chore: cleanup of Array docstrings after refactor

2026-03-18 19:04:07 +00:00 · 2024-09-25 08:59:55 +10:00
1146 changed files with 2860 additions and 13243 deletions
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -257,7 +257,7 @@ jobs:
                "cross": true,
                "shell": "bash -euxo pipefail {0}",
                // Just a few selected tests because wasm is slow
-                "CTEST_OPTIONS": "-R \"leantest_1007\\.lean|leantest_Format\\.lean|leanruntest\\_1037.lean|leanruntest_ac_rfl\\.lean|leanruntest_tempfile.lean\\.|leanruntest_libuv\\.lean\""
+                "CTEST_OPTIONS": "-R \"leantest_1007\\.lean|leantest_Format\\.lean|leanruntest\\_1037.lean|leanruntest_ac_rfl\\.lean|leanruntest_libuv\\.lean\""
              }
            ];
            console.log(`matrix:\n${JSON.stringify(matrix, null, 2)}`)
@@ -452,7 +452,7 @@ jobs:
        run: ccache -s

  # This job collects results from all the matrix jobs
-  # This can be made the "required" job, instead of listing each
+  # This can be made the “required” job, instead of listing each
  # matrix job separately
  all-done:
    name: Build matrix complete
--- a/.github/workflows/pr-release.yml
+++ b/.github/workflows/pr-release.yml
@@ -164,10 +164,10 @@ jobs:

            # Use GitHub API to check if a comment already exists
            existing_comment="$(curl --retry 3 --location --silent \
-                                    -H "Authorization: token ${{ secrets.MATHLIB4_COMMENT_BOT }}" \
+                                    -H "Authorization: token ${{ secrets.MATHLIB4_BOT }}" \
                                    -H "Accept: application/vnd.github.v3+json" \
                                    "https://api.github.com/repos/leanprover/lean4/issues/${{ steps.workflow-info.outputs.pullRequestNumber }}/comments" \
-                                    | jq 'first(.[] | select(.body | test("^- . Mathlib") or startswith("Mathlib CI status")) | select(.user.login == "leanprover-community-bot"))')"
+                                    | jq 'first(.[] | select(.body | test("^- . Mathlib") or startswith("Mathlib CI status")) | select(.user.login == "leanprover-community-mathlib4-bot"))')"
            existing_comment_id="$(echo "$existing_comment" | jq -r .id)"
            existing_comment_body="$(echo "$existing_comment" | jq -r .body)"

@@ -177,14 +177,14 @@ jobs:
              echo "Posting message to the comments: $MESSAGE"

              # Append new result to the existing comment or post a new comment
-              # It's essential we use the MATHLIB4_COMMENT_BOT token here, so that Mathlib CI can subsequently edit the comment.
+              # It's essential we use the MATHLIB4_BOT token here, so that Mathlib CI can subsequently edit the comment.
              if [ -z "$existing_comment_id" ]; then
                INTRO="Mathlib CI status ([docs](https://leanprover-community.github.io/contribute/tags_and_branches.html)):"
                # Post new comment with a bullet point
                echo "Posting as new comment at leanprover/lean4/issues/${{ steps.workflow-info.outputs.pullRequestNumber }}/comments"
                curl -L -s \
                  -X POST \
-                  -H "Authorization: token ${{ secrets.MATHLIB4_COMMENT_BOT }}" \
+                  -H "Authorization: token ${{ secrets.MATHLIB4_BOT }}" \
                  -H "Accept: application/vnd.github.v3+json" \
                  -d "$(jq --null-input --arg intro "$INTRO" --arg val "$MESSAGE" '{"body":($intro + "\n" + $val)}')" \
                  "https://api.github.com/repos/leanprover/lean4/issues/${{ steps.workflow-info.outputs.pullRequestNumber }}/comments"
@@ -193,7 +193,7 @@ jobs:
                echo "Appending to existing comment at leanprover/lean4/issues/${{ steps.workflow-info.outputs.pullRequestNumber }}/comments"
                curl -L -s \
                  -X PATCH \
-                  -H "Authorization: token ${{ secrets.MATHLIB4_COMMENT_BOT }}" \
+                  -H "Authorization: token ${{ secrets.MATHLIB4_BOT }}" \
                  -H "Accept: application/vnd.github.v3+json" \
                  -d "$(jq --null-input --arg existing "$existing_comment_body" --arg message "$MESSAGE" '{"body":($existing + "\n" + $message)}')" \
                  "https://api.github.com/repos/leanprover/lean4/issues/comments/$existing_comment_id"
@@ -340,7 +340,6 @@ jobs:
            # (This should no longer be possible once `nightly-testing-YYYY-MM-DD` is a tag, but it is still safe to merge.)
            git merge "$BASE" --strategy-option ours --no-commit --allow-unrelated-histories
            lake update batteries
-            git add lake-manifest.json
            git commit --allow-empty -m "Trigger CI for https://github.com/leanprover/lean4/pull/${{ steps.workflow-info.outputs.pullRequestNumber }}"
          fi

--- a/RELEASES.md
+++ b/RELEASES.md
@@ -10,317 +10,7 @@ of each version.

 v4.12.0
 ----------
-
-### Language features, tactics, and metaprograms
-
-* `bv_decide` tactic. This release introduces a new tactic for proving goals involving `BitVec` and `Bool`. It reduces the goal to a SAT instance that is refuted by an external solver, and the resulting LRAT proof is checked in Lean. This is used to synthesize a proof of the goal by reflection. As this process uses verified algorithms, proofs generated by this tactic use `Lean.ofReduceBool`, so this tactic includes the Lean compiler as part of the trusted code base. The external solver CaDiCaL is included with Lean and does not need to be installed separately to make use of `bv_decide`.
-
-  For example, we can use `bv_decide` to verify that a bit twiddling formula leaves at most one bit set:
-  ```lean
-  def popcount (x : BitVec 64) : BitVec 64 :=
-    let rec go (x pop : BitVec 64) : Nat → BitVec 64
-      | 0 => pop
-      | n + 1 => go (x >>> 2) (pop + (x &&& 1)) n
-    go x 0 64
-
-  example (x : BitVec 64) : popcount ((x &&& (x - 1)) ^^^ x) ≤ 1 := by
-    simp only [popcount, popcount.go]
-    bv_decide
-  ```
-  When the external solver fails to refute the SAT instance generated by `bv_decide`, it can report a counterexample:
-  ```lean
-  /--
-  error: The prover found a counterexample, consider the following assignment:
-  x = 0xffffffffffffffff#64
-  -/
-  #guard_msgs in
-  example (x : BitVec 64) : x < x + 1 := by
-    bv_decide
-  ```
-
-  See `Lean.Elab.Tactic.BVDecide` for a more detailed overview, and look in `tests/lean/run/bv_*` for examples.
-
-  [#5013](https://github.com/leanprover/lean4/pull/5013), [#5074](https://github.com/leanprover/lean4/pull/5074), [#5100](https://github.com/leanprover/lean4/pull/5100), [#5113](https://github.com/leanprover/lean4/pull/5113), [#5137](https://github.com/leanprover/lean4/pull/5137), [#5203](https://github.com/leanprover/lean4/pull/5203), [#5212](https://github.com/leanprover/lean4/pull/5212), [#5220](https://github.com/leanprover/lean4/pull/5220).
-
-* `simp` tactic
-  * [#4988](https://github.com/leanprover/lean4/pull/4988) fixes a panic in the `reducePow` simproc.
-  * [#5071](https://github.com/leanprover/lean4/pull/5071) exposes the `index` option to the `dsimp` tactic, introduced to `simp` in [#4202](https://github.com/leanprover/lean4/pull/4202).
-  * [#5159](https://github.com/leanprover/lean4/pull/5159) fixes a panic at `Fin.isValue` simproc.
-  * [#5167](https://github.com/leanprover/lean4/pull/5167) and [#5175](https://github.com/leanprover/lean4/pull/5175) rename the `simpCtorEq` simproc to `reduceCtorEq` and makes it optional. (See breaking changes.)
-  * [#5187](https://github.com/leanprover/lean4/pull/5187) ensures `reduceCtorEq` is enabled in the `norm_cast` tactic.
-  * [#5073](https://github.com/leanprover/lean4/pull/5073) modifies the simp debug trace messages to tag with "dpre" and "dpost" instead of "pre" and "post" when in definitional rewrite mode. [#5054](https://github.com/leanprover/lean4/pull/5054) explains the `reduce` steps for `trace.Debug.Meta.Tactic.simp` trace messages.
-* `ext` tactic
-  * [#4996](https://github.com/leanprover/lean4/pull/4996) reduces default maximum iteration depth from 1000000 to 100.
-* `induction` tactic
-  * [#5117](https://github.com/leanprover/lean4/pull/5117) fixes a bug where `let` bindings in minor premises wouldn't be counted correctly.
-
-* `omega` tactic
-  * [#5157](https://github.com/leanprover/lean4/pull/5157) fixes a panic.
-
-* `conv` tactic
-  * [#5149](https://github.com/leanprover/lean4/pull/5149) improves `arg n` to handle subsingleton instance arguments.
-
-* [#5044](https://github.com/leanprover/lean4/pull/5044) upstreams the `#time` command.
-* [#5079](https://github.com/leanprover/lean4/pull/5079) makes `#check` and `#reduce` typecheck the elaborated terms.
-
-* **Incrementality**
-  * [#4974](https://github.com/leanprover/lean4/pull/4974) fixes regression where we would not interrupt elaboration of previous document versions.
-  * [#5004](https://github.com/leanprover/lean4/pull/5004) fixes a performance regression.
-  * [#5001](https://github.com/leanprover/lean4/pull/5001) disables incremental body elaboration in presence of `where` clauses in declarations.
-  * [#5018](https://github.com/leanprover/lean4/pull/5018) enables infotrees on the command line for ilean generation.
-  * [#5040](https://github.com/leanprover/lean4/pull/5040) and [#5056](https://github.com/leanprover/lean4/pull/5056) improve performance of info trees.
-  * [#5090](https://github.com/leanprover/lean4/pull/5090) disables incrementality in the `case .. | ..` tactic.
-  * [#5312](https://github.com/leanprover/lean4/pull/5312) fixes a bug where changing whitespace after the module header could break subsequent commands.
-
-* **Definitions**
-  * [#5016](https://github.com/leanprover/lean4/pull/5016) and [#5066](https://github.com/leanprover/lean4/pull/5066) add `clean_wf` tactic to clean up tactic state in `decreasing_by`. This can be disabled with `set_option debug.rawDecreasingByGoal false`.
-  * [#5055](https://github.com/leanprover/lean4/pull/5055) unifies equational theorems between structural and well-founded recursion.
-  * [#5041](https://github.com/leanprover/lean4/pull/5041) allows mutually recursive functions to use different parameter names among the “fixed parameter prefix”
-  * [#4154](https://github.com/leanprover/lean4/pull/4154) and [#5109](https://github.com/leanprover/lean4/pull/5109) add fine-grained equational lemmas for non-recursive functions. See breaking changes.
-  * [#5129](https://github.com/leanprover/lean4/pull/5129) unifies equation lemmas for recursive and non-recursive definitions. The `backward.eqns.deepRecursiveSplit` option can be set to `false` to get the old behavior. See breaking changes.
-  * [#5141](https://github.com/leanprover/lean4/pull/5141) adds `f.eq_unfold` lemmas. Now Lean produces the following zoo of rewrite rules:
-    ```
-    Option.map.eq_1      : Option.map f none = none
-    Option.map.eq_2      : Option.map f (some x) = some (f x)
-    Option.map.eq_def    : Option.map f p = match o with | none => none | (some x) => some (f x)
-    Option.map.eq_unfold : Option.map = fun f p => match o with | none => none | (some x) => some (f x)
-    ```
-    The `f.eq_unfold` variant is especially useful to rewrite with `rw` under binders.
-  * [#5136](https://github.com/leanprover/lean4/pull/5136) fixes bugs in recursion over predicates.
-
-* **Variable inclusion**
-  * [#5206](https://github.com/leanprover/lean4/pull/5206) documents that `include` currently only applies to theorems.
-
-* **Elaboration**
-  * [#4926](https://github.com/leanprover/lean4/pull/4926) fixes a bug where autoparam errors were associated to an incorrect source position.
-  * [#4833](https://github.com/leanprover/lean4/pull/4833) fixes an issue where cdot anonymous functions (e.g. `(· + ·)`) would not handle ambiguous notation correctly. Numbers the parameters, making this example expand as `fun x1 x2 => x1 + x2` rather than `fun x x_1 => x + x_1`.
-  * [#5037](https://github.com/leanprover/lean4/pull/5037) improves strength of the tactic that proves array indexing is in bounds.
-  * [#5119](https://github.com/leanprover/lean4/pull/5119) fixes a bug in the tactic that proves indexing is in bounds where it could loop in the presence of mvars.
-  * [#5072](https://github.com/leanprover/lean4/pull/5072) makes the structure type clickable in "not a field of structure" errors for structure instance notation.
-  * [#4717](https://github.com/leanprover/lean4/pull/4717) fixes a bug where mutual `inductive` commands could create terms that the kernel rejects.
-  * [#5142](https://github.com/leanprover/lean4/pull/5142) fixes a bug where `variable` could fail when mixing binder updates and declarations.
-
-* **Other fixes or improvements**
-  * [#5118](https://github.com/leanprover/lean4/pull/5118) changes the definition of the `syntheticHole` parser so that hovering over `_` in `?_` gives the docstring for synthetic holes.
-  * [#5173](https://github.com/leanprover/lean4/pull/5173) uses the emoji variant selector for ✅️,❌️,💥️ in messages, improving fonts selection.
-  * [#5183](https://github.com/leanprover/lean4/pull/5183) fixes a bug in `rename_i` where implementation detail hypotheses could be renamed.
-
-### Language server, widgets, and IDE extensions
-
-* [#4821](https://github.com/leanprover/lean4/pull/4821) resolves two language server bugs that especially affect Windows users. (1) Editing the header could result in the watchdog not correctly restarting the file worker, which would lead to the file seemingly being processed forever. (2) On an especially slow Windows machine, we found that starting the language server would sometimes not succeed at all. This PR also resolves an issue where we would not correctly emit messages that we received while the file worker is being restarted to the corresponding file worker after the restart.
-* [#5006](https://github.com/leanprover/lean4/pull/5006) updates the user widget manual.
-* [#5193](https://github.com/leanprover/lean4/pull/5193) updates the quickstart guide with the new display name for the Lean 4 extension ("Lean 4").
-* [#5185](https://github.com/leanprover/lean4/pull/5185) fixes a bug where over time "import out of date" messages would accumulate.
-* [#4900](https://github.com/leanprover/lean4/pull/4900) improves ilean loading performance by about a factor of two. Optimizes the JSON parser and the conversion from JSON to Lean data structures; see PR description for details.
-* **Other fixes or improvements**
-  * [#5031](https://github.com/leanprover/lean4/pull/5031) localizes an instance in `Lsp.Diagnostics`.
-
-### Pretty printing
-
-* [#4976](https://github.com/leanprover/lean4/pull/4976) introduces `@[app_delab]`, a macro for creating delaborators for particular constants. The `@[app_delab ident]` syntax resolves `ident` to its constant name `name` and then expands to `@[delab app.name]`.
-* [#4982](https://github.com/leanprover/lean4/pull/4982) fixes a bug where the pretty printer assumed structure projections were type correct (such terms can appear in type mismatch errors). Improves hoverability of `#print` output for structures.
-* [#5218](https://github.com/leanprover/lean4/pull/5218) and [#5239](https://github.com/leanprover/lean4/pull/5239) add `pp.exprSizes` debugging option. When true, each pretty printed expression is prefixed with `[size a/b/c]`, where `a` is the size without sharing, `b` is the actual size, and `c` is the size with the maximum possible sharing.
-
-### Library
-
-* [#5020](https://github.com/leanprover/lean4/pull/5020) swaps the parameters to `Membership.mem`. A purpose of this change is to make set-like `CoeSort` coercions to refer to the eta-expanded function `fun x => Membership.mem s x`, which can reduce in many computations. Another is that having the `s` argument first leads to better discrimination tree keys. (See breaking changes.)
-* `Array`
-  * [#4970](https://github.com/leanprover/lean4/pull/4970) adds `@[ext]` attribute to `Array.ext`.
-  * [#4957](https://github.com/leanprover/lean4/pull/4957) deprecates `Array.get_modify`.
-* `List`
-  * [#4995](https://github.com/leanprover/lean4/pull/4995) upstreams `List.findIdx` lemmas.
-  * [#5029](https://github.com/leanprover/lean4/pull/5029), [#5048](https://github.com/leanprover/lean4/pull/5048) and [#5132](https://github.com/leanprover/lean4/pull/5132) add `List.Sublist` lemmas, some upstreamed. [#5077](https://github.com/leanprover/lean4/pull/5077) fixes implicitness in refl/rfl lemma binders.  add `List.Sublist` theorems.
-  * [#5047](https://github.com/leanprover/lean4/pull/5047) upstreams `List.Pairwise` lemmas.
-  * [#5053](https://github.com/leanprover/lean4/pull/5053), [#5124](https://github.com/leanprover/lean4/pull/5124), and [#5161](https://github.com/leanprover/lean4/pull/5161) add `List.find?/findSome?/findIdx?` theorems.
-  * [#5039](https://github.com/leanprover/lean4/pull/5039) adds `List.foldlRecOn` and `List.foldrRecOn` recursion principles to prove things about `List.foldl` and `List.foldr`.
-  * [#5069](https://github.com/leanprover/lean4/pull/5069) upstreams `List.Perm`.
-  * [#5092](https://github.com/leanprover/lean4/pull/5092) and [#5107](https://github.com/leanprover/lean4/pull/5107) add `List.mergeSort` and a fast `@[csimp]` implementation.
-  * [#5103](https://github.com/leanprover/lean4/pull/5103) makes the simp lemmas for `List.subset` more aggressive.
-  * [#5106](https://github.com/leanprover/lean4/pull/5106) changes the statement of `List.getLast?_cons`.
-  * [#5123](https://github.com/leanprover/lean4/pull/5123) and [#5158](https://github.com/leanprover/lean4/pull/5158) add `List.range` and `List.iota` lemmas.
-  * [#5130](https://github.com/leanprover/lean4/pull/5130) adds `List.join` lemmas.
-  * [#5131](https://github.com/leanprover/lean4/pull/5131) adds `List.append` lemmas.
-  * [#5152](https://github.com/leanprover/lean4/pull/5152) adds `List.erase(|P|Idx)` lemmas.
-  * [#5127](https://github.com/leanprover/lean4/pull/5127) makes miscellaneous lemma updates.
-  * [#5153](https://github.com/leanprover/lean4/pull/5153) and [#5160](https://github.com/leanprover/lean4/pull/5160) add lemmas about `List.attach` and `List.pmap`.
-  * [#5164](https://github.com/leanprover/lean4/pull/5164), [#5177](https://github.com/leanprover/lean4/pull/5177), and [#5215](https://github.com/leanprover/lean4/pull/5215) add `List.find?` and `List.range'/range/iota` lemmas.
-  * [#5196](https://github.com/leanprover/lean4/pull/5196) adds `List.Pairwise_erase` and related lemmas.
-  * [#5151](https://github.com/leanprover/lean4/pull/5151) and [#5163](https://github.com/leanprover/lean4/pull/5163) improve confluence of `List` simp lemmas. [#5105](https://github.com/leanprover/lean4/pull/5105) and [#5102](https://github.com/leanprover/lean4/pull/5102) adjust `List` simp lemmas.
-  * [#5178](https://github.com/leanprover/lean4/pull/5178) removes `List.getLast_eq_iff_getLast_eq_some` as a simp lemma.
-  * [#5210](https://github.com/leanprover/lean4/pull/5210) reverses the meaning of `List.getElem_drop` and `List.getElem_drop'`.
-  * [#5214](https://github.com/leanprover/lean4/pull/5214) moves `@[csimp]` lemmas earlier where possible.
-* `Nat` and `Int`
-  * [#5104](https://github.com/leanprover/lean4/pull/5104) adds `Nat.add_left_eq_self` and relatives.
-  * [#5146](https://github.com/leanprover/lean4/pull/5146) adds missing `Nat.and_xor_distrib_(left|right)`.
-  * [#5148](https://github.com/leanprover/lean4/pull/5148) and [#5190](https://github.com/leanprover/lean4/pull/5190) improve `Nat` and `Int` simp lemma confluence.
-  * [#5165](https://github.com/leanprover/lean4/pull/5165) adjusts `Int` simp lemmas.
-  * [#5166](https://github.com/leanprover/lean4/pull/5166) adds `Int` lemmas relating `neg` and `emod`/`mod`.
-  * [#5208](https://github.com/leanprover/lean4/pull/5208) reverses the direction of the `Int.toNat_sub` simp lemma.
-  * [#5209](https://github.com/leanprover/lean4/pull/5209) adds `Nat.bitwise` lemmas.
-  * [#5230](https://github.com/leanprover/lean4/pull/5230) corrects the docstrings for integer division and modulus.
-* `Option`
-  * [#5128](https://github.com/leanprover/lean4/pull/5128) and [#5154](https://github.com/leanprover/lean4/pull/5154) add `Option` lemmas.
-* `BitVec`
-  * [#4889](https://github.com/leanprover/lean4/pull/4889) adds `sshiftRight` bitblasting.
-  * [#4981](https://github.com/leanprover/lean4/pull/4981) adds `Std.Associative` and `Std.Commutative` instances for `BitVec.[and|or|xor]`.
-  * [#4913](https://github.com/leanprover/lean4/pull/4913) enables `missingDocs` error for `BitVec` modules.
-  * [#4930](https://github.com/leanprover/lean4/pull/4930) makes parameter names for `BitVec` more consistent.
-  * [#5098](https://github.com/leanprover/lean4/pull/5098) adds `BitVec.intMin`. Introduces `boolToPropSimps` simp set for converting from boolean to propositional expressions.
-  * [#5200](https://github.com/leanprover/lean4/pull/5200) and [#5217](https://github.com/leanprover/lean4/pull/5217) rename `BitVec.getLsb` to `BitVec.getLsbD`, etc., to bring naming in line with `List`/`Array`/etc.
-  * **Theorems:** [#4977](https://github.com/leanprover/lean4/pull/4977), [#4951](https://github.com/leanprover/lean4/pull/4951), [#4667](https://github.com/leanprover/lean4/pull/4667), [#5007](https://github.com/leanprover/lean4/pull/5007), [#4997](https://github.com/leanprover/lean4/pull/4997), [#5083](https://github.com/leanprover/lean4/pull/5083), [#5081](https://github.com/leanprover/lean4/pull/5081), [#4392](https://github.com/leanprover/lean4/pull/4392)
-* `UInt`
-  * [#4514](https://github.com/leanprover/lean4/pull/4514) fixes naming convention for `UInt` lemmas.
-* `Std.HashMap` and `Std.HashSet`
-  * [#4943](https://github.com/leanprover/lean4/pull/4943) deprecates variants of hash map query methods. (See breaking changes.)
-  * [#4917](https://github.com/leanprover/lean4/pull/4917) switches the library and Lean to `Std.HashMap` and `Std.HashSet` almost everywhere.
-  * [#4954](https://github.com/leanprover/lean4/pull/4954) deprecates `Lean.HashMap` and `Lean.HashSet`.
-  * [#5023](https://github.com/leanprover/lean4/pull/5023) cleans up lemma parameters.
-
-* `Std.Sat` (for `bv_decide`)
-  * [#4933](https://github.com/leanprover/lean4/pull/4933) adds definitions of SAT and CNF.
-  * [#4953](https://github.com/leanprover/lean4/pull/4953) defines "and-inverter graphs" (AIGs) as described in section 3 of [Davis-Swords 2013](https://arxiv.org/pdf/1304.7861.pdf).
-
-* **Parsec**
-  * [#4774](https://github.com/leanprover/lean4/pull/4774) generalizes the `Parsec` library, allowing parsing of iterable data beyond `String` such as `ByteArray`. (See breaking changes.)
-  * [#5115](https://github.com/leanprover/lean4/pull/5115) moves `Lean.Data.Parsec` to `Std.Internal.Parsec` for bootstrappng reasons.
-
-* `Thunk`
-  * [#4969](https://github.com/leanprover/lean4/pull/4969) upstreams `Thunk.ext`.
-
-* **IO**
-  * [#4973](https://github.com/leanprover/lean4/pull/4973) modifies `IO.FS.lines` to handle `\r\n` on all operating systems instead of just on Windows.
-  * [#5125](https://github.com/leanprover/lean4/pull/5125) adds `createTempFile` and `withTempFile` for creating temporary files that can only be read and written by the current user.
-
-* **Other fixes or improvements**
-  * [#4945](https://github.com/leanprover/lean4/pull/4945) adds `Array`, `Bool` and `Prod` utilities from LeanSAT.
-  * [#4960](https://github.com/leanprover/lean4/pull/4960) adds `Relation.TransGen.trans`.
-  * [#5012](https://github.com/leanprover/lean4/pull/5012) states `WellFoundedRelation Nat` using `<`, not `Nat.lt`.
-  * [#5011](https://github.com/leanprover/lean4/pull/5011) uses `≠` instead of `Not (Eq ...)` in `Fin.ne_of_val_ne`.
-  * [#5197](https://github.com/leanprover/lean4/pull/5197) upstreams `Fin.le_antisymm`.
-  * [#5042](https://github.com/leanprover/lean4/pull/5042) reduces usage of `refine'`.
-  * [#5101](https://github.com/leanprover/lean4/pull/5101) adds about `if-then-else` and `Option`.
-  * [#5112](https://github.com/leanprover/lean4/pull/5112) adds basic instances for `ULift` and `PLift`.
-  * [#5133](https://github.com/leanprover/lean4/pull/5133) and [#5168](https://github.com/leanprover/lean4/pull/5168) make fixes from running the simpNF linter over Lean.
-  * [#5156](https://github.com/leanprover/lean4/pull/5156) removes a bad simp lemma in `omega` theory.
-  * [#5155](https://github.com/leanprover/lean4/pull/5155) improves confluence of `Bool` simp lemmas.
-  * [#5162](https://github.com/leanprover/lean4/pull/5162) improves confluence of `Function.comp` simp lemmas.
-  * [#5191](https://github.com/leanprover/lean4/pull/5191) improves confluence of `if-then-else` simp lemmas.
-  * [#5147](https://github.com/leanprover/lean4/pull/5147) adds `@[elab_as_elim]` to `Quot.rec`, `Nat.strongInductionOn` and `Nat.casesStrongInductionOn`, and also renames the latter two to `Nat.strongRecOn` and `Nat.casesStrongRecOn` (deprecated in [#5179](https://github.com/leanprover/lean4/pull/5179)).
-  * [#5180](https://github.com/leanprover/lean4/pull/5180) disables some simp lemmas with bad discrimination tree keys.
-  * [#5189](https://github.com/leanprover/lean4/pull/5189) cleans up internal simp lemmas that had leaked.
-  * [#5198](https://github.com/leanprover/lean4/pull/5198) cleans up `allowUnsafeReducibility`.
-  * [#5229](https://github.com/leanprover/lean4/pull/5229) removes unused lemmas from some `simp` tactics.
-  * [#5199](https://github.com/leanprover/lean4/pull/5199) removes >6 month deprecations.
-
-### Lean internals
-
-* **Performance**
-  * Some core algorithms have been rewritten in C++ for performance.
-    * [#4910](https://github.com/leanprover/lean4/pull/4910) and [#4912](https://github.com/leanprover/lean4/pull/4912) reimplement `instantiateLevelMVars`.
-    * [#4915](https://github.com/leanprover/lean4/pull/4915), [#4922](https://github.com/leanprover/lean4/pull/4922), and [#4931](https://github.com/leanprover/lean4/pull/4931) reimplement `instantiateExprMVars`, 30% faster on a benchmark.
-  * [#4934](https://github.com/leanprover/lean4/pull/4934) has optimizations for the kernel's `Expr` equality test.
-  * [#4990](https://github.com/leanprover/lean4/pull/4990) fixes bug in hashing for the kernel's `Expr` equality test.
-  * [#4935](https://github.com/leanprover/lean4/pull/4935) and [#4936](https://github.com/leanprover/lean4/pull/4936) skip some `PreDefinition` transformations if they are not needed.
-  * [#5225](https://github.com/leanprover/lean4/pull/5225) adds caching for visited exprs at `CheckAssignmentQuick` in `ExprDefEq`.
-  * [#5226](https://github.com/leanprover/lean4/pull/5226) maximizes term sharing at `instantiateMVarDeclMVars`, used by `runTactic`.
-* **Diagnostics and profiling**
-  * [#4923](https://github.com/leanprover/lean4/pull/4923) adds profiling for `instantiateMVars` in `Lean.Elab.MutualDef`, which can be a bottleneck there.
-  * [#4924](https://github.com/leanprover/lean4/pull/4924) adds diagnostics for large theorems, controlled by the `diagnostics.threshold.proofSize` option.
-  * [#4897](https://github.com/leanprover/lean4/pull/4897) improves display of diagnostic results.
-* **Other fixes or improvements**
-  * [#4921](https://github.com/leanprover/lean4/pull/4921) cleans up `Expr.betaRev`.
-  * [#4940](https://github.com/leanprover/lean4/pull/4940) fixes tests by not writing directly to stdout, which is unreliable now that elaboration and reporting are executed in separate threads.
-  * [#4955](https://github.com/leanprover/lean4/pull/4955) documents that `stderrAsMessages` is now the default on the command line as well.
-  * [#4647](https://github.com/leanprover/lean4/pull/4647) adjusts documentation for building on macOS.
-  * [#4987](https://github.com/leanprover/lean4/pull/4987) makes regular mvar assignments take precedence over delayed ones in `instantiateMVars`. Normally delayed assignment metavariables are never directly assigned, but on errors Lean assigns `sorry` to unassigned metavariables.
-  * [#4967](https://github.com/leanprover/lean4/pull/4967) adds linter name to errors when a linter crashes.
-  * [#5043](https://github.com/leanprover/lean4/pull/5043) cleans up command line snapshots logic.
-  * [#5067](https://github.com/leanprover/lean4/pull/5067) minimizes some imports.
-  * [#5068](https://github.com/leanprover/lean4/pull/5068) generalizes the monad for `addMatcherInfo`.
-  * [f71a1f](https://github.com/leanprover/lean4/commit/f71a1fb4ae958fccb3ad4d48786a8f47ced05c15) adds missing test for [#5126](https://github.com/leanprover/lean4/issues/5126).
-  * [#5201](https://github.com/leanprover/lean4/pull/5201) restores a test.
-  * [#3698](https://github.com/leanprover/lean4/pull/3698) fixes a bug where label attributes did not pass on the attribute kind.
-  * Typos: [#5080](https://github.com/leanprover/lean4/pull/5080), [#5150](https://github.com/leanprover/lean4/pull/5150), [#5202](https://github.com/leanprover/lean4/pull/5202)
-
-### Compiler, runtime, and FFI
-
-* [#3106](https://github.com/leanprover/lean4/pull/3106) moves frontend to new snapshot architecture. Note that `Frontend.processCommand` and `FrontendM` are no longer used by Lean core, but they will be preserved.
-* [#4919](https://github.com/leanprover/lean4/pull/4919) adds missing include in runtime for `AUTO_THREAD_FINALIZATION` feature on Windows.
-* [#4941](https://github.com/leanprover/lean4/pull/4941) adds more `LEAN_EXPORT`s for Windows.
-* [#4911](https://github.com/leanprover/lean4/pull/4911) improves formatting of CLI help text for the frontend.
-* [#4950](https://github.com/leanprover/lean4/pull/4950) improves file reading and writing.
-  * `readBinFile` and `readFile` now only require two system calls (`stat` + `read`) instead of one `read` per 1024 byte chunk.
-  * `Handle.getLine` and `Handle.putStr` no longer get tripped up by NUL characters.
-* [#4971](https://github.com/leanprover/lean4/pull/4971) handles the SIGBUS signal when detecting stack overflows.
-* [#5062](https://github.com/leanprover/lean4/pull/5062) avoids overwriting existing signal handlers, like in [rust-lang/rust#69685](https://github.com/rust-lang/rust/pull/69685).
-* [#4860](https://github.com/leanprover/lean4/pull/4860) improves workarounds for building on Windows. Splits `libleanshared` on Windows to avoid symbol limit, removes the `LEAN_EXPORT` denylist workaround, adds missing `LEAN_EXPORT`s.
-* [#4952](https://github.com/leanprover/lean4/pull/4952) output panics into Lean's redirected stderr, ensuring panics ARE visible as regular messages in the language server and properly ordered in relation to other messages on the command line.
-* [#4963](https://github.com/leanprover/lean4/pull/4963) links LibUV.
-
-### Lake
-
-* [#5030](https://github.com/leanprover/lean4/pull/5030) removes dead code.
-* [#4770](https://github.com/leanprover/lean4/pull/4770) adds additional fields to the package configuration which will be used by Reservoir. See the PR description for details.
-
-
-### DevOps/CI
-* [#4914](https://github.com/leanprover/lean4/pull/4914) and [#4937](https://github.com/leanprover/lean4/pull/4937) improve the release checklist.
-* [#4925](https://github.com/leanprover/lean4/pull/4925) ignores stale leanpkg tests.
-* [#5003](https://github.com/leanprover/lean4/pull/5003) upgrades `actions/cache` in CI.
-* [#5010](https://github.com/leanprover/lean4/pull/5010) sets `save-always` in cache actions in CI.
-* [#5008](https://github.com/leanprover/lean4/pull/5008) adds more libuv search patterns for the speedcenter.
-* [#5009](https://github.com/leanprover/lean4/pull/5009) reduce number of runs in the speedcenter for "fast" benchmarks from 10 to 3.
-* [#5014](https://github.com/leanprover/lean4/pull/5014) adjusts lakefile editing to use new `git` syntax in `pr-release` workflow.
-* [#5025](https://github.com/leanprover/lean4/pull/5025) has `pr-release` workflow pass `--retry` to `curl`.
-* [#5022](https://github.com/leanprover/lean4/pull/5022) builds MacOS Aarch64 release for PRs by default.
-* [#5045](https://github.com/leanprover/lean4/pull/5045) adds libuv to the required packages heading in macos docs.
-* [#5034](https://github.com/leanprover/lean4/pull/5034) fixes the install name of `libleanshared_1` on macOS.
-* [#5051](https://github.com/leanprover/lean4/pull/5051) fixes Windows stage 0.
-* [#5052](https://github.com/leanprover/lean4/pull/5052) fixes 32bit stage 0 builds in CI.
-* [#5057](https://github.com/leanprover/lean4/pull/5057) avoids rebuilding `leanmanifest` in each build.
-* [#5099](https://github.com/leanprover/lean4/pull/5099) makes `restart-on-label` workflow also filter by commit SHA.
-* [#4325](https://github.com/leanprover/lean4/pull/4325) adds CaDiCaL.
-
-### Breaking changes
-
-* [LibUV](https://libuv.org/) is now required to build Lean. This change only affects developers who compile Lean themselves instead of obtaining toolchains via `elan`. We have updated the official build instructions with information on how to obtain LibUV on our supported platforms. ([#4963](https://github.com/leanprover/lean4/pull/4963))
-
-* Recursive definitions with a `decreasing_by` clause that begins with `simp_wf` may break. Try removing `simp_wf` or replacing it with `simp`. ([#5016](https://github.com/leanprover/lean4/pull/5016))
-
-* The behavior of `rw [f]` where `f` is a non-recursive function defined by pattern matching changed.
-
-  For example, preciously, `rw [Option.map]` would rewrite `Option.map f o` to `match o with … `. Now this rewrite fails because it will use the equational lemmas, and these require constructors – just like for `List.map`.
-
-  Remedies:
-  * Split on `o` before rewriting.
-  * Use `rw [Option.map.eq_def]`, which rewrites any (saturated) application of `Option.map`.
-  * Use `set_option backward.eqns.nonrecursive false` when *defining* the function in question.
-  ([#4154](https://github.com/leanprover/lean4/pull/4154))
-
-* The unified handling of equation lemmas for recursive and non-recursive functions can break existing code, as there now can be extra equational lemmas:
-
-  * Explicit uses of `f.eq_2` might have to be adjusted if the numbering changed.
-
-  * Uses of `rw [f]` or `simp [f]` may no longer apply if they previously matched (and introduced a `match` statement), when the equational lemmas got more fine-grained.
-
-    In this case either case analysis on the parameters before rewriting helps, or setting the option `backward.eqns.deepRecursiveSplit false` while *defining* the function.
-
-  ([#5129](https://github.com/leanprover/lean4/pull/5129), [#5207](https://github.com/leanprover/lean4/pull/5207))
-
-* The `reduceCtorEq` simproc is now optional, and it might need to be included in lists of simp lemmas, like `simp only [reduceCtorEq]`. This simproc is responsible for reducing equalities of constructors. ([#5167](https://github.com/leanprover/lean4/pull/5167))
-
-* `Nat.strongInductionOn` is now `Nat.strongRecOn` and `Nat.caseStrongInductionOn` to `Nat.caseStrongRecOn`. ([#5147](https://github.com/leanprover/lean4/pull/5147))
-
-* The parameters to `Membership.mem` have been swapped, which affects all `Membership` instances. ([#5020](https://github.com/leanprover/lean4/pull/5020))
-
-* The meanings of `List.getElem_drop` and `List.getElem_drop'` have been reversed and the first is now a simp lemma. ([#5210](https://github.com/leanprover/lean4/pull/5210))
-
-* The `Parsec` library has moved from `Lean.Data.Parsec` to `Std.Internal.Parsec`. The `Parsec` type is now more general with a parameter for an iterable. Users parsing strings can migrate to `Parser` in the `Std.Internal.Parsec.String` namespace, which also includes string-focused parsing combinators. ([#4774](https://github.com/leanprover/lean4/pull/4774))
-
-* The `Lean` module has switched from `Lean.HashMap` and `Lean.HashSet` to `Std.HashMap` and `Std.HashSet` ([#4943](https://github.com/leanprover/lean4/pull/4943)). `Lean.HashMap` and `Lean.HashSet` are now deprecated ([#4954](https://github.com/leanprover/lean4/pull/4954)) and will be removed in a future release. Users of `Lean` APIs that interact with hash maps, for example `Lean.Environment.const2ModIdx`, might encounter minor breakage due to the following changes from `Lean.HashMap` to `Std.HashMap`:
-  * query functions use the term `get` instead of `find`, ([#4943](https://github.com/leanprover/lean4/pull/4943))
-  * the notation `map[key]` no longer returns an optional value but instead expects a proof that the key is present in the map. The previous behavior is available via the `map[key]?` notation.
-
+Development in progress.

