feat: add control and arrow_telescope simproc DSL primitives

Add two new `sym_simproc` primitives for use as `pre` simprocs:
- `control` — simplifies control-flow expressions (`if-then-else`,
  `match`, `cond`, `dite`), visiting only conditions and discriminants
- `arrow_telescope` — simplifies arrow telescopes
  (`p₁ → p₂ → ... → q`) without entering binders

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

.claude/CLAUDE.md

@@ -7,11 +7,6 @@ To build Lean you should use `make -j$(nproc) -C build/release`.
 The build uses `ccache`, and in a sandbox `ccache` may complain about read-only file systems.
 Use `CCACHE_READONLY` and `CCACHE_TEMPDIR` instead of disabling ccache completely.
 
-To rebuild individual modules without a full build, use Lake directly:
-```
-cd src && lake build Init.Prelude
-```
-
 ## Running Tests
 
 See `tests/README.md` for full documentation. Quick reference:
@@ -61,11 +56,6 @@ make -C build/release/stage2 clean-stdlib
 ```
 must be run manually before building.
 
-To rebuild individual stage 2 modules without a full `make stage2`, use Lake directly:
-```
-cd build/release/stage2 && lake build Init.Prelude
-```
-
 ## New features
 
 When asked to implement new features:

.claude/commands/release.md

@@ -157,16 +157,6 @@ Note: `gh pr checks --watch` exits as soon as ALL checks complete (pass or fail)
 fail while others are still running, `--watch` will continue until everything settles, then exit
 with a non-zero code. So a background `--watch` finishing = all checks done; check which failed.
 
-## Mathlib Bump Branches
-
-Mathlib `bump/v4.X.0` branches live on the **fork** `leanprover-community/mathlib4-nightly-testing`,
-NOT on `leanprover-community/mathlib4`.
-
-## Never Force-Update Remote Refs Without Confirmation
-
-Never force-update an existing remote branch or tag via `git push --force` or the GitHub API
-without explicit user confirmation.
-
 ## Error Handling
 
 **CRITICAL**: If something goes wrong or a command fails:

.github/workflows/build-template.yml

@@ -33,7 +33,7 @@ jobs:
         include: ${{fromJson(inputs.config)}}
       # complete all jobs
       fail-fast: false
-    runs-on: ${{ endsWith(matrix.os, '-with-cache') && fromJSON(format('["{0}", "nscloud-git-mirror-5gb"]', matrix.os)) || matrix.os }}
+    runs-on: ${{ endsWith(matrix.os, '-with-cache') && fromJSON(format('["{0}", "nscloud-git-mirror-1gb"]', matrix.os)) || matrix.os }}
     defaults:
       run:
         shell: ${{ matrix.shell || 'nix develop -c bash -euxo pipefail {0}' }}
@@ -78,7 +78,7 @@ jobs:
       # (needs to be after "Install *" to use the right shell)
       - name: CI Merge Checkout
         run: |
-          git fetch --depth=${{ matrix.name == 'Linux Lake (Cached)' && '10' || '1' }} origin ${{ github.sha }}
+          git fetch --depth=1 origin ${{ github.sha }}
           git checkout FETCH_HEAD flake.nix flake.lock script/prepare-* tests/elab/importStructure.lean
         if: github.event_name == 'pull_request'
       # (needs to be after "Checkout" so files don't get overridden)
@@ -125,7 +125,7 @@ jobs:
           else
             echo "TARGET_STAGE=stage1" >> $GITHUB_ENV
           fi
-      - name: Configure Build
+      - name: Build
         run: |
           ulimit -c unlimited  # coredumps
           [ -d build ] || mkdir build
@@ -162,21 +162,7 @@ jobs:
           fi
           # contortion to support empty OPTIONS with old macOS bash
           cmake .. --preset ${{ matrix.CMAKE_PRESET || 'release' }} -B . ${{ matrix.CMAKE_OPTIONS }} ${OPTIONS[@]+"${OPTIONS[@]}"} -DLEAN_INSTALL_PREFIX=$PWD/..
-      - name: Build Stage 0 & Configure Stage 1
-        run: |
-          ulimit -c unlimited  # coredumps
-          time make -C build stage1-configure -j$NPROC
-      - name: Download Lake Cache
-        if: matrix.name == 'Linux Lake (Cached)'
-        run: |
-          cd src
-          ../build/stage0/bin/lake cache get --repo=${{ github.repository }}
-        timeout-minutes: 20 # prevent excessive hanging from network issues
-        continue-on-error: true
-      - name: Build Target Stage
-        run: |
-          ulimit -c unlimited  # coredumps
-          time make -C build $TARGET_STAGE -j$NPROC
+          time make $TARGET_STAGE -j$NPROC
       # Should be done as early as possible and in particular *before* "Check rebootstrap" which
       # changes the state of stage1/
       - name: Save Cache
@@ -195,21 +181,6 @@ jobs:
             build/stage1/**/*.c
             build/stage1/**/*.c.o*' || '' }}
           key: ${{ steps.restore-cache.outputs.cache-primary-key }}
-      - name: Upload Lake Cache
-        # Caching on cancellation created some mysterious issues perhaps related to improper build
-        # shutdown. Also, since this needs access to secrets, it cannot be run on forks.
-        if: matrix.name == 'Linux Lake' && !cancelled() && (github.event_name != 'pull_request' || github.event.pull_request.head.repo.full_name == github.repository)
-        run: |
-          curl --version
-          cd src
-          time ../build/stage0/bin/lake build -o ../build/lake-mappings.jsonl
-          time ../build/stage0/bin/lake cache put ../build/lake-mappings.jsonl --repo=${{ github.repository }}
-        env:
-          LAKE_CACHE_KEY: ${{ secrets.LAKE_CACHE_KEY }}
-          LAKE_CACHE_ARTIFACT_ENDPOINT: ${{ vars.LAKE_CACHE_ENDPOINT }}/a1
-          LAKE_CACHE_REVISION_ENDPOINT: ${{ vars.LAKE_CACHE_ENDPOINT }}/r1
-        timeout-minutes: 20 # prevent excessive hanging from network issues
-        continue-on-error: true
       - name: Install
         run: |
           make -C build/$TARGET_STAGE install
@@ -276,10 +247,10 @@ jobs:
       - name: Check rebootstrap
         run: |
           set -e
-          git config user.email "stage0@lean-fro.org"
-          git config user.name "update-stage0"
+          # clean rebuild in case of Makefile changes/Lake does not detect uncommited stage 0
+          # changes yet
           make -C build update-stage0
-          git commit --allow-empty -m "chore: update-stage0"
+          make -C build/stage1 clean-stdlib
           time make -C build -j$NPROC
           time ctest --preset ${{ matrix.CMAKE_PRESET || 'release' }} --test-dir build/stage1 -j$NPROC
         if: matrix.check-rebootstrap

.github/workflows/check-empty-pr.yml

@@ -1,29 +0,0 @@
-name: Check for empty PR
-
-on:
-  merge_group:
-  pull_request:
-
-jobs:
-  check-empty-pr:
-    runs-on: ubuntu-latest
-    steps:
-    - uses: actions/checkout@v6
-      with:
-        ref: ${{ github.event_name == 'pull_request' && github.event.pull_request.head.sha || github.sha }}
-        fetch-depth: 0
-        filter: tree:0
-
-    - name: Check for empty diff
-      run: |
-        if [[ "${{ github.event_name }}" == "pull_request" ]]; then
-          base=$(git merge-base "origin/${{ github.base_ref }}" HEAD)
-        else
-          base=$(git rev-parse HEAD^1)
-        fi
-        if git diff --quiet "$base" HEAD --; then
-          echo "This PR introduces no changes compared to its base branch." | tee "$GITHUB_STEP_SUMMARY"
-          echo "It may be a duplicate of an already-merged PR." | tee -a "$GITHUB_STEP_SUMMARY"
-          exit 1
-        fi
-      shell: bash

.github/workflows/ci.yml

@@ -76,20 +76,9 @@ jobs:
               fi
               echo "nightly=$LEAN_VERSION_STRING" >> "$GITHUB_OUTPUT"
             else
-              # Scheduled: do nothing if commit already has a different tag (e.g. a release tag)
+              # Scheduled: do nothing if commit already has a different tag
               LEAN_VERSION_STRING="nightly-$(date -u +%F)"
-              HEAD_TAG="$(git name-rev --name-only --tags --no-undefined HEAD 2> /dev/null || true)"
-              if [[ -n "$HEAD_TAG" && "$HEAD_TAG" != "$LEAN_VERSION_STRING" ]]; then
-                echo "HEAD already tagged as ${HEAD_TAG}, skipping nightly"
-              elif git rev-parse "refs/tags/${LEAN_VERSION_STRING}" >/dev/null 2>&1; then
-                # Today's nightly already exists (e.g. from a manual release), create a revision
-                REV=1
-                while git rev-parse "refs/tags/${LEAN_VERSION_STRING}-rev${REV}" >/dev/null 2>&1; do
-                  REV=$((REV + 1))
-                done
-                LEAN_VERSION_STRING="${LEAN_VERSION_STRING}-rev${REV}"
-                echo "nightly=$LEAN_VERSION_STRING" >> "$GITHUB_OUTPUT"
-              else
+              if [[ "$(git name-rev --name-only --tags --no-undefined HEAD 2> /dev/null || echo "$LEAN_VERSION_STRING")" == "$LEAN_VERSION_STRING" ]]; then
                 echo "nightly=$LEAN_VERSION_STRING" >> "$GITHUB_OUTPUT"
               fi
             fi
@@ -143,7 +132,7 @@ jobs:
           CMAKE_MAJOR=$(grep -E "^set\(LEAN_VERSION_MAJOR " src/CMakeLists.txt | grep -oE '[0-9]+')
           CMAKE_MINOR=$(grep -E "^set\(LEAN_VERSION_MINOR " src/CMakeLists.txt | grep -oE '[0-9]+')
           CMAKE_PATCH=$(grep -E "^set\(LEAN_VERSION_PATCH " src/CMakeLists.txt | grep -oE '[0-9]+')
-          CMAKE_IS_RELEASE=$(grep -m 1 -E "^set\(LEAN_VERSION_IS_RELEASE " src/CMakeLists.txt | grep -oE '[0-9]+' | head -1)
+          CMAKE_IS_RELEASE=$(grep -m 1 -E "^set\(LEAN_VERSION_IS_RELEASE " src/CMakeLists.txt | sed -nE 's/^set\(LEAN_VERSION_IS_RELEASE ([0-9]+)\).*/\1/p')
 
           # Expected values from tag parsing
           TAG_MAJOR="${{ steps.set-release.outputs.LEAN_VERSION_MAJOR }}"
@@ -255,7 +244,7 @@ jobs:
                 // portable release build: use channel with older glibc (2.26)
                 "name": "Linux release",
                 // usually not a bottleneck so make exclusive to `fast-ci`
-                "os": large && fast ? "nscloud-ubuntu-24.04-amd64-8x16-with-cache" : "ubuntu-latest",
+                "os": large && fast ? "nscloud-ubuntu-22.04-amd64-8x16-with-cache" : "ubuntu-latest",
                 "release": true,
                 // Special handling for release jobs. We want:
                 // 1. To run it in PRs so developers get PR toolchains (so secondary without tests is sufficient)
@@ -276,7 +265,7 @@ jobs:
               },
               {
                 "name": "Linux Lake",
-                "os": large ? "nscloud-ubuntu-24.04-amd64-8x16-with-cache" : "ubuntu-latest",
+                "os": large ? "nscloud-ubuntu-22.04-amd64-8x16-with-cache" : "ubuntu-latest",
                 "enabled": true,
                 "check-rebootstrap": level >= 1,
                 "check-stage3": level >= 2,
@@ -284,19 +273,7 @@ jobs:
                 // NOTE: `test-bench` currently seems to be broken on `ubuntu-latest`
                 "test-bench": large && level >= 2,
                 // We are not warning-free yet on all platforms, start here
-                "CMAKE_OPTIONS": "-DLEAN_EXTRA_CXX_FLAGS=-Werror -DUSE_LAKE_CACHE=ON",
-              },
-              {
-                "name": "Linux Lake (Cached)",
-                "os": large ? "nscloud-ubuntu-24.04-amd64-8x16-with-cache" : "ubuntu-latest",
-                "enabled": true,
-                "check-rebootstrap": level >= 1,
-                "check-stage3": level >= 2,
-                "test": true,
-                "secondary": true,
-                // NOTE: `test-bench` currently seems to be broken on `ubuntu-latest`
-                "test-bench": large && level >= 2,
-                "CMAKE_OPTIONS": "-DLEAN_EXTRA_CXX_FLAGS=-Werror -DUSE_LAKE_CACHE=ON",
+                "CMAKE_OPTIONS": "-DLEAN_EXTRA_CXX_FLAGS=-Werror",
               },
               {
                 "name": "Linux Reldebug",
@@ -310,7 +287,7 @@ jobs:
               {
                 "name": "Linux fsanitize",
                 // Always run on large if available, more reliable regarding timeouts
-                "os": large ? "nscloud-ubuntu-24.04-amd64-16x32-with-cache" : "ubuntu-latest",
+                "os": large ? "nscloud-ubuntu-22.04-amd64-16x32-with-cache" : "ubuntu-latest",
                 "enabled": level >= 2,
                 // do not fail nightlies on this for now
                 "secondary": level <= 2,

.gitpod.yml

@@ -6,6 +6,6 @@ vscode:
     - leanprover.lean4
 
 tasks:
-  - name: Build
-    init: cmake --preset dev
+  - name: Release build
+    init: cmake --preset release
     command: make -C build/release -j$(nproc || sysctl -n hw.logicalcpu)

.vscode/tasks.json

@@ -11,15 +11,6 @@
 				"isDefault": true
 			}
 		},
-		{
-			"label": "build stage2",
-			"type": "shell",
-			"command": "make -C build/release stage2 -j$(nproc 2>/dev/null || sysctl -n hw.logicalcpu 2>/dev/null || echo 4)",
-			"problemMatcher": [],
-			"group": {
-				"kind": "build"
-			}
-		},
 		{
 			"label": "build-old",
 			"type": "shell",

CMakeLists.txt

@@ -1,6 +1,4 @@
 cmake_minimum_required(VERSION 3.21)
-include(ExternalProject)
-include(FetchContent)
 
 if(NOT CMAKE_GENERATOR MATCHES "Makefiles")
   message(FATAL_ERROR "Only makefile generators are supported")
@@ -36,6 +34,7 @@ foreach(var ${vars})
   endif()
 endforeach()
 
+include(ExternalProject)
 project(LEAN CXX C)
 
 if(NOT (DEFINED STAGE0_CMAKE_EXECUTABLE_SUFFIX))
@@ -120,17 +119,17 @@ if(NOT CMAKE_SYSTEM_NAME MATCHES "Emscripten")
 endif()
 
 if(USE_MIMALLOC)
-  FetchContent_Declare(
+  ExternalProject_Add(
     mimalloc
+    PREFIX mimalloc
     GIT_REPOSITORY https://github.com/microsoft/mimalloc
     GIT_TAG v2.2.3
-    # Unnecessarily deep directory structure, but it saves us from a complicated
-    # stage0 update for now. If we ever update the other dependencies like
-    # cadical, it might be worth reorganizing the directory structure.
-    SOURCE_DIR
-    "${CMAKE_BINARY_DIR}/mimalloc/src/mimalloc"
+    # just download, we compile it as part of each stage as it is small
+    CONFIGURE_COMMAND ""
+    BUILD_COMMAND ""
+    INSTALL_COMMAND ""
   )
-  FetchContent_MakeAvailable(mimalloc)
+  list(APPEND EXTRA_DEPENDS mimalloc)
 endif()
 
 if(NOT STAGE1_PREV_STAGE)

CMakePresets.json

@@ -8,26 +8,16 @@
   "configurePresets": [
     {
       "name": "release",
-      "displayName": "Release build config",
+      "displayName": "Default development optimized build config",
       "generator": "Unix Makefiles",
       "binaryDir": "${sourceDir}/build/release"
     },
-    {
-      "name": "dev",
-      "displayName": "Default development optimized build config",
-      "cacheVariables": {
-        "STRIP_BINARIES": "OFF"
-      },
-      "generator": "Unix Makefiles",
-      "binaryDir": "${sourceDir}/build/dev"
-    },
     {
       "name": "debug",
       "displayName": "Debug build config",
       "cacheVariables": {
-        "CMAKE_BUILD_TYPE": "Debug",
         "LEAN_EXTRA_CXX_FLAGS": "-DLEAN_DEFAULT_THREAD_STACK_SIZE=16*1024*1024",
-        "STRIP_BINARIES": "OFF"
+        "CMAKE_BUILD_TYPE": "Debug"
       },
       "generator": "Unix Makefiles",
       "binaryDir": "${sourceDir}/build/debug"
@@ -36,8 +26,7 @@
       "name": "reldebug",
       "displayName": "Release with assertions enabled",
       "cacheVariables": {
-        "CMAKE_BUILD_TYPE": "RelWithAssert",
-        "STRIP_BINARIES": "OFF"
+        "CMAKE_BUILD_TYPE": "RelWithAssert"
       },
       "generator": "Unix Makefiles",
       "binaryDir": "${sourceDir}/build/reldebug"
@@ -49,7 +38,6 @@
         "LEAN_EXTRA_CXX_FLAGS": "-fsanitize=address,undefined -DLEAN_DEFAULT_THREAD_STACK_SIZE=16*1024*1024",
         "LEANC_EXTRA_CC_FLAGS": "-fsanitize=address,undefined",
         "LEAN_EXTRA_LINKER_FLAGS": "-fsanitize=address,undefined -fsanitize-link-c++-runtime",
-        "STRIP_BINARIES": "OFF",
         "SMALL_ALLOCATOR": "OFF",
         "USE_MIMALLOC": "OFF",
         "BSYMBOLIC": "OFF",
@@ -70,10 +58,6 @@
       "name": "release",
       "configurePreset": "release"
     },
-    {
-      "name": "dev",
-      "configurePreset": "dev"
-    },
     {
       "name": "debug",
       "configurePreset": "debug"
@@ -97,11 +81,6 @@
       "configurePreset": "release",
       "output": {"outputOnFailure": true, "shortProgress": true}
     },
-    {
-      "name": "dev",
-      "configurePreset": "dev",
-      "output": {"outputOnFailure": true, "shortProgress": true}
-    },
     {
       "name": "debug",
       "configurePreset": "debug",

doc/make/index.md

@@ -30,9 +30,6 @@ cd lean4
 cmake --preset release
 make -C build/release -j$(nproc || sysctl -n hw.logicalcpu)
 ```
-
-For development, `cmake --preset dev` is recommended instead.
-
 You can replace `$(nproc || sysctl -n hw.logicalcpu)` with the desired parallelism amount.
 
 The above commands will compile the Lean library and binaries into the

script/release_checklist.py

@@ -236,7 +236,7 @@ def parse_version(version_str):
 def is_version_gte(version1, version2):
     """Check if version1 >= version2, including proper handling of release candidates."""
     # Check if version1 is a nightly toolchain
-    if version1.startswith("leanprover/lean4:nightly-") or version1.startswith("leanprover/lean4-nightly:"):
+    if version1.startswith("leanprover/lean4:nightly-"):
         return False
     return parse_version(version1) >= parse_version(version2)
 
@@ -311,16 +311,16 @@ def check_cmake_version(repo_url, branch, version_major, version_minor, github_t
         print(f"  ❌ Could not retrieve {cmake_file_path} from {branch}")
         return False
 
-    expected_patterns = [
-        (f"LEAN_VERSION_MAJOR", rf"^set\(LEAN_VERSION_MAJOR\s+{version_major}[\s)]", f"set(LEAN_VERSION_MAJOR {version_major} ...)"),
-        (f"LEAN_VERSION_MINOR", rf"^set\(LEAN_VERSION_MINOR\s+{version_minor}[\s)]", f"set(LEAN_VERSION_MINOR {version_minor} ...)"),
-        (f"LEAN_VERSION_PATCH", rf"^set\(LEAN_VERSION_PATCH\s+0[\s)]", f"set(LEAN_VERSION_PATCH 0 ...)"),
-        (f"LEAN_VERSION_IS_RELEASE", rf"^set\(LEAN_VERSION_IS_RELEASE\s+1[\s)]", f"set(LEAN_VERSION_IS_RELEASE 1 ...)"),
+    expected_lines = [
+        f"set(LEAN_VERSION_MAJOR {version_major})",
+        f"set(LEAN_VERSION_MINOR {version_minor})",
+        f"set(LEAN_VERSION_PATCH 0)",
+        f"set(LEAN_VERSION_IS_RELEASE 1)"
     ]
 
-    for name, pattern, display in expected_patterns:
-        if not any(re.match(pattern, l.strip()) for l in content.splitlines()):
-            print(f"  ❌ Missing or incorrect line in {cmake_file_path}: {display}")
+    for line in expected_lines:
+        if not any(l.strip().startswith(line) for l in content.splitlines()):
+            print(f"  ❌ Missing or incorrect line in {cmake_file_path}: {line}")
             return False
 
     print(f"  ✅ CMake version settings are correct in {cmake_file_path}")
@@ -343,11 +343,11 @@ def check_stage0_version(repo_url, branch, version_major, version_minor, github_
     for line in content.splitlines():
         stripped = line.strip()
         if stripped.startswith("set(LEAN_VERSION_MAJOR "):
-            actual = stripped.split()[1].rstrip(")")
+            actual = stripped.split()[-1].rstrip(")")
             if actual != str(version_major):
                 errors.append(f"LEAN_VERSION_MAJOR: expected {version_major}, found {actual}")
         elif stripped.startswith("set(LEAN_VERSION_MINOR "):
-            actual = stripped.split()[1].rstrip(")")
+            actual = stripped.split()[-1].rstrip(")")
             if actual != str(version_minor):
                 errors.append(f"LEAN_VERSION_MINOR: expected {version_minor}, found {actual}")
 

script/release_repos.yml

@@ -14,6 +14,13 @@ repositories:
     bump-branch: true
     dependencies: []
 
+  - name: lean4checker
+    url: https://github.com/leanprover/lean4checker
+    toolchain-tag: true
+    stable-branch: true
+    branch: master
+    dependencies: []
+
   - name: quote4
     url: https://github.com/leanprover-community/quote4
     toolchain-tag: true

src/CMakeLists.txt

@@ -8,7 +8,7 @@ endif()
 include(ExternalProject)
 project(LEAN CXX C)
 set(LEAN_VERSION_MAJOR 4 CACHE STRING "")
-set(LEAN_VERSION_MINOR 31 CACHE STRING "")
+set(LEAN_VERSION_MINOR 30 CACHE STRING "")
 set(LEAN_VERSION_PATCH 0 CACHE STRING "")
 set(LEAN_VERSION_IS_RELEASE 0 CACHE STRING "") # 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'")
@@ -80,7 +80,6 @@ option(CCACHE "use ccache" ON)
 option(SPLIT_STACK "SPLIT_STACK" OFF)
 # When OFF we disable LLVM support
 option(LLVM "LLVM" OFF)
-option(STRIP_BINARIES "Strip produced binaries" ON)
 
 # When ON we include githash in the version string
 option(USE_GITHASH "GIT_HASH" ON)
@@ -615,38 +614,6 @@ else()
       OUTPUT_VARIABLE GIT_SHA1
       OUTPUT_STRIP_TRAILING_WHITESPACE
     )
-    # Fallback for jj workspaces where git cannot find .git directly.
-    # Use `jj git root` to find the backing git repo, then `jj log` to
-    # resolve the current workspace's commit (git HEAD points to the root
-    # workspace, not the current one).
-    if("${GIT_SHA1}" STREQUAL "")
-      find_program(JJ_EXECUTABLE jj)
-      if(JJ_EXECUTABLE)
-        execute_process(
-          COMMAND "${JJ_EXECUTABLE}" git root
-          WORKING_DIRECTORY "${CMAKE_CURRENT_SOURCE_DIR}"
-          OUTPUT_VARIABLE _jj_git_dir
-          OUTPUT_STRIP_TRAILING_WHITESPACE
-          ERROR_QUIET
-          RESULT_VARIABLE _jj_git_root_result
-        )
-        execute_process(
-          COMMAND "${JJ_EXECUTABLE}" log -r @ --no-graph -T "commit_id"
-          WORKING_DIRECTORY "${CMAKE_CURRENT_SOURCE_DIR}"
-          OUTPUT_VARIABLE _jj_commit
-          OUTPUT_STRIP_TRAILING_WHITESPACE
-          ERROR_QUIET
-          RESULT_VARIABLE _jj_rev_result
-        )
-        if(_jj_git_root_result EQUAL 0 AND _jj_rev_result EQUAL 0)
-          execute_process(
-            COMMAND git --git-dir "${_jj_git_dir}" ls-tree "${_jj_commit}" stage0 --object-only
-            OUTPUT_VARIABLE GIT_SHA1
-            OUTPUT_STRIP_TRAILING_WHITESPACE
-          )
-        endif()
-      endif()
-    endif()
     message(STATUS "stage0 sha1: ${GIT_SHA1}")
     # Now that we've prepared the information for the next stage, we can forget that we will use
     # Lake in the future as we won't use it in this stage
@@ -830,14 +797,7 @@ if(LLVM AND STAGE GREATER 0)
   set(EXTRA_LEANMAKE_OPTS "LLVM=1")
 endif()
 
-set(
-  STDLIBS
-  Init
-  Std
-  Lean
-  Leanc
-  LeanIR
-)
+set(STDLIBS Init Std Lean Leanc LeanIR)
 if(NOT CMAKE_SYSTEM_NAME MATCHES "Emscripten")
   list(APPEND STDLIBS Lake LeanChecker)
 endif()
@@ -945,7 +905,10 @@ if(PREV_STAGE)
 endif()
 
 if(NOT CMAKE_SYSTEM_NAME MATCHES "Emscripten")
-  add_custom_target(leanir ALL DEPENDS leanshared COMMAND $(MAKE) -f ${CMAKE_BINARY_DIR}/stdlib.make leanir VERBATIM)
+  add_custom_target(leanir ALL
+    DEPENDS leanshared
+    COMMAND $(MAKE) -f ${CMAKE_BINARY_DIR}/stdlib.make leanir
+    VERBATIM)
 endif()
 
 # use Bash version for building, use Lean version in bin/ for tests & distribution

src/Init/Control/ExceptCps.lean

@@ -37,7 +37,7 @@ set_option linter.unusedVariables false in  -- `s` unused
 Use a monadic action that may throw an exception by providing explicit success and failure
 continuations.
 -/
-@[always_inline, inline, expose]
+@[always_inline, inline]
 def runK {ε α : Type u} (x : ExceptCpsT ε m α) (s : ε) (ok : α → m β) (error : ε → m β) : m β :=
   x _ ok error
 
@@ -83,8 +83,6 @@ of `True`.
 -/
 instance : MonadAttach (ExceptCpsT ε m) := .trivial
 
-@[simp] theorem throw_bind [Monad m] (e : ε) (f : α → ExceptCpsT ε m β) : (throw e >>= f : ExceptCpsT ε m β) = throw e := rfl
-
 @[simp] theorem run_pure [Monad m] : run (pure x : ExceptCpsT ε m α) = pure (Except.ok x) := rfl
 
 @[simp] theorem run_lift {α ε : Type u} [Monad m] (x : m α) : run (ExceptCpsT.lift x : ExceptCpsT ε m α) = (x >>= fun a => pure (Except.ok a) : m (Except ε α)) := rfl
@@ -93,20 +91,7 @@ instance : MonadAttach (ExceptCpsT ε m) := .trivial
 
 @[simp] theorem run_bind_lift [Monad m] (x : m α) (f : α → ExceptCpsT ε m β) : run (ExceptCpsT.lift x >>= f : ExceptCpsT ε m β) = x >>= fun a => run (f a) := rfl
 
-@[deprecated throw_bind (since := "2026-03-13")]
-theorem run_bind_throw [Monad m] (e : ε) (f : α → ExceptCpsT ε m β) : run (throw e >>= f : ExceptCpsT ε m β) = run (throw e) := rfl
-
-@[simp] theorem runK_pure :
-    runK (pure x : ExceptCpsT ε m α) s ok error = ok x := rfl
-
-@[simp] theorem runK_lift {α ε : Type u} [Monad m] (x : m α) (s : ε) (ok : α → m β) (error : ε → m β) :
-    runK (ExceptCpsT.lift x : ExceptCpsT ε m α) s ok error = x >>= ok := rfl
-
-@[simp] theorem runK_throw [Monad m] :
-    runK (throw e : ExceptCpsT ε m β) s ok error = error e := rfl
-
-@[simp] theorem runK_bind_lift [Monad m] (x : m α) (f : α → ExceptCpsT ε m β) :
-    runK (ExceptCpsT.lift x >>= f : ExceptCpsT ε m β) s ok error = x >>= fun a => runK (f a) s ok error := rfl
+@[simp] theorem run_bind_throw [Monad m] (e : ε) (f : α → ExceptCpsT ε m β) : run (throw e >>= f : ExceptCpsT ε m β) = run (throw e) := rfl
 
 @[simp] theorem runCatch_pure [Monad m] : runCatch (pure x : ExceptCpsT α m α) = pure x := rfl
 
@@ -117,7 +102,6 @@ theorem run_bind_throw [Monad m] (e : ε) (f : α → ExceptCpsT ε m β) : run
 
 @[simp] theorem runCatch_bind_lift [Monad m] (x : m α) (f : α → ExceptCpsT β m β) : runCatch (ExceptCpsT.lift x >>= f : ExceptCpsT β m β) = x >>= fun a => runCatch (f a) := rfl
 
-@[deprecated throw_bind (since := "2026-03-13")]
-theorem runCatch_bind_throw [Monad m] (e : β) (f : α → ExceptCpsT β m β) : runCatch (throw e >>= f : ExceptCpsT β m β) = pure e := rfl
+@[simp] theorem runCatch_bind_throw [Monad m] (e : β) (f : α → ExceptCpsT β m β) : runCatch (throw e >>= f : ExceptCpsT β m β) = pure e := rfl
 
 end ExceptCpsT

src/Init/Data/Array/MinMax.lean

@@ -113,7 +113,7 @@ public theorem _root_.List.min?_toArray [Min α] {l : List α} :
   · simp [List.min_toArray, List.min_eq_get_min?, - List.get_min?]
   · simp_all
 
-@[simp, grind =, cbv_eval ←]
+@[simp, grind =]
 public theorem min?_toList [Min α] {xs : Array α} :
     xs.toList.min? = xs.min? := by
   cases xs; simp
@@ -153,7 +153,7 @@ public theorem _root_.List.max?_toArray [Max α] {l : List α} :
   · simp [List.max_toArray, List.max_eq_get_max?, - List.get_max?]
   · simp_all
 
-@[simp, grind =, cbv_eval ←]
+@[simp, grind =]
 public theorem max?_toList [Max α] {xs : Array α} :
     xs.toList.max? = xs.max? := by
   cases xs; simp

src/Init/Data/BEq.lean

@@ -66,8 +66,3 @@ theorem BEq.neq_of_beq_of_neq [BEq α] [PartialEquivBEq α] {a b c : α} :
 instance (priority := low) [BEq α] [LawfulBEq α] : EquivBEq α where
   symm h := beq_iff_eq.2 <| Eq.symm <| beq_iff_eq.1 h
   trans hab hbc := beq_iff_eq.2 <| (beq_iff_eq.1 hab).trans <| beq_iff_eq.1 hbc
-
-theorem equivBEq_of_iff_apply_eq [BEq α] (f : α → β) (hf : ∀ a b, a == b ↔ f a = f b) : EquivBEq α where
-  rfl := by simp [hf]
-  symm := by simp [hf, eq_comm]
-  trans hab hbc := (hf _ _).2 (Eq.trans ((hf _ _).1 hab) ((hf _ _).1 hbc))

src/Init/Data/ByteArray/Basic.lean

@@ -20,20 +20,12 @@ universe u
 
 namespace ByteArray
 
-@[extern "lean_sarray_dec_eq"]
-def beq (lhs rhs : @& ByteArray) : Bool :=
-  lhs.data == rhs.data
-
-instance : BEq ByteArray where
-  beq := beq
+deriving instance BEq for ByteArray
 
 attribute [ext] ByteArray
 
-@[extern "lean_sarray_dec_eq"]
-def decEq (lhs rhs : @& ByteArray) : Decidable (lhs = rhs) :=
-  decidable_of_decidable_of_iff ByteArray.ext_iff.symm
-
-instance : DecidableEq ByteArray := decEq
+instance : DecidableEq ByteArray :=
+  fun _ _ => decidable_of_decidable_of_iff ByteArray.ext_iff.symm
 
 instance : Inhabited ByteArray where
   default := empty

src/Init/Data/Char/Lemmas.lean

@@ -98,8 +98,4 @@ theorem toNat_inj {c d : Char} : c.toNat = d.toNat ↔ c = d := by
 theorem isDigit_iff_toNat {c : Char} : c.isDigit ↔ '0'.toNat ≤ c.toNat ∧ c.toNat ≤ '9'.toNat := by
   simp [isDigit, UInt32.le_iff_toNat_le]
 
-@[simp]
-theorem toNat_mk {val : UInt32} {h} : (Char.mk val h).toNat = val.toNat := by
-  simp [← toNat_val]
-
 end Char

src/Init/Data/Fin/Lemmas.lean

@@ -527,14 +527,6 @@ theorem castLE_of_eq {m n : Nat} (h : m = n) {h' : m ≤ n} : castLE h' = Fin.ca
 
 @[simp, grind =] theorem val_castAdd (m : Nat) (i : Fin n) : (castAdd m i : Nat) = i := rfl
 
-/-
-**Note**
-The current pattern inference heuristic includes the implicit term `n + m` as pattern of the pattern,
-but arithmetic is problematic in patterns because it is an interpreted symbol. For example,
-we will fail to match `@val n (castNat 0 i)`. Thus, we mark the implicit subterm with `no_index`
--/
-grind_pattern val_castAdd => @val (no_index _) (castAdd m i)
-
 @[deprecated val_castAdd (since := "2025-11-21")]
 theorem coe_castAdd (m : Nat) (i : Fin n) : (castAdd m i : Nat) = i := rfl
 
@@ -645,15 +637,7 @@ theorem exists_castSucc_eq {n : Nat} {i : Fin (n + 1)} : (∃ j, castSucc j = i)
 
 theorem succ_castSucc {n : Nat} (i : Fin n) : i.castSucc.succ = i.succ.castSucc := rfl
 
-@[simp] theorem val_addNat (m : Nat) (i : Fin n) : (addNat i m : Nat) = i + m := rfl
-
-/-
-**Note**
-The current pattern inference heuristic includes the implicit term `n + m` as pattern of the pattern,
-but arithmetic is problematic in patterns because it is an interpreted symbol. For example,
-we will fail to match `@val n (addNat i 0)`. Thus, we mark the implicit subterm with `no_index`
--/
-grind_pattern val_addNat => @val (no_index _) (addNat i m)
+@[simp, grind =] theorem val_addNat (m : Nat) (i : Fin n) : (addNat i m : Nat) = i + m := rfl
 
 @[deprecated val_addNat (since := "2025-11-21")]
 theorem coe_addNat (m : Nat) (i : Fin n) : (addNat i m : Nat) = i + m := rfl

src/Init/Data/Iterators/Consumers/Collect.lean

@@ -66,7 +66,7 @@ lists are prepend-only, this `toListRev` is usually more efficient that `toList`
 If the iterator is not finite, this function might run forever. The variant
 `it.ensureTermination.toListRev` always terminates after finitely many steps.
 -/
-@[always_inline, inline, cbv_opaque]
+@[always_inline, inline]
 def Iter.toListRev {α : Type w} {β : Type w}
     [Iterator α Id β] (it : Iter (α := α) β) : List β :=
   it.toIterM.toListRev.run

src/Init/Data/Iterators/Consumers/Loop.lean

@@ -226,7 +226,7 @@ any element emitted by the iterator {name}`it`.
 {lit}`O(|xs|)`. Short-circuits upon encountering the first match. The elements in {name}`it` are
 examined in order of iteration.
 -/
-@[inline, cbv_opaque]
+@[inline]
 def Iter.any {α β : Type w}
     [Iterator α Id β] [IteratorLoop α Id Id]
     (p : β → Bool) (it : Iter (α := α) β) : Bool :=
@@ -292,7 +292,7 @@ all element emitted by the iterator {name}`it`.
 {lit}`O(|xs|)`. Short-circuits upon encountering the first match. The elements in {name}`it` are
 examined in order of iteration.
 -/
-@[inline, cbv_opaque]
+@[inline]
 def Iter.all {α β : Type w}
     [Iterator α Id β] [IteratorLoop α Id Id]
     (p : β → Bool) (it : Iter (α := α) β) : Bool :=
@@ -644,7 +644,7 @@ Examples:
 * `[7, 6].iter.first? = some 7`
 * `[].iter.first? = none`
 -/
-@[inline, cbv_opaque]
+@[inline]
 def Iter.first? {α β : Type w} [Iterator α Id β] [IteratorLoop α Id Id]
     (it : Iter (α := α) β) : Option β :=
   it.toIterM.first?.run

src/Init/Data/Iterators/Lemmas/Consumers/Collect.lean

@@ -110,7 +110,6 @@ theorem Iter.reverse_toListRev_ensureTermination [Iterator α Id β] [Finite α
     it.ensureTermination.toListRev.reverse = it.toList := by
   simp
 
-@[cbv_eval]
 theorem Iter.toListRev_eq {α β} [Iterator α Id β] [Finite α Id]
     {it : Iter (α := α) β} :
     it.toListRev = it.toList.reverse := by

src/Init/Data/Iterators/Lemmas/Consumers/Loop.lean

@@ -637,7 +637,6 @@ theorem Iter.any_eq_forIn {α β : Type w} [Iterator α Id β]
           return .yield false)).run := by
   simp [any_eq_anyM, anyM_eq_forIn]
 
-@[cbv_eval ←]
 theorem Iter.any_toList {α β : Type w} [Iterator α Id β]
     [Finite α Id] [IteratorLoop α Id Id] [LawfulIteratorLoop α Id Id]
     {it : Iter (α := α) β} {p : β → Bool} :
@@ -728,7 +727,6 @@ theorem Iter.all_eq_forIn {α β : Type w} [Iterator α Id β]
           return .done false)).run := by
   simp [all_eq_allM, allM_eq_forIn]
 
-@[cbv_eval ←]
 theorem Iter.all_toList {α β : Type w} [Iterator α Id β]
     [Finite α Id] [IteratorLoop α Id Id] [LawfulIteratorLoop α Id Id]
     {it : Iter (α := α) β} {p : β → Bool} :
@@ -956,7 +954,7 @@ theorem Iter.first?_eq_match_step {α β : Type w} [Iterator α Id β] [Iterator
   generalize it.toIterM.step.run.inflate = s
   rcases s with ⟨_|_|_, _⟩ <;> simp [Iter.first?_eq_first?_toIterM]
 
-@[simp, grind =, cbv_eval ←]
+@[simp, grind =]
 theorem Iter.head?_toList {α β : Type w} [Iterator α Id β] [IteratorLoop α Id Id]
     [Finite α Id] [LawfulIteratorLoop α Id Id] {it : Iter (α := α) β} :
     it.toList.head? = it.first? := by

src/Init/Data/Nat/ToString.lean

@@ -298,7 +298,7 @@ theorem ofDigitChars_cons {c : Char} {cs : List Char} {init : Nat} :
   simp [ofDigitChars]
 
 theorem ofDigitChars_cons_digitChar_of_lt_ten {n : Nat} (hn : n < 10) {cs : List Char} {init : Nat} :
-    ofDigitChars b (n.digitChar :: cs) init = ofDigitChars b cs (b * init + n) := by
+    ofDigitChars 10 (n.digitChar :: cs) init = ofDigitChars 10 cs (10 * init + n) := by
   simp [ofDigitChars_cons, Nat.toNat_digitChar_sub_48_of_lt_ten hn]
 
 theorem ofDigitChars_eq_ofDigitChars_zero {l : List Char} {init : Nat} :
@@ -320,17 +320,15 @@ theorem ofDigitChars_replicate_zero {n : Nat} : ofDigitChars b (List.replicate n
   | zero => simp
   | succ n ih => simp [List.replicate_succ, ofDigitChars_cons, ih, Nat.pow_succ, Nat.mul_assoc]
 
-theorem ofDigitChars_toDigits {b n : Nat} (hb' : 1 < b) (hb : b ≤ 10) : ofDigitChars b (toDigits b n) 0 = n := by
-  induction n using base_induction b hb' with
-  | single m hm =>
-    simp [Nat.toDigits_of_lt_base hm, ofDigitChars_cons_digitChar_of_lt_ten (by omega : m < 10)]
-  | digit m k hk hm ih =>
-    rw [← Nat.toDigits_append_toDigits hb' hm hk,
-      ofDigitChars_append, ih, Nat.toDigits_of_lt_base hk,
-      ofDigitChars_cons_digitChar_of_lt_ten (Nat.lt_of_lt_of_le hk hb), ofDigitChars_nil]
-
 @[simp]
-theorem ofDigitChars_ten_toDigits {n : Nat} : ofDigitChars 10 (toDigits 10 n) 0 = n :=
-  ofDigitChars_toDigits (by decide) (by decide)
+theorem ofDigitChars_toDigits {n : Nat} : ofDigitChars 10 (toDigits 10 n) 0 = n := by
+  have : 1 < 10 := by decide
+  induction n using base_induction 10 this with
+  | single m hm =>
+    simp [Nat.toDigits_of_lt_base hm, ofDigitChars_cons_digitChar_of_lt_ten hm]
+  | digit m k hk hm ih =>
+    rw [← Nat.toDigits_append_toDigits this hm hk,
+      ofDigitChars_append, ih, Nat.toDigits_of_lt_base hk,
+      ofDigitChars_cons_digitChar_of_lt_ten hk, ofDigitChars_nil]
 
 end Nat

src/Init/Data/Ord/String.lean

@@ -9,7 +9,7 @@ prelude
 public import Init.Data.Order.Ord
 public import Init.Data.String.Basic
 import Init.Data.Char.Lemmas
-import Init.Data.String.Lemmas.StringOrder
+import Init.Data.String.Lemmas
 
 public section
 

src/Init/Data/Order/Lemmas.lean

@@ -243,10 +243,6 @@ public theorem lt_iff_le_and_ne [LE α] [LT α] [LawfulOrderLT α] [IsPartialOrd
     a < b ↔ a ≤ b ∧ a ≠ b := by
   simpa [le_iff_lt_or_eq, or_and_right] using Std.ne_of_lt
 
-public theorem lt_trichotomy [LT α] [Std.Trichotomous (α := α) (· < ·)] (a b : α) :
-    a < b ∨ a = b ∨ b < a :=
-  Trichotomous.rel_or_eq_or_rel_swap
-
 end LT
 end Std
 

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

@@ -193,7 +193,6 @@ public theorem Array.toSubarray_eq_toSubarray_of_min_eq_min {xs : Array α}
         simp [*]; omega
       · simp
 
-@[cbv_eval]
 public theorem Array.toSubarray_eq_min {xs : Array α} {lo hi : Nat} :
     xs.toSubarray lo hi = ⟨⟨xs, min lo (min hi xs.size), min hi xs.size, Nat.min_le_right _ _,
       Nat.min_le_right _ _⟩⟩ := by

src/Init/Data/String/Basic.lean

@@ -852,10 +852,6 @@ theorem Slice.rawEndPos_copy {s : Slice} : s.copy.rawEndPos = s.rawEndPos := by
 theorem copy_toSlice {s : String} : s.toSlice.copy = s := by
   simp [← toByteArray_inj, Slice.toByteArray_copy, ← size_toByteArray]
 
-@[simp]
-theorem copy_comp_toSlice : String.Slice.copy ∘ String.toSlice = id := by
-  ext; simp
-
 theorem Slice.getUTF8Byte_eq_getUTF8Byte_copy {s : Slice} {p : Pos.Raw} {h : p < s.rawEndPos} :
     s.getUTF8Byte p h = s.copy.getUTF8Byte p (by simpa) := by
   simp [getUTF8Byte, String.getUTF8Byte, toByteArray_copy, ByteArray.getElem_extract]
@@ -1386,11 +1382,6 @@ theorem Slice.copy_eq_copy_sliceTo {s : Slice} {pos : s.Pos} :
   rw [Nat.max_eq_right]
   exact pos.offset_str_le_offset_endExclusive
 
-@[simp]
-theorem Slice.sliceTo_append_sliceFrom {s : Slice} {pos : s.Pos} :
-    (s.sliceTo pos).copy ++ (s.sliceFrom pos).copy = s.copy :=
-  copy_eq_copy_sliceTo.symm
-
 /-- Given a slice `s` and a position on `s.copy`, obtain the corresponding position on `s`. -/
 @[inline]
 def Pos.ofCopy {s : Slice} (pos : s.copy.Pos) : s.Pos where
@@ -1750,31 +1741,6 @@ theorem Slice.Pos.offset_cast {s t : Slice} {pos : s.Pos} {h : s.copy = t.copy}
 theorem Slice.Pos.cast_rfl {s : Slice} {pos : s.Pos} : pos.cast rfl = pos :=
   Slice.Pos.ext (by simp)
 
-@[simp]
-theorem Slice.Pos.cast_cast {s t u : Slice} {hst : s.copy = t.copy} {htu : t.copy = u.copy}
-    {pos : s.Pos} : (pos.cast hst).cast htu = pos.cast (hst.trans htu) :=
-  Slice.Pos.ext (by simp)
-
-@[simp]
-theorem Slice.Pos.cast_inj {s t : Slice} {hst : s.copy = t.copy} {p q : s.Pos} : p.cast hst = q.cast hst ↔ p = q := by
-  simp [Slice.Pos.ext_iff]
-
-@[simp]
-theorem Slice.Pos.cast_startPos {s t : Slice} {hst : s.copy = t.copy} : s.startPos.cast hst = t.startPos :=
-  Slice.Pos.ext (by simp)
-
-@[simp]
-theorem Slice.Pos.cast_eq_startPos {s t : Slice} {p : s.Pos} {hst : s.copy = t.copy} : p.cast hst = t.startPos ↔ p = s.startPos := by
-  rw [← cast_startPos (hst := hst), Pos.cast_inj]
-
-@[simp]
-theorem Slice.Pos.cast_endPos {s t : Slice} {hst : s.copy = t.copy} : s.endPos.cast hst = t.endPos :=
-  Slice.Pos.ext (by simp [← rawEndPos_copy, hst])
-
-@[simp]
-theorem Slice.Pos.cast_eq_endPos {s t : Slice} {p : s.Pos} {hst : s.copy = t.copy} : p.cast hst = t.endPos ↔ p = s.endPos := by
-  rw [← cast_endPos (hst := hst), Pos.cast_inj]
-
 @[simp]
 theorem Slice.Pos.cast_le_cast_iff {s t : Slice} {pos pos' : s.Pos} {h : s.copy = t.copy} :
     pos.cast h ≤ pos'.cast h ↔ pos ≤ pos' := by
@@ -1785,22 +1751,6 @@ theorem Slice.Pos.cast_lt_cast_iff {s t : Slice} {pos pos' : s.Pos} {h : s.copy
     pos.cast h < pos'.cast h ↔ pos < pos' := by
   simp [Slice.Pos.lt_iff]
 
-theorem Slice.Pos.cast_le_iff {s t : Slice} {pos : s.Pos} {pos' : t.Pos} {h : s.copy = t.copy} :
-    pos.cast h ≤ pos' ↔ pos ≤ pos'.cast h.symm := by
-  simp [Slice.Pos.le_iff]
-
-theorem Slice.Pos.le_cast_iff {s t : Slice} {pos : t.Pos} {pos' : s.Pos} {h : s.copy = t.copy} :
-    pos ≤ pos'.cast h ↔ pos.cast h.symm ≤ pos' := by
-  simp [Slice.Pos.le_iff]
-
-theorem Slice.Pos.cast_lt_iff {s t : Slice} {pos : s.Pos} {pos' : t.Pos} {h : s.copy = t.copy} :
-    pos.cast h < pos' ↔ pos < pos'.cast h.symm := by
-  simp [Slice.Pos.lt_iff]
-
-theorem Slice.Pos.lt_cast_iff {s t : Slice} {pos : t.Pos} {pos' : s.Pos} {h : s.copy = t.copy} :
-    pos < pos'.cast h ↔ pos.cast h.symm < pos' := by
-  simp [Slice.Pos.lt_iff]
-
 /-- Constructs a valid position on `t` from a valid position on `s` and a proof that `s = t`. -/
 @[inline]
 def Pos.cast {s t : String} (pos : s.Pos) (h : s = t) : t.Pos where
@@ -1815,31 +1765,6 @@ theorem Pos.offset_cast {s t : String} {pos : s.Pos} {h : s = t} :
 theorem Pos.cast_rfl {s : String} {pos : s.Pos} : pos.cast rfl = pos :=
   Pos.ext (by simp)
 
-@[simp]
-theorem Pos.cast_cast {s t u : String} {hst : s = t} {htu : t = u}
-    {pos : s.Pos} : (pos.cast hst).cast htu = pos.cast (hst.trans htu) :=
-  Pos.ext (by simp)
-
-@[simp]
-theorem Pos.cast_inj {s t : String} {hst : s = t} {p q : s.Pos} : p.cast hst = q.cast hst ↔ p = q := by
-  simp [Pos.ext_iff]
-
-@[simp]
-theorem Pos.cast_startPos {s t : String} {hst : s = t} : s.startPos.cast hst = t.startPos := by
-  subst hst; simp
-
-@[simp]
-theorem Pos.cast_eq_startPos {s t : String} {hst : s = t} {p : s.Pos} : p.cast hst = t.startPos ↔ p = s.startPos := by
-  rw [← Pos.cast_startPos (hst := hst), Pos.cast_inj]
-
-@[simp]
-theorem Pos.cast_endPos {s t : String} {hst : s = t} : s.endPos.cast hst = t.endPos := by
-  subst hst; simp
-
-@[simp]
-theorem Pos.cast_eq_endPos {s t : String} {hst : s = t} {p : s.Pos} : p.cast hst = t.endPos ↔ p = s.endPos := by
-  rw [← Pos.cast_endPos (hst := hst), Pos.cast_inj]
-
 @[simp]
 theorem Pos.cast_le_cast_iff {s t : String} {pos pos' : s.Pos} {h : s = t} :
     pos.cast h ≤ pos'.cast h ↔ pos ≤ pos' := by
@@ -1850,22 +1775,6 @@ theorem Pos.cast_lt_cast_iff {s t : String} {pos pos' : s.Pos} {h : s = t} :
     pos.cast h < pos'.cast h ↔ pos < pos' := by
   cases h; simp
 
-theorem Pos.cast_le_iff {s t : String} {pos : s.Pos} {pos' : t.Pos} {h : s = t} :
-    pos.cast h ≤ pos' ↔ pos ≤ pos'.cast h.symm := by
-  simp [Pos.le_iff]
-
-theorem Pos.le_cast_iff {s t : String} {pos : t.Pos} {pos' : s.Pos} {h : s = t} :
-    pos ≤ pos'.cast h ↔ pos.cast h.symm ≤ pos' := by
-  simp [Pos.le_iff]
-
-theorem Pos.cast_lt_iff {s t : String} {pos : s.Pos} {pos' : t.Pos} {h : s = t} :
-    pos.cast h < pos' ↔ pos < pos'.cast h.symm := by
-  simp [Pos.lt_iff]
-
-theorem Pos.lt_cast_iff {s t : String} {pos : t.Pos} {pos' : s.Pos} {h : s = t} :
-    pos < pos'.cast h ↔ pos.cast h.symm < pos' := by
-  simp [Pos.lt_iff]
-
 theorem Pos.copy_toSlice_eq_cast {s : String} (p : s.Pos) :
     p.toSlice.copy = p.cast copy_toSlice.symm :=
   Pos.ext (by simp)
@@ -2141,10 +2050,6 @@ theorem Pos.le_ofToSlice_iff {s : String} {p : s.Pos} {q : s.toSlice.Pos} :
 theorem Pos.toSlice_lt_toSlice_iff {s : String} {p q : s.Pos} :
     p.toSlice < q.toSlice ↔ p < q := Iff.rfl
 
-@[simp]
-theorem Pos.toSlice_le_toSlice_iff {s : String} {p q : s.Pos} :
-    p.toSlice ≤ q.toSlice ↔ p ≤ q := Iff.rfl
-
 theorem Pos.next_le_of_lt {s : String} {p q : s.Pos} {h} : p < q → p.next h ≤ q := by
   rw [next, Pos.ofToSlice_le_iff, ← Pos.toSlice_lt_toSlice_iff]
   exact Slice.Pos.next_le_of_lt

src/Init/Data/String/Defs.lean

@@ -187,9 +187,6 @@ theorem append_right_inj (s : String) {t₁ t₂ : String} :
 theorem append_assoc {s₁ s₂ s₃ : String} : s₁ ++ s₂ ++ s₃ = s₁ ++ (s₂ ++ s₃) := by
   simp [← toByteArray_inj, ByteArray.append_assoc]
 
