := 0)
-    (leakEnv := false) : IO Environment := do
+def finalizeImport (s : ImportState) (imports : Array Import) (opts : Options) (trustLevel : UInt32 := 0) : IO Environment := do
   let numConsts := s.moduleData.foldl (init := 0) fun numConsts mod =>
     numConsts + mod.constants.size + mod.extraConstNames.size
   let mut const2ModIdx : HashMap Name ModuleIdx := mkHashMap (capacity := numConsts)
@@ -793,7 +776,7 @@ def finalizeImport (s : ImportState) (imports : Array Import) (opts : Options) (
       const2ModIdx := const2ModIdx.insert cname modIdx
   let constants : ConstMap := SMap.fromHashMap constantMap false
   let exts ← mkInitialExtensionStates
-  let mut env : Environment := {
+  let env : Environment := {
     const2ModIdx    := const2ModIdx
     constants       := constants
     extraConstNames := {}
@@ -807,35 +790,18 @@ def finalizeImport (s : ImportState) (imports : Array Import) (opts : Options) (
       moduleData   := s.moduleData
     }
   }
-  env ← setImportedEntries env s.moduleData
-  if leakEnv then
-    /- Mark persistent a first time before `finalizePersistenExtensions`, which
-       avoids costly MT markings when e.g. an interpreter closure (which
-       contains the environment) is put in an `IO.Ref`. This can happen in e.g.
-       initializers of user environment extensions and is wasteful because the
-       environment is marked persistent immediately afterwards anyway when the
-       constructed extension including the closure is ultimately stored in the
-       initialized constant. We have seen significant savings in `open Mathlib`
-       timings, where we have both a big environment and interpreted environment
-       extensions, from this. There is no significant extra cost to calling
-       `markPersistent` multiple times like this. -/
-    env := Runtime.markPersistent env
-  env ← finalizePersistentExtensions env s.moduleData opts
-  if leakEnv then
-    /- Ensure the final environment including environment extension states is
-       marked persistent as documented. -/
-    env := Runtime.markPersistent env
+  let env ← setImportedEntries env s.moduleData
+  let env ← finalizePersistentExtensions env s.moduleData opts
   pure env
 
 @[export lean_import_modules]
-def importModules (imports : Array Import) (opts : Options) (trustLevel : UInt32 := 0)
-    (leakEnv := false) : IO Environment := profileitIO "import" opts do
+def importModules (imports : Array Import) (opts : Options) (trustLevel : UInt32 := 0) : IO Environment := profileitIO "import" opts do
   for imp in imports do
     if imp.module matches .anonymous then
       throw <| IO.userError "import failed, trying to import module with anonymous name"
   withImporting do
     let (_, s) ← importModulesCore imports |>.run
-    finalizeImport (leakEnv := leakEnv) s imports opts trustLevel
+    finalizeImport s imports opts trustLevel
 
 /--
   Create environment object from imports and free compacted regions after calling `act`. No live references to the