 v4.11.0
 ----------
@@ -331,7 +21,7 @@ v4.11.0

  See breaking changes below.

-  PRs: [#4883](https://github.com/leanprover/lean4/pull/4883), [#4814](https://github.com/leanprover/lean4/pull/4814), [#5000](https://github.com/leanprover/lean4/pull/5000), [#5036](https://github.com/leanprover/lean4/pull/5036), [#5138](https://github.com/leanprover/lean4/pull/5138), [0edf1b](https://github.com/leanprover/lean4/commit/0edf1bac392f7e2fe0266b28b51c498306363a84).
+  PRs: [#4883](https://github.com/leanprover/lean4/pull/4883), [1242ff](https://github.com/leanprover/lean4/commit/1242ffbfb5a79296041683682268e770fc3cf820), [#5000](https://github.com/leanprover/lean4/pull/5000), [#5036](https://github.com/leanprover/lean4/pull/5036), [#5138](https://github.com/leanprover/lean4/pull/5138), [0edf1b](https://github.com/leanprover/lean4/commit/0edf1bac392f7e2fe0266b28b51c498306363a84).

 * **Recursive definitions**
  * Structural recursion can now be explicitly requested using
--- a/doc/make/msys2.md
+++ b/doc/make/msys2.md
@@ -18,14 +18,14 @@ the stdlib.
 ## Installing dependencies

 [The official webpage of MSYS2][msys2] provides one-click installers.
-Once installed, you should run the "MSYS2 CLANG64" shell from the start menu (the one that runs `clang64.exe`).
-Do not run "MSYS2 MSYS" or "MSYS2 MINGW64" instead!
-MSYS2 has a package management system, [pacman][pacman].
+Once installed, you should run the "MSYS2 MinGW 64-bit shell" from the start menu (the one that runs `mingw64.exe`).
+Do not run "MSYS2 MSYS" instead!
+MSYS2 has a package management system, [pacman][pacman], which is used in Arch Linux.

 Here are the commands to install all dependencies needed to compile Lean on your machine.

 ```bash
-pacman -S make python mingw-w64-clang-x86_64-cmake mingw-w64-clang-x86_64-clang mingw-w64-clang-x86_64-ccache mingw-w64-clang-x86_64-libuv mingw-w64-clang-x86_64-gmp git unzip diffutils binutils
+pacman -S make python mingw-w64-x86_64-cmake mingw-w64-x86_64-clang mingw-w64-x86_64-ccache mingw-w64-x86_64-libuv mingw-w64-x86_64-gmp git unzip diffutils binutils
 ```

 You should now be able to run these commands:
@@ -61,7 +61,8 @@ If you want a version that can run independently of your MSYS install
 then you need to copy the following dependent DLL's from where ever
 they are installed in your MSYS setup:

- libc++.dll
+- libgcc_s_seh-1.dll
+- libstdc++-6.dll
 - libgmp-10.dll
 - libuv-1.dll
 - libwinpthread-1.dll
@@ -81,6 +82,6 @@ version clang to your path.

 **-bash: gcc: command not found**

-Make sure `/clang64/bin` is in your PATH environment.  If it is not then
-check you launched the MSYS2 CLANG64 shell from the start menu.
-(The one that runs `clang64.exe`).
+Make sure `/mingw64/bin` is in your PATH environment.  If it is not then
+check you launched the MSYS2 MinGW 64-bit shell from the start menu.
+(The one that runs `mingw64.exe`).
--- a/flake.nix
+++ b/flake.nix
@@ -39,19 +39,7 @@
          CTEST_OUTPUT_ON_FAILURE = 1;
        } // pkgs.lib.optionalAttrs pkgs.stdenv.isLinux {
          GMP = pkgsDist.gmp.override { withStatic = true; };
-          LIBUV = pkgsDist.libuv.overrideAttrs (attrs: {
-            configureFlags = ["--enable-static"];
-            hardeningDisable = [ "stackprotector" ];
-            # Sync version with CMakeLists.txt
-            version = "1.48.0";
-            src = pkgs.fetchFromGitHub {
-              owner = "libuv";
-              repo = "libuv";
-              rev = "v1.48.0";
-              sha256 = "100nj16fg8922qg4m2hdjh62zv4p32wyrllsvqr659hdhjc03bsk";
-            };
-            doCheck = false;
-          });
+          LIBUV = pkgsDist.libuv.overrideAttrs (attrs: { configureFlags = ["--enable-static"]; });
          GLIBC = pkgsDist.glibc;
          GLIBC_DEV = pkgsDist.glibc.dev;
          GCC_LIB = pkgsDist.gcc.cc.lib;
--- a/releases_drafts/hashmap.md
+++ b/releases_drafts/hashmap.md
@@ -0,0 +1,3 @@
+* The `Lean` module has switched from `Lean.HashMap` and `Lean.HashSet` to `Std.HashMap` and `Std.HashSet`. `Lean.HashMap` and `Lean.HashSet` are now deprecated and will be removed in a future release. Users of `Lean` APIs that interact with hash maps, for example `Lean.Environment.const2ModIdx`, might encounter minor breakage due to the following breaking changes from `Lean.HashMap` to `Std.HashMap`:
+    * query functions use the term `get` instead of `find`,
+    * the notation `map[key]` no longer returns an optional value but expects a proof that the key is present in the map instead. The previous behavior is available via the `map[key]?` notation.
--- a/releases_drafts/libuv.md
+++ b/releases_drafts/libuv.md
@@ -0,0 +1 @@
+* #4963 [LibUV](https://libuv.org/) is now required to build Lean. This change only affects developers who compile Lean themselves instead of obtaining toolchains via `elan`. We have updated the official build instructions with information on how to obtain LibUV on our supported platforms.
--- a/script/prepare-llvm-linux.sh
+++ b/script/prepare-llvm-linux.sh
@@ -48,8 +48,6 @@ $CP llvm-host/lib/*/lib{c++,c++abi,unwind}.* llvm-host/lib/
 $CP -r llvm/include/*-*-* llvm-host/include/
 # glibc: use for linking (so Lean programs don't embed newer symbol versions), but not for running (because libc.so, librt.so, and ld.so must be compatible)!
 $CP $GLIBC/lib/libc_nonshared.a stage1/lib/glibc
-# libpthread_nonshared.a must be linked in order to be able to use `pthread_atfork(3)`. LibUV uses this function.
-$CP $GLIBC/lib/libpthread_nonshared.a stage1/lib/glibc
 for f in $GLIBC/lib/lib{c,dl,m,rt,pthread}-*; do b=$(basename $f); cp $f stage1/lib/glibc/${b%-*}.so; done
 OPTIONS=()
 echo -n " -DLEAN_STANDALONE=ON"
@@ -64,8 +62,8 @@ fi
 # use `-nostdinc` to make sure headers are not visible by default (in particular, not to `#include_next` in the clang headers),
 # but do not change sysroot so users can still link against system libs
 echo -n " -DLEANC_INTERNAL_FLAGS='-nostdinc -isystem ROOT/include/clang' -DLEANC_CC=ROOT/bin/clang"
-echo -n " -DLEANC_INTERNAL_LINKER_FLAGS='-L ROOT/lib -L ROOT/lib/glibc ROOT/lib/glibc/libc_nonshared.a ROOT/lib/glibc/libpthread_nonshared.a -Wl,--as-needed -Wl,-Bstatic -lgmp -lunwind -luv -lpthread -ldl -lrt -Wl,-Bdynamic -Wl,--no-as-needed -fuse-ld=lld'"
+echo -n " -DLEANC_INTERNAL_LINKER_FLAGS='-L ROOT/lib -L ROOT/lib/glibc ROOT/lib/glibc/libc_nonshared.a -Wl,--as-needed -Wl,-Bstatic -lgmp -lunwind -luv -Wl,-Bdynamic -Wl,--no-as-needed -fuse-ld=lld'"
 # when not using the above flags, link GMP dynamically/as usual
-echo -n " -DLEAN_EXTRA_LINKER_FLAGS='-Wl,--as-needed -lgmp -luv -lpthread -ldl -lrt -Wl,--no-as-needed'"
+echo -n " -DLEAN_EXTRA_LINKER_FLAGS='-Wl,--as-needed -lgmp -luv -Wl,--no-as-needed'"
 # do not set `LEAN_CC` for tests
 echo -n " -DLEAN_TEST_VARS=''"
--- a/script/prepare-llvm-mingw.sh
+++ b/script/prepare-llvm-mingw.sh
@@ -31,15 +31,15 @@ cp /clang64/lib/{crtbegin,crtend,crt2,dllcrt2}.o stage1/lib/
 # runtime
 (cd llvm; cp --parents lib/clang/*/lib/*/libclang_rt.builtins* ../stage1)
 # further dependencies
-cp /clang64/lib/lib{m,bcrypt,mingw32,moldname,mingwex,msvcrt,pthread,advapi32,shell32,user32,kernel32,ucrtbase,psapi,iphlpapi,userenv,ws2_32,dbghelp,ole32}.* /clang64/lib/libgmp.a /clang64/lib/libuv.a llvm/lib/lib{c++,c++abi,unwind}.a stage1/lib/
+cp /clang64/lib/lib{m,bcrypt,mingw32,moldname,mingwex,msvcrt,pthread,advapi32,shell32,user32,kernel32,ucrtbase}.* /clang64/lib/libgmp.a /clang64/lib/libuv.a llvm/lib/lib{c++,c++abi,unwind}.a stage1/lib/
 echo -n " -DLEAN_STANDALONE=ON"
 echo -n " -DCMAKE_C_COMPILER=$PWD/stage1/bin/clang.exe -DCMAKE_C_COMPILER_WORKS=1 -DCMAKE_CXX_COMPILER=$PWD/llvm/bin/clang++.exe -DCMAKE_CXX_COMPILER_WORKS=1 -DLEAN_CXX_STDLIB='-lc++ -lc++abi'"
 echo -n " -DSTAGE0_CMAKE_C_COMPILER=clang -DSTAGE0_CMAKE_CXX_COMPILER=clang++"
 echo -n " -DLEAN_EXTRA_CXX_FLAGS='--sysroot $PWD/llvm -idirafter /clang64/include/'"
 echo -n " -DLEANC_INTERNAL_FLAGS='--sysroot ROOT -nostdinc -isystem ROOT/include/clang' -DLEANC_CC=ROOT/bin/clang.exe"
-echo -n " -DLEANC_INTERNAL_LINKER_FLAGS='-L ROOT/lib -static-libgcc -Wl,-Bstatic -lgmp $(pkg-config --static --libs libuv) -lunwind -Wl,-Bdynamic -fuse-ld=lld'"
+echo -n " -DLEANC_INTERNAL_LINKER_FLAGS='-L ROOT/lib -static-libgcc -Wl,-Bstatic -lgmp -luv -lunwind -Wl,-Bdynamic -fuse-ld=lld'"
 # when not using the above flags, link GMP dynamically/as usual
-echo -n " -DLEAN_EXTRA_LINKER_FLAGS='-lgmp $(pkg-config --libs libuv) -lucrtbase'"
+echo -n " -DLEAN_EXTRA_LINKER_FLAGS='-lgmp -luv -lucrtbase'"
 # do not set `LEAN_CC` for tests
 echo -n " -DAUTO_THREAD_FINALIZATION=OFF -DSTAGE0_AUTO_THREAD_FINALIZATION=OFF"
 echo -n " -DLEAN_TEST_VARS=''"
--- a/src/CMakeLists.txt
+++ b/src/CMakeLists.txt
@@ -243,56 +243,11 @@ if("${USE_GMP}" MATCHES "ON")
  endif()
 endif()