-instance : Std.Associative (α := String) (· ++ ·) where
-  assoc _ _ _ := append_assoc
-
 @[simp]
 theorem utf8ByteSize_eq_zero_iff {s : String} : s.utf8ByteSize = 0 ↔ s = "" := by
   refine ⟨fun h => ?_, fun h => h ▸ utf8ByteSize_empty⟩

src/Init/Data/String/Iter.lean

@@ -6,5 +6,29 @@ Authors: Markus Himmel
 module
 
 prelude
-public import Init.Data.String.Iter.Basic
-public import Init.Data.String.Iter.Intercalate
+public import Init.Data.Iterators.Combinators.FilterMap
+public import Init.Data.Iterators.Consumers.Collect
+
+set_option doc.verso true
+
+namespace Std
+
+/--
+Convenience function for turning an iterator into a list of strings, provided the output of the
+iterator implements {name}`ToString`.
+-/
+@[inline]
+public abbrev Iter.toStringList {α β : Type} [Iterator α Id β] [ToString β]
+    (it : Iter (α := α) β) : List String :=
+  it.map toString |>.toList
+
+/--
+Convenience function for turning an iterator into an array of strings, provided the output of the
+iterator implements {name}`ToString`.
+-/
+@[inline]
+public abbrev Iter.toStringArray {α β : Type} [Iterator α Id β] [ToString β]
+    (it : Iter (α := α) β) : Array String :=
+  it.map toString |>.toArray
+
+end Std

src/Init/Data/String/Iter/Basic.lean

@@ -1,34 +0,0 @@
-/-
-Copyright (c) 2026 Lean FRO, LLC. All rights reserved.
-Released under Apache 2.0 license as described in the file LICENSE.
-Authors: Markus Himmel
--/
-module
-
-prelude
-public import Init.Data.Iterators.Combinators.FilterMap
-public import Init.Data.Iterators.Consumers.Collect
-
-set_option doc.verso true
-
-namespace Std
-
-/--
-Convenience function for turning an iterator into a list of strings, provided the output of the
-iterator implements {name}`ToString`.
--/
-@[inline]
-public abbrev Iter.toStringList {α β : Type} [Iterator α Id β] [ToString β]
-    (it : Iter (α := α) β) : List String :=
-  it.map toString |>.toList
-
-/--
-Convenience function for turning an iterator into an array of strings, provided the output of the
-iterator implements {name}`ToString`.
--/
-@[inline]
-public abbrev Iter.toStringArray {α β : Type} [Iterator α Id β] [ToString β]
-    (it : Iter (α := α) β) : Array String :=
-  it.map toString |>.toArray
-
-end Std

src/Init/Data/String/Iter/Intercalate.lean

@@ -1,37 +0,0 @@
-/-
-Copyright (c) 2026 Lean FRO, LLC. All rights reserved.
-Released under Apache 2.0 license as described in the file LICENSE.
-Authors: Julia Markus Himmel
--/
-module
-
-prelude
-public import Init.Data.Iterators.Combinators.Monadic.FilterMap
-public import Init.Data.String.Basic
-import Init.Data.String.Slice
-
-set_option doc.verso true
-
-namespace Std
-
-/--
-Appends all the elements in the iterator, in order.
--/
-@[inline]
-public def Iter.joinString {α β : Type} [Iterator α Id β] [ToString β]
-    (it : Std.Iter (α := α) β) : String :=
-  (it.map toString).fold (init := "") (· ++ ·)
-
-/--
-Appends the elements of the iterator into a string, placing the separator {name}`s` between them.
--/
-@[inline]
-public def Iter.intercalateString {α β : Type} [Iterator α Id β] [ToString β]
-    (s : String.Slice) (it : Std.Iter (α := α) β) : String :=
-  it.map toString
-    |>.fold (init := none) (fun
-      | none, sl => some sl
-      | some str, sl => some (str ++ s ++ sl))
-    |>.getD ""
-
-end Std

src/Init/Data/String/Lemmas.lean

@@ -17,7 +17,49 @@ public import Init.Data.String.Lemmas.Pattern
 public import Init.Data.String.Lemmas.Slice
 public import Init.Data.String.Lemmas.Iterate
 public import Init.Data.String.Lemmas.Intercalate
-public import Init.Data.String.Lemmas.Iter
-public import Init.Data.String.Lemmas.Hashable
-public import Init.Data.String.Lemmas.TakeDrop
-public import Init.Data.String.Lemmas.StringOrder
+import Init.Data.Order.Lemmas
+public import Init.Data.String.Basic
+import Init.Data.Char.Lemmas
+import Init.Data.Char.Order
+import Init.Data.List.Lex
+
+public section
+
+open Std
+
+namespace String
+
+@[deprecated toList_inj (since := "2025-10-30")]
+protected theorem data_eq_of_eq {a b : String} (h : a = b) : a.toList = b.toList :=
+  h ▸ rfl
+@[deprecated toList_inj (since := "2025-10-30")]
+protected theorem ne_of_data_ne {a b : String} (h : a.toList ≠ b.toList) : a ≠ b := by
+  simpa [← toList_inj]
+
+@[simp] protected theorem not_le {a b : String} : ¬ a ≤ b ↔ b < a := Decidable.not_not
+@[simp] protected theorem not_lt {a b : String} : ¬ a < b ↔ b ≤ a := Iff.rfl
+@[simp] protected theorem le_refl (a : String) : a ≤ a := List.le_refl _
+@[simp] protected theorem lt_irrefl (a : String) : ¬ a < a := List.lt_irrefl _
+
+attribute [local instance] Char.notLTTrans Char.ltTrichotomous Char.ltAsymm
+
+protected theorem le_trans {a b c : String} : a ≤ b → b ≤ c → a ≤ c := List.le_trans
+protected theorem lt_trans {a b c : String} : a < b → b < c → a < c := List.lt_trans
+protected theorem le_total (a b : String) : a ≤ b ∨ b ≤ a := List.le_total _ _
+protected theorem le_antisymm {a b : String} : a ≤ b → b ≤ a → a = b := fun h₁ h₂ => String.ext (List.le_antisymm (as := a.toList) (bs := b.toList) h₁ h₂)
+protected theorem lt_asymm {a b : String} (h : a < b) : ¬ b < a := List.lt_asymm h
+protected theorem ne_of_lt {a b : String} (h : a < b) : a ≠ b := by
+  have := String.lt_irrefl a
+  intro h; subst h; contradiction
+
+instance instIsLinearOrder : IsLinearOrder String := by
+  apply IsLinearOrder.of_le
+  case le_antisymm => constructor; apply String.le_antisymm
+  case le_trans => constructor; apply String.le_trans
+  case le_total => constructor; apply String.le_total
+
+instance : LawfulOrderLT String where
+  lt_iff a b := by
+    simp [← String.not_le, Decidable.imp_iff_not_or, Std.Total.total]
+
+end String

src/Init/Data/String/Lemmas/Basic.lean

@@ -7,7 +7,6 @@ module
 
 prelude
 public import Init.Data.String.Basic
-import all Init.Data.String.Basic
 import Init.Data.ByteArray.Lemmas
 import Init.Data.Nat.MinMax
 
@@ -22,10 +21,6 @@ public section
 
 namespace String
 
-@[simp]
-theorem singleton_inj {c d : Char} : singleton c = singleton d ↔ c = d := by
-  simp [← toList_inj]
-
 @[simp]
 theorem singleton_append_inj : singleton c ++ s = singleton d ++ t ↔ c = d ∧ s = t := by
   simp [← toList_inj]
@@ -61,11 +56,6 @@ theorem singleton_ne_empty {c : Char} : singleton c ≠ "" := by
 theorem empty_ne_singleton {c : Char} : "" ≠ singleton c := by
   simp
 
-@[simp]
-theorem ofList_cons {c : Char} {l : List Char} :
-    String.ofList (c :: l) = String.singleton c ++ String.ofList l := by
-  simp [← toList_inj]
-
 @[simp]
 theorem Slice.Pos.copy_inj {s : Slice} {p₁ p₂ : s.Pos} : p₁.copy = p₂.copy ↔ p₁ = p₂ := by
   simp [String.Pos.ext_iff, Pos.ext_iff]
@@ -195,74 +185,18 @@ theorem sliceTo_slice {s : String} {p₁ p₂ h p} :
 theorem Slice.sliceFrom_startPos {s : Slice} : s.sliceFrom s.startPos = s := by
   ext <;> simp
 
-@[simp]
-theorem Slice.sliceFrom_eq_self_iff {s : Slice} {p : s.Pos} : s.sliceFrom p = s ↔ p = s.startPos := by
-  refine ⟨?_, by rintro rfl; simp⟩
-  rcases s with ⟨str, startInclusive, endExclusive, h⟩
-  simp [sliceFrom, Slice.startPos, String.Pos.ext_iff, Pos.Raw.ext_iff, Slice.Pos.ext_iff]
-
 @[simp]
 theorem Slice.sliceTo_endPos {s : Slice} : s.sliceTo s.endPos = s := by
   ext <;> simp
 
-@[simp]
-theorem Slice.sliceTo_eq_self_iff {s : Slice} {p : s.Pos} : s.sliceTo p = s ↔ p = s.endPos := by
-  refine ⟨?_, by rintro rfl; simp⟩
-  rcases s with ⟨str, startInclusive, endExclusive, h⟩
-  simp [sliceTo, Slice.endPos, String.Pos.ext_iff, Pos.Raw.ext_iff, Slice.Pos.ext_iff,
-    utf8ByteSize_eq]
-  omega
-
-@[simp]
-theorem Slice.slice_startPos {s : Slice} {p : s.Pos} :
-    s.slice s.startPos p (Pos.startPos_le _) = s.sliceTo p := by
-  ext <;> simp
-
-@[simp]
-theorem Slice.slice_eq_self_iff {s : Slice} {p₁ p₂ : s.Pos} {h} :
-    s.slice p₁ p₂ h = s ↔ p₁ = s.startPos ∧ p₂ = s.endPos := by
-  refine ⟨?_, by rintro ⟨rfl, rfl⟩; simp⟩
-  rcases s with ⟨str, startInclusive, endExclusive, h⟩
-  simp [slice, Slice.endPos, String.Pos.ext_iff, Pos.Raw.ext_iff, Slice.Pos.ext_iff,
-    utf8ByteSize_eq]
-  omega
-
-@[simp]
-theorem Slice.slice_endPos {s : Slice} {p : s.Pos} :
-    s.slice p s.endPos (Pos.le_endPos _) = s.sliceFrom p := by
-  ext <;> simp
-
 @[simp]
 theorem sliceFrom_startPos {s : String} : s.sliceFrom s.startPos = s := by
   ext <;> simp
 
-@[simp]
-theorem sliceFrom_eq_toSlice_iff {s : String} {p : s.Pos} : s.sliceFrom p = s.toSlice ↔ p = s.startPos := by
-  simp [← sliceFrom_toSlice]
-
 @[simp]
 theorem sliceTo_endPos {s : String} : s.sliceTo s.endPos = s := by
   ext <;> simp
 
-@[simp]
-theorem sliceTo_eq_toSlice_iff {s : String} {p : s.Pos} : s.sliceTo p = s.toSlice ↔ p = s.endPos := by
-  simp [← sliceTo_toSlice]
-
-@[simp]
-theorem slice_startPos {s : String} {p : s.Pos} :
-    s.slice s.startPos p (Pos.startPos_le _) = s.sliceTo p := by
-  ext <;> simp
-
-@[simp]
-theorem slice_endPos {s : String} {p : s.Pos} :
-    s.slice p s.endPos (Pos.le_endPos _) = s.sliceFrom p := by
-  ext <;> simp
-
-@[simp]
-theorem slice_eq_toSlice_iff {s : String} {p₁ p₂ : s.Pos} {h} :
-    s.slice p₁ p₂ h = s.toSlice ↔ p₁ = s.startPos ∧ p₂ = s.endPos := by
-  simp [← slice_toSlice]
-
 end Iterate
 
 theorem Slice.copy_eq_copy_slice {s : Slice} {pos₁ pos₂ : s.Pos} {h} :
@@ -310,81 +244,4 @@ theorem Pos.get_ofToSlice {s : String} {p : (s.toSlice).Pos} {h} :
 @[simp]
 theorem push_empty {c : Char} : "".push c = singleton c := rfl
 
-namespace Slice.Pos
-
-@[simp]
-theorem nextn_zero {s : Slice} {p : s.Pos} : p.nextn 0 = p := by
-  simp [nextn]
-
-theorem nextn_add_one {s : Slice} {p : s.Pos} :
-    p.nextn (n + 1) = if h : p = s.endPos then p else (p.next h).nextn n := by
-  simp [nextn]
-
-@[simp]
-theorem nextn_endPos {s : Slice} : s.endPos.nextn n = s.endPos := by
-  cases n <;> simp [nextn_add_one]
-
-end Slice.Pos
-
-namespace Pos
-
-theorem nextn_eq_nextn_toSlice {s : String} {p : s.Pos} : p.nextn n = Pos.ofToSlice (p.toSlice.nextn n) :=
-  (rfl)
-
-@[simp]
-theorem nextn_zero {s : String} {p : s.Pos} : p.nextn 0 = p := by
-  simp [nextn_eq_nextn_toSlice]
-
-theorem nextn_add_one {s : String} {p : s.Pos} :
-    p.nextn (n + 1) = if h : p = s.endPos then p else (p.next h).nextn n := by
-  simp only [nextn_eq_nextn_toSlice, Slice.Pos.nextn_add_one, endPos_toSlice, toSlice_inj]
-  split <;> simp [Pos.next_toSlice]
-
-theorem nextn_toSlice {s : String} {p : s.Pos} : p.toSlice.nextn n = (p.nextn n).toSlice := by
-  induction n generalizing p with simp_all [nextn_add_one, Slice.Pos.nextn_add_one, apply_dite Pos.toSlice, next_toSlice]
-
-theorem toSlice_nextn {s : String} {p : s.Pos} : (p.nextn n).toSlice = p.toSlice.nextn n :=
-  nextn_toSlice.symm
-
-@[simp]
-theorem nextn_endPos {s : String} : s.endPos.nextn n = s.endPos := by
-  cases n <;> simp [nextn_add_one]
-
-end Pos
-
-@[simp]
-theorem Slice.Pos.cast_toSlice_copy {s : Slice} {pos : s.Pos} :
-    pos.copy.toSlice.cast (by simp) = pos := by
-  ext; simp
-
-@[simp]
-theorem Slice.Pos.sliceFrom_eq_startPos {s : Slice} {p : s.Pos} :
-    (Pos.sliceFrom p p (Pos.le_refl _)) = Slice.startPos _ := by
-  simp [← Pos.ofSliceFrom_inj]
-
-@[simp]
-theorem Slice.Pos.sliceFrom_endPos {s : Slice} {p : s.Pos} :
-    (Pos.sliceFrom p s.endPos (Pos.le_endPos _)) = Slice.endPos _ := by
-  simp [← Pos.ofSliceFrom_inj]
-
-@[simp]
-theorem Slice.Pos.sliceTo_startPos {s : Slice} {p : s.Pos} :
-    (Pos.sliceTo p s.startPos (Pos.startPos_le _)) = Slice.startPos _ := by
-  simp [← Pos.ofSliceTo_inj]
-
-@[simp]
-theorem Slice.Pos.sliceTo_eq_endPos {s : Slice} {p : s.Pos} :
-    (Pos.sliceTo p p (Pos.le_refl _)) = Slice.endPos _ := by
-  simp [← Pos.ofSliceTo_inj]
-
-@[simp]
-theorem Slice.Pos.slice_eq_startPos {s : Slice} {p₀ p₁ : s.Pos} {h} :
-    (Pos.slice p₀ p₀ p₁ (Pos.le_refl _) h) = Slice.startPos _ := by
-  simp [← Pos.ofSlice_inj]
-
-@[simp]
-theorem Slice.Pos.slice_eq_endPos {s : Slice} {p₀ p₁ : s.Pos} {h} :
-    (Pos.slice p₁ p₀ p₁ h (Pos.le_refl _)) = Slice.endPos _ := by
-  simp [← Pos.ofSlice_inj]
-
 end String

src/Init/Data/String/Lemmas/FindPos.lean

@@ -11,8 +11,6 @@ import all Init.Data.String.FindPos
 import Init.Data.String.OrderInstances
 import Init.Data.String.Lemmas.Order
 import Init.Data.Order.Lemmas
-import Init.Data.Option.Lemmas
-import Init.ByCases
 
 public section
 
@@ -201,10 +199,6 @@ theorem Pos.prev_eq_iff {s : Slice} {p q : s.Pos} {h} :
 theorem Pos.prev_lt {s : Slice} {p : s.Pos} {h} : p.prev h < p := by
   simp
 
-@[simp]
-theorem Pos.prev_le {s : Slice} {p : s.Pos} {h} : p.prev h ≤ p :=
-  Std.le_of_lt (by simp)
-
 @[simp]
 theorem Pos.prev_ne_endPos {s : Slice} {p : s.Pos} {h} : p.prev h ≠ s.endPos :=
   ne_endPos_of_lt prev_lt
@@ -215,29 +209,6 @@ theorem Pos.prevn_le {s : Slice} {p : s.Pos} {n : Nat} : p.prevn n ≤ p := by
   | case2 p n h ih => exact Std.le_of_lt (by simpa using ih)
   | case3 => simp
 
-theorem Pos.ofSliceTo_prev {s : Slice} {p₀ : s.Pos} {p : (s.sliceTo p₀).Pos} {h} :
-    Pos.ofSliceTo (p.prev h) = (Pos.ofSliceTo p).prev (by simpa [← Pos.ofSliceTo_inj] using h) := by
-  rw [eq_comm, Pos.prev_eq_iff]
-  simp only [Pos.ofSliceTo_lt_ofSliceTo_iff, Pos.le_ofSliceTo_iff]
-  simp [Pos.lt_ofSliceTo_iff]
-
-theorem Pos.prev_ofSliceTo {s : Slice} {p₀ : s.Pos} {p : (s.sliceTo p₀).Pos} {h} :
-    (Pos.ofSliceTo p).prev h = Pos.ofSliceTo (p.prev (by simpa [← Pos.ofSliceTo_inj])) := by
-  simp [ofSliceTo_prev]
-
-theorem Pos.ofSliceFrom_prev {s : Slice} {p₀ : s.Pos} {p : (s.sliceFrom p₀).Pos} {h} :
-    Pos.ofSliceFrom (p.prev h) = (Pos.ofSliceFrom p).prev (by exact ofSliceFrom_ne_startPos h) := by
-  rw [eq_comm, Pos.prev_eq_iff]
-  simp only [Pos.ofSliceFrom_lt_ofSliceFrom_iff,  Pos.le_ofSliceFrom_iff]
-  simp [Pos.lt_ofSliceFrom_iff]
-
-theorem Pos.ofSlice_prev {s : Slice} {p₀ p₁ : s.Pos} {h}
-    {p : (s.slice p₀ p₁ h).Pos} {h'} :
-    Pos.ofSlice (p.prev h') = (Pos.ofSlice p).prev (by exact ofSlice_ne_startPos h') := by
-  rw [eq_comm, Pos.prev_eq_iff]
-  simp only [ofSlice_lt_ofSlice_iff,  le_ofSlice_iff]
-  simpa +contextual [← ofSlice_lt_ofSlice_iff] using fun q hq => Std.le_of_lt (Std.lt_of_lt_of_le hq ofSlice_le)
-
 @[simp]
 theorem Pos.prev_next {s : Slice} {p : s.Pos} {h} : (p.next h).prev (by simp) = p :=
   prev_eq_iff.2 (by simp)
@@ -246,23 +217,6 @@ theorem Pos.prev_next {s : Slice} {p : s.Pos} {h} : (p.next h).prev (by simp) =
 theorem Pos.next_prev {s : Slice} {p : s.Pos} {h} : (p.prev h).next (by simp) = p :=
   next_eq_iff.2 (by simp)
 
-theorem Pos.prev?_eq_dif {s : Slice} {p : s.Pos} : p.prev? = if h : p = s.startPos then none else some (p.prev h) :=
-  (rfl)
-
-theorem Pos.prev?_eq_some_prev {s : Slice} {p : s.Pos} (h : p ≠ s.startPos) : p.prev? = some (p.prev h) := by
-  simp [Pos.prev?, h]
-
-@[simp]
-theorem Pos.prev?_eq_none_iff {s : Slice} {p : s.Pos} : p.prev? = none ↔ p = s.startPos := by
-  simp [Pos.prev?]
-
-theorem Pos.prev?_eq_none {s : Slice} {p : s.Pos} (h : p = s.startPos) : p.prev? = none :=
-  prev?_eq_none_iff.2 h
-
-@[simp]
-theorem Pos.prev?_startPos {s : Slice} : s.startPos.prev? = none := by
-  simp
-
 end Slice
 
 @[simp]
@@ -466,10 +420,6 @@ theorem Pos.prev_eq_iff {s : String} {p q : s.Pos} {h} :
 theorem Pos.prev_lt {s : String} {p : s.Pos} {h} : p.prev h < p := by
   simp
 
-@[simp]
-theorem Pos.prev_le {s : String} {p : s.Pos} {h} : p.prev h ≤ p :=
-  Std.le_of_lt (by simp)
-
 @[simp]
 theorem Pos.prev_ne_endPos {s : String} {p : s.Pos} {h} : p.prev h ≠ s.endPos :=
   ne_endPos_of_lt prev_lt
@@ -478,45 +428,14 @@ theorem Pos.toSlice_prev {s : String} {p : s.Pos} {h} :
     (p.prev h).toSlice = p.toSlice.prev (by simpa [toSlice_inj]) := by
   simp [prev]
 
-theorem Pos.ofToSlice_prev {s : String} {p : s.toSlice.Pos} {h} :
-    Pos.ofToSlice (p.prev h) = (Pos.ofToSlice p).prev (by simpa [← toSlice_inj]) := by
-  simp [prev]
-
 theorem Pos.prev_toSlice {s : String} {p : s.Pos} {h} :
     p.toSlice.prev h = (p.prev (by simpa [← toSlice_inj])).toSlice := by
   simp [prev]
 
-theorem Pos.prev_ofToSlice {s : String} {p : s.toSlice.Pos} {h} :
-    (Pos.ofToSlice p).prev h = Pos.ofToSlice (p.prev (by simpa [← ofToSlice_inj])) := by
-  simp [prev]
-
 theorem Pos.prevn_le {s : String} {p : s.Pos} {n : Nat} :
     p.prevn n ≤ p := by
   simpa [Pos.le_iff, ← offset_toSlice] using Slice.Pos.prevn_le
 
-theorem Pos.ofSliceTo_prev {s : String} {p₀ : s.Pos} {p : (s.sliceTo p₀).Pos} {h} :
-    Pos.ofSliceTo (p.prev h) = (Pos.ofSliceTo p).prev (by simpa [← Pos.ofSliceTo_inj] using h) := by
-  rw [eq_comm, Pos.prev_eq_iff]
-  simp only [Pos.ofSliceTo_lt_ofSliceTo_iff, Pos.le_ofSliceTo_iff]
-  simp [Pos.lt_ofSliceTo_iff]
-
-theorem Pos.prev_ofSliceTo {s : String} {p₀ : s.Pos} {p : (s.sliceTo p₀).Pos} {h} :
-    (Pos.ofSliceTo p).prev h = Pos.ofSliceTo (p.prev (by simpa [← Pos.ofSliceTo_inj])) := by
-  simp [ofSliceTo_prev]
-
-theorem Pos.ofSliceFrom_prev {s : String} {p₀ : s.Pos} {p : (s.sliceFrom p₀).Pos} {h} :
-    Pos.ofSliceFrom (p.prev h) = (Pos.ofSliceFrom p).prev (by exact ofSliceFrom_ne_startPos h) := by
-  rw [eq_comm, Pos.prev_eq_iff]
-  simp only [Pos.ofSliceFrom_lt_ofSliceFrom_iff, Pos.le_ofSliceFrom_iff]
-  simp [Pos.lt_ofSliceFrom_iff]
-
-theorem Pos.ofSlice_prev {s : String} {p₀ p₁ : s.Pos} {h}
-    {p : (s.slice p₀ p₁ h).Pos} {h'} :
-    Pos.ofSlice (p.prev h') = (Pos.ofSlice p).prev (by exact ofSlice_ne_startPos h') := by
-  rw [eq_comm, Pos.prev_eq_iff]
-  simp only [ofSlice_lt_ofSlice_iff, le_ofSlice_iff]
-  simpa +contextual [← ofSlice_lt_ofSlice_iff] using fun q hq => Std.le_of_lt (Std.lt_of_lt_of_le hq ofSlice_le)
-
 @[simp]
 theorem Pos.prev_next {s : String} {p : s.Pos} {h} : (p.next h).prev (by simp) = p :=
   prev_eq_iff.2 (by simp)
@@ -525,71 +444,4 @@ theorem Pos.prev_next {s : String} {p : s.Pos} {h} : (p.next h).prev (by simp) =
 theorem Pos.next_prev {s : String} {p : s.Pos} {h} : (p.prev h).next (by simp) = p :=
   next_eq_iff.2 (by simp)
 
-theorem Pos.prev?_eq_prev?_toSlice {s : String} {p : s.Pos} : p.prev? = p.toSlice.prev?.map Pos.ofToSlice :=
-  (rfl)
-
-theorem Pos.prev?_toSlice {s : String} {p : s.Pos} : p.toSlice.prev? = p.prev?.map Pos.toSlice := by
-  simp [prev?_eq_prev?_toSlice]
-
-theorem Pos.prev?_eq_dif {s : String} {p : s.Pos} : p.prev? = if h : p = s.startPos then none else some (p.prev h) := by
-  simp [prev?_eq_prev?_toSlice, Slice.Pos.prev?_eq_dif, apply_dite (Option.map Pos.ofToSlice),
-    ofToSlice_prev]
-
-theorem Pos.prev?_eq_some_prev {s : String} {p : s.Pos} (h : p ≠ s.startPos) : p.prev? = some (p.prev h) := by
-  simp [prev?_eq_prev?_toSlice, Slice.Pos.prev?_eq_some_prev (by simpa : p.toSlice ≠ s.toSlice.startPos),
-    ofToSlice_prev]
-
-@[simp]
-theorem Pos.prev?_eq_none_iff {s : String} {p : s.Pos} : p.prev? = none ↔ p = s.startPos := by
-  simp [prev?_eq_prev?_toSlice]
-
-theorem Pos.prev?_eq_none {s : String} {p : s.Pos} (h : p = s.startPos) : p.prev? = none :=
-  prev?_eq_none_iff.2 h
-
-@[simp]
-theorem Pos.prev?_startPos {s : String} : s.startPos.prev? = none := by
-  simp
-
-namespace Slice.Pos
-
-@[simp]
-theorem prevn_zero {s : Slice} {p : s.Pos} : p.prevn 0 = p := by
-  simp [prevn]
-
-theorem prevn_add_one {s : Slice} {p : s.Pos} :
-    p.prevn (n + 1) = if h : p = s.startPos then p else (p.prev h).prevn n := by
-  simp [prevn]
-
-@[simp]
-theorem prevn_startPos {s : Slice} : s.startPos.prevn n = s.startPos := by
-  cases n <;> simp [prevn_add_one]
-
-end Slice.Pos
-
-namespace Pos
-
-theorem prevn_eq_prevn_toSlice {s : String} {p : s.Pos} : p.prevn n = Pos.ofToSlice (p.toSlice.prevn n) :=
-  (rfl)
-
-@[simp]
-theorem prevn_zero {s : String} {p : s.Pos} : p.prevn 0 = p := by
-  simp [prevn_eq_prevn_toSlice]
-
-theorem prevn_add_one {s : String} {p : s.Pos} :
-    p.prevn (n + 1) = if h : p = s.startPos then p else (p.prev h).prevn n := by
-  simp only [prevn_eq_prevn_toSlice, Slice.Pos.prevn_add_one, startPos_toSlice, toSlice_inj]
-  split <;> simp [Pos.prev_toSlice]
-
-theorem prevn_toSlice {s : String} {p : s.Pos} : p.toSlice.prevn n = (p.prevn n).toSlice := by
-  induction n generalizing p with simp_all [prevn_add_one, Slice.Pos.prevn_add_one, apply_dite Pos.toSlice, prev_toSlice]
-
-theorem toSlice_prevn {s : String} {p : s.Pos} : (p.prevn n).toSlice = p.toSlice.prevn n :=
-  prevn_toSlice.symm
-
-@[simp]
-theorem prevn_startPos {s : String} : s.startPos.prevn n = s.startPos := by
-  cases n <;> simp [prevn_add_one]
-
-end Pos
-
 end String

src/Init/Data/String/Lemmas/Hashable.lean

@@ -1,25 +0,0 @@
-/-
-Copyright (c) 2026 Lean FRO, LLC. All rights reserved.
-Released under Apache 2.0 license as described in the file LICENSE.
-Authors: Julia Markus Himmel
--/
-module
-
-prelude
-public import Init.Data.String.Slice
-public import Init.Data.LawfulHashable
-import all Init.Data.String.Slice
-import Init.Data.String.Lemmas.Slice
-
-namespace String
-
-public theorem hash_eq {s : String} : hash s = String.hash s := rfl
-
-namespace Slice
-
-public theorem hash_eq {s : String.Slice} : hash s = String.hash s.copy := (rfl)
-
-public instance : LawfulHashable String.Slice where
-  hash_eq a b hab := by simp [hash_eq, beq_eq_true_iff.1 hab]
-
-end String.Slice

src/Init/Data/String/Lemmas/Intercalate.lean

@@ -10,7 +10,6 @@ public import Init.Data.String.Defs
 import all Init.Data.String.Defs
 public import Init.Data.String.Slice
 import all Init.Data.String.Slice
-import Init.ByCases
 
 public section
 
@@ -43,16 +42,6 @@ theorem intercalate_cons_of_ne_nil {s t : String} {l : List String} (h : l ≠ [
   match l, h with
   | u::l, _ => by simp
 
-theorem intercalate_append_of_ne_nil {l m : List String} {s : String} (hl : l ≠ []) (hm : m ≠ []) :
-    s.intercalate (l ++ m) = s.intercalate l ++ s ++ s.intercalate m := by
-  induction l with
-  | nil => simp_all
-  | cons hd tl ih =>
-    rw [List.cons_append, intercalate_cons_of_ne_nil (by simp_all)]
-    by_cases ht : tl = []
-    · simp_all
-    · simp [ih ht, intercalate_cons_of_ne_nil ht, String.append_assoc]
-
 @[simp]
 theorem toList_intercalate {s : String} {l : List String} :
     (s.intercalate l).toList = s.toList.intercalate (l.map String.toList) := by
@@ -60,32 +49,6 @@ theorem toList_intercalate {s : String} {l : List String} :
   | nil => simp
   | cons hd tl ih => cases tl <;> simp_all
 
-theorem join_eq_foldl : join l = l.foldl (fun r s => r ++ s) "" :=
-  (rfl)
-
-@[simp]
-theorem join_nil : join [] = "" := by
-  simp [join]
-
-@[simp]
-theorem join_cons : join (s :: l) = s ++ join l := by
-  simp only [join, List.foldl_cons, empty_append]
-  conv => lhs; rw [← String.append_empty (s := s)]
-  rw [List.foldl_assoc]
-
-@[simp]
-theorem toList_join {l : List String} : (String.join l).toList = l.flatMap String.toList := by
-  induction l <;> simp_all
-
-@[simp]
-theorem join_append {l m : List String} : String.join (l ++ m) = String.join l ++ String.join m := by
-  simp [← toList_inj]
-
-@[simp]
-theorem length_join {l : List String} : (String.join l).length = (l.map String.length).sum := by
-  simp only [← length_toList, toList_join, List.length_flatMap]
-  simp
-
 namespace Slice
 
 @[simp]
@@ -102,10 +65,6 @@ theorem intercalate_eq {s : Slice} {l : List Slice} :
   | nil => simp [intercalate]
   | cons hd tl ih => cases tl <;> simp_all [intercalate, intercalate.go, intercalateGo_append]
 
-@[simp]
-theorem join_eq {l : List Slice} : join l = String.join (l.map copy) := by
-  simp [join, String.join, List.foldl_map]
-
 end Slice
 
 end String

src/Init/Data/String/Lemmas/IsEmpty.lean

@@ -204,7 +204,7 @@ theorem Slice.copy_sliceTo_startPos {s : Slice} : (s.sliceTo s.startPos).copy =
   simp
 
 @[simp]
-theorem Slice.copy_sliceFrom_endPos {s : Slice} : (s.sliceFrom s.endPos).copy = "" := by
+theorem Slice.copy_sliceFrom_startPos {s : Slice} : (s.sliceFrom s.endPos).copy = "" := by
   simp
 
 end CopyEqEmpty

src/Init/Data/String/Lemmas/Iter.lean

@@ -1,50 +0,0 @@
-/-
-Copyright (c) 2026 Lean FRO, LLC. All rights reserved.
-Released under Apache 2.0 license as described in the file LICENSE.
-Authors: Julia Markus Himmel
--/
-module
-
-prelude
-public import Init.Data.String.Iter.Intercalate
-public import Init.Data.String.Slice
-import all Init.Data.String.Iter.Intercalate
-import all Init.Data.String.Defs
-import Init.Data.String.Lemmas.Intercalate
-import Init.Data.Iterators.Lemmas.Consumers.Loop
-import Init.Data.Iterators.Lemmas.Combinators.FilterMap
-
-namespace Std.Iter
-
-@[simp]
-public theorem joinString_eq {α β : Type} [Std.Iterator α Id β] [Std.Iterators.Finite α Id]
-    [ToString β] {it : Std.Iter (α := α) β} :
-    it.joinString = String.join (it.toList.map toString) := by
-  rw [joinString, String.join, ← foldl_toList, toList_map]
-
-@[simp]
-public theorem intercalateString_eq {α β : Type} [Std.Iterator α Id β] [Std.Iterators.Finite α Id]
-    [ToString β] {s : String.Slice} {it : Std.Iter (α := α) β} :
-    it.intercalateString s = s.copy.intercalate (it.toList.map toString) := by
-  simp only [intercalateString, String.appendSlice_eq, ← foldl_toList, toList_map]
-  generalize s.copy = s
-  suffices ∀ (l m : List String),
-      (l.foldl (init := if m = [] then none else some (s.intercalate m))
-        (fun | none, sl => some sl | some str, sl => some (str ++ s ++ sl))).getD ""
-        = s.intercalate (m ++ l) by
-    simpa [-foldl_toList] using this (it.toList.map toString) []
-  intro l m
-  induction l generalizing m with
-  | nil => cases m <;> simp
-  | cons hd tl ih =>
-    rw [List.append_cons, ← ih, List.foldl_cons]
-    congr
-    simp only [List.append_eq_nil_iff, List.cons_ne_self, and_false, ↓reduceIte]
-    match m with
-    | [] => simp
-    | x::xs =>
-      simp only [reduceCtorEq, ↓reduceIte, List.cons_append, Option.some.injEq]
-      rw [← List.cons_append, String.intercalate_append_of_ne_nil (by simp) (by simp),
-        String.intercalate_singleton]
-
-end Std.Iter

src/Init/Data/String/Lemmas/Order.lean

@@ -11,7 +11,6 @@ import Init.Data.String.OrderInstances
 import Init.Data.String.Lemmas.Basic
 import Init.Data.Order.Lemmas
 import Init.Omega
-import Init.ByCases
 
 public section
 
@@ -71,7 +70,7 @@ theorem Pos.le_startPos {s : String} (p : s.Pos) : p ≤ s.startPos ↔ p = s.st
   ⟨fun h => Std.le_antisymm h (startPos_le _), by simp +contextual⟩
 
 @[simp]
-theorem Pos.startPos_lt_iff {s : String} (p : s.Pos) : s.startPos < p ↔ p ≠ s.startPos := by
+theorem Pos.startPos_lt_iff {s : String} {p : s.Pos} : s.startPos < p ↔ p ≠ s.startPos := by
   simp [← le_startPos, Std.not_le]
 
 @[simp]
@@ -236,10 +235,6 @@ theorem Slice.Pos.ofSliceFrom_next {s : Slice} {p₀ : s.Pos} {p : (s.sliceFrom
     Pos.next_le_iff_lt, true_and]
   simp [Pos.ofSliceFrom_lt_iff]
 
-theorem Slice.Pos.next_ofSliceFrom {s : Slice} {p₀ : s.Pos} {p : (s.sliceFrom p₀).Pos} {h} :
-    (Pos.ofSliceFrom p).next h = Pos.ofSliceFrom (p.next (by simpa [← Pos.ofSliceFrom_inj])) := by
-  simp [ofSliceFrom_next]
-
 theorem Pos.ofSliceFrom_next {s : String} {p₀ : s.Pos} {p : (s.sliceFrom p₀).Pos} {h} :
     Pos.ofSliceFrom (p.next h) = (Pos.ofSliceFrom p).next (by simpa [← Pos.ofSliceFrom_inj] using h) := by
   rw [eq_comm, Pos.next_eq_iff]
@@ -247,10 +242,6 @@ theorem Pos.ofSliceFrom_next {s : String} {p₀ : s.Pos} {p : (s.sliceFrom p₀)
     Slice.Pos.next_le_iff_lt, true_and]
   simp [Pos.ofSliceFrom_lt_iff]
 
-theorem Pos.next_ofSliceFrom {s : String} {p₀ : s.Pos} {p : (s.sliceFrom p₀).Pos} {h} :
-    (Pos.ofSliceFrom p).next h = Pos.ofSliceFrom (p.next (by simpa [← Pos.ofSliceFrom_inj])) := by
-  simp [Pos.ofSliceFrom_next]
-
 theorem Slice.Pos.le_ofSliceTo_iff {s : Slice} {p₀ : s.Pos} {p : (s.sliceTo p₀).Pos} {q : s.Pos} :
     q ≤ Pos.ofSliceTo p ↔ ∃ h, Slice.Pos.sliceTo p₀ q h ≤ p := by
   refine ⟨fun h => ⟨Slice.Pos.le_trans h Pos.ofSliceTo_le, ?_⟩, fun ⟨h, h'⟩ => ?_⟩
@@ -368,41 +359,11 @@ theorem Slice.Pos.ofSliceTo_ne_endPos {s : Slice} {p₀ : s.Pos} {p : (s.sliceTo
   refine (lt_endPos_iff _).1 (Std.lt_of_lt_of_le ?_ (le_endPos p₀))
   simpa [← lt_endPos_iff, ← ofSliceTo_lt_ofSliceTo_iff] using h
 
-theorem Slice.Pos.ne_endPos_of_sliceTo_ne_endPos {s : Slice} {p p₀ : s.Pos} {h₀}
-    (h : Pos.sliceTo p₀ p h₀ ≠ Slice.endPos _) : p ≠ s.endPos := by
-  rw [← Pos.ofSliceTo_sliceTo (h := h₀)]
-  apply Pos.ofSliceTo_ne_endPos h
-
-theorem Slice.Pos.ofSliceFrom_ne_startPos {s : Slice} {p₀ : s.Pos} {p : (s.sliceFrom p₀).Pos}
-    (h : p ≠ (s.sliceFrom p₀).startPos) : Pos.ofSliceFrom p ≠ s.startPos := by
-  refine (startPos_lt_iff _).1 (Std.lt_of_le_of_lt (startPos_le p₀) ?_)
-  simpa [← startPos_lt_iff, ← ofSliceFrom_lt_ofSliceFrom_iff] using h
-
-theorem Slice.Pos.ne_startPos_of_sliceFrom_ne_startPos {s : Slice} {p p₀ : s.Pos} {h₀}
-    (h : Pos.sliceFrom p₀ p h₀ ≠ Slice.startPos _) : p ≠ s.startPos := by
-  rw [← Pos.ofSliceFrom_sliceFrom (h := h₀)]
-  apply Pos.ofSliceFrom_ne_startPos h
-
 theorem Pos.ofSliceTo_ne_endPos {s : String} {p₀ : s.Pos} {p : (s.sliceTo p₀).Pos}
     (h : p ≠ (s.sliceTo p₀).endPos) : Pos.ofSliceTo p ≠ s.endPos := by
   refine (lt_endPos_iff _).1 (Std.lt_of_lt_of_le ?_ (le_endPos p₀))
   simpa [← Slice.Pos.lt_endPos_iff, ← ofSliceTo_lt_ofSliceTo_iff] using h
 
-theorem Pos.ne_endPos_of_sliceTo_ne_endPos {s : String} {p p₀ : s.Pos} {h₀}
-    (h : Pos.sliceTo p₀ p h₀ ≠ Slice.endPos _) : p ≠ s.endPos := by
-  rw [← Pos.ofSliceTo_sliceTo (h := h₀)]
-  apply Pos.ofSliceTo_ne_endPos h
-
-theorem Pos.ofSliceFrom_ne_startPos {s : String} {p₀ : s.Pos} {p : (s.sliceFrom p₀).Pos}
-    (h : p ≠ (s.sliceFrom p₀).startPos) : Pos.ofSliceFrom p ≠ s.startPos := by
-  refine (startPos_lt_iff _).1 (Std.lt_of_le_of_lt (startPos_le p₀) ?_)
-  simpa [← Slice.Pos.startPos_lt_iff, ← ofSliceFrom_lt_ofSliceFrom_iff] using h
-
-theorem Pos.ne_startPos_of_sliceFrom_ne_startPos {s : String} {p p₀ : s.Pos} {h₀}
-    (h : Pos.sliceFrom p₀ p h₀ ≠ Slice.startPos _) : p ≠ s.startPos := by
-  rw [← Pos.ofSliceFrom_sliceFrom (h := h₀)]
-  apply Pos.ofSliceFrom_ne_startPos h
-
 theorem Slice.Pos.ofSliceTo_next {s : Slice} {p₀ : s.Pos} {p : (s.sliceTo p₀).Pos} {h} :
     Pos.ofSliceTo (p.next h) = (Pos.ofSliceTo p).next (ofSliceTo_ne_endPos h) := by
   rw [eq_comm, Pos.next_eq_iff]
@@ -445,130 +406,16 @@ theorem Pos.slice_le_slice_iff {s : String} {p₀ p₁ : s.Pos} {q r : s.Pos}
   simp [Slice.Pos.le_iff, Pos.le_iff, Pos.Raw.le_iff] at h₁ h₁' ⊢
   omega
 
-theorem Slice.Pos.le_ofSlice_iff {s : Slice} {p₀ p₁ : s.Pos} {h} {p : (s.slice p₀ p₁ h).Pos} {q : s.Pos} :
-    q ≤ Pos.ofSlice p ↔ ∃ h₁, ∀ h₀, Slice.Pos.slice q p₀ p₁ h₀ h₁ ≤ p := by
-  refine ⟨fun h => ⟨Std.le_trans h ofSlice_le, fun h' => ?_⟩, fun ⟨h₁, h⟩ => ?_⟩
-  · simp only [← Slice.Pos.slice_ofSlice (pos := p), slice_le_slice_iff]
-    simpa
-  · by_cases h₀ : p₀ ≤ q
-    · simpa only [← Slice.Pos.ofSlice_slice (h₁ := h₀) (h₂ := h₁), ofSlice_le_ofSlice_iff] using h h₀
-    · exact Std.le_of_lt (Std.lt_of_lt_of_le (Std.not_le.1 h₀) le_ofSlice)
-
-theorem Slice.Pos.ofSlice_lt_iff {s : Slice} {p₀ p₁ : s.Pos} {h} {p : (s.slice p₀ p₁ h).Pos} {q : s.Pos} :
-    Pos.ofSlice p < q ↔ ∀ h₁, ∃ h₀, p < Slice.Pos.slice q p₀ p₁ h₀ h₁ := by
-  simp [← Std.not_le, le_ofSlice_iff]
-
-theorem Slice.Pos.lt_ofSlice_iff {s : Slice} {p₀ p₁ : s.Pos} {h} {p : (s.slice p₀ p₁ h).Pos} {q : s.Pos} :
-    q < Pos.ofSlice p ↔ ∃ h₁, ∀ h₀, Slice.Pos.slice q p₀ p₁ h₀ h₁ < p := by
-  refine ⟨fun h => ⟨Std.le_of_lt (Std.lt_of_lt_of_le h ofSlice_le), fun h' => ?_⟩, fun ⟨h₁, h⟩ => ?_⟩
-  · simp only [← Slice.Pos.slice_ofSlice (pos := p), slice_lt_slice_iff]
-    simpa
-  · by_cases h₀ : p₀ ≤ q
-    · simpa only [← Slice.Pos.ofSlice_slice (h₁ := h₀) (h₂ := h₁), ofSlice_lt_ofSlice_iff] using h h₀
-    · exact Std.lt_of_lt_of_le (Std.not_le.1 h₀) le_ofSlice
-
-theorem Slice.Pos.ofSlice_le_iff {s : Slice} {p₀ p₁ : s.Pos} {h} {p : (s.slice p₀ p₁ h).Pos} {q : s.Pos} :
-    Pos.ofSlice p ≤ q ↔ ∀ h₁, ∃ h₀, p ≤ Slice.Pos.slice q p₀ p₁ h₀ h₁ := by
-  simp [← Std.not_lt, lt_ofSlice_iff]
-
-theorem Pos.le_ofSlice_iff {s : String} {p₀ p₁ : s.Pos} {h} {p : (s.slice p₀ p₁ h).Pos} {q : s.Pos} :
-    q ≤ Pos.ofSlice p ↔ ∃ h₁, ∀ h₀, Pos.slice q p₀ p₁ h₀ h₁ ≤ p := by
-  refine ⟨fun h => ⟨Std.le_trans h ofSlice_le, fun h' => ?_⟩, fun ⟨h₁, h⟩ => ?_⟩
-  · simp only [← Pos.slice_ofSlice (pos := p), slice_le_slice_iff]
-    simpa
-  · by_cases h₀ : p₀ ≤ q
-    · simpa only [← Pos.ofSlice_slice (h₁ := h₀) (h₂ := h₁), ofSlice_le_ofSlice_iff] using h h₀
-    · exact Std.le_of_lt (Std.lt_of_lt_of_le (Std.not_le.1 h₀) le_ofSlice)
-
-theorem Pos.ofSlice_lt_iff {s : String} {p₀ p₁ : s.Pos} {h} {p : (s.slice p₀ p₁ h).Pos} {q : s.Pos} :
-    Pos.ofSlice p < q ↔ ∀ h₁, ∃ h₀, p < Pos.slice q p₀ p₁ h₀ h₁ := by
-  simp [← Std.not_le, le_ofSlice_iff]
-
-theorem Pos.lt_ofSlice_iff {s : String} {p₀ p₁ : s.Pos} {h} {p : (s.slice p₀ p₁ h).Pos} {q : s.Pos} :
-    q < Pos.ofSlice p ↔ ∃ h₁, ∀ h₀, Pos.slice q p₀ p₁ h₀ h₁ < p := by
-  refine ⟨fun h => ⟨Std.le_of_lt (Std.lt_of_lt_of_le h ofSlice_le), fun h' => ?_⟩, fun ⟨h₁, h⟩ => ?_⟩
-  · simp only [← Pos.slice_ofSlice (pos := p), slice_lt_slice_iff]
-    simpa
-  · by_cases h₀ : p₀ ≤ q
-    · simpa only [← Pos.ofSlice_slice (h₁ := h₀) (h₂ := h₁), ofSlice_lt_ofSlice_iff] using h h₀
-    · exact Std.lt_of_lt_of_le (Std.not_le.1 h₀) le_ofSlice
-
-theorem Pos.ofSlice_le_iff {s : String} {p₀ p₁ : s.Pos} {h} {p : (s.slice p₀ p₁ h).Pos} {q : s.Pos} :
-    Pos.ofSlice p ≤ q ↔ ∀ h₁, ∃ h₀, p ≤ Pos.slice q p₀ p₁ h₀ h₁ := by
-  simp [← Std.not_lt, lt_ofSlice_iff]
-
-theorem Slice.Pos.slice_le_iff {s : Slice} {p₀ p₁ : s.Pos} {h} {p : (s.slice p₀ p₁ h).Pos} {q : s.Pos} {h₀ h₁} :
-    Slice.Pos.slice q p₀ p₁ h₀ h₁ ≤ p ↔ q ≤ Pos.ofSlice p := by
-  simp [le_ofSlice_iff, h₀, h₁]
-
-theorem Slice.Pos.lt_slice_iff {s : Slice} {p₀ p₁ : s.Pos} {h} {p : (s.slice p₀ p₁ h).Pos} {q : s.Pos} {h₀ h₁} :
-    p < Slice.Pos.slice q p₀ p₁ h₀ h₁ ↔ Pos.ofSlice p < q := by
-  simp [ofSlice_lt_iff, h₀, h₁]
-
-theorem Slice.Pos.slice_lt_iff {s : Slice} {p₀ p₁ : s.Pos} {h} {p : (s.slice p₀ p₁ h).Pos} {q : s.Pos} {h₀ h₁} :
-    Slice.Pos.slice q p₀ p₁ h₀ h₁ < p ↔ q < Pos.ofSlice p := by
-  simp [lt_ofSlice_iff, h₀, h₁]
-
-theorem Slice.Pos.le_slice_iff {s : Slice} {p₀ p₁ : s.Pos} {h} {p : (s.slice p₀ p₁ h).Pos} {q : s.Pos} {h₀ h₁} :
-    p ≤ Slice.Pos.slice q p₀ p₁ h₀ h₁ ↔ Pos.ofSlice p ≤ q := by
-  simp [ofSlice_le_iff, h₀, h₁]
-
-theorem Pos.slice_le_iff {s : String} {p₀ p₁ : s.Pos} {h} {p : (s.slice p₀ p₁ h).Pos} {q : s.Pos} {h₀ h₁} :
-    Pos.slice q p₀ p₁ h₀ h₁ ≤ p ↔ q ≤ Pos.ofSlice p := by
-  simp [le_ofSlice_iff, h₀, h₁]
-
-theorem Pos.lt_slice_iff {s : String} {p₀ p₁ : s.Pos} {h} {p : (s.slice p₀ p₁ h).Pos} {q : s.Pos} {h₀ h₁} :
-    p < Pos.slice q p₀ p₁ h₀ h₁ ↔ Pos.ofSlice p < q := by
-  simp [ofSlice_lt_iff, h₀, h₁]
-
-theorem Pos.slice_lt_iff {s : String} {p₀ p₁ : s.Pos} {h} {p : (s.slice p₀ p₁ h).Pos} {q : s.Pos} {h₀ h₁} :
-    Pos.slice q p₀ p₁ h₀ h₁ < p ↔ q < Pos.ofSlice p := by
-  simp [lt_ofSlice_iff, h₀, h₁]
-
-theorem Pos.le_slice_iff {s : String} {p₀ p₁ : s.Pos} {h} {p : (s.slice p₀ p₁ h).Pos} {q : s.Pos} {h₀ h₁} :
-    p ≤ Pos.slice q p₀ p₁ h₀ h₁ ↔ Pos.ofSlice p ≤ q := by
-  simp [ofSlice_le_iff, h₀, h₁]
-
 theorem Slice.Pos.ofSlice_ne_endPos {s : Slice} {p₀ p₁ : s.Pos} {h} {p : (s.slice p₀ p₁ h).Pos}
     (h : p ≠ (s.slice p₀ p₁ h).endPos) : Pos.ofSlice p ≠ s.endPos := by
   refine (lt_endPos_iff _).1 (Std.lt_of_lt_of_le ?_ (le_endPos p₁))
   simpa [← lt_endPos_iff, ← ofSlice_lt_ofSlice_iff] using h
 
-theorem Slice.Pos.ne_endPos_of_slice_ne_endPos {s : Slice} {p p₀ p₁ : s.Pos} {h₁ h₂}
-    (h : Pos.slice p p₀ p₁ h₁ h₂ ≠ Slice.endPos _) : p ≠ s.endPos := by
-  rw [← Pos.ofSlice_slice (h₁ := h₁) (h₂ := h₂)]
-  apply Pos.ofSlice_ne_endPos h
-
-theorem Slice.Pos.ofSlice_ne_startPos {s : Slice} {p₀ p₁ : s.Pos} {h} {p : (s.slice p₀ p₁ h).Pos}
-    (h : p ≠ (s.slice p₀ p₁ h).startPos) : Pos.ofSlice p ≠ s.startPos := by
-  refine (startPos_lt_iff _).1 (Std.lt_of_le_of_lt (startPos_le p₀) ?_)
-  simpa [← startPos_lt_iff, ← ofSlice_lt_ofSlice_iff] using h
-
-theorem Slice.Pos.ne_startPos_of_slice_ne_startPos {s : Slice} {p p₀ p₁ : s.Pos} {h₁ h₂}
-    (h : Pos.slice p p₀ p₁ h₁ h₂ ≠ Slice.startPos _) : p ≠ s.startPos := by
-  rw [← Pos.ofSlice_slice (h₁ := h₁) (h₂ := h₂)]
-  apply Pos.ofSlice_ne_startPos h
-
 theorem Pos.ofSlice_ne_endPos {s : String} {p₀ p₁ : s.Pos} {h} {p : (s.slice p₀ p₁ h).Pos}
     (h : p ≠ (s.slice p₀ p₁ h).endPos) : Pos.ofSlice p ≠ s.endPos := by
   refine (lt_endPos_iff _).1 (Std.lt_of_lt_of_le ?_ (le_endPos p₁))
   simpa [← Slice.Pos.lt_endPos_iff, ← ofSlice_lt_ofSlice_iff] using h
 
-theorem Pos.ne_endPos_of_slice_ne_endPos {s : String} {p p₀ p₁ : s.Pos} {h₁ h₂}
-    (h : Pos.slice p p₀ p₁ h₁ h₂ ≠ Slice.endPos _) : p ≠ s.endPos := by
-  rw [← Pos.ofSlice_slice (h₁ := h₁) (h₂ := h₂)]
-  apply Pos.ofSlice_ne_endPos h
-
-theorem Pos.ofSlice_ne_startPos {s : String} {p₀ p₁ : s.Pos} {h} {p : (s.slice p₀ p₁ h).Pos}
-    (h : p ≠ (s.slice p₀ p₁ h).startPos) : Pos.ofSlice p ≠ s.startPos := by
-  refine (startPos_lt_iff _).1 (Std.lt_of_le_of_lt (startPos_le p₀) ?_)
-  simpa [← Slice.Pos.startPos_lt_iff, ← ofSlice_lt_ofSlice_iff] using h
-
-theorem Pos.ne_startPos_of_slice_ne_startPos {s : String} {p p₀ p₁ : s.Pos} {h₁ h₂}
-    (h : Pos.slice p p₀ p₁ h₁ h₂ ≠ Slice.startPos _) : p ≠ s.startPos := by
-  rw [← Pos.ofSlice_slice (h₁ := h₁) (h₂ := h₂)]
-  apply Pos.ofSlice_ne_startPos h
-
 @[simp]
 theorem Slice.Pos.offset_le_rawEndPos {s : Slice} {p : s.Pos} :
     p.offset ≤ s.rawEndPos :=
@@ -621,37 +468,21 @@ theorem Slice.Pos.get_eq_get_ofSliceTo {s : Slice} {p₀ : s.Pos} {pos : (s.slic
     pos.get h = (ofSliceTo pos).get (ofSliceTo_ne_endPos h) := by
   simp [Slice.Pos.get]
 