src/Lean/Expr.lean

@@ -60,7 +60,7 @@ def bar ⦃x : Nat⦄ : Nat := x
 #check bar -- bar : ⦃x : Nat⦄ → Nat
 ```
 
-See also [the Lean manual](https://lean-lang.org/lean4/doc/expressions.html#implicit-arguments).
+See also the Lean manual: https://lean-lang.org/lean4/doc/expressions.html#implicit-arguments
 -/
 inductive BinderInfo where
   /-- Default binder annotation, e.g. `(x : α)` -/
@@ -300,8 +300,8 @@ inductive Expr where
   above it (i.e. introduced by a `lam`, `forallE`, or `letE`).
 
   The `deBruijnIndex` parameter is the *de-Bruijn* index for the bound
-  variable. See [the Wikipedia page on de-Bruijn indices](https://en.wikipedia.org/wiki/De_Bruijn_index)
-  for additional information.
+  variable. See [here](https://en.wikipedia.org/wiki/De_Bruijn_index)
+  for additional information on de-Bruijn indexes.
 
   For example, consider the expression `fun x : Nat => forall y : Nat, x = y`.
   The `x` and `y` variables in the equality expression are constructed
@@ -319,11 +319,11 @@ inductive Expr where
   | bvar (deBruijnIndex : Nat)
 
   /--
-  The `fvar` constructor represent free variables. These *free* variable
+  The `fvar` constructor represent free variables. These /free/ variable
   occurrences are not bound by an earlier `lam`, `forallE`, or `letE`
   constructor and its binder exists in a local context only.
 
-  Note that Lean uses the *locally nameless approach*. See [McBride and McKinna](https://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.365.2479&rep=rep1&type=pdf)
+  Note that Lean uses the /locally nameless approach/. See [here](https://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.365.2479&rep=rep1&type=pdf)
   for additional details.
 
   When "visiting" the body of a binding expression (i.e. `lam`, `forallE`, or `letE`),
@@ -361,7 +361,7 @@ inductive Expr where
   A function application.
 
   For example, the natural number one, i.e. `Nat.succ Nat.zero` is represented as
-  ``Expr.app (.const `Nat.succ []) (.const .zero [])``.
+  `Expr.app (.const `Nat.succ []) (.const .zero [])`
   Note that multiple arguments are represented using partial application.
 
   For example, the two argument application `f x y` is represented as
@@ -387,15 +387,15 @@ inductive Expr where
 
   For example:
   - `forall x : Prop, x ∧ x`:
-    ```lean
-    Expr.forallE `x (.sort .zero)
-      (.app (.app (.const `And []) (.bvar 0)) (.bvar 0)) .default
-    ```
+  ```lean
+  Expr.forallE `x (.sort .zero)
+    (.app (.app (.const `And []) (.bvar 0)) (.bvar 0)) .default
+  ```
   - `Nat → Bool`:
-    ```lean
-    Expr.forallE `a (.const `Nat [])
-      (.const `Bool []) .default
-    ```
+  ```lean
+  Expr.forallE `a (.const `Nat [])
+    (.const `Bool []) .default
+  ```
   -/
   | forallE (binderName : Name) (binderType : Expr) (body : Expr) (binderInfo : BinderInfo)
 
@@ -450,11 +450,11 @@ inductive Expr where
   The type of `struct` must be an structure-like inductive type. That is, it has only one
   constructor, is not recursive, and it is not an inductive predicate. The kernel and elaborators
   check whether the `typeName` matches the type of `struct`, and whether the (zero-based) index
-  is valid (i.e., it is smaller than the number of constructor fields).
+  is valid (i.e., it is smaller than the numbef of constructor fields).
   When exporting Lean developments to other systems, `proj` can be replaced with `typeName`.`rec`
   applications.
 
-  Example, given `a : Nat × Bool`, `a.1` is represented as
+  Example, given `a : Nat x Bool`, `a.1` is represented as
   ```
   .proj `Prod 0 a
   ```
@@ -774,8 +774,8 @@ instance : BEq Expr where
   beq := Expr.eqv
 
 /--
-Return `true` iff `a` and `b` are equal.
-Binder names and annotations are taken into account.
+Return true iff `a` and `b` are equal.
+Binder names and annotations are taking into account.
 -/
 @[extern "lean_expr_equal"]
 opaque equal (a : @& Expr) (b : @& Expr) : Bool
@@ -831,7 +831,7 @@ def isConst : Expr → Bool
   | _        => false
 
 /--
-Return `true` if the given expression is a constant of the given name.
+Return `true` if the given expression is a constant of the give name.
 Examples:
 - `` (.const `Nat []).isConstOf `Nat `` is `true`
 - `` (.const `Nat []).isConstOf `False `` is `false`
@@ -1332,14 +1332,6 @@ lambda expression. See docstring for `betaRev` for examples.
 def beta (f : Expr) (args : Array Expr) : Expr :=
   betaRev f args.reverse
 
-/--
-Count the number of lambdas at the head of the given expression.
--/
-def getNumHeadLambdas : Expr → Nat
-  | .lam _ _ b _ => getNumHeadLambdas b + 1
-  | .mdata _ b => getNumHeadLambdas b
-  | _ => 0
-
 /--
 Return true if the given expression is the function of an expression that is target for (head) beta reduction.
 If `useZeta = true`, then `let`-expressions are visited. That is, it assumes

src/Lean/Level.lean

@@ -205,9 +205,6 @@ def ofNat : Nat → Level
   | 0   => levelZero
   | n+1 => mkLevelSucc (ofNat n)
 
-instance instOfNat (n : Nat) : OfNat Level n where
-  ofNat := ofNat n
-
 def addOffsetAux : Nat → Level → Level
   | 0,     u => u
   | (n+1), u => addOffsetAux n (mkLevelSucc u)

src/Lean/Linter/Util.lean

@@ -10,12 +10,6 @@ def logLint [Monad m] [MonadLog m] [AddMessageContext m] [MonadOptions m]
     (linterOption : Lean.Option Bool) (stx : Syntax) (msg : MessageData) : m Unit :=
   logWarningAt stx (.tagged linterOption.name m!"{msg} [{linterOption.name}]")
 
-/-- If `linterOption` is true, print a linter warning message at the position determined by `stx`.
--/
-def logLintIf [Monad m] [MonadLog m] [AddMessageContext m] [MonadOptions m]
-    (linterOption : Lean.Option Bool) (stx : Syntax) (msg : MessageData) : m Unit := do
-  if linterOption.get (← getOptions) then logLint linterOption stx msg
-
 /-- Go upwards through the given `tree` starting from the smallest node that
 contains the given `range` and collect all `MacroExpansionInfo`s on the way up.
 The result is `some []` if no `MacroExpansionInfo` was found on the way and

src/Lean/Meta/ACLt.lean

@@ -60,8 +60,8 @@ where
       -- Drawback: cost.
       return e
     else match mode with
-      | .reduce => DiscrTree.reduce e {}
-      | .reduceSimpleOnly => DiscrTree.reduce e { iota := false, proj := .no }
+      | .reduce => DiscrTree.reduce e (simpleReduce := false)
+      | .reduceSimpleOnly => DiscrTree.reduce e (simpleReduce := true)
       | .none => return e
 
   lt (a b : Expr) : MetaM Bool := do

src/Lean/Meta/AbstractNestedProofs.lean

@@ -72,11 +72,7 @@ partial def visit (e : Expr) : M Expr := do
 end AbstractNestedProofs
 
 /-- Replace proofs nested in `e` with new lemmas. The new lemmas have names of the form `mainDeclName.proof_<idx>` -/
-def abstractNestedProofs (mainDeclName : Name) (e : Expr) : MetaM Expr := do
-  if (← isProof e) then
-    -- `e` is a proof itself. So, we don't abstract nested proofs
-    return e
-  else
-    AbstractNestedProofs.visit e |>.run { baseName := mainDeclName } |>.run |>.run' { nextIdx := 1 }
+def abstractNestedProofs (mainDeclName : Name) (e : Expr) : MetaM Expr :=
+  AbstractNestedProofs.visit e |>.run { baseName := mainDeclName } |>.run |>.run' { nextIdx := 1 }
 
 end Lean.Meta