-# LibUV
-if("${CMAKE_SYSTEM_NAME}" MATCHES "Emscripten")
-  # Only on WebAssembly we compile LibUV ourselves
-  set(LIBUV_EMSCRIPTEN_FLAGS "${EMSCRIPTEN_SETTINGS}")
-
-  # LibUV does not compile on WebAssembly without modifications because
-  # building LibUV on a platform requires including stub implementations
-  # for features not present on the target platform. This patch includes
-  # the minimum amount of stub implementations needed for successfully
-  # running Lean on WebAssembly and using LibUV's temporary file support.
-  # It still leaves several symbols completely undefined: uv__fs_event_close,
-  # uv__hrtime, uv__io_check_fd, uv__io_fork, uv__io_poll, uv__platform_invalidate_fd
-  # uv__platform_loop_delete, uv__platform_loop_init. Making additional
-  # LibUV features available on WebAssembly might require adapting the
-  # patch to include additional LibUV source files.
-  set(LIBUV_PATCH_IN "
-diff --git a/CMakeLists.txt b/CMakeLists.txt
-index 5e8e0166..f3b29134 100644
--- a/CMakeLists.txt
-+++ b/CMakeLists.txt
-@@ -317,6 +317,11 @@ if(CMAKE_SYSTEM_NAME STREQUAL \"GNU\")
-        src/unix/hurd.c)
- endif()
-
-+if(CMAKE_SYSTEM_NAME STREQUAL \"Emscripten\")
-+  list(APPEND uv_sources
-+       src/unix/no-proctitle.c)
-+endif()
-+
- if(CMAKE_SYSTEM_NAME STREQUAL \"Linux\")
-   list(APPEND uv_defines _GNU_SOURCE _POSIX_C_SOURCE=200112)
-   list(APPEND uv_libraries dl rt)
-")
-  string(REPLACE "\n" "\\n" LIBUV_PATCH ${LIBUV_PATCH_IN})
-
-  ExternalProject_add(libuv
-    PREFIX libuv
-    GIT_REPOSITORY https://github.com/libuv/libuv
-    # Sync version with flake.nix
-    GIT_TAG v1.48.0
-    CMAKE_ARGS -DCMAKE_BUILD_TYPE=Release -DLIBUV_BUILD_TESTS=OFF -DLIBUV_BUILD_SHARED=OFF -DCMAKE_AR=${CMAKE_AR} -DCMAKE_TOOLCHAIN_FILE=${CMAKE_TOOLCHAIN_FILE} -DCMAKE_POSITION_INDEPENDENT_CODE=ON -DCMAKE_C_FLAGS=${LIBUV_EMSCRIPTEN_FLAGS}
-	  PATCH_COMMAND git reset --hard HEAD && printf "${LIBUV_PATCH}" > patch.diff && git apply patch.diff
-    BUILD_IN_SOURCE ON
-    INSTALL_COMMAND "")
-  set(LIBUV_INCLUDE_DIR "${CMAKE_BINARY_DIR}/libuv/src/libuv/include")
-  set(LIBUV_LIBRARIES "${CMAKE_BINARY_DIR}/libuv/src/libuv/libuv.a")
-else()
+if(NOT "${CMAKE_SYSTEM_NAME}" MATCHES "Emscripten")
+  # LibUV
  find_package(LibUV 1.0.0 REQUIRED)
+  include_directories(${LIBUV_INCLUDE_DIR})
 endif()
-include_directories(${LIBUV_INCLUDE_DIR})
 if(NOT LEAN_STANDALONE)
  string(APPEND LEAN_EXTRA_LINKER_FLAGS " ${LIBUV_LIBRARIES}")
 endif()
@@ -567,10 +522,6 @@ if(${STAGE} GREATER 1)
  endif()
 else()
  add_subdirectory(runtime)
-  if("${CMAKE_SYSTEM_NAME}" MATCHES "Emscripten")
-    add_dependencies(leanrt libuv)
-    add_dependencies(leanrt_initial-exec libuv)
-  endif()

  add_subdirectory(util)
  set(LEAN_OBJS ${LEAN_OBJS} $<TARGET_OBJECTS:util>)
@@ -611,10 +562,7 @@ if (${CMAKE_SYSTEM_NAME} MATCHES "Emscripten")
  # simple. (And we are not interested in `Lake` anyway.) To use dynamic
  # linking, we would probably have to set MAIN_MODULE=2 on `leanshared`,
  # SIDE_MODULE=2 on `lean`, and set CMAKE_SHARED_LIBRARY_SUFFIX to ".js".
-  # We set `ERROR_ON_UNDEFINED_SYMBOLS=0` because our build of LibUV does not
-  # define all symbols, see the comment about LibUV on WebAssembly further up
-  # in this file.
-  string(APPEND LEAN_EXE_LINKER_FLAGS " ${LIB}/temp/libleanshell.a ${TOOLCHAIN_STATIC_LINKER_FLAGS} ${EMSCRIPTEN_SETTINGS} -lnodefs.js -s EXIT_RUNTIME=1 -s MAIN_MODULE=1 -s LINKABLE=1 -s EXPORT_ALL=1 -s ERROR_ON_UNDEFINED_SYMBOLS=0")
+  string(APPEND LEAN_EXE_LINKER_FLAGS " ${LIB}/temp/libleanshell.a ${TOOLCHAIN_STATIC_LINKER_FLAGS} ${EMSCRIPTEN_SETTINGS} -lnodefs.js -s EXIT_RUNTIME=1 -s MAIN_MODULE=1 -s LINKABLE=1 -s EXPORT_ALL=1")
 endif()

 # Build the compiler using the bootstrapped C sources for stage0, and use
--- a/src/Init/Classical.lean
+++ b/src/Init/Classical.lean
@@ -80,8 +80,6 @@ noncomputable scoped instance (priority := low) propDecidable (a : Prop) : Decid
 noncomputable def decidableInhabited (a : Prop) : Inhabited (Decidable a) where
  default := inferInstance

-instance (a : Prop) : Nonempty (Decidable a) := ⟨propDecidable a⟩
-
 noncomputable def typeDecidableEq (α : Sort u) : DecidableEq α :=
  fun _ _ => inferInstance

--- a/src/Init/Control/Lawful/Basic.lean
+++ b/src/Init/Control/Lawful/Basic.lean
@@ -33,10 +33,6 @@ attribute [simp] id_map
@[simp] theorem id_map' [Functor m] [LawfulFunctor m] (x : m α) : (fun a => a) <$> x = x :=
  id_map x

-@[simp] theorem Functor.map_map [Functor f] [LawfulFunctor f] (m : α → β) (g : β → γ) (x : f α) :
-    g <$> m <$> x = (fun a => g (m a)) <$> x :=
-  (comp_map _ _ _).symm
-
 /--
 The `Applicative` typeclass only contains the operations of an applicative functor.
 `LawfulApplicative` further asserts that these operations satisfy the laws of an applicative functor:
@@ -87,16 +83,12 @@ class LawfulMonad (m : Type u → Type v) [Monad m] extends LawfulApplicative m
  seq_assoc x g h := (by simp [← bind_pure_comp, ← bind_map, bind_assoc, pure_bind])

 export LawfulMonad (bind_pure_comp bind_map pure_bind bind_assoc)
-attribute [simp] pure_bind bind_assoc bind_pure_comp
+attribute [simp] pure_bind bind_assoc

@[simp] theorem bind_pure [Monad m] [LawfulMonad m] (x : m α) : x >>= pure = x := by
  show x >>= (fun a => pure (id a)) = x
  rw [bind_pure_comp, id_map]

-/--
-Use `simp [← bind_pure_comp]` rather than `simp [map_eq_pure_bind]`,
-as `bind_pure_comp` is in the default simp set, so also using `map_eq_pure_bind` would cause a loop.
-/
 theorem map_eq_pure_bind [Monad m] [LawfulMonad m] (f : α → β) (x : m α) : f <$> x = x >>= fun a => pure (f a) := by
  rw [← bind_pure_comp]

@@ -117,24 +109,10 @@ theorem seq_eq_bind {α β : Type u} [Monad m] [LawfulMonad m] (mf : m (α →

 theorem seqRight_eq_bind [Monad m] [LawfulMonad m] (x : m α) (y : m β) : x *> y = x >>= fun _ => y := by
  rw [seqRight_eq]
-  simp only [map_eq_pure_bind, const, seq_eq_bind_map, bind_assoc, pure_bind, id_eq, bind_pure]
+  simp [map_eq_pure_bind, seq_eq_bind_map, const]

 theorem seqLeft_eq_bind [Monad m] [LawfulMonad m] (x : m α) (y : m β) : x <* y = x >>= fun a => y >>= fun _ => pure a := by
-  rw [seqLeft_eq]
-  simp only [map_eq_pure_bind, seq_eq_bind_map, bind_assoc, pure_bind, const_apply]
-
-@[simp] theorem map_bind [Monad m] [LawfulMonad m] (f : β → γ) (x : m α) (g : α → m β) :
-    f <$> (x >>= g) = x >>= fun a => f <$> g a := by
-  rw [← bind_pure_comp, LawfulMonad.bind_assoc]
-  simp [bind_pure_comp]
-
-@[simp] theorem bind_map_left [Monad m] [LawfulMonad m] (f : α → β) (x : m α) (g : β → m γ) :
-    ((f <$> x) >>= fun b => g b) = (x >>= fun a => g (f a)) := by
-  rw [← bind_pure_comp]
-  simp only [bind_assoc, pure_bind]
-
-@[simp] theorem Functor.map_unit [Monad m] [LawfulMonad m] {a : m PUnit} : (fun _ => PUnit.unit) <$> a = a := by
-  simp [map]
+  rw [seqLeft_eq]; simp [map_eq_pure_bind, seq_eq_bind_map]

 /--
 An alternative constructor for `LawfulMonad` which has more
@@ -183,9 +161,9 @@ end Id

 instance : LawfulMonad Option := LawfulMonad.mk'
  (id_map := fun x => by cases x <;> rfl)
-  (pure_bind := fun _ _ => rfl)
-  (bind_assoc := fun x _ _ => by cases x <;> rfl)
-  (bind_pure_comp := fun _ x => by cases x <;> rfl)
+  (pure_bind := fun x f => rfl)
+  (bind_assoc := fun x f g => by cases x <;> rfl)
+  (bind_pure_comp := fun f x => by cases x <;> rfl)

 instance : LawfulApplicative Option := inferInstance
 instance : LawfulFunctor Option := inferInstance
--- a/src/Init/Control/Lawful/Instances.lean
+++ b/src/Init/Control/Lawful/Instances.lean
@@ -25,7 +25,7 @@ theorem ext {x y : ExceptT ε m α} (h : x.run = y.run) : x = y := by
@[simp] theorem run_throw [Monad m] : run (throw e : ExceptT ε m β) = pure (Except.error e) := rfl

@[simp] theorem run_bind_lift [Monad m] [LawfulMonad m] (x : m α) (f : α → ExceptT ε m β) : run (ExceptT.lift x >>= f : ExceptT ε m β) = x >>= fun a => run (f a) := by
-  simp [ExceptT.run, ExceptT.lift, bind, ExceptT.bind, ExceptT.mk, ExceptT.bindCont]
+  simp[ExceptT.run, ExceptT.lift, bind, ExceptT.bind, ExceptT.mk, ExceptT.bindCont, map_eq_pure_bind]

@[simp] theorem bind_throw [Monad m] [LawfulMonad m] (f : α → ExceptT ε m β) : (throw e >>= f) = throw e := by
  simp [throw, throwThe, MonadExceptOf.throw, bind, ExceptT.bind, ExceptT.bindCont, ExceptT.mk]
@@ -43,7 +43,7 @@ theorem run_bind [Monad m] (x : ExceptT ε m α)

@[simp] theorem run_map [Monad m] [LawfulMonad m] (f : α → β) (x : ExceptT ε m α)
    : (f <$> x).run = Except.map f <$> x.run := by
-  simp [Functor.map, ExceptT.map, ←bind_pure_comp]
+  simp [Functor.map, ExceptT.map, map_eq_pure_bind]
  apply bind_congr
  intro a; cases a <;> simp [Except.map]

@@ -62,7 +62,7 @@ protected theorem seqLeft_eq {α β ε : Type u} {m : Type u → Type v} [Monad
  intro
  | Except.error _ => simp
  | Except.ok _ =>
-    simp [←bind_pure_comp]; apply bind_congr; intro b;
+    simp [map_eq_pure_bind]; apply bind_congr; intro b;
    cases b <;> simp [comp, Except.map, const]

 protected theorem seqRight_eq [Monad m] [LawfulMonad m] (x : ExceptT ε m α) (y : ExceptT ε m β) : x *> y = const α id <$> x <*> y := by
@@ -84,19 +84,14 @@ instance [Monad m] [LawfulMonad m] : LawfulMonad (ExceptT ε m) where
  pure_bind      := by intros; apply ext; simp [run_bind]
  bind_assoc     := by intros; apply ext; simp [run_bind]; apply bind_congr; intro a; cases a <;> simp

-@[simp] theorem map_throw [Monad m] [LawfulMonad m] {α β : Type _} (f : α → β) (e : ε) :
-    f <$> (throw e : ExceptT ε m α) = (throw e : ExceptT ε m β) := by
-  simp only [ExceptT.instMonad, ExceptT.map, ExceptT.mk, throw, throwThe, MonadExceptOf.throw,
-    pure_bind]
-
 end ExceptT

 /-! # Except -/

 instance : LawfulMonad (Except ε) := LawfulMonad.mk'
  (id_map := fun x => by cases x <;> rfl)
-  (pure_bind := fun _ _ => rfl)
-  (bind_assoc := fun a _ _ => by cases a <;> rfl)
+  (pure_bind := fun a f => rfl)
+  (bind_assoc := fun a f g => by cases a <;> rfl)

 instance : LawfulApplicative (Except ε) := inferInstance
 instance : LawfulFunctor (Except ε) := inferInstance
@@ -180,7 +175,7 @@ theorem ext {x y : StateT σ m α} (h : ∀ s, x.run s = y.run s) : x = y :=
  simp [bind, StateT.bind, run]

@[simp] theorem run_map {α β σ : Type u} [Monad m] [LawfulMonad m] (f : α → β) (x : StateT σ m α) (s : σ) : (f <$> x).run s = (fun (p : α × σ) => (f p.1, p.2)) <$> x.run s := by
-  simp [Functor.map, StateT.map, run, ←bind_pure_comp]
+  simp [Functor.map, StateT.map, run, map_eq_pure_bind]

@[simp] theorem run_get [Monad m] (s : σ)    : (get : StateT σ m σ).run s = pure (s, s) := rfl

@@ -215,13 +210,13 @@ theorem run_bind_lift {α σ : Type u} [Monad m] [LawfulMonad m] (x : m α) (f :

 theorem seqRight_eq [Monad m] [LawfulMonad m] (x : StateT σ m α) (y : StateT σ m β) : x *> y = const α id <$> x <*> y := by
  apply ext; intro s
-  simp [←bind_pure_comp, const]
+  simp [map_eq_pure_bind, const]
  apply bind_congr; intro p; cases p
  simp [Prod.eta]

 theorem seqLeft_eq [Monad m] [LawfulMonad m] (x : StateT σ m α) (y : StateT σ m β) : x <* y = const β <$> x <*> y := by
  apply ext; intro s
-  simp [←bind_pure_comp]
+  simp [map_eq_pure_bind]

 instance [Monad m] [LawfulMonad m] : LawfulMonad (StateT σ m) where
  id_map         := by intros; apply ext; intros; simp[Prod.eta]
@@ -229,7 +224,7 @@ instance [Monad m] [LawfulMonad m] : LawfulMonad (StateT σ m) where
  seqLeft_eq     := seqLeft_eq
  seqRight_eq    := seqRight_eq
  pure_seq       := by intros; apply ext; intros; simp
-  bind_pure_comp := by intros; apply ext; intros; simp
+  bind_pure_comp := by intros; apply ext; intros; simp; apply LawfulMonad.bind_pure_comp
  bind_map       := by intros; rfl
  pure_bind      := by intros; apply ext; intros; simp
  bind_assoc     := by intros; apply ext; intros; simp
--- a/src/Init/Core.lean
+++ b/src/Init/Core.lean
@@ -823,7 +823,6 @@ theorem iff_iff_implies_and_implies {a b : Prop} : (a ↔ b) ↔ (a → b) ∧ (
 protected theorem Iff.rfl {a : Prop} : a ↔ a :=
  Iff.refl a

-- And, also for backward compatibility, we try `Iff.rfl.` using `exact` (see #5366)
 macro_rules | `(tactic| rfl) => `(tactic| exact Iff.rfl)

 theorem Iff.of_eq (h : a = b) : a ↔ b := h ▸ Iff.rfl
@@ -838,9 +837,6 @@ instance : Trans Iff Iff Iff where
 theorem Eq.comm {a b : α} : a = b ↔ b = a := Iff.intro Eq.symm Eq.symm
 theorem eq_comm {a b : α} : a = b ↔ b = a := Eq.comm

-theorem HEq.comm {a : α} {b : β} : HEq a b ↔ HEq b a := Iff.intro HEq.symm HEq.symm
-theorem heq_comm {a : α} {b : β} : HEq a b ↔ HEq b a := HEq.comm
-
@[symm] theorem Iff.symm (h : a ↔ b) : b ↔ a := Iff.intro h.mpr h.mp
 theorem Iff.comm: (a ↔ b) ↔ (b ↔ a) := Iff.intro Iff.symm Iff.symm
 theorem iff_comm : (a ↔ b) ↔ (b ↔ a) := Iff.comm
@@ -1864,8 +1860,7 @@ section
 variable {α : Type u}
 variable (r : α → α → Prop)

-instance Quotient.decidableEq {α : Sort u} {s : Setoid α} [d : ∀ (a b : α), Decidable (a ≈ b)]
-    : DecidableEq (Quotient s) :=
+instance {α : Sort u} {s : Setoid α} [d : ∀ (a b : α), Decidable (a ≈ b)] : DecidableEq (Quotient s) :=
  fun (q₁ q₂ : Quotient s) =>
    Quotient.recOnSubsingleton₂ q₁ q₂
      fun a₁ a₂ =>
--- a/src/Init/Data.lean
+++ b/src/Init/Data.lean
@@ -40,4 +40,3 @@ import Init.Data.ULift
 import Init.Data.PLift
 import Init.Data.Zero
 import Init.Data.NeZero
-import Init.Data.Function
--- a/src/Init/Data/Array/Attach.lean
+++ b/src/Init/Data/Array/Attach.lean
@@ -5,7 +5,6 @@ Authors: Joachim Breitner, Mario Carneiro
 -/
 prelude
 import Init.Data.Array.Mem
-import Init.Data.Array.Lemmas
 import Init.Data.List.Attach

 namespace Array
@@ -27,152 +26,4 @@ Unsafe implementation of `attachWith`, taking advantage of the fact that the rep
  with the same elements but in the type `{x // x ∈ xs}`. -/
@[inline] def attach (xs : Array α) : Array {x // x ∈ xs} := xs.attachWith _ fun _ => id