-theorem Slice.Pos.get_sliceTo {s : Slice} {p₀ p : s.Pos} {h h'} :
-    (Pos.sliceTo p₀ p h).get h' = p.get (ne_endPos_of_sliceTo_ne_endPos h') := by
-  simp [get_eq_get_ofSliceTo]
-
 theorem Pos.get_eq_get_ofSliceTo {s : String} {p₀ : s.Pos}
     {pos : (s.sliceTo p₀).Pos} {h} :
     pos.get h = (ofSliceTo pos).get (ofSliceTo_ne_endPos h) := by
   simp [Pos.get, Slice.Pos.get]
 
-theorem Pos.get_sliceTo {s : String} {p₀ p : s.Pos} {h h'} :
-    (Pos.sliceTo p₀ p h).get h' = p.get (ne_endPos_of_sliceTo_ne_endPos h') := by
-  simp [get_eq_get_ofSliceTo]
-
 theorem Slice.Pos.get_eq_get_ofSlice {s : Slice} {p₀ p₁ : s.Pos} {h}
     {pos : (s.slice p₀ p₁ h).Pos} {h'} :
     pos.get h' = (ofSlice pos).get (ofSlice_ne_endPos h') := by
   simp [Slice.Pos.get, Nat.add_assoc]
 
-theorem Slice.Pos.get_slice {s : Slice} {p p₀ p₁ : s.Pos} {h₁ h₂ h} :
-    (Pos.slice p p₀ p₁ h₁ h₂).get h = p.get (ne_endPos_of_slice_ne_endPos h) := by
-  simp [get_eq_get_ofSlice]
-
 theorem Pos.get_eq_get_ofSlice {s : String} {p₀ p₁ : s.Pos} {h}
     {pos : (s.slice p₀ p₁ h).Pos} {h'} :
     pos.get h' = (ofSlice pos).get (ofSlice_ne_endPos h') := by
   simp [Pos.get, Slice.Pos.get]
 
-theorem Pos.get_slice {s : String} {p p₀ p₁ : s.Pos} {h₁ h₂ h} :
-    (Pos.slice p p₀ p₁ h₁ h₂).get h = p.get (ne_endPos_of_slice_ne_endPos h) := by
-  simp [get_eq_get_ofSlice]
-
 theorem Slice.Pos.ofSlice_next {s : Slice} {p₀ p₁ : s.Pos} {h}
     {p : (s.slice p₀ p₁ h).Pos} {h'} :
     Pos.ofSlice (p.next h') = (Pos.ofSlice p).next (ofSlice_ne_endPos h') := by

src/Init/Data/String/Lemmas/Pattern/Char.lean

@@ -20,44 +20,28 @@ import Init.Data.String.Lemmas.Order
 import Init.Data.Order.Lemmas
 import Init.Data.String.OrderInstances
 import Init.Omega
-import Init.Data.String.Lemmas.FindPos
 
 public section
 
 namespace String.Slice.Pattern.Model.Char
 
-instance {c : Char} : PatternModel c where
+instance {c : Char} : ForwardPatternModel c where
   Matches s := s = String.singleton c
+  not_matches_empty := by simp
 
-instance {c : Char} : StrictPatternModel c where
-  not_matches_empty := by simp [PatternModel.Matches]
-
-instance {c : Char} : NoPrefixPatternModel c :=
-  .of_length_eq (by simp +contextual [PatternModel.Matches])
-
-instance {c : Char} : NoSuffixPatternModel c :=
-  .of_length_eq (by simp +contextual [PatternModel.Matches])
+instance {c : Char} : NoPrefixForwardPatternModel c :=
+  .of_length_eq (by simp +contextual [ForwardPatternModel.Matches])
 
 theorem isMatch_iff {c : Char} {s : Slice} {pos : s.Pos} :
     IsMatch c pos ↔
       ∃ (h : s.startPos ≠ s.endPos), pos = s.startPos.next h ∧ s.startPos.get h = c := by
-  simp only [Model.isMatch_iff, PatternModel.Matches, copy_sliceTo_eq_iff_exists_splits]
+  simp only [Model.isMatch_iff, ForwardPatternModel.Matches, sliceTo_copy_eq_iff_exists_splits]
   refine ⟨?_, ?_⟩
   · simp only [splits_singleton_iff]
     exact fun ⟨t₂, h, h₁, h₂, h₃⟩ => ⟨h, h₁, h₂⟩
   · rintro ⟨h, rfl, rfl⟩
     exact ⟨_, Slice.splits_next_startPos⟩
 
-theorem isRevMatch_iff {c : Char} {s : Slice} {pos : s.Pos} :
-    IsRevMatch c pos ↔
-      ∃ (h : s.endPos ≠ s.startPos), pos = s.endPos.prev h ∧ (s.endPos.prev h).get (by simp) = c := by
-  simp only [Model.isRevMatch_iff, PatternModel.Matches, copy_sliceFrom_eq_iff_exists_splits]
-  refine ⟨?_, ?_⟩
-  · simp only [splits_singleton_right_iff]
-    exact fun ⟨t₂, h, h₁, h₂, h₃⟩ => ⟨h, h₁, h₂⟩
-  · rintro ⟨h, rfl, rfl⟩
-    exact ⟨_, Slice.splits_prev_endPos⟩
-
 theorem isLongestMatch_iff {c : Char} {s : Slice} {pos : s.Pos} :
     IsLongestMatch c pos ↔
       ∃ (h : s.startPos ≠ s.endPos), pos = s.startPos.next h ∧ s.startPos.get h = c := by
@@ -68,46 +52,21 @@ theorem isLongestMatchAt_iff {c : Char} {s : Slice} {pos pos' : s.Pos} :
   simp +contextual [Model.isLongestMatchAt_iff, isLongestMatch_iff, ← Pos.ofSliceFrom_inj,
     Pos.get_eq_get_ofSliceFrom, Pos.ofSliceFrom_next]
 
-theorem isLongestRevMatch_iff {c : Char} {s : Slice} {pos : s.Pos} :
-    IsLongestRevMatch c pos ↔
-      ∃ (h : s.endPos ≠ s.startPos), pos = s.endPos.prev h ∧ (s.endPos.prev h).get (by simp) = c := by
-  rw [isLongestRevMatch_iff_isRevMatch, isRevMatch_iff]
-
-theorem isLongestRevMatchAt_iff {c : Char} {s : Slice} {pos pos' : s.Pos} :
-    IsLongestRevMatchAt c pos pos' ↔ ∃ h, pos = pos'.prev h ∧ (pos'.prev h).get (by simp) = c := by
-  simp +contextual [Model.isLongestRevMatchAt_iff, isLongestRevMatch_iff, ← Pos.ofSliceTo_inj,
-    Pos.get_eq_get_ofSliceTo, Pos.ofSliceTo_prev]
-
 theorem isLongestMatchAt_of_get_eq {c : Char} {s : Slice} {pos : s.Pos} {h : pos ≠ s.endPos}
     (hc : pos.get h = c) : IsLongestMatchAt c pos (pos.next h) :=
   isLongestMatchAt_iff.2 ⟨h, by simp [hc]⟩
 
-theorem isLongestRevMatchAt_of_get_eq {c : Char} {s : Slice} {pos : s.Pos} {h : pos ≠ s.startPos}
-    (hc : (pos.prev h).get (by simp) = c) : IsLongestRevMatchAt c (pos.prev h) pos :=
-  isLongestRevMatchAt_iff.2 ⟨h, by simp [hc]⟩
-
 instance {c : Char} : LawfulForwardPatternModel c where
   skipPrefix?_eq_some_iff {s} pos := by
     simp [isLongestMatch_iff, ForwardPattern.skipPrefix?, and_comm, eq_comm (b := pos)]
 
-instance {c : Char} : LawfulBackwardPatternModel c where
-  skipSuffix?_eq_some_iff {s} pos := by
-    simp [isLongestRevMatch_iff, BackwardPattern.skipSuffix?, and_comm, eq_comm (b := pos)]
-
 theorem toSearcher_eq {c : Char} {s : Slice} :
   ToForwardSearcher.toSearcher c s = ToForwardSearcher.toSearcher (· == c) s := (rfl)
 
-theorem toBackwardSearcher_eq {c : Char} {s : Slice} :
-  ToBackwardSearcher.toSearcher c s = ToBackwardSearcher.toSearcher (· == c) s := (rfl)
-
 theorem matchesAt_iff {c : Char} {s : Slice} {pos : s.Pos} :
     MatchesAt c pos ↔ ∃ (h : pos ≠ s.endPos), pos.get h = c := by
   simp [matchesAt_iff_exists_isLongestMatchAt, isLongestMatchAt_iff, exists_comm]
 
-theorem revMatchesAt_iff {c : Char} {s : Slice} {pos : s.Pos} :
-    RevMatchesAt c pos ↔ ∃ (h : pos ≠ s.startPos), (pos.prev h).get (by simp) = c := by
-  simp [revMatchesAt_iff_exists_isLongestRevMatchAt, isLongestRevMatchAt_iff, exists_comm]
-
 theorem matchesAt_iff_splits {c : Char} {s : Slice} {pos : s.Pos} :
     MatchesAt c pos ↔ ∃ t₁ t₂, pos.Splits t₁ (singleton c ++ t₂) := by
   rw [matchesAt_iff]
@@ -118,131 +77,37 @@ theorem matchesAt_iff_splits {c : Char} {s : Slice} {pos : s.Pos} :
     have hne := hs.ne_endPos_of_singleton
     exact ⟨hne, (singleton_append_inj.mp (hs.eq_right (pos.splits_next_right hne))).1.symm⟩
 
-theorem revMatchesAt_iff_splits {c : Char} {s : Slice} {pos : s.Pos} :
-    RevMatchesAt c pos ↔ ∃ t₁ t₂, pos.Splits (t₁ ++ singleton c) t₂ := by
-  rw [revMatchesAt_iff]
-  refine ⟨?_, ?_⟩
-  · rintro ⟨h, rfl⟩
-    exact ⟨_, _, pos.splits_prev_right h⟩
-  · rintro ⟨t₁, t₂, hs⟩
-    have hne := hs.ne_startPos_of_singleton
-    refine ⟨hne, ?_⟩
-    have := hs.eq_left (pos.splits_prev_right hne)
-    simp only [append_singleton, push_inj] at this
-    exact this.2.symm
-
 theorem not_matchesAt_of_get_ne {c : Char} {s : Slice} {pos : s.Pos} {h : pos ≠ s.endPos}
     (hc : pos.get h ≠ c) : ¬ MatchesAt c pos := by
   simp [matchesAt_iff, hc]
 
-theorem not_revMatchesAt_of_get_ne {c : Char} {s : Slice} {pos : s.Pos} {h : pos ≠ s.startPos}
-    (hc : (pos.prev h).get (by simp) ≠ c) : ¬ RevMatchesAt c pos := by
-  simp [revMatchesAt_iff, hc]
-
 theorem matchAt?_eq {s : Slice} {pos : s.Pos} {c : Char} :
     matchAt? c pos =
       if h₀ : ∃ (h : pos ≠ s.endPos), pos.get h = c then some (pos.next h₀.1) else none := by
   split <;> simp_all [isLongestMatchAt_iff, matchesAt_iff]
 
-theorem revMatchAt?_eq {s : Slice} {pos : s.Pos} {c : Char} :
-    revMatchAt? c pos =
-      if h₀ : ∃ (h : pos ≠ s.startPos), (pos.prev h).get (by simp) = c then some (pos.prev h₀.1) else none := by
-  split <;> simp_all [isLongestRevMatchAt_iff, revMatchesAt_iff]
-
 theorem isMatch_iff_isMatch_beq {c : Char} {s : Slice} {pos : s.Pos} :
     IsMatch c pos ↔ IsMatch (· == c) pos := by
   simp [isMatch_iff, CharPred.isMatch_iff, beq_iff_eq]
 
-theorem isRevMatch_iff_isRevMatch_beq {c : Char} {s : Slice} {pos : s.Pos} :
-    IsRevMatch c pos ↔ IsRevMatch (· == c) pos := by
-  simp [isRevMatch_iff, CharPred.isRevMatch_iff, beq_iff_eq]
-
 theorem isLongestMatch_iff_isLongestMatch_beq {c : Char} {s : Slice} {pos : s.Pos} :
     IsLongestMatch c pos ↔ IsLongestMatch (· == c) pos := by
   simp [isLongestMatch_iff_isMatch, isMatch_iff_isMatch_beq]
 
-theorem isLongestRevMatch_iff_isLongestRevMatch_beq {c : Char} {s : Slice} {pos : s.Pos} :
-    IsLongestRevMatch c pos ↔ IsLongestRevMatch (· == c) pos := by
-  simp [isLongestRevMatch_iff_isRevMatch, isRevMatch_iff_isRevMatch_beq]
-
 theorem isLongestMatchAt_iff_isLongestMatchAt_beq {c : Char} {s : Slice}
     {pos pos' : s.Pos} :
     IsLongestMatchAt c pos pos' ↔ IsLongestMatchAt (· == c) pos pos' := by
   simp [Model.isLongestMatchAt_iff, isLongestMatch_iff_isLongestMatch_beq]
 
-theorem isLongestMatchAtChain_iff_isLongestMatchAtChain_beq {c : Char} {s : Slice} {pos pos' : s.Pos} :
-    IsLongestMatchAtChain c pos pos' ↔ IsLongestMatchAtChain (· == c) pos pos' := by
-  refine ⟨fun h => ?_, fun h => ?_⟩
-  · induction h with
-    | nil => simp
-    | cons p₁ p₂ p₃ h₁ h₂ ih => exact .cons _ _ _ (isLongestMatchAt_iff_isLongestMatchAt_beq.1 h₁) ih
-  · induction h with
-    | nil => simp
-    | cons p₁ p₂ p₃ h₁ h₂ ih => exact .cons _ _ _ (isLongestMatchAt_iff_isLongestMatchAt_beq.2 h₁) ih
-
-theorem isLongestMatchAtChain_iff {c : Char} {s : Slice} {pos pos' : s.Pos} :
-    IsLongestMatchAtChain c pos pos' ↔ pos ≤ pos' ∧ ∀ pos'', pos ≤ pos'' → (h : pos'' < pos') → pos''.get (Pos.ne_endPos_of_lt h) = c := by
-  simp [isLongestMatchAtChain_iff_isLongestMatchAtChain_beq, CharPred.isLongestMatchAtChain_iff]
-
-theorem isLongestMatchAtChain_iff_toList {c : Char} {s : Slice} {pos pos' : s.Pos} :
-    IsLongestMatchAtChain c pos pos' ↔
-      ∃ (h : pos ≤ pos'), (s.slice pos pos' h).copy.toList = List.replicate (s.slice pos pos' h).copy.length c := by
-  simp [isLongestMatchAtChain_iff_isLongestMatchAtChain_beq, CharPred.isLongestMatchAtChain_iff_toList,
-    List.eq_replicate_iff]
-
-theorem isLongestMatchAtChain_startPos_endPos_iff_toList {c : Char} {s : Slice} :
-    IsLongestMatchAtChain c s.startPos s.endPos ↔ s.copy.toList = List.replicate s.copy.length c := by
-  simp [isLongestMatchAtChain_iff_isLongestMatchAtChain_beq,
-    CharPred.isLongestMatchAtChain_startPos_endPos_iff_toList, List.eq_replicate_iff]
-
-theorem isLongestRevMatchAt_iff_isLongestRevMatchAt_beq {c : Char} {s : Slice}
-    {pos pos' : s.Pos} :
-    IsLongestRevMatchAt c pos pos' ↔ IsLongestRevMatchAt (· == c) pos pos' := by
-  simp [Model.isLongestRevMatchAt_iff, isLongestRevMatch_iff_isLongestRevMatch_beq]
-
-theorem isLongestRevMatchAtChain_iff_isLongestRevMatchAtChain_beq {c : Char} {s : Slice} {pos pos' : s.Pos} :
-    IsLongestRevMatchAtChain c pos pos' ↔ IsLongestRevMatchAtChain (· == c) pos pos' := by
-  refine ⟨fun h => ?_, fun h => ?_⟩
-  · induction h with
-    | nil => simp
-    | cons p₂ p₃ _ hmatch ih => exact .cons _ _ _ ih (isLongestRevMatchAt_iff_isLongestRevMatchAt_beq.1 hmatch)
-  · induction h with
-    | nil => simp
-    | cons p₂ p₃ _ hmatch ih => exact .cons _ _ _ ih (isLongestRevMatchAt_iff_isLongestRevMatchAt_beq.2 hmatch)
-
-theorem isLongestRevMatchAtChain_iff {c : Char} {s : Slice} {pos pos' : s.Pos} :
-    IsLongestRevMatchAtChain c pos pos' ↔ pos ≤ pos' ∧ ∀ pos'', pos ≤ pos'' → (h : pos'' < pos') → pos''.get (Pos.ne_endPos_of_lt h) = c := by
-  simp [isLongestRevMatchAtChain_iff_isLongestRevMatchAtChain_beq, CharPred.isLongestRevMatchAtChain_iff]
-
-theorem isLongestRevMatchAtChain_iff_toList {c : Char} {s : Slice} {pos pos' : s.Pos} :
-    IsLongestRevMatchAtChain c pos pos' ↔
-      ∃ (h : pos ≤ pos'), (s.slice pos pos' h).copy.toList = List.replicate (s.slice pos pos' h).copy.length c := by
-  simp [isLongestRevMatchAtChain_iff_isLongestRevMatchAtChain_beq, CharPred.isLongestRevMatchAtChain_iff_toList,
-    List.eq_replicate_iff]
-
-theorem isLongestRevMatchAtChain_startPos_endPos_iff_toList {c : Char} {s : Slice} :
-    IsLongestRevMatchAtChain c s.startPos s.endPos ↔ s.copy.toList = List.replicate s.copy.length c := by
-  simp [isLongestRevMatchAtChain_iff_isLongestRevMatchAtChain_beq,
-    CharPred.isLongestRevMatchAtChain_startPos_endPos_iff_toList, List.eq_replicate_iff]
-
 theorem matchesAt_iff_matchesAt_beq {c : Char} {s : Slice} {pos : s.Pos} :
     MatchesAt c pos ↔ MatchesAt (· == c) pos := by
   simp [matchesAt_iff_exists_isLongestMatchAt, isLongestMatchAt_iff_isLongestMatchAt_beq]
 
-theorem revMatchesAt_iff_revMatchesAt_beq {c : Char} {s : Slice} {pos : s.Pos} :
-    RevMatchesAt c pos ↔ RevMatchesAt (· == c) pos := by
-  simp [revMatchesAt_iff_exists_isLongestRevMatchAt, isLongestRevMatchAt_iff_isLongestRevMatchAt_beq]
-
 theorem matchAt?_eq_matchAt?_beq {c : Char} {s : Slice} {pos : s.Pos} :
     matchAt? c pos = matchAt? (· == c) pos := by
   refine Option.ext (fun pos' => ?_)
   simp [matchAt?_eq_some_iff, isLongestMatchAt_iff_isLongestMatchAt_beq]
 
-theorem revMatchAt?_eq_revMatchAt?_beq {c : Char} {s : Slice} {pos : s.Pos} :
-    revMatchAt? c pos = revMatchAt? (· == c) pos := by
-  refine Option.ext (fun pos' => ?_)
-  simp [revMatchAt?_eq_some_iff, isLongestRevMatchAt_iff_isLongestRevMatchAt_beq]
-
 theorem isValidSearchFrom_iff_isValidSearchFrom_beq {c : Char} {s : Slice} {p : s.Pos}
     {l : List (SearchStep s)} : IsValidSearchFrom c p l ↔ IsValidSearchFrom (· == c) p l := by
   refine ⟨fun h => ?_, fun h => ?_⟩
@@ -255,28 +120,11 @@ theorem isValidSearchFrom_iff_isValidSearchFrom_beq {c : Char} {s : Slice} {p :
     | matched => simp_all [IsValidSearchFrom.matched, isLongestMatchAt_iff_isLongestMatchAt_beq]
     | mismatched => simp_all [IsValidSearchFrom.mismatched, matchesAt_iff_matchesAt_beq]
 
-theorem isValidRevSearchFrom_iff_isValidRevSearchFrom_beq {c : Char} {s : Slice} {p : s.Pos}
-    {l : List (SearchStep s)} : IsValidRevSearchFrom c p l ↔ IsValidRevSearchFrom (· == c) p l := by
-  refine ⟨fun h => ?_, fun h => ?_⟩
-  · induction h with
-    | startPos => simpa using IsValidRevSearchFrom.startPos
-    | matched => simp_all [IsValidRevSearchFrom.matched, isLongestRevMatchAt_iff_isLongestRevMatchAt_beq]
-    | mismatched => simp_all [IsValidRevSearchFrom.mismatched, revMatchesAt_iff_revMatchesAt_beq]
-  · induction h with
-    | startPos => simpa using IsValidRevSearchFrom.startPos
-    | matched => simp_all [IsValidRevSearchFrom.matched, isLongestRevMatchAt_iff_isLongestRevMatchAt_beq]
-    | mismatched => simp_all [IsValidRevSearchFrom.mismatched, revMatchesAt_iff_revMatchesAt_beq]
-
 instance {c : Char} : LawfulToForwardSearcherModel c where
   isValidSearchFrom_toList s := by
     simpa [toSearcher_eq, isValidSearchFrom_iff_isValidSearchFrom_beq] using
       LawfulToForwardSearcherModel.isValidSearchFrom_toList (pat := (· == c)) (s := s)
 
-instance {c : Char} : LawfulToBackwardSearcherModel c where
-  isValidRevSearchFrom_toList s := by
-    simpa [toBackwardSearcher_eq, isValidRevSearchFrom_iff_isValidRevSearchFrom_beq] using
-      LawfulToBackwardSearcherModel.isValidRevSearchFrom_toList (pat := (· == c)) (s := s)
-
 end Pattern.Model.Char
 
 theorem startsWith_char_eq_startsWith_beq {c : Char} {s : Slice} :
@@ -294,21 +142,18 @@ theorem skipPrefix?_char_eq_skipPrefix?_beq {c : Char} {s : Slice} :
 theorem Pattern.ForwardPattern.skipPrefix?_char_eq_skipPrefix?_beq {c : Char} {s : Slice} :
     skipPrefix? c s = skipPrefix? (· == c) s := (rfl)
 
-theorem Pos.skip?_char_eq_skip?_beq {c : Char} {s : Slice} {pos : s.Pos} :
-    pos.skip? c = pos.skip? (· == c) := (rfl)
-
 theorem Pos.skipWhile_char_eq_skipWhile_beq {c : Char} {s : Slice} (curr : s.Pos) :
     Pos.skipWhile curr c = Pos.skipWhile curr (· == c) := by
   fun_induction Pos.skipWhile curr c with
   | case1 pos nextCurr h₁ h₂ ih =>
     conv => rhs; rw [Pos.skipWhile]
-    simp [← Pos.skip?_char_eq_skip?_beq, h₁, h₂, ih]
+    simp [← Pattern.ForwardPattern.skipPrefix?_char_eq_skipPrefix?_beq, h₁, h₂, ih]
   | case2 pos nextCurr h ih =>
     conv => rhs; rw [Pos.skipWhile]
-    simp [← Pos.skip?_char_eq_skip?_beq, h, ih]
+    simp [← Pattern.ForwardPattern.skipPrefix?_char_eq_skipPrefix?_beq, h, ih]
   | case3 pos h =>
     conv => rhs; rw [Pos.skipWhile]
-    simp [← Pos.skip?_char_eq_skip?_beq, h]
+    simp [← Pattern.ForwardPattern.skipPrefix?_char_eq_skipPrefix?_beq]
 
 theorem skipPrefixWhile_char_eq_skipPrefixWhile_beq {c : Char} {s : Slice} :
     s.skipPrefixWhile c = s.skipPrefixWhile (· == c) :=
@@ -324,7 +169,7 @@ theorem takeWhile_char_eq_takeWhile_beq {c : Char} {s : Slice} :
 
 theorem all_char_eq_all_beq {c : Char} {s : Slice} :
     s.all c = s.all (· == c) := by
-  simp only [all, skipPrefixWhile_char_eq_skipPrefixWhile_beq]
+  simp only [all, dropWhile_char_eq_dropWhile_beq]
 
 theorem find?_char_eq_find?_beq {c : Char} {s : Slice} :
     s.find? c = s.find? (· == c) :=
@@ -353,21 +198,18 @@ theorem dropSuffix_char_eq_dropSuffix_beq {c : Char} {s : Slice} :
 theorem Pattern.BackwardPattern.skipSuffix?_char_eq_skipSuffix?_beq {c : Char} {s : Slice} :
     skipSuffix? c s = skipSuffix? (· == c) s := (rfl)
 
-theorem Pos.revSkip?_char_eq_revSkip?_beq {c : Char} {s : Slice} {pos : s.Pos} :
-    pos.revSkip? c = pos.revSkip? (· == c) := (rfl)
-
 theorem Pos.revSkipWhile_char_eq_revSkipWhile_beq {c : Char} {s : Slice} (curr : s.Pos) :
     Pos.revSkipWhile curr c = Pos.revSkipWhile curr (· == c) := by
   fun_induction Pos.revSkipWhile curr c with
   | case1 pos nextCurr h₁ h₂ ih =>
     conv => rhs; rw [Pos.revSkipWhile]
-    simp [← Pos.revSkip?_char_eq_revSkip?_beq, h₁, h₂, ih]
+    simp [← Pattern.BackwardPattern.skipSuffix?_char_eq_skipSuffix?_beq, h₁, h₂, ih]
   | case2 pos nextCurr h ih =>
     conv => rhs; rw [Pos.revSkipWhile]
-    simp [← Pos.revSkip?_char_eq_revSkip?_beq, h, ih]
+    simp [← Pattern.BackwardPattern.skipSuffix?_char_eq_skipSuffix?_beq, h, ih]
   | case3 pos h =>
     conv => rhs; rw [Pos.revSkipWhile]
-    simp [← Pos.revSkip?_char_eq_revSkip?_beq, h]
+    simp [← Pattern.BackwardPattern.skipSuffix?_char_eq_skipSuffix?_beq]
 
 theorem skipSuffixWhile_char_eq_skipSuffixWhile_beq {c : Char} {s : Slice} :
     s.skipSuffixWhile c = s.skipSuffixWhile (· == c) :=
@@ -381,16 +223,4 @@ theorem takeEndWhile_char_eq_takeEndWhile_beq {c : Char} {s : Slice} :
     s.takeEndWhile c = s.takeEndWhile (· == c) := by
   simp only [takeEndWhile]; exact congrArg _ skipSuffixWhile_char_eq_skipSuffixWhile_beq
 
-theorem revFind?_char_eq_revFind?_beq {c : Char} {s : Slice} :
-    s.revFind? c = s.revFind? (· == c) :=
-  (rfl)
-
-theorem Pos.revFind?_char_eq_revFind?_beq {c : Char} {s : Slice} {p : s.Pos} :
-    p.revFind? c = p.revFind? (· == c) :=
-  (rfl)
-
-theorem revAll_char_eq_revAll_beq {c : Char} {s : Slice} :
-    s.revAll c = s.revAll (· == c) := by
-  simp [revAll, skipSuffixWhile_char_eq_skipSuffixWhile_beq]
-
 end String.Slice

src/Init/Data/String/Lemmas/Pattern/Find/Basic.lean

@@ -23,8 +23,8 @@ open Std String.Slice Pattern Pattern.Model
 
 namespace String.Slice
 
-theorem Pattern.Model.find?_eq_some_iff {ρ : Type} (pat : ρ) [PatternModel pat] [StrictPatternModel pat]
-    {σ : Slice → Type} [∀ s, Iterator (σ s) Id (SearchStep s)] [∀ s, Iterators.Finite (σ s) Id]
+theorem Pattern.Model.find?_eq_some_iff {ρ : Type} (pat : ρ) [ForwardPatternModel pat] {σ : Slice → Type}
+    [∀ s, Iterator (σ s) Id (SearchStep s)] [∀ s, Iterators.Finite (σ s) Id]
     [∀ s, IteratorLoop (σ s) Id Id] [∀ s, LawfulIteratorLoop (σ s) Id Id]
     [ToForwardSearcher pat σ] [LawfulToForwardSearcherModel pat] {s : Slice} {pos : s.Pos} :
     s.find? pat = some pos ↔ MatchesAt pat pos ∧ (∀ pos', pos' < pos → ¬ MatchesAt pat pos') := by
@@ -40,8 +40,8 @@ theorem Pattern.Model.find?_eq_some_iff {ρ : Type} (pat : ρ) [PatternModel pat
   | matched h₁ _ _ => have := h₁.matchesAt; grind
   | mismatched => grind
 
-theorem Pattern.Model.find?_eq_none_iff {ρ : Type} (pat : ρ) [PatternModel pat] [StrictPatternModel pat]
-    {σ : Slice → Type} [∀ s, Iterator (σ s) Id (SearchStep s)] [∀ s, Iterators.Finite (σ s) Id]
+theorem Pattern.Model.find?_eq_none_iff {ρ : Type} (pat : ρ) [ForwardPatternModel pat] {σ : Slice → Type}
+    [∀ s, Iterator (σ s) Id (SearchStep s)] [∀ s, Iterators.Finite (σ s) Id]
     [∀ s, IteratorLoop (σ s) Id Id] [∀ s, LawfulIteratorLoop (σ s) Id Id]
     [ToForwardSearcher pat σ] [LawfulToForwardSearcherModel pat] {s : Slice} :
     s.find? pat = none ↔ ∀ (pos : s.Pos), ¬ MatchesAt pat pos := by
@@ -65,15 +65,15 @@ theorem find?_eq_none_iff {ρ : Type} (pat : ρ) {σ : Slice → Type}
     [ToForwardSearcher pat σ] {s : Slice} : s.find? pat = none ↔ s.contains pat = false := by
   rw [← Option.isNone_iff_eq_none, ← Option.isSome_eq_false_iff, isSome_find?]
 
-theorem Pattern.Model.contains_eq_false_iff {ρ : Type} (pat : ρ) [PatternModel pat] [StrictPatternModel pat]
-    {σ : Slice → Type} [∀ s, Iterator (σ s) Id (SearchStep s)] [∀ s, Iterators.Finite (σ s) Id]
+theorem Pattern.Model.contains_eq_false_iff {ρ : Type} (pat : ρ) [ForwardPatternModel pat] {σ : Slice → Type}
+    [∀ s, Iterator (σ s) Id (SearchStep s)] [∀ s, Iterators.Finite (σ s) Id]
     [∀ s, IteratorLoop (σ s) Id Id] [∀ s, LawfulIteratorLoop (σ s) Id Id]
     [ToForwardSearcher pat σ] [LawfulToForwardSearcherModel pat] {s : Slice} :
     s.contains pat = false ↔ ∀ (pos : s.Pos), ¬ MatchesAt pat pos := by
   rw [← find?_eq_none_iff, Slice.find?_eq_none_iff]
 
-theorem Pattern.Model.contains_eq_true_iff {ρ : Type} (pat : ρ) [PatternModel pat] [StrictPatternModel pat]
-    {σ : Slice → Type} [∀ s, Iterator (σ s) Id (SearchStep s)] [∀ s, Iterators.Finite (σ s) Id]
+theorem Pattern.Model.contains_eq_true_iff {ρ : Type} (pat : ρ) [ForwardPatternModel pat] {σ : Slice → Type}
+    [∀ s, Iterator (σ s) Id (SearchStep s)] [∀ s, Iterators.Finite (σ s) Id]
     [∀ s, IteratorLoop (σ s) Id Id] [∀ s, LawfulIteratorLoop (σ s) Id Id]
     [ToForwardSearcher pat σ] [LawfulToForwardSearcherModel pat] {s : Slice} :
     s.contains pat ↔ ∃ (pos : s.Pos), MatchesAt pat pos := by
@@ -85,7 +85,7 @@ theorem Pos.find?_eq_find?_sliceFrom {ρ : Type} {pat : ρ} {σ : Slice → Type
     p.find? pat = ((s.sliceFrom p).find? pat).map Pos.ofSliceFrom :=
   (rfl)
 
-theorem Pattern.Model.posFind?_eq_some_iff {ρ : Type} {pat : ρ} [PatternModel pat] [StrictPatternModel pat] {σ : Slice → Type}
+theorem Pattern.Model.posFind?_eq_some_iff {ρ : Type} {pat : ρ} [ForwardPatternModel pat] {σ : Slice → Type}
     [∀ s, Iterator (σ s) Id (SearchStep s)] [∀ s, Iterators.Finite (σ s) Id]
     [∀ s, IteratorLoop (σ s) Id Id] [∀ s, LawfulIteratorLoop (σ s) Id Id]
     [ToForwardSearcher pat σ] [LawfulToForwardSearcherModel pat] {s : Slice} {pos pos' : s.Pos} :
@@ -100,8 +100,8 @@ theorem Pattern.Model.posFind?_eq_some_iff {ρ : Type} {pat : ρ} [PatternModel
     refine ⟨Pos.sliceFrom _ _ h₁, ⟨by simpa using h₂, fun p hp₁ hp₂ => ?_⟩, by simp⟩
     exact h₃ (Pos.ofSliceFrom p) Slice.Pos.le_ofSliceFrom (Pos.lt_sliceFrom_iff.1 hp₁) hp₂
 
-theorem Pattern.Model.posFind?_eq_none_iff {ρ : Type} {pat : ρ} [PatternModel pat] [StrictPatternModel pat]
-    {σ : Slice → Type} [∀ s, Iterator (σ s) Id (SearchStep s)] [∀ s, Iterators.Finite (σ s) Id]
+theorem Pattern.Model.posFind?_eq_none_iff {ρ : Type} {pat : ρ} [ForwardPatternModel pat] {σ : Slice → Type}
+    [∀ s, Iterator (σ s) Id (SearchStep s)] [∀ s, Iterators.Finite (σ s) Id]
     [∀ s, IteratorLoop (σ s) Id Id] [∀ s, LawfulIteratorLoop (σ s) Id Id]
     [ToForwardSearcher pat σ] [LawfulToForwardSearcherModel pat] {s : Slice} {pos : s.Pos} :
     pos.find? pat = none ↔ ∀ pos', pos ≤ pos' → ¬ MatchesAt pat pos' := by

src/Init/Data/String/Lemmas/Pattern/Find/String.lean

@@ -49,10 +49,9 @@ theorem contains_slice_iff {t s : Slice} :
   by_cases ht : t.isEmpty
   · simp [contains_eq_true_of_isEmpty ht s, copy_eq_empty_iff.mpr ht, String.toList_empty]
   · simp only [Bool.not_eq_true] at ht
-    have := Pattern.Model.ForwardSliceSearcher.strictPatternModel ht
     have := Pattern.Model.ForwardSliceSearcher.lawfulToForwardSearcherModel ht
     simp only [Pattern.Model.contains_eq_true_iff,
-      Pattern.Model.ForwardSliceSearcher.exists_matchesAt_iff_eq_append, isInfix_toList_iff]
+      Pattern.Model.ForwardSliceSearcher.exists_matchesAt_iff_eq_append ht, isInfix_toList_iff]
 
 @[simp]
 theorem contains_string_iff {t : String} {s : Slice} :

src/Init/Data/String/Lemmas/Pattern/Pred.lean

@@ -18,321 +18,125 @@ import Init.Data.String.Lemmas.Basic
 import Init.Data.String.Lemmas.Order
 import Init.Data.Order.Lemmas
 import Init.Data.String.OrderInstances
-import Init.Data.String.Lemmas.Iterate
 import Init.Omega
-import Init.Data.String.Lemmas.FindPos
 
 public section
 
 namespace String.Slice.Pattern.Model.CharPred
 
-instance {p : Char → Bool} : PatternModel p where
+instance {p : Char → Bool} : ForwardPatternModel p where
   Matches s := ∃ c, s = singleton c ∧ p c
+  not_matches_empty := by
+    simp
 
-instance {p : Char → Bool} : StrictPatternModel p where
-  not_matches_empty := by simp [PatternModel.Matches]
-
-instance {p : Char → Bool} : NoPrefixPatternModel p :=
-  .of_length_eq (by simp +contextual [PatternModel.Matches])
-
-instance {p : Char → Bool} : NoSuffixPatternModel p :=
-  .of_length_eq (by simp +contextual [PatternModel.Matches])
+instance {p : Char → Bool} : NoPrefixForwardPatternModel p :=
+  .of_length_eq (by simp +contextual [ForwardPatternModel.Matches])
 
 theorem isMatch_iff {p : Char → Bool} {s : Slice} {pos : s.Pos} :
     IsMatch p pos ↔
       ∃ (h : s.startPos ≠ s.endPos), pos = s.startPos.next h ∧ p (s.startPos.get h) := by
-  simp only [Model.isMatch_iff, PatternModel.Matches, copy_sliceTo_eq_iff_exists_splits]
+  simp only [Model.isMatch_iff, ForwardPatternModel.Matches, sliceTo_copy_eq_iff_exists_splits]
   refine ⟨?_, ?_⟩
   · simp only [splits_singleton_iff]
     refine fun ⟨c, ⟨t₂, h, h₁, h₂, h₃⟩, hc⟩ => ⟨h, h₁, h₂ ▸ hc⟩
   · rintro ⟨h, rfl, h'⟩
     exact ⟨s.startPos.get h, ⟨_, Slice.splits_next_startPos⟩, h'⟩
 
-theorem isRevMatch_iff {p : Char → Bool} {s : Slice} {pos : s.Pos} :
-    IsRevMatch p pos ↔
-      ∃ (h : s.endPos ≠ s.startPos), pos = s.endPos.prev h ∧ p ((s.endPos.prev h).get (by simp)) := by
-  simp only [Model.isRevMatch_iff, PatternModel.Matches, copy_sliceFrom_eq_iff_exists_splits]
-  refine ⟨?_, ?_⟩
-  · simp only [splits_singleton_right_iff]
-    refine fun ⟨c, ⟨t₂, h, h₁, h₂, h₃⟩, hc⟩ => ⟨h, h₁, h₂ ▸ hc⟩
-  · rintro ⟨h, rfl, h'⟩
-    exact ⟨(s.endPos.prev h).get (by simp), ⟨_, Slice.splits_prev_endPos⟩, h'⟩
-
 theorem isLongestMatch_iff {p : Char → Bool} {s : Slice} {pos : s.Pos} :
     IsLongestMatch p pos ↔
       ∃ (h : s.startPos ≠ s.endPos), pos = s.startPos.next h ∧ p (s.startPos.get h) := by
   rw [isLongestMatch_iff_isMatch, isMatch_iff]
 
-theorem isLongestRevMatch_iff {p : Char → Bool} {s : Slice} {pos : s.Pos} :
-    IsLongestRevMatch p pos ↔
-      ∃ (h : s.endPos ≠ s.startPos), pos = s.endPos.prev h ∧ p ((s.endPos.prev h).get (by simp)) := by
-  rw [isLongestRevMatch_iff_isRevMatch, isRevMatch_iff]
-
 theorem isLongestMatchAt_iff {p : Char → Bool} {s : Slice} {pos pos' : s.Pos} :
     IsLongestMatchAt p pos pos' ↔ ∃ h, pos' = pos.next h ∧ p (pos.get h) := by
   simp +contextual [Model.isLongestMatchAt_iff, isLongestMatch_iff, ← Pos.ofSliceFrom_inj,
     Pos.get_eq_get_ofSliceFrom, Pos.ofSliceFrom_next]
 
-theorem isLongestMatchAtChain_iff {p : Char → Bool} {s : Slice} {pos pos' : s.Pos} :
-    IsLongestMatchAtChain p pos pos' ↔ pos ≤ pos' ∧ ∀ pos'', pos ≤ pos'' → (h : pos'' < pos') → p (pos''.get (Pos.ne_endPos_of_lt h)) := by
-  induction pos using WellFounded.induction Pos.wellFounded_gt with | h pos ih
-  obtain (h|rfl|h) := Std.lt_trichotomy pos pos'
-  · refine ⟨fun h => ?_, fun ⟨h₁, h₂⟩ => ?_⟩
-    · cases h with
-      | nil => exact (Std.lt_irrefl h).elim
-      | cons _ mid _ h₁ h₂ =>
-        obtain ⟨h₀, rfl, h₁'⟩ := isLongestMatchAt_iff.1 h₁
-        refine ⟨Std.le_of_lt h, fun pos'' hp₁ hp₂ => ?_⟩
-        obtain (hh|rfl) := Std.le_iff_lt_or_eq.1 hp₁
-        · exact ((ih (pos.next (Pos.ne_endPos_of_lt h)) Pos.lt_next).1 h₂).2 _ (by simpa) hp₂
-        · exact h₁'
-    · refine .cons _ (pos.next (Pos.ne_endPos_of_lt h)) _ ?_ ((ih _ Pos.lt_next).2 ?_)
-      · exact isLongestMatchAt_iff.2 ⟨Pos.ne_endPos_of_lt h, rfl, h₂ _ (by simp) h⟩
-      · exact ⟨by simpa, fun pos'' hp₁ hp₂ => h₂ _ (Std.le_trans Pos.le_next hp₁) hp₂⟩
-  · simpa using fun _ h₁ h₂ => (Std.lt_irrefl (Std.lt_of_le_of_lt h₁ h₂)).elim
-  · simpa [Std.not_le.2 h] using fun h' => (Std.not_le.2 h h'.le).elim
-
-theorem isLongestMatchAtChain_iff_toList {p : Char → Bool} {s : Slice} {pos pos' : s.Pos} :
-    IsLongestMatchAtChain p pos pos' ↔ ∃ (h : pos ≤ pos'), ∀ c, c ∈ (s.slice pos pos' h).copy.toList → p c := by
-  simp only [isLongestMatchAtChain_iff, mem_toList_copy_iff_exists_get, Pos.get_eq_get_ofSlice,
-    forall_exists_index]
-  refine ⟨fun ⟨h₁, h₂⟩ => ⟨h₁, fun c p' hp => ?_⟩, fun ⟨h₁, h₂⟩ => ⟨h₁, fun p' hp₁ hp₂ => ?_⟩⟩
-  · rintro rfl
-    exact h₂ _ Pos.le_ofSlice (by simp [Pos.ofSlice_lt_iff, h₁, hp])
-  · refine h₂ _ (Pos.slice p' _ _ hp₁ (Std.le_of_lt hp₂)) ?_ (by simp)
-    rwa [← Pos.lt_endPos_iff, ← Pos.slice_eq_endPos (h := h₁), Pos.slice_lt_slice_iff]
-
-theorem isLongestMatchAtChain_startPos_endPos_iff_toList {p : Char → Bool} {s : Slice} :
-    IsLongestMatchAtChain p s.startPos s.endPos ↔ ∀ c, c ∈ s.copy.toList → p c := by
-  simp [isLongestMatchAtChain_iff_toList]
-
-theorem isLongestRevMatchAt_iff {p : Char → Bool} {s : Slice} {pos pos' : s.Pos} :
-    IsLongestRevMatchAt p pos pos' ↔ ∃ h, pos = pos'.prev h ∧ p ((pos'.prev h).get (by simp)) := by
-  simp +contextual [Model.isLongestRevMatchAt_iff, isLongestRevMatch_iff, ← Pos.ofSliceTo_inj,
-    Pos.get_eq_get_ofSliceTo, Pos.ofSliceTo_prev]
-
 theorem isLongestMatchAt_of_get {p : Char → Bool} {s : Slice} {pos : s.Pos} {h : pos ≠ s.endPos}
     (hc : p (pos.get h)) : IsLongestMatchAt p pos (pos.next h) :=
   isLongestMatchAt_iff.2 ⟨h, by simp [hc]⟩
 
-theorem isLongestRevMatchAt_of_get {p : Char → Bool} {s : Slice} {pos : s.Pos} {h : pos ≠ s.startPos}
-    (hc : p ((pos.prev h).get (by simp))) : IsLongestRevMatchAt p (pos.prev h) pos :=
-  isLongestRevMatchAt_iff.2 ⟨h, by simp [hc]⟩
-
-theorem isLongestRevMatchAtChain_iff {p : Char → Bool} {s : Slice} {pos pos' : s.Pos} :
-    IsLongestRevMatchAtChain p pos pos' ↔ pos ≤ pos' ∧ ∀ pos'', pos ≤ pos'' → (h : pos'' < pos') → p (pos''.get (Pos.ne_endPos_of_lt h)) := by
-  induction pos' using WellFounded.induction Pos.wellFounded_lt with | h pos' ih
-  obtain (h|rfl|h) := Std.lt_trichotomy pos pos'
-  · refine ⟨fun h => ?_, fun ⟨h₁, h₂⟩ => ?_⟩
-    · cases h with
-      | nil => exact (Std.lt_irrefl h).elim
-      | cons _ _ hchain hmatch =>
-        obtain ⟨hne, hmid, hp⟩ := isLongestRevMatchAt_iff.1 hmatch
-        refine ⟨Std.le_of_lt h, fun pos'' hp₁ hp₂ => ?_⟩
-        rcases Std.le_iff_lt_or_eq.1 (Pos.le_prev_iff_lt.2 hp₂) with hh | heq
-        · exact ((ih _ Pos.prev_lt).1 (hmid ▸ hchain)).2 _ hp₁ hh
-        · exact heq ▸ hp
-    · have hne : pos' ≠ s.startPos := Slice.Pos.ne_startPos_of_lt h
-      refine .cons _ (pos'.prev hne) _ ((ih _ Pos.prev_lt).2 ?_)
-        (isLongestRevMatchAt_of_get (h₂ _ (Pos.le_prev_iff_lt.2 h) Pos.prev_lt))
-      exact ⟨Pos.le_prev_iff_lt.2 h, fun pos'' hp₁ hp₂ =>
-        h₂ _ hp₁ (Std.lt_trans hp₂ Pos.prev_lt)⟩
-  · simpa using fun _ h₁ h₂ => (Std.lt_irrefl (Std.lt_of_le_of_lt h₁ h₂)).elim
-  · simpa [Std.not_le.2 h] using fun h' => (Std.not_le.2 h h'.le).elim
-
-theorem isLongestRevMatchAtChain_iff_toList {p : Char → Bool} {s : Slice} {pos pos' : s.Pos} :
-    IsLongestRevMatchAtChain p pos pos' ↔ ∃ (h : pos ≤ pos'), ∀ c, c ∈ (s.slice pos pos' h).copy.toList → p c :=
-  isLongestRevMatchAtChain_iff.trans (isLongestMatchAtChain_iff.symm.trans isLongestMatchAtChain_iff_toList)
-
-theorem isLongestRevMatchAtChain_startPos_endPos_iff_toList {p : Char → Bool} {s : Slice} :
-    IsLongestRevMatchAtChain p s.startPos s.endPos ↔ ∀ c, c ∈ s.copy.toList → p c := by
-  simp [isLongestRevMatchAtChain_iff_toList]
-
 instance {p : Char → Bool} : LawfulForwardPatternModel p where
   skipPrefix?_eq_some_iff {s} pos := by
     simp [isLongestMatch_iff, ForwardPattern.skipPrefix?, and_comm, eq_comm (b := pos)]
 
-instance {p : Char → Bool} : LawfulBackwardPatternModel p where
-  skipSuffix?_eq_some_iff {s} pos := by
-    simp [isLongestRevMatch_iff, BackwardPattern.skipSuffix?, and_comm, eq_comm (b := pos)]
-
 instance {p : Char → Bool} : LawfulToForwardSearcherModel p :=
   .defaultImplementation
 
-instance {p : Char → Bool} : LawfulToBackwardSearcherModel p :=
-  .defaultImplementation
-
 theorem matchesAt_iff {p : Char → Bool} {s : Slice} {pos : s.Pos} :
     MatchesAt p pos ↔ ∃ (h : pos ≠ s.endPos), p (pos.get h) := by
   simp [matchesAt_iff_exists_isLongestMatchAt, isLongestMatchAt_iff, exists_comm]
 
-theorem revMatchesAt_iff {p : Char → Bool} {s : Slice} {pos : s.Pos} :
-    RevMatchesAt p pos ↔ ∃ (h : pos ≠ s.startPos), p ((pos.prev h).get (by simp)) := by
-  simp [revMatchesAt_iff_exists_isLongestRevMatchAt, isLongestRevMatchAt_iff, exists_comm]
-
 theorem not_matchesAt_of_get {p : Char → Bool} {s : Slice} {pos : s.Pos} {h : pos ≠ s.endPos}
     (hc : p (pos.get h) = false) : ¬ MatchesAt p pos := by
   simp [matchesAt_iff, hc]
 
-theorem not_revMatchesAt_of_get {p : Char → Bool} {s : Slice} {pos : s.Pos} {h : pos ≠ s.startPos}
-    (hc : p ((pos.prev h).get (by simp)) = false) : ¬ RevMatchesAt p pos := by
-  simp [revMatchesAt_iff, hc]
-
 theorem matchAt?_eq {s : Slice} {pos : s.Pos} {p : Char → Bool} :
     matchAt? p pos =
       if h₀ : ∃ (h : pos ≠ s.endPos), p (pos.get h) then some (pos.next h₀.1) else none := by
   split <;> simp_all [isLongestMatchAt_iff, matchesAt_iff]
 
-theorem revMatchAt?_eq {s : Slice} {pos : s.Pos} {p : Char → Bool} :
-    revMatchAt? p pos =
-      if h₀ : ∃ (h : pos ≠ s.startPos), p ((pos.prev h).get (by simp)) then some (pos.prev h₀.1) else none := by
-  split <;> simp_all [isLongestRevMatchAt_iff, revMatchesAt_iff]
-
 namespace Decidable
 
-instance {p : Char → Prop} [DecidablePred p] : PatternModel p where
-  Matches := PatternModel.Matches (decide <| p ·)
+instance {p : Char → Prop} [DecidablePred p] : ForwardPatternModel p where
+  Matches := ForwardPatternModel.Matches (decide <| p ·)
+  not_matches_empty := ForwardPatternModel.not_matches_empty (pat := (decide <| p ·))
 
-instance {p : Char → Prop} [DecidablePred p] : StrictPatternModel p where
-  not_matches_empty := StrictPatternModel.not_matches_empty (pat := (decide <| p ·))
-
-instance {p : Char → Prop} [DecidablePred p] : NoPrefixPatternModel p where
-  eq_empty := NoPrefixPatternModel.eq_empty (pat := (decide <| p ·))
-
-instance {p : Char → Prop} [DecidablePred p] : NoSuffixPatternModel p where
-  eq_empty := NoSuffixPatternModel.eq_empty (pat := (decide <| p ·))
+instance {p : Char → Prop} [DecidablePred p] : NoPrefixForwardPatternModel p where
+  eq_empty := NoPrefixForwardPatternModel.eq_empty (pat := (decide <| p ·))
 
 theorem isMatch_iff_isMatch_decide {p : Char → Prop} [DecidablePred p] {s : Slice} {pos : s.Pos} :
     IsMatch p pos ↔ IsMatch (decide <| p ·) pos :=
   ⟨fun ⟨h⟩ => ⟨h⟩, fun ⟨h⟩ => ⟨h⟩⟩
 
-theorem isRevMatch_iff_isRevMatch_decide {p : Char → Prop} [DecidablePred p] {s : Slice} {pos : s.Pos} :
-    IsRevMatch p pos ↔ IsRevMatch (decide <| p ·) pos :=
-  ⟨fun ⟨h⟩ => ⟨h⟩, fun ⟨h⟩ => ⟨h⟩⟩
-
 theorem isMatch_iff {p : Char → Prop} [DecidablePred p] {s : Slice} {pos : s.Pos} :
     IsMatch p pos ↔
       ∃ (h : s.startPos ≠ s.endPos), pos = s.startPos.next h ∧ p (s.startPos.get h) := by
   simp [isMatch_iff_isMatch_decide, CharPred.isMatch_iff]
 
-theorem isRevMatch_iff {p : Char → Prop} [DecidablePred p] {s : Slice} {pos : s.Pos} :
-    IsRevMatch p pos ↔
-      ∃ (h : s.endPos ≠ s.startPos), pos = s.endPos.prev h ∧ p ((s.endPos.prev h).get (by simp)) := by
-  simp [isRevMatch_iff_isRevMatch_decide, CharPred.isRevMatch_iff]
-
 theorem isLongestMatch_iff {p : Char → Prop} [DecidablePred p] {s : Slice} {pos : s.Pos} :
     IsLongestMatch p pos ↔
       ∃ (h : s.startPos ≠ s.endPos), pos = s.startPos.next h ∧ p (s.startPos.get h) := by
   rw [isLongestMatch_iff_isMatch, isMatch_iff]
 
-theorem isLongestRevMatch_iff {p : Char → Prop} [DecidablePred p] {s : Slice} {pos : s.Pos} :
-    IsLongestRevMatch p pos ↔
-      ∃ (h : s.endPos ≠ s.startPos), pos = s.endPos.prev h ∧ p ((s.endPos.prev h).get (by simp)) := by
-  simp [isLongestRevMatch_iff_isRevMatch, isRevMatch_iff]
-
 theorem isLongestMatch_iff_isLongestMatch_decide {p : Char → Prop} [DecidablePred p] {s : Slice}
     {pos : s.Pos} : IsLongestMatch p pos ↔ IsLongestMatch (decide <| p ·) pos := by
   simp [isLongestMatch_iff_isMatch, isMatch_iff_isMatch_decide]
 
-theorem isLongestRevMatch_iff_isLongestRevMatch_decide {p : Char → Prop} [DecidablePred p] {s : Slice}
-    {pos : s.Pos} : IsLongestRevMatch p pos ↔ IsLongestRevMatch (decide <| p ·) pos := by
-  simp [isLongestRevMatch_iff_isRevMatch, isRevMatch_iff_isRevMatch_decide]
-
 theorem isLongestMatchAt_iff_isLongestMatchAt_decide {p : Char → Prop} [DecidablePred p]
     {s : Slice} {pos pos' : s.Pos} :
     IsLongestMatchAt p pos pos' ↔ IsLongestMatchAt (decide <| p ·) pos pos' := by
   simp [Model.isLongestMatchAt_iff, isLongestMatch_iff_isLongestMatch_decide]
 
-theorem isLongestRevMatchAt_iff_isLongestRevMatchAt_decide {p : Char → Prop} [DecidablePred p]
-    {s : Slice} {pos pos' : s.Pos} :
-    IsLongestRevMatchAt p pos pos' ↔ IsLongestRevMatchAt (decide <| p ·) pos pos' := by
-  simp [Model.isLongestRevMatchAt_iff, isLongestRevMatch_iff_isLongestRevMatch_decide]
-
-theorem isLongestMatchAtChain_iff_isLongestMatchAtChain_decide {p : Char → Prop} [DecidablePred p]
-    {s : Slice} {pos pos' : s.Pos} :
-    IsLongestMatchAtChain p pos pos' ↔ IsLongestMatchAtChain (decide <| p ·) pos pos' := by
-  constructor
-  · intro h; induction h with
-    | nil => exact .nil _
-    | cons _ mid _ hmatch hchain ih =>
-      exact .cons _ mid _ (isLongestMatchAt_iff_isLongestMatchAt_decide.1 hmatch) ih
-  · intro h; induction h with
-    | nil => exact .nil _
-    | cons _ mid _ hmatch hchain ih =>
-      exact .cons _ mid _ (isLongestMatchAt_iff_isLongestMatchAt_decide.2 hmatch) ih
-
-theorem isLongestRevMatchAtChain_iff_isLongestRevMatchAtChain_decide {p : Char → Prop} [DecidablePred p]
-    {s : Slice} {pos pos' : s.Pos} :
-    IsLongestRevMatchAtChain p pos pos' ↔ IsLongestRevMatchAtChain (decide <| p ·) pos pos' := by
-  constructor
-  · intro h; induction h with
-    | nil => exact .nil _
-    | cons _ _ hchain hmatch ih =>
-      exact .cons _ _ _ ih (isLongestRevMatchAt_iff_isLongestRevMatchAt_decide.1 hmatch)
-  · intro h; induction h with
-    | nil => exact .nil _
-    | cons _ _ hchain hmatch ih =>
-      exact .cons _ _ _ ih (isLongestRevMatchAt_iff_isLongestRevMatchAt_decide.2 hmatch)
-
 theorem isLongestMatchAt_iff {p : Char → Prop} [DecidablePred p] {s : Slice}
     {pos pos' : s.Pos} :
     IsLongestMatchAt p pos pos' ↔ ∃ h, pos' = pos.next h ∧ p (pos.get h) := by
   simp [isLongestMatchAt_iff_isLongestMatchAt_decide, CharPred.isLongestMatchAt_iff]
 
-theorem isLongestRevMatchAt_iff {p : Char → Prop} [DecidablePred p] {s : Slice}
-    {pos pos' : s.Pos} :
-    IsLongestRevMatchAt p pos pos' ↔ ∃ h, pos = pos'.prev h ∧ p ((pos'.prev h).get (by simp)) := by
-  simp [isLongestRevMatchAt_iff_isLongestRevMatchAt_decide, CharPred.isLongestRevMatchAt_iff]
-
 theorem isLongestMatchAt_of_get {p : Char → Prop} [DecidablePred p] {s : Slice} {pos : s.Pos}
     {h : pos ≠ s.endPos} (hc : p (pos.get h)) : IsLongestMatchAt p pos (pos.next h) :=
   isLongestMatchAt_iff.2 ⟨h, by simp [hc]⟩
 
-theorem isLongestRevMatchAt_of_get {p : Char → Prop} [DecidablePred p] {s : Slice} {pos : s.Pos}
-    {h : pos ≠ s.startPos} (hc : p ((pos.prev h).get (by simp))) :
-    IsLongestRevMatchAt p (pos.prev h) pos :=
-  isLongestRevMatchAt_iff.2 ⟨h, by simp [hc]⟩
-
 theorem matchesAt_iff_matchesAt_decide {p : Char → Prop} [DecidablePred p] {s : Slice}
     {pos : s.Pos} : MatchesAt p pos ↔ MatchesAt (decide <| p ·) pos := by
   simp [matchesAt_iff_exists_isLongestMatchAt, isLongestMatchAt_iff_isLongestMatchAt_decide]
 
-theorem revMatchesAt_iff_revMatchesAt_decide {p : Char → Prop} [DecidablePred p] {s : Slice}
-    {pos : s.Pos} : RevMatchesAt p pos ↔ RevMatchesAt (decide <| p ·) pos := by
-  simp [revMatchesAt_iff_exists_isLongestRevMatchAt, isLongestRevMatchAt_iff_isLongestRevMatchAt_decide]
-
 theorem matchAt?_eq_matchAt?_decide {p : Char → Prop} [DecidablePred p] {s : Slice}
     {pos : s.Pos} : matchAt? p pos = matchAt? (decide <| p ·) pos := by
   ext endPos
   simp [isLongestMatchAt_iff_isLongestMatchAt_decide]
 
-theorem revMatchAt?_eq_revMatchAt?_decide {p : Char → Prop} [DecidablePred p] {s : Slice}
-    {pos : s.Pos} : revMatchAt? p pos = revMatchAt? (decide <| p ·) pos := by
-  ext startPos
-  simp [isLongestRevMatchAt_iff_isLongestRevMatchAt_decide]
-
 theorem skipPrefix?_eq_skipPrefix?_decide {p : Char → Prop} [DecidablePred p] :
     ForwardPattern.skipPrefix? p = ForwardPattern.skipPrefix? (decide <| p ·) := rfl
 
-theorem skipSuffix?_eq_skipSuffix?_decide {p : Char → Prop} [DecidablePred p] :
-    BackwardPattern.skipSuffix? p = BackwardPattern.skipSuffix? (decide <| p ·) := rfl
-
 instance {p : Char → Prop} [DecidablePred p] : LawfulForwardPatternModel p where
   skipPrefix?_eq_some_iff {s} pos := by
     rw [skipPrefix?_eq_skipPrefix?_decide, isLongestMatch_iff_isLongestMatch_decide]
     exact LawfulForwardPatternModel.skipPrefix?_eq_some_iff ..
 
-instance {p : Char → Prop} [DecidablePred p] : LawfulBackwardPatternModel p where
-  skipSuffix?_eq_some_iff {s} pos := by
-    rw [skipSuffix?_eq_skipSuffix?_decide, isLongestRevMatch_iff_isLongestRevMatch_decide]
-    exact LawfulBackwardPatternModel.skipSuffix?_eq_some_iff ..
-
 theorem toSearcher_eq {p : Char → Prop} [DecidablePred p] {s : Slice} :
     ToForwardSearcher.toSearcher p s = ToForwardSearcher.toSearcher (decide <| p ·) s := (rfl)
 
-theorem toBackwardSearcher_eq {p : Char → Prop} [DecidablePred p] {s : Slice} :
-    ToBackwardSearcher.toSearcher p s = ToBackwardSearcher.toSearcher (decide <| p ·) s := (rfl)
-
 theorem isValidSearchFrom_iff_isValidSearchFrom_decide {p : Char → Prop} [DecidablePred p]
     {s : Slice} {pos : s.Pos} {l : List (SearchStep s)} :
     IsValidSearchFrom p pos l ↔ IsValidSearchFrom (decide <| p ·) pos l := by
@@ -346,55 +150,24 @@ theorem isValidSearchFrom_iff_isValidSearchFrom_decide {p : Char → Prop} [Deci
     | matched => simp_all [IsValidSearchFrom.matched, isLongestMatchAt_iff_isLongestMatchAt_decide]
     | mismatched => simp_all [IsValidSearchFrom.mismatched, matchesAt_iff_matchesAt_decide]
 
-theorem isValidRevSearchFrom_iff_isValidRevSearchFrom_decide {p : Char → Prop} [DecidablePred p]
-    {s : Slice} {pos : s.Pos} {l : List (SearchStep s)} :
-    IsValidRevSearchFrom p pos l ↔ IsValidRevSearchFrom (decide <| p ·) pos l := by
-  refine ⟨fun h => ?_, fun h => ?_⟩
-  · induction h with
-    | startPos => simpa using IsValidRevSearchFrom.startPos
-    | matched => simp_all [IsValidRevSearchFrom.matched, isLongestRevMatchAt_iff_isLongestRevMatchAt_decide]
-    | mismatched => simp_all [IsValidRevSearchFrom.mismatched, revMatchesAt_iff_revMatchesAt_decide]
-  · induction h with
-    | startPos => simpa using IsValidRevSearchFrom.startPos
-    | matched => simp_all [IsValidRevSearchFrom.matched, isLongestRevMatchAt_iff_isLongestRevMatchAt_decide]
-    | mismatched => simp_all [IsValidRevSearchFrom.mismatched, revMatchesAt_iff_revMatchesAt_decide]
-
 instance {p : Char → Prop} [DecidablePred p] : LawfulToForwardSearcherModel p where
   isValidSearchFrom_toList s := by
     simpa [toSearcher_eq, isValidSearchFrom_iff_isValidSearchFrom_decide] using
       LawfulToForwardSearcherModel.isValidSearchFrom_toList (pat := (decide <| p ·)) (s := s)
 
-instance {p : Char → Prop} [DecidablePred p] : LawfulToBackwardSearcherModel p where
-  isValidRevSearchFrom_toList s := by
-    simpa [toBackwardSearcher_eq, isValidRevSearchFrom_iff_isValidRevSearchFrom_decide] using
-      LawfulToBackwardSearcherModel.isValidRevSearchFrom_toList (pat := (decide <| p ·)) (s := s)
-
 theorem matchesAt_iff {p : Char → Prop} [DecidablePred p] {s : Slice} {pos : s.Pos} :
     MatchesAt p pos ↔ ∃ (h : pos ≠ s.endPos), p (pos.get h) := by
   simp [matchesAt_iff_exists_isLongestMatchAt, isLongestMatchAt_iff, exists_comm]
 
-theorem revMatchesAt_iff {p : Char → Prop} [DecidablePred p] {s : Slice} {pos : s.Pos} :
-    RevMatchesAt p pos ↔ ∃ (h : pos ≠ s.startPos), p ((pos.prev h).get (by simp)) := by
-  simp [revMatchesAt_iff_exists_isLongestRevMatchAt, isLongestRevMatchAt_iff, exists_comm]
-
 theorem not_matchesAt_of_get {p : Char → Prop} [DecidablePred p] {s : Slice} {pos : s.Pos}
     {h : pos ≠ s.endPos} (hc : ¬ p (pos.get h)) : ¬ MatchesAt p pos := by
   simp [matchesAt_iff, hc]
 
-theorem not_revMatchesAt_of_get {p : Char → Prop} [DecidablePred p] {s : Slice} {pos : s.Pos}
-    {h : pos ≠ s.startPos} (hc : ¬ p ((pos.prev h).get (by simp))) : ¬ RevMatchesAt p pos := by
-  simp [revMatchesAt_iff, hc]
-
 theorem matchAt?_eq {s : Slice} {pos : s.Pos} {p : Char → Prop} [DecidablePred p] :
     matchAt? p pos =
       if h₀ : ∃ (h : pos ≠ s.endPos), p (pos.get h) then some (pos.next h₀.1) else none := by
   split <;> simp_all [isLongestMatchAt_iff, matchesAt_iff]
 
-theorem revMatchAt?_eq {s : Slice} {pos : s.Pos} {p : Char → Prop} [DecidablePred p] :
-    revMatchAt? p pos =
-      if h₀ : ∃ (h : pos ≠ s.startPos), p ((pos.prev h).get (by simp)) then some (pos.prev h₀.1) else none := by
-  split <;> simp_all [isLongestRevMatchAt_iff, revMatchesAt_iff]
-
 end Decidable
 
 end Pattern.Model.CharPred
@@ -411,9 +184,6 @@ theorem dropPrefix_prop_eq_dropPrefix_decide {p : Char → Prop} [DecidablePred
 theorem skipPrefix?_prop_eq_skipPrefix?_decide {p : Char → Prop} [DecidablePred p] {s : Slice} :
     s.skipPrefix? p = s.skipPrefix? (decide <| p ·) := (rfl)
 
-theorem Pos.skip?_prop_eq_skip?_decide {p : Char → Prop} [DecidablePred p] {s : Slice} {pos : s.Pos} :
-    pos.skip? p = pos.skip? (decide <| p ·) := (rfl)
-
 theorem Pattern.ForwardPattern.skipPrefix?_prop_eq_skipPrefix?_decide
     {p : Char → Prop} [DecidablePred p] {s : Slice} :
     skipPrefix? p s = skipPrefix? (decide <| p ·) s := (rfl)
@@ -424,13 +194,13 @@ theorem Pos.skipWhile_prop_eq_skipWhile_decide {p : Char → Prop} [DecidablePre
   fun_induction Pos.skipWhile curr p with
   | case1 pos nextCurr h₁ h₂ ih =>
     conv => rhs; rw [Pos.skipWhile]
-    simp [← Pos.skip?_prop_eq_skip?_decide, h₁, h₂, ih]
+    simp [← Pattern.ForwardPattern.skipPrefix?_prop_eq_skipPrefix?_decide, h₁, h₂, ih]
   | case2 pos nextCurr h ih =>
     conv => rhs; rw [Pos.skipWhile]
-    simp [← Pos.skip?_prop_eq_skip?_decide, h, ih]
+    simp [← Pattern.ForwardPattern.skipPrefix?_prop_eq_skipPrefix?_decide, h, ih]
   | case3 pos h =>
     conv => rhs; rw [Pos.skipWhile]
-    simp [← Pos.skip?_prop_eq_skip?_decide, h]
+    simp [← Pattern.ForwardPattern.skipPrefix?_prop_eq_skipPrefix?_decide]
 
 theorem skipPrefixWhile_prop_eq_skipPrefixWhile_decide {p : Char → Prop} [DecidablePred p]
     {s : Slice} :
@@ -447,7 +217,7 @@ theorem takeWhile_prop_eq_takeWhile_decide {p : Char → Prop} [DecidablePred p]
 
 theorem all_prop_eq_all_decide {p : Char → Prop} [DecidablePred p] {s : Slice} :
     s.all p = s.all (decide <| p ·) := by
-  simp only [all, skipPrefixWhile_prop_eq_skipPrefixWhile_decide]
+  simp only [all, dropWhile_prop_eq_dropWhile_decide]
 
 theorem find?_prop_eq_find?_decide {p : Char → Prop} [DecidablePred p] {s : Slice} :
     s.find? p = s.find? (decide <| p ·) :=
@@ -478,22 +248,19 @@ theorem Pattern.BackwardPattern.skipSuffix?_prop_eq_skipSuffix?_decide
     {p : Char → Prop} [DecidablePred p] {s : Slice} :
     skipSuffix? p s = skipSuffix? (decide <| p ·) s := (rfl)
 
-theorem Pos.revSkip?_prop_eq_revSkip?_decide {p : Char → Prop} [DecidablePred p] {s : Slice} {pos : s.Pos} :
-    pos.revSkip? p = pos.revSkip? (decide <| p ·) := (rfl)
-
 theorem Pos.revSkipWhile_prop_eq_revSkipWhile_decide {p : Char → Prop} [DecidablePred p]
     {s : Slice} (curr : s.Pos) :
     Pos.revSkipWhile curr p = Pos.revSkipWhile curr (decide <| p ·) := by
   fun_induction Pos.revSkipWhile curr p with
   | case1 pos nextCurr h₁ h₂ ih =>
     conv => rhs; rw [Pos.revSkipWhile]
-    simp [← Pos.revSkip?_prop_eq_revSkip?_decide, h₁, h₂, ih]
+    simp [← Pattern.BackwardPattern.skipSuffix?_prop_eq_skipSuffix?_decide, h₁, h₂, ih]
   | case2 pos nextCurr h ih =>
     conv => rhs; rw [Pos.revSkipWhile]
-    simp [← Pos.revSkip?_prop_eq_revSkip?_decide, h, ih]
+    simp [← Pattern.BackwardPattern.skipSuffix?_prop_eq_skipSuffix?_decide, h, ih]
   | case3 pos h =>
     conv => rhs; rw [Pos.revSkipWhile]
-    simp [← Pos.revSkip?_prop_eq_revSkip?_decide, h]
+    simp [← Pattern.BackwardPattern.skipSuffix?_prop_eq_skipSuffix?_decide]
 
 theorem skipSuffixWhile_prop_eq_skipSuffixWhile_decide {p : Char → Prop} [DecidablePred p]
     {s : Slice} :
@@ -510,8 +277,4 @@ theorem takeEndWhile_prop_eq_takeEndWhile_decide {p : Char → Prop} [DecidableP
     s.takeEndWhile p = s.takeEndWhile (decide <| p ·) := by
   simp only [takeEndWhile]; exact congrArg _ skipSuffixWhile_prop_eq_skipSuffixWhile_decide
 
-theorem revAll_prop_eq_revAll_decide {p : Char → Prop} [DecidablePred p] {s : Slice} :
-    s.revAll p = s.revAll (decide <| p ·) := by
-  simp only [revAll, skipSuffixWhile_prop_eq_skipSuffixWhile_decide]
-
 end String.Slice

src/Init/Data/String/Lemmas/Pattern/Split/Basic.lean

@@ -28,7 +28,7 @@ set_option doc.verso true
 # Verification of {name}`String.Slice.splitToSubslice`
 
 This PR verifies the {name}`String.Slice.splitToSubslice` function by relating it to a model
-implementation based on the {name}`String.Slice.Pattern.Model.PatternModel` class.
+implementation based on the {name}`String.Slice.Pattern.Model.ForwardPatternModel` class.
 
 This gives a low-level correctness proof from which higher-level API lemmas can be derived.
 -/
@@ -36,7 +36,7 @@ This gives a low-level correctness proof from which higher-level API lemmas can
 namespace String.Slice.Pattern.Model
 
 @[cbv_opaque]
-public protected noncomputable def split {ρ : Type} (pat : ρ) [PatternModel pat] [StrictPatternModel pat] {s : Slice}
+public protected noncomputable def split {ρ : Type} (pat : ρ) [ForwardPatternModel pat] {s : Slice}
     (firstRejected curr : s.Pos) (hle : firstRejected ≤ curr) : List s.Subslice :=
   if h : curr = s.endPos then
     [s.subslice _ _ hle]
@@ -49,12 +49,12 @@ public protected noncomputable def split {ρ : Type} (pat : ρ) [PatternModel pa
 termination_by curr
 
 @[simp]
-public theorem split_endPos {ρ : Type} {pat : ρ} [PatternModel pat] [StrictPatternModel pat] {s : Slice}
+public theorem split_endPos {ρ : Type} {pat : ρ} [ForwardPatternModel pat] {s : Slice}
     {firstRejected : s.Pos} :
     Model.split (s := s) pat firstRejected s.endPos (by simp) = [s.subslice firstRejected s.endPos (by simp)] := by
   simp [Model.split]
 
-public theorem split_eq_of_isLongestMatchAt {ρ : Type} {pat : ρ} [PatternModel pat] [StrictPatternModel pat]
+public theorem split_eq_of_isLongestMatchAt {ρ : Type} {pat : ρ} [ForwardPatternModel pat]
     {s : Slice} {firstRejected start stop : s.Pos} {hle} (h : IsLongestMatchAt pat start stop) :
     Model.split pat firstRejected start hle =
       s.subslice _ _ hle :: Model.split pat stop stop (by exact Std.le_refl _) := by
@@ -63,7 +63,7 @@ public theorem split_eq_of_isLongestMatchAt {ρ : Type} {pat : ρ} [PatternModel
   · congr <;> exact (matchAt?_eq_some_iff.1 ‹_›).eq h
   · simp [matchAt?_eq_some_iff.2 ‹_›] at *
 
-public theorem split_eq_of_not_matchesAt {ρ : Type} {pat : ρ} [PatternModel pat] [StrictPatternModel pat]
+public theorem split_eq_of_not_matchesAt {ρ : Type} {pat : ρ} [ForwardPatternModel pat]
     {s : Slice} {firstRejected start} (stop : s.Pos) (h₀ : start ≤ stop) {hle}
     (h : ∀ p, start ≤ p → p < stop → ¬ MatchesAt pat p) :
     Model.split pat firstRejected start hle =
@@ -80,7 +80,7 @@ public theorem split_eq_of_not_matchesAt {ρ : Type} {pat : ρ} [PatternModel pa
   · obtain rfl : start = stop := Std.le_antisymm h₀ (Std.not_lt.1 h')
     simp
 
-public theorem split_eq_next_of_not_matchesAt {ρ : Type} {pat : ρ} [PatternModel pat] [StrictPatternModel pat]
+public theorem split_eq_next_of_not_matchesAt {ρ : Type} {pat : ρ} [ForwardPatternModel pat]
     {s : Slice} {firstRejected start} {hle} (hs : start ≠ s.endPos) (h : ¬ MatchesAt pat start) :
     Model.split pat firstRejected start hle =
       Model.split pat firstRejected (start.next hs) (by exact Std.le_trans hle (by simp)) := by
@@ -103,7 +103,7 @@ def splitFromSteps {s : Slice} (currPos : s.Pos) (l : List (SearchStep s)) : Lis
   | .matched p q :: l => s.subslice! currPos p :: splitFromSteps q l
 
 theorem IsValidSearchFrom.splitFromSteps_eq_extend_split {ρ : Type} (pat : ρ)
-    [PatternModel pat] [StrictPatternModel pat] (l : List (SearchStep s)) (pos pos' : s.Pos) (h₀ : pos ≤ pos')
+    [ForwardPatternModel pat] (l : List (SearchStep s)) (pos pos' : s.Pos) (h₀ : pos ≤ pos')
     (h' : ∀ p, pos ≤ p → p < pos' → ¬ MatchesAt pat p)
     (h : IsValidSearchFrom pat pos' l) :
     splitFromSteps pos l = Model.split pat pos pos' h₀ := by
@@ -155,7 +155,7 @@ end Model
 open Model
 
 @[cbv_eval]
-public theorem toList_splitToSubslice_eq_modelSplit {ρ : Type} (pat : ρ) [PatternModel pat] [StrictPatternModel pat]
+public theorem toList_splitToSubslice_eq_modelSplit {ρ : Type} (pat : ρ) [ForwardPatternModel pat]
     {σ : Slice → Type} [ToForwardSearcher pat σ] [∀ s, Std.Iterator (σ s) Id (SearchStep s)]
     [∀ s, Std.Iterators.Finite (σ s) Id] [LawfulToForwardSearcherModel pat] (s : Slice) :
     (s.splitToSubslice pat).toList = Model.split pat s.startPos s.startPos (by exact Std.le_refl _) := by
@@ -168,7 +168,7 @@ end Pattern
 open Pattern
 
 public theorem toList_splitToSubslice_of_isEmpty {ρ : Type} (pat : ρ)
-    [Model.PatternModel pat] [Model.StrictPatternModel pat] {σ : Slice → Type}
+    [Model.ForwardPatternModel pat] {σ : Slice → Type}
     [ToForwardSearcher pat σ] [∀ s, Std.Iterator (σ s) Id (SearchStep s)]
     [∀ s, Std.Iterators.Finite (σ s) Id] [Model.LawfulToForwardSearcherModel pat] {s : Slice}
     (h : s.isEmpty = true) :
@@ -182,7 +182,7 @@ public theorem toList_split_eq_splitToSubslice {ρ : Type} (pat : ρ) {σ : Slic
   simp [split, Std.Iter.toList_map]
 
 public theorem toList_split_of_isEmpty {ρ : Type} (pat : ρ)
-    [Model.PatternModel pat] [Model.StrictPatternModel pat] {σ : Slice → Type}
+    [Model.ForwardPatternModel pat] {σ : Slice → Type}
     [ToForwardSearcher pat σ] [∀ s, Std.Iterator (σ s) Id (SearchStep s)]
     [∀ s, Std.Iterators.Finite (σ s) Id] [Model.LawfulToForwardSearcherModel pat] {s : Slice}
     (h : s.isEmpty = true) :
@@ -200,7 +200,7 @@ public theorem split_eq_split_toSlice {ρ : Type} {pat : ρ} {σ : Slice → Typ
 
 @[simp]
 public theorem toList_split_empty {ρ : Type} (pat : ρ)
-    [Model.PatternModel pat] [Model.StrictPatternModel pat] {σ : Slice → Type}
+    [Model.ForwardPatternModel pat] {σ : Slice → Type}
     [ToForwardSearcher pat σ] [∀ s, Std.Iterator (σ s) Id (SearchStep s)]
     [∀ s, Std.Iterators.Finite (σ s) Id] [Model.LawfulToForwardSearcherModel pat] :
     ("".split pat).toList.map Slice.copy = [""] := by

src/Init/Data/String/Lemmas/Pattern/Split/Char.lean

@@ -23,7 +23,6 @@ import Init.Data.String.OrderInstances
 import Init.Data.String.Lemmas.Order
 import Init.Data.String.Lemmas.Intercalate
 import Init.Data.List.SplitOn.Lemmas
-import Init.Data.String.Lemmas.Slice
 
 public section
 
@@ -71,11 +70,6 @@ theorem Slice.toList_split_intercalate {c : Char} {l : List Slice} (hl : ∀ s
   · simp_all
   · rw [List.splitOn_intercalate] <;> simp_all
 
-theorem Slice.toList_split_intercalate_beq {c : Char} {l : List Slice} (hl : ∀ s ∈ l, c ∉ s.copy.toList) :
-    ((Slice.intercalate (String.singleton c) l).split c).toList ==
-      if l = [] then ["".toSlice] else l := by
-  split <;> simp_all [toList_split_intercalate hl, beq_list_iff]
-
 theorem toList_split_intercalate {c : Char} {l : List String} (hl : ∀ s ∈ l, c ∉ s.toList) :
     ((String.intercalate (String.singleton c) l).split c).toList.map (·.copy) =
       if l = [] then [""] else l := by
@@ -84,9 +78,4 @@ theorem toList_split_intercalate {c : Char} {l : List String} (hl : ∀ s ∈ l,
   · simp_all
   · rw [List.splitOn_intercalate] <;> simp_all
 
-theorem toList_split_intercalate_beq {c : Char} {l : List String} (hl : ∀ s ∈ l, c ∉ s.toList) :
-    ((String.intercalate (String.singleton c) l).split c).toList ==
-      if l = [] then ["".toSlice] else l.map String.toSlice := by
-  split <;> simp_all [toList_split_intercalate hl, Slice.beq_list_iff]
-
 end String

src/Init/Data/String/Lemmas/Pattern/String/Basic.lean

@@ -10,9 +10,6 @@ public import Init.Data.String.Pattern.String
 public import Init.Data.String.Lemmas.Pattern.Basic
 import Init.Data.String.Lemmas.IsEmpty
 import Init.Data.String.Lemmas.Basic
-import Init.Data.String.Lemmas.Intercalate
-import Init.Data.String.OrderInstances
-import Init.Data.String.Lemmas.Splits
 import Init.Data.ByteArray.Lemmas
 import Init.Omega
 
@@ -22,135 +19,52 @@ namespace String.Slice.Pattern.Model
 
 namespace ForwardSliceSearcher
 
-instance {pat : Slice} : PatternModel pat where
-  Matches s := s = pat.copy
+instance {pat : Slice} : ForwardPatternModel pat where
+  /-
+  See the docstring of `ForwardPatternModel` for an explanation about why we disallow matching the
+  empty string.
 
-theorem strictPatternModel {pat : Slice} (hpat : pat.isEmpty = false) : StrictPatternModel pat where
-  not_matches_empty := by simpa [PatternModel.Matches]
+  Requiring `s ≠ ""` is a trick that allows us to give a `ForwardPatternModel` instance
+  unconditionally, without forcing `pat.copy` to be non-empty (which would make it very awkward
+  to state theorems about the instance). It does not change anything about the fact that all lemmas
+  about this instance require `pat.isEmpty = false`.
+  -/
+  Matches s := s ≠ "" ∧ s = pat.copy
+  not_matches_empty := by simp
 
-instance {pat : Slice} : NoPrefixPatternModel pat :=
-  .of_length_eq (by simp +contextual [PatternModel.Matches])
+instance {pat : Slice} : NoPrefixForwardPatternModel pat :=
+  .of_length_eq (by simp +contextual [ForwardPatternModel.Matches])
 
-instance {pat : Slice} : NoSuffixPatternModel pat :=
-  .of_length_eq (by simp +contextual [PatternModel.Matches])
-
-theorem isMatch_iff {pat s : Slice} {pos : s.Pos} :
+theorem isMatch_iff {pat s : Slice} {pos : s.Pos} (h : pat.isEmpty = false) :
     IsMatch pat pos ↔ (s.sliceTo pos).copy = pat.copy := by
-  simp [Model.isMatch_iff, PatternModel.Matches]
+  simp only [Model.isMatch_iff, ForwardPatternModel.Matches, ne_eq, copy_eq_empty_iff,
+    Bool.not_eq_true, and_iff_right_iff_imp]
+  intro h'
+  rw [← isEmpty_copy (s := s.sliceTo pos), h', isEmpty_copy, h]
 
-theorem isRevMatch_iff {pat s : Slice} {pos : s.Pos} :
-    IsRevMatch pat pos ↔ (s.sliceFrom pos).copy = pat.copy := by
-  simp [Model.isRevMatch_iff, PatternModel.Matches]
-
-theorem isLongestMatch_iff {pat s : Slice} {pos : s.Pos} :
+theorem isLongestMatch_iff {pat s : Slice} {pos : s.Pos} (h : pat.isEmpty = false) :
     IsLongestMatch pat pos ↔ (s.sliceTo pos).copy = pat.copy := by
-  rw [isLongestMatch_iff_isMatch, isMatch_iff]
+  rw [isLongestMatch_iff_isMatch, isMatch_iff h]
 
-theorem isLongestRevMatch_iff {pat s : Slice} {pos : s.Pos} :
-    IsLongestRevMatch pat pos ↔ (s.sliceFrom pos).copy = pat.copy := by
-  rw [isLongestRevMatch_iff_isRevMatch, isRevMatch_iff]
-
-theorem isLongestMatchAt_iff {pat s : Slice} {pos₁ pos₂ : s.Pos} :
+theorem isLongestMatchAt_iff {pat s : Slice} {pos₁ pos₂ : s.Pos} (h : pat.isEmpty = false) :
     IsLongestMatchAt pat pos₁ pos₂ ↔ ∃ h, (s.slice pos₁ pos₂ h).copy = pat.copy := by
-  simp [Model.isLongestMatchAt_iff, isLongestMatch_iff]
+  simp [Model.isLongestMatchAt_iff, isLongestMatch_iff h]
 
-theorem isLongestMatchAtChain_iff {pat s : Slice} {pos₁ pos₂ : s.Pos} :
-    IsLongestMatchAtChain pat pos₁ pos₂ ↔
-      ∃ h n, (s.slice pos₁ pos₂ h).copy = String.join (List.replicate n pat.copy) := by
-  refine ⟨fun h => ⟨h.le, ?_⟩, fun ⟨h, n, h'⟩ => ?_⟩
-  · induction h with
-    | nil => simpa using ⟨0, by simp⟩
-    | cons p₁ p₂ p₃ h₁ h₂ ih =>
-      rw [isLongestMatchAt_iff] at h₁
-      obtain ⟨n, ih⟩ := ih
-      obtain ⟨h₀, h₁⟩ := h₁
-      have : (s.slice p₁ p₃ (Std.le_trans h₀ h₂.le)).copy = (s.slice p₁ p₂ h₀).copy ++ (s.slice p₂ p₃ h₂.le).copy := by
-        simp [(Slice.Pos.slice p₂ _ _ h₀ h₂.le).splits.eq_append]
-      refine ⟨n + 1, ?_⟩
-      rw [this, h₁, ih]
-      simp [← String.join_cons, ← List.replicate_succ]
-  · induction n generalizing pos₁ pos₂ with
-    | zero => simp_all
-    | succ n ih =>
-      rw [List.replicate_succ, String.join_cons] at h'
-      refine .cons _ (Pos.ofSlice (Pos.ofEqAppend h')) _ ?_ (ih ?_ Pos.ofSlice_le ?_)
-      · simpa [isLongestMatchAt_iff] using (Pos.splits_ofEqAppend h').copy_sliceTo_eq
-      · simpa [sliceFrom_slice ▸ (Pos.splits_ofEqAppend h').copy_sliceFrom_eq] using ⟨n, rfl⟩
-      · simpa using (Pos.splits_ofEqAppend h').copy_sliceFrom_eq
-
-theorem isLongestMatchAtChain_startPos_endPos_iff {pat s : Slice} :
-    IsLongestMatchAtChain pat s.startPos s.endPos ↔
-      ∃ n, s.copy = String.join (List.replicate n pat.copy) := by
-  simp [isLongestMatchAtChain_iff]
-
-theorem isLongestRevMatchAt_iff {pat s : Slice} {pos₁ pos₂ : s.Pos} :
-    IsLongestRevMatchAt pat pos₁ pos₂ ↔ ∃ h, (s.slice pos₁ pos₂ h).copy = pat.copy := by
-  simp [Model.isLongestRevMatchAt_iff, isLongestRevMatch_iff]
-
-theorem isLongestRevMatchAtChain_iff {pat s : Slice} {pos₁ pos₂ : s.Pos} :
-    IsLongestRevMatchAtChain pat pos₁ pos₂ ↔
-      ∃ h n, (s.slice pos₁ pos₂ h).copy = String.join (List.replicate n pat.copy) := by
-  refine ⟨fun h => ⟨h.le, ?_⟩, fun ⟨h, n, h'⟩ => ?_⟩
-  · induction h with
-    | nil => simpa using ⟨0, by simp⟩
-    | cons p₂ p₃ h₁ h₂ ih =>
-      rw [isLongestRevMatchAt_iff] at h₂
-      obtain ⟨n, ih⟩ := ih
-      obtain ⟨h₀, h₂⟩ := h₂
-      have : (s.slice pos₁ p₃ (Std.le_trans h₁.le h₀)).copy = (s.slice pos₁ p₂ h₁.le).copy ++ (s.slice p₂ p₃ h₀).copy := by
-        simp [(Slice.Pos.slice p₂ _ _ (IsLongestRevMatchAtChain.le ‹_›) h₀).splits.eq_append]
-      refine ⟨n + 1, ?_⟩
-      rw [this, h₂, ih]
-      simp [← List.replicate_append_replicate]
-  · induction n generalizing pos₁ pos₂ with
-    | zero => simp_all
-    | succ n ih =>
-      have h'' : (s.slice pos₁ pos₂ h).copy = String.join (List.replicate n pat.copy) ++ pat.copy := by
-        rw [h', List.replicate_succ', String.join_append]; simp
-      refine .cons _ (Pos.ofSlice (Pos.ofEqAppend h'')) _ (ih ?_ Pos.le_ofSlice ?_) ?_
-      · simpa [sliceTo_slice ▸ (Pos.splits_ofEqAppend h'').copy_sliceTo_eq] using ⟨n, rfl⟩
-      · simpa using (Pos.splits_ofEqAppend h'').copy_sliceTo_eq
-      · simpa [isLongestRevMatchAt_iff] using (Pos.splits_ofEqAppend h'').copy_sliceFrom_eq
-
-theorem isLongestRevMatchAtChain_startPos_endPos_iff {pat s : Slice} :
-    IsLongestRevMatchAtChain pat s.startPos s.endPos ↔
-      ∃ n, s.copy = String.join (List.replicate n pat.copy) := by
-  simp [isLongestRevMatchAtChain_iff]
-
-theorem isLongestMatchAt_iff_splits {pat s : Slice} {pos₁ pos₂ : s.Pos} :
+theorem isLongestMatchAt_iff_splits {pat s : Slice} {pos₁ pos₂ : s.Pos} (h : pat.isEmpty = false) :
     IsLongestMatchAt pat pos₁ pos₂ ↔ ∃ t₁ t₂, pos₁.Splits t₁ (pat.copy ++ t₂) ∧
       pos₂.Splits (t₁ ++ pat.copy) t₂ := by
-  simp only [isLongestMatchAt_iff, copy_slice_eq_iff_splits]
+  simp only [isLongestMatchAt_iff h, copy_slice_eq_iff_splits]
 
-theorem isLongestRevMatchAt_iff_splits {pat s : Slice} {pos₁ pos₂ : s.Pos} :
-    IsLongestRevMatchAt pat pos₁ pos₂ ↔ ∃ t₁ t₂, pos₁.Splits t₁ (pat.copy ++ t₂) ∧
-      pos₂.Splits (t₁ ++ pat.copy) t₂ := by
-  simp only [isLongestRevMatchAt_iff, copy_slice_eq_iff_splits]
-
-theorem isLongestMatch_iff_splits {pat s : Slice} {pos : s.Pos} :
+theorem isLongestMatch_iff_splits {pat s : Slice} {pos : s.Pos} (h : pat.isEmpty = false) :
     IsLongestMatch pat pos ↔ ∃ t, pos.Splits pat.copy t := by
-  rw [isLongestMatch_iff, copy_sliceTo_eq_iff_exists_splits]
-
-theorem isLongestRevMatch_iff_splits {pat s : Slice} {pos : s.Pos} :
-    IsLongestRevMatch pat pos ↔ ∃ t, pos.Splits t pat.copy := by
-  rw [isLongestRevMatch_iff, copy_sliceFrom_eq_iff_exists_splits]
+  simp only [← isLongestMatchAt_startPos_iff, isLongestMatchAt_iff_splits h, splits_startPos_iff,
+    and_assoc, exists_and_left, exists_eq_left, empty_append]
+  exact ⟨fun ⟨h, _, h'⟩ => ⟨h, h'⟩, fun ⟨h, h'⟩ => ⟨h, h'.eq_append.symm, h'⟩⟩
 
 theorem isLongestMatchAt_iff_extract {pat s : Slice} {pos₁ pos₂ : s.Pos} (h : pat.isEmpty = false) :
     IsLongestMatchAt pat pos₁ pos₂ ↔
       s.copy.toByteArray.extract pos₁.offset.byteIdx pos₂.offset.byteIdx = pat.copy.toByteArray := by
-  rw [isLongestMatchAt_iff]
-  refine ⟨fun ⟨h, h'⟩ => ?_, fun h' => ?_⟩
-  · simp [← h', toByteArray_copy_slice]
-  · rw [← Slice.toByteArray_copy_ne_empty_iff, ← h', ne_eq, ByteArray.extract_eq_empty_iff] at h
-    exact ⟨by simp [Pos.le_iff, Pos.Raw.le_iff]; omega,
-      by simp [← h', ← toByteArray_inj, toByteArray_copy_slice]⟩
-
-theorem isLongestRevMatchAt_iff_extract {pat s : Slice} {pos₁ pos₂ : s.Pos}
-    (h : pat.isEmpty = false) :
-    IsLongestRevMatchAt pat pos₁ pos₂ ↔
-      s.copy.toByteArray.extract pos₁.offset.byteIdx pos₂.offset.byteIdx =
-        pat.copy.toByteArray := by
-  rw [isLongestRevMatchAt_iff]
+  rw [isLongestMatchAt_iff h]
   refine ⟨fun ⟨h, h'⟩ => ?_, fun h' => ?_⟩
   · simp [← h', toByteArray_copy_slice]
   · rw [← Slice.toByteArray_copy_ne_empty_iff, ← h', ne_eq, ByteArray.extract_eq_empty_iff] at h
@@ -167,32 +81,15 @@ theorem offset_of_isLongestMatchAt {pat s : Slice} {pos₁ pos₂ : s.Pos} (h :
   suffices pos₂.offset.byteIdx ≤ s.utf8ByteSize by omega
   simpa [Pos.le_iff, Pos.Raw.le_iff] using pos₂.le_endPos
 
-theorem offset_of_isLongestRevMatchAt {pat s : Slice} {pos₁ pos₂ : s.Pos}
-    (h : pat.isEmpty = false) (h' : IsLongestRevMatchAt pat pos₁ pos₂) :
-    pos₂.offset = pos₁.offset.increaseBy pat.utf8ByteSize := by
-  simp only [Pos.Raw.ext_iff, Pos.Raw.byteIdx_increaseBy]
-  rw [isLongestRevMatchAt_iff_extract h] at h'
-  rw [← Slice.toByteArray_copy_ne_empty_iff, ← h', ne_eq, ByteArray.extract_eq_empty_iff] at h
-  replace h' := congrArg ByteArray.size h'
-  simp only [ByteArray.size_extract, size_toByteArray, utf8ByteSize_copy] at h'
-  suffices pos₂.offset.byteIdx ≤ s.utf8ByteSize by omega
-  simpa [Pos.le_iff, Pos.Raw.le_iff] using pos₂.le_endPos
-
-theorem matchesAt_iff_splits {pat s : Slice} {pos : s.Pos} :
+theorem matchesAt_iff_splits {pat s : Slice} {pos : s.Pos} (h : pat.isEmpty = false) :
     MatchesAt pat pos ↔ ∃ t₁ t₂, pos.Splits t₁ (pat.copy ++ t₂) := by
-  simp only [matchesAt_iff_exists_isLongestMatchAt, isLongestMatchAt_iff_splits]
+  simp only [matchesAt_iff_exists_isLongestMatchAt, isLongestMatchAt_iff_splits h]
   exact ⟨fun ⟨e, t₁, t₂, ht₁, ht₂⟩ => ⟨t₁, t₂, ht₁⟩,
     fun ⟨t₁, t₂, ht⟩ => ⟨ht.rotateRight, t₁, t₂, ht, ht.splits_rotateRight⟩⟩
 
-theorem revMatchesAt_iff_splits {pat s : Slice} {pos : s.Pos} :
-    RevMatchesAt pat pos ↔ ∃ t₁ t₂, pos.Splits (t₁ ++ pat.copy) t₂ := by
-  simp only [revMatchesAt_iff_exists_isLongestRevMatchAt, isLongestRevMatchAt_iff_splits]
-  exact ⟨fun ⟨e, t₁, t₂, ht₁, ht₂⟩ => ⟨t₁, t₂, ht₂⟩,
-    fun ⟨t₁, t₂, ht⟩ => ⟨ht.rotateLeft, t₁, t₂, ht.splits_rotateLeft, ht⟩⟩
-
-theorem exists_matchesAt_iff_eq_append {pat s : Slice} :
+theorem exists_matchesAt_iff_eq_append {pat s : Slice} (h : pat.isEmpty = false) :
     (∃ (pos : s.Pos), MatchesAt pat pos) ↔ ∃ t₁ t₂, s.copy = t₁ ++ pat.copy ++ t₂ := by
-  simp only [matchesAt_iff_splits]
+  simp only [matchesAt_iff_splits h]
   constructor
   · rintro ⟨pos, t₁, t₂, hsplit⟩
     exact ⟨t₁, t₂, by rw [hsplit.eq_append, append_assoc]⟩
@@ -202,18 +99,6 @@ theorem exists_matchesAt_iff_eq_append {pat s : Slice} :
         ⟨t₁, pat.copy ++ t₂, by rw [← append_assoc]; exact heq, rfl⟩
     exact ⟨s.pos _ hvalid, t₁, t₂, ⟨by rw [← append_assoc]; exact heq, by simp⟩⟩
 
-theorem exists_revMatchesAt_iff_eq_append {pat s : Slice} :
-    (∃ (pos : s.Pos), RevMatchesAt pat pos) ↔ ∃ t₁ t₂, s.copy = t₁ ++ pat.copy ++ t₂ := by
-  simp only [revMatchesAt_iff_splits]
-  constructor
-  · rintro ⟨pos, t₁, t₂, hsplit⟩
-    exact ⟨t₁, t₂, by rw [hsplit.eq_append, append_assoc]⟩
-  · rintro ⟨t₁, t₂, heq⟩
-    have hvalid : (t₁ ++ pat.copy).rawEndPos.IsValidForSlice s :=
-      Pos.Raw.isValidForSlice_iff_exists_append.mpr
-        ⟨t₁ ++ pat.copy, t₂, heq, rfl⟩
-    exact ⟨s.pos _ hvalid, t₁, t₂, ⟨heq, by simp⟩⟩
-
 theorem matchesAt_iff_isLongestMatchAt {pat s : Slice} {pos : s.Pos} (h : pat.isEmpty = false) :
     MatchesAt pat pos ↔ ∃ (h : (pos.offset.increaseBy pat.utf8ByteSize).IsValidForSlice s),
       IsLongestMatchAt pat pos (s.pos _ h) := by
@@ -223,25 +108,6 @@ theorem matchesAt_iff_isLongestMatchAt {pat s : Slice} {pos : s.Pos} (h : pat.is
   obtain rfl : p = s.pos _ this := by simpa [Pos.ext_iff] using offset_of_isLongestMatchAt h h'
   exact h'
 
-theorem revMatchesAt_iff_isLongestRevMatchAt {pat s : Slice} {pos : s.Pos}
-    (h : pat.isEmpty = false) :
-    RevMatchesAt pat pos ↔
-      ∃ (h : (pos.offset.decreaseBy pat.utf8ByteSize).IsValidForSlice s),
-        IsLongestRevMatchAt pat (s.pos _ h) pos := by
-  refine ⟨fun ⟨⟨p, h'⟩⟩ => ?_, fun ⟨_, h⟩ => ⟨⟨_, h⟩⟩⟩
-  have hoff := offset_of_isLongestRevMatchAt h h'
-  have hvalid : (pos.offset.decreaseBy pat.utf8ByteSize).IsValidForSlice s := by
-    rw [show pos.offset.decreaseBy pat.utf8ByteSize = p.offset from by
-      simp [Pos.Raw.ext_iff, Pos.Raw.byteIdx_decreaseBy, Pos.Raw.byteIdx_increaseBy] at hoff ⊢
-      omega]
-    exact p.isValidForSlice
-  refine ⟨hvalid, ?_⟩
-  obtain rfl : p = s.pos _ hvalid := by
-    simp only [Pos.ext_iff, offset_pos]
-    simp [Pos.Raw.ext_iff, Pos.Raw.byteIdx_decreaseBy, Pos.Raw.byteIdx_increaseBy] at hoff ⊢
-    omega
-  exact h'
-
 theorem matchesAt_iff_getElem {pat s : Slice} {pos : s.Pos} (h : pat.isEmpty = false) :
     MatchesAt pat pos ↔
       ∃ (h : pos.offset.byteIdx + pat.copy.toByteArray.size ≤ s.copy.toByteArray.size),
@@ -280,194 +146,81 @@ end ForwardSliceSearcher
 
 namespace ForwardStringSearcher
 
-instance {pat : String} : PatternModel pat where
-  Matches s := s = pat
+instance {pat : String} : ForwardPatternModel pat where
+  Matches s := s ≠ "" ∧ s = pat
+  not_matches_empty := by simp
 
-theorem strictPatternModel {pat : String} (h : pat ≠ "") : StrictPatternModel pat where
-  not_matches_empty := by simpa [PatternModel.Matches]
-
-instance {pat : String} : NoPrefixPatternModel pat :=
-  .of_length_eq (by simp +contextual [PatternModel.Matches])
-
-instance {pat : String} : NoSuffixPatternModel pat :=
-  .of_length_eq (by simp +contextual [PatternModel.Matches])
+instance {pat : String} : NoPrefixForwardPatternModel pat :=
+  .of_length_eq (by simp +contextual [ForwardPatternModel.Matches])
 
 theorem isMatch_iff_slice {pat : String} {s : Slice} {pos : s.Pos} :
     IsMatch (ρ := String) pat pos ↔ IsMatch (ρ := Slice) pat.toSlice pos := by
-  simp only [Model.isMatch_iff, PatternModel.Matches, copy_toSlice]
-
-theorem isRevMatch_iff_slice {pat : String} {s : Slice} {pos : s.Pos} :
-    IsRevMatch (ρ := String) pat pos ↔ IsRevMatch (ρ := Slice) pat.toSlice pos := by
-  simp only [Model.isRevMatch_iff, PatternModel.Matches, copy_toSlice]
+  simp only [Model.isMatch_iff, ForwardPatternModel.Matches, copy_toSlice]
 
 theorem isLongestMatch_iff_isLongestMatch_toSlice {pat : String} {s : Slice} {pos : s.Pos} :
     IsLongestMatch (ρ := String) pat pos ↔ IsLongestMatch (ρ := Slice) pat.toSlice pos where
   mp h := ⟨isMatch_iff_slice.1 h.isMatch, fun p hp hm => h.not_isMatch p hp (isMatch_iff_slice.2 hm)⟩
   mpr h := ⟨isMatch_iff_slice.2 h.isMatch, fun p hp hm => h.not_isMatch p hp (isMatch_iff_slice.1 hm)⟩
 
-theorem isLongestRevMatch_iff_isLongestRevMatch_toSlice {pat : String} {s : Slice} {pos : s.Pos} :
-    IsLongestRevMatch (ρ := String) pat pos ↔ IsLongestRevMatch (ρ := Slice) pat.toSlice pos where
-  mp h := ⟨isRevMatch_iff_slice.1 h.isRevMatch,
-    fun p hp hm => h.not_isRevMatch p hp (isRevMatch_iff_slice.2 hm)⟩
-  mpr h := ⟨isRevMatch_iff_slice.2 h.isRevMatch,
-    fun p hp hm => h.not_isRevMatch p hp (isRevMatch_iff_slice.1 hm)⟩
-
 theorem isLongestMatchAt_iff_isLongestMatchAt_toSlice {pat : String} {s : Slice} {pos₁ pos₂ : s.Pos} :
     IsLongestMatchAt (ρ := String) pat pos₁ pos₂ ↔
       IsLongestMatchAt (ρ := Slice) pat.toSlice pos₁ pos₂ := by
   simp [Model.isLongestMatchAt_iff, isLongestMatch_iff_isLongestMatch_toSlice]
 
-theorem isLongestMatchAtChain_iff_isLongestMatchAtChain_toSlice {pat : String} {s : Slice} {pos₁ pos₂ : s.Pos} :
-    IsLongestMatchAtChain pat pos₁ pos₂ ↔
-      IsLongestMatchAtChain pat.toSlice pos₁ pos₂ := by
-  refine ⟨fun h => ?_, fun h => ?_⟩
-  · induction h with
-    | nil => simp
-    | cons p₁ p₂ p₃ h₁ h₂ ih =>
-      exact .cons _ _ _ (isLongestMatchAt_iff_isLongestMatchAt_toSlice.1 h₁) ih
-  · induction h with
-    | nil => simp
-    | cons p₁ p₂ p₃ h₁ h₂ ih =>
-      exact .cons _ _ _ (isLongestMatchAt_iff_isLongestMatchAt_toSlice.2 h₁) ih
-
-theorem isLongestMatchAtChain_iff {pat : String} {s : Slice} {pos₁ pos₂ : s.Pos} :
-    IsLongestMatchAtChain pat pos₁ pos₂ ↔
-      ∃ h n, (s.slice pos₁ pos₂ h).copy = String.join (List.replicate n pat) := by
-  simp [isLongestMatchAtChain_iff_isLongestMatchAtChain_toSlice,
-    ForwardSliceSearcher.isLongestMatchAtChain_iff]
-
-theorem isLongestMatchAtChain_startPos_endPos_iff {pat : String} {s : Slice} :
-    IsLongestMatchAtChain pat s.startPos s.endPos ↔
-      ∃ n, s.copy = String.join (List.replicate n pat) := by
-  simp [isLongestMatchAtChain_iff]
-
-theorem isLongestRevMatchAt_iff_isLongestRevMatchAt_toSlice {pat : String} {s : Slice}
-    {pos₁ pos₂ : s.Pos} :
-    IsLongestRevMatchAt (ρ := String) pat pos₁ pos₂ ↔
-      IsLongestRevMatchAt (ρ := Slice) pat.toSlice pos₁ pos₂ := by
-  simp [Model.isLongestRevMatchAt_iff, isLongestRevMatch_iff_isLongestRevMatch_toSlice]
-
-theorem isLongestRevMatchAtChain_iff_isLongestRevMatchAtChain_toSlice {pat : String} {s : Slice} {pos₁ pos₂ : s.Pos} :
-    IsLongestRevMatchAtChain pat pos₁ pos₂ ↔
-      IsLongestRevMatchAtChain pat.toSlice pos₁ pos₂ := by
-  refine ⟨fun h => ?_, fun h => ?_⟩
-  · induction h with
-    | nil => simp
-    | cons p₂ p₃ _ hmatch ih =>
-      exact .cons _ _ _ ih (isLongestRevMatchAt_iff_isLongestRevMatchAt_toSlice.1 hmatch)
-  · induction h with
-    | nil => simp
-    | cons p₂ p₃ _ hmatch ih =>
-      exact .cons _ _ _ ih (isLongestRevMatchAt_iff_isLongestRevMatchAt_toSlice.2 hmatch)
-
-theorem isLongestRevMatchAtChain_iff {pat : String} {s : Slice} {pos₁ pos₂ : s.Pos} :
-    IsLongestRevMatchAtChain pat pos₁ pos₂ ↔
-      ∃ h n, (s.slice pos₁ pos₂ h).copy = String.join (List.replicate n pat) := by
-  simp [isLongestRevMatchAtChain_iff_isLongestRevMatchAtChain_toSlice,
-    ForwardSliceSearcher.isLongestRevMatchAtChain_iff]
-
-theorem isLongestRevMatchAtChain_startPos_endPos_iff {pat : String} {s : Slice} :
-    IsLongestRevMatchAtChain pat s.startPos s.endPos ↔
-      ∃ n, s.copy = String.join (List.replicate n pat) := by
-  simp [isLongestRevMatchAtChain_iff]
-
 theorem matchesAt_iff_toSlice {pat : String} {s : Slice} {pos : s.Pos} :
     MatchesAt (ρ := String) pat pos ↔ MatchesAt (ρ := Slice) pat.toSlice pos := by
   simp [matchesAt_iff_exists_isLongestMatchAt, isLongestMatchAt_iff_isLongestMatchAt_toSlice]
 
-theorem revMatchesAt_iff_toSlice {pat : String} {s : Slice} {pos : s.Pos} :
-    RevMatchesAt (ρ := String) pat pos ↔ RevMatchesAt (ρ := Slice) pat.toSlice pos := by
-  simp [revMatchesAt_iff_exists_isLongestRevMatchAt,
-    isLongestRevMatchAt_iff_isLongestRevMatchAt_toSlice]
+private theorem toSlice_isEmpty (h : pat ≠ "") : pat.toSlice.isEmpty = false := by
+  rwa [isEmpty_toSlice, isEmpty_eq_false_iff]
 