-@[simp] theorem _root_.List.attachWith_toArray {l : List α} {P : α → Prop} {H : ∀ x ∈ l.toArray, P x} :
-    l.toArray.attachWith P H = (l.attachWith P (by simpa using H)).toArray := by
-  simp [attachWith]
-
-@[simp] theorem _root_.List.attach_toArray {l : List α} :
-    l.toArray.attach = (l.attachWith (· ∈ l.toArray) (by simp)).toArray := by
-  simp [attach]
-
-@[simp] theorem toList_attachWith {l : Array α} {P : α → Prop} {H : ∀ x ∈ l, P x} :
-   (l.attachWith P H).toList = l.toList.attachWith P (by simpa [mem_toList] using H) := by
-  simp [attachWith]
-
-@[simp] theorem toList_attach {α : Type _} {l : Array α} :
-    l.attach.toList = l.toList.attachWith (· ∈ l) (by simp [mem_toList]) := by
-  simp [attach]
-
-/-! ## unattach
-
-`Array.unattach` is the (one-sided) inverse of `Array.attach`. It is a synonym for `Array.map Subtype.val`.
-
-We use it by providing a simp lemma `l.attach.unattach = l`, and simp lemmas which recognize higher order
-functions applied to `l : Array { x // p x }` which only depend on the value, not the predicate, and rewrite these
-in terms of a simpler function applied to `l.unattach`.
-
-Further, we provide simp lemmas that push `unattach` inwards.
-/
-
-/--
-A synonym for `l.map (·.val)`. Mostly this should not be needed by users.
-It is introduced as in intermediate step by lemmas such as `map_subtype`,
-and is ideally subsequently simplified away by `unattach_attach`.
-
-If not, usually the right approach is `simp [Array.unattach, -Array.map_subtype]` to unfold.
-/
-def unattach {α : Type _} {p : α → Prop} (l : Array { x // p x }) := l.map (·.val)
-
-@[simp] theorem unattach_nil {p : α → Prop} : (#[] : Array { x // p x }).unattach = #[] := rfl
-@[simp] theorem unattach_push {p : α → Prop} {a : { x // p x }} {l : Array { x // p x }} :
-    (l.push a).unattach = l.unattach.push a.1 := by
-  simp only [unattach, Array.map_push]
-
-@[simp] theorem size_unattach {p : α → Prop} {l : Array { x // p x }} :
-    l.unattach.size = l.size := by
-  unfold unattach
-  simp
-
-@[simp] theorem _root_.List.unattach_toArray {p : α → Prop} {l : List { x // p x }} :
-    l.toArray.unattach = l.unattach.toArray := by
-  simp only [unattach, List.map_toArray, List.unattach]
-
-@[simp] theorem toList_unattach {p : α → Prop} {l : Array { x // p x }} :
-    l.unattach.toList = l.toList.unattach := by
-  simp only [unattach, toList_map, List.unattach]
-
-@[simp] theorem unattach_attach {l : Array α} : l.attach.unattach = l := by
-  cases l
-  simp
-
-@[simp] theorem unattach_attachWith {p : α → Prop} {l : Array α}
-    {H : ∀ a ∈ l, p a} :
-    (l.attachWith p H).unattach = l := by
-  cases l
-  simp
-
-/-! ### Recognizing higher order functions using a function that only depends on the value. -/
-
-/--
-This lemma identifies folds over arrays of subtypes, where the function only depends on the value, not the proposition,
-and simplifies these to the function directly taking the value.
-/
-theorem foldl_subtype {p : α → Prop} {l : Array { x // p x }}
-    {f : β → { x // p x } → β} {g : β → α → β} {x : β}
-    {hf : ∀ b x h, f b ⟨x, h⟩ = g b x} :
-    l.foldl f x = l.unattach.foldl g x := by
-  cases l
-  simp only [List.foldl_toArray', List.unattach_toArray]
-  rw [List.foldl_subtype] -- Why can't simp do this?
-  simp [hf]
-
-/-- Variant of `foldl_subtype` with side condition to check `stop = l.size`. -/
-@[simp] theorem foldl_subtype' {p : α → Prop} {l : Array { x // p x }}
-    {f : β → { x // p x } → β} {g : β → α → β} {x : β}
-    {hf : ∀ b x h, f b ⟨x, h⟩ = g b x} (h : stop = l.size) :
-    l.foldl f x 0 stop = l.unattach.foldl g x := by
-  subst h
-  rwa [foldl_subtype]
-
-/--
-This lemma identifies folds over arrays of subtypes, where the function only depends on the value, not the proposition,
-and simplifies these to the function directly taking the value.
-/
-theorem foldr_subtype {p : α → Prop} {l : Array { x // p x }}
-    {f : { x // p x } → β → β} {g : α → β → β} {x : β}
-    {hf : ∀ x h b, f ⟨x, h⟩ b = g x b} :
-    l.foldr f x = l.unattach.foldr g x := by
-  cases l
-  simp only [List.foldr_toArray', List.unattach_toArray]
-  rw [List.foldr_subtype]
-  simp [hf]
-
-/-- Variant of `foldr_subtype` with side condition to check `stop = l.size`. -/
-@[simp] theorem foldr_subtype' {p : α → Prop} {l : Array { x // p x }}
-    {f : { x // p x } → β → β} {g : α → β → β} {x : β}
-    {hf : ∀ x h b, f ⟨x, h⟩ b = g x b} (h : start = l.size) :
-    l.foldr f x start 0 = l.unattach.foldr g x := by
-  subst h
-  rwa [foldr_subtype]
-
-/--
-This lemma identifies maps over arrays of subtypes, where the function only depends on the value, not the proposition,
-and simplifies these to the function directly taking the value.
-/
-@[simp] theorem map_subtype {p : α → Prop} {l : Array { x // p x }}
-    {f : { x // p x } → β} {g : α → β} {hf : ∀ x h, f ⟨x, h⟩ = g x} :
-    l.map f = l.unattach.map g := by
-  cases l
-  simp only [List.map_toArray, List.unattach_toArray]
-  rw [List.map_subtype]
-  simp [hf]
-
-@[simp] theorem filterMap_subtype {p : α → Prop} {l : Array { x // p x }}
-    {f : { x // p x } → Option β} {g : α → Option β} {hf : ∀ x h, f ⟨x, h⟩ = g x} :
-    l.filterMap f = l.unattach.filterMap g := by
-  cases l
-  simp only [size_toArray, List.filterMap_toArray', List.unattach_toArray, List.length_unattach,
-    mk.injEq]
-  rw [List.filterMap_subtype]
-  simp [hf]
-
-@[simp] theorem unattach_filter {p : α → Prop} {l : Array { x // p x }}
-    {f : { x // p x } → Bool} {g : α → Bool} {hf : ∀ x h, f ⟨x, h⟩ = g x} :
-    (l.filter f).unattach = l.unattach.filter g := by
-  cases l
-  simp [hf]
-
-/-! ### Simp lemmas pushing `unattach` inwards. -/
-
-@[simp] theorem unattach_reverse {p : α → Prop} {l : Array { x // p x }} :
-    l.reverse.unattach = l.unattach.reverse := by
-  cases l
-  simp
-
-@[simp] theorem unattach_append {p : α → Prop} {l₁ l₂ : Array { x // p x }} :
-    (l₁ ++ l₂).unattach = l₁.unattach ++ l₂.unattach := by
-  cases l₁
-  cases l₂
-  simp
-
 end Array
--- a/src/Init/Data/Array/Basic.lean
+++ b/src/Init/Data/Array/Basic.lean
@@ -11,7 +11,6 @@ import Init.Data.UInt.Basic
 import Init.Data.Repr
 import Init.Data.ToString.Basic
 import Init.GetElem
-import Init.Data.List.ToArray
 universe u v w

 /-! ### Array literal syntax -/
@@ -216,7 +215,7 @@ def swapAt! (a : Array α) (i : Nat) (v : α) : α × Array α :=
  if h : i < a.size then
    swapAt a ⟨i, h⟩ v
  else
-    have : Inhabited (α × Array α) := ⟨(v, a)⟩
+    have : Inhabited α := ⟨v⟩
    panic! ("index " ++ toString i ++ " out of bounds")

 def shrink (a : Array α) (n : Nat) : Array α :=
@@ -618,7 +617,7 @@ def concatMap (f : α → Array β) (as : Array α) : Array β :=

 `flatten #[#[a₁, a₂, ⋯], #[b₁, b₂, ⋯], ⋯]` = `#[a₁, a₂, ⋯, b₁, b₂, ⋯]`
 -/
-@[inline] def flatten (as : Array (Array α)) : Array α :=
+def flatten (as : Array (Array α)) : Array α :=
  as.foldl (init := empty) fun r a => r ++ a

@[inline]
@@ -721,7 +720,7 @@ termination_by a.size - i.val
 decreasing_by simp_wf; exact Nat.sub_succ_lt_self _ _ i.isLt

 -- This is required in `Lean.Data.PersistentHashMap`.
-@[simp] theorem size_feraseIdx (a : Array α) (i : Fin a.size) : (a.feraseIdx i).size = a.size - 1 := by
+theorem size_feraseIdx (a : Array α) (i : Fin a.size) : (a.feraseIdx i).size = a.size - 1 := by
  induction a, i using Array.feraseIdx.induct with
  | @case1 a i h a' _ ih =>
    unfold feraseIdx
@@ -811,27 +810,11 @@ def split (as : Array α) (p : α → Bool) : Array α × Array α :=
  as.foldl (init := (#[], #[])) fun (as, bs) a =>
    if p a then (as.push a, bs) else (as, bs.push a)

-/-! ## Auxiliary functions used in metaprogramming.
+/-! ### Auxiliary functions used in metaprogramming.

 We do not intend to provide verification theorems for these functions.
 -/

-/-! ### eraseReps -/
-
-/--
-`O(|l|)`. Erase repeated adjacent elements. Keeps the first occurrence of each run.
-* `eraseReps #[1, 3, 2, 2, 2, 3, 5] = #[1, 3, 2, 3, 5]`
-/
-def eraseReps {α} [BEq α] (as : Array α) : Array α :=
-  if h : 0 < as.size then
-    let ⟨last, r⟩ := as.foldl (init := (as[0], #[])) fun ⟨last, r⟩ a =>
-      if a == last then ⟨last, r⟩ else ⟨a, r.push last⟩
-    r.push last
-  else
-    #[]
-
-/-! ### allDiff -/
-
 private def allDiffAuxAux [BEq α] (as : Array α) (a : α) : forall (i : Nat), i < as.size → Bool
  | 0,   _ => true
  | i+1, h =>
@@ -849,8 +832,6 @@ decreasing_by simp_wf; decreasing_trivial_pre_omega
 def allDiff [BEq α] (as : Array α) : Bool :=
  allDiffAux as 0

-/-! ### getEvenElems -/
-
@[inline] def getEvenElems (as : Array α) : Array α :=
  (·.2) <| as.foldl (init := (true, Array.empty)) fun (even, r) a =>
    if even then
--- a/src/Init/Data/Array/Bootstrap.lean
+++ b/src/Init/Data/Array/Bootstrap.lean
@@ -73,7 +73,7 @@ theorem foldr_eq_foldr_toList (f : α → β → β) (init : β) (arr : Array α

@[simp] theorem append_eq_append (arr arr' : Array α) : arr.append arr' = arr ++ arr' := rfl

-@[simp] theorem toList_append (arr arr' : Array α) :
+@[simp] theorem append_toList (arr arr' : Array α) :
    (arr ++ arr').toList = arr.toList ++ arr'.toList := by
  rw [← append_eq_append]; unfold Array.append
  rw [foldl_eq_foldl_toList]
@@ -111,8 +111,8 @@ abbrev toList_eq := @toListImpl_eq
@[deprecated pop_toList (since := "2024-09-09")]
 abbrev pop_data := @pop_toList

-@[deprecated toList_append (since := "2024-09-09")]
-abbrev append_data := @toList_append
+@[deprecated append_toList (since := "2024-09-09")]
+abbrev append_data := @append_toList

@[deprecated appendList_toList (since := "2024-09-09")]
 abbrev appendList_data := @appendList_toList
--- a/src/Init/Data/Array/Lemmas.lean
+++ b/src/Init/Data/Array/Lemmas.lean
--- a/src/Init/Data/Array/QSort.lean
+++ b/src/Init/Data/Array/QSort.lean
@@ -5,7 +5,6 @@ Authors: Leonardo de Moura
 -/
 prelude
 import Init.Data.Array.Basic
-import Init.Data.Ord

 namespace Array
 -- TODO: remove the [Inhabited α] parameters as soon as we have the tactic framework for automating proof generation and using Array.fget
@@ -45,11 +44,4 @@ def qpartition (as : Array α) (lt : α → α → Bool) (lo hi : Nat) : Nat ×
    else as
  sort as low high

-set_option linter.unusedVariables.funArgs false in
-/--
-Sort an array using `compare` to compare elements.
-/
-def qsortOrd [ord : Ord α] (xs : Array α) : Array α :=
-  xs.qsort fun x y => compare x y |>.isLT
-
 end Array
--- a/src/Init/Data/Array/Subarray.lean
+++ b/src/Init/Data/Array/Subarray.lean
@@ -59,22 +59,6 @@ def popFront (s : Subarray α) : Subarray α :=
  else
    s

-/--
-The empty subarray.
-/
-protected def empty : Subarray α where
-  array := #[]
-  start := 0
-  stop := 0
-  start_le_stop := Nat.le_refl 0
-  stop_le_array_size := Nat.le_refl 0
-
-instance : EmptyCollection (Subarray α) :=
-  ⟨Subarray.empty⟩
-
-instance : Inhabited (Subarray α) :=
-  ⟨{}⟩
-
@[inline] unsafe def forInUnsafe {α : Type u} {β : Type v} {m : Type v → Type w} [Monad m] (s : Subarray α) (b : β) (f : α → β → m (ForInStep β)) : m β :=
  let sz := USize.ofNat s.stop
  let rec @[specialize] loop (i : USize) (b : β) : m β := do
--- a/src/Init/Data/Array/TakeDrop.lean
+++ b/src/Init/Data/Array/TakeDrop.lean
@@ -12,7 +12,7 @@ namespace Array
 theorem exists_of_uset (self : Array α) (i d h) :
    ∃ l₁ l₂, self.toList = l₁ ++ self[i] :: l₂ ∧ List.length l₁ = i.toNat ∧
      (self.uset i d h).toList = l₁ ++ d :: l₂ := by
-  simpa only [ugetElem_eq_getElem, getElem_eq_getElem_toList, uset, toList_set] using
+  simpa only [ugetElem_eq_getElem, getElem_eq_toList_getElem, uset, toList_set] using
    List.exists_of_set _

 end Array
--- a/src/Init/Data/BitVec/Basic.lean
+++ b/src/Init/Data/BitVec/Basic.lean
@@ -1,7 +1,7 @@
 /-
 Copyright (c) 2024 Lean FRO, LLC. All rights reserved.
 Released under Apache 2.0 license as described in the file LICENSE.
-Authors: Joe Hendrix, Wojciech Nawrocki, Leonardo de Moura, Mario Carneiro, Alex Keizer, Harun Khan, Abdalrhman M Mohamed, Siddharth Bhat
+Authors: Joe Hendrix, Wojciech Nawrocki, Leonardo de Moura, Mario Carneiro, Alex Keizer, Harun Khan, Abdalrhman M Mohamed
 -/
 prelude
 import Init.Data.Fin.Basic
@@ -269,8 +269,8 @@ Return the absolute value of a signed bitvector.
 protected def abs (x : BitVec n) : BitVec n := if x.msb then .neg x else x

 /--
-Multiplication for bit vectors. This can be interpreted as either signed or unsigned
-multiplication modulo `2^n`.
+Multiplication for bit vectors. This can be interpreted as either signed or unsigned negation
+modulo `2^n`.

 SMT-Lib name: `bvmul`.
 -/
@@ -676,13 +676,6 @@ result of appending a single bit to the front in the naive implementation).
    That is, the new bit is the least significant bit. -/
 def concat {n} (msbs : BitVec n) (lsb : Bool) : BitVec (n+1) := msbs ++ (ofBool lsb)

-/--
-`x.shiftConcat b` shifts all bits of `x` to the left by `1` and sets the least significant bit to `b`.
-It is a non-dependent version of `concat` that does not change the total bitwidth.
-/
-def shiftConcat (x : BitVec n) (b : Bool) : BitVec n :=
-  (x.concat b).truncate n
-
 /-- Prepend a single bit to the front of a bitvector, using big endian order (see `append`).
    That is, the new bit is the most significant bit. -/
 def cons {n} (msb : Bool) (lsbs : BitVec n) : BitVec (n+1) :=
@@ -718,8 +711,6 @@ section normalization_eqs
@[simp] theorem add_eq (x y : BitVec w)                   : BitVec.add x y = x + y            := rfl
@[simp] theorem sub_eq (x y : BitVec w)                   : BitVec.sub x y = x - y            := rfl
@[simp] theorem mul_eq (x y : BitVec w)                   : BitVec.mul x y = x * y            := rfl
-@[simp] theorem udiv_eq (x y : BitVec w)                  : BitVec.udiv x y = x / y           := rfl
-@[simp] theorem umod_eq (x y : BitVec w)                  : BitVec.umod x y = x % y           := rfl
@[simp] theorem zero_eq                                   : BitVec.zero n = 0#n               := rfl
 end normalization_eqs

--- a/src/Init/Data/BitVec/Bitblast.lean
+++ b/src/Init/Data/BitVec/Bitblast.lean
@@ -1,7 +1,7 @@
 /-
 Copyright (c) 2024 Lean FRO, LLC. All rights reserved.
 Released under Apache 2.0 license as described in the file LICENSE.
-Authors: Harun Khan, Abdalrhman M Mohamed, Joe Hendrix, Siddharth Bhat
+Authors: Harun Khan, Abdalrhman M Mohamed, Joe Hendrix
 -/
 prelude
 import Init.Data.BitVec.Folds
@@ -18,80 +18,6 @@ as vectors of bits into proofs about Lean `BitVec` values.
 The module is named for the bit-blasting operation in an SMT solver that converts bitvector
 expressions into expressions about individual bits in each vector.

-### Example: How bitblasting works for multiplication
-
-We explain how the lemmas here are used for bitblasting,
-by using multiplication as a prototypical example.
-Other bitblasters for other operations follow the same pattern.
-To bitblast a multiplication of the form `x * y`,
-we must unfold the above into a form that the SAT solver understands.
-
-We assume that the solver already knows how to bitblast addition.
-This is known to `bv_decide`, by exploiting the lemma `add_eq_adc`,
-which says that `x + y : BitVec w` equals `(adc x y false).2`,
-where `adc` builds an add-carry circuit in terms of the primitive operations
-(bitwise and, bitwise or, bitwise xor) that bv_decide already understands.
-In this way, we layer bitblasters on top of each other,
-by reducing the multiplication bitblaster to an addition operation.
-
-The core lemma is given by `getLsbD_mul`:
-
-```lean
- x y : BitVec w ⊢ (x * y).getLsbD i = (mulRec x y w).getLsbD i
-```
-
-Which says that the `i`th bit of `x * y` can be obtained by
-evaluating the `i`th bit of `(mulRec x y w)`.
-Once again, we assume that `bv_decide` knows how to implement `getLsbD`,
-given that `mulRec` can be understood by `bv_decide`.
-
-We write two lemmas to enable `bv_decide` to unfold `(mulRec x y w)`
-into a complete circuit, **when `w` is a known constant**`.
-This is given by two recurrence lemmas, `mulRec_zero_eq` and `mulRec_succ_eq`,
-which are applied repeatedly when the width is `0` and when the width is `w' + 1`:
-
-```lean
-mulRec_zero_eq :
-    mulRec x y 0 =
-      if y.getLsbD 0 then x else 0
-
-mulRec_succ_eq
-    mulRec x y (s + 1) =
-      mulRec x y s +
-      if y.getLsbD (s + 1) then (x <<< (s + 1)) else 0 := rfl
-```
-
-By repeatedly applying the lemmas `mulRec_zero_eq` and `mulRec_succ_eq`,
-one obtains a circuit for multiplication.
-Note that this circuit uses `BitVec.add`, `BitVec.getLsbD`, `BitVec.shiftLeft`.
-Here, `BitVec.add` and `BitVec.shiftLeft` are (recursively) bitblasted by `bv_decide`,
-using the lemmas `add_eq_adc` and `shiftLeft_eq_shiftLeftRec`,
-and `BitVec.getLsbD` is a primitive that `bv_decide` knows how to reduce to SAT.
-
-The two lemmas, `mulRec_zero_eq`, and `mulRec_succ_eq`,
-are used in `Std.Tactic.BVDecide.BVExpr.bitblast.blastMul`
-to prove the correctness of the circuit that is built by `bv_decide`.
-
-```lean
-def blastMul (aig : AIG BVBit) (input : AIG.BinaryRefVec aig w) : AIG.RefVecEntry BVBit w
-theorem denote_blastMul (aig : AIG BVBit) (lhs rhs : BitVec w) (assign : Assignment) :
-   ...
-   ⟦(blastMul aig input).aig, (blastMul aig input).vec.get idx hidx, assign.toAIGAssignment⟧
-     =
-   (lhs * rhs).getLsbD idx
-```
-
-The definition and theorem above are internal to `bv_decide`,
-and use `mulRec_{zero,succ}_eq` to prove that the circuit built by `bv_decide`
-computes the correct value for multiplication.
-
-To zoom out, therefore, we follow two steps:
-First, we prove bitvector lemmas to unfold a high-level operation (such as multiplication)
-into already bitblastable operations (such as addition and left shift).
-We then use these lemmas to prove the correctness of the circuit that `bv_decide` builds.
-
-We use this workflow to implement bitblasting for all SMT-LIB2 operations.
-
 ## Main results
 * `x + y : BitVec w` is `(adc x y false).2`.

@@ -238,17 +164,6 @@ theorem getLsbD_add {i : Nat} (i_lt : i < w) (x y : BitVec w) :
      (getLsbD x i ^^ (getLsbD y i ^^ carry i x y false)) := by
  simpa using getLsbD_add_add_bool i_lt x y false

-theorem getElem_add_add_bool {i : Nat} (i_lt : i < w) (x y : BitVec w) (c : Bool) :
-    (x + y + setWidth w (ofBool c))[i] =
-      (x[i] ^^ (y[i] ^^ carry i x y c)) := by
-  simp only [← getLsbD_eq_getElem]
-  rw [getLsbD_add_add_bool]
-  omega
-
-theorem getElem_add {i : Nat} (i_lt : i < w) (x y : BitVec w) :
-    (x + y)[i] = (x[i] ^^ (y[i] ^^ carry i x y false)) := by
-  simpa using getElem_add_add_bool i_lt x y false
-
 theorem adc_spec (x y : BitVec w) (c : Bool) :
    adc x y c = (carry w x y c, x + y + setWidth w (ofBool c)) := by
  simp only [adc]
@@ -453,10 +368,6 @@ theorem getLsbD_mul (x y : BitVec w) (i : Nat) :
  · simp
  · omega

-theorem getElem_mul {x y : BitVec w} {i : Nat} (h : i < w) :
-    (x * y)[i] = (mulRec x y w)[i] := by
-  simp [mulRec_eq_mul_signExtend_setWidth]
-
 /-! ## shiftLeft recurrence for bitblasting -/

 /--
@@ -527,385 +438,6 @@ theorem shiftLeft_eq_shiftLeftRec (x : BitVec w₁) (y : BitVec w₂) :
  · simp [of_length_zero]
  · simp [shiftLeftRec_eq]