-theorem isMatch_iff {pat : String} {s : Slice} {pos : s.Pos} :
+theorem isMatch_iff {pat : String} {s : Slice} {pos : s.Pos} (h : pat ≠ "") :
     IsMatch pat pos ↔ (s.sliceTo pos).copy = pat := by
-  rw [isMatch_iff_slice, ForwardSliceSearcher.isMatch_iff]
+  rw [isMatch_iff_slice, ForwardSliceSearcher.isMatch_iff (toSlice_isEmpty h)]
   simp
 
-theorem isRevMatch_iff {pat : String} {s : Slice} {pos : s.Pos} :
-    IsRevMatch pat pos ↔ (s.sliceFrom pos).copy = pat := by
-  rw [isRevMatch_iff_slice, ForwardSliceSearcher.isRevMatch_iff]
-  simp
-
-theorem isLongestMatch_iff {pat : String} {s : Slice} {pos : s.Pos} :
+theorem isLongestMatch_iff {pat : String} {s : Slice} {pos : s.Pos} (h : pat ≠ "") :
     IsLongestMatch pat pos ↔ (s.sliceTo pos).copy = pat := by
-  rw [isLongestMatch_iff_isMatch, isMatch_iff]
+  rw [isLongestMatch_iff_isMatch, isMatch_iff h]
 
-theorem isLongestRevMatch_iff {pat : String} {s : Slice} {pos : s.Pos} :
-    IsLongestRevMatch pat pos ↔ (s.sliceFrom pos).copy = pat := by
-  rw [isLongestRevMatch_iff_isRevMatch, isRevMatch_iff]
-
-theorem isLongestMatchAt_iff {pat : String} {s : Slice} {pos₁ pos₂ : s.Pos} :
+theorem isLongestMatchAt_iff {pat : String} {s : Slice} {pos₁ pos₂ : s.Pos} (h : pat ≠ "") :
     IsLongestMatchAt pat pos₁ pos₂ ↔ ∃ h, (s.slice pos₁ pos₂ h).copy = pat := by
   rw [isLongestMatchAt_iff_isLongestMatchAt_toSlice,
-    ForwardSliceSearcher.isLongestMatchAt_iff]
+    ForwardSliceSearcher.isLongestMatchAt_iff (toSlice_isEmpty h)]
   simp
 
-theorem isLongestRevMatchAt_iff {pat : String} {s : Slice} {pos₁ pos₂ : s.Pos} :
-    IsLongestRevMatchAt pat pos₁ pos₂ ↔ ∃ h, (s.slice pos₁ pos₂ h).copy = pat := by
-  rw [isLongestRevMatchAt_iff_isLongestRevMatchAt_toSlice,
-    ForwardSliceSearcher.isLongestRevMatchAt_iff]
-  simp
-
-theorem isLongestMatchAt_iff_splits {pat : String} {s : Slice} {pos₁ pos₂ : s.Pos} :
-    IsLongestMatchAt pat pos₁ pos₂ ↔
-      ∃ t₁ t₂, pos₁.Splits t₁ (pat ++ t₂) ∧ pos₂.Splits (t₁ ++ pat) t₂ := by
-  rw [isLongestMatchAt_iff_isLongestMatchAt_toSlice,
-    ForwardSliceSearcher.isLongestMatchAt_iff_splits]
-  simp
-
-theorem isLongestRevMatchAt_iff_splits {pat : String} {s : Slice} {pos₁ pos₂ : s.Pos} :
-    IsLongestRevMatchAt pat pos₁ pos₂ ↔
-      ∃ t₁ t₂, pos₁.Splits t₁ (pat ++ t₂) ∧ pos₂.Splits (t₁ ++ pat) t₂ := by
-  rw [isLongestRevMatchAt_iff_isLongestRevMatchAt_toSlice,
-    ForwardSliceSearcher.isLongestRevMatchAt_iff_splits]
-  simp
-
-theorem isLongestMatchAt_iff_extract {pat : String} {s : Slice} {pos₁ pos₂ : s.Pos} (h : pat ≠ "") :
-    IsLongestMatchAt pat pos₁ pos₂ ↔
-      s.copy.toByteArray.extract pos₁.offset.byteIdx pos₂.offset.byteIdx = pat.toByteArray := by
-  rw [isLongestMatchAt_iff_isLongestMatchAt_toSlice,
-    ForwardSliceSearcher.isLongestMatchAt_iff_extract (by simpa)]
-  simp
-
-theorem isLongestRevMatchAt_iff_extract {pat : String} {s : Slice} {pos₁ pos₂ : s.Pos}
+theorem isLongestMatchAt_iff_splits {pat : String} {s : Slice} {pos₁ pos₂ : s.Pos}
     (h : pat ≠ "") :
-    IsLongestRevMatchAt pat pos₁ pos₂ ↔
+    IsLongestMatchAt pat pos₁ pos₂ ↔
+      ∃ t₁ t₂, pos₁.Splits t₁ (pat ++ t₂) ∧ pos₂.Splits (t₁ ++ pat) t₂ := by
+  rw [isLongestMatchAt_iff_isLongestMatchAt_toSlice,
+    ForwardSliceSearcher.isLongestMatchAt_iff_splits (toSlice_isEmpty h)]
+  simp
+
+theorem isLongestMatchAt_iff_extract {pat : String} {s : Slice} {pos₁ pos₂ : s.Pos}
+    (h : pat ≠ "") :
+    IsLongestMatchAt pat pos₁ pos₂ ↔
       s.copy.toByteArray.extract pos₁.offset.byteIdx pos₂.offset.byteIdx = pat.toByteArray := by
-  rw [isLongestRevMatchAt_iff_isLongestRevMatchAt_toSlice,
-    ForwardSliceSearcher.isLongestRevMatchAt_iff_extract (by simpa)]
+  rw [isLongestMatchAt_iff_isLongestMatchAt_toSlice,
+    ForwardSliceSearcher.isLongestMatchAt_iff_extract (toSlice_isEmpty h)]
   simp
 
 theorem offset_of_isLongestMatchAt {pat : String} {s : Slice} {pos₁ pos₂ : s.Pos}
     (h : pat ≠ "") (h' : IsLongestMatchAt pat pos₁ pos₂) :
     pos₂.offset = pos₁.offset.increaseBy pat.utf8ByteSize := by
   rw [show pat.utf8ByteSize = pat.toSlice.utf8ByteSize from utf8ByteSize_toSlice.symm]
-  exact ForwardSliceSearcher.offset_of_isLongestMatchAt (by simpa)
+  exact ForwardSliceSearcher.offset_of_isLongestMatchAt (toSlice_isEmpty h)
     (isLongestMatchAt_iff_isLongestMatchAt_toSlice.1 h')
 
-theorem offset_of_isLongestRevMatchAt {pat : String} {s : Slice} {pos₁ pos₂ : s.Pos}
-    (h : pat ≠ "") (h' : IsLongestRevMatchAt pat pos₁ pos₂) :
-    pos₂.offset = pos₁.offset.increaseBy pat.utf8ByteSize := by
-  rw [show pat.utf8ByteSize = pat.toSlice.utf8ByteSize from utf8ByteSize_toSlice.symm]
-  exact ForwardSliceSearcher.offset_of_isLongestRevMatchAt (by simpa)
-    (isLongestRevMatchAt_iff_isLongestRevMatchAt_toSlice.1 h')
-
-theorem matchesAt_iff_splits {pat : String} {s : Slice} {pos : s.Pos} :
+theorem matchesAt_iff_splits {pat : String} {s : Slice} {pos : s.Pos} (h : pat ≠ "") :
     MatchesAt pat pos ↔ ∃ t₁ t₂, pos.Splits t₁ (pat ++ t₂) := by
   rw [matchesAt_iff_toSlice,
-    ForwardSliceSearcher.matchesAt_iff_splits]
+    ForwardSliceSearcher.matchesAt_iff_splits (toSlice_isEmpty h)]
   simp
 
-theorem revMatchesAt_iff_splits {pat : String} {s : Slice} {pos : s.Pos} :
-    RevMatchesAt pat pos ↔ ∃ t₁ t₂, pos.Splits (t₁ ++ pat) t₂ := by
-  rw [revMatchesAt_iff_toSlice,
-    ForwardSliceSearcher.revMatchesAt_iff_splits]
-  simp
-
-theorem exists_matchesAt_iff_eq_append {pat : String} {s : Slice} :
+theorem exists_matchesAt_iff_eq_append {pat : String} {s : Slice} (h : pat ≠ "") :
     (∃ (pos : s.Pos), MatchesAt pat pos) ↔ ∃ t₁ t₂, s.copy = t₁ ++ pat ++ t₂ := by
-  simp only [matchesAt_iff_splits]
+  simp only [matchesAt_iff_splits h]
   constructor
   · rintro ⟨pos, t₁, t₂, hsplit⟩
     exact ⟨t₁, t₂, by rw [hsplit.eq_append, append_assoc]⟩
@@ -477,58 +230,35 @@ theorem exists_matchesAt_iff_eq_append {pat : String} {s : Slice} :
         ⟨t₁, pat ++ t₂, by rw [← append_assoc]; exact heq, rfl⟩
     exact ⟨s.pos _ hvalid, t₁, t₂, ⟨by rw [← append_assoc]; exact heq, by simp⟩⟩
 
-theorem exists_revMatchesAt_iff_eq_append {pat : String} {s : Slice} :
-    (∃ (pos : s.Pos), RevMatchesAt pat pos) ↔ ∃ t₁ t₂, s.copy = t₁ ++ pat ++ t₂ := by
-  rw [show (∃ (pos : s.Pos), RevMatchesAt (ρ := String) pat pos) ↔
-      (∃ (pos : s.Pos), RevMatchesAt (ρ := Slice) pat.toSlice pos) from by
-    simp [revMatchesAt_iff_toSlice],
-    ForwardSliceSearcher.exists_revMatchesAt_iff_eq_append]
-  simp
-
 theorem matchesAt_iff_isLongestMatchAt {pat : String} {s : Slice} {pos : s.Pos}
     (h : pat ≠ "") :
     MatchesAt pat pos ↔ ∃ (h : (pos.offset.increaseBy pat.utf8ByteSize).IsValidForSlice s),
       IsLongestMatchAt pat pos (s.pos _ h) := by
   have key := ForwardSliceSearcher.matchesAt_iff_isLongestMatchAt (pat := pat.toSlice)
-    (by simpa) (pos := pos)
+    (toSlice_isEmpty h) (pos := pos)
   simp only [utf8ByteSize_toSlice, ← isLongestMatchAt_iff_isLongestMatchAt_toSlice] at key
   rwa [matchesAt_iff_toSlice]
 
-theorem revMatchesAt_iff_isLongestRevMatchAt {pat : String} {s : Slice} {pos : s.Pos}
-    (h : pat ≠ "") :
-    RevMatchesAt pat pos ↔
-      ∃ (h : (pos.offset.decreaseBy pat.utf8ByteSize).IsValidForSlice s),
-        IsLongestRevMatchAt pat (s.pos _ h) pos := by
-  have key := ForwardSliceSearcher.revMatchesAt_iff_isLongestRevMatchAt (pat := pat.toSlice)
-    (by simpa) (pos := pos)
-  simp only [utf8ByteSize_toSlice, ← isLongestRevMatchAt_iff_isLongestRevMatchAt_toSlice] at key
-  rwa [revMatchesAt_iff_toSlice]
-
 theorem matchesAt_iff_getElem {pat : String} {s : Slice} {pos : s.Pos} (h : pat ≠ "") :
     MatchesAt pat pos ↔
       ∃ (h : pos.offset.byteIdx + pat.toByteArray.size ≤ s.copy.toByteArray.size),
         ∀ (j), (hj : j < pat.toByteArray.size) →
           pat.toByteArray[j] = s.copy.toByteArray[pos.offset.byteIdx + j] := by
   have key := ForwardSliceSearcher.matchesAt_iff_getElem (pat := pat.toSlice)
-    (by simpa) (pos := pos)
+    (toSlice_isEmpty h) (pos := pos)
   simp only [copy_toSlice] at key
   rwa [matchesAt_iff_toSlice]
 
 theorem le_of_matchesAt {pat : String} {s : Slice} {pos : s.Pos} (h : pat ≠ "")
     (h' : MatchesAt pat pos) : pos.offset.increaseBy pat.utf8ByteSize ≤ s.rawEndPos := by
   rw [show pat.utf8ByteSize = pat.toSlice.utf8ByteSize from utf8ByteSize_toSlice.symm]
-  exact ForwardSliceSearcher.le_of_matchesAt (by simpa)
+  exact ForwardSliceSearcher.le_of_matchesAt (toSlice_isEmpty h)
     (matchesAt_iff_toSlice.1 h')
 
 theorem matchesAt_iff_matchesAt_toSlice {pat : String} {s : Slice}
     {pos : s.Pos} : MatchesAt pat pos ↔ MatchesAt pat.toSlice pos := by
   simp [matchesAt_iff_exists_isLongestMatchAt, isLongestMatchAt_iff_isLongestMatchAt_toSlice]
 
-theorem revMatchesAt_iff_revMatchesAt_toSlice {pat : String} {s : Slice}
-    {pos : s.Pos} : RevMatchesAt pat pos ↔ RevMatchesAt pat.toSlice pos := by
-  simp [revMatchesAt_iff_exists_isLongestRevMatchAt,
-    isLongestRevMatchAt_iff_isLongestRevMatchAt_toSlice]
-
 theorem toSearcher_eq {pat : String} {s : Slice} :
     ToForwardSearcher.toSearcher pat s = ToForwardSearcher.toSearcher pat.toSlice s := (rfl)
 
@@ -545,21 +275,6 @@ theorem isValidSearchFrom_iff_isValidSearchFrom_toSlice {pat : String}
     | matched => simp_all [IsValidSearchFrom.matched, isLongestMatchAt_iff_isLongestMatchAt_toSlice]
     | mismatched => simp_all [IsValidSearchFrom.mismatched, matchesAt_iff_matchesAt_toSlice]
 
-theorem isValidRevSearchFrom_iff_isValidRevSearchFrom_toSlice {pat : String}
-    {s : Slice} {pos : s.Pos} {l : List (SearchStep s)} :
-    IsValidRevSearchFrom pat pos l ↔ IsValidRevSearchFrom pat.toSlice pos l := by
-  refine ⟨fun h => ?_, fun h => ?_⟩
-  · induction h with
-    | startPos => simpa using IsValidRevSearchFrom.startPos
-    | matched => simp_all [IsValidRevSearchFrom.matched,
-        isLongestRevMatchAt_iff_isLongestRevMatchAt_toSlice]
-    | mismatched => simp_all [IsValidRevSearchFrom.mismatched, revMatchesAt_iff_revMatchesAt_toSlice]
-  · induction h with
-    | startPos => simpa using IsValidRevSearchFrom.startPos
-    | matched => simp_all [IsValidRevSearchFrom.matched,
-        isLongestRevMatchAt_iff_isLongestRevMatchAt_toSlice]
-    | mismatched => simp_all [IsValidRevSearchFrom.mismatched, revMatchesAt_iff_revMatchesAt_toSlice]
-
 end ForwardStringSearcher
 
 end String.Slice.Pattern.Model

src/Init/Data/String/Lemmas/Pattern/String/ForwardPattern.lean

@@ -56,7 +56,7 @@ theorem skipPrefix?_eq_some_iff {pat s : Slice} {pos : s.Pos} :
     simp only [reduceCtorEq, false_iff]
     intro heq
     have := h (s.sliceFrom pos).copy
-    simp [← heq, -sliceTo_append_sliceFrom, pos.splits.eq_append] at this
+    simp [← heq, pos.splits.eq_append] at this
 
 theorem isSome_skipPrefix? {pat s : Slice} : (skipPrefix? pat s).isSome = startsWith pat s := by
   fun_cases skipPrefix? <;> simp_all
@@ -76,11 +76,12 @@ namespace Model.ForwardSliceSearcher
 
 open Pattern.ForwardSliceSearcher
 
-public instance {pat : Slice} : LawfulForwardPatternModel pat where
-  skipPrefixOfNonempty?_eq _ := rfl
-  startsWith_eq _ := isSome_skipPrefix?.symm
+public theorem lawfulForwardPatternModel {pat : Slice} (hpat : pat.isEmpty = false) :
+    LawfulForwardPatternModel pat where
+  skipPrefixOfNonempty?_eq h := rfl
+  startsWith_eq s := isSome_skipPrefix?.symm
   skipPrefix?_eq_some_iff pos := by
-    simp [ForwardPattern.skipPrefix?, skipPrefix?_eq_some_iff, isLongestMatch_iff]
+    simp [ForwardPattern.skipPrefix?, skipPrefix?_eq_some_iff, isLongestMatch_iff hpat]
 
 end Model.ForwardSliceSearcher
 
@@ -88,107 +89,15 @@ namespace Model.ForwardStringSearcher
 
 open Pattern.ForwardSliceSearcher
 
-public instance {pat : String} : LawfulForwardPatternModel pat where
-  skipPrefixOfNonempty?_eq _ := rfl
-  startsWith_eq _ := isSome_skipPrefix?.symm
+public theorem lawfulForwardPatternModel {pat : String} (hpat : pat ≠ "") :
+    LawfulForwardPatternModel pat where
+  skipPrefixOfNonempty?_eq h := rfl
+  startsWith_eq s := isSome_skipPrefix?.symm
   skipPrefix?_eq_some_iff pos := by
-    simp [ForwardPattern.skipPrefix?, skipPrefix?_eq_some_iff, isLongestMatch_iff]
+    simp [ForwardPattern.skipPrefix?, skipPrefix?_eq_some_iff, isLongestMatch_iff hpat]
 
 end Model.ForwardStringSearcher
 
-namespace BackwardSliceSearcher
-
-theorem endsWith_iff {pat s : Slice} : endsWith pat s ↔ ∃ t, s.copy = t ++ pat.copy := by
-  rw [endsWith]
-  simp [Internal.memcmpSlice_eq_true_iff, utf8ByteSize_eq_size_toByteArray_copy, -size_toByteArray]
-  generalize pat.copy = pat
-  generalize s.copy = s
-  refine ⟨fun ⟨h₁, h₂⟩ => ?_, ?_⟩
-  · rw [Nat.sub_add_cancel h₁] at h₂
-    suffices (s.rawEndPos.unoffsetBy pat.rawEndPos).IsValid s by
-      have h₃ : (s.sliceFrom (s.pos _ this)).copy = pat := by
-        rw [← toByteArray_inj, (s.pos _ this).splits.toByteArray_right_eq]
-        simpa [offset_pos, Pos.Raw.byteIdx_unoffsetBy, byteIdx_rawEndPos]
-      have := (s.pos _ this).splits
-      rw [h₃] at this
-      exact ⟨_, this.eq_append⟩
-    rw [Pos.Raw.isValid_iff_isValidUTF8_extract_utf8ByteSize]
-    refine ⟨by simp [Pos.Raw.le_iff, Pos.Raw.byteIdx_unoffsetBy], ?_⟩
-    simp only [size_toByteArray] at h₂
-    simpa [Pos.Raw.byteIdx_unoffsetBy, byteIdx_rawEndPos, h₂] using pat.isValidUTF8
-  · rintro ⟨t, rfl⟩
-    exact ⟨by simp, by rw [Nat.sub_add_cancel (by simp)]; exact
-      ByteArray.extract_append_eq_right (by simp) (by simp)⟩
-
-theorem skipSuffix?_eq_some_iff {pat s : Slice} {pos : s.Pos} :
-    skipSuffix? pat s = some pos ↔ (s.sliceFrom pos).copy = pat.copy := by
-  fun_cases skipSuffix? with
-  | case1 h =>
-    simp only [Option.some.injEq]
-    obtain ⟨t, ht⟩ := endsWith_iff.1 h
-    have hpc : pat.copy.utf8ByteSize = pat.utf8ByteSize := Slice.utf8ByteSize_copy
-    have hsz : s.utf8ByteSize = t.utf8ByteSize + pat.utf8ByteSize := by
-      have := congrArg String.utf8ByteSize ht
-      simp only [utf8ByteSize_append, Slice.utf8ByteSize_copy] at this
-      exact this
-    have hoff : (s.endPos.offset.unoffsetBy pat.rawEndPos) = t.rawEndPos := by
-      ext
-      simp only [offset_endPos, Pos.Raw.byteIdx_unoffsetBy, byteIdx_rawEndPos,
-        String.byteIdx_rawEndPos]
-      omega
-    have hval : (s.endPos.offset.unoffsetBy pat.rawEndPos).IsValidForSlice s :=
-      Pos.Raw.isValidForSlice_iff_exists_append.mpr ⟨t, pat.copy, ht, hoff⟩
-    have hsp : (s.pos _ hval).Splits t pat.copy := ⟨ht, hoff⟩
-    rw [Slice.pos!_eq_pos hval]
-    exact ⟨(· ▸ hsp.copy_sliceFrom_eq),
-      fun h => hsp.pos_eq_of_eq_right (h ▸ pos.splits)⟩
-  | case2 h =>
-    simp only [endsWith_iff, not_exists] at h
-    simp only [reduceCtorEq, false_iff]
-    intro heq
-    have := h (s.sliceTo pos).copy
-    simp [← heq, -sliceTo_append_sliceFrom, pos.splits.eq_append] at this
-
-theorem isSome_skipSuffix? {pat s : Slice} : (skipSuffix? pat s).isSome = endsWith pat s := by
-  fun_cases skipSuffix? <;> simp_all
-
-public theorem endsWith_of_isEmpty {pat s : Slice} (hpat : pat.isEmpty = true) :
-    BackwardPattern.endsWith pat s = true := by
-  suffices pat.copy = "" by simp [BackwardPattern.endsWith, endsWith_iff, this]
-  simpa
-
-public theorem skipSuffix?_of_isEmpty {pat s : Slice} (hpat : pat.isEmpty = true) :
-    BackwardPattern.skipSuffix? pat s = some s.endPos := by
-  simpa [BackwardPattern.skipSuffix?, skipSuffix?_eq_some_iff]
-
-end BackwardSliceSearcher
-
-namespace Model.BackwardSliceSearcher
-
-open Pattern.BackwardSliceSearcher
-
-public instance {pat : Slice} : LawfulBackwardPatternModel pat where
-  skipSuffixOfNonempty?_eq _ := rfl
-  endsWith_eq _ := isSome_skipSuffix?.symm
-  skipSuffix?_eq_some_iff pos := by
-    simp [BackwardPattern.skipSuffix?, skipSuffix?_eq_some_iff,
-      ForwardSliceSearcher.isLongestRevMatch_iff]
-
-end Model.BackwardSliceSearcher
-
-namespace Model.BackwardStringSearcher
-
-open Pattern.BackwardSliceSearcher
-
-public instance {pat : String} : LawfulBackwardPatternModel pat where
-  skipSuffixOfNonempty?_eq _ := rfl
-  endsWith_eq _ := isSome_skipSuffix?.symm
-  skipSuffix?_eq_some_iff pos := by
-    simp [BackwardPattern.skipSuffix?, skipSuffix?_eq_some_iff,
-      ForwardStringSearcher.isLongestRevMatch_iff]
-
-end Model.BackwardStringSearcher
-
 end Pattern
 
 public theorem startsWith_string_eq_startsWith_toSlice {pat : String} {s : Slice} :
@@ -207,22 +116,19 @@ public theorem Pattern.ForwardPattern.skipPrefix?_string_eq_skipPrefix?_toSlice
     {pat : String} {s : Slice} :
     skipPrefix? pat s = skipPrefix? pat.toSlice s := (rfl)
 
-public theorem Pos.skip?_string_eq_skip?_toSlice {pat : String} {s : Slice} {pos : s.Pos} :
-    pos.skip? pat = pos.skip? pat.toSlice := (rfl)
-
 public theorem Pos.skipWhile_string_eq_skipWhile_toSlice {pat : String} {s : Slice}
     (curr : s.Pos) :
     Pos.skipWhile curr pat = Pos.skipWhile curr pat.toSlice := by
   fun_induction Pos.skipWhile curr pat with
   | case1 pos nextCurr h₁ h₂ ih =>
     conv => rhs; rw [Pos.skipWhile]
-    simp [← Pos.skip?_string_eq_skip?_toSlice, h₁, h₂, ih]
+    simp [← Pattern.ForwardPattern.skipPrefix?_string_eq_skipPrefix?_toSlice, h₁, h₂, ih]
   | case2 pos nextCurr h ih =>
     conv => rhs; rw [Pos.skipWhile]
-    simp [← Pos.skip?_string_eq_skip?_toSlice, h, ih]
+    simp [← Pattern.ForwardPattern.skipPrefix?_string_eq_skipPrefix?_toSlice, h, ih]
   | case3 pos h =>
     conv => rhs; rw [Pos.skipWhile]
-    simp [← Pos.skip?_string_eq_skip?_toSlice, h]
+    simp [← Pattern.ForwardPattern.skipPrefix?_string_eq_skipPrefix?_toSlice]
 
 public theorem skipPrefixWhile_string_eq_skipPrefixWhile_toSlice {pat : String} {s : Slice} :
     s.skipPrefixWhile pat = s.skipPrefixWhile pat.toSlice :=
@@ -238,7 +144,7 @@ public theorem takeWhile_string_eq_takeWhile_toSlice {pat : String} {s : Slice}
 
 public theorem all_string_eq_all_toSlice {pat : String} {s : Slice} :
     s.all pat = s.all pat.toSlice := by
-  simp only [all, skipPrefixWhile_string_eq_skipPrefixWhile_toSlice]
+  simp only [all, dropWhile_string_eq_dropWhile_toSlice]
 
 public theorem endsWith_string_eq_endsWith_toSlice {pat : String} {s : Slice} :
     s.endsWith pat = s.endsWith pat.toSlice := (rfl)
@@ -256,22 +162,19 @@ public theorem Pattern.BackwardPattern.skipSuffix?_string_eq_skipSuffix?_toSlice
     {pat : String} {s : Slice} :
     skipSuffix? pat s = skipSuffix? pat.toSlice s := (rfl)
 
-public theorem Pos.revSkip?_string_eq_revSkip?_toSlice {pat : String} {s : Slice} {pos : s.Pos} :
-    pos.revSkip? pat = pos.revSkip? pat.toSlice := (rfl)
-
 public theorem Pos.revSkipWhile_string_eq_revSkipWhile_toSlice {pat : String} {s : Slice}
     (curr : s.Pos) :
     Pos.revSkipWhile curr pat = Pos.revSkipWhile curr pat.toSlice := by
   fun_induction Pos.revSkipWhile curr pat with
   | case1 pos nextCurr h₁ h₂ ih =>
     conv => rhs; rw [Pos.revSkipWhile]
-    simp [← Pos.revSkip?_string_eq_revSkip?_toSlice, h₁, h₂, ih]
+    simp [← Pattern.BackwardPattern.skipSuffix?_string_eq_skipSuffix?_toSlice, h₁, h₂, ih]
   | case2 pos nextCurr h ih =>
     conv => rhs; rw [Pos.revSkipWhile]
-    simp [← Pos.revSkip?_string_eq_revSkip?_toSlice, h, ih]
+    simp [← Pattern.BackwardPattern.skipSuffix?_string_eq_skipSuffix?_toSlice, h, ih]
   | case3 pos h =>
     conv => rhs; rw [Pos.revSkipWhile]
-    simp [← Pos.revSkip?_string_eq_revSkip?_toSlice, h]
+    simp [← Pattern.BackwardPattern.skipSuffix?_string_eq_skipSuffix?_toSlice]
 
 public theorem skipSuffixWhile_string_eq_skipSuffixWhile_toSlice {pat : String} {s : Slice} :
     s.skipSuffixWhile pat = s.skipSuffixWhile pat.toSlice :=
@@ -285,8 +188,4 @@ public theorem takeEndWhile_string_eq_takeEndWhile_toSlice {pat : String} {s : S
     s.takeEndWhile pat = s.takeEndWhile pat.toSlice := by
   simp only [takeEndWhile]; exact congrArg _ skipSuffixWhile_string_eq_skipSuffixWhile_toSlice
 
-public theorem revAll_string_eq_revAll_toSlice {pat : String} {s : Slice} :
-    s.revAll pat = s.revAll pat.toSlice := by
-  simp [revAll, skipSuffixWhile_string_eq_skipSuffixWhile_toSlice]
-
 end String.Slice

src/Init/Data/String/Lemmas/Pattern/TakeDrop/Char.lean

@@ -11,8 +11,6 @@ public import Init.Data.String.TakeDrop
 import Init.Data.String.Lemmas.Pattern.TakeDrop.Basic
 import Init.Data.String.Lemmas.Pattern.Char
 import Init.Data.Option.Lemmas
-import Init.Data.String.Lemmas.FindPos
-import Init.Data.List.Sublist
 
 public section
 
@@ -54,113 +52,7 @@ theorem startsWith_char_eq_false_iff_forall_append {c : Char} {s : Slice} :
 
 theorem eq_append_of_dropPrefix?_char_eq_some {c : Char} {s res : Slice} (h : s.dropPrefix? c = some res) :
     s.copy = singleton c ++ res.copy := by
-  simpa [PatternModel.Matches] using Pattern.Model.eq_append_of_dropPrefix?_eq_some h
-
-theorem Pos.skip?_char_eq_some_iff {c : Char} {s : Slice} {pos res : s.Pos} :
-    pos.skip? c = some res ↔ ∃ h, res = pos.next h ∧ pos.get h = c := by
-  simp [Pattern.Model.Pos.skip?_eq_some_iff, Char.isLongestMatchAt_iff]
-
-@[simp]
-theorem Pos.skip?_char_eq_none_iff {c : Char} {s : Slice} {pos : s.Pos} :
-    pos.skip? c = none ↔ ∀ h, pos.get h ≠ c := by
-  simp [Pattern.Model.Pos.skip?_eq_none_iff, Char.matchesAt_iff]
-
-theorem Pos.get_skipWhile_char_ne {c : Char} {s : Slice} {pos : s.Pos} {h} :
-    (pos.skipWhile c).get h ≠ c := by
-  have := Pattern.Model.Pos.not_matchesAt_skipWhile c pos
-  simp_all [Char.matchesAt_iff]
-
-theorem Pos.skipWhile_char_eq_self_iff_get {c : Char} {s : Slice} {pos : s.Pos} :
-    pos.skipWhile c = pos ↔ ∀ h, pos.get h ≠ c := by
-  simp [Pattern.Model.Pos.skipWhile_eq_self_iff, Char.matchesAt_iff]
-
-theorem Pos.get_eq_of_lt_skipWhile_char {c : Char} {s : Slice} {pos pos' : s.Pos}
-    (h₁ : pos ≤ pos') (h₂ : pos' < pos.skipWhile c) : pos'.get (ne_endPos_of_lt h₂) = c :=
-  (Char.isLongestMatchAtChain_iff.1 (Pattern.Model.Pos.isLongestMatchAtChain_skipWhile c pos)).2 _ h₁ h₂
-
-theorem get_skipPrefixWhile_char_ne {c : Char} {s : Slice} {h} :
-    (s.skipPrefixWhile c).get h ≠ c := by
-  simp [skipPrefixWhile_eq_skipWhile_startPos, Pos.get_skipWhile_char_ne]
-
-theorem get_eq_of_lt_skipPrefixWhile_char {c : Char} {s : Slice} {pos : s.Pos} (h : pos < s.skipPrefixWhile c) :
-    pos.get (Pos.ne_endPos_of_lt h) = c :=
-  Pos.get_eq_of_lt_skipWhile_char (Pos.startPos_le _) (by rwa [skipPrefixWhile_eq_skipWhile_startPos] at h)
-
-@[simp]
-theorem all_char_iff {c : Char} {s : Slice} : s.all c ↔ s.copy.toList = List.replicate s.copy.length c := by
-  rw [Bool.eq_iff_iff]
-  simp [Pattern.Model.all_eq_true_iff, Char.isLongestMatchAtChain_startPos_endPos_iff_toList]
-
-theorem Pos.revSkip?_char_eq_some_iff {c : Char} {s : Slice} {pos res : s.Pos} :
-    pos.revSkip? c = some res ↔ ∃ h, res = pos.prev h ∧ (pos.prev h).get (by simp) = c := by
-  simp [Pattern.Model.Pos.revSkip?_eq_some_iff, Char.isLongestRevMatchAt_iff]
-
-@[simp]
-theorem Pos.revSkip?_char_eq_none_iff {c : Char} {s : Slice} {pos : s.Pos} :
-    pos.revSkip? c = none ↔ ∀ h, (pos.prev h).get (by simp) ≠ c := by
-  simp [Pattern.Model.Pos.revSkip?_eq_none_iff, Char.revMatchesAt_iff]
-
-theorem Pos.get_revSkipWhile_char_ne {c : Char} {s : Slice} {pos : s.Pos} {h} :
-    ((pos.revSkipWhile c).prev h).get (by simp) ≠ c := by
-  have := Pattern.Model.Pos.not_revMatchesAt_revSkipWhile c pos
-  simp_all [Char.revMatchesAt_iff]
-
-theorem Pos.revSkipWhile_char_eq_self_iff_get {c : Char} {s : Slice} {pos : s.Pos} :
-    pos.revSkipWhile c = pos ↔ ∀ h, (pos.prev h).get (by simp) ≠ c := by
-  simp [Pattern.Model.Pos.revSkipWhile_eq_self_iff, Char.revMatchesAt_iff]
-
-theorem Pos.get_eq_of_revSkipWhile_le_char {c : Char} {s : Slice} {pos pos' : s.Pos}
-    (h₁ : pos' < pos) (h₂ : pos.revSkipWhile c ≤ pos') : pos'.get (Pos.ne_endPos_of_lt h₁) = c :=
-  (Char.isLongestRevMatchAtChain_iff.1 (Pattern.Model.Pos.isLongestRevMatchAtChain_revSkipWhile c pos)).2 _ h₂ h₁
-
-theorem get_skipSuffixWhile_char_ne {c : Char} {s : Slice} {h} :
-    ((s.skipSuffixWhile c).prev h).get (by simp) ≠ c := by
-  simp [skipSuffixWhile_eq_revSkipWhile_endPos, Pos.get_revSkipWhile_char_ne]
-
-theorem get_eq_of_skipSuffixWhile_le_char {c : Char} {s : Slice} {pos : s.Pos}
-    (h : s.skipSuffixWhile c ≤ pos) (h' : pos < s.endPos) :
-    pos.get (Pos.ne_endPos_of_lt h') = c :=
-  Pos.get_eq_of_revSkipWhile_le_char h' (by rwa [skipSuffixWhile_eq_revSkipWhile_endPos] at h)
-
-@[simp]
-theorem revAll_char_iff {c : Char} {s : Slice} : s.revAll c ↔ s.copy.toList = List.replicate s.copy.length c := by
-  rw [Bool.eq_iff_iff]
-  simp [Pattern.Model.revAll_eq_true_iff, Char.isLongestRevMatchAtChain_startPos_endPos_iff_toList]
-
-theorem skipSuffix?_char_eq_some_iff {c : Char} {s : Slice} {pos : s.Pos} :
-    s.skipSuffix? c = some pos ↔ ∃ h, pos = s.endPos.prev h ∧ (s.endPos.prev h).get (by simp) = c := by
-  rw [Pattern.Model.skipSuffix?_eq_some_iff, Char.isLongestRevMatch_iff]
-
-theorem endsWith_char_iff_get {c : Char} {s : Slice} :
-    s.endsWith c ↔ ∃ h, (s.endPos.prev h).get (by simp) = c := by
-  simp [Pattern.Model.endsWith_iff, Char.revMatchesAt_iff]
-
-theorem endsWith_char_eq_false_iff_get {c : Char} {s : Slice} :
-    s.endsWith c = false ↔ ∀ h, (s.endPos.prev h).get (by simp) ≠ c := by
-  simp [Pattern.Model.endsWith_eq_false_iff, Char.revMatchesAt_iff]
-
-theorem endsWith_char_iff_exists_append {c : Char} {s : Slice} :
-    s.endsWith c ↔ ∃ t, s.copy = t ++ singleton c := by
-  rw [Pattern.Model.endsWith_iff, Char.revMatchesAt_iff_splits]
-  simp only [splits_endPos_iff, exists_eq_right, eq_comm (a := s.copy)]
-
-theorem endsWith_char_eq_getLast? {c : Char} {s : Slice} :
-    s.endsWith c = (s.copy.toList.getLast? == some c) := by
-  rw [Bool.eq_iff_iff, endsWith_char_iff_exists_append, beq_iff_eq,
-    ← List.singleton_suffix_iff_getLast?_eq_some, List.suffix_iff_exists_eq_append]
-  constructor
-  · rintro ⟨t, ht⟩
-    exact ⟨t.toList, by rw [ht, toList_append, toList_singleton]⟩
-  · rintro ⟨l, hl⟩
-    exact ⟨ofList l, by rw [← toList_inj, toList_append, toList_singleton, toList_ofList]; exact hl⟩
-
-theorem endsWith_char_eq_false_iff_forall_append {c : Char} {s : Slice} :
-    s.endsWith c = false ↔ ∀ t, s.copy ≠ t ++ singleton c := by
-  simp [← Bool.not_eq_true, endsWith_char_iff_exists_append]
-
-theorem eq_append_of_dropSuffix?_char_eq_some {c : Char} {s res : Slice} (h : s.dropSuffix? c = some res) :
-    s.copy = res.copy ++ singleton c := by
-  simpa [PatternModel.Matches] using Pattern.Model.eq_append_of_dropSuffix?_eq_some h
+  simpa [ForwardPatternModel.Matches] using Pattern.Model.eq_append_of_dropPrefix?_eq_some h
 
 end Slice
 
@@ -171,19 +63,19 @@ theorem skipPrefix?_char_eq_some_iff {c : Char} {s : String} {pos : s.Pos} :
 
 theorem startsWith_char_iff_get {c : Char} {s : String} :
     s.startsWith c ↔ ∃ h, s.startPos.get h = c := by
-  simp [← startsWith_toSlice, Slice.startsWith_char_iff_get]
+  simp [startsWith_eq_startsWith_toSlice, Slice.startsWith_char_iff_get]
 
 theorem startsWith_char_eq_false_iff_get {c : Char} {s : String} :
     s.startsWith c = false ↔ ∀ h, s.startPos.get h ≠ c := by
-  simp [← startsWith_toSlice, Slice.startsWith_char_eq_false_iff_get]
+  simp [startsWith_eq_startsWith_toSlice, Slice.startsWith_char_eq_false_iff_get]
 
 theorem startsWith_char_eq_head? {c : Char} {s : String} :
     s.startsWith c = (s.toList.head? == some c) := by
-  simp [← startsWith_toSlice, Slice.startsWith_char_eq_head?]
+  simp [startsWith_eq_startsWith_toSlice, Slice.startsWith_char_eq_head?]
 
 theorem startsWith_char_iff_exists_append {c : Char} {s : String} :
     s.startsWith c ↔ ∃ t, s = singleton c ++ t := by
-  simp [← startsWith_toSlice, Slice.startsWith_char_iff_exists_append]
+  simp [startsWith_eq_startsWith_toSlice, Slice.startsWith_char_iff_exists_append]
 
 theorem startsWith_char_eq_false_iff_forall_append {c : Char} {s : String} :
     s.startsWith c = false ↔ ∀ t, s ≠ singleton c ++ t := by
@@ -194,34 +86,4 @@ theorem eq_append_of_dropPrefix?_char_eq_some {c : Char} {s : String} {res : Sli
   rw [dropPrefix?_eq_dropPrefix?_toSlice] at h
   simpa using Slice.eq_append_of_dropPrefix?_char_eq_some h
 
-theorem skipSuffix?_char_eq_some_iff {c : Char} {s : String} {pos : s.Pos} :
-    s.skipSuffix? c = some pos ↔ ∃ h, pos = s.endPos.prev h ∧ (s.endPos.prev h).get (by simp) = c := by
-  simp [skipSuffix?_eq_skipSuffix?_toSlice, Slice.skipSuffix?_char_eq_some_iff, ← Pos.toSlice_inj,
-    Pos.prev_toSlice]
-
-theorem endsWith_char_iff_get {c : Char} {s : String} :
-    s.endsWith c ↔ ∃ h, (s.endPos.prev h).get (by simp) = c := by
-  simp [← endsWith_toSlice, Slice.endsWith_char_iff_get, Pos.prev_toSlice]
-
-theorem endsWith_char_eq_false_iff_get {c : Char} {s : String} :
-    s.endsWith c = false ↔ ∀ h, (s.endPos.prev h).get (by simp) ≠ c := by
-  simp [← endsWith_toSlice, Slice.endsWith_char_eq_false_iff_get, Pos.prev_toSlice]
-
-theorem endsWith_char_eq_getLast? {c : Char} {s : String} :
-    s.endsWith c = (s.toList.getLast? == some c) := by
-  simp [← endsWith_toSlice, Slice.endsWith_char_eq_getLast?]
-
-theorem endsWith_char_iff_exists_append {c : Char} {s : String} :
-    s.endsWith c ↔ ∃ t, s = t ++ singleton c := by
-  simp [← endsWith_toSlice, Slice.endsWith_char_iff_exists_append]
-
-theorem endsWith_char_eq_false_iff_forall_append {c : Char} {s : String} :
-    s.endsWith c = false ↔ ∀ t, s ≠ t ++ singleton c := by
-  simp [← Bool.not_eq_true, endsWith_char_iff_exists_append]
-
-theorem eq_append_of_dropSuffix?_char_eq_some {c : Char} {s : String} {res : Slice} (h : s.dropSuffix? c = some res) :
-    s = res.copy ++ singleton c := by
-  rw [dropSuffix?_eq_dropSuffix?_toSlice] at h
-  simpa using Slice.eq_append_of_dropSuffix?_char_eq_some h
-
 end String

src/Init/Data/String/Lemmas/Pattern/TakeDrop/Pred.lean

@@ -8,16 +8,10 @@ module
 prelude
 public import Init.Data.String.Slice
 public import Init.Data.String.TakeDrop
-public import Init.Data.String.Lemmas.Order
 import Init.Data.String.Lemmas.Pattern.TakeDrop.Basic
 import Init.Data.String.Lemmas.Pattern.Pred
 import Init.Data.Option.Lemmas
-import Init.Data.String.Lemmas.FindPos
-import Init.Data.String.Lemmas.Intercalate
 import Init.ByCases
-import Init.Data.Order.Lemmas
-import Init.Data.String.OrderInstances
-import Init.Data.String.Lemmas.Basic
 
 public section
 
@@ -51,83 +45,9 @@ theorem startsWith_bool_eq_head? {p : Char → Bool} {s : Slice} :
 
 theorem eq_append_of_dropPrefix?_bool_eq_some {p : Char → Bool} {s res : Slice} (h : s.dropPrefix? p = some res) :
     ∃ c, s.copy = singleton c ++ res.copy ∧ p c = true := by
-  obtain ⟨_, ⟨c, ⟨rfl, h₁⟩⟩, h₂⟩ := by simpa [PatternModel.Matches] using Pattern.Model.eq_append_of_dropPrefix?_eq_some h
+  obtain ⟨_, ⟨c, ⟨rfl, h₁⟩⟩, h₂⟩ := by simpa [ForwardPatternModel.Matches] using Pattern.Model.eq_append_of_dropPrefix?_eq_some h
   exact ⟨_, h₂, h₁⟩
 
-@[simp]
-theorem Pos.skip?_bool_eq_some_iff {p : Char → Bool} {s : Slice} {pos res : s.Pos} :
-    pos.skip? p = some res ↔ ∃ h, res = pos.next h ∧ p (pos.get h) := by
-  simp [Pattern.Model.Pos.skip?_eq_some_iff, CharPred.isLongestMatchAt_iff]
-
-@[simp]
-theorem Pos.skip?_bool_eq_none_iff {p : Char → Bool} {s : Slice} {pos : s.Pos} :
-    pos.skip? p = none ↔ ∀ h, p (pos.get h) = false := by
-  simp [Pattern.Model.Pos.skip?_eq_none_iff, CharPred.matchesAt_iff]
-
-theorem Pos.apply_skipWhile_bool_eq_false {p : Char → Bool} {s : Slice} {pos : s.Pos} {h} :
-    p ((pos.skipWhile p).get h) = false := by
-  have := Pattern.Model.Pos.not_matchesAt_skipWhile p pos
-  simp_all [CharPred.matchesAt_iff]
-
-theorem Pos.skipWhile_bool_eq_self_iff_get {p : Char → Bool} {s : Slice} {pos : s.Pos} :
-    pos.skipWhile p = pos ↔ ∀ h, p (pos.get h) = false := by
-  simp [Pattern.Model.Pos.skipWhile_eq_self_iff, CharPred.matchesAt_iff]
-
-theorem Pos.apply_eq_true_of_lt_skipWhile_bool {p : Char → Bool} {s : Slice} {pos pos' : s.Pos}
-    (h₁ : pos ≤ pos') (h₂ : pos' < pos.skipWhile p) : p (pos'.get (ne_endPos_of_lt h₂)) = true :=
-  (CharPred.isLongestMatchAtChain_iff.1 (Pattern.Model.Pos.isLongestMatchAtChain_skipWhile p pos)).2 _ h₁ h₂
-
-theorem apply_skipPrefixWhile_bool_eq_false {p : Char → Bool} {s : Slice} {h} :
-    p ((s.skipPrefixWhile p).get h) = false := by
-  simp [skipPrefixWhile_eq_skipWhile_startPos, Pos.apply_skipWhile_bool_eq_false]
-
-theorem apply_eq_true_of_lt_skipPrefixWhile_bool {p : Char → Bool} {s : Slice} {pos : s.Pos} (h : pos < s.skipPrefixWhile p) :
-    p (pos.get (Pos.ne_endPos_of_lt h)) = true :=
-  Pos.apply_eq_true_of_lt_skipWhile_bool (Pos.startPos_le _) (skipPrefixWhile_eq_skipWhile_startPos ▸ h)
-
-@[simp]
-theorem all_bool_eq {p : Char → Bool} {s : Slice} : s.all p = s.copy.toList.all p := by
-  rw [Bool.eq_iff_iff, Pattern.Model.all_eq_true_iff,
-    CharPred.isLongestMatchAtChain_startPos_endPos_iff_toList, List.all_eq_true]
-
-@[simp]
-theorem Pos.skip?_prop_eq_some_iff {P : Char → Prop} [DecidablePred P] {s : Slice} {pos res : s.Pos} :
-    pos.skip? P = some res ↔ ∃ h, res = pos.next h ∧ P (pos.get h) := by
-  simp [Pos.skip?_prop_eq_skip?_decide, skip?_bool_eq_some_iff]
-
-@[simp]
-theorem Pos.skip?_prop_eq_none_iff {P : Char → Prop} [DecidablePred P] {s : Slice} {pos : s.Pos} :
-    pos.skip? P = none ↔ ∀ h, ¬ P (pos.get h) := by
-  simp [Pos.skip?_prop_eq_skip?_decide, skip?_bool_eq_none_iff]
-
-theorem Pos.apply_skipWhile_prop {P : Char → Prop} [DecidablePred P] {s : Slice} {pos : s.Pos} {h} :
-    ¬ P ((pos.skipWhile P).get h) := by
-  have := Pattern.Model.Pos.not_matchesAt_skipWhile P pos
-  simp_all [CharPred.Decidable.matchesAt_iff]
-
-theorem Pos.skipWhile_prop_eq_self_iff_get {P : Char → Prop} [DecidablePred P] {s : Slice} {pos : s.Pos} :
-    pos.skipWhile P = pos ↔ ∀ h, ¬ P (pos.get h) := by
-  simp [Pos.skipWhile_prop_eq_skipWhile_decide, skipWhile_bool_eq_self_iff_get]
-
-theorem Pos.apply_of_lt_skipWhile_prop {P : Char → Prop} [DecidablePred P] {s : Slice} {pos pos' : s.Pos}
-    (h₁ : pos ≤ pos') (h₂ : pos' < pos.skipWhile P) : P (pos'.get (ne_endPos_of_lt h₂)) := by
-  simp [Pos.skipWhile_prop_eq_skipWhile_decide] at h₂
-  simpa using apply_eq_true_of_lt_skipWhile_bool h₁ h₂
-
-theorem apply_skipPrefixWhile_prop {P : Char → Prop} [DecidablePred P] {s : Slice} {h} :
-    ¬ P ((s.skipPrefixWhile P).get h) := by
-  simp [skipPrefixWhile_eq_skipWhile_startPos, Pos.apply_skipWhile_prop]
-
-theorem apply_of_lt_skipPrefixWhile_prop {P : Char → Prop} [DecidablePred P] {s : Slice} {pos : s.Pos}
-    (h : pos < s.skipPrefixWhile P) : P (pos.get (Pos.ne_endPos_of_lt h)) := by
-  simp [skipPrefixWhile_prop_eq_skipPrefixWhile_decide] at h
-  simpa using apply_eq_true_of_lt_skipPrefixWhile_bool h
-
-@[simp]
-theorem all_prop_eq {P : Char → Prop} [DecidablePred P] {s : Slice} :
-    s.all P = s.copy.toList.all (decide <| P ·) := by
-  simp [all_prop_eq_all_decide]
-
 theorem skipPrefix?_prop_eq_some_iff {P : Char → Prop} [DecidablePred P] {s : Slice} {pos : s.Pos} :
     s.skipPrefix? P = some pos ↔ ∃ h, pos = s.startPos.next h ∧ P (s.startPos.get h) := by
   simp [skipPrefix?_prop_eq_skipPrefix?_decide, skipPrefix?_bool_eq_some_iff]
@@ -144,136 +64,11 @@ theorem startsWith_prop_eq_head? {P : Char → Prop} [DecidablePred P] {s : Slic
     s.startsWith P = s.copy.toList.head?.any (decide <| P ·) := by
   simp [startsWith_prop_eq_startsWith_decide, startsWith_bool_eq_head?]
 
-theorem eq_append_of_dropPrefix?_prop_eq_some {P : Char → Prop} [DecidablePred P] {s res : Slice} (h : s.dropPrefix? P = some res) :
+theorem eq_append_of_dropPrefix_prop_eq_some {P : Char → Prop} [DecidablePred P] {s res : Slice} (h : s.dropPrefix? P = some res) :
     ∃ c, s.copy = singleton c ++ res.copy ∧ P c := by
   rw [dropPrefix?_prop_eq_dropPrefix?_decide] at h
   simpa using eq_append_of_dropPrefix?_bool_eq_some h
 
-theorem skipSuffix?_bool_eq_some_iff {p : Char → Bool} {s : Slice} {pos : s.Pos} :
-    s.skipSuffix? p = some pos ↔ ∃ h, pos = s.endPos.prev h ∧ p ((s.endPos.prev h).get (by simp)) = true := by
-  rw [Pattern.Model.skipSuffix?_eq_some_iff, CharPred.isLongestRevMatch_iff]
-
-theorem endsWith_bool_iff_get {p : Char → Bool} {s : Slice} :
-    s.endsWith p ↔ ∃ h, p ((s.endPos.prev h).get (by simp)) = true := by
-  simp [Pattern.Model.endsWith_iff, CharPred.revMatchesAt_iff]
-
-theorem endsWith_bool_eq_false_iff_get {p : Char → Bool} {s : Slice} :
-    s.endsWith p = false ↔ ∀ h, p ((s.endPos.prev h).get (by simp)) = false := by
-  simp [Pattern.Model.endsWith_eq_false_iff, CharPred.revMatchesAt_iff]
-
-theorem endsWith_bool_eq_getLast? {p : Char → Bool} {s : Slice} :
-    s.endsWith p = s.copy.toList.getLast?.any p := by
-  rw [Bool.eq_iff_iff, Pattern.Model.endsWith_iff, CharPred.revMatchesAt_iff]
-  by_cases h : s.endPos = s.startPos
-  · refine ⟨fun ⟨h', _⟩ => by simp_all, ?_⟩
-    have : s.copy = "" := by simp_all [Slice.startPos_eq_endPos_iff.mp h.symm]
-    simp [this]
-  · obtain ⟨t, ht⟩ := s.splits_endPos.exists_eq_append_singleton_of_ne_startPos h
-    simp [h, ht]
-
-theorem eq_append_of_dropSuffix?_bool_eq_some {p : Char → Bool} {s res : Slice} (h : s.dropSuffix? p = some res) :
-    ∃ c, s.copy = res.copy ++ singleton c ∧ p c = true := by
-  obtain ⟨_, ⟨c, ⟨rfl, h₁⟩⟩, h₂⟩ := by simpa [PatternModel.Matches] using Pattern.Model.eq_append_of_dropSuffix?_eq_some h
-  exact ⟨_, h₂, h₁⟩
-
-theorem skipSuffix?_prop_eq_some_iff {P : Char → Prop} [DecidablePred P] {s : Slice} {pos : s.Pos} :
-    s.skipSuffix? P = some pos ↔ ∃ h, pos = s.endPos.prev h ∧ P ((s.endPos.prev h).get (by simp)) := by
-  simp [skipSuffix?_prop_eq_skipSuffix?_decide, skipSuffix?_bool_eq_some_iff]
-
-theorem endsWith_prop_iff_get {P : Char → Prop} [DecidablePred P] {s : Slice} :
-    s.endsWith P ↔ ∃ h, P ((s.endPos.prev h).get (by simp)) := by
-  simp [endsWith_prop_eq_endsWith_decide, endsWith_bool_iff_get]
-
-theorem endsWith_prop_eq_false_iff_get {P : Char → Prop} [DecidablePred P] {s : Slice} :
-    s.endsWith P = false ↔ ∀ h, ¬ P ((s.endPos.prev h).get (by simp)) := by
-  simp [endsWith_prop_eq_endsWith_decide, endsWith_bool_eq_false_iff_get]
-
-theorem endsWith_prop_eq_getLast? {P : Char → Prop} [DecidablePred P] {s : Slice} :
-    s.endsWith P = s.copy.toList.getLast?.any (decide <| P ·) := by
-  simp [endsWith_prop_eq_endsWith_decide, endsWith_bool_eq_getLast?]
-
-theorem eq_append_of_dropSuffix?_prop_eq_some {P : Char → Prop} [DecidablePred P] {s res : Slice} (h : s.dropSuffix? P = some res) :
-    ∃ c, s.copy = res.copy ++ singleton c ∧ P c := by
-  rw [dropSuffix?_prop_eq_dropSuffix?_decide] at h
-  simpa using eq_append_of_dropSuffix?_bool_eq_some h
-
-@[simp]
-theorem Pos.revSkip?_bool_eq_some_iff {p : Char → Bool} {s : Slice} {pos res : s.Pos} :
-    pos.revSkip? p = some res ↔ ∃ h, res = pos.prev h ∧ p ((pos.prev h).get (by simp)) := by
-  simp [Pattern.Model.Pos.revSkip?_eq_some_iff, CharPred.isLongestRevMatchAt_iff]
-
-@[simp]
-theorem Pos.revSkip?_bool_eq_none_iff {p : Char → Bool} {s : Slice} {pos : s.Pos} :
-    pos.revSkip? p = none ↔ ∀ h, p ((pos.prev h).get (by simp)) = false := by
-  simp [Pattern.Model.Pos.revSkip?_eq_none_iff, CharPred.revMatchesAt_iff]
-
-theorem Pos.apply_revSkipWhile_bool_eq_false {p : Char → Bool} {s : Slice} {pos : s.Pos} {h} :
-    p (((pos.revSkipWhile p).prev h).get (by simp)) = false := by
-  have := Pattern.Model.Pos.not_revMatchesAt_revSkipWhile p pos
-  simp_all [CharPred.revMatchesAt_iff]
-
-theorem Pos.revSkipWhile_bool_eq_self_iff_get {p : Char → Bool} {s : Slice} {pos : s.Pos} :
-    pos.revSkipWhile p = pos ↔ ∀ h, p ((pos.prev h).get (by simp)) = false := by
-  simp [Pattern.Model.Pos.revSkipWhile_eq_self_iff, CharPred.revMatchesAt_iff]
-
-theorem Pos.apply_eq_true_of_revSkipWhile_le_bool {p : Char → Bool} {s : Slice} {pos pos' : s.Pos}
-    (h₁ : pos' < pos) (h₂ : pos.revSkipWhile p ≤ pos') : p (pos'.get (Pos.ne_endPos_of_lt h₁)) = true :=
-  (CharPred.isLongestRevMatchAtChain_iff.1 (Pattern.Model.Pos.isLongestRevMatchAtChain_revSkipWhile p pos)).2 _ h₂ h₁
-
-theorem apply_skipSuffixWhile_bool_eq_false {p : Char → Bool} {s : Slice} {h} :
-    p (((s.skipSuffixWhile p).prev h).get (by simp)) = false := by
-  simp [skipSuffixWhile_eq_revSkipWhile_endPos, Pos.apply_revSkipWhile_bool_eq_false]
-
-theorem apply_eq_true_of_skipSuffixWhile_le_bool {p : Char → Bool} {s : Slice} {pos : s.Pos}
-    (h : s.skipSuffixWhile p ≤ pos) (h' : pos < s.endPos) :
-    p (pos.get (Pos.ne_endPos_of_lt h')) = true :=
-  Pos.apply_eq_true_of_revSkipWhile_le_bool h' (skipSuffixWhile_eq_revSkipWhile_endPos ▸ h)
-
-@[simp]
-theorem revAll_bool_eq {p : Char → Bool} {s : Slice} : s.revAll p = s.copy.toList.all p := by
-  rw [Bool.eq_iff_iff, Pattern.Model.revAll_eq_true_iff,
-    CharPred.isLongestRevMatchAtChain_startPos_endPos_iff_toList, List.all_eq_true]
-
-@[simp]
-theorem Pos.revSkip?_prop_eq_some_iff {P : Char → Prop} [DecidablePred P] {s : Slice} {pos res : s.Pos} :
-    pos.revSkip? P = some res ↔ ∃ h, res = pos.prev h ∧ P ((pos.prev h).get (by simp)) := by
-  simp [Pos.revSkip?_prop_eq_revSkip?_decide, revSkip?_bool_eq_some_iff]
-
-@[simp]
-theorem Pos.revSkip?_prop_eq_none_iff {P : Char → Prop} [DecidablePred P] {s : Slice} {pos : s.Pos} :
-    pos.revSkip? P = none ↔ ∀ h, ¬ P ((pos.prev h).get (by simp)) := by
-  simp [Pos.revSkip?_prop_eq_revSkip?_decide, revSkip?_bool_eq_none_iff]
-
-theorem Pos.apply_revSkipWhile_prop {P : Char → Prop} [DecidablePred P] {s : Slice} {pos : s.Pos} {h} :
-    ¬ P (((pos.revSkipWhile P).prev h).get (by simp)) := by
-  have := Pattern.Model.Pos.not_revMatchesAt_revSkipWhile P pos
-  simp_all [CharPred.Decidable.revMatchesAt_iff]
-
-theorem Pos.revSkipWhile_prop_eq_self_iff_get {P : Char → Prop} [DecidablePred P] {s : Slice} {pos : s.Pos} :
-    pos.revSkipWhile P = pos ↔ ∀ h, ¬ P ((pos.prev h).get (by simp)) := by
-  simp [Pos.revSkipWhile_prop_eq_revSkipWhile_decide, revSkipWhile_bool_eq_self_iff_get]
-
-theorem Pos.apply_of_revSkipWhile_le_prop {P : Char → Prop} [DecidablePred P] {s : Slice} {pos pos' : s.Pos}
-    (h₁ : pos' < pos) (h₂ : pos.revSkipWhile P ≤ pos') : P (pos'.get (Pos.ne_endPos_of_lt h₁)) := by
-  have h₂' : pos.revSkipWhile (decide <| P ·) ≤ pos' :=
-    Pos.revSkipWhile_prop_eq_revSkipWhile_decide (p := P) pos ▸ h₂
-  simpa using Pos.apply_eq_true_of_revSkipWhile_le_bool h₁ h₂'
-
-theorem apply_skipSuffixWhile_prop {P : Char → Prop} [DecidablePred P] {s : Slice} {h} :
-    ¬ P (((s.skipSuffixWhile P).prev h).get (by simp)) := by
-  have := Pattern.Model.Pos.not_revMatchesAt_revSkipWhile P s.endPos
-  simp_all [CharPred.Decidable.revMatchesAt_iff, skipSuffixWhile_eq_revSkipWhile_endPos]
-
-theorem apply_of_skipSuffixWhile_le_prop {P : Char → Prop} [DecidablePred P] {s : Slice} {pos : s.Pos}
-    (h : s.skipSuffixWhile P ≤ pos) (h' : pos < s.endPos) :
-    P (pos.get (Pos.ne_endPos_of_lt h')) :=
-  Pos.apply_of_revSkipWhile_le_prop h' (skipSuffixWhile_eq_revSkipWhile_endPos (pat := P) ▸ h)
-
-@[simp]
-theorem revAll_prop_eq {P : Char → Prop} [DecidablePred P] {s : Slice} :
-    s.revAll P = s.copy.toList.all (decide <| P ·) := by
-  simp [revAll_prop_eq_revAll_decide, revAll_bool_eq]
-
 end Slice
 
 theorem skipPrefix?_bool_eq_some_iff {p : Char → Bool} {s : String} {pos : s.Pos} :
@@ -283,58 +78,21 @@ theorem skipPrefix?_bool_eq_some_iff {p : Char → Bool} {s : String} {pos : s.P
 
 theorem startsWith_bool_iff_get {p : Char → Bool} {s : String} :
     s.startsWith p ↔ ∃ h, p (s.startPos.get h) = true := by
-  simp [← startsWith_toSlice, Slice.startsWith_bool_iff_get]
+  simp [startsWith_eq_startsWith_toSlice, Slice.startsWith_bool_iff_get]
 
 theorem startsWith_bool_eq_false_iff_get {p : Char → Bool} {s : String} :
     s.startsWith p = false ↔ ∀ h, p (s.startPos.get h) = false := by
-  simp [← startsWith_toSlice, Slice.startsWith_bool_eq_false_iff_get]
+  simp [startsWith_eq_startsWith_toSlice, Slice.startsWith_bool_eq_false_iff_get]
 
 theorem startsWith_bool_eq_head? {p : Char → Bool} {s : String} :
     s.startsWith p = s.toList.head?.any p := by
-  simp [← startsWith_toSlice, Slice.startsWith_bool_eq_head?]
+  simp [startsWith_eq_startsWith_toSlice, Slice.startsWith_bool_eq_head?]
 
 theorem eq_append_of_dropPrefix?_bool_eq_some {p : Char → Bool} {s : String} {res : Slice} (h : s.dropPrefix? p = some res) :
     ∃ c, s = singleton c ++ res.copy ∧ p c = true := by
   rw [dropPrefix?_eq_dropPrefix?_toSlice] at h
   simpa using Slice.eq_append_of_dropPrefix?_bool_eq_some h
 
-@[simp]
-theorem Pos.skip?_bool_eq_some_iff {p : Char → Bool} {s : String} {pos res : s.Pos} :
-    pos.skip? p = some res ↔ ∃ h, res = pos.next h ∧ p (pos.get h) := by
-  simp [skip?_eq_skip?_toSlice, ← toSlice_inj, toSlice_next]
-
-@[simp]
-theorem Pos.skip?_bool_eq_none_iff {p : Char → Bool} {s : String} {pos : s.Pos} :
-    pos.skip? p = none ↔ ∀ h, p (pos.get h) = false := by
-  simp [skip?_eq_skip?_toSlice]
-
-theorem Pos.apply_skipWhile_bool_eq_false {p : Char → Bool} {s : String} {pos : s.Pos} {h} :
-    p ((pos.skipWhile p).get h) = false := by
-  simp [skipWhile_eq_skipWhile_toSlice, Slice.Pos.apply_skipWhile_bool_eq_false]
-
-theorem Pos.skipWhile_bool_eq_self_iff_get {p : Char → Bool} {s : String} {pos : s.Pos} :
-    pos.skipWhile p = pos ↔ ∀ h, p (pos.get h) = false := by
-  simp [skipWhile_eq_skipWhile_toSlice, ← toSlice_inj, Slice.Pos.skipWhile_bool_eq_self_iff_get]
-
-theorem Pos.apply_eq_true_of_lt_skipWhile_bool {p : Char → Bool} {s : String} {pos pos' : s.Pos}
-    (h₁ : pos ≤ pos') (h₂ : pos' < pos.skipWhile p) : p (pos'.get (ne_endPos_of_lt h₂)) = true := by
-  rw [Pos.get_eq_get_toSlice]
-  exact Slice.Pos.apply_eq_true_of_lt_skipWhile_bool (toSlice_le_toSlice_iff.2 h₁)
-    (by simpa [skipWhile_eq_skipWhile_toSlice] using h₂)
-
-theorem apply_skipPrefixWhile_bool_eq_false {p : Char → Bool} {s : String} {h} :
-    p ((s.skipPrefixWhile p).get h) = false := by
-  simp [skipPrefixWhile_eq_skipPrefixWhile_toSlice, Slice.apply_skipPrefixWhile_bool_eq_false]
-
-theorem apply_eq_true_of_lt_skipPrefixWhile_bool {p : Char → Bool} {s : String} {pos : s.Pos} (h : pos < s.skipPrefixWhile p) :
-    p (pos.get (Pos.ne_endPos_of_lt h)) = true := by
-  rw [Pos.get_eq_get_toSlice]
-  exact Slice.apply_eq_true_of_lt_skipPrefixWhile_bool (by simpa [skipPrefixWhile_eq_skipPrefixWhile_toSlice] using h)
-
-@[simp]
-theorem all_bool_eq {p : Char → Bool} {s : String} : s.all p = s.toList.all p := by
-  simp [← all_toSlice]
-
 theorem skipPrefix?_prop_eq_some_iff {P : Char → Prop} [DecidablePred P] {s : String} {pos : s.Pos} :
     s.skipPrefix? P = some pos ↔ ∃ h, pos = s.startPos.next h ∧ P (s.startPos.get h) := by
   simp [skipPrefix?_eq_skipPrefix?_toSlice, Slice.skipPrefix?_prop_eq_some_iff, ← Pos.toSlice_inj,
@@ -342,198 +100,19 @@ theorem skipPrefix?_prop_eq_some_iff {P : Char → Prop} [DecidablePred P] {s :
 
 theorem startsWith_prop_iff_get {P : Char → Prop} [DecidablePred P] {s : String} :
     s.startsWith P ↔ ∃ h, P (s.startPos.get h) := by
-  simp [← startsWith_toSlice, Slice.startsWith_prop_iff_get]
+  simp [startsWith_eq_startsWith_toSlice, Slice.startsWith_prop_iff_get]
 
 theorem startsWith_prop_eq_false_iff_get {P : Char → Prop} [DecidablePred P] {s : String} :
     s.startsWith P = false ↔ ∀ h, ¬ P (s.startPos.get h) := by
-  simp [← startsWith_toSlice, Slice.startsWith_prop_eq_false_iff_get]
+  simp [startsWith_eq_startsWith_toSlice, Slice.startsWith_prop_eq_false_iff_get]
 
 theorem startsWith_prop_eq_head? {P : Char → Prop} [DecidablePred P] {s : String} :
     s.startsWith P = s.toList.head?.any (decide <| P ·) := by
-  simp [← startsWith_toSlice, Slice.startsWith_prop_eq_head?]
+  simp [startsWith_eq_startsWith_toSlice, Slice.startsWith_prop_eq_head?]
 
 theorem eq_append_of_dropPrefix?_prop_eq_some {P : Char → Prop} [DecidablePred P] {s : String} {res : Slice}
     (h : s.dropPrefix? P = some res) : ∃ c, s = singleton c ++ res.copy ∧ P c := by
   rw [dropPrefix?_eq_dropPrefix?_toSlice] at h
-  simpa using Slice.eq_append_of_dropPrefix?_prop_eq_some h
-
-theorem skipSuffix?_bool_eq_some_iff {p : Char → Bool} {s : String} {pos : s.Pos} :
-    s.skipSuffix? p = some pos ↔ ∃ h, pos = s.endPos.prev h ∧ p ((s.endPos.prev h).get (by simp)) = true := by
-  simp [skipSuffix?_eq_skipSuffix?_toSlice, Slice.skipSuffix?_bool_eq_some_iff, ← Pos.toSlice_inj,
-    Pos.prev_toSlice]
-
-theorem endsWith_bool_iff_get {p : Char → Bool} {s : String} :
-    s.endsWith p ↔ ∃ h, p ((s.endPos.prev h).get (by simp)) = true := by
-  simp [← endsWith_toSlice, Slice.endsWith_bool_iff_get, Pos.prev_toSlice]
-
-theorem endsWith_bool_eq_false_iff_get {p : Char → Bool} {s : String} :
-    s.endsWith p = false ↔ ∀ h, p ((s.endPos.prev h).get (by simp)) = false := by
-  simp [← endsWith_toSlice, Slice.endsWith_bool_eq_false_iff_get, Pos.prev_toSlice]
-
-theorem endsWith_bool_eq_getLast? {p : Char → Bool} {s : String} :
-    s.endsWith p = s.toList.getLast?.any p := by
-  simp [← endsWith_toSlice, Slice.endsWith_bool_eq_getLast?]
-
-theorem eq_append_of_dropSuffix?_bool_eq_some {p : Char → Bool} {s : String} {res : Slice} (h : s.dropSuffix? p = some res) :
-    ∃ c, s = res.copy ++ singleton c ∧ p c = true := by
-  rw [dropSuffix?_eq_dropSuffix?_toSlice] at h
-  simpa using Slice.eq_append_of_dropSuffix?_bool_eq_some h
-
-theorem skipSuffix?_prop_eq_some_iff {P : Char → Prop} [DecidablePred P] {s : String} {pos : s.Pos} :
-    s.skipSuffix? P = some pos ↔ ∃ h, pos = s.endPos.prev h ∧ P ((s.endPos.prev h).get (by simp)) := by
-  simp [skipSuffix?_eq_skipSuffix?_toSlice, Slice.skipSuffix?_prop_eq_some_iff, ← Pos.toSlice_inj,
-    Pos.prev_toSlice]
-
-theorem endsWith_prop_iff_get {P : Char → Prop} [DecidablePred P] {s : String} :
-    s.endsWith P ↔ ∃ h, P ((s.endPos.prev h).get (by simp)) := by
-  simp [← endsWith_toSlice, Slice.endsWith_prop_iff_get, Pos.prev_toSlice]
-
-theorem endsWith_prop_eq_false_iff_get {P : Char → Prop} [DecidablePred P] {s : String} :
-    s.endsWith P = false ↔ ∀ h, ¬ P ((s.endPos.prev h).get (by simp)) := by
-  simp [← endsWith_toSlice, Slice.endsWith_prop_eq_false_iff_get, Pos.prev_toSlice]
-
-theorem endsWith_prop_eq_getLast? {P : Char → Prop} [DecidablePred P] {s : String} :
-    s.endsWith P = s.toList.getLast?.any (decide <| P ·) := by
-  simp [← endsWith_toSlice, Slice.endsWith_prop_eq_getLast?]
-
-theorem eq_append_of_dropSuffix?_prop_eq_some {P : Char → Prop} [DecidablePred P] {s : String} {res : Slice}
-    (h : s.dropSuffix? P = some res) : ∃ c, s = res.copy ++ singleton c ∧ P c := by
-  rw [dropSuffix?_eq_dropSuffix?_toSlice] at h
-  simpa using Slice.eq_append_of_dropSuffix?_prop_eq_some h
-
-@[simp]
-theorem Pos.skip?_prop_eq_some_iff {P : Char → Prop} [DecidablePred P] {s : String} {pos res : s.Pos} :
-    pos.skip? P = some res ↔ ∃ h, res = pos.next h ∧ P (pos.get h) := by
-  simp [skip?_eq_skip?_toSlice, ← toSlice_inj, toSlice_next]
-
-@[simp]
-theorem Pos.skip?_prop_eq_none_iff {P : Char → Prop} [DecidablePred P] {s : String} {pos : s.Pos} :
-    pos.skip? P = none ↔ ∀ h, ¬ P (pos.get h) := by
-  simp [skip?_eq_skip?_toSlice]
-
-theorem Pos.apply_skipWhile_prop {P : Char → Prop} [DecidablePred P] {s : String} {pos : s.Pos} {h} :
-    ¬ P ((pos.skipWhile P).get h) := by
-  simp [skipWhile_eq_skipWhile_toSlice, Slice.Pos.apply_skipWhile_prop]
-
-theorem Pos.skipWhile_prop_eq_self_iff_get {P : Char → Prop} [DecidablePred P] {s : String} {pos : s.Pos} :
-    pos.skipWhile P = pos ↔ ∀ h, ¬ P (pos.get h) := by
-  simp [skipWhile_eq_skipWhile_toSlice, ← toSlice_inj, Slice.Pos.skipWhile_prop_eq_self_iff_get]
-
-theorem Pos.apply_of_lt_skipWhile_prop {P : Char → Prop} [DecidablePred P] {s : String} {pos pos' : s.Pos}
-    (h₁ : pos ≤ pos') (h₂ : pos' < pos.skipWhile P) : P (pos'.get (ne_endPos_of_lt h₂)) := by
-  rw [Pos.get_eq_get_toSlice]
-  exact Slice.Pos.apply_of_lt_skipWhile_prop (toSlice_le_toSlice_iff.2 h₁)
-    (by simpa [skipWhile_eq_skipWhile_toSlice] using h₂)
-
-theorem apply_skipPrefixWhile_prop {P : Char → Prop} [DecidablePred P] {s : String} {h} :
-    ¬ P ((s.skipPrefixWhile P).get h) := by
-  simp [skipPrefixWhile_eq_skipPrefixWhile_toSlice, Slice.apply_skipPrefixWhile_prop]
-
-theorem apply_of_lt_skipPrefixWhile_prop {P : Char → Prop} [DecidablePred P] {s : String} {pos : s.Pos}
-    (h : pos < s.skipPrefixWhile P) : P (pos.get (Pos.ne_endPos_of_lt h)) := by
-  rw [Pos.get_eq_get_toSlice]
-  exact Slice.apply_of_lt_skipPrefixWhile_prop (by simpa [skipPrefixWhile_eq_skipPrefixWhile_toSlice] using h)
-
-@[simp]
-theorem all_prop_eq {P : Char → Prop} [DecidablePred P] {s : String} :
-    s.all P = s.toList.all (decide <| P ·) := by
-  simp [← all_toSlice]
-
-@[simp]
-theorem Pos.revSkip?_bool_eq_some_iff {p : Char → Bool} {s : String} {pos res : s.Pos} :
-    pos.revSkip? p = some res ↔ ∃ h, res = pos.prev h ∧ p ((pos.prev h).get (by simp)) := by
-  simp [revSkip?_eq_revSkip?_toSlice, ← toSlice_inj, toSlice_prev, get_eq_get_toSlice]
-
-@[simp]
-theorem Pos.revSkip?_bool_eq_none_iff {p : Char → Bool} {s : String} {pos : s.Pos} :
-    pos.revSkip? p = none ↔ ∀ h, p ((pos.prev h).get (by simp)) = false := by
-  simp [revSkip?_eq_revSkip?_toSlice, Pos.prev_toSlice]
-
-theorem Pos.apply_revSkipWhile_bool_eq_false {p : Char → Bool} {s : String} {pos : s.Pos} {h} :
-    p (((pos.revSkipWhile p).prev h).get (by simp)) = false := by
-  have h' : pos.toSlice.revSkipWhile p ≠ s.toSlice.startPos := by
-    simpa [Pos.revSkipWhile_eq_revSkipWhile_toSlice, ← toSlice_inj] using h
-  have := Slice.Pos.apply_revSkipWhile_bool_eq_false (pos := pos.toSlice) (h := h')
-  simpa [Pos.revSkipWhile_eq_revSkipWhile_toSlice, Pos.prev_ofToSlice]
-
-theorem Pos.revSkipWhile_bool_eq_self_iff_get {p : Char → Bool} {s : String} {pos : s.Pos} :
-    pos.revSkipWhile p = pos ↔ ∀ h, p ((pos.prev h).get (by simp)) = false := by
-  simp [Pos.revSkipWhile_eq_revSkipWhile_toSlice, ← toSlice_inj, Slice.Pos.revSkipWhile_bool_eq_self_iff_get,
-    Pos.prev_toSlice]
-
-theorem Pos.apply_eq_true_of_revSkipWhile_le_bool {p : Char → Bool} {s : String} {pos pos' : s.Pos}
-    (h₁ : pos' < pos) (h₂ : pos.revSkipWhile p ≤ pos') : p (pos'.get (ne_endPos_of_lt h₁)) = true := by
-  rw [Pos.get_eq_get_toSlice]
-  exact Slice.Pos.apply_eq_true_of_revSkipWhile_le_bool
-    (Pos.toSlice_lt_toSlice_iff.2 h₁)
-    (by simpa [Pos.revSkipWhile_eq_revSkipWhile_toSlice, Pos.ofToSlice_le_iff] using h₂)
-
-theorem apply_skipSuffixWhile_bool_eq_false {p : Char → Bool} {s : String} {h} :
-    p (((s.skipSuffixWhile p).prev h).get (by simp)) = false := by
-  have h' : s.toSlice.skipSuffixWhile p ≠ s.toSlice.startPos := by
-    simpa [skipSuffixWhile_eq_skipSuffixWhile_toSlice, ← Pos.toSlice_inj] using h
-  have := Slice.apply_skipSuffixWhile_bool_eq_false (s := s.toSlice) (h := h')
-  simpa [skipSuffixWhile_eq_skipSuffixWhile_toSlice, Pos.prev_ofToSlice]
-
-theorem apply_eq_true_of_skipSuffixWhile_le_bool {p : Char → Bool} {s : String} {pos : s.Pos}
-    (h : s.skipSuffixWhile p ≤ pos) (h' : pos < s.endPos) :
-    p (pos.get (Pos.ne_endPos_of_lt h')) = true := by
-  rw [Pos.get_eq_get_toSlice]
-  exact Slice.apply_eq_true_of_skipSuffixWhile_le_bool
-    (by simpa [skipSuffixWhile_eq_skipSuffixWhile_toSlice, Pos.ofToSlice_le_iff] using h)
-    (by simpa [Pos.toSlice_lt_toSlice_iff] using h')
-
-@[simp]
-theorem revAll_bool_eq {p : Char → Bool} {s : String} : s.revAll p = s.toList.all p := by
-  simp [← revAll_toSlice]
-
-@[simp]
-theorem Pos.revSkip?_prop_eq_some_iff {P : Char → Prop} [DecidablePred P] {s : String} {pos res : s.Pos} :
-    pos.revSkip? P = some res ↔ ∃ h, res = pos.prev h ∧ P ((pos.prev h).get (by simp)) := by
-  simp [revSkip?_eq_revSkip?_toSlice, ← toSlice_inj, toSlice_prev, get_eq_get_toSlice]
-
-@[simp]
-theorem Pos.revSkip?_prop_eq_none_iff {P : Char → Prop} [DecidablePred P] {s : String} {pos : s.Pos} :
-    pos.revSkip? P = none ↔ ∀ h, ¬ P ((pos.prev h).get (by simp)) := by
-  simp [revSkip?_eq_revSkip?_toSlice, Pos.prev_toSlice]
-
-theorem Pos.apply_revSkipWhile_prop {P : Char → Prop} [DecidablePred P] {s : String} {pos : s.Pos} {h} :
-    ¬ P (((pos.revSkipWhile P).prev h).get (by simp)) := by
-  have h' : pos.toSlice.revSkipWhile P ≠ s.toSlice.startPos := by
-    simpa [Pos.revSkipWhile_eq_revSkipWhile_toSlice, ← toSlice_inj] using h
-  have := Slice.Pos.apply_revSkipWhile_prop (pos := pos.toSlice) (h := h')
-  simpa [Pos.revSkipWhile_eq_revSkipWhile_toSlice, Pos.prev_ofToSlice]
-
-theorem Pos.revSkipWhile_prop_eq_self_iff_get {P : Char → Prop} [DecidablePred P] {s : String} {pos : s.Pos} :
-    pos.revSkipWhile P = pos ↔ ∀ h, ¬ P ((pos.prev h).get (by simp)) := by
-  simp [Pos.revSkipWhile_eq_revSkipWhile_toSlice, ← toSlice_inj,
-    Slice.Pos.revSkipWhile_prop_eq_self_iff_get, Pos.prev_toSlice]
-
-theorem Pos.apply_of_revSkipWhile_le_prop {P : Char → Prop} [DecidablePred P] {s : String} {pos pos' : s.Pos}
-    (h₁ : pos' < pos) (h₂ : pos.revSkipWhile P ≤ pos') : P (pos'.get (ne_endPos_of_lt h₁)) := by
-  rw [Pos.get_eq_get_toSlice]
-  exact Slice.Pos.apply_of_revSkipWhile_le_prop
-    (Pos.toSlice_lt_toSlice_iff.2 h₁)
-    (by simpa [Pos.revSkipWhile_eq_revSkipWhile_toSlice, Pos.ofToSlice_le_iff] using h₂)
-
-theorem apply_skipSuffixWhile_prop {P : Char → Prop} [DecidablePred P] {s : String} {h} :
-    ¬ P (((s.skipSuffixWhile P).prev h).get (by simp)) := by
-  have h' : s.toSlice.skipSuffixWhile P ≠ s.toSlice.startPos := by
-    simpa [skipSuffixWhile_eq_skipSuffixWhile_toSlice, ← Pos.toSlice_inj] using h
-  have := Slice.apply_skipSuffixWhile_prop (s := s.toSlice) (h := h')
-  simpa [skipSuffixWhile_eq_skipSuffixWhile_toSlice, Pos.prev_ofToSlice]
-
-theorem apply_of_skipSuffixWhile_le_prop {P : Char → Prop} [DecidablePred P] {s : String} {pos : s.Pos}
-    (h : s.skipSuffixWhile P ≤ pos) (h' : pos < s.endPos) :
-    P (pos.get (Pos.ne_endPos_of_lt h')) := by
-  rw [Pos.get_eq_get_toSlice]
-  exact Slice.apply_of_skipSuffixWhile_le_prop
-    (by simpa [skipSuffixWhile_eq_skipSuffixWhile_toSlice, Pos.ofToSlice_le_iff] using h)
-    (by simpa [Pos.toSlice_lt_toSlice_iff] using h')
-
-@[simp]
-theorem revAll_prop_eq {P : Char → Prop} [DecidablePred P] {s : String} :
-    s.revAll P = s.toList.all (decide <| P ·) := by
-  simp [← revAll_toSlice]
+  simpa using Slice.eq_append_of_dropPrefix_prop_eq_some h
 
 end String

src/Init/Data/String/Lemmas/Pattern/TakeDrop/String.lean

@@ -30,7 +30,11 @@ theorem skipPrefix?_slice_of_isEmpty {pat s : Slice} (hpat : pat.isEmpty = true)
 @[simp]
 theorem skipPrefix?_slice_eq_some_iff {pat s : Slice} {pos : s.Pos} :
     s.skipPrefix? pat = some pos ↔ ∃ t, pos.Splits pat.copy t := by
-  rw [Pattern.Model.skipPrefix?_eq_some_iff, ForwardSliceSearcher.isLongestMatch_iff_splits]
+  match h : pat.isEmpty with
+  | false =>
+    have := ForwardSliceSearcher.lawfulForwardPatternModel h
+    rw [Pattern.Model.skipPrefix?_eq_some_iff, ForwardSliceSearcher.isLongestMatch_iff_splits h]
+  | true => simp [skipPrefix?_slice_of_isEmpty h, (show pat.copy = "" by simpa), eq_comm]
 
 theorem startsWith_slice_of_isEmpty {pat s : Slice} (hpat : pat.isEmpty = true) :
     s.startsWith pat = true := by
@@ -39,10 +43,14 @@ theorem startsWith_slice_of_isEmpty {pat s : Slice} (hpat : pat.isEmpty = true)
 @[simp]
 theorem startsWith_slice_iff {pat s : Slice} :
     s.startsWith pat ↔ pat.copy.toList <+: s.copy.toList := by
-  simp only [Model.startsWith_iff, ForwardSliceSearcher.matchesAt_iff_splits,
-    splits_startPos_iff, exists_and_left, exists_eq_left]
-  simp only [← toList_inj, toList_append, List.prefix_iff_exists_append_eq]
-  exact ⟨fun ⟨t, ht⟩ => ⟨t.toList, by simp [ht]⟩, fun ⟨t, ht⟩ => ⟨String.ofList t, by simp [← ht]⟩⟩
+  match h : pat.isEmpty with
+  | false =>
+    have := ForwardSliceSearcher.lawfulForwardPatternModel h
+    simp only [Model.startsWith_iff, ForwardSliceSearcher.matchesAt_iff_splits h,
+      splits_startPos_iff, exists_and_left, exists_eq_left]
+    simp only [← toList_inj, toList_append, List.prefix_iff_exists_append_eq]
+    exact ⟨fun ⟨t, ht⟩ => ⟨t.toList, by simp [ht]⟩, fun ⟨t, ht⟩ => ⟨String.ofList t, by simp [← ht]⟩⟩
+  | true => simp [startsWith_slice_of_isEmpty h, (show pat.copy = "" by simpa)]
 
 @[simp]
 theorem startsWith_slice_eq_false_iff {pat s : Slice} :
@@ -55,18 +63,14 @@ theorem dropPrefix?_slice_of_isEmpty {pat s : Slice} (hpat : pat.isEmpty = true)
 
 theorem eq_append_of_dropPrefix?_slice_eq_some {pat s res : Slice} (h : s.dropPrefix? pat = some res) :
     s.copy = pat.copy ++ res.copy := by
-  have := Pattern.Model.eq_append_of_dropPrefix?_eq_some h
-  simp only [PatternModel.Matches] at this
-  obtain ⟨_, ⟨-, rfl⟩, h⟩ := this
-  exact h
-
-@[simp]
-theorem all_slice_iff {pat s : Slice} : s.all pat ↔ ∃ n, s.copy = String.join (List.replicate n pat.copy) := by
-  simp [Pattern.Model.all_eq_true_iff, ForwardSliceSearcher.isLongestMatchAtChain_startPos_endPos_iff]
-
-@[simp]
-theorem revAll_slice_iff {pat s : Slice} : s.revAll pat ↔ ∃ n, s.copy = String.join (List.replicate n pat.copy) := by
-  simp [Pattern.Model.revAll_eq_true_iff, ForwardSliceSearcher.isLongestRevMatchAtChain_startPos_endPos_iff]
+  match hpat : pat.isEmpty with
+  | false =>
+    have := ForwardSliceSearcher.lawfulForwardPatternModel hpat
+    have := Pattern.Model.eq_append_of_dropPrefix?_eq_some h
+    simp only [ForwardPatternModel.Matches] at this
+    obtain ⟨_, ⟨-, rfl⟩, h⟩ := this
+    exact h
+  | true => simp [Option.some.inj (h ▸ dropPrefix?_slice_of_isEmpty hpat), (show pat.copy = "" by simpa)]
 
 @[simp]
 theorem skipPrefix?_string_eq_some_iff {pat : String} {s : Slice} {pos : s.Pos} :
@@ -100,76 +104,6 @@ theorem eq_append_of_dropPrefix?_string_eq_some {pat : String} {s res : Slice} (
   rw [dropPrefix?_string_eq_dropPrefix?_toSlice] at h
   simpa using eq_append_of_dropPrefix?_slice_eq_some h
 
-
-theorem skipSuffix?_slice_of_isEmpty {pat s : Slice} (hpat : pat.isEmpty = true) :
-    s.skipSuffix? pat = some s.endPos := by
-  rw [skipSuffix?_eq_backwardPatternSkipSuffix?, BackwardSliceSearcher.skipSuffix?_of_isEmpty hpat]
-
-@[simp]
-theorem skipSuffix?_slice_eq_some_iff {pat s : Slice} {pos : s.Pos} :
-    s.skipSuffix? pat = some pos ↔ ∃ t, pos.Splits t pat.copy := by
-  rw [Pattern.Model.skipSuffix?_eq_some_iff, ForwardSliceSearcher.isLongestRevMatch_iff_splits]
-
-theorem endsWith_slice_of_isEmpty {pat s : Slice} (hpat : pat.isEmpty = true) :
-    s.endsWith pat = true := by
-  rw [endsWith_eq_backwardPatternEndsWith, BackwardSliceSearcher.endsWith_of_isEmpty hpat]
-
-@[simp]
-theorem endsWith_slice_iff {pat s : Slice} :
-    s.endsWith pat ↔ pat.copy.toList <:+ s.copy.toList := by
-  simp only [Model.endsWith_iff, ForwardSliceSearcher.revMatchesAt_iff_splits,
-    splits_endPos_iff, exists_eq_right]
-  simp only [← toList_inj, toList_append, List.suffix_iff_exists_append_eq]
-  exact ⟨fun ⟨t, ht⟩ => ⟨t.toList, by simp [ht]⟩, fun ⟨t, ht⟩ => ⟨String.ofList t, by simp [← ht]⟩⟩
-
-@[simp]
-theorem endsWith_slice_eq_false_iff {pat s : Slice} :
-    s.endsWith pat = false ↔ ¬ (pat.copy.toList <:+ s.copy.toList) := by
-  simp [← Bool.not_eq_true, endsWith_slice_iff]
-
-theorem dropSuffix?_slice_of_isEmpty {pat s : Slice} (hpat : pat.isEmpty = true) :
-    s.dropSuffix? pat = some s := by
-  simp [dropSuffix?_eq_map_skipSuffix?, skipSuffix?_slice_of_isEmpty hpat]
-
-theorem eq_append_of_dropSuffix?_slice_eq_some {pat s res : Slice} (h : s.dropSuffix? pat = some res) :
-    s.copy = res.copy ++ pat.copy := by
-  have := Pattern.Model.eq_append_of_dropSuffix?_eq_some h
-  simp only [PatternModel.Matches] at this
-  obtain ⟨_, ⟨-, rfl⟩, h⟩ := this
-  exact h
-
-@[simp]
-theorem skipSuffix?_string_eq_some_iff' {pat : String} {s : Slice} {pos : s.Pos} :
-    s.skipSuffix? pat = some pos ↔ ∃ t, pos.Splits t pat := by
-  simp [skipSuffix?_string_eq_skipSuffix?_toSlice]
-
-@[simp]
-theorem skipSuffix?_string_empty {s : Slice} : s.skipSuffix? "" = some s.endPos := by
-  simp
-
-@[simp]
-theorem endsWith_string_iff {pat : String} {s : Slice} :
-    s.endsWith pat ↔ pat.toList <:+ s.copy.toList := by
-  simp [endsWith_string_eq_endsWith_toSlice]
-
-@[simp]
-theorem endsWith_string_empty {s : Slice} : s.endsWith "" = true := by
-  simp
-
-@[simp]
-theorem endsWith_string_eq_false_iff {pat : String} {s : Slice} :
-    s.endsWith pat = false ↔ ¬ (pat.toList <:+ s.copy.toList) := by
-  simp [endsWith_string_eq_endsWith_toSlice]
-
-@[simp]
-theorem dropSuffix?_string_empty {s : Slice} : s.dropSuffix? "" = some s := by
-  simpa [dropSuffix?_string_eq_dropSuffix?_toSlice] using dropSuffix?_slice_of_isEmpty (by simp)
-
-theorem eq_append_of_dropSuffix?_string_eq_some {pat : String} {s res : Slice} (h : s.dropSuffix? pat = some res) :
-    s.copy = res.copy ++ pat := by
-  rw [dropSuffix?_string_eq_dropSuffix?_toSlice] at h
-  simpa using eq_append_of_dropSuffix?_slice_eq_some h
-
 end Slice
 
 theorem skipPrefix?_slice_of_isEmpty {pat : Slice} {s : String} (hpat : pat.isEmpty = true) :
@@ -193,12 +127,12 @@ theorem startsWith_slice_of_isEmpty {pat : Slice} {s : String} (hpat : pat.isEmp
 @[simp]
 theorem startsWith_slice_iff {pat : Slice} {s : String} :
     s.startsWith pat ↔ pat.copy.toList <+: s.toList := by
-  simp [← startsWith_toSlice]
+  simp [startsWith_eq_startsWith_toSlice]
 
 @[simp]
 theorem startsWith_slice_eq_false_iff {pat : Slice} {s : String} :
     s.startsWith pat = false ↔ ¬ (pat.copy.toList <+: s.toList) := by
-  simp [← startsWith_toSlice]
+  simp [startsWith_eq_startsWith_toSlice]
 
 theorem dropPrefix?_slice_of_isEmpty {pat : Slice} {s : String} (hpat : pat.isEmpty = true) :
     s.dropPrefix? pat = some s.toSlice := by
@@ -224,21 +158,21 @@ theorem skipPrefix?_string_eq_some_iff {pat s : String} {pos : s.Pos} :
 
 @[simp]
 theorem startsWith_string_empty {s : String} : s.startsWith "" = true := by
-  simp [← startsWith_toSlice]
+  simp [startsWith_eq_startsWith_toSlice]
 
 @[simp]
 theorem startsWith_string_iff {pat s : String} :
     s.startsWith pat ↔ pat.toList <+: s.toList := by
-  simp [← startsWith_toSlice]
+  simp [startsWith_eq_startsWith_toSlice]
 
 @[simp]
 theorem startsWith_string_eq_false_iff {pat s : String} :
     s.startsWith pat = false ↔ ¬ (pat.toList <+: s.toList) := by
-  simp [← startsWith_toSlice]
+  simp [startsWith_eq_startsWith_toSlice]
 
 @[simp]
 theorem dropPrefix?_string_empty {s : String} : s.dropPrefix? "" = some s.toSlice := by
-  simp [← dropPrefix?_toSlice]
+  simp [dropPrefix?_eq_dropPrefix?_toSlice]
 
 theorem eq_append_of_dropPrefix?_string_eq_some {s pat : String} {res : Slice} (h : s.dropPrefix? pat = some res) :
     s = pat ++ res.copy := by

src/Init/Data/String/Lemmas/Search.lean

@@ -8,8 +8,6 @@ module
 prelude
 public import Init.Data.String.Search
 import all Init.Data.String.Search
-import Init.Data.String.Lemmas.Slice
-import Init.Data.String.Lemmas.FindPos
 
 public section
 
@@ -30,42 +28,4 @@ theorem Pos.le_find {s : String} (pos : s.Pos) (pattern : ρ) [ToForwardSearcher
     pos ≤ pos.find pattern := by
   simp [Pos.find, ← toSlice_le]
 
-@[simp]
-theorem front?_toSlice {s : String} : s.toSlice.front? = s.front? :=
-  (rfl)
-
-theorem front?_eq_get? {s : String} : s.front? = s.startPos.get? := by
-  simp [← front?_toSlice, ← Pos.get?_toSlice, Slice.front?_eq_get?]
-
-theorem front?_eq {s : String} : s.front? = s.toList.head? := by
-  simp [← front?_toSlice, Slice.front?_eq]
-
-@[simp]
-theorem front_toSlice {s : String} : s.toSlice.front = s.front :=
-  (rfl)
-
-@[simp]
-theorem front_eq {s : String} : s.front = s.front?.getD default := by
-  simp [← front_toSlice, Slice.front_eq]
-
-@[simp]
-theorem back?_toSlice {s : String} : s.toSlice.back? = s.back? :=
-  (rfl)
-
-theorem back?_eq_get? {s : String} : s.back? = s.endPos.prev?.bind Pos.get? := by
-  simp only [← back?_toSlice, Slice.back?_eq_get?, endPos_toSlice, Slice.Pos.prev?_eq_dif,
-    startPos_toSlice, Pos.toSlice_inj, Pos.prev?_eq_dif]
-  split <;> simp [← Pos.get?_toSlice, Pos.toSlice_prev]
-
-theorem back?_eq {s : String} : s.back? = s.toList.getLast? := by
-  simp [← back?_toSlice, Slice.back?_eq]
-
-@[simp]
-theorem back_toSlice {s : String} : s.toSlice.back = s.back :=
-  (rfl)
-
-@[simp]
-theorem back_eq {s : String} : s.back = s.back?.getD default := by
-  simp [← back_toSlice, Slice.back_eq]
-
 end String

src/Init/Data/String/Lemmas/Slice.lean

@@ -11,8 +11,6 @@ import all Init.Data.String.Slice
 import Init.Data.String.Lemmas.Pattern.Memcmp
 import Init.Data.String.Lemmas.Basic
 import Init.Data.ByteArray.Lemmas
-import Init.Data.String.Lemmas.IsEmpty
-import Init.Data.String.Lemmas.FindPos
 
 public section
 
@@ -35,104 +33,9 @@ theorem beq_eq_true_iff {s t : Slice} : s == t ↔ s.copy = t.copy := by
 theorem beq_eq_false_iff {s t : Slice} : (s == t) = false ↔ s.copy ≠ t.copy := by
   simp [← Bool.not_eq_true]
 
-theorem beq_eq_decide {s t : Slice} : (s == t) = decide (s.copy = t.copy) :=
-  Bool.eq_iff_iff.2 (by simp)
-
-instance : EquivBEq String.Slice :=
-  equivBEq_of_iff_apply_eq copy (by simp)
-
-theorem beq_list_iff {l l' : List String.Slice} : l == l' ↔ l.map copy = l'.map copy := by
-  induction l generalizing l' <;> cases l' <;> simp_all
-
-theorem beq_list_eq_false_iff {l l' : List String.Slice} :
-    (l == l') = false ↔ l.map copy ≠ l'.map copy := by
-  simp [← Bool.not_eq_true, beq_list_iff]
-
-theorem beq_list_eq_decide {l l' : List String.Slice} :
-    (l == l') = decide (l.map copy = l'.map copy) :=
-  Bool.eq_iff_iff.2 (by simp [beq_list_iff])
+theorem beq_eq_decide {s t : Slice} : (s == t) = decide (s.copy = t.copy) := by
+  cases h : s == t <;> simp_all
 
 end BEq
 
-namespace Pos
-
-theorem get?_eq_dif {s : Slice} {p : s.Pos} : p.get? = if h : p = s.endPos then none else some (p.get h) :=
-  (rfl)
-
-theorem get?_eq_some_get {s : Slice} {p : s.Pos} (h : p ≠ s.endPos) : p.get? = some (p.get h) := by
-  simp [Pos.get?, h]
-
-@[simp]
-theorem get?_eq_none_iff {s : Slice} {p : s.Pos} : p.get? = none ↔ p = s.endPos := by
-  simp [Pos.get?]
-
-theorem get?_eq_none {s : Slice} {p : s.Pos} (h : p = s.endPos) : p.get? = none :=
-  get?_eq_none_iff.2 h
-
-@[simp]
-theorem get?_endPos {s : Slice} : s.endPos.get? = none := by
-  simp
-
-end Pos
-
-end Slice
-
-namespace Pos
-
-theorem get?_toSlice {s : String} {p : s.Pos} : p.toSlice.get? = p.get? :=
-  (rfl)
-
-theorem get?_eq_dif {s : String} {p : s.Pos} : p.get? = if h : p = s.endPos then none else some (p.get h) := by
-  simp [← get?_toSlice, Slice.Pos.get?_eq_dif]
-
-theorem get?_eq_some_get {s : String} {p : s.Pos} (h : p ≠ s.endPos) : p.get? = some (p.get h) := by
-  simpa [← get?_toSlice] using Slice.Pos.get?_eq_some_get (by simpa)
-
-@[simp]
-theorem get?_eq_none_iff {s : String} {p : s.Pos} : p.get? = none ↔ p = s.endPos := by
-  simp [← get?_toSlice]
-
-theorem get?_eq_none {s : String} {p : s.Pos} (h : p = s.endPos) : p.get? = none :=
-  get?_eq_none_iff.2 h
-
-@[simp]
-theorem get?_endPos {s : String} : s.endPos.get? = none := by
-  simp
-
-end Pos
-
-namespace Slice
-
-theorem front?_eq_get? {s : Slice} : s.front? = s.startPos.get? :=
-  (rfl)
-
-theorem front?_eq {s : Slice} : s.front? = s.copy.toList.head? := by
-  simp only [front?_eq_get?, Pos.get?_eq_dif]
-  split
-  · simp_all [startPos_eq_endPos_iff, eq_comm (a := none)]
-  · rename_i h
-    obtain ⟨t, ht⟩ := s.splits_startPos.exists_eq_singleton_append h
-    simp [ht]
-
-@[simp]
-theorem front_eq {s : Slice} : s.front = s.front?.getD default := by
-  simp [front]
-
-theorem back?_eq_get? {s : Slice} : s.back? = s.endPos.prev?.bind Pos.get? :=
-  (rfl)
-
-theorem back?_eq {s : Slice} : s.back? = s.copy.toList.getLast? := by
-  simp [back?_eq_get?, Pos.prev?_eq_dif]
-  split
-  · simp_all [startPos_eq_endPos_iff, eq_comm (a := s.endPos), eq_comm (a := none)]
-  · rename_i h
-    obtain ⟨t, ht⟩ := s.splits_endPos.exists_eq_append_singleton_of_ne_startPos h
-    simp [ht, Pos.get?_eq_some_get]
-
-@[simp]
-theorem back_eq {s : Slice} : s.back = s.back?.getD default := by
-  simp [back]
-
-end Slice
-
-end String
+end String.Slice

src/Init/Data/String/Lemmas/Splits.lean

@@ -17,8 +17,6 @@ import Init.Data.String.OrderInstances
 import Init.Data.Nat.Order
 import Init.Omega
 import Init.Data.String.Lemmas.FindPos
-import Init.Data.List.TakeDrop
-import Init.Data.List.Nat.TakeDrop
 
 /-!
 # `Splits` predicates on `String.Pos` and `String.Slice.Pos`.
@@ -99,11 +97,6 @@ theorem Pos.splits {s : String} (p : s.Pos) :
   eq_append := by simp [← toByteArray_inj, Slice.toByteArray_copy, ← size_toByteArray]
   offset_eq_rawEndPos := by simp
 
-@[simp]
-theorem sliceTo_append_sliceFrom {s : String} {pos : s.Pos} :
-    (s.sliceTo pos).copy ++ (s.sliceFrom pos).copy = s :=
-  pos.splits.eq_append.symm
-
 theorem Slice.Pos.splits {s : Slice} (p : s.Pos) :
     p.Splits (s.sliceTo p).copy (s.sliceFrom p).copy where
   eq_append := copy_eq_copy_sliceTo
@@ -372,7 +365,7 @@ theorem Slice.Pos.Splits.of_prev {s : Slice} {p : s.Pos} {hp}
   obtain ⟨rfl, rfl, rfl⟩ := by simpa using h.eq (splits_prev p hp)
   exact splits_prev_right p hp
 
-theorem Slice.copy_sliceTo_eq_iff_exists_splits {s : Slice} {p : s.Pos} {t₁ : String} :
+theorem Slice.sliceTo_copy_eq_iff_exists_splits {s : Slice} {p : s.Pos} {t₁ : String} :
     (s.sliceTo p).copy = t₁ ↔ ∃ t₂, p.Splits t₁ t₂ := by
   refine ⟨?_, ?_⟩
   · rintro rfl
@@ -380,37 +373,13 @@ theorem Slice.copy_sliceTo_eq_iff_exists_splits {s : Slice} {p : s.Pos} {t₁ :
   · rintro ⟨t₂, h⟩
     exact p.splits.eq_left h
 
-theorem Slice.copy_sliceTo_eq_iff_splits {s : Slice} {p : s.Pos} {t₁ : String} :
-    (s.sliceTo p).copy = t₁ ↔ p.Splits t₁ (s.sliceFrom p).copy :=
-  ⟨fun h => h ▸ p.splits, p.splits.eq_left⟩
-
-theorem Slice.copy_sliceFrom_eq_iff_exists_splits {s : Slice} {p : s.Pos} {t₂ : String} :
-    (s.sliceFrom p).copy = t₂ ↔ ∃ t₁, p.Splits t₁ t₂ := by
+theorem sliceTo_copy_eq_iff_exists_splits {s : String} {p : s.Pos} {t₁ : String} :
+    (s.sliceTo p).copy = t₁ ↔ ∃ t₂, p.Splits t₁ t₂ := by
   refine ⟨?_, ?_⟩
   · rintro rfl
     exact ⟨_, p.splits⟩
   · rintro ⟨t₂, h⟩
-    exact p.splits.eq_right h
-
-theorem Slice.copy_sliceFrom_eq_iff_splits {s : Slice} {p : s.Pos} {t₂ : String} :
-    (s.sliceFrom p).copy = t₂ ↔ p.Splits (s.sliceTo p).copy t₂ :=
-  ⟨fun h => h ▸ p.splits, p.splits.eq_right⟩
-
-theorem copy_sliceTo_eq_iff_exists_splits {s : String} {p : s.Pos} {t₁ : String} :
-    (s.sliceTo p).copy = t₁ ↔ ∃ t₂, p.Splits t₁ t₂ := by
-  simp [← Pos.splits_toSlice_iff, ← Slice.copy_sliceTo_eq_iff_exists_splits]
-
-theorem copy_sliceTo_eq_iff_splits {s : String} {p : s.Pos} {t₁ : String} :
-    (s.sliceTo p).copy = t₁ ↔ p.Splits t₁ (s.sliceFrom p).copy :=
-  ⟨fun h => h ▸ p.splits, p.splits.eq_left⟩
-
-theorem copy_sliceFrom_eq_iff_exists_splits {s : String} {p : s.Pos} {t₂ : String} :
-    (s.sliceFrom p).copy = t₂ ↔ ∃ t₁, p.Splits t₁ t₂ := by
-  simp [← Pos.splits_toSlice_iff, ← Slice.copy_sliceFrom_eq_iff_exists_splits]
-
-theorem copy_sliceFrom_eq_iff_splits {s : String} {p : s.Pos} {t₂ : String} :
-    (s.sliceFrom p).copy = t₂ ↔ p.Splits (s.sliceTo p).copy t₂ :=
-  ⟨fun h => h ▸ p.splits, p.splits.eq_right⟩
+    exact p.splits.eq_left h
 
 theorem Pos.Splits.offset_eq_decreaseBy {s : String} {p : s.Pos} (h : p.Splits t₁ t₂) :
     p.offset = s.rawEndPos.decreaseBy t₂.utf8ByteSize := by
@@ -456,7 +425,8 @@ theorem Slice.splits_singleton_iff {s : Slice} {p : s.Pos} {c : Char} {t : Strin
       simp [startPos_ne_endPos_iff, ← copy_ne_empty_iff, h.eq_append]
     have spl : (s.startPos.next this).Splits (singleton c) t := by
       rw [← empty_append (s := singleton c)]
-      exact Pos.Splits.next (by simp [h.eq_append])
+      apply Pos.Splits.next
+      simp [h.eq_append]
     refine ⟨this, ⟨h.pos_eq spl, ?_, h.eq_append⟩⟩
     rw [← empty_append (s := singleton c)] at spl
     exact spl.get_eq_of_singleton
@@ -470,27 +440,6 @@ theorem splits_singleton_iff {s : String} {p : s.Pos} {c : Char} {t : String} :
   rw [← Pos.splits_toSlice_iff, Slice.splits_singleton_iff]
   simp [← Pos.ofToSlice_inj]
 