-/-! # udiv/urem recurrence for bitblasting
-
-In order to prove the correctness of the division algorithm on the integers,
-one shows that `n.div d = q` and `n.mod d = r` iff `n = d * q + r` and `0 ≤ r < d`.
-Mnemonic: `n` is the numerator, `d` is the denominator, `q` is the quotient, and `r` the remainder.
-
-This *uniqueness of decomposition* is not true for bitvectors.
-For `n = 0, d = 3, w = 3`, we can write:
- `0 = 0 * 3 + 0` (`q = 0`, `r = 0 < 3`.)
- `0 = 2 * 3 + 2 = 6 + 2 ≃ 0 (mod 8)` (`q = 2`, `r = 2 < 3`).
-
-Such examples can be created by choosing different `(q, r)` for a fixed `(d, n)`
-such that `(d * q + r)` overflows and wraps around to equal `n`.
-
-This tells us that the division algorithm must have more restrictions than just the ones
-we have for integers. These restrictions are captured in `DivModState.Lawful`.
-The key idea is to state the relationship in terms of the toNat values of {n, d, q, r}.
-If the division equation `d.toNat * q.toNat + r.toNat = n.toNat` holds,
-then `n.udiv d = q` and `n.umod d = r`.
-
-Following this, we implement the division algorithm by repeated shift-subtract.
-
-References:
- Fast 32-bit Division on the DSP56800E: Minimized nonrestoring division algorithm by David Baca
- Bitwuzla sources for bitblasting.h
-/
-
-private theorem Nat.div_add_eq_left_of_lt {x y z : Nat} (hx : z ∣ x) (hy : y < z) (hz : 0 < z) :
-    (x + y) / z = x / z := by
-  refine Nat.div_eq_of_lt_le ?lo ?hi
-  · apply Nat.le_trans
-    · exact div_mul_le_self x z
-    · omega
-  · simp only [succ_eq_add_one, Nat.add_mul, Nat.one_mul]
-    apply Nat.add_lt_add_of_le_of_lt
-    · apply Nat.le_of_eq
-      exact (Nat.div_eq_iff_eq_mul_left hz hx).mp rfl
-    · exact hy
-
-/-- If the division equation `d.toNat * q.toNat + r.toNat = n.toNat` holds,
-then `n.udiv d = q`. -/
-theorem udiv_eq_of_mul_add_toNat {d n q r : BitVec w} (hd : 0 < d)
-    (hrd : r < d)
-    (hdqnr : d.toNat * q.toNat + r.toNat = n.toNat) :
-    n / d = q := by
-  apply BitVec.eq_of_toNat_eq
-  rw [toNat_udiv]
-  replace hdqnr : (d.toNat * q.toNat + r.toNat) / d.toNat = n.toNat / d.toNat := by
-    simp [hdqnr]
-  rw [Nat.div_add_eq_left_of_lt] at hdqnr
-  · rw [← hdqnr]
-    exact mul_div_right q.toNat hd
-  · exact Nat.dvd_mul_right d.toNat q.toNat
-  · exact hrd
-  · exact hd
-
-/-- If the division equation `d.toNat * q.toNat + r.toNat = n.toNat` holds,
-then `n.umod d = r`. -/
-theorem umod_eq_of_mul_add_toNat {d n q r : BitVec w} (hrd : r < d)
-    (hdqnr : d.toNat * q.toNat + r.toNat = n.toNat) :
-    n % d = r := by
-  apply BitVec.eq_of_toNat_eq
-  rw [toNat_umod]
-  replace hdqnr : (d.toNat * q.toNat + r.toNat) % d.toNat = n.toNat % d.toNat := by
-    simp [hdqnr]
-  rw [Nat.add_mod, Nat.mul_mod_right] at hdqnr
-  simp only [Nat.zero_add, mod_mod] at hdqnr
-  replace hrd : r.toNat < d.toNat := by
-    simpa [BitVec.lt_def] using hrd
-  rw [Nat.mod_eq_of_lt hrd] at hdqnr
-  simp [hdqnr]
-
-/-! ### DivModState -/
-
-/-- `DivModState` is a structure that maintains the state of recursive `divrem` calls. -/
-structure DivModState (w : Nat) : Type where
-  /-- The number of bits in the numerator that are not yet processed -/
-  wn : Nat
-  /-- The number of bits in the remainder (and quotient) -/
-  wr : Nat
-  /-- The current quotient. -/
-  q : BitVec w
-  /-- The current remainder. -/
-  r : BitVec w
-
-
-/-- `DivModArgs` contains the arguments to a `divrem` call which remain constant throughout
-execution. -/
-structure DivModArgs (w : Nat) where
-  /-- the numerator (aka, dividend) -/
-  n : BitVec w
-  /-- the denumerator (aka, divisor)-/
-  d : BitVec w
-
-/-- A `DivModState` is lawful if the remainder width `wr` plus the numerator width `wn` equals `w`,
-and the bitvectors `r` and `n` have values in the bounds given by bitwidths `wr`, resp. `wn`.
-
-This is a proof engineering choice: an alternative world could have been
-`r : BitVec wr` and `n : BitVec wn`, but this required much more dependent typing coercions.
-
-Instead, we choose to declare all involved bitvectors as length `w`, and then prove that
-the values are within their respective bounds.
-
-We start with `wn = w` and `wr = 0`, and then in each step, we decrement `wn` and increment `wr`.
-In this way, we grow a legal remainder in each loop iteration.
-/
-structure DivModState.Lawful {w : Nat} (args : DivModArgs w) (qr : DivModState w) : Prop where
-  /-- The sum of widths of the dividend and remainder is `w`. -/
-  hwrn : qr.wr + qr.wn = w
-  /-- The denominator is positive. -/
-  hdPos : 0 < args.d
-  /-- The remainder is strictly less than the denominator. -/
-  hrLtDivisor : qr.r.toNat < args.d.toNat
-  /-- The remainder is morally a `Bitvec wr`, and so has value less than `2^wr`. -/
-  hrWidth : qr.r.toNat < 2^qr.wr
-  /-- The quotient is morally a `Bitvec wr`, and so has value less than `2^wr`. -/
-  hqWidth : qr.q.toNat < 2^qr.wr
-  /-- The low `(w - wn)` bits of `n` obey the invariant for division. -/
-  hdiv : args.n.toNat >>> qr.wn = args.d.toNat * qr.q.toNat + qr.r.toNat
-
-/-- A lawful DivModState implies `w > 0`. -/
-def DivModState.Lawful.hw {args : DivModArgs w} {qr : DivModState w}
-    {h : DivModState.Lawful args qr} : 0 < w := by
-  have hd := h.hdPos
-  rcases w with rfl | w
-  · have hcontra : args.d = 0#0 := by apply Subsingleton.elim
-    rw [hcontra] at hd
-    simp at hd
-  · omega
-
-/-- An initial value with both `q, r = 0`. -/
-def DivModState.init (w : Nat) : DivModState w := {
-  wn := w
-  wr := 0
-  q := 0#w
-  r := 0#w
-}
-
-/-- The initial state is lawful. -/
-def DivModState.lawful_init {w : Nat} (args : DivModArgs w) (hd : 0#w < args.d) :
-    DivModState.Lawful args (DivModState.init w) := by
-  simp only [BitVec.DivModState.init]
-  exact {
-    hwrn := by simp only; omega,
-    hdPos := by assumption
-    hrLtDivisor := by simp [BitVec.lt_def] at hd ⊢; assumption
-    hrWidth := by simp [DivModState.init],
-    hqWidth := by simp [DivModState.init],
-    hdiv := by
-      simp only [DivModState.init, toNat_ofNat, zero_mod, Nat.mul_zero, Nat.add_zero];
-      rw [Nat.shiftRight_eq_div_pow]
-      apply Nat.div_eq_of_lt args.n.isLt
-  }
-
-/--
-A lawful DivModState with a fully consumed dividend (`wn = 0`) witnesses that the
-quotient has been correctly computed.
-/
-theorem DivModState.udiv_eq_of_lawful {n d : BitVec w} {qr : DivModState w}
-    (h_lawful : DivModState.Lawful {n, d} qr)
-    (h_final  : qr.wn = 0) :
-    n / d = qr.q := by
-  apply udiv_eq_of_mul_add_toNat h_lawful.hdPos h_lawful.hrLtDivisor
-  have hdiv := h_lawful.hdiv
-  simp only [h_final] at *
-  omega
-
-/--
-A lawful DivModState with a fully consumed dividend (`wn = 0`) witnesses that the
-remainder has been correctly computed.
-/
-theorem DivModState.umod_eq_of_lawful {qr : DivModState w}
-    (h : DivModState.Lawful {n, d} qr)
-    (h_final  : qr.wn = 0) :
-    n % d = qr.r := by
-  apply umod_eq_of_mul_add_toNat h.hrLtDivisor
-  have hdiv := h.hdiv
-  simp only [shiftRight_zero] at hdiv
-  simp only [h_final] at *
-  exact hdiv.symm
-
-/-! ### DivModState.Poised -/
-
-/--
-A `Poised` DivModState is a state which is `Lawful` and furthermore, has at least
-one numerator bit left to process `(0 < wn)`
-
-The input to the shift subtractor is a legal input to `divrem`, and we also need to have an
-input bit to perform shift subtraction on, and thus we need `0 < wn`.
-/
-structure DivModState.Poised {w : Nat} (args : DivModArgs w) (qr : DivModState w)
-  extends DivModState.Lawful args qr : Type where
-  /-- Only perform a round of shift-subtract if we have dividend bits. -/
-  hwn_lt : 0 < qr.wn
-
-/--
-In the shift subtract input, the dividend is at least one bit long (`wn > 0`), so
-the remainder has bits to be computed (`wr < w`).
-/
-def DivModState.wr_lt_w {qr : DivModState w} (h : qr.Poised args) : qr.wr < w := by
-  have hwrn := h.hwrn
-  have hwn_lt := h.hwn_lt
-  omega
-
-/-! ### Division shift subtractor -/
-
-/--
-One round of the division algorithm, that tries to perform a subtract shift.
-Note that this should only be called when `r.msb = false`, so we will not overflow.
-/
-def divSubtractShift (args : DivModArgs w) (qr : DivModState w) : DivModState w :=
-  let {n, d} := args
-  let wn := qr.wn - 1
-  let wr := qr.wr + 1
-  let r' := shiftConcat qr.r (n.getLsbD wn)
-  if r' < d then {
-    q := qr.q.shiftConcat false, -- If `r' < d`, then we do not have a quotient bit.
-    r := r'
-    wn, wr
-  } else {
-    q := qr.q.shiftConcat true, -- Otherwise, `r' ≥ d`, and we have a quotient bit.
-    r := r' - d -- we subtract to maintain the invariant that `r < d`.
-    wn, wr
-  }
-
-/-- The value of shifting right by `wn - 1` equals shifting by `wn` and grabbing the lsb at `(wn - 1)`. -/
-theorem DivModState.toNat_shiftRight_sub_one_eq
-    {args : DivModArgs w} {qr : DivModState w} (h : qr.Poised args) :
-    args.n.toNat >>> (qr.wn - 1)
-    = (args.n.toNat >>> qr.wn) * 2 + (args.n.getLsbD (qr.wn - 1)).toNat := by
-  show BitVec.toNat (args.n >>> (qr.wn - 1)) = _
-  have {..} := h -- break the structure down for `omega`
-  rw [shiftRight_sub_one_eq_shiftConcat args.n h.hwn_lt]
-  rw [toNat_shiftConcat_eq_of_lt (k := w - qr.wn)]
-  · simp
-  · omega
-  · apply BitVec.toNat_ushiftRight_lt
-    omega
-
-/--
-This is used when proving the correctness of the division algorithm,
-where we know that `r < d`.
-We then want to show that `((r.shiftConcat b) - d) < d` as the loop invariant.
-In arithmetic, this is the same as showing that
-`r * 2 + 1 - d < d`, which this theorem establishes.
-/
-private theorem two_mul_add_sub_lt_of_lt_of_lt_two (h : a < x) (hy : y < 2) :
-    2 * a + y - x < x := by omega
-
-/-- We show that the output of `divSubtractShift` is lawful, which tells us that it
-obeys the division equation. -/
-theorem lawful_divSubtractShift (qr : DivModState w) (h : qr.Poised args) :
-    DivModState.Lawful args (divSubtractShift args qr) := by
-  rcases args with ⟨n, d⟩
-  simp only [divSubtractShift, decide_eq_true_eq]
-  -- We add these hypotheses for `omega` to find them later.
-  have ⟨⟨hrwn, hd, hrd, hr, hn, hrnd⟩, hwn_lt⟩ := h
-  have : d.toNat * (qr.q.toNat * 2) = d.toNat * qr.q.toNat * 2 := by rw [Nat.mul_assoc]
-  by_cases rltd : shiftConcat qr.r (n.getLsbD (qr.wn - 1)) < d
-  · simp only [rltd, ↓reduceIte]
-    constructor <;> try bv_omega
-    case pos.hrWidth => apply toNat_shiftConcat_lt_of_lt <;> omega
-    case pos.hqWidth => apply toNat_shiftConcat_lt_of_lt <;> omega
-    case pos.hdiv =>
-      simp [qr.toNat_shiftRight_sub_one_eq h, h.hdiv, this,
-        toNat_shiftConcat_eq_of_lt (qr.wr_lt_w h) h.hrWidth,
-        toNat_shiftConcat_eq_of_lt (qr.wr_lt_w h) h.hqWidth]
-      omega
-  · simp only [rltd, ↓reduceIte]
-    constructor <;> try bv_omega
-    case neg.hrLtDivisor =>
-      simp only [lt_def, Nat.not_lt] at rltd
-      rw [BitVec.toNat_sub_of_le rltd,
-        toNat_shiftConcat_eq_of_lt (hk := qr.wr_lt_w h) (hx := h.hrWidth),
-        Nat.mul_comm]
-      apply two_mul_add_sub_lt_of_lt_of_lt_two <;> bv_omega
-    case neg.hrWidth =>
-      simp only
-      have hdr' : d ≤ (qr.r.shiftConcat (n.getLsbD (qr.wn - 1))) :=
-        BitVec.not_lt_iff_le.mp rltd
-      have hr' : ((qr.r.shiftConcat (n.getLsbD (qr.wn - 1)))).toNat < 2 ^ (qr.wr + 1) := by
-        apply toNat_shiftConcat_lt_of_lt <;> bv_omega
-      rw [BitVec.toNat_sub_of_le hdr']
-      omega
-    case neg.hqWidth =>
-      apply toNat_shiftConcat_lt_of_lt <;> omega
-    case neg.hdiv =>
-      have rltd' := (BitVec.not_lt_iff_le.mp rltd)
-      simp only [qr.toNat_shiftRight_sub_one_eq h,
-        BitVec.toNat_sub_of_le rltd',
-        toNat_shiftConcat_eq_of_lt (qr.wr_lt_w h) h.hrWidth]
-      simp only [BitVec.le_def,
-        toNat_shiftConcat_eq_of_lt (qr.wr_lt_w h) h.hrWidth] at rltd'
-      simp only [toNat_shiftConcat_eq_of_lt (qr.wr_lt_w h) h.hqWidth, h.hdiv, Nat.mul_add]
-      bv_omega
-
-/-! ### Core division algorithm circuit -/
-
-/-- A recursive definition of division for bitblasting, in terms of a shift-subtraction circuit. -/
-def divRec {w : Nat} (m : Nat) (args : DivModArgs w) (qr : DivModState w) :
-    DivModState w :=
-  match m with
-  | 0 => qr
-  | m + 1 => divRec m args <| divSubtractShift args qr
-
-@[simp]
-theorem divRec_zero (qr : DivModState w) :
-    divRec 0 args qr = qr := rfl
-
-@[simp]
-theorem divRec_succ (m : Nat) (args : DivModArgs w) (qr : DivModState w) :
-    divRec (m + 1) args qr =
-      divRec m args (divSubtractShift args qr) := rfl
-
-/-- The output of `divRec` is a lawful state -/
-theorem lawful_divRec {args : DivModArgs w} {qr : DivModState w}
-    (h : DivModState.Lawful args qr) :
-    DivModState.Lawful args (divRec qr.wn args qr) := by
-  generalize hm : qr.wn = m
-  induction m generalizing qr
-  case zero =>
-    exact h
-  case succ wn' ih =>
-    simp only [divRec_succ]
-    apply ih
-    · apply lawful_divSubtractShift
-      constructor
-      · assumption
-      · omega
-    · simp only [divSubtractShift, hm]
-      split <;> rfl
-
-/-- The output of `divRec` has no more bits left to process (i.e., `wn = 0`) -/
-@[simp]
-theorem wn_divRec (args : DivModArgs w) (qr : DivModState w) :
-    (divRec qr.wn args qr).wn = 0 := by
-  generalize hm : qr.wn = m
-  induction m generalizing qr
-  case zero =>
-    assumption
-  case succ wn' ih =>
-    apply ih
-    simp only [divSubtractShift, hm]
-    split <;> rfl
-
-/-- The result of `udiv` agrees with the result of the division recurrence. -/
-theorem udiv_eq_divRec (hd : 0#w < d) :
-    let out := divRec w {n, d} (DivModState.init w)
-    n / d = out.q := by
-  have := DivModState.lawful_init {n, d} hd
-  have := lawful_divRec this
-  apply DivModState.udiv_eq_of_lawful this (wn_divRec ..)
-
-/-- The result of `umod` agrees with the result of the division recurrence. -/
-theorem umod_eq_divRec (hd : 0#w < d) :
-    let out := divRec w {n, d} (DivModState.init w)
-    n % d = out.r := by
-  have := DivModState.lawful_init {n, d} hd
-  have := lawful_divRec this
-  apply DivModState.umod_eq_of_lawful this (wn_divRec ..)
-
-theorem divRec_succ' (m : Nat) (args : DivModArgs w) (qr : DivModState w) :
-    divRec (m+1) args qr =
-    let wn := qr.wn - 1
-    let wr := qr.wr + 1
-    let r' := shiftConcat qr.r (args.n.getLsbD wn)
-    let input : DivModState _ :=
-      if r' < args.d then {
-        q := qr.q.shiftConcat false,
-        r := r'
-        wn, wr
-      } else {
-        q := qr.q.shiftConcat true,
-        r := r' - args.d
-        wn, wr
-      }
-    divRec m args input := by
-  simp [divRec_succ, divSubtractShift]
-
 /- ### Arithmetic shift right (sshiftRight) recurrence -/

 /--
--- a/src/Init/Data/BitVec/Lemmas.lean
+++ b/src/Init/Data/BitVec/Lemmas.lean
--- a/src/Init/Data/Bool.lean
+++ b/src/Init/Data/Bool.lean
@@ -368,14 +368,13 @@ theorem and_or_inj_left_iff :
 /-- convert a `Bool` to a `Nat`, `false -> 0`, `true -> 1` -/
 def toNat (b : Bool) : Nat := cond b 1 0

-@[simp, bv_toNat] theorem toNat_false : false.toNat = 0 := rfl
+@[simp] theorem toNat_false : false.toNat = 0 := rfl

-@[simp, bv_toNat] theorem toNat_true : true.toNat = 1 := rfl
+@[simp] theorem toNat_true : true.toNat = 1 := rfl

 theorem toNat_le (c : Bool) : c.toNat ≤ 1 := by
  cases c <;> trivial

-@[bv_toNat]
 theorem toNat_lt (b : Bool) : b.toNat < 2 :=
  Nat.lt_succ_of_le (toNat_le _)

--- a/src/Init/Data/ByteArray/Basic.lean
+++ b/src/Init/Data/ByteArray/Basic.lean
@@ -245,7 +245,7 @@ On an invalid position, returns `(default : UInt8)`. -/
@[inline]
 def curr : Iterator → UInt8
  | ⟨arr, i⟩ =>
-    if h : i < arr.size then
+    if h:i < arr.size then
      arr[i]'h
    else
      default
--- a/src/Init/Data/Fin/Lemmas.lean
+++ b/src/Init/Data/Fin/Lemmas.lean
@@ -244,13 +244,9 @@ theorem add_def (a b : Fin n) : a + b = Fin.mk ((a + b) % n) (Nat.mod_lt _ a.siz

 theorem val_add (a b : Fin n) : (a + b).val = (a.val + b.val) % n := rfl

-@[simp] protected theorem zero_add [NeZero n] (k : Fin n) : (0 : Fin n) + k = k := by
+@[simp] protected theorem zero_add {n : Nat} [NeZero n] (i : Fin n) : (0 : Fin n) + i = i := by
  ext
-  simp [Fin.add_def, Nat.mod_eq_of_lt k.2]
-
-@[simp] protected theorem add_zero [NeZero n] (k : Fin n) : k + 0 = k := by
-  ext
-  simp [add_def, Nat.mod_eq_of_lt k.2]
+  simp [Fin.add_def, Nat.mod_eq_of_lt i.2]

 theorem val_add_one_of_lt {n : Nat} {i : Fin n.succ} (h : i < last _) : (i + 1).1 = i + 1 := by
  match n with
@@ -586,8 +582,8 @@ theorem rev_succ (k : Fin n) : rev (succ k) = castSucc (rev k) := k.rev_addNat 1
@[simp] theorem coe_pred (j : Fin (n + 1)) (h : j ≠ 0) : (j.pred h : Nat) = j - 1 := rfl

@[simp] theorem succ_pred : ∀ (i : Fin (n + 1)) (h : i ≠ 0), (i.pred h).succ = i
-  | ⟨0, _⟩, hi => by simp only [mk_zero, ne_eq, not_true] at hi
-  | ⟨_ + 1, _⟩, _ => rfl
+  | ⟨0, h⟩, hi => by simp only [mk_zero, ne_eq, not_true] at hi
+  | ⟨n + 1, h⟩, hi => rfl

@[simp]
 theorem pred_succ (i : Fin n) {h : i.succ ≠ 0} : i.succ.pred h = i := by
--- a/src/Init/Data/Float.lean
+++ b/src/Init/Data/Float.lean
@@ -72,35 +72,21 @@ instance floatDecLt (a b : Float) : Decidable (a < b) := Float.decLt a b
 instance floatDecLe (a b : Float) : Decidable (a ≤ b) := Float.decLe a b

@[extern "lean_float_to_string"] opaque Float.toString : Float → String
-/-- If the given float is non-negative, truncates the value to the nearest non-negative integer.
-If negative or NaN, returns `0`.
-If larger than the maximum value for `UInt8` (including Inf), returns the maximum value of `UInt8`
-(i.e. `UInt8.size - 1`).
-/
+
+/-- If the given float is positive, truncates the value to the nearest positive integer.
+If negative or larger than the maximum value for UInt8, returns 0. -/
@[extern "lean_float_to_uint8"] opaque Float.toUInt8 : Float → UInt8
-/-- If the given float is non-negative, truncates the value to the nearest non-negative integer.
-If negative or NaN, returns `0`.
-If larger than the maximum value for `UInt16` (including Inf), returns the maximum value of `UInt16`
-(i.e. `UInt16.size - 1`).
-/
+/-- If the given float is positive, truncates the value to the nearest positive integer.
+If negative or larger than the maximum value for UInt16, returns 0. -/
@[extern "lean_float_to_uint16"] opaque Float.toUInt16 : Float → UInt16
-/-- If the given float is non-negative, truncates the value to the nearest non-negative integer.
-If negative or NaN, returns `0`.
-If larger than the maximum value for `UInt32` (including Inf), returns the maximum value of `UInt32`
-(i.e. `UInt32.size - 1`).
-/
+/-- If the given float is positive, truncates the value to the nearest positive integer.
+If negative or larger than the maximum value for UInt32, returns 0. -/
@[extern "lean_float_to_uint32"] opaque Float.toUInt32 : Float → UInt32
-/-- If the given float is non-negative, truncates the value to the nearest non-negative integer.
-If negative or NaN, returns `0`.
-If larger than the maximum value for `UInt64` (including Inf), returns the maximum value of `UInt64`
-(i.e. `UInt64.size - 1`).
-/
+/-- If the given float is positive, truncates the value to the nearest positive integer.
+If negative or larger than the maximum value for UInt64, returns 0. -/
@[extern "lean_float_to_uint64"] opaque Float.toUInt64 : Float → UInt64
-/-- If the given float is non-negative, truncates the value to the nearest non-negative integer.
-If negative or NaN, returns `0`.
-If larger than the maximum value for `USize` (including Inf), returns the maximum value of `USize`
-(i.e. `USize.size - 1`). This value is platform dependent).
-/
+/-- If the given float is positive, truncates the value to the nearest positive integer.
+If negative or larger than the maximum value for USize, returns 0. -/
@[extern "lean_float_to_usize"] opaque Float.toUSize : Float → USize

@[extern "lean_float_isnan"] opaque Float.isNaN : Float → Bool
--- a/src/Init/Data/Function.lean
+++ b/src/Init/Data/Function.lean
@@ -1,35 +0,0 @@
-/-
-Copyright (c) 2024 Lean FRO. All rights reserved.
-Released under Apache 2.0 license as described in the file LICENSE.
-Authors: Kim Morrison
-/
-
-prelude
-import Init.Core
-
-namespace Function
-
-@[inline]
-def curry : (α × β → φ) → α → β → φ := fun f a b => f (a, b)
-
-/-- Interpret a function with two arguments as a function on `α × β` -/
-@[inline]
-def uncurry : (α → β → φ) → α × β → φ := fun f a => f a.1 a.2
-
-@[simp]
-theorem curry_uncurry (f : α → β → φ) : curry (uncurry f) = f :=
-  rfl
-
-@[simp]
-theorem uncurry_curry (f : α × β → φ) : uncurry (curry f) = f :=
-  funext fun ⟨_a, _b⟩ => rfl
-
-@[simp]
-theorem uncurry_apply_pair {α β γ} (f : α → β → γ) (x : α) (y : β) : uncurry f (x, y) = f x y :=
-  rfl
-
-@[simp]
-theorem curry_apply {α β γ} (f : α × β → γ) (x : α) (y : β) : curry f x y = f (x, y) :=
-  rfl
-
-end Function
--- a/src/Init/Data/Int/DivModLemmas.lean
+++ b/src/Init/Data/Int/DivModLemmas.lean
@@ -253,7 +253,7 @@ theorem tmod_def (a b : Int) : tmod a b = a - b * a.tdiv b := by

 theorem fmod_add_fdiv : ∀ a b : Int, a.fmod b + b * a.fdiv b = a
  | 0, ofNat _ | 0, -[_+1] => congrArg ofNat <| by simp
-  | succ _, ofNat _ => congrArg ofNat <| Nat.mod_add_div ..
+  | succ m, ofNat n => congrArg ofNat <| Nat.mod_add_div ..
  | succ m, -[n+1] => by
    show subNatNat (m % succ n) n + (↑(succ n * (m / succ n)) + n + 1) = (m + 1)
    rw [Int.add_comm _ n, ← Int.add_assoc, ← Int.add_assoc,
@@ -289,8 +289,8 @@ theorem fmod_eq_tmod {a b : Int} (Ha : 0 ≤ a) (Hb : 0 ≤ b) : fmod a b = tmod

@[simp] protected theorem ediv_neg : ∀ a b : Int, a / (-b) = -(a / b)
  | ofNat m, 0 => show ofNat (m / 0) = -↑(m / 0) by rw [Nat.div_zero]; rfl
-  | ofNat _, -[_+1] => (Int.neg_neg _).symm
-  | ofNat _, succ _ | -[_+1], 0 | -[_+1], succ _ | -[_+1], -[_+1] => rfl
+  | ofNat m, -[n+1] => (Int.neg_neg _).symm
+  | ofNat m, succ n | -[m+1], 0 | -[m+1], succ n | -[m+1], -[n+1] => rfl

 theorem ediv_neg' {a b : Int} (Ha : a < 0) (Hb : 0 < b) : a / b < 0 :=
  match a, b, eq_negSucc_of_lt_zero Ha, eq_succ_of_zero_lt Hb with
@@ -339,7 +339,7 @@ theorem add_mul_ediv_right (a b : Int) {c : Int} (H : c ≠ 0) : (a + b * c) / c
      | _, ⟨k, rfl⟩, -[n+1] => show (a - n.succ * k.succ).ediv k.succ = a.ediv k.succ - n.succ by
        rw [← Int.add_sub_cancel (ediv ..), ← this, Int.sub_add_cancel]
  fun {k n} => @fun
-  | ofNat _ => congrArg ofNat <| Nat.add_mul_div_right _ _ k.succ_pos
+  | ofNat m => congrArg ofNat <| Nat.add_mul_div_right _ _ k.succ_pos
  | -[m+1] => by
    show ((n * k.succ : Nat) - m.succ : Int).ediv k.succ = n - (m / k.succ + 1 : Nat)
    by_cases h : m < n * k.succ
@@ -396,7 +396,7 @@ theorem add_mul_ediv_left (a : Int) {b : Int}
      rw [Int.mul_neg, Int.ediv_neg, Int.ediv_neg]; apply congrArg Neg.neg; apply this
  fun m k b =>
  match b, k with
-  | ofNat _, _ => congrArg ofNat (Nat.mul_div_mul_left _ _ m.succ_pos)
+  | ofNat n, k => congrArg ofNat (Nat.mul_div_mul_left _ _ m.succ_pos)
  | -[n+1], 0 => by
    rw [Int.ofNat_zero, Int.mul_zero, Int.ediv_zero, Int.ediv_zero]
  | -[n+1], succ k => congrArg negSucc <|
@@ -822,14 +822,14 @@ theorem ediv_eq_ediv_of_mul_eq_mul {a b c d : Int}
 unseal Nat.div in
@[simp] protected theorem tdiv_neg : ∀ a b : Int, a.tdiv (-b) = -(a.tdiv b)
  | ofNat m, 0 => show ofNat (m / 0) = -↑(m / 0) by rw [Nat.div_zero]; rfl
-  | ofNat _, -[_+1] | -[_+1], succ _ => (Int.neg_neg _).symm
-  | ofNat _, succ _ | -[_+1], 0 | -[_+1], -[_+1] => rfl
+  | ofNat m, -[n+1] | -[m+1], succ n => (Int.neg_neg _).symm
+  | ofNat m, succ n | -[m+1], 0 | -[m+1], -[n+1] => rfl

 unseal Nat.div in
@[simp] protected theorem neg_tdiv : ∀ a b : Int, (-a).tdiv b = -(a.tdiv b)
  | 0, n => by simp [Int.neg_zero]
-  | succ _, (n:Nat) | -[_+1], 0 | -[_+1], -[_+1] => rfl
-  | succ _, -[_+1] | -[_+1], succ _ => (Int.neg_neg _).symm
+  | succ m, (n:Nat) | -[m+1], 0 | -[m+1], -[n+1] => rfl
+  | succ m, -[n+1] | -[m+1], succ n => (Int.neg_neg _).symm

 protected theorem neg_tdiv_neg (a b : Int) : (-a).tdiv (-b) = a.tdiv b := by
  simp [Int.tdiv_neg, Int.neg_tdiv, Int.neg_neg]
--- a/src/Init/Data/Int/Lemmas.lean
+++ b/src/Init/Data/Int/Lemmas.lean
@@ -181,12 +181,12 @@ theorem subNatNat_add_negSucc (m n k : Nat) :
      Nat.add_comm]

 protected theorem add_assoc : ∀ a b c : Int, a + b + c = a + (b + c)
-  | (m:Nat), (n:Nat), _ => aux1 ..
+  | (m:Nat), (n:Nat), c => aux1 ..
  | Nat.cast m, b, Nat.cast k => by
    rw [Int.add_comm, ← aux1, Int.add_comm k, aux1, Int.add_comm b]
  | a, (n:Nat), (k:Nat) => by
    rw [Int.add_comm, Int.add_comm a, ← aux1, Int.add_comm a, Int.add_comm k]
-  | -[_+1], -[_+1], (k:Nat) => aux2 ..
+  | -[m+1], -[n+1], (k:Nat) => aux2 ..
  | -[m+1], (n:Nat), -[k+1] => by
    rw [Int.add_comm, ← aux2, Int.add_comm n, ← aux2, Int.add_comm -[m+1]]
  | (m:Nat), -[n+1], -[k+1] => by
--- a/src/Init/Data/Int/Order.lean
+++ b/src/Init/Data/Int/Order.lean
@@ -512,8 +512,8 @@ theorem toNat_add_nat {a : Int} (ha : 0 ≤ a) (n : Nat) : (a + n).toNat = a.toN

@[simp] theorem pred_toNat : ∀ i : Int, (i - 1).toNat = i.toNat - 1
  | 0 => rfl
-  | (_+1:Nat) => by simp [ofNat_add]
-  | -[_+1] => rfl
+  | (n+1:Nat) => by simp [ofNat_add]
+  | -[n+1] => rfl

 theorem toNat_sub_toNat_neg : ∀ n : Int, ↑n.toNat - ↑(-n).toNat = n
  | 0 => rfl
--- a/src/Init/Data/Int/Pow.lean
+++ b/src/Init/Data/Int/Pow.lean
@@ -5,7 +5,6 @@ Authors: Jeremy Avigad, Deniz Aydin, Floris van Doorn, Mario Carneiro
 -/
 prelude
 import Init.Data.Int.Lemmas
-import Init.Data.Nat.Lemmas

 namespace Int

@@ -36,24 +35,10 @@ theorem pow_le_pow_of_le_right {n : Nat} (hx : n > 0) {i : Nat} : ∀ {j}, i ≤
 theorem pos_pow_of_pos {n : Nat} (m : Nat) (h : 0 < n) : 0 < n^m :=
  pow_le_pow_of_le_right h (Nat.zero_le _)

-@[norm_cast]
 theorem natCast_pow (b n : Nat) : ((b^n : Nat) : Int) = (b : Int) ^ n := by
  match n with
  | 0 => rfl
  | n + 1 =>
    simp only [Nat.pow_succ, Int.pow_succ, natCast_mul, natCast_pow _ n]

-@[simp]
-protected theorem two_pow_pred_sub_two_pow {w : Nat} (h : 0 < w) :
-    ((2 ^ (w - 1) : Nat) - (2 ^ w : Nat) : Int) = - ((2 ^ (w - 1) : Nat) : Int) := by
-  rw [← Nat.two_pow_pred_add_two_pow_pred h]
-  omega
-
-@[simp]
-protected theorem two_pow_pred_sub_two_pow' {w : Nat} (h : 0 < w) :
-    (2 : Int) ^ (w - 1) - (2 : Int) ^ w = - (2 : Int) ^ (w - 1) := by
-  norm_cast
-  rw [← Nat.two_pow_pred_add_two_pow_pred h]
-  simp [h]
-
 end Int
--- a/src/Init/Data/List.lean
+++ b/src/Init/Data/List.lean
@@ -23,5 +23,3 @@ import Init.Data.List.TakeDrop
 import Init.Data.List.Zip
 import Init.Data.List.Perm
 import Init.Data.List.Sort
-import Init.Data.List.ToArray
-import Init.Data.List.MapIdx
--- a/src/Init/Data/List/Attach.lean
+++ b/src/Init/Data/List/Attach.lean
@@ -73,7 +73,7 @@ theorem map_pmap {p : α → Prop} (g : β → γ) (f : ∀ a, p a → β) (l H)
  · simp only [*, pmap, map]

 theorem pmap_map {p : β → Prop} (g : ∀ b, p b → γ) (f : α → β) (l H) :
-    pmap g (map f l) H = pmap (fun a h => g (f a) h) l fun _ h => H _ (mem_map_of_mem _ h) := by
+    pmap g (map f l) H = pmap (fun a h => g (f a) h) l fun a h => H _ (mem_map_of_mem _ h) := by
  induction l
  · rfl
  · simp only [*, pmap, map]
@@ -84,7 +84,7 @@ theorem attach_congr {l₁ l₂ : List α} (h : l₁ = l₂) :
  simp

 theorem attachWith_congr {l₁ l₂ : List α} (w : l₁ = l₂) {P : α → Prop} {H : ∀ x ∈ l₁, P x} :
-    l₁.attachWith P H = l₂.attachWith P fun _ h => H _ (w ▸ h) := by
+    l₁.attachWith P H = l₂.attachWith P fun x h => H _ (w ▸ h) := by
  subst w
  simp

@@ -353,7 +353,7 @@ theorem attach_map {l : List α} (f : α → β) :
  induction l <;> simp [*]

 theorem attachWith_map {l : List α} (f : α → β) {P : β → Prop} {H : ∀ (b : β), b ∈ l.map f → P b} :
-    (l.map f).attachWith P H = (l.attachWith (P ∘ f) (fun _ h => H _ (mem_map_of_mem f h))).map
+    (l.map f).attachWith P H = (l.attachWith (P ∘ f) (fun a h => H _ (mem_map_of_mem f h))).map
      fun ⟨x, h⟩ => ⟨f x, h⟩ := by
  induction l <;> simp [*]

@@ -548,133 +548,4 @@ theorem count_attachWith [DecidableEq α] {p : α → Prop} (l : List α) (H :
    (l.attachWith p H).count a = l.count ↑a :=
  Eq.trans (countP_congr fun _ _ => by simp [Subtype.ext_iff]) <| countP_attachWith _ _ _

-/-! ## unattach
-
-`List.unattach` is the (one-sided) inverse of `List.attach`. It is a synonym for `List.map Subtype.val`.
-
-We use it by providing a simp lemma `l.attach.unattach = l`, and simp lemmas which recognize higher order
-functions applied to `l : List { x // p x }` which only depend on the value, not the predicate, and rewrite these
-in terms of a simpler function applied to `l.unattach`.
-
-Further, we provide simp lemmas that push `unattach` inwards.
-/
-
-/--
-A synonym for `l.map (·.val)`. Mostly this should not be needed by users.
-It is introduced as an intermediate step by lemmas such as `map_subtype`,
-and is ideally subsequently simplified away by `unattach_attach`.
-
-If not, usually the right approach is `simp [List.unattach, -List.map_subtype]` to unfold.
-/
-def unattach {α : Type _} {p : α → Prop} (l : List { x // p x }) := l.map (·.val)
-
-@[simp] theorem unattach_nil {p : α → Prop} : ([] : List { x // p x }).unattach = [] := rfl
-@[simp] theorem unattach_cons {p : α → Prop} {a : { x // p x }} {l : List { x // p x }} :
-  (a :: l).unattach = a.val :: l.unattach := rfl
-
-@[simp] theorem length_unattach {p : α → Prop} {l : List { x // p x }} :
-    l.unattach.length = l.length := by
-  unfold unattach
-  simp
-
-@[simp] theorem unattach_attach {l : List α} : l.attach.unattach = l := by
-  unfold unattach
-  induction l with
-  | nil => simp
-  | cons a l ih => simp [ih, Function.comp_def]
-
-@[simp] theorem unattach_attachWith {p : α → Prop} {l : List α}
-    {H : ∀ a ∈ l, p a} :
-    (l.attachWith p H).unattach = l := by
-  unfold unattach
-  induction l with
-  | nil => simp
-  | cons a l ih => simp [ih, Function.comp_def]
-
-/-! ### Recognizing higher order functions on subtypes using a function that only depends on the value. -/
-
-/--
-This lemma identifies folds over lists of subtypes, where the function only depends on the value, not the proposition,
-and simplifies these to the function directly taking the value.
-/
-@[simp] theorem foldl_subtype {p : α → Prop} {l : List { x // p x }}
-    {f : β → { x // p x } → β} {g : β → α → β} {x : β}
-    {hf : ∀ b x h, f b ⟨x, h⟩ = g b x} :
-    l.foldl f x = l.unattach.foldl g x := by
-  unfold unattach
-  induction l generalizing x with
-  | nil => simp
-  | cons a l ih => simp [ih, hf]
-
-/--
-This lemma identifies folds over lists of subtypes, where the function only depends on the value, not the proposition,
-and simplifies these to the function directly taking the value.
-/
-@[simp] theorem foldr_subtype {p : α → Prop} {l : List { x // p x }}
-    {f : { x // p x } → β → β} {g : α → β → β} {x : β}
-    {hf : ∀ x h b, f ⟨x, h⟩ b = g x b} :
-    l.foldr f x = l.unattach.foldr g x := by
-  unfold unattach
-  induction l generalizing x with
-  | nil => simp
-  | cons a l ih => simp [ih, hf]
-
-/--
-This lemma identifies maps over lists of subtypes, where the function only depends on the value, not the proposition,
-and simplifies these to the function directly taking the value.
-/
-@[simp] theorem map_subtype {p : α → Prop} {l : List { x // p x }}
-    {f : { x // p x } → β} {g : α → β} {hf : ∀ x h, f ⟨x, h⟩ = g x} :
-    l.map f = l.unattach.map g := by
-  unfold unattach
-  induction l with
-  | nil => simp
-  | cons a l ih => simp [ih, hf]
-
-@[simp] theorem filterMap_subtype {p : α → Prop} {l : List { x // p x }}
-    {f : { x // p x } → Option β} {g : α → Option β} {hf : ∀ x h, f ⟨x, h⟩ = g x} :
-    l.filterMap f = l.unattach.filterMap g := by
-  unfold unattach
-  induction l with
-  | nil => simp
-  | cons a l ih => simp [ih, hf, filterMap_cons]
-
-@[simp] theorem bind_subtype {p : α → Prop} {l : List { x // p x }}
-    {f : { x // p x } → List β} {g : α → List β} {hf : ∀ x h, f ⟨x, h⟩ = g x} :
-    (l.bind f) = l.unattach.bind g := by
-  unfold unattach
-  induction l with
-  | nil => simp
-  | cons a l ih => simp [ih, hf]
-
-@[simp] theorem unattach_filter {p : α → Prop} {l : List { x // p x }}
-    {f : { x // p x } → Bool} {g : α → Bool} {hf : ∀ x h, f ⟨x, h⟩ = g x} :
-    (l.filter f).unattach = l.unattach.filter g := by
-  induction l with
-  | nil => simp
-  | cons a l ih =>
-    simp only [filter_cons, hf, unattach_cons]
-    split <;> simp [ih]
-
-/-! ### Simp lemmas pushing `unattach` inwards. -/
-
-@[simp] theorem unattach_reverse {p : α → Prop} {l : List { x // p x }} :
-    l.reverse.unattach = l.unattach.reverse := by
-  simp [unattach, -map_subtype]
-
-@[simp] theorem unattach_append {p : α → Prop} {l₁ l₂ : List { x // p x }} :
-    (l₁ ++ l₂).unattach = l₁.unattach ++ l₂.unattach := by
-  simp [unattach, -map_subtype]
-
-@[simp] theorem unattach_flatten {p : α → Prop} {l : List (List { x // p x })} :
-    l.flatten.unattach = (l.map unattach).flatten := by
-  unfold unattach
-  induction l <;> simp_all
-
-@[deprecated unattach_flatten (since := "2024-10-14")] abbrev unattach_join := @unattach_flatten
-
-@[simp] theorem unattach_replicate {p : α → Prop} {n : Nat} {x : { x // p x }} :
-    (List.replicate n x).unattach = List.replicate n x.1 := by
-  simp [unattach, -map_subtype]
-
 end List
--- a/src/Init/Data/List/Basic.lean
+++ b/src/Init/Data/List/Basic.lean
@@ -29,10 +29,9 @@ The operations are organized as follow:
 * Lexicographic ordering: `lt`, `le`, and instances.
 * Head and tail operators: `head`, `head?`, `headD?`, `tail`, `tail?`, `tailD`.
 * Basic operations:
-  `map`, `filter`, `filterMap`, `foldr`, `append`, `flatten`, `pure`, `bind`, `replicate`, and
+  `map`, `filter`, `filterMap`, `foldr`, `append`, `join`, `pure`, `bind`, `replicate`, and
  `reverse`.
 * Additional functions defined in terms of these: `leftpad`, `rightPad`, and `reduceOption`.
-* Operations using indexes: `mapIdx`.
 * List membership: `isEmpty`, `elem`, `contains`, `mem` (and the `∈` notation),
  and decidability for predicates quantifying over membership in a `List`.
 * Sublists: `take`, `drop`, `takeWhile`, `dropWhile`, `partition`, `dropLast`,
@@ -44,7 +43,7 @@ The operations are organized as follow:
 * Logic: `any`, `all`, `or`, and `and`.
 * Zippers: `zipWith`, `zip`, `zipWithAll`, and `unzip`.
 * Ranges and enumeration: `range`, `iota`, `enumFrom`, and `enum`.
-* Minima and maxima: `min?` and `max?`.
+* Minima and maxima: `minimum?` and `maximum?`.
 * Other functions: `intersperse`, `intercalate`, `eraseDups`, `eraseReps`, `span`, `groupBy`,
  `removeAll`
  (currently these functions are mostly only used in meta code,
@@ -219,8 +218,8 @@ def get? : (as : List α) → (i : Nat) → Option α

 theorem ext_get? : ∀ {l₁ l₂ : List α}, (∀ n, l₁.get? n = l₂.get? n) → l₁ = l₂
  | [], [], _ => rfl
-  | _ :: _, [], h => nomatch h 0
-  | [], _ :: _, h => nomatch h 0
+  | a :: l₁, [], h => nomatch h 0
+  | [], a' :: l₂, h => nomatch h 0
  | a :: l₁, a' :: l₂, h => by
    have h0 : some a = some a' := h 0
    injection h0 with aa; simp only [aa, ext_get? fun n => h (n+1)]
@@ -369,7 +368,7 @@ def tailD (list fallback : List α) : List α :=
 /-! ## Basic `List` operations.

 We define the basic functional programming operations on `List`:
-`map`, `filter`, `filterMap`, `foldr`, `append`, `flatten`, `pure`, `bind`, `replicate`, and `reverse`.
+`map`, `filter`, `filterMap`, `foldr`, `append`, `join`, `pure`, `bind`, `replicate`, and `reverse`.
 -/

 /-! ### map -/
@@ -543,20 +542,18 @@ theorem reverseAux_eq_append (as bs : List α) : reverseAux as bs = reverseAux a
  simp [reverse, reverseAux]
  rw [← reverseAux_eq_append]

-/-! ### flatten -/
+/-! ### join -/

 /--
-`O(|flatten L|)`. `join L` concatenates all the lists in `L` into one list.
-* `flatten [[a], [], [b, c], [d, e, f]] = [a, b, c, d, e, f]`
+`O(|join L|)`. `join L` concatenates all the lists in `L` into one list.
+* `join [[a], [], [b, c], [d, e, f]] = [a, b, c, d, e, f]`
 -/
-def flatten : List (List α) → List α
+def join : List (List α) → List α
  | []      => []
-  | a :: as => a ++ flatten as
+  | a :: as => a ++ join as

-@[simp] theorem flatten_nil : List.flatten ([] : List (List α)) = [] := rfl
-@[simp] theorem flatten_cons : (l :: ls).flatten = l ++ ls.flatten := rfl
-
-@[deprecated flatten (since := "2024-10-14"), inherit_doc flatten] abbrev join := @flatten
+@[simp] theorem join_nil : List.join ([] : List (List α)) = [] := rfl
+@[simp] theorem join_cons : (l :: ls).join = l ++ ls.join := rfl

 /-! ### pure -/

@@ -570,11 +567,11 @@ def flatten : List (List α) → List α
 to get a list of lists, and then concatenates them all together.
 * `[2, 3, 2].bind range = [0, 1, 0, 1, 2, 0, 1]`
 -/
-@[inline] protected def bind {α : Type u} {β : Type v} (a : List α) (b : α → List β) : List β := flatten (map b a)
+@[inline] protected def bind {α : Type u} {β : Type v} (a : List α) (b : α → List β) : List β := join (map b a)

-@[simp] theorem bind_nil (f : α → List β) : List.bind [] f = [] := by simp [flatten, List.bind]
+@[simp] theorem bind_nil (f : α → List β) : List.bind [] f = [] := by simp [join, List.bind]
@[simp] theorem bind_cons x xs (f : α → List β) :
-  List.bind (x :: xs) f = f x ++ List.bind xs f := by simp [flatten, List.bind]
+  List.bind (x :: xs) f = f x ++ List.bind xs f := by simp [join, List.bind]

 set_option linter.missingDocs false in
@[deprecated bind_nil (since := "2024-06-15")] abbrev nil_bind := @bind_nil
@@ -1398,17 +1395,8 @@ def unzip : List (α × β) → List α × List β

 /-! ## Ranges and enumeration -/

-/-- Sum of a list.
-
-`List.sum [a, b, c] = a + (b + (c + 0))` -/
-def sum {α} [Add α] [Zero α] : List α → α :=
-  foldr (· + ·) 0
-
-@[simp] theorem sum_nil [Add α] [Zero α] : ([] : List α).sum = 0 := rfl
-@[simp] theorem sum_cons [Add α] [Zero α] {a : α} {l : List α} : (a::l).sum = a + l.sum := rfl
-
 /-- Sum of a list of natural numbers. -/
-- We intend to subsequently deprecate this in favor of `List.sum`.
+-- This is not in the `List` namespace as later `List.sum` will be defined polymorphically.
 protected def _root_.Nat.sum (l : List Nat) : Nat := l.foldr (·+·) 0

@[simp] theorem _root_.Nat.sum_nil : Nat.sum ([] : List Nat) = 0 := rfl
@@ -1476,34 +1464,30 @@ def enum : List α → List (Nat × α) := enumFrom 0

 /-! ## Minima and maxima -/

-/-! ### min? -/
+/-! ### minimum? -/

 /--
 Returns the smallest element of the list, if it is not empty.
-* `[].min? = none`
-* `[4].min? = some 4`
-* `[1, 4, 2, 10, 6].min? = some 1`
+* `[].minimum? = none`
+* `[4].minimum? = some 4`
+* `[1, 4, 2, 10, 6].minimum? = some 1`
 -/
-def min? [Min α] : List α → Option α
+def minimum? [Min α] : List α → Option α
  | []    => none
  | a::as => some <| as.foldl min a

-@[inherit_doc min?, deprecated min? (since := "2024-09-29")] abbrev minimum? := @min?
-
-/-! ### max? -/
+/-! ### maximum? -/

 /--
 Returns the largest element of the list, if it is not empty.
-* `[].max? = none`
-* `[4].max? = some 4`
-* `[1, 4, 2, 10, 6].max? = some 10`
+* `[].maximum? = none`
+* `[4].maximum? = some 4`
+* `[1, 4, 2, 10, 6].maximum? = some 10`
 -/
-def max? [Max α] : List α → Option α
+def maximum? [Max α] : List α → Option α
  | []    => none
  | a::as => some <| as.foldl max a

-@[inherit_doc max?, deprecated max? (since := "2024-09-29")] abbrev maximum? := @max?
-
 /-! ## Other list operations

 The functions are currently mostly used in meta code,
@@ -1539,7 +1523,7 @@ def intersperse (sep : α) : List α → List α
 * `intercalate sep [a, b, c] = a ++ sep ++ b ++ sep ++ c`
 -/
 def intercalate (sep : List α) (xs : List (List α)) : List α :=
-  (intersperse sep xs).flatten
+  join (intersperse sep xs)

 /-! ### eraseDups -/

--- a/src/Init/Data/List/BasicAux.lean
+++ b/src/Init/Data/List/BasicAux.lean
@@ -235,8 +235,8 @@ theorem sizeOf_get [SizeOf α] (as : List α) (i : Fin as.length) : sizeOf (as.g
 theorem le_antisymm [LT α] [s : Antisymm (¬ · < · : α → α → Prop)] {as bs : List α} (h₁ : as ≤ bs) (h₂ : bs ≤ as) : as = bs :=
  match as, bs with
  | [],    []    => rfl
-  | [],    _::_ => False.elim <| h₂ (List.lt.nil ..)
-  | _::_, []    => False.elim <| h₁ (List.lt.nil ..)
+  | [],    b::bs => False.elim <| h₂ (List.lt.nil ..)
+  | a::as, []    => False.elim <| h₁ (List.lt.nil ..)
  | a::as, b::bs => by
    by_cases hab : a < b
    · exact False.elim <| h₂ (List.lt.head _ _ hab)
--- a/src/Init/Data/List/Count.lean
+++ b/src/Init/Data/List/Count.lean
@@ -153,15 +153,13 @@ theorem countP_filterMap (p : β → Bool) (f : α → Option β) (l : List α)
  simp only [length_filterMap_eq_countP]
  congr
  ext a
-  simp (config := { contextual := true }) [Option.getD_eq_iff, Option.isSome_eq_isSome]
+  simp (config := { contextual := true }) [Option.getD_eq_iff]

-@[simp] theorem countP_flatten (l : List (List α)) :
-    countP p l.flatten = (l.map (countP p)).sum := by
-  simp only [countP_eq_length_filter, filter_flatten]
+@[simp] theorem countP_join (l : List (List α)) :
+    countP p l.join = Nat.sum (l.map (countP p)) := by
+  simp only [countP_eq_length_filter, filter_join]
  simp [countP_eq_length_filter']

-@[deprecated countP_flatten (since := "2024-10-14")] abbrev countP_join := @countP_flatten
-
@[simp] theorem countP_reverse (l : List α) : countP p l.reverse = countP p l := by
  simp [countP_eq_length_filter, filter_reverse]

@@ -232,10 +230,8 @@ theorem count_singleton (a b : α) : count a [b] = if b == a then 1 else 0 := by
@[simp] theorem count_append (a : α) : ∀ l₁ l₂, count a (l₁ ++ l₂) = count a l₁ + count a l₂ :=
  countP_append _

-theorem count_flatten (a : α) (l : List (List α)) : count a l.flatten = (l.map (count a)).sum := by
-  simp only [count_eq_countP, countP_flatten, count_eq_countP']
-
-@[deprecated count_flatten (since := "2024-10-14")] abbrev count_join := @count_flatten
+theorem count_join (a : α) (l : List (List α)) : count a l.join = Nat.sum (l.map (count a)) := by
+  simp only [count_eq_countP, countP_join, count_eq_countP']

@[simp] theorem count_reverse (a : α) (l : List α) : count a l.reverse = count a l := by
  simp only [count_eq_countP, countP_eq_length_filter, filter_reverse, length_reverse]
--- a/src/Init/Data/List/Erase.lean
+++ b/src/Init/Data/List/Erase.lean
@@ -52,9 +52,9 @@ theorem eraseP_of_forall_not {l : List α} (h : ∀ a, a ∈ l → ¬p a) : l.er
 theorem eraseP_ne_nil {xs : List α} {p : α → Bool} : xs.eraseP p ≠ [] ↔ xs ≠ [] ∧ ∀ x, p x → xs ≠ [x] := by
  simp

-theorem exists_of_eraseP : ∀ {l : List α} {a} (_ : a ∈ l) (_ : p a),
+theorem exists_of_eraseP : ∀ {l : List α} {a} (al : a ∈ l) (pa : p a),
    ∃ a l₁ l₂, (∀ b ∈ l₁, ¬p b) ∧ p a ∧ l = l₁ ++ a :: l₂ ∧ l.eraseP p = l₁ ++ l₂
-  | b :: l, _, al, pa =>
+  | b :: l, a, al, pa =>
    if pb : p b then
      ⟨b, [], l, forall_mem_nil _, pb, by simp [pb]⟩
    else
@@ -168,8 +168,8 @@ theorem eraseP_append_left {a : α} (pa : p a) :

 theorem eraseP_append_right :
    ∀ {l₁ : List α} l₂, (∀ b ∈ l₁, ¬p b) → eraseP p (l₁++l₂) = l₁ ++ l₂.eraseP p
-  | [],     _, _ => rfl
-  | _ :: _, _, h => by
+  | [],      l₂, _ => rfl
+  | x :: xs, l₂, h => by
    simp [(forall_mem_cons.1 h).1, eraseP_append_right _ (forall_mem_cons.1 h).2]

 theorem eraseP_append (l₁ l₂ : List α) :
--- a/src/Init/Data/List/Find.lean
+++ b/src/Init/Data/List/Find.lean
@@ -132,14 +132,14 @@ theorem findSome?_append {l₁ l₂ : List α} : (l₁ ++ l₂).findSome? f = (l
    simp only [cons_append, findSome?]
    split <;> simp_all

-theorem head_flatten {L : List (List α)} (h : ∃ l, l ∈ L ∧ l ≠ []) :
-    (flatten L).head (by simpa using h) = (L.findSome? fun l => l.head?).get (by simpa using h) := by
-  simp [head_eq_iff_head?_eq_some, head?_flatten]
+theorem head_join {L : List (List α)} (h : ∃ l, l ∈ L ∧ l ≠ []) :
+    (join L).head (by simpa using h) = (L.findSome? fun l => l.head?).get (by simpa using h) := by
+  simp [head_eq_iff_head?_eq_some, head?_join]

-theorem getLast_flatten {L : List (List α)} (h : ∃ l, l ∈ L ∧ l ≠ []) :
-    (flatten L).getLast (by simpa using h) =
+theorem getLast_join {L : List (List α)} (h : ∃ l, l ∈ L ∧ l ≠ []) :
+    (join L).getLast (by simpa using h) =
      (L.reverse.findSome? fun l => l.getLast?).get (by simpa using h) := by
-  simp [getLast_eq_iff_getLast_eq_some, getLast?_flatten]
+  simp [getLast_eq_iff_getLast_eq_some, getLast?_join]

 theorem findSome?_replicate : findSome? f (replicate n a) = if n = 0 then none else f a := by
  cases n with
@@ -326,35 +326,35 @@ theorem get_find?_mem (xs : List α) (p : α → Bool) (h) : (xs.find? p).get h
    simp only [cons_append, find?]
    by_cases h : p x <;> simp [h, ih]

-@[simp] theorem find?_flatten (xs : List (List α)) (p : α → Bool) :
-    xs.flatten.find? p = xs.findSome? (·.find? p) := by
+@[simp] theorem find?_join (xs : List (List α)) (p : α → Bool) :
+    xs.join.find? p = xs.findSome? (·.find? p) := by
  induction xs with
  | nil => simp
  | cons x xs ih =>
-    simp only [flatten_cons, find?_append, findSome?_cons, ih]
+    simp only [join_cons, find?_append, findSome?_cons, ih]
    split <;> simp [*]

-theorem find?_flatten_eq_none {xs : List (List α)} {p : α → Bool} :
-    xs.flatten.find? p = none ↔ ∀ ys ∈ xs, ∀ x ∈ ys, !p x := by
+theorem find?_join_eq_none {xs : List (List α)} {p : α → Bool} :
+    xs.join.find? p = none ↔ ∀ ys ∈ xs, ∀ x ∈ ys, !p x := by
  simp

 /--
-If `find? p` returns `some a` from `xs.flatten`, then `p a` holds, and
+If `find? p` returns `some a` from `xs.join`, then `p a` holds, and
 some list in `xs` contains `a`, and no earlier element of that list satisfies `p`.
 Moreover, no earlier list in `xs` has an element satisfying `p`.
 -/
-theorem find?_flatten_eq_some {xs : List (List α)} {p : α → Bool} {a : α} :
-    xs.flatten.find? p = some a ↔
+theorem find?_join_eq_some {xs : List (List α)} {p : α → Bool} {a : α} :
+    xs.join.find? p = some a ↔
      p a ∧ ∃ as ys zs bs, xs = as ++ (ys ++ a :: zs) :: bs ∧
        (∀ a ∈ as, ∀ x ∈ a, !p x) ∧ (∀ x ∈ ys, !p x) := by
  rw [find?_eq_some]
  constructor
  · rintro ⟨h, ⟨ys, zs, h₁, h₂⟩⟩
    refine ⟨h, ?_⟩
-    rw [flatten_eq_append_iff] at h₁
+    rw [join_eq_append_iff] at h₁
    obtain (⟨as, bs, rfl, rfl, h₁⟩ | ⟨as, bs, c, cs, ds, rfl, rfl, h₁⟩) := h₁
    · replace h₁ := h₁.symm
-      rw [flatten_eq_cons_iff] at h₁
+      rw [join_eq_cons_iff] at h₁
      obtain ⟨bs, cs, ds, rfl, h₁, rfl⟩ := h₁
      refine ⟨as ++ bs, [], cs, ds, by simp, ?_⟩
      simp
@@ -371,7 +371,7 @@ theorem find?_flatten_eq_some {xs : List (List α)} {p : α → Bool} {a : α} :
      · intro x m
        simpa using h₂ x (by simpa using .inr m)
  · rintro ⟨h, ⟨as, ys, zs, bs, rfl, h₁, h₂⟩⟩
-    refine ⟨h, as.flatten ++ ys, zs ++ bs.flatten, by simp, ?_⟩
+    refine ⟨h, as.join ++ ys, zs ++ bs.join, by simp, ?_⟩
    intro a m
    simp at m
    obtain ⟨l, ml, m⟩ | m := m
@@ -786,15 +786,15 @@ theorem findIdx?_of_eq_none {xs : List α} {p : α → Bool} (w : xs.findIdx? p
  induction xs with simp
  | cons _ _ _ => split <;> simp_all [Option.map_or', Option.map_map]; rfl

-theorem findIdx?_flatten {l : List (List α)} {p : α → Bool} :
-    l.flatten.findIdx? p =
+theorem findIdx?_join {l : List (List α)} {p : α → Bool} :
+    l.join.findIdx? p =
      (l.findIdx? (·.any p)).map
-        fun i => ((l.take i).map List.length).sum +
+        fun i => Nat.sum ((l.take i).map List.length) +
          (l[i]?.map fun xs => xs.findIdx p).getD 0 := by
  induction l with
  | nil => simp
  | cons xs l ih =>
-    simp only [flatten, findIdx?_append, map_take, map_cons, findIdx?, any_eq_true, Nat.zero_add,
+    simp only [join, findIdx?_append, map_take, map_cons, findIdx?, any_eq_true, Nat.zero_add,
      findIdx?_succ]
    split
    · simp only [Option.map_some', take_zero, sum_nil, length_cons, zero_lt_succ,
@@ -976,13 +976,4 @@ theorem IsInfix.lookup_eq_none {l₁ l₂ : List (α × β)} (h : l₁ <:+: l₂

 end lookup

-/-! ### Deprecations -/
-
-@[deprecated head_flatten (since := "2024-10-14")] abbrev head_join := @head_flatten
-@[deprecated getLast_flatten (since := "2024-10-14")] abbrev getLast_join := @getLast_flatten
-@[deprecated find?_flatten (since := "2024-10-14")] abbrev find?_join := @find?_flatten
-@[deprecated find?_flatten_eq_none (since := "2024-10-14")] abbrev find?_join_eq_none := @find?_flatten_eq_none
-@[deprecated find?_flatten_eq_some (since := "2024-10-14")] abbrev find?_join_eq_some := @find?_flatten_eq_some
-@[deprecated findIdx?_flatten (since := "2024-10-14")] abbrev findIdx?_join := @findIdx?_flatten
-
 end List
--- a/src/Init/Data/List/Impl.lean
+++ b/src/Init/Data/List/Impl.lean
@@ -31,7 +31,7 @@ The following operations are still missing `@[csimp]` replacements:
 The following operations are not recursive to begin with
 (or are defined in terms of recursive primitives):
 `isEmpty`, `isSuffixOf`, `isSuffixOf?`, `rotateLeft`, `rotateRight`, `insert`, `zip`, `enum`,
-`min?`, `max?`, and `removeAll`.
+`minimum?`, `maximum?`, and `removeAll`.

 The following operations were already given `@[csimp]` replacements in `Init/Data/List/Basic.lean`:
 `length`, `map`, `filter`, `replicate`, `leftPad`, `unzip`, `range'`, `iota`, `intersperse`.
@@ -109,12 +109,12 @@ The following operations are given `@[csimp]` replacements below:
    | x::xs, acc => by simp [bindTR.go, bind, go xs]
  exact (go as #[]).symm

-/-! ### flatten -/
+/-! ### join -/

-/-- Tail recursive version of `List.flatten`. -/
-@[inline] def flattenTR (l : List (List α)) : List α := bindTR l id
+/-- Tail recursive version of `List.join`. -/
+@[inline] def joinTR (l : List (List α)) : List α := bindTR l id

-@[csimp] theorem flatten_eq_flattenTR : @flatten = @flattenTR := by
+@[csimp] theorem join_eq_joinTR : @join = @joinTR := by
  funext α l; rw [← List.bind_id, List.bind_eq_bindTR]; rfl

 /-! ## Sublists -/
@@ -322,7 +322,7 @@ where
  | [_] => simp
  | x::y::xs =>
    let rec go {acc x} : ∀ xs,
-      intercalateTR.go sep.toArray x xs acc = acc.toList ++ flatten (intersperse sep (x::xs))
+      intercalateTR.go sep.toArray x xs acc = acc.toList ++ join (intersperse sep (x::xs))
    | [] => by simp [intercalateTR.go]
    | _::_ => by simp [intercalateTR.go, go]
    simp [intersperse, go]
--- a/src/Init/Data/List/Lemmas.lean
+++ b/src/Init/Data/List/Lemmas.lean
@@ -55,7 +55,7 @@ See also
 * `Init.Data.List.Erase` for lemmas about `List.eraseP` and `List.erase`.
 * `Init.Data.List.Find` for lemmas about `List.find?`, `List.findSome?`, `List.findIdx`,
  `List.findIdx?`, and `List.indexOf`
-* `Init.Data.List.MinMax` for lemmas about `List.min?` and `List.max?`.
+* `Init.Data.List.MinMax` for lemmas about `List.minimum?` and `List.maximum?`.
 * `Init.Data.List.Pairwise` for lemmas about `List.Pairwise` and `List.Nodup`.
 * `Init.Data.List.Sublist` for lemmas about `List.Subset`, `List.Sublist`, `List.IsPrefix`,
  `List.IsSuffix`, and `List.IsInfix`.
@@ -191,7 +191,7 @@ theorem get?_eq_some : l.get? n = some a ↔ ∃ h, get l ⟨n, h⟩ = a :=
  ⟨fun e =>
    have : n < length l := Nat.gt_of_not_le fun hn => by cases get?_len_le hn ▸ e
    ⟨this, by rwa [get?_eq_get this, Option.some.injEq] at e⟩,
-  fun ⟨_, e⟩ => e ▸ get?_eq_get _⟩
+  fun ⟨h, e⟩ => e ▸ get?_eq_get _⟩

 theorem get?_eq_none : l.get? n = none ↔ length l ≤ n :=
  ⟨fun e => Nat.ge_of_not_lt (fun h' => by cases e ▸ get?_eq_some.2 ⟨h', rfl⟩), get?_len_le⟩
@@ -203,9 +203,6 @@ theorem get?_eq_none : l.get? n = none ↔ length l ≤ n :=

@[simp] theorem get_eq_getElem (l : List α) (i : Fin l.length) : l.get i = l[i.1]'i.2 := rfl

-theorem getElem?_eq_some {l : List α} : l[i]? = some a ↔ ∃ h : i < l.length, l[i]'h = a := by
-  simpa using get?_eq_some
-
 /--
 If one has `l.get i` in an expression (with `i : Fin l.length`) and `h : l = l'`,
 `rw [h]` will give a "motive it not type correct" error, as it cannot rewrite the
@@ -492,7 +489,7 @@ theorem getElem?_of_mem {a} {l : List α} (h : a ∈ l) : ∃ n : Nat, l[n]? = s
 theorem get?_of_mem {a} {l : List α} (h : a ∈ l) : ∃ n, l.get? n = some a :=
  let ⟨⟨n, _⟩, e⟩ := get_of_mem h; ⟨n, e ▸ get?_eq_get _⟩

-@[simp] theorem getElem_mem : ∀ {l : List α} {n} (h : n < l.length), l[n]'h ∈ l
+theorem getElem_mem : ∀ {l : List α} {n} (h : n < l.length), l[n]'h ∈ l
  | _ :: _, 0, _ => .head ..
  | _ :: l, _+1, _ => .tail _ (getElem_mem (l := l) ..)

@@ -718,9 +715,9 @@ theorem set_eq_of_length_le {l : List α} {n : Nat} (h : l.length ≤ n) {a : α
 theorem set_comm (a b : α) : ∀ {n m : Nat} (l : List α), n ≠ m →
    (l.set n a).set m b = (l.set m b).set n a
  | _, _, [], _ => by simp
-  | _+1, 0, _ :: _, _ => by simp [set]
-  | 0, _+1, _ :: _, _ => by simp [set]
-  | _+1, _+1, _ :: t, h =>
+  | n+1, 0, _ :: _, _ => by simp [set]
+  | 0, m+1, _ :: _, _ => by simp [set]
+  | n+1, m+1, x :: t, h =>
    congrArg _ <| set_comm a b t fun h' => h <| Nat.succ_inj'.mpr h'

@[simp]
@@ -881,20 +878,6 @@ theorem foldr_map' {α β : Type u} (g : α → β) (f : α → α → α) (f' :
  · simp
  · simp [*, h]

-theorem foldl_assoc {op : α → α → α} [ha : Std.Associative op] :
-    ∀ {l : List α} {a₁ a₂}, l.foldl op (op a₁ a₂) = op a₁ (l.foldl op a₂)
-  | [], a₁, a₂ => rfl
-  | a :: l, a₁, a₂ => by
-    simp only [foldl_cons, ha.assoc]
-    rw [foldl_assoc]
-
-theorem foldr_assoc {op : α → α → α} [ha : Std.Associative op] :
-    ∀ {l : List α} {a₁ a₂}, l.foldr op (op a₁ a₂) = op (l.foldr op a₁) a₂
-  | [], a₁, a₂ => rfl
-  | a :: l, a₁, a₂ => by
-    simp only [foldr_cons, ha.assoc]
-    rw [foldr_assoc]
-
 theorem foldl_hom (f : α₁ → α₂) (g₁ : α₁ → β → α₁) (g₂ : α₂ → β → α₂) (l : List β) (init : α₁)
    (H : ∀ x y, g₂ (f x) y = f (g₁ x y)) : l.foldl g₂ (f init) = f (l.foldl g₁ init) := by
  induction l generalizing init <;> simp [*, H]
@@ -994,8 +977,8 @@ theorem getLast_eq_getElem : ∀ (l : List α) (h : l ≠ []),
      match l with
      | [] => contradiction
      | a :: l => exact Nat.le_refl _)
-  | [_], _ => rfl
-  | _ :: _ :: _, _ => by
+  | [a], h => rfl
+  | a :: b :: l, h => by
    simp [getLast, get, Nat.succ_sub_succ, getLast_eq_getElem]

@[deprecated getLast_eq_getElem (since := "2024-07-15")]
@@ -1021,14 +1004,14 @@ theorem getLast_eq_getLastD (a l h) : @getLast α (a::l) h = getLastD l a := by
 theorem getLast!_cons [Inhabited α] : @getLast! α _ (a::l) = getLastD l a := by
  simp [getLast!, getLast_eq_getLastD]

-@[simp] theorem getLast_mem : ∀ {l : List α} (h : l ≠ []), getLast l h ∈ l
+theorem getLast_mem : ∀ {l : List α} (h : l ≠ []), getLast l h ∈ l
  | [], h => absurd rfl h
  | [_], _ => .head ..
  | _::a::l, _ => .tail _ <| getLast_mem (cons_ne_nil a l)

 theorem getLast_mem_getLast? : ∀ {l : List α} (h : l ≠ []), getLast l h ∈ getLast? l
  | [], h => by contradiction
-  | _ :: _, _ => rfl
+  | a :: l, _ => rfl

 theorem getLastD_mem_cons : ∀ (l : List α) (a : α), getLastD l a ∈ a::l
  | [], _ => .head ..
@@ -1119,7 +1102,7 @@ theorem head?_eq_some_iff {xs : List α} {a : α} : xs.head? = some a ↔ ∃ ys
@[simp] theorem head?_isSome : l.head?.isSome ↔ l ≠ [] := by
  cases l <;> simp

-@[simp] theorem head_mem : ∀ {l : List α} (h : l ≠ []), head l h ∈ l
+theorem head_mem : ∀ {l : List α} (h : l ≠ []), head l h ∈ l
  | [], h => absurd rfl h
  | _::_, _ => .head ..

@@ -1134,7 +1117,7 @@ theorem mem_of_mem_head? : ∀ {l : List α} {a : α}, a ∈ l.head? → a ∈ l

 theorem head_mem_head? : ∀ {l : List α} (h : l ≠ []), head l h ∈ head? l
  | [], h => by contradiction
-  | _ :: _, _ => rfl
+  | a :: l, _ => rfl

 theorem head?_concat {a : α} : (l ++ [a]).head? = l.head?.getD a := by
  cases l <;> simp
@@ -1343,12 +1326,12 @@ theorem set_map {f : α → β} {l : List α} {n : Nat} {a : α} :
  simp

@[simp] theorem head_map (f : α → β) (l : List α) (w) :
-    (map f l).head w = f (l.head (by simpa using w)) := by
+    head (map f l) w = f (head l (by simpa using w)) := by
  cases l
  · simp at w
  · simp_all

-@[simp] theorem head?_map (f : α → β) (l : List α) : (map f l).head? = l.head?.map f := by
+@[simp] theorem head?_map (f : α → β) (l : List α) : head? (map f l) = (head? l).map f := by
  cases l <;> rfl

@[simp] theorem map_tail? (f : α → β) (l : List α) : (tail? l).map (map f) = tail? (map f l) := by
@@ -1466,7 +1449,7 @@ theorem map_filter_eq_foldr (f : α → β) (p : α → Bool) (as : List α) :

@[simp] theorem filter_append {p : α → Bool} :
    ∀ (l₁ l₂ : List α), filter p (l₁ ++ l₂) = filter p l₁ ++ filter p l₂
-  | [], _ => rfl
+  | [], l₂ => rfl
  | a :: l₁, l₂ => by simp [filter]; split <;> simp [filter_append l₁]

 theorem filter_eq_cons_iff {l} {a} {as} :
@@ -1671,11 +1654,6 @@ theorem filterMap_eq_cons_iff {l} {b} {bs} :

 /-! ### append -/

-@[simp] theorem nil_append_fun : (([] : List α) ++ ·) = id := rfl
-
-@[simp] theorem cons_append_fun (a : α) (as : List α) :
-    (fun bs => ((a :: as) ++ bs)) = fun bs => a :: (as ++ bs) := rfl
-
 theorem getElem_append {l₁ l₂ : List α} (n : Nat) (h) :
    (l₁ ++ l₂)[n] = if h' : n < l₁.length then l₁[n] else l₂[n - l₁.length]'(by simp at h h'; exact Nat.sub_lt_left_of_lt_add h' h) := by
  split <;> rename_i h'
@@ -1690,7 +1668,7 @@ theorem getElem?_append_left {l₁ l₂ : List α} {n : Nat} (hn : n < l₁.leng

 theorem getElem?_append_right : ∀ {l₁ l₂ : List α} {n : Nat}, l₁.length ≤ n →
  (l₁ ++ l₂)[n]? = l₂[n - l₁.length]?
-| [], _, _, _ => rfl
+| [], _, n, _ => rfl
 | a :: l, _, n+1, h₁ => by
  rw [cons_append]
  simp [Nat.succ_sub_succ_eq_sub, getElem?_append_right (Nat.lt_succ.1 h₁)]
@@ -1755,8 +1733,8 @@ theorem append_of_mem {a : α} {l : List α} : a ∈ l → ∃ s t : List α, l

 theorem append_inj :
    ∀ {s₁ s₂ t₁ t₂ : List α}, s₁ ++ t₁ = s₂ ++ t₂ → length s₁ = length s₂ → s₁ = s₂ ∧ t₁ = t₂
-  | [], [], _, _, h, _ => ⟨rfl, h⟩
-  | _ :: _, _ :: _, _, _, h, hl => by
+  | [], [], t₁, t₂, h, _ => ⟨rfl, h⟩
+  | a :: s₁, b :: s₂, t₁, t₂, h, hl => by
    simp [append_inj (cons.inj h).2 (Nat.succ.inj hl)] at h ⊢; exact h

 theorem append_inj_right (h : s₁ ++ t₁ = s₂ ++ t₂) (hl : length s₁ = length s₂) : t₁ = t₂ :=
@@ -2068,97 +2046,106 @@ theorem eq_nil_or_concat : ∀ l : List α, l = [] ∨ ∃ L b, l = concat L b
    | _, .inl rfl => .inr ⟨[], a, rfl⟩
    | _, .inr ⟨L, b, rfl⟩ => .inr ⟨a::L, b, rfl⟩

-/-! ### flatten -/
+/-! ### join -/

-@[simp] theorem length_flatten (L : List (List α)) : (flatten L).length = (L.map length).sum := by
+@[simp] theorem length_join (L : List (List α)) : (join L).length = Nat.sum (L.map length) := by
  induction L with
  | nil => rfl
  | cons =>
-    simp [flatten, length_append, *]
+    simp [join, length_append, *]

-theorem flatten_singleton (l : List α) : [l].flatten = l := by simp
+theorem join_singleton (l : List α) : [l].join = l := by simp

-@[simp] theorem mem_flatten : ∀ {L : List (List α)}, a ∈ L.flatten ↔ ∃ l, l ∈ L ∧ a ∈ l
+@[simp] theorem mem_join : ∀ {L : List (List α)}, a ∈ L.join ↔ ∃ l, l ∈ L ∧ a ∈ l
  | [] => by simp
-  | b :: l => by simp [mem_flatten, or_and_right, exists_or]
+  | b :: l => by simp [mem_join, or_and_right, exists_or]

-@[simp] theorem flatten_eq_nil_iff {L : List (List α)} : L.flatten = [] ↔ ∀ l ∈ L, l = [] := by
+@[simp] theorem join_eq_nil_iff {L : List (List α)} : L.join = [] ↔ ∀ l ∈ L, l = [] := by
  induction L <;> simp_all

-theorem flatten_ne_nil_iff {xs : List (List α)} : xs.flatten ≠ [] ↔ ∃ x, x ∈ xs ∧ x ≠ [] := by
+@[deprecated join_eq_nil_iff (since := "2024-09-05")] abbrev join_eq_nil := @join_eq_nil_iff
+
+theorem join_ne_nil_iff {xs : List (List α)} : xs.join ≠ [] ↔ ∃ x, x ∈ xs ∧ x ≠ [] := by
  simp

-theorem exists_of_mem_flatten : a ∈ flatten L → ∃ l, l ∈ L ∧ a ∈ l := mem_flatten.1
+@[deprecated join_ne_nil_iff (since := "2024-09-05")] abbrev join_ne_nil := @join_ne_nil_iff

-theorem mem_flatten_of_mem (lL : l ∈ L) (al : a ∈ l) : a ∈ flatten L := mem_flatten.2 ⟨l, lL, al⟩
+theorem exists_of_mem_join : a ∈ join L → ∃ l, l ∈ L ∧ a ∈ l := mem_join.1

-theorem forall_mem_flatten {p : α → Prop} {L : List (List α)} :
-    (∀ (x) (_ : x ∈ flatten L), p x) ↔ ∀ (l) (_ : l ∈ L) (x) (_ : x ∈ l), p x := by
-  simp only [mem_flatten, forall_exists_index, and_imp]
+theorem mem_join_of_mem (lL : l ∈ L) (al : a ∈ l) : a ∈ join L := mem_join.2 ⟨l, lL, al⟩
+
+theorem forall_mem_join {p : α → Prop} {L : List (List α)} :
+    (∀ (x) (_ : x ∈ join L), p x) ↔ ∀ (l) (_ : l ∈ L) (x) (_ : x ∈ l), p x := by
+  simp only [mem_join, forall_exists_index, and_imp]
  constructor <;> (intros; solve_by_elim)

-theorem flatten_eq_bind {L : List (List α)} : flatten L = L.bind id := by
+theorem join_eq_bind {L : List (List α)} : join L = L.bind id := by
  induction L <;> simp [List.bind]

-theorem head?_flatten {L : List (List α)} : (flatten L).head? = L.findSome? fun l => l.head? := by
+theorem head?_join {L : List (List α)} : (join L).head? = L.findSome? fun l => l.head? := by
  induction L with
  | nil => rfl
  | cons =>
    simp only [findSome?_cons]
    split <;> simp_all

-- `getLast?_flatten` is proved later, after the `reverse` section.
-- `head_flatten` and `getLast_flatten` are proved in `Init.Data.List.Find`.
+-- `getLast?_join` is proved later, after the `reverse` section.
+-- `head_join` and `getLast_join` are proved in `Init.Data.List.Find`.

-theorem foldl_flatten (f : β → α → β) (b : β) (L : List (List α)) :
-    (flatten L).foldl f b = L.foldl (fun b l => l.foldl f b) b := by
+theorem foldl_join (f : β → α → β) (b : β) (L : List (List α)) :
+    (join L).foldl f b = L.foldl (fun b l => l.foldl f b) b := by
  induction L generalizing b <;> simp_all

-theorem foldr_flatten (f : α → β → β) (b : β) (L : List (List α)) :
-    (flatten L).foldr f b = L.foldr (fun l b => l.foldr f b) b := by
+theorem foldr_join (f : α → β → β) (b : β) (L : List (List α)) :
+    (join L).foldr f b = L.foldr (fun l b => l.foldr f b) b := by
  induction L <;> simp_all

-@[simp] theorem map_flatten (f : α → β) (L : List (List α)) : map f (flatten L) = flatten (map (map f) L) := by
+@[simp] theorem map_join (f : α → β) (L : List (List α)) : map f (join L) = join (map (map f) L) := by
  induction L <;> simp_all

-@[simp] theorem filterMap_flatten (f : α → Option β) (L : List (List α)) :
-    filterMap f (flatten L) = flatten (map (filterMap f) L) := by
+@[simp] theorem filterMap_join (f : α → Option β) (L : List (List α)) :
+    filterMap f (join L) = join (map (filterMap f) L) := by
  induction L <;> simp [*, filterMap_append]

-@[simp] theorem filter_flatten (p : α → Bool) (L : List (List α)) :
-    filter p (flatten L) = flatten (map (filter p) L) := by
+@[simp] theorem filter_join (p : α → Bool) (L : List (List α)) :
+    filter p (join L) = join (map (filter p) L) := by
  induction L <;> simp [*, filter_append]

-theorem flatten_filter_not_isEmpty  :
-    ∀ {L : List (List α)}, flatten (L.filter fun l => !l.isEmpty) = L.flatten
+theorem join_filter_not_isEmpty  :
+    ∀ {L : List (List α)}, join (L.filter fun l => !l.isEmpty) = L.join
  | [] => rfl
  | [] :: L
  | (a :: l) :: L => by
-      simp [flatten_filter_not_isEmpty (L := L)]
+      simp [join_filter_not_isEmpty (L := L)]

-theorem flatten_filter_ne_nil [DecidablePred fun l : List α => l ≠ []] {L : List (List α)} :
-    flatten (L.filter fun l => l ≠ []) = L.flatten := by
+theorem join_filter_ne_nil [DecidablePred fun l : List α => l ≠ []] {L : List (List α)} :
+    join (L.filter fun l => l ≠ []) = L.join := by
  simp only [ne_eq, ← isEmpty_iff, Bool.not_eq_true, Bool.decide_eq_false,
-    flatten_filter_not_isEmpty]
+    join_filter_not_isEmpty]

-@[simp] theorem flatten_append (L₁ L₂ : List (List α)) : flatten (L₁ ++ L₂) = flatten L₁ ++ flatten L₂ := by
+@[deprecated filter_join (since := "2024-08-26")]
+theorem join_map_filter (p : α → Bool) (l : List (List α)) :
+    (l.map (filter p)).join = (l.join).filter p := by
+  rw [filter_join]
+
+@[simp] theorem join_append (L₁ L₂ : List (List α)) : join (L₁ ++ L₂) = join L₁ ++ join L₂ := by
  induction L₁ <;> simp_all

-theorem flatten_concat (L : List (List α)) (l : List α) : flatten (L ++ [l]) = flatten L ++ l := by
+theorem join_concat (L : List (List α)) (l : List α) : join (L ++ [l]) = join L ++ l := by
  simp

-theorem flatten_flatten {L : List (List (List α))} : flatten (flatten L) = flatten (map flatten L) := by
+theorem join_join {L : List (List (List α))} : join (join L) = join (map join L) := by
  induction L <;> simp_all

-theorem flatten_eq_cons_iff {xs : List (List α)} {y : α} {ys : List α} :
-    xs.flatten = y :: ys ↔
-      ∃ as bs cs, xs = as ++ (y :: bs) :: cs ∧ (∀ l, l ∈ as → l = []) ∧ ys = bs ++ cs.flatten := by
+theorem join_eq_cons_iff {xs : List (List α)} {y : α} {ys : List α} :
+    xs.join = y :: ys ↔
+      ∃ as bs cs, xs = as ++ (y :: bs) :: cs ∧ (∀ l, l ∈ as → l = []) ∧ ys = bs ++ cs.join := by
  constructor
  · induction xs with
    | nil => simp
    | cons x xs ih =>
      intro h
-      simp only [flatten_cons] at h
+      simp only [join_cons] at h
      replace h := h.symm
      rw [cons_eq_append_iff] at h
      obtain (⟨rfl, h⟩ | ⟨z⟩) := h
@@ -2169,23 +2156,23 @@ theorem flatten_eq_cons_iff {xs : List (List α)} {y : α} {ys : List α} :
        refine ⟨[], a', xs, ?_⟩
        simp
  · rintro ⟨as, bs, cs, rfl, h₁, rfl⟩
-    simp [flatten_eq_nil_iff.mpr h₁]
+    simp [join_eq_nil_iff.mpr h₁]

-theorem flatten_eq_append_iff {xs : List (List α)} {ys zs : List α} :
-    xs.flatten = ys ++ zs ↔
-      (∃ as bs, xs = as ++ bs ∧ ys = as.flatten ∧ zs = bs.flatten) ∨
-        ∃ as bs c cs ds, xs = as ++ (bs ++ c :: cs) :: ds ∧ ys = as.flatten ++ bs ∧
-          zs = c :: cs ++ ds.flatten := by
+theorem join_eq_append_iff {xs : List (List α)} {ys zs : List α} :
+    xs.join = ys ++ zs ↔
+      (∃ as bs, xs = as ++ bs ∧ ys = as.join ∧ zs = bs.join) ∨
+        ∃ as bs c cs ds, xs = as ++ (bs ++ c :: cs) :: ds ∧ ys = as.join ++ bs ∧
+          zs = c :: cs ++ ds.join := by
  constructor
  · induction xs generalizing ys with
    | nil =>
-      simp only [flatten_nil, nil_eq, append_eq_nil, and_false, cons_append, false_and, exists_const,
+      simp only [join_nil, nil_eq, append_eq_nil, and_false, cons_append, false_and, exists_const,
        exists_false, or_false, and_imp, List.cons_ne_nil]
      rintro rfl rfl
      exact ⟨[], [], by simp⟩
    | cons x xs ih =>
      intro h
-      simp only [flatten_cons] at h
+      simp only [join_cons] at h
      rw [append_eq_append_iff] at h
      obtain (⟨ys, rfl, h⟩ | ⟨c', rfl, h⟩) := h
      · obtain (⟨as, bs, rfl, rfl, rfl⟩ | ⟨as, bs, c, cs, ds, rfl, rfl, rfl⟩) := ih h
@@ -2199,15 +2186,18 @@ theorem flatten_eq_append_iff {xs : List (List α)} {ys zs : List α} :
    · simp
    · simp

-/-- Two lists of sublists are equal iff their flattens coincide, as well as the lengths of the
+@[deprecated join_eq_cons_iff (since := "2024-09-05")] abbrev join_eq_cons := @join_eq_cons_iff
+@[deprecated join_eq_append_iff (since := "2024-09-05")] abbrev join_eq_append := @join_eq_append_iff
+
+/-- Two lists of sublists are equal iff their joins coincide, as well as the lengths of the
 sublists. -/
-theorem eq_iff_flatten_eq : ∀ {L L' : List (List α)},
-    L = L' ↔ L.flatten = L'.flatten ∧ map length L = map length L'
+theorem eq_iff_join_eq : ∀ {L L' : List (List α)},
+    L = L' ↔ L.join = L'.join ∧ map length L = map length L'
  | _, [] => by simp_all
  | [], x' :: L' => by simp_all
  | x :: L, x' :: L' => by
    simp
-    rw [eq_iff_flatten_eq]
+    rw [eq_iff_join_eq]
    constructor
    · rintro ⟨rfl, h₁, h₂⟩
      simp_all
@@ -2217,12 +2207,12 @@ theorem eq_iff_flatten_eq : ∀ {L L' : List (List α)},

 /-! ### bind -/

-theorem bind_def (l : List α) (f : α → List β) : l.bind f = flatten (map f l) := by rfl
+theorem bind_def (l : List α) (f : α → List β) : l.bind f = join (map f l) := by rfl

-@[simp] theorem bind_id (l : List (List α)) : List.bind l id = l.flatten := by simp [bind_def]
+@[simp] theorem bind_id (l : List (List α)) : List.bind l id = l.join := by simp [bind_def]

@[simp] theorem mem_bind {f : α → List β} {b} {l : List α} : b ∈ l.bind f ↔ ∃ a, a ∈ l ∧ b ∈ f a := by
-  simp [bind_def, mem_flatten]
+  simp [bind_def, mem_join]
  exact ⟨fun ⟨_, ⟨a, h₁, rfl⟩, h₂⟩ => ⟨a, h₁, h₂⟩, fun ⟨a, h₁, h₂⟩ => ⟨_, ⟨a, h₁, rfl⟩, h₂⟩⟩

 theorem exists_of_mem_bind {b : β} {l : List α} {f : α → List β} :
@@ -2233,7 +2223,7 @@ theorem mem_bind_of_mem {b : β} {l : List α} {f : α → List β} {a} (al : a

@[simp]
 theorem bind_eq_nil_iff {l : List α} {f : α → List β} : List.bind l f = [] ↔ ∀ x ∈ l, f x = [] :=
-  flatten_eq_nil_iff.trans <| by
+  join_eq_nil_iff.trans <| by
    simp only [mem_map, forall_exists_index, and_imp, forall_apply_eq_imp_iff₂]

@[deprecated bind_eq_nil_iff (since := "2024-09-05")] abbrev bind_eq_nil := @bind_eq_nil_iff
@@ -2397,21 +2387,11 @@ theorem map_eq_replicate_iff {l : List α} {f : α → β} {b : β} :
@[simp] theorem map_const (l : List α) (b : β) : map (Function.const α b) l = replicate l.length b :=
  map_eq_replicate_iff.mpr fun _ _ => rfl

-@[simp] theorem map_const_fun (x : β) : map (Function.const α x) = (replicate ·.length x) := by
-  funext l
-  simp
-
 /-- Variant of `map_const` using a lambda rather than `Function.const`. -/
 -- This can not be a `@[simp]` lemma because it would fire on every `List.map`.
 theorem map_const' (l : List α) (b : β) : map (fun _ => b) l = replicate l.length b :=
  map_const l b

-@[simp] theorem set_replicate_self : (replicate n a).set i a = replicate n a := by
-  apply ext_getElem
-  · simp
-  · intro i h₁ h₂
-    simp [getElem_set]
-
@[simp] theorem append_replicate_replicate : replicate n a ++ replicate m a = replicate (n + m) a := by
  rw [eq_replicate_iff]
  constructor
@@ -2471,23 +2451,23 @@ theorem filterMap_replicate_of_some {f : α → Option β} (h : f a = some b) :
    (replicate n a).filterMap f = [] := by
  simp [filterMap_replicate, h]

-@[simp] theorem flatten_replicate_nil : (replicate n ([] : List α)).flatten = [] := by
+@[simp] theorem join_replicate_nil : (replicate n ([] : List α)).join = [] := by
  induction n <;> simp_all [replicate_succ]

-@[simp] theorem flatten_replicate_singleton : (replicate n [a]).flatten = replicate n a := by
+@[simp] theorem join_replicate_singleton : (replicate n [a]).join = replicate n a := by
  induction n <;> simp_all [replicate_succ]

-@[simp] theorem flatten_replicate_replicate : (replicate n (replicate m a)).flatten = replicate (n * m) a := by
+@[simp] theorem join_replicate_replicate : (replicate n (replicate m a)).join = replicate (n * m) a := by
  induction n with
  | zero => simp
  | succ n ih =>
-    simp only [replicate_succ, flatten_cons, ih, append_replicate_replicate, replicate_inj, or_true,
+    simp only [replicate_succ, join_cons, ih, append_replicate_replicate, replicate_inj, or_true,
      and_true, add_one_mul, Nat.add_comm]

-theorem bind_replicate {β} (f : α → List β) : (replicate n a).bind f = (replicate n (f a)).flatten := by
+theorem bind_replicate {β} (f : α → List β) : (replicate n a).bind f = (replicate n (f a)).join := by
  induction n with
  | zero => simp
-  | succ n ih => simp only [replicate_succ, bind_cons, ih, flatten_cons]
+  | succ n ih => simp only [replicate_succ, bind_cons, ih, join_cons]

@[simp] theorem isEmpty_replicate : (replicate n a).isEmpty = decide (n = 0) := by
  cases n <;> simp [replicate_succ]
@@ -2662,14 +2642,14 @@ theorem reverse_eq_concat {xs ys : List α} {a : α} :
    xs.reverse = ys ++ [a] ↔ xs = a :: ys.reverse := by
  rw [reverse_eq_iff, reverse_concat]

-/-- Reversing a flatten is the same as reversing the order of parts and reversing all parts. -/
-theorem reverse_flatten (L : List (List α)) :
-    L.flatten.reverse = (L.map reverse).reverse.flatten := by
+/-- Reversing a join is the same as reversing the order of parts and reversing all parts. -/
+theorem reverse_join (L : List (List α)) :
+    L.join.reverse = (L.map reverse).reverse.join := by
  induction L <;> simp_all

-/-- Flattening a reverse is the same as reversing all parts and reversing the flattened result. -/
-theorem flatten_reverse (L : List (List α)) :
-    L.reverse.flatten = (L.map reverse).flatten.reverse := by
+/-- Joining a reverse is the same as reversing all parts and reversing the joined result. -/
+theorem join_reverse (L : List (List α)) :
+    L.reverse.join = (L.map reverse).join.reverse := by
  induction L <;> simp_all

 theorem reverse_bind {β} (l : List α) (f : α → List β) : (l.bind f).reverse = l.reverse.bind (reverse ∘ f) := by
@@ -2695,7 +2675,7 @@ theorem bind_reverse {β} (l : List α) (f : α → List β) : (l.reverse.bind f
@[simp] theorem reverse_replicate (n) (a : α) : reverse (replicate n a) = replicate n a :=
  eq_replicate_iff.2
    ⟨by rw [length_reverse, length_replicate],
-     fun _ h => eq_of_mem_replicate (mem_reverse.1 h)⟩
+     fun b h => eq_of_mem_replicate (mem_reverse.1 h)⟩

 /-! #### Further results about `getLast` and `getLast?` -/

@@ -2789,8 +2769,8 @@ theorem getLast?_bind {L : List α} {f : α → List β} :
  rw [head?_bind]
  rfl

-theorem getLast?_flatten {L : List (List α)} :
-    (flatten L).getLast? = L.reverse.findSome? fun l => l.getLast? := by
+theorem getLast?_join {L : List (List α)} :
+    (join L).getLast? = L.reverse.findSome? fun l => l.getLast? := by
  simp [← bind_id, getLast?_bind]

 theorem getLast?_replicate (a : α) (n : Nat) : (replicate n a).getLast? = if n = 0 then none else some a := by
@@ -2900,7 +2880,7 @@ theorem head?_dropLast (xs : List α) : xs.dropLast.head? = if 1 < xs.length the

 theorem getLast_dropLast {xs : List α} (h) :
   xs.dropLast.getLast h =
-     xs[xs.length - 2]'(match xs, h with | (_ :: _ :: _), _ => Nat.lt_trans (Nat.lt_add_one _) (Nat.lt_add_one _)) := by
+     xs[xs.length - 2]'(match xs, h with | (a :: b :: xs), _ => Nat.lt_trans (Nat.lt_add_one _) (Nat.lt_add_one _)) := by
  rw [getLast_eq_getElem, getElem_dropLast]
  congr 1
  simp; rfl
@@ -2924,8 +2904,8 @@ theorem dropLast_cons_of_ne_nil {α : Type u} {x : α}

 theorem dropLast_concat_getLast : ∀ {l : List α} (h : l ≠ []), dropLast l ++ [getLast l h] = l
  | [], h => absurd rfl h
-  | [_], _ => rfl
-  | _ :: b :: l, _ => by
+  | [a], h => rfl
+  | a :: b :: l, h => by
    rw [dropLast_cons₂, cons_append, getLast_cons (cons_ne_nil _ _)]
    congr
    exact dropLast_concat_getLast (cons_ne_nil b l)
@@ -3290,16 +3270,12 @@ theorem all_eq_not_any_not (l : List α) (p : α → Bool) : l.all p = !l.any (!
  | nil => rfl
  | cons h t ih => simp_all [Bool.and_assoc]

-@[simp] theorem any_flatten {l : List (List α)} : l.flatten.any f = l.any (any · f) := by
+@[simp] theorem any_join {l : List (List α)} : l.join.any f = l.any (any · f) := by
  induction l <;> simp_all

-@[deprecated any_flatten (since := "2024-10-14")] abbrev any_join := @any_flatten
-
-@[simp] theorem all_flatten {l : List (List α)} : l