-theorem Slice.splits_singleton_right_iff {s : Slice} {p : s.Pos} {c : Char} {t : String} :
-    p.Splits t (singleton c) ↔
-      ∃ h, p = s.endPos.prev h ∧ (s.endPos.prev h).get (by simp) = c ∧ s.copy = t ++ singleton c := by
-  refine ⟨fun h => ?_, ?_⟩
-  · have : s.endPos ≠ s.startPos := by
-      simp [ne_comm (a := s.endPos), startPos_ne_endPos_iff, ← copy_ne_empty_iff, h.eq_append]
-    have spl : (s.endPos.prev this).Splits t (singleton c) := by
-      rw [← append_empty (s := singleton c)]
-      exact Pos.Splits.prev (by simp [h.eq_append])
-    refine ⟨this, ⟨h.pos_eq spl, ?_, h.eq_append⟩⟩
-    exact (h.eq_append ▸ Pos.next_prev (h := this) ▸ s.splits_endPos).get_eq_of_singleton
-  · rintro ⟨h, ⟨rfl, rfl, h'⟩⟩
-    rw [← String.append_empty (s := singleton _)]
-    exact Pos.Splits.prev (by simp [h'])
-
-theorem splits_singleton_right_iff {s : String} {p : s.Pos} {c : Char} {t : String} :
-    p.Splits t (singleton c) ↔
-      ∃ h, p = s.endPos.prev h ∧ (s.endPos.prev h).get (by simp) = c ∧ s = t ++ singleton c := by
-  rw [← Pos.splits_toSlice_iff, Slice.splits_singleton_right_iff]
-  simp [← Pos.ofToSlice_inj, Pos.prev_toSlice]
-
 theorem Slice.splits_next_startPos {s : Slice} {h : s.startPos ≠ s.endPos} :
     (s.startPos.next h).Splits
       (singleton (s.startPos.get h)) (s.sliceFrom (s.startPos.next h)).copy := by
@@ -505,20 +454,6 @@ theorem splits_next_startPos {s : String} {h : s.startPos ≠ s.endPos} :
   rw [← Pos.splits_toSlice_iff]
   apply (Slice.splits_next_startPos).of_eq <;> simp [String.Pos.next_toSlice]
 
-theorem Slice.splits_prev_endPos {s : Slice} {h : s.endPos ≠ s.startPos} :
-    (s.endPos.prev h).Splits
-      (s.sliceTo (s.endPos.prev h)).copy (singleton ((s.endPos.prev h).get (by simp))) := by
-  rw [← String.append_empty (s := singleton _)]
-  apply Slice.Pos.Splits.prev
-  have := Slice.Pos.splits_prev_right s.endPos h
-  rwa [copy_sliceFrom_endPos] at this
-
-theorem splits_prev_endPos {s : String} {h : s.endPos ≠ s.startPos} :
-    (s.endPos.prev h).Splits
-      (s.sliceTo (s.endPos.prev h)).copy (singleton ((s.endPos.prev h).get (by simp))) := by
-  rw [← Pos.splits_toSlice_iff]
-  apply (Slice.splits_prev_endPos).of_eq <;> simp [String.Pos.prev_toSlice, h]
-
 theorem Slice.Pos.Splits.toByteArray_eq_left {s : Slice} {p : s.Pos} {t₁ t₂ : String} (h : p.Splits t₁ t₂) :
     t₁.toByteArray = s.copy.toByteArray.extract 0 p.offset.byteIdx := by
   rw [h.eq_left p.splits]
@@ -662,28 +597,6 @@ theorem Pos.splits_append_rawEndPos {s t : String} :
   eq_append := rfl
   offset_eq_rawEndPos := rfl
 
-/--
-Given a slice `s` such that `s.copy = t₁ ++ t₂`, obtain the position sitting between `t₁` and `t₂`.
--/
-def Slice.Pos.ofEqAppend {s : Slice} {t₁ t₂ : String} (h : s.copy = t₁ ++ t₂) : s.Pos :=
-  s.pos t₁.rawEndPos
-    (by simpa [← Pos.Raw.isValid_copy_iff, h] using ((Pos.Raw.isValid_rawEndPos).append_right t₂))
-
-theorem Slice.Pos.splits_ofEqAppend {s : Slice} {t₁ t₂ : String} (h : s.copy = t₁ ++ t₂) :
-    (ofEqAppend h).Splits t₁ t₂ where
-  eq_append := h
-  offset_eq_rawEndPos := by simp [ofEqAppend]
-
-/--
-Given a string `s` such that `s = t₁ ++ t₂`, obtain the position sitting between `t₁` and `t₂`.
--/
-def Pos.ofEqAppend {s t₁ t₂ : String} (h : s = t₁ ++ t₂) : s.Pos :=
-  ((t₁ ++ t₂).pos t₁.rawEndPos ((Pos.Raw.isValid_rawEndPos).append_right t₂)).cast h.symm
-
-theorem Pos.splits_ofEqAppend {s t₁ t₂ : String} (h : s = t₁ ++ t₂) : (ofEqAppend h).Splits t₁ t₂ where
-  eq_append := h
-  offset_eq_rawEndPos := by simp [ofEqAppend]
-
 theorem Pos.Splits.copy_sliceTo_eq {s : String} {p : s.Pos} (h : p.Splits t₁ t₂) :
     (s.sliceTo p).copy = t₁ :=
   p.splits.eq_left h
@@ -736,91 +649,4 @@ theorem Slice.splits_slice {s : Slice} {p₀ p₁ : s.Pos} (h) (p : (s.slice p
     p.Splits (s.slice p₀ (Pos.ofSlice p) Pos.le_ofSlice).copy (s.slice (Pos.ofSlice p) p₁ Pos.ofSlice_le).copy := by
   simpa using p.splits
 
-theorem Slice.Pos.Splits.nextn {s : Slice} {t₁ t₂ : String} {p : s.Pos} (h : p.Splits t₁ t₂) (n : Nat) :
-    (p.nextn n).Splits (t₁ ++ String.ofList (t₂.toList.take n)) (String.ofList (t₂.toList.drop n)) := by
-  induction n generalizing p t₁ t₂ with
-  | zero => simpa
-  | succ n ih =>
-    rw [Pos.nextn_add_one]
-    split
-    · simp_all
-    · obtain ⟨t₂, rfl⟩ := h.exists_eq_singleton_append ‹_›
-      simpa [← append_assoc] using ih h.next
-
-theorem Slice.splits_nextn_startPos (s : Slice) (n : Nat) :
-    (s.startPos.nextn n).Splits (String.ofList (s.copy.toList.take n)) (String.ofList (s.copy.toList.drop n)) := by
-  simpa using s.splits_startPos.nextn n
-
-theorem Pos.Splits.nextn {s t₁ t₂ : String} {p : s.Pos} (h : p.Splits t₁ t₂) (i : Nat) :
-    (p.nextn i).Splits (t₁ ++ String.ofList (t₂.toList.take i)) (String.ofList (t₂.toList.drop i)) := by
-  simpa [← splits_toSlice_iff, toSlice_nextn] using h.toSlice.nextn i
-
-theorem splits_nextn_startPos (s : String) (n : Nat) :
-    (s.startPos.nextn n).Splits (String.ofList (s.toList.take n)) (String.ofList (s.toList.drop n)) := by
-  simpa using s.splits_startPos.nextn n
-
-theorem Slice.Pos.Splits.prevn {s : Slice} {t₁ t₂ : String} {p : s.Pos} (h : p.Splits t₁ t₂) (n : Nat) :
-    (p.prevn n).Splits (String.ofList (t₁.toList.take (t₁.length - n))) (String.ofList (t₁.toList.drop (t₁.length - n)) ++ t₂) := by
-  induction n generalizing p t₁ t₂ with
-  | zero => simpa [← String.length_toList]
-  | succ n ih =>
-    rw [Pos.prevn_add_one]
-    split
-    · simp_all
-    · obtain ⟨t₂, rfl⟩ := h.exists_eq_append_singleton_of_ne_startPos ‹_›
-      simpa [Nat.add_sub_add_right, List.take_append, List.drop_append, ← append_assoc] using ih h.prev
-
-theorem Slice.splits_prevn_endPos (s : Slice) (n : Nat) :
-    (s.endPos.prevn n).Splits (String.ofList (s.copy.toList.take (s.copy.length - n)))
-      (String.ofList (s.copy.toList.drop (s.copy.length - n))) := by
-  simpa using s.splits_endPos.prevn n
-
-theorem Pos.Splits.prevn {s t₁ t₂ : String} {p : s.Pos} (h : p.Splits t₁ t₂) (n : Nat) :
-    (p.prevn n).Splits (String.ofList (t₁.toList.take (t₁.length - n))) (String.ofList (t₁.toList.drop (t₁.length - n)) ++ t₂) := by
-  simpa [← splits_toSlice_iff, toSlice_prevn] using h.toSlice.prevn n
-
-theorem splits_prevn_endPos (s : String) (n : Nat) :
-    (s.endPos.prevn n).Splits (String.ofList (s.toList.take (s.length - n))) (String.ofList (s.toList.drop (s.length - n))) := by
-  simpa using s.splits_endPos.prevn n
-
-@[simp]
-theorem Slice.copy_sliceFrom_cast {s t : Slice} (hst : s.copy = t.copy) {pos : s.Pos} :
-    (t.sliceFrom (pos.cast hst)).copy = (s.sliceFrom pos).copy := by
-  simpa [copy_sliceFrom_eq_iff_exists_splits] using ⟨_, pos.splits⟩
-
-@[simp]
-theorem Slice.copy_sliceTo_cast {s t : Slice} (hst : s.copy = t.copy) {pos : s.Pos} :
-    (t.sliceTo (pos.cast hst)).copy = (s.sliceTo pos).copy := by
-  simpa [copy_sliceTo_eq_iff_exists_splits] using ⟨_, pos.splits⟩
-
-@[simp]
-theorem copy_sliceFrom_cast {s t : String} (hst : s = t) {pos : s.Pos} :
-    (t.sliceFrom (pos.cast hst)).copy = (s.sliceFrom pos).copy := by
-  simpa [copy_sliceFrom_eq_iff_exists_splits] using ⟨_, pos.splits⟩
-
-@[simp]
-theorem copy_sliceTo_cast {s t : String} (hst : s = t) {pos : s.Pos} :
-    (t.sliceTo (pos.cast hst)).copy = (s.sliceTo pos).copy := by
-  simpa [copy_sliceTo_eq_iff_exists_splits] using ⟨_, pos.splits⟩
-
-theorem Slice.Pos.sliceFrom_cast {s t : Slice} {hst : s.copy = t.copy} (p q : s.Pos) {h} :
-    Slice.Pos.sliceFrom (p.cast hst) (q.cast hst) h =
-      (Slice.Pos.sliceFrom p q (by simpa using h)).cast (by simp) := by
-  ext1; simp
-
-theorem Slice.Pos.sliceTo_cast {s t : Slice} {hst : s.copy = t.copy} (p q : s.Pos) {h} :
-    Slice.Pos.sliceTo (p.cast hst) (q.cast hst) h =
-      (Slice.Pos.sliceTo p q (by simpa using h)).cast (by simp) := by
-  ext1; simp
-
-theorem Pos.sliceFrom_cast {s t : String} {hst : s = t} (p q : s.Pos) {h} :
-    Pos.sliceFrom (p.cast hst) (q.cast hst) h =
-      (Pos.sliceFrom p q (by simpa using h)).cast (by simp) := by
-  ext1; simp
-
-theorem Pos.sliceTo_cast {s t : String} {hst : s = t} (p q : s.Pos) {h} :
-    Pos.sliceTo (p.cast hst) (q.cast hst) h =
-      (Pos.sliceTo p q (by simpa using h)).cast (by simp) := by
-  ext1; simp
-
 end String

src/Init/Data/String/Lemmas/StringOrder.lean

@@ -1,49 +0,0 @@
-/-
-Copyright (c) 2024 Amazon.com, Inc. or its affiliates. All Rights Reserved.
-Released under Apache 2.0 license as described in the file LICENSE.
-Authors: Leonardo de Moura
--/
-module
-
-prelude
-public import Init.Data.String.Basic
-public import Init.Data.Order.Classes
-import Init.Data.List.Lex
-import Init.Data.Char.Lemmas
-import Init.Data.Char.Order
-import Init.Data.Order.Factories
-import Init.Data.Order.Lemmas
-
-public section
-
-open Std
-
-namespace String
-
-@[simp] protected theorem not_le {a b : String} : ¬ a ≤ b ↔ b < a := Decidable.not_not
-@[simp] protected theorem not_lt {a b : String} : ¬ a < b ↔ b ≤ a := Iff.rfl
-@[simp] protected theorem le_refl (a : String) : a ≤ a := List.le_refl _
-@[simp] protected theorem lt_irrefl (a : String) : ¬ a < a := List.lt_irrefl _
-
-attribute [local instance] Char.notLTTrans Char.ltTrichotomous Char.ltAsymm
-
-protected theorem le_trans {a b c : String} : a ≤ b → b ≤ c → a ≤ c := List.le_trans
-protected theorem lt_trans {a b c : String} : a < b → b < c → a < c := List.lt_trans
-protected theorem le_total (a b : String) : a ≤ b ∨ b ≤ a := List.le_total _ _
-protected theorem le_antisymm {a b : String} : a ≤ b → b ≤ a → a = b := fun h₁ h₂ => String.ext (List.le_antisymm (as := a.toList) (bs := b.toList) h₁ h₂)
-protected theorem lt_asymm {a b : String} (h : a < b) : ¬ b < a := List.lt_asymm h
-protected theorem ne_of_lt {a b : String} (h : a < b) : a ≠ b := by
-  have := String.lt_irrefl a
-  intro h; subst h; contradiction
-
-instance instIsLinearOrder : IsLinearOrder String := by
-  apply IsLinearOrder.of_le
-  case le_antisymm => constructor; apply String.le_antisymm
-  case le_trans => constructor; apply String.le_trans
-  case le_total => constructor; apply String.le_total
-
-instance : LawfulOrderLT String where
-  lt_iff a b := by
-    simp [← String.not_le, Decidable.imp_iff_not_or, Std.Total.total]
-
-end String

src/Init/Data/String/Lemmas/TakeDrop.lean

@@ -1,86 +0,0 @@
-/-
-Copyright (c) 2026 Lean FRO, LLC. All rights reserved.
-Released under Apache 2.0 license as described in the file LICENSE.
-Author: Julia Markus Himmel
--/
-module
-
-prelude
-public import Init.Data.String.TakeDrop
-import all Init.Data.String.Slice
-import all Init.Data.String.TakeDrop
-import Init.Data.String.Lemmas.Splits
-
-public section
-
-namespace String
-
-namespace Slice
-
-theorem drop_eq_sliceFrom {s : Slice} {n : Nat} : s.drop n = s.sliceFrom (s.startPos.nextn n) :=
-  (rfl)
-
-@[simp]
-theorem toList_copy_drop {s : Slice} {n : Nat} : (s.drop n).copy.toList = s.copy.toList.drop n := by
-  simp [drop_eq_sliceFrom, (s.splits_nextn_startPos n).copy_sliceFrom_eq]
-
-theorem dropEnd_eq_sliceTo {s : Slice} {n : Nat} : s.dropEnd n = s.sliceTo (s.endPos.prevn n) :=
-  (rfl)
-
-@[simp]
-theorem toList_copy_dropEnd {s : Slice} {n : Nat} :
-    (s.dropEnd n).copy.toList = s.copy.toList.take (s.copy.length - n) := by
-  simp [dropEnd_eq_sliceTo, (s.splits_prevn_endPos n).copy_sliceTo_eq]
-
-theorem take_eq_sliceTo {s : Slice} {n : Nat} : s.take n = s.sliceTo (s.startPos.nextn n) :=
-  (rfl)
-
-@[simp]
-theorem toList_copy_take {s : Slice} {n : Nat} : (s.take n).copy.toList = s.copy.toList.take n := by
-  simp [take_eq_sliceTo, (s.splits_nextn_startPos n).copy_sliceTo_eq]
-
-theorem takeEnd_eq_sliceFrom {s : Slice} {n : Nat} : s.takeEnd n = s.sliceFrom (s.endPos.prevn n) :=
-  (rfl)
-
-@[simp]
-theorem toList_copy_takeEnd {s : Slice} {n : Nat} :
-    (s.takeEnd n).copy.toList = s.copy.toList.drop (s.copy.length - n) := by
-  simp [takeEnd_eq_sliceFrom, (s.splits_prevn_endPos n).copy_sliceFrom_eq]
-
-end Slice
-
-@[simp]
-theorem drop_toSlice {s : String} {n : Nat} : s.toSlice.drop n = s.drop n :=
-  (rfl)
-
-@[simp]
-theorem toList_copy_drop {s : String} {n : Nat} : (s.drop n).copy.toList = s.toList.drop n := by
-  simp [← drop_toSlice]
-
-@[simp]
-theorem dropEnd_toSlice {s : String} {n : Nat} : s.toSlice.dropEnd n = s.dropEnd n :=
-  (rfl)
-
-@[simp]
-theorem toList_copy_dropEnd {s : String} {n : Nat} :
-    (s.dropEnd n).copy.toList = s.toList.take (s.length - n) := by
-  simp [← dropEnd_toSlice]
-
-@[simp]
-theorem take_toSlice {s : String} {n : Nat} : s.toSlice.take n = s.take n :=
-  (rfl)
-
-@[simp]
-theorem toList_copy_take {s : String} {n : Nat} : (s.take n).copy.toList = s.toList.take n := by
-  simp [← take_toSlice]
-
-@[simp]
-theorem takeEnd_toSlice {s : String} {n : Nat} : s.toSlice.takeEnd n = s.takeEnd n :=
-  (rfl)
-
-@[simp]
-theorem toList_copy_takeEnd {s : String} {n : Nat} :
-    (s.takeEnd n).copy.toList = s.toList.drop (s.length - n) := by
-  simp [← takeEnd_toSlice]
-
-end String

src/Init/Data/String/Pattern/Basic.lean

@@ -96,44 +96,6 @@ theorem endPos_ofSliceFrom {s : Slice} {p : s.Pos} {st : SearchStep (s.sliceFrom
     st.ofSliceFrom.endPos = Slice.Pos.ofSliceFrom st.endPos := by
   cases st <;> simp [ofSliceFrom]
 
-/--
-Converts a {lean}`SearchStep s` into a {lean}`SearchStep t` by applying {name}`Slice.Pos.cast` to the
-start and end position.
--/
-@[inline]
-def cast {s t : Slice} (hst : s.copy = t.copy) : SearchStep s → SearchStep t
-  | .rejected startPos endPos => .rejected (startPos.cast hst) (endPos.cast hst)
-  | .matched startPos endPos => .matched (startPos.cast hst) (endPos.cast hst)
-
-@[simp]
-theorem cast_rejected {s t : Slice} {hst : s.copy = t.copy} {startPos endPos : s.Pos} :
-    (SearchStep.rejected startPos endPos).cast hst = .rejected (startPos.cast hst) (endPos.cast hst) :=
-  (rfl)
-
-@[simp]
-theorem cast_matched {s t : Slice} {hst : s.copy = t.copy} {startPos endPos : s.Pos} :
-    (SearchStep.matched startPos endPos).cast hst = .matched (startPos.cast hst) (endPos.cast hst) :=
-  (rfl)
-
-@[simp]
-theorem startPos_cast {s t : Slice} (hst : s.copy = t.copy) {st : SearchStep s} :
-    (st.cast hst).startPos = st.startPos.cast hst := by
-  cases st <;> simp
-
-@[simp]
-theorem endPos_cast {s t : Slice} (hst : s.copy = t.copy) {st : SearchStep s} :
-    (st.cast hst).endPos = st.endPos.cast hst := by
-  cases st <;> simp
-
-@[simp]
-theorem cast_rfl {s : Slice} {st : SearchStep s} : st.cast rfl = st := by
-  cases st <;> simp
-
-@[simp]
-theorem cast_cast {s t u : Slice} {hst : s.copy = t.copy} {htu : t.copy = u.copy} {st : SearchStep s} :
-    (st.cast hst).cast htu = st.cast (hst.trans htu) := by
-  cases st <;> simp
-
 end SearchStep
 
 /--
@@ -155,7 +117,7 @@ class ForwardPattern {ρ : Type} (pat : ρ) where
   -/
   startsWith : (s : Slice) → Bool := fun s => (skipPrefix? s).isSome
 
-@[deprecated ForwardPattern.skipPrefix? (since := "2026-03-19")]
+@[deprecated ForwardPattern.dropPrefix? (since := "2026-03-19")]
 def ForwardPattern.dropPrefix? {ρ : Type} (pat : ρ) [ForwardPattern pat] (s : Slice) : Option s.Pos :=
   ForwardPattern.skipPrefix? pat s
 

src/Init/Data/String/Pattern/Char.lean

@@ -47,8 +47,8 @@ instance {c : Char} : LawfulBackwardPattern c where
   skipSuffixOfNonempty?_eq h := LawfulBackwardPattern.skipSuffixOfNonempty?_eq (pat := (· == c)) h
   endsWith_eq s := LawfulBackwardPattern.endsWith_eq (pat := (· == c)) s
 
-instance {c : Char} : ToBackwardSearcher c (ToBackwardSearcher.DefaultBackwardSearcher (· == c)) where
-  toSearcher s := ToBackwardSearcher.toSearcher (· == c) s
+instance {c : Char} : ToBackwardSearcher c (ToBackwardSearcher.DefaultBackwardSearcher c) :=
+  .defaultImplementation
 
 end Char
 

src/Init/Data/String/Pattern/Pred.lean

@@ -139,9 +139,8 @@ instance {p : Char → Prop} [DecidablePred p] : LawfulBackwardPattern p where
   skipSuffixOfNonempty?_eq h := LawfulBackwardPattern.skipSuffixOfNonempty?_eq (pat := (decide <| p ·)) h
   endsWith_eq s := LawfulBackwardPattern.endsWith_eq (pat := (decide <| p ·)) s
 
-instance {p : Char → Prop} [DecidablePred p] :
-    ToBackwardSearcher p (ToBackwardSearcher.DefaultBackwardSearcher (decide <| p ·)) where
-  toSearcher s := ToBackwardSearcher.toSearcher (decide <| p ·) s
+instance {p : Char → Prop} [DecidablePred p] : ToBackwardSearcher p (ToBackwardSearcher.DefaultBackwardSearcher p) :=
+  .defaultImplementation
 
 end Decidable
 

src/Init/Data/String/Search.lean

@@ -311,6 +311,23 @@ def Internal.containsImpl (s : String) (c : Char) : Bool :=
 def Internal.anyImpl (s : String) (p : Char → Bool) :=
   String.any s p
 
+/--
+Checks whether a slice only consists of matches of the pattern {name}`pat`.
+
+Short-circuits at the first pattern mis-match.
+
+This function is generic over all currently supported patterns.
+
+Examples:
+ * {lean}`"brown".all Char.isLower = true`
+ * {lean}`"brown and orange".all Char.isLower = false`
+ * {lean}`"aaaaaa".all 'a' = true`
+ * {lean}`"aaaaaa".all "aa" = true`
+ * {lean}`"aaaaaaa".all "aa" = false`
+-/
+@[inline, suggest_for String.every] def all (s : String) (pat : ρ) [ForwardPattern pat] : Bool :=
+  s.toSlice.all pat
+
 /--
 Checks whether the string can be interpreted as the decimal representation of a natural number.
 

src/Init/Data/String/Slice.lean

@@ -11,7 +11,7 @@ public import Init.Data.Ord.Basic
 public import Init.Data.Iterators.Combinators.FilterMap
 public import Init.Data.String.ToSlice
 public import Init.Data.String.Subslice
-public import Init.Data.String.Iter.Basic
+public import Init.Data.String.Iter
 public import Init.Data.String.Iterate
 import Init.Data.Iterators.Consumers.Collect
 import Init.Data.Iterators.Consumers.Loop
@@ -84,11 +84,10 @@ instance : ToString String.Slice where
 theorem toStringToString_eq : ToString.toString = String.Slice.copy := (rfl)
 
 @[extern "lean_slice_hash"]
-protected def hash (s : @& Slice) : UInt64 :=
-  String.hash s.copy
+opaque hash (s : @& Slice) : UInt64
 
 instance : Hashable Slice where
-  hash := Slice.hash
+  hash := hash
 
 instance : LT Slice where
   lt x y := x.copy < y.copy
@@ -426,13 +425,13 @@ Advances {name}`pos` as long as {name}`pat` matches.
 -/
 @[specialize pat]
 def Pos.skipWhile {s : Slice} (pos : s.Pos) (pat : ρ) [ForwardPattern pat] : s.Pos :=
-  match pos.skip? pat with
-  | some nextCurr =>
-    if pos < nextCurr then
-      skipWhile nextCurr pat
+  if let some nextCurr := ForwardPattern.skipPrefix? pat (s.sliceFrom pos) then
+    if pos < Pos.ofSliceFrom nextCurr then
+      skipWhile (Pos.ofSliceFrom nextCurr) pat
     else
       pos
-  | none => pos
+  else
+    pos
 termination_by pos
 
 /--
@@ -572,7 +571,7 @@ Examples:
 -/
 @[inline]
 def all (s : Slice) (pat : ρ) [ForwardPattern pat] : Bool :=
-  s.skipPrefixWhile pat == s.endPos
+  s.dropWhile pat |>.isEmpty
 
 end ForwardPatternUsers
 
@@ -706,14 +705,14 @@ Returns {name}`none` otherwise.
 This function is generic over all currently supported patterns.
 -/
 @[inline]
-def Pos.revSkip? {s : Slice} (pos : s.Pos) (pat : ρ) [BackwardPattern pat] : Option s.Pos :=
-  ((s.sliceTo pos).skipSuffix? pat).map Pos.ofSliceTo
+def Pos.revSkip? {s : Slice} (pos : s.Pos) (pat : ρ) [ForwardPattern pat] : Option s.Pos :=
+  ((s.sliceFrom pos).skipPrefix? pat).map Pos.ofSliceFrom
 
 /--
 If {name}`pat` matches a suffix of {name}`s`, returns the remainder. Returns {name}`none` otherwise.
 
 Use {name (scope := "Init.Data.String.Slice")}`String.Slice.dropSuffix` to return the slice
-unchanged when {name}`pat` does not match a suffix.
+unchanged when {name}`pat` does not match a prefix.
 
 This function is generic over all currently supported patterns.
 
@@ -765,53 +764,23 @@ Rewinds {name}`pos` as long as {name}`pat` matches.
 -/
 @[specialize pat]
 def Pos.revSkipWhile {s : Slice} (pos : s.Pos) (pat : ρ) [BackwardPattern pat] : s.Pos :=
-  match pos.revSkip? pat with
-  | some nextCurr =>
-    if nextCurr < pos then
-      revSkipWhile nextCurr pat
+  if let some nextCurr := BackwardPattern.skipSuffix? pat (s.sliceTo pos) then
+    if Pos.ofSliceTo nextCurr < pos then
+      revSkipWhile (Pos.ofSliceTo nextCurr) pat
     else
       pos
-  | none => pos
+  else
+    pos
 termination_by pos.down
 
 /--
-Returns the position at the start of the longest suffix of {name}`s` for which {name}`pat` matches
+Returns the position a the start of the longest suffix of {name}`s` for which {name}`pat` matches
 (potentially repeatedly).
 -/
 @[inline]
 def skipSuffixWhile (s : Slice) (pat : ρ) [BackwardPattern pat] : s.Pos :=
   s.endPos.revSkipWhile pat
 
-/--
-Checks whether a slice only consists of matches of the pattern {name}`pat`, starting from the back
-of the string.
-
-Short-circuits at the first pattern mis-match.
-
-This function is generic over all currently supported patterns.
-
-For many types of patterns, this function can be expected to return the same result as
-{name}`Slice.all`. If mismatches are expected to occur close to the end of the string, this function
-might be more efficient.
-
-For some types of patterns, this function will return a different result than {name}`Slice.all`.
-Consider, for example, a pattern that matches the longest string at the given position that matches
-the regular expression {lean}`"a|aa|ab"`. Then, given the input string {lean}`"aab"`, performing
-{name}`Slice.all` will greedily match the prefix {lean}`"aa"` and then get stuck on the remainder
-{lean}`"b"`, causing it to return {lean}`false`. On the other hand, {name}`Slice.revAll` will match
-the suffix {lean}`"ab"` and then match the remainder {lean}`"a"`, so it will return {lean}`true`.
-
-Examples:
- * {lean}`"brown".toSlice.revAll Char.isLower = true`
- * {lean}`"brown and orange".toSlice.revAll Char.isLower = false`
- * {lean}`"aaaaaa".toSlice.revAll 'a' = true`
- * {lean}`"aaaaaa".toSlice.revAll "aa" = true`
- * {lean}`"aaaaaaa".toSlice.revAll "aa" = false`
--/
-@[inline]
-def revAll (s : Slice) (pat : ρ) [BackwardPattern pat] : Bool :=
-  s.skipSuffixWhile pat == s.startPos
-
 /--
 Creates a new slice that contains the longest suffix of {name}`s` for which {name}`pat` matched
 (potentially repeatedly).
@@ -1182,19 +1151,6 @@ where go (acc : String) (s : Slice) : List Slice → String
   | a :: as => go (acc ++ s ++ a) s as
   | []      => acc
 
-/--
-Appends all the slices in a list of slices, in order.
-
-Use {name}`String.Slice.intercalate` to place a separator string between the strings in a list.
-
-Examples:
- * {lean}`String.Slice.join ["gr", "ee", "n"] = "green"`
- * {lean}`String.Slice.join ["b", "", "l", "", "ue"] = "blue"`
- * {lean}`String.Slice.join [] = ""`
--/
-def join (l : List String.Slice) : String :=
-  l.foldl (fun (r : String) (s : String.Slice) => r ++ s) ""
-
 /--
 Converts a string to the Lean compiler's representation of names. The resulting name is
 hierarchical, and the string is split at the dots ({lean}`'.'`).

src/Init/Data/String/TakeDrop.lean

@@ -224,53 +224,6 @@ Returns the position after the longest prefix of {name}`s` for which {name}`pat`
 @[inline] def skipPrefixWhile (s : String) (pat : ρ) [ForwardPattern pat] : s.Pos :=
   Pos.ofToSlice (s.toSlice.skipPrefixWhile pat)
 
-/--
-Checks whether a string only consists of matches of the pattern {name}`pat`.
-
-Short-circuits at the first pattern mis-match.
-
-This function is generic over all currently supported patterns.
-
-Examples:
- * {lean}`"brown".all Char.isLower = true`
- * {lean}`"brown and orange".all Char.isLower = false`
- * {lean}`"aaaaaa".all 'a' = true`
- * {lean}`"aaaaaa".all "aa" = true`
- * {lean}`"aaaaaaa".all "aa" = false`
--/
-@[inline, suggest_for String.every] def all (s : String) (pat : ρ) [ForwardPattern pat] : Bool :=
-  s.toSlice.all pat
-
-/--
-Checks whether a string only consists of matches of the pattern {name}`pat`, starting from the back
-of the string.
-
-Short-circuits at the first pattern mis-match.
-
-This function is generic over all currently supported patterns.
-
-For many types of patterns, this function can be expected to return the same result as
-{name}`String.all`. If mismatches are expected to occur close to the end of the string, this function
-might be more efficient.
-
-For some types of patterns, this function will return a different result than {name}`String.all`.
-Consider, for example, a pattern that matches the longest string at the given position that matches
-the regular expression {lean}`"a|aa|ab"`. Then, given the input string {lean}`"aab"`, performing
-{name}`String.all` will greedily match the prefix {lean}`"aa"` and then get stuck on the remainder
-{lean}`"b"`, causing it to return {lean}`false`. On the other hand, {name}`String.revAll` will match
-the suffix {lean}`"ab"` and then match the remainder {lean}`"a"`, so it will return {lean}`true`.
-
-Examples:
- * {lean}`"brown".revAll Char.isLower = true`
- * {lean}`"brown and orange".revAll Char.isLower = false`
- * {lean}`"aaaaaa".revAll 'a' = true`
- * {lean}`"aaaaaa".revAll "aa" = true`
- * {lean}`"aaaaaaa".revAll "aa" = false`
--/
-@[inline]
-def revAll (s : String) (pat : ρ) [BackwardPattern pat] : Bool :=
-  s.toSlice.revAll pat
-
 /--
 If {name}`pat` matches at {name}`pos`, returns the position after the end of the match.
 Returns {name}`none` otherwise.
@@ -361,7 +314,7 @@ Returns {name}`none` otherwise.
 This function is generic over all currently supported patterns.
 -/
 @[inline]
-def Pos.revSkip? {s : String} (pos : s.Pos) (pat : ρ) [BackwardPattern pat] : Option s.Pos :=
+def Pos.revSkip? {s : String} (pos : s.Pos) (pat : ρ) [ForwardPattern pat] : Option s.Pos :=
   (pos.toSlice.revSkip? pat).map Pos.ofToSlice
 
 /--
@@ -508,7 +461,7 @@ def dropPrefix? (s : String) (pat : ρ) [ForwardPattern pat] : Option String.Sli
 If {name}`pat` matches a suffix of {name}`s`, returns the remainder. Returns {name}`none` otherwise.
 
 Use {name (scope := "Init.Data.String.TakeDrop")}`String.dropSuffix` to return the slice
-unchanged when {name}`pat` does not match a suffix.
+unchanged when {name}`pat` does not match a prefix.
 
 This is a cheap operation because it does not allocate a new string to hold the result.
 To convert the result into a string, use {name}`String.Slice.copy`.

src/Init/Grind/Util.lean

@@ -30,13 +30,7 @@ simpMatchDiscrsOnly (match 0 with | 0 => true | _ => false) = true
 ```
 using `eq_self`.
 -/
-@[expose] def simpMatchDiscrsOnly {α : Sort u} (a : α) : α := a
-
-/--
-Gadget for protecting lambda abstractions created by `abstractGroundMismatches?`
-from beta reduction during preprocessing. See `ProveEq.lean` for details.
--/
-@[expose] def abstractFn {α : Sort u} (a : α) : α := a
+def simpMatchDiscrsOnly {α : Sort u} (a : α) : α := a
 
 /-- Gadget for representing offsets `t+k` in patterns. -/
 def offset (a b : Nat) : Nat := a + b

src/Init/Notation.lean

@@ -624,23 +624,6 @@ existing code. It may be removed in a future version of the library.
 syntax (name := deprecated) "deprecated" (ppSpace ident)? (ppSpace str)?
     (" (" &"since" " := " str ")")? : attr
 
-/--
-The attribute `@[deprecated_arg old new]` marks a named parameter as deprecated.
-
-When a caller uses the old name with a replacement available, a deprecation warning is emitted
-and the argument is silently forwarded to the new parameter. When no replacement is provided,
-the parameter is treated as removed and using it produces an error.
-
-* `@[deprecated_arg old new (since := "2026-03-18")]` marks `old` as a deprecated alias for `new`.
-* `@[deprecated_arg old new "use foo instead" (since := "2026-03-18")]` adds a custom message.
-* `@[deprecated_arg old (since := "2026-03-18")]` marks `old` as a removed parameter (no replacement).
-* `@[deprecated_arg old "no longer needed" (since := "2026-03-18")]` removed with a custom message.
-
-A warning is emitted if `(since := "...")` is omitted.
--/
-syntax (name := deprecated_arg) "deprecated_arg" ppSpace ident (ppSpace ident)? (ppSpace str)?
-    (" (" &"since" " := " str ")")? : attr
-
 /--
 The attribute `@[suggest_for ..]` on a declaration suggests likely ways in which
 someone might **incorrectly** refer to a definition.

src/Init/Omega/LinearCombo.lean

@@ -36,6 +36,9 @@ private local instance : ToString Int where
 private local instance : Repr Int where
   reprPrec i prec := if i < 0 then Repr.addAppParen (toString i) prec else toString i
 
+private local instance : Append String where
+  append := String.Internal.append
+
 /-- Internal representation of a linear combination of atoms, and a constant term. -/
 structure LinearCombo where
   /-- Constant term. -/

src/Init/Prelude.lean

@@ -185,36 +185,15 @@ example : foo.default = (default, default) :=
 abbrev inferInstance {α : Sort u} [i : α] : α := i
 
 set_option checkBinderAnnotations false in
-/--
-`inferInstanceAs α` synthesizes an instance of type `α` and then adjusts it to conform to the
-expected type `β`, which must be inferable from context.
-
-Example:
+/-- `inferInstanceAs α` synthesizes an instance of type `α` and normalizes it to
+"instance normal form": the result is a constructor application whose sub-instance fields
+are canonical instances and whose types match `α` exactly. This is useful when `α` is
+definitionally equal to some `α'` for which instances are registered, as it prevents
+leaking the definition's RHS at lower transparencies. See `Lean.Meta.InstanceNormalForm`
+for details. Example:
 ```
-def D := Nat
-instance : Inhabited D := inferInstanceAs (Inhabited Nat)
+#check inferInstanceAs (Inhabited Nat) -- Inhabited Nat
 ```
-
-The adjustment will make sure that when the resulting instance will not "leak" the RHS `Nat` when
-reduced at transparency levels below `semireducible`, i.e. where `D` would not be unfolded either,
-preventing "defeq abuse".
-
-More specifically, given the "source type" (the argument) and "target type" (the expected type),
-`inferInstanceAs` synthesizes an instance for the source type and then unfolds and rewraps its
-components (fields, nested instances) as necessary to make them compatible with the target type. The
-individual steps are represented by the following options, which all default to enabled and can be
-disabled to help with porting:
-
-* `backward.inferInstanceAs.wrap`: master switch for instance adjustment in both `inferInstanceAs`
-  and the default deriving handler
-* `backward.inferInstanceAs.wrap.reuseSubInstances`: reuse existing instances for the target type
-  for sub-instance fields to avoid non-defeq instance diamonds
-* `backward.inferInstanceAs.wrap.instances`: wrap non-reducible instances in auxiliary definitions
-* `backward.inferInstanceAs.wrap.data`: wrap data fields in auxiliary definitions (proof fields are
-  always wrapped)
-
-If you just need to synthesize an instance without transporting between types, use `inferInstance`
-instead, potentially with a type annotation for the expected type.
 -/
 abbrev «inferInstanceAs» (α : Sort u) [i : α] : α := i
 
@@ -3282,7 +3261,7 @@ Version of `Array.get!Internal` that does not increment the reference count of i
 This is only intended for direct use by the compiler.
 -/
 @[extern "lean_array_get_borrowed"]
-unsafe opaque Array.get!InternalBorrowed {α : Type u} [@&Inhabited α] (a : @& Array α) (i : @& Nat) : α
+unsafe opaque Array.get!InternalBorrowed {α : Type u} [Inhabited α] (a : @& Array α) (i : @& Nat) : α
 
 /--
 Use the indexing notation `a[i]!` instead.
@@ -3290,7 +3269,7 @@ Use the indexing notation `a[i]!` instead.
 Access an element from an array, or panic if the index is out of bounds.
 -/
 @[extern "lean_array_get"]
-def Array.get!Internal {α : Type u} [@&Inhabited α] (a : @& Array α) (i : @& Nat) : α :=
+def Array.get!Internal {α : Type u} [Inhabited α] (a : @& Array α) (i : @& Nat) : α :=
   Array.getD a i default
 
 /--
@@ -3669,8 +3648,8 @@ will prevent the actual monad from being "copied" to the code being specialized.
 When we reimplement the specializer, we may consider copying `inst` if it also
 occurs outside binders or if it is an instance.
 -/
-@[never_extract, extern "lean_panic_fn_borrowed"]
-def panicCore {α : Sort u} [@&Inhabited α] (msg : String) : α := default
+@[never_extract, extern "lean_panic_fn"]
+def panicCore {α : Sort u} [Inhabited α] (msg : String) : α := default
 
 /--
 `(panic "msg" : α)` has a built-in implementation which prints `msg` to
@@ -3688,7 +3667,7 @@ def panic {α : Sort u} [Inhabited α] (msg : String) : α :=
   panicCore msg
 
 -- TODO: this be applied directly to `Inhabited`'s definition when we remove the above workaround
-attribute [weak_specialize] Inhabited
+attribute [nospecialize] Inhabited
 
 /--
 The `>>=` operator is overloaded via instances of `bind`.
@@ -4103,7 +4082,7 @@ Actions in the resulting monad are functions that take the local value as a para
 ordinary actions in `m`.
 -/
 def ReaderT (ρ : Type u) (m : Type u → Type v) (α : Type u) : Type (max u v) :=
-  (a : @&ρ) → m α
+  ρ → m α
 
 /--
 Interpret `ρ → m α` as an element of `ReaderT ρ m α`.

src/Init/Tactics.lean

@@ -2259,6 +2259,42 @@ with grind
 ```
 This is more convenient than the equivalent `· by rename_i _ acc _; exact I1 acc`.
 
+### Witnesses
+
+When a specification has a parameter whose type is tagged with `@[mvcgen_witness_type]`, `mvcgen`
+classifies the corresponding goal as a *witness* rather than a verification condition.
+Witnesses are concrete values that the user must provide (inspired by zero-knowledge proofs),
+as opposed to invariants (predicates maintained across loop iterations) or verification conditions
+(propositions to prove).
+
+Witness goals are labelled `witness1`, `witness2`, etc. and can be provided in a `witnesses` section
+that appears before the `invariants` section:
+```
+mvcgen [...] witnesses
+· W1
+· W2
+invariants
+· I1
+with grind
+```
+Like invariants, witnesses support case label syntax:
+```
+mvcgen [...] witnesses
+| witness1 => W1
+```
+
+See the `@[mvcgen_witness_type]` attribute for how to register custom witness types.
+
+### Invariant and witness type attributes
+
+The `@[mvcgen_invariant_type]` and `@[mvcgen_witness_type]` tag attributes control how `mvcgen`
+classifies subgoals:
+* A goal whose type is an application of a type tagged with `@[mvcgen_invariant_type]` is classified
+  as an invariant (`inv<n>`).
+* A goal whose type is an application of a type tagged with `@[mvcgen_witness_type]` is classified
+  as a witness (`witness<n>`).
+* All other goals are classified as verification conditions (`vc<n>`).
+
 ### Invariant suggestions
 
 `mvcgen` will suggest invariants for you if you use the `invariants?` keyword.

src/Lean/Attributes.lean

@@ -186,11 +186,11 @@ def registerTagAttribute (name : Name) (descr : String)
     mkInitial       := pure {}
     addImportedFn   := fun _ _ => pure {}
     addEntryFn      := fun (s : NameSet) n => s.insert n
-    exportEntriesFnEx := fun env es =>
-      let all : Array Name := es.foldl (fun a e => a.push e) #[] |>.qsort Name.quickLt
-      -- Do not export info for private defs at exported/server levels
-      let exported := all.filter ((env.setExporting true).contains (skipRealize := false))
-      { exported, server := exported, «private» := all }
+    exportEntriesFnEx := fun env es _ =>
+      let r : Array Name := es.foldl (fun a e => a.push e) #[]
+      -- Do not export info for private defs
+      let r := r.filter (env.contains (skipRealize := false))
+      r.qsort Name.quickLt
     statsFn         := fun s => "tag attribute" ++ Format.line ++ "number of local entries: " ++ format s.size
     asyncMode       := asyncMode
     replay?         := some fun _ newState newConsts s =>
@@ -266,14 +266,15 @@ def registerParametricAttribute (impl : ParametricAttributeImpl α) : IO (Parame
     mkInitial       := pure ([], {})
     addImportedFn   := fun _ => pure ([], {})
     addEntryFn      := fun (decls, m) (p : Name × α) => (p.1 :: decls, m.insert p.1 p.2)
-    exportEntriesFnEx := fun env (decls, m) => Id.run do
-      let all := if impl.preserveOrder then
+    exportEntriesFnEx := fun env (decls, m) lvl => Id.run do
+      let mut r := if impl.preserveOrder then
         decls.toArray.reverse.filterMap (fun n => return (n, ← m.find? n))
       else
         let r := m.foldl (fun a n p => a.push (n, p)) #[]
         r.qsort (fun a b => Name.quickLt a.1 b.1)
-      let exported := all.filter (fun ⟨n, a⟩ => impl.filterExport env n a)
-      { exported, server := exported, «private» := all }
+      if lvl != .private then
+        r := r.filter (fun ⟨n, a⟩ => impl.filterExport env n a)
+      r
     statsFn         := fun (_, m) => "parametric attribute" ++ Format.line ++ "number of local entries: " ++ format m.size
   }
   let attrImpl : AttributeImpl := {
@@ -332,11 +333,11 @@ def registerEnumAttributes (attrDescrs : List (Name × String × α))
     mkInitial       := pure {}
     addImportedFn   := fun _ _ => pure {}
     addEntryFn      := fun (s : NameMap α) (p : Name × α) => s.insert p.1 p.2
-    exportEntriesFnEx := fun env m =>
-      let all : Array (Name × α) := m.foldl (fun a n p => a.push (n, p)) #[] |>.qsort (fun a b => Name.quickLt a.1 b.1)
-      -- Do not export info for private defs at exported/server levels
-      let exported := all.filter ((env.setExporting true).contains (skipRealize := false) ·.1)
-      { exported, server := exported, «private» := all }
+    exportEntriesFnEx := fun env m _ =>
+      let r : Array (Name × α) := m.foldl (fun a n p => a.push (n, p)) #[]
+      -- Do not export info for private defs
+      let r := r.filter (env.contains (skipRealize := false) ·.1)
+      r.qsort (fun a b => Name.quickLt a.1 b.1)
     statsFn         := fun s => "enumeration attribute extension" ++ Format.line ++ "number of local entries: " ++ format s.size
     -- We assume (and check in `modifyState`) that, if used asynchronously, enum attributes are set
     -- only in the same context in which the tagged declaration was created

src/Lean/Compiler/ExternAttr.lean

@@ -55,6 +55,11 @@ private def syntaxToExternAttrData (stx : Syntax) : AttrM ExternAttrData := do
       entries := entries.push <| ExternEntry.inline backend str
   return { entries := entries.toList }
 
+-- Forward declaration
+set_option compiler.ignoreBorrowAnnotation true in
+@[extern "lean_add_extern"]
+opaque addExtern (declName : Name) (externAttrData : ExternAttrData) : CoreM Unit
+
 builtin_initialize externAttr : ParametricAttribute ExternAttrData ←
   registerParametricAttribute {
     name := `extern
@@ -66,7 +71,7 @@ builtin_initialize externAttr : ParametricAttribute ExternAttrData ←
         if let some (.thmInfo ..) := env.find? declName then
           -- We should not mark theorems as extern
           return ()
-        compileDecls #[declName]
+        addExtern declName externAttrData
   }
 
 def getExternAttrData? (env : Environment) (n : Name) : Option ExternAttrData :=

src/Lean/Compiler/IR.lean

@@ -6,6 +6,7 @@ Authors: Leonardo de Moura
 module
 
 prelude
+public import Lean.Compiler.IR.AddExtern
 public import Lean.Compiler.IR.Basic
 public import Lean.Compiler.IR.Format
 public import Lean.Compiler.IR.CompilerM

src/Lean/Compiler/IR/AddExtern.lean

@@ -0,0 +1,85 @@
+/-
+Copyright (c) 2025 Lean FRO LLC. All rights reserved.
+Released under Apache 2.0 license as described in the file LICENSE.
+Authors: Cameron Zwarich
+-/
+
+module
+
+prelude
+import Init.While
+import Lean.Compiler.IR.ToIR
+import Lean.Compiler.LCNF.ToImpureType
+import Lean.Compiler.LCNF.ToImpure
+import Lean.Compiler.LCNF.ExplicitBoxing
+import Lean.Compiler.LCNF.Internalize
+public import Lean.Compiler.ExternAttr
+import Lean.Compiler.LCNF.ExplicitRC
+import Lean.Compiler.Options
+
+public section
+
+namespace Lean.IR
+
+@[export lean_add_extern]
+def addExtern (declName : Name) (externAttrData : ExternAttrData) : CoreM Unit := do
+  if !isPrivateName declName then
+    modifyEnv (Compiler.LCNF.setDeclPublic · declName)
+  let monoDecl ← addMono declName
+  let impureDecls ← addImpure monoDecl
+  addIr impureDecls
+where
+  addMono (declName : Name) : CoreM (Compiler.LCNF.Decl .pure) := do
+    let type ← Compiler.LCNF.getOtherDeclMonoType declName
+    let mut typeIter := type
+    let mut params := #[]
+    let ignoreBorrow := Compiler.compiler.ignoreBorrowAnnotation.get (← getOptions)
+    repeat
+      let .forallE binderName ty b _ := typeIter | break
+      let borrow := !ignoreBorrow && isMarkedBorrowed ty
+      params := params.push {
+        fvarId := (← mkFreshFVarId)
+        type := ty,
+        binderName,
+        borrow
+      }
+      typeIter := b
+    let decl := {
+      name := declName,
+      levelParams := [],
+      value := .extern externAttrData,
+      inlineAttr? := some .noinline,
+      type,
+      params,
+    }
+    decl.saveMono
+    return decl
+
+  addImpure (decl : Compiler.LCNF.Decl .pure) : CoreM (Array (Compiler.LCNF.Decl .impure)) := do
+    let type ← Compiler.LCNF.lowerResultType decl.type decl.params.size
+    let params ← decl.params.mapM fun param =>
+      return { param with type := ← Compiler.LCNF.toImpureType param.type }
+    let decl : Compiler.LCNF.Decl .impure := {
+      name := decl.name,
+      levelParams := decl.levelParams,
+      value := .extern externAttrData
+      inlineAttr? := some .noinline,
+      type,
+      params
+    }
+    Compiler.LCNF.CompilerM.run (phase := .impure) do
+      let decl ← decl.internalize
+      decl.saveImpure
+      let decls ← Compiler.LCNF.addBoxedVersions #[decl]
+      let decls ← Compiler.LCNF.runExplicitRc decls
+      for decl in decls do
+        decl.saveImpure
+        modifyEnv fun env => Compiler.LCNF.recordFinalImpureDecl env decl.name
+      return decls
+
+  addIr (decls : Array (Compiler.LCNF.Decl .impure)) : CoreM Unit := do
+    let decls ← toIR decls
+    logDecls `result decls
+    addDecls decls
+
+end Lean.IR

src/Lean/Compiler/IR/CompilerM.lean

@@ -10,7 +10,6 @@ public import Lean.Compiler.IR.Format
 public import Lean.Compiler.ExportAttr
 public import Lean.Compiler.LCNF.PublicDeclsExt
 import Lean.Compiler.InitAttr
-import all Lean.Compiler.ModPkgExt
 import Init.Data.Format.Macro
 import Lean.Compiler.LCNF.Basic
 
@@ -86,11 +85,11 @@ builtin_initialize declMapExt : SimplePersistentEnvExtension Decl DeclMap ←
     addEntryFn    := fun s d => s.insert d.name d
     -- Store `meta` closure only in `.olean`, turn all other decls into opaque externs.
     -- Leave storing the remainder for `meta import` and server `#eval` to `exportIREntries` below.
-    exportEntriesFnEx? := some fun env s entries =>
+    exportEntriesFnEx? := some fun env s entries _ =>
       let decls := entries.foldl (init := #[]) fun decls decl => decls.push decl
       let entries := sortDecls decls
       -- Do not save all IR even in .olean.private as it will be in .ir anyway
-      .uniform <| if env.header.isModule then
+      if env.header.isModule then
         entries.filterMap fun d => do
           if isDeclMeta env d.name then
             return d
@@ -126,18 +125,12 @@ private def exportIREntries (env : Environment) : Array (Name × Array EnvExtens
   -- save all initializers independent of meta/private. Non-meta initializers will only be used when
   -- .ir is actually loaded, and private ones iff visible.
   let initDecls : Array (Name × Name) :=
-    (regularInitAttr.ext.exportEntriesFn env (regularInitAttr.ext.getState env)).private
+    regularInitAttr.ext.exportEntriesFn env (regularInitAttr.ext.getState env) .private
   -- safety: cast to erased type
   let initDecls : Array EnvExtensionEntry := unsafe unsafeCast initDecls
 
-  -- needed during initialization via interpreter
-  let modPkg : Array (Option PkgId) := (modPkgExt.exportEntriesFn env (modPkgExt.getState env)).private
-  -- safety: cast to erased type
-  let modPkg : Array EnvExtensionEntry := unsafe unsafeCast modPkg
-
   #[(declMapExt.name, irEntries),
-    (Lean.regularInitAttr.ext.name, initDecls),
-    (modPkgExt.name, modPkg)]
+    (Lean.regularInitAttr.ext.name, initDecls)]
 
 def findEnvDecl (env : Environment) (declName : Name) : Option Decl :=
   Compiler.LCNF.findExtEntry? env declMapExt declName findAtSorted? (·.2.find?)

src/Lean/Compiler/LCNF/Basic.lean

@@ -342,11 +342,6 @@ def LetValue.toExpr (e : LetValue pu) : Expr :=
   | .unbox var _ => mkApp (.const `unbox []) (.fvar var)
   | .isShared fvarId _ => mkApp (.const `isShared []) (.fvar fvarId)
 
-def LetValue.isPersistent (val : LetValue .impure) : Bool :=
-  match val with
-  | .fap _ xs => xs.isEmpty -- all global constants are persistent
-  | _ => false
-
 structure LetDecl (pu : Purity) where
   fvarId : FVarId
   binderName : Name
@@ -1230,14 +1225,7 @@ def instantiateRevRangeArgs (e : Expr) (beginIdx endIdx : Nat) (args : Array (Ar
   else
     e.instantiateRevRange beginIdx endIdx (args.map (·.toExpr))
 
-/--
-Lookup function for compiler extensions with sorted persisted state that works in both `lean` and
-`leanir`.
-
-`preferImported` defaults to false because in `leanir`, we do not want to mix information from
-`meta` compilation in `lean` with our own state. But in `lean`, setting `preferImported` can help
-with avoiding unnecessary task blocks.
--/
+/-- Lookup function for compiler extensions with sorted persisted state that works in both `lean` and `leanir`. -/
 @[inline] def findExtEntry? [Inhabited σ] (env : Environment) (ext : PersistentEnvExtension α β σ) (declName : Name)
     (findAtSorted? : Array α → Name → Option α')
     (findInState? : σ → Name → Option α') : Option α' :=

src/Lean/Compiler/LCNF/Check.lean

@@ -232,7 +232,6 @@ partial def checkCases (c : Cases .pure) : CheckM Unit := do
       withParams params do check k
 
 partial def check (code : Code .pure) : CheckM Unit := do
-  checkSystem "LCNF check"
   match code with
   | .let decl k => checkLetDecl decl; withFVarId decl.fvarId do check k
   | .fun decl k =>

src/Lean/Compiler/LCNF/CoalesceRC.lean

@@ -1,104 +0,0 @@
-/-
-Copyright (c) 2026 Lean FRO, LLC. All rights reserved.
-Released under Apache 2.0 license as described in the file LICENSE.
-Authors: Henrik Böving
--/
-module
-
-prelude
-public import Lean.Compiler.LCNF.CompilerM
-public import Lean.Compiler.LCNF.PassManager
-
-namespace Lean.Compiler.LCNF
-
-/-!
-# Coalesce Reference Counting Operations
-
-This pass coalesces multiple `inc`/`dec` operations on the same variable within a basic block.
-Within a basic block, it is always safe to:
-- Move all increments on a variable to the first `inc` location (summing the counts). Because if
-  there are later `inc`s no intermediate operation can observe RC=1 (as the value must stay alive
-  until the later inc) and thus doing all relevant `inc` in the beginning doesn't change
-  semantics.
-- Move all decrements on a variable to the last `dec` location (summing the counts). Because the
-  value is guaranteed to stay alive until at least the last `dec` anyway so a similar argument to
-  `inc` holds.
-
-Crucially this pass must be placed after `expandResetReuse` as that one relies on `inc`s still being
-present in their original location for optimization purposes.
--/
-
-private structure State where
-  /-- Total inc count per variable in the current basic block (accumulated going forward). -/
-  incTotal : Std.HashMap FVarId Nat := {}
-  /-- Total dec count per variable in the current basic block (accumulated going forward). -/
-  decTotal : Std.HashMap FVarId Nat := {}
-  /--
-  Inc count seen so far per variable going backward. When this equals `incTotal`, we've
-  reached the first inc and should emit the coalesced operation.
-  -/
-  incAccum : Std.HashMap FVarId Nat := {}
-  /--
-  Whether we've already emitted the coalesced dec for a variable (going backward, the first
-  dec encountered is the last in the block).
-  -/
-  decPlaced : Std.HashSet FVarId := {}
-
-private abbrev M := StateRefT State CompilerM
-
-/--
-Coalesce inc/dec operations within individual basic blocks.
--/
-partial def Code.coalesceRC (code : Code .impure) : CompilerM (Code .impure) := do
-  go code |>.run' {}
-where
-  go (code : Code .impure) : M (Code .impure) := do
-    match code with
-    | .inc fvarId n check persistent k _ =>
-      modify fun s => { s with incTotal := s.incTotal.alter fvarId (fun v? => some ((v?.getD 0) + n)) }
-      let k ← go k
-      modify fun s => { s with incAccum := s.incAccum.alter fvarId (fun v? => some ((v?.getD 0) + n)) }
-      let s ← get
-      if s.incAccum[fvarId]! == s.incTotal[fvarId]! then
-        return .inc fvarId s.incTotal[fvarId]! check persistent k
-      else
-        return k
-    | .dec fvarId n check persistent k _ =>
-      modify fun s => { s with decTotal := s.decTotal.alter fvarId (fun v? => some ((v?.getD 0) + n)) }
-      let k ← go k
-      let s ← get
-      if !s.decPlaced.contains fvarId then
-        modify fun s => { s with decPlaced := s.decPlaced.insert fvarId }
-        return .dec fvarId s.decTotal[fvarId]! check persistent k
-      else
-        return k
-    | .let _ k =>
-      let k ← go k
-      return code.updateCont! k
-    | .jp decl k =>
-      let value ← decl.value.coalesceRC
-      let decl ← decl.updateValue value
-      let k ← go k
-      return code.updateFun! decl k
-    | .cases c =>
-      let alts ← c.alts.mapMonoM (·.mapCodeM (·.coalesceRC))
-      return code.updateAlts! alts
-    | .del _ k _ =>
-      let k ← go k
-      return code.updateCont! k
-    | .oset (k := k) .. | .uset (k := k) .. | .sset (k := k) .. | .setTag (k := k) .. =>
-      let k ← go k
-      return code.updateCont! k
-    | .return .. | .jmp .. | .unreach .. => return code
-
-def Decl.coalesceRC (decl : Decl .impure) : CompilerM (Decl .impure) := do
-  let value ← decl.value.mapCodeM Code.coalesceRC
-  return { decl with value }
-
-public def coalesceRC : Pass :=
-  .mkPerDeclaration `coalesceRc .impure Decl.coalesceRC
-
-builtin_initialize
-  registerTraceClass `Compiler.coalesceRc (inherited := true)
-
-end Lean.Compiler.LCNF

src/Lean/Compiler/LCNF/ElimDeadBranches.lean

@@ -291,9 +291,10 @@ builtin_initialize functionSummariesExt : SimplePersistentEnvExtension (Name ×
   registerSimplePersistentEnvExtension {
     addImportedFn := fun _ => {}
     addEntryFn := fun s ⟨e, n⟩ => s.insert e n
-    exportEntriesFnEx? := some fun _ s _ =>
+    exportEntriesFnEx? := some fun _ s _ => fun
       -- preserved for non-modules, make non-persistent at some point?
-      { exported := #[], server := #[], «private» := s.toArray.qsort decLt }
+      | .private => s.toArray.qsort decLt
+      | _ => #[]
     asyncMode := .sync  -- compilation is non-parallel anyway
     replay? := some <| SimplePersistentEnvExtension.replayOfFilter (!·.contains ·.1) (fun s ⟨e, n⟩ => s.insert e n)
   }

src/Lean/Compiler/LCNF/ExpandResetReuse.lean

@@ -69,8 +69,8 @@ open ImpureType
 abbrev Mask := Array (Option FVarId)
 
 /--
-Try to erase `inc` instructions on projections of `targetId` occurring in the tail of `ds`.
-Return the updated `ds` and mask containing the `FVarId`s whose `inc` was removed.
+Try to erase `inc` instructions on projections of `targetId` occuring in the tail of `ds`.
+Return the updated `ds` and mask contianing the `FVarId`s whose `inc` was removed.
 -/
 partial def eraseProjIncFor (nFields : Nat) (targetId : FVarId) (ds : Array (CodeDecl .impure)) :
     CompilerM (Array (CodeDecl .impure) × Mask) := do

src/Lean/Compiler/LCNF/ExplicitRC.lean

@@ -31,12 +31,9 @@ namespace Lean.Compiler.LCNF
 open ImpureType
 
 /-!
-The following section contains the derived value analysis. It figures out a dependency graph of
+The following section contains the derived value analysis. It figures out a dependency tree of
 values that were derived from other values through projections or `Array` accesses. This information
 is later used in the derived borrow analysis to reduce reference counting pressure.
-
-When a derived value has more than one parent, it is derived from one of the parent values but we
-cannot statically determine which one.
 -/
 
 /--
@@ -44,10 +41,10 @@ Contains information about values derived through various forms of projection fr
 -/
 structure DerivedValInfo where
   /--
-  The set of variables this value may derive from. This is always set except for parameters as they
-  have no value to be derived from.
+  The variable this value was derived from. This is always set except for parameters as they have no
+  value to be derived from.
   -/
-  parents : Array FVarId
+  parent? : Option FVarId
   /--
   The set of variables that were derived from this value.
   -/
@@ -59,85 +56,58 @@ abbrev DerivedValMap := Std.HashMap FVarId DerivedValInfo
 namespace CollectDerivedValInfo
 
 structure State where
-  /--
-  The dependency graph of values.
-  -/
   varMap : DerivedValMap := {}
-  /--
-  The set of values that are to be interpreted as being borrowed by nature. This currently includes:
-  - borrowed parameters
-  - variables that are initialized from constants
-  -/
-  borrowedValues : FVarIdHashSet := {}
+  borrowedParams : FVarIdHashSet := {}
 
 abbrev M := StateRefT State CompilerM
 
 @[inline]
-def addDerivedValue (parents : Array FVarId) (child : FVarId) : M Unit := do
+def visitParam (p : Param .impure) : M Unit :=
   modify fun s => { s with
-    varMap :=
-      let varMap := parents.foldl (init := s.varMap)
-        (·.modify · (fun info => { info with children := info.children.insert child }))
-      varMap.insert child { parents := parents, children := {} }
+    varMap := s.varMap.insert p.fvarId {
+      parent? := none
+      children := {}
+    }
+    borrowedParams :=
+      if p.borrow && p.type.isPossibleRef then
+        s.borrowedParams.insert p.fvarId
+      else
+        s.borrowedParams
   }
 
 @[inline]
-def addBorrowedValue (fvarId : FVarId) : M Unit := do
-  modify fun s => { s with borrowedValues := s.borrowedValues.insert fvarId }
+def addDerivedValue (parent : FVarId) (child : FVarId) : M Unit := do
+  modify fun s => { s with
+    varMap :=
+      s.varMap
+        |>.modify parent (fun info => { info with children := info.children.insert child })
+        |>.insert child { parent? := some parent, children := {} }
+  }
 
-def addDerivedLetValue (parents : Array FVarId) (child : FVarId) : M Unit := do
-  let type ← getType child
-  if !type.isPossibleRef then
-    return ()
-  let parents ← parents.filterM fun fvarId => do
-    let type ← getType fvarId
-    return type.isPossibleRef
-  addDerivedValue parents child
-  if parents.isEmpty then
-      addBorrowedValue child
-
-@[inline]
-def visitParam (p : Param .impure) : M Unit := do
-  addDerivedValue #[] p.fvarId
-  if p.borrow && p.type.isPossibleRef then
-    addBorrowedValue p.fvarId
-
-def removeFromParents (child : FVarId) : M Unit := do
-  if let some entry := (← get).varMap.get? child then
-    for parent in entry.parents do
-      modify fun s => { s with
-        varMap := s.varMap.modify parent fun info =>
-          { info with children := info.children.erase child }
-      }
+def removeFromParent (child : FVarId) : M Unit := do
+  if let some parent := (← get).varMap.get? child |>.bind (·.parent?) then
+    modify fun s => { s with
+      varMap := s.varMap.modify parent fun info =>
+        { info with children := info.children.erase child }
+    }
 
 partial def collectCode (code : Code .impure) : M Unit := do
   match code with
   | .let decl k =>
     match decl.value with
     | .oproj _ parent =>
-      addDerivedLetValue #[parent] decl.fvarId
-    -- Keep in sync with PropagateBorrow, InferBorrow
+      addDerivedValue parent decl.fvarId
     | .fap ``Array.getInternal args =>
       if let .fvar parent := args[1]! then
-        addDerivedLetValue #[parent] decl.fvarId
+        addDerivedValue parent decl.fvarId
     | .fap ``Array.get!Internal args =>
-      let mut parents := #[]
-      /-
-      Because execution may continue after a panic, the value resulting from a get!InternalBorrowed
-      may be derived from either the `Inhabited` instance or the `Array` argument.
-      -/
-      if let .fvar parent := args[1]! then
-        parents := parents.push parent
       if let .fvar parent := args[2]! then
-        parents := parents.push parent
-      addDerivedLetValue parents decl.fvarId
+        addDerivedValue parent decl.fvarId
     | .fap ``Array.uget args =>
       if let .fvar parent := args[1]! then
-        addDerivedLetValue #[parent] decl.fvarId
-    | .fap _ #[] =>
-      addDerivedLetValue #[] decl.fvarId
+        addDerivedValue parent decl.fvarId
     | .reset _ target =>
-      removeFromParents target
+      removeFromParent target
     | _ => pure ()
     collectCode k
   | .jp decl k =>
@@ -154,8 +124,8 @@ Collect the derived value tree as well as the set of parameters that take object
 -/
 def collect (ps : Array (Param .impure)) (code : Code .impure) :
     CompilerM (DerivedValMap × FVarIdHashSet) := do
-  let ⟨_, { varMap, borrowedValues }⟩ ← go |>.run {}
-  return ⟨varMap, borrowedValues⟩
+  let ⟨_, { varMap, borrowedParams }⟩ ← go |>.run {}
+  return ⟨varMap, borrowedParams⟩
 where
   go : M Unit := do
     ps.forM visitParam
@@ -199,21 +169,13 @@ def LiveVars.erase (liveVars : LiveVars) (fvarId : FVarId) : LiveVars :=
   let borrows := liveVars.borrows.erase fvarId
   { vars, borrows }
 
-@[inline]
-def LiveVars.insertBorrow (liveVars : LiveVars) (fvarId : FVarId) : LiveVars :=
-  { liveVars with borrows := liveVars.borrows.insert fvarId }
-
-@[inline]
-def LiveVars.insertLive (liveVars : LiveVars) (fvarId : FVarId) : LiveVars :=
-  { liveVars with vars := liveVars.vars.insert fvarId }
-
 abbrev JPLiveVarMap := FVarIdMap LiveVars
 
 structure Context where
   /--
-  The set of all values that are borrowed and potentially objects
+  The set of all parameters that are borrowed and take potential objects as arguments.
   -/
-  borrowedValues : FVarIdHashSet
+  borrowedParams : FVarIdHashSet
   /--
   The derived value tree.
   -/
@@ -272,6 +234,11 @@ def withParams (ps : Array (Param .impure)) (x : RcM α) : RcM α := do
       { ctx with idx := ctx.idx + 1, varMap }
   withReader update x
 
+def LetValue.isPersistent (val : LetValue .impure) : Bool :=
+  match val with
+  | .fap _ xs => xs.isEmpty -- all global constants are persistent
+  | _ => false
+
 @[inline]
 def withLetDecl (decl : LetDecl .impure) (x : RcM α) : RcM α := do
   let update := fun ctx =>
@@ -314,21 +281,18 @@ def withCollectLiveVars (x : RcM α) : RcM (α × LiveVars) := do
   return (ret, collected)
 
 /--
-Traverse the transitive closure of values derived from `fvarId` and add them to `s` if:
-- they pass `shouldAdd`.
-- all their parents are accessible
+Traverse the transitive closure of values derived from `fvarId` and add them to `s` if they pass
+`shouldAdd`.
 -/
 @[specialize]
-partial def addDescendants (fvarId : FVarId) (derivedValMap : DerivedValMap) (liveVars : LiveVars)
-    (shouldAdd : FVarId → Bool := fun _ => true) : LiveVars :=
+partial def addDescendants (fvarId : FVarId) (derivedValMap : DerivedValMap) (s : FVarIdHashSet)
+    (shouldAdd : FVarId → Bool := fun _ => true) : FVarIdHashSet :=
   if let some info := derivedValMap.get? fvarId then
-    info.children.fold (init := liveVars) fun liveVars child =>
-      let cinfo := derivedValMap.get! child
-      let parentsOk := cinfo.parents.all fun fvarId => (liveVars.vars.contains fvarId || liveVars.borrows.contains fvarId)
-      let liveVars := if parentsOk && shouldAdd child then liveVars.insertBorrow child else liveVars
-      addDescendants child derivedValMap liveVars shouldAdd
+    info.children.fold (init := s) fun s child =>
+      let s := if shouldAdd child then s.insert child else s
+      addDescendants child derivedValMap s shouldAdd
   else
-    liveVars
+    s
 
 /--
 Mark `fvarId` as live from here on out and if there are any derived values that are not live anymore
@@ -339,21 +303,20 @@ alive after all).
 def useVar (fvarId : FVarId) (shouldBorrow : FVarId → Bool := fun _ => true) : RcM Unit := do
   if !(← isLive fvarId) then
     let derivedValMap := (← read).derivedValMap
-    modifyLive fun liveVars => { liveVars with vars := liveVars.vars.insert fvarId }
     modifyLive fun liveVars =>
-      addDescendants fvarId derivedValMap liveVars fun y =>
-        !liveVars.vars.contains y && shouldBorrow y
+      { liveVars with
+          borrows := addDescendants fvarId derivedValMap liveVars.borrows fun y =>
+            !liveVars.vars.contains y && shouldBorrow y
+          vars := liveVars.vars.insert fvarId
+      }
 
 def useArgs (args : Array (Arg .impure)) : RcM Unit := do
   args.forM fun arg =>
     match arg with
     | .fvar fvarId =>
       useVar fvarId fun y =>
-        /-
-        If we are in a situation like `f x y` where `x` would imply that `y` remains borrowed we are
-        going to mark `y` as being live instead of borrowed later on anyways. Instead we skip this
-        intermediate state and don't even begin to consider it as borrowed.
-        -/
+        -- If a value is used as an argument we are going to mark it live anyways so don't mark it
+        -- as borrowed.
         args.all fun arg =>
           match arg with
           | .fvar z => y != z
@@ -382,9 +345,9 @@ def setRetLiveVars : RcM Unit := do
   let derivedValMap := (← read).derivedValMap
   -- At the end of a function no values are live and all borrows derived from parameters will still
   -- be around.
-  let liveVars := (← read).borrowedValues.fold (init := {}) fun liveVars x =>
-    addDescendants x derivedValMap (liveVars.insertBorrow x)
-  modifyLive (fun _ => liveVars)
+  let borrows := (← read).borrowedParams.fold (init := {}) fun borrows x =>
+    addDescendants x derivedValMap (borrows.insert x)
+  modifyLive fun _ => { vars := {}, borrows }
 
 @[inline]
 def addInc (fvarId : FVarId) (k : Code .impure) (n : Nat := 1) : RcM (Code .impure) := do
@@ -666,9 +629,9 @@ partial def Code.explicitRc (code : Code .impure) : RcM (Code .impure) := do
 def Decl.explicitRc (decl : Decl .impure) :
     CompilerM (Decl .impure) := do
   let value ← decl.value.mapCodeM fun code => do
-    let ⟨derivedValMap, borrowedValues⟩ ← CollectDerivedValInfo.collect decl.params code
+    let ⟨derivedValMap, borrowedParams⟩ ← CollectDerivedValInfo.collect decl.params code
     go code |>.run {
-      borrowedValues,
+      borrowedParams,
       derivedValMap,
     } |>.run' {}
   return { decl with value }

src/Lean/Compiler/LCNF/InferBorrow.lean

@@ -213,8 +213,6 @@ inductive OwnReason where
   | jpArgPropagation (jpFVar : FVarId)
   /-- Tail call preservation at a join point jump. -/
   | jpTailCallPreservation (jpFVar : FVarId)
-  /-- Annotated as an owned parameter (currently only triggerable through `@[export]`)-/
-  | ownedAnnotation
 
 def OwnReason.toString (reason : OwnReason) : CompilerM String := do
   PP.run do
@@ -231,7 +229,6 @@ def OwnReason.toString (reason : OwnReason) : CompilerM String := do
     | .tailCallPreservation funcName => return s!"tail call preservation of {funcName}"
     | .jpArgPropagation jpFVar => return s!"backward propagation from JP {← PP.ppFVar jpFVar}"
     | .jpTailCallPreservation jpFVar => return s!"JP tail call preservation {← PP.ppFVar jpFVar}"
-    | .ownedAnnotation => return s!"Annotated as owned"
 
 /--
 Determine whether an `OwnReason` is necessary for correctness (forced) or just an optimization
@@ -243,19 +240,13 @@ def OwnReason.isForced (reason : OwnReason) : Bool :=
   -- All of these reasons propagate through ABI decisions and can thus safely be ignored as they
   -- will be accounted for by the reference counting pass.
   | .constructorArg .. | .functionCallArg .. | .fvarCall .. | .partialApplication ..
-  | .jpArgPropagation ..
-  -- forward propagation can never affect a user-annotated parameter
-  | .forwardProjectionProp ..
-  -- backward propagation on a user-annotated parameter is only necessary if the projected value
-  -- directly flows into a reset-reuse. However, the borrow annotation propagator ensures this
-  -- situation never arises
-  | .backwardProjectionProp .. => false
+  | .jpArgPropagation .. => false
   -- Results of functions and constructors are naturally owned.
   | .constructorResult .. | .functionCallResult ..
   -- We cannot pass borrowed values to reset or have borrow annotations destroy tail calls for
   -- correctness reasons.
   | .resetReuse .. | .tailCallPreservation .. | .jpTailCallPreservation ..
-  | .ownedAnnotation => true
+  | .forwardProjectionProp .. | .backwardProjectionProp .. => true
 
 /--
 Infer the borrowing annotations in a SCC through dataflow analysis.
@@ -265,19 +256,10 @@ partial def infer (decls : Array (Decl .impure)) : CompilerM ParamMap := do
   return map.paramMap
 where
   go : InferM Unit := do
-    for (_, params) in (← get).paramMap.map do
-      for param in params do
-        if !param.borrow && param.type.isPossibleRef then
-          -- if the param already disqualifies as borrow now this is because of an annotation
-          ownFVar param.fvarId .ownedAnnotation
-    modify fun s => { s with modified := false }
-    loop
-
-  loop : InferM Unit := do
     step
     if (← get).modified then
       modify fun s => { s with modified := false }
-      loop
+      go
     else
       return ()
 
@@ -375,31 +357,14 @@ where
     match v with
     | .reset _ x => ownFVar z (.resetReuse z); ownFVar x (.resetReuse z)
     | .reuse x _ _ args => ownFVar z (.resetReuse z); ownFVar x (.resetReuse z); ownArgsIfParam z args
+    | .ctor _ args => ownFVar z (.constructorResult z); ownArgsIfParam z args
     | .oproj _ x _ =>
       if ← isOwned x then ownFVar z (.forwardProjectionProp z)
       if ← isOwned z then ownFVar x (.backwardProjectionProp z)
-    -- Keep in sync with ExplicitRC, PropagateBorrow
-    | .fap ``Array.getInternal args =>
-      if let .fvar parent := args[1]! then
-        if ← isOwned parent then ownFVar z (.forwardProjectionProp z)
-    | .fap ``Array.get!Internal args =>
-      if let .fvar parent := args[1]! then
-        if ← isOwned parent then ownFVar z (.forwardProjectionProp z)
-      if let .fvar parent := args[2]! then
-        if ← isOwned parent then ownFVar z (.forwardProjectionProp z)
-    | .fap ``Array.uget args =>
-      if let .fvar parent := args[1]! then
-        if ← isOwned parent then ownFVar z (.forwardProjectionProp z)
     | .fap f args =>
-      -- Constants remain alive at least until the end of execution and can thus effectively be seen
-      -- as a "borrowed" read.
-      if args.size > 0 then
-        let ps ← getParamInfo (.decl f)
-        ownFVar z (.functionCallResult z)
-        ownArgsUsingParams args ps (.functionCallArg z)
-    | .ctor i args =>
-      if !i.isScalar then
-        ownFVar z (.constructorResult z); ownArgsIfParam z args
+      let ps ← getParamInfo (.decl f)
+      ownFVar z (.functionCallResult z)
+      ownArgsUsingParams args ps (.functionCallArg z)
     | .fvar x args =>
       ownFVar z (.functionCallResult z); ownFVar x (.fvarCall z); ownArgs (.fvarCall z) args
     | .pap _ args => ownFVar z (.functionCallResult z); ownArgs (.partialApplication z) args

src/Lean/Compiler/LCNF/Main.lean

@@ -78,13 +78,9 @@ def isValidMainType (type : Expr) : Bool :=
     isValidResultName resultName
   | _ => false
 
-/-- A postponed call of `compileDecls`. -/
 structure PostponedCompileDecls where
-  /-- Declaration names of this mutual group. -/
   declNames : Array Name
-  /-- Options at time of original call, to be restored for tracing etc. -/
-  options : Options
-deriving BEq
+deriving BEq, Hashable
 
 /--
 Saves postponed `compileDecls` calls.
@@ -100,25 +96,21 @@ builtin_initialize postponedCompileDeclsExt : SimplePersistentEnvExtension Postp
     asyncMode     := .sync
     replay?       := some <| SimplePersistentEnvExtension.replayOfFilter
       (fun s e => !e.declNames.any s.contains) (fun s e => e.declNames.foldl (·.insert · e) s)
-    exportEntriesFnEx? := some fun _ _ es =>
+    exportEntriesFnEx? := some fun _ _ es lvl =>
       -- `leanir` imports the target module privately
-      { exported := #[], server := #[], «private» := es.toArray }
+      if lvl == .private then es.toArray else #[]
   }
 
-def resumeCompilation (declName : Name) (baseOpts : Options) : CoreM Unit := do
+def resumeCompilation (declName : Name) : CoreM Unit := do
   let some decls := postponedCompileDeclsExt.getState (← getEnv) |>.find? declName | return
-  let opts := baseOpts.mergeBy (fun _ base _ => base) decls.options
-  let opts := compiler.postponeCompile.set opts false
   modifyEnv (postponedCompileDeclsExt.modifyState · fun s => decls.declNames.foldl (·.erase) s)
-  -- NOTE: we *must* throw away the current options as they could depend on the specific recursion
-  -- we did to get here.
-  withOptions (fun _ => opts) do
+  withOptions (compiler.postponeCompile.set · false) do
   Core.prependError m!"Failed to compile `{declName}`" do
-    (← compileDeclsRef.get) decls.declNames baseOpts
+    (← compileDeclsRef.get) decls.declNames
 
 namespace PassManager
 
-partial def run (declNames : Array Name) (baseOpts : Options) : CompilerM Unit := withAtLeastMaxRecDepth 8192 do
+partial def run (declNames : Array Name) : CompilerM Unit := withAtLeastMaxRecDepth 8192 do
   /-
   Note: we need to increase the recursion depth because we currently do to save phase1
   declarations in .olean files. Then, we have to recursively compile all dependencies,
@@ -149,14 +141,11 @@ partial def run (declNames : Array Name) (baseOpts : Options) : CompilerM Unit :
 
   -- Now that we have done all input checks, check for postponement
   if (← getEnv).header.isModule && (← compiler.postponeCompile.getM) then
-    modifyEnv (postponedCompileDeclsExt.addEntry · { declNames := decls.map (·.name), options := ← getOptions })
+    modifyEnv (postponedCompileDeclsExt.addEntry · { declNames := decls.map (·.name) })
     -- meta defs are compiled locally so they are available for execution/compilation without
     -- importing `.ir` but still marked for `leanir` compilation so that we do not have to persist
     -- module-local compilation information between the two processes
-    if decls.any (isMarkedMeta (← getEnv) ·.name) then
-      -- avoid re-compiling the meta defs in this process; the entry for `leanir` is not affected
-      modifyEnv (postponedCompileDeclsExt.modifyState · fun s => decls.foldl (·.erase ·.name) s)
-    else
+    if !decls.any (isMarkedMeta (← getEnv) ·.name) then
       trace[Compiler] "postponing compilation of {decls.map (·.name)}"
       return
 
@@ -168,7 +157,7 @@ partial def run (declNames : Array Name) (baseOpts : Options) : CompilerM Unit :
       let .let { value := .const c .., .. } .. := c | return
       -- Need to do some lookups to get the actual name passed to `compileDecls`
       let c := Compiler.getImplementedBy? (← getEnv) c |>.getD c
-      resumeCompilation c baseOpts
+      resumeCompilation c
 
   let decls := markRecDecls decls
   let manager ← getPassManager
@@ -199,7 +188,6 @@ where
     profileitM Exception profilerName (← getOptions) do
       let mut state : (pu : Purity) × Array (Decl pu) := ⟨inPhase, decls⟩
       for pass in passes do
-        checkSystem "LCNF compiler"
         state ← withTraceNode `Compiler (fun _ => return m!"compiler phase: {pass.phase}, pass: {pass.name}") do
           let decls ← withPhase pass.phase do
             state.fst.withAssertPurity pass.phase.toPurity fun h => do
@@ -211,9 +199,9 @@ where
 
 end PassManager
 
-def main (declNames : Array Name) (baseOpts : Options) : CoreM Unit := do
+def main (declNames : Array Name) : CoreM Unit := do
   withTraceNode `Compiler (fun _ => return m!"compiling: {declNames}") do
-    CompilerM.run <| PassManager.run declNames baseOpts
+    CompilerM.run <| PassManager.run declNames
 
 builtin_initialize
   compileDeclsRef.set main

src/Lean/Compiler/LCNF/OtherDecl.lean

@@ -21,6 +21,6 @@ def getOtherDeclType (declName : Name) (us : List Level := []) : CompilerM Expr
   match (← getPhase) with
   | .base => getOtherDeclBaseType declName us
   | .mono => getOtherDeclMonoType declName
-  | .impure => throwError "getOtherDeclType unsupported for impure"
+  | .impure => getOtherDeclImpureType declName
 
 end Lean.Compiler.LCNF

src/Lean/Compiler/LCNF/Passes.lean

@@ -26,7 +26,6 @@ public import Lean.Compiler.LCNF.SimpCase
 public import Lean.Compiler.LCNF.InferBorrow
 public import Lean.Compiler.LCNF.ExplicitBoxing
 public import Lean.Compiler.LCNF.ExplicitRC
-public import Lean.Compiler.LCNF.CoalesceRC
 public import Lean.Compiler.LCNF.Toposort
 public import Lean.Compiler.LCNF.ExpandResetReuse
 public import Lean.Compiler.LCNF.SimpleGroundExpr
@@ -150,7 +149,6 @@ def builtinPassManager : PassManager := {
     explicitBoxing,
     explicitRc,
     expandResetReuse,
-    coalesceRC,
     pushProj (occurrence := 1),
     detectSimpleGround,
     inferVisibility (phase := .impure),

src/Lean/Compiler/LCNF/PhaseExt.lean

@@ -93,15 +93,16 @@ def mkDeclExt (phase : Phase) (name : Name := by exact decl_name%) :
     mkInitial := pure {},
     addImportedFn := fun _ => pure {},
     addEntryFn := fun s decl => s.insert decl.name decl
-    exportEntriesFnEx env s := Id.run do
-      let all := sortedEntries s declLt
-      let exported := all.filterMap fun decl => do
-        guard <| isDeclPublic env decl.name
-        if isDeclTransparent env phase decl.name then
-          some decl
-        else
-          some { decl with value := .extern { entries := [.opaque] } }
-      return { exported, server := exported, «private» := all }
+    exportEntriesFnEx env s level := Id.run do
+      let mut entries := sortedEntries s declLt
+      if level != .private then
+        entries := entries.filterMap fun decl => do
+          guard <| isDeclPublic env decl.name
+          if isDeclTransparent env phase decl.name then
+            some decl
+          else
+            some { decl with value := .extern { entries := [.opaque] } }
+      return entries
     statsFn := statsFn,
     asyncMode := .sync,
     replay? := some (replayFn phase)
@@ -137,12 +138,13 @@ def mkSigDeclExt (phase : Phase) (name : Name := by exact decl_name%) :
     mkInitial := pure {},
     addImportedFn := fun _ => pure {},
     addEntryFn := fun s sig => s.insert sig.name sig
-    exportEntriesFnEx env s := Id.run do
-      let all := sortedEntries s sigLt
-      let exported := all.filterMap fun sig => do
-        guard <| isDeclPublic env sig.name
-        some sig
-      return { exported, server := exported, «private» := all }
+    exportEntriesFnEx env s level := Id.run do
+      let mut entries := sortedEntries s sigLt
+      if level != .private then
+        entries := entries.filterMap fun sig => do
+          guard <| isDeclPublic env sig.name
+          some sig
+      return entries
     statsFn := statsFn,
     asyncMode := .sync,
     replay? := some (replayFn phase)

src/Lean/Compiler/LCNF/PrettyPrinter.lean

@@ -154,18 +154,16 @@ mutual
       return f!"oset {← ppFVar fvarId} [{i}] := {← ppArg y};" ++ .line ++ (← ppCode k)
     | .setTag fvarId cidx k _ =>
       return f!"setTag {← ppFVar fvarId} := {cidx};" ++ .line ++ (← ppCode k)
-    | .inc fvarId n check persistent k _ =>
-      let ann := (if persistent then "[persistent]" else "") ++ (if !check then "[ref]" else "")
+    | .inc fvarId n _ _ k _ =>
       if n != 1 then
-        return f!"inc[{n}]{ann} {← ppFVar fvarId};" ++ .line ++ (← ppCode k)
+        return f!"inc[{n}] {← ppFVar fvarId};" ++ .line ++ (← ppCode k)
       else
-        return f!"inc{ann} {← ppFVar fvarId};" ++ .line ++ (← ppCode k)
-    | .dec fvarId n check persistent k _ =>
-      let ann := (if persistent then "[persistent]" else "") ++ (if !check then "[ref]" else "")
+        return f!"inc {← ppFVar fvarId};" ++ .line ++ (← ppCode k)
+    | .dec fvarId n _ _ k _ =>
       if n != 1 then
-        return f!"dec[{n}]{ann} {← ppFVar fvarId};" ++ .line ++ (← ppCode k)
+        return f!"dec[{n}] {← ppFVar fvarId};" ++ .line ++ (← ppCode k)
       else
-        return f!"dec{ann} {← ppFVar fvarId};" ++ .line ++ (← ppCode k)
+        return f!"dec {← ppFVar fvarId};" ++ .line ++ (← ppCode k)
     | .del fvarId k _ =>
       return f!"del {← ppFVar fvarId};" ++ .line ++ (← ppCode k)
 

src/Lean/Compiler/LCNF/PropagateBorrow.lean

@@ -105,32 +105,10 @@ where
 
   collectLetValue (z : FVarId) (v : LetValue .impure) : InferM Unit := do
     match v with
-    | .oproj _ parent _ =>
-      let parentVal ← getOwnedness parent
-      join z parentVal
-    -- Keep in sync with ExplicitRC, InferBorrow
-    | .fap ``Array.getInternal args =>
-      if let .fvar parent := args[1]! then
-        let parentVal ← getOwnedness parent
-        join z parentVal
-    | .fap ``Array.get!Internal args =>
-      if let .fvar parent := args[1]! then
-        let parentVal ← getOwnedness parent
-        join z parentVal
-      if let .fvar parent := args[2]! then
-        let parentVal ← getOwnedness parent
-        join z parentVal
-    | .fap ``Array.uget args =>
-      if let .fvar parent := args[1]! then
-        let parentVal ← getOwnedness parent
-        join z parentVal
-    | .fap _ args =>
-      let value := if args.isEmpty then .borrow else .own
-      join z value
-    | .ctor i _ =>
-      let value := if i.isScalar then .borrow else .own
-      join z value
-    | .fvar .. | .pap .. | .sproj .. | .uproj .. | .erased .. | .lit .. =>
+    | .oproj _ x _ =>
+      let xVal ← getOwnedness x
+      join z xVal
+    | .ctor .. | .fap .. | .fvar .. | .pap .. | .sproj .. | .uproj .. | .erased .. | .lit .. =>
       join z .own
     | _ => unreachable!
 

src/Lean/Compiler/LCNF/Simp/SimpM.lean

@@ -146,7 +146,7 @@ Similar to the default `Lean.withIncRecDepth`, but include the `inlineStack` in
 @[inline] def withIncRecDepth (x : SimpM α) : SimpM α := do
   let curr ← MonadRecDepth.getRecDepth
   let max  ← MonadRecDepth.getMaxRecDepth
-  if max != 0 && curr == max then
+  if curr == max then
     throwMaxRecDepth
   else
     MonadRecDepth.withRecDepth (curr+1) x

src/Lean/Compiler/LCNF/SimpleGroundExpr.lean

@@ -178,11 +178,10 @@ partial def compileToSimpleGroundExpr (code : Code .impure) : CompilerM (Option
 where
   go (code : Code .impure) : DetectM SimpleGroundExpr := do
     match code with
-    | .let decl (.return fvarId) | .let decl (.inc _ _ _ true  (.return fvarId)) =>
+    | .let decl (.return fvarId) =>
       guard <| decl.fvarId == fvarId
       compileFinalLet decl.value
     | .let decl k => compileNonFinalLet decl k
-    | .inc (persistent := true) (k := k) .. => go k
     | _ => failure
 
   @[inline]

src/Lean/Compiler/LCNF/SpecInfo.lean

@@ -20,10 +20,8 @@ inductive SpecParamInfo where
   /--
   A parameter that is an type class instance (or an arrow that produces a type class instance),
   and is fixed in recursive declarations. By default, Lean always specializes this kind of argument.
-  If the `weak` parameter is set we only specialize for this parameter iff another parameter causes
-  specialization as well.
   -/
-  | fixedInst (weak : Bool)
+  | fixedInst
   /--
   A parameter that is a function and is fixed in recursive declarations. If the user tags a declaration
   with `@[specialize]` without specifying which arguments should be specialized, Lean will specialize
@@ -51,15 +49,14 @@ namespace SpecParamInfo
 
 @[inline]
 def causesSpecialization : SpecParamInfo → Bool
-  | .fixedInst false | .fixedHO | .user => true
-  | .fixedInst true | .fixedNeutral | .other => false
+  | .fixedInst | .fixedHO | .user => true
+  | .fixedNeutral | .other => false
 
 end SpecParamInfo
 
 instance : ToMessageData SpecParamInfo where
   toMessageData
-    | .fixedInst false => "I"
-    | .fixedInst true => "W"
+    | .fixedInst => "I"
     | .fixedHO => "H"
     | .fixedNeutral => "N"
     | .user => "U"
@@ -133,18 +130,6 @@ private def isNoSpecType (env : Environment) (type : Expr) : Bool :=
     else
       false
 
-/--
-Return `true` if `type` is a type tagged with `@[weak_specialize]` or an arrow that produces this kind of type.
--/
-private def isWeakSpecType (env : Environment) (type : Expr) : Bool :=
-  match type with
-  | .forallE _ _ b _ => isWeakSpecType env b
-  | _ =>
-    if let .const declName _ := type.getAppFn then
-      hasWeakSpecializeAttribute env declName
-    else
-      false
-
 /-!
 *Note*: `fixedNeutral` must have forward dependencies.
 
@@ -175,7 +160,7 @@ See comment at `.fixedNeutral`.
 private def hasFwdDeps (decl : Decl .pure) (paramsInfo : Array SpecParamInfo) (j : Nat) : Bool := Id.run do
   let param := decl.params[j]!
   for h : k in (j+1)...decl.params.size do
-    if paramsInfo[k]!.causesSpecialization || paramsInfo[k]! matches .fixedInst .. then
+    if paramsInfo[k]!.causesSpecialization then
       let param' := decl.params[k]
       if param'.type.containsFVar param.fvarId then
         return true
@@ -214,7 +199,7 @@ def computeSpecEntries (decls : Array (Decl .pure)) (autoSpecialize : Name → O
           else if isTypeFormerType param.type then
             pure .fixedNeutral
           else if (← isArrowClass? param.type).isSome then
-            pure (.fixedInst (weak := isWeakSpecType (← getEnv) param.type))
+            pure .fixedInst
           /-
           Recall that if `specArgs? == some #[]`, then user annotated function with `@[specialize]`, but did not
           specify which arguments must be specialized besides instances. In this case, we try to specialize

src/Lean/Compiler/LCNF/Specialize.lean

@@ -31,8 +31,11 @@ builtin_initialize specCacheExt : SimplePersistentEnvExtension CacheEntry Cache
   registerSimplePersistentEnvExtension {
     addEntryFn    := addEntry
     addImportedFn := fun es => (mkStateFromImportedEntries addEntry {} es).switch
-    exportEntriesFnEx? := some fun _ _ entries =>
-      { exported := #[], server := #[], «private» := entries.toArray }
+    exportEntriesFnEx? := some fun _ _ entries level =>
+      if level == .private then
+        entries.toArray
+      else
+        #[]
     asyncMode     := .sync
     replay?       := some <| SimplePersistentEnvExtension.replayOfFilter
       (!·.contains ·.key) addEntry
@@ -206,7 +209,7 @@ def collect (paramsInfo : Array SpecParamInfo) (args : Array (Arg .pure)) :
       match paramInfo with
       | .other =>
         argMask := argMask.push none
-      | .fixedNeutral | .user | .fixedInst .. | .fixedHO =>
+      | .fixedNeutral | .user | .fixedInst | .fixedHO =>
         argMask := argMask.push (some arg)
         Closure.collectArg arg
     return argMask
@@ -254,8 +257,7 @@ def shouldSpecialize (specEntry : SpecEntry) (args : Array (Arg .pure)) : Specia
     match paramInfo with
     | .other => pure ()
     | .fixedNeutral => pure () -- If we want to monomorphize types such as `Array`, we need to change here
-    | .fixedInst true => pure ()  -- weak: don't trigger specialization on its own
-    | .fixedInst false | .user => if ← isGround arg then return true
+    | .fixedInst | .user => if ← isGround arg then return true
     | .fixedHO => if ← hoCheck arg then return true
 
   return false
@@ -507,7 +509,7 @@ def updateLocalSpecParamInfo : SpecializeM Unit := do
   for entry in infos do
     if let some mask := (← get).parentMasks[entry.declName]? then
       let maskInfo info :=
-        mask.zipWith info (f := fun b i => if !b && (i.causesSpecialization || i matches .fixedInst ..) then .other else i)
+        mask.zipWith info (f := fun b i => if !b && i.causesSpecialization then .other else i)
       let entry := { entry with paramsInfo := maskInfo entry.paramsInfo }
       modify fun s => {
         s with

src/Lean/Compiler/LCNF/ToImpureType.lean

@@ -240,4 +240,12 @@ where fillCache := do
       fieldInfo := fields
     }
 
+public def getOtherDeclImpureType (declName : Name) : CoreM Expr := do
+  match (← impureTypeExt.find? declName) with
+  | some type => return type
+  | none =>
+    let type ← toImpureType (← getOtherDeclMonoType declName)
+    monoTypeExt.insert declName type
+    return type
+
 end Lean.Compiler.LCNF

src/Lean/Compiler/LCNF/ToMono.lean

@@ -279,13 +279,13 @@ partial def casesFloatArrayToMono (c : Cases .pure) (_ : c.typeName == ``FloatAr
   let k ← k.toMono
   return .let decl k
 
-/-- Eliminate `cases` for `String`. -/
+/-- Eliminate `cases` for `String. -/
 partial def casesStringToMono (c : Cases .pure) (_ : c.typeName == ``String) : ToMonoM (Code .pure) := do
   assert! c.alts.size == 1
   let .alt _ ps k := c.alts[0]! | unreachable!
   eraseParams ps
   let p := ps[0]!
-  let decl := { fvarId := p.fvarId, binderName := p.binderName, type := anyExpr, value := .const ``String.toByteArray [] #[.fvar c.discr] }
+  let decl := { fvarId := p.fvarId, binderName := p.binderName, type := anyExpr, value := .const ``String.toList [] #[.fvar c.discr] }
   modifyLCtx fun lctx => lctx.addLetDecl decl
   let k ← k.toMono
   return .let decl k

src/Lean/Compiler/Main.lean

@@ -19,7 +19,7 @@ that fulfill the requirements of `shouldGenerateCode`.
 def compile (declNames : Array Name) : CoreM Unit := do profileitM Exception "compiler new" (← getOptions) do
   withOptions (compiler.postponeCompile.set · false) do
   withTraceNode `Compiler (fun _ => return m!"compiling: {declNames}") do
-    LCNF.main declNames {}
+    LCNF.main declNames
 
 builtin_initialize
   registerTraceClass `Compiler

src/Lean/Compiler/MetaAttr.lean

@@ -39,9 +39,11 @@ private builtin_initialize declMetaExt : SimplePersistentEnvExtension Name NameS
     addEntryFn := fun s n => s.insert n
     asyncMode := .sync
     replay? := some <| SimplePersistentEnvExtension.replayOfFilter (!·.contains ·) (·.insert ·)
-    exportEntriesFnEx? := some fun env s entries =>
-      let decls := entries.foldl (init := #[]) fun decls decl => decls.push decl
-      { exported := #[], server := #[], «private» := decls.qsort Name.quickLt }
+    exportEntriesFnEx? := some fun env s entries => fun
+      | .private =>
+        let decls := entries.foldl (init := #[]) fun decls decl => decls.push decl
+        decls.qsort Name.quickLt
+      | _ => #[]
   }
 
 /-- Whether a declaration should be exported for interpretation. -/

src/Lean/Compiler/Specialize.lean

@@ -24,17 +24,6 @@ Marks a definition to never be specialized during code generation.
 builtin_initialize nospecializeAttr : TagAttribute ←
   registerTagAttribute `nospecialize "mark definition to never be specialized"
 
-/--
-Marks a type for weak specialization: Parameters of this type are only specialized when
-another argument already triggers specialization. Unlike `@[nospecialize]`, if specialization
-happens for other reasons, parameters of this type will participate in the specialization
-rather than being ignored.
--/
-@[builtin_doc]
-builtin_initialize weakSpecializeAttr : TagAttribute ←
-  registerTagAttribute `weak_specialize
-    "mark type for weak specialization: instances are only specialized when another argument already triggers specialization"
-
 private def elabSpecArgs (declName : Name) (args : Array Syntax) : MetaM (Array Nat) := do
   if args.isEmpty then return #[]
   let info ← getConstInfo declName
@@ -93,7 +82,4 @@ def hasSpecializeAttribute (env : Environment) (declName : Name) : Bool :=
 def hasNospecializeAttribute (env : Environment) (declName : Name) : Bool :=
   nospecializeAttr.hasTag env declName
 
-def hasWeakSpecializeAttribute (env : Environment) (declName : Name) : Bool :=
-  weakSpecializeAttr.hasTag env declName
-
 end Lean.Compiler

src/Lean/CoreM.lean

@@ -343,13 +343,13 @@ def instantiateTypeLevelParams (c : ConstantVal) (us : List Level) : CoreM Expr
   modifyInstLevelTypeCache fun s => s.insert c.name (us, r)
   return r
 
-def instantiateValueLevelParams (c : ConstantInfo) (us : List Level) (allowOpaque := false) : CoreM Expr := do
+def instantiateValueLevelParams (c : ConstantInfo) (us : List Level) : CoreM Expr := do
   if let some (us', r) := (← get).cache.instLevelValue.find? c.name then
     if us == us' then
       return r
-  unless c.hasValue (allowOpaque := allowOpaque) do
+  unless c.hasValue do
     throwError "Not a definition or theorem: {.ofConstName c.name}"
-  let r := c.instantiateValueLevelParams! us (allowOpaque := allowOpaque)
+  let r := c.instantiateValueLevelParams! us
   modifyInstLevelValueCache fun s => s.insert c.name (us, r)
   return r
 
@@ -453,9 +453,6 @@ Throws an internal interrupt exception if cancellation has been requested. The e
 caught by `try catch` but is intended to be caught by `Command.withLoggingExceptions` at the top
 level of elaboration. In particular, we want to skip producing further incremental snapshots after
 the exception has been thrown.
-
-Like `checkSystem` but without the global heartbeat check, for callers that have their own
-heartbeat tracking (e.g. `SynthInstance`).
  -/
 @[inline] def checkInterrupted : CoreM Unit := do
   if let some tk := (← read).cancelTk? then
@@ -711,11 +708,11 @@ breaks the cycle by making `compileDeclsImpl` a "dynamic" call through the ref t
 to the linker. In the compiler there is a matching `builtin_initialize` to set this ref to the
 actual implementation of compileDeclsRef.
 -/
-builtin_initialize compileDeclsRef : IO.Ref (Array Name → Options → CoreM Unit) ←
-  IO.mkRef (fun _ _ => throwError m!"call to compileDecls with uninitialized compileDeclsRef")
+builtin_initialize compileDeclsRef : IO.Ref (Array Name → CoreM Unit) ←
+  IO.mkRef (fun _ => throwError m!"call to compileDecls with uninitialized compileDeclsRef")
 
 private def compileDeclsImpl (declNames : Array Name) : CoreM Unit := do
-  (← compileDeclsRef.get) declNames {}
+  (← compileDeclsRef.get) declNames
 
 -- `ref?` is used for error reporting if available
 def compileDecls (decls : Array Name) (logErrors := true) : CoreM Unit := do

src/Lean/Data/Options.lean

@@ -82,17 +82,11 @@ def mergeBy (f : Name → DataValue → DataValue → DataValue) (o1 o2 : Option
 
 end Options
 
-structure OptionDeprecation where
-  since    : String
-  text?    : Option String := none
-  deriving Inhabited
-
 structure OptionDecl where
   name     : Name
   declName : Name := by exact decl_name%
   defValue : DataValue
   descr    : String := ""
-  deprecation? : Option OptionDeprecation := none
   deriving Inhabited
 
 def OptionDecl.fullDescr (self : OptionDecl) : String := Id.run do
@@ -189,7 +183,6 @@ namespace Option
 protected structure Decl (α : Type) where
   defValue : α
   descr    : String := ""
-  deprecation? : Option OptionDeprecation := none
 
 protected def get? [KVMap.Value α] (opts : Options) (opt : Lean.Option α) : Option α :=
   opts.get? opt.name
@@ -221,7 +214,6 @@ protected def register [KVMap.Value α] (name : Name) (decl : Lean.Option.Decl
     declName := ref
     defValue := KVMap.Value.toDataValue decl.defValue
     descr := decl.descr
-    deprecation? := decl.deprecation?
   }
   return { name := name, defValue := decl.defValue }
 

src/Lean/Data/Trie.lean

@@ -60,7 +60,7 @@ instance : EmptyCollection (Trie α) :=
 instance : Inhabited (Trie α) where
   default := empty
 
-/-- Insert or update the value at the given key `s`.  -/
+/-- Insert or update the value at a the given key `s`.  -/
 partial def upsert (t : Trie α) (s : String) (f : Option α → α) : Trie α :=
   let rec insertEmpty (i : Nat) : Trie α :=
     if h : i < s.utf8ByteSize then
@@ -100,7 +100,7 @@ partial def upsert (t : Trie α) (s : String) (f : Option α → α) : Trie α :
         node (f v) cs ts
   loop 0 t
 
-/-- Inserts a value at the given key `s`, overriding an existing value if present. -/
+/-- Inserts a value at a the given key `s`, overriding an existing value if present. -/
 partial def insert (t : Trie α) (s : String) (val : α) : Trie α :=
   upsert t s (fun _ => val)
 

src/Lean/Declaration.lean

@@ -14,35 +14,29 @@ public section
 
 namespace Lean
 /--
-Reducibility hints guide the kernel's *lazy delta reduction* strategy. When the kernel encounters a
-definitional equality constraint
+Reducibility hints are used in the convertibility checker.
+When trying to solve a constraint such a
 
            (f ...) =?= (g ...)
 
-where `f` and `g` are definitions, it must decide which side to unfold. The rules (implemented in
-`lazy_delta_reduction_step` in `src/kernel/type_checker.cpp`) are:
+where f and g are definitions, the checker has to decide which one will be unfolded.
+  If      f (g) is opaque,     then g (f) is unfolded if it is also not marked as opaque,
+  Else if f (g) is abbrev,     then f (g) is unfolded if g (f) is also not marked as abbrev,
+  Else if f and g are regular, then we unfold the one with the biggest definitional height.
+  Otherwise both are unfolded.
 
-* If `f` and `g` have the **same hint kind**:
-  - Both `.opaque` or both `.abbrev`: unfold both.
-  - Both `.regular`: unfold the one with the **greater** height first. If their heights are equal
-    (in particular, if `f` and `g` are the same definition), first try to compare their arguments
-    for definitional equality (short-circuiting the unfolding if they match), then unfold both.
-* If `f` and `g` have **different hint kinds**: unfold the one that is *not* `.opaque`, preferring to
-  unfold `.abbrev` over `.regular`.
+The arguments of the `regular` Constructor are: the definitional height and the flag `selfOpt`.
 
-The `.regular` constructor carries a `UInt32` *definitional height*, which is computed by the
-elaborator as one plus the maximum height of all `.regular` constants appearing in the definition's
-body (see `getMaxHeight`). This means `.abbrev` and `.opaque` constants do not contribute to the
-height. When creating declarations via meta-programming, the height can be specified manually.
+The definitional height is by default computed by the kernel. It only takes into account
+other regular definitions used in a definition. When creating declarations using meta-programming,
+we can specify the definitional depth manually.
 
-The hints only affect performance — they control the order in which definitions are unfolded, but
-never prevent the kernel from unfolding a definition during type checking.
+Remark: the hint only affects performance. None of the hints prevent the kernel from unfolding a
+declaration during Type checking.
 
-The `ReducibilityHints` are not related to the `@[reducible]`/`@[irreducible]`/`@[semireducible]`
-attributes. Those attributes are used by the elaborator to control which definitions tactics like
-`simp`, `rfl`, and `dsimp` will unfold; they do not affect the kernel. Conversely,
-`ReducibilityHints` are set when a declaration is added to the kernel and cannot be changed
-afterwards. -/
+Remark: the ReducibilityHints are not related to the attributes: reducible/irrelevance/semireducible.
+These attributes are used by the Elaborator. The ReducibilityHints are used by the kernel (and Elaborator).
+Moreover, the ReducibilityHints cannot be changed after a declaration is added to the kernel. -/
 inductive ReducibilityHints where
   | opaque  : ReducibilityHints
   | abbrev  : ReducibilityHints
@@ -475,37 +469,24 @@ def numLevelParams (d : ConstantInfo) : Nat :=
 def type (d : ConstantInfo) : Expr :=
   d.toConstantVal.type
 
-/--
-Returns the value of a definition. With `allowOpaque := true`, values
-of theorems and opaque declarations are also returned.
--/
 def value? (info : ConstantInfo) (allowOpaque := false) : Option Expr :=
   match info with
   | .defnInfo {value, ..}   => some value
-  | .thmInfo  {value, ..}   => if allowOpaque then some value else none
+  | .thmInfo  {value, ..}   => some value
   | .opaqueInfo {value, ..} => if allowOpaque then some value else none
   | _                       => none
 
-/--
-Returns `true` if this declaration as a value for the purpose of reduction
-and type-checking, i.e. is a definition.
-With `allowOpaque := true`, theorems and opaque declarations are also considered to have values.
--/
 def hasValue (info : ConstantInfo) (allowOpaque := false) : Bool :=
   match info with
   | .defnInfo _   => true
-  | .thmInfo  _   => allowOpaque
+  | .thmInfo  _   => true
   | .opaqueInfo _ => allowOpaque
   | _             => false
 
-/--
-Returns the value of a definition. With `allowOpaque := true`, values
-of theorems and opaque declarations are also returned.
--/
 def value! (info : ConstantInfo) (allowOpaque := false) : Expr :=
   match info with
   | .defnInfo {value, ..}   => value
-  | .thmInfo  {value, ..}   => if allowOpaque then value else panic! "declaration with value expected"
+  | .thmInfo  {value, ..}   => value
   | .opaqueInfo {value, ..} => if allowOpaque then value else panic! "declaration with value expected"
   | _                       => panic! s!"declaration with value expected, but {info.name} has none"
 
@@ -529,10 +510,6 @@ def isDefinition : ConstantInfo → Bool
   | .defnInfo _ => true
   | _           => false
 
-def isTheorem : ConstantInfo → Bool
-  | .thmInfo _ => true
-  | _          => false
-
 def inductiveVal! : ConstantInfo → InductiveVal
   | .inductInfo val => val
   | _ => panic! "Expected a `ConstantInfo.inductInfo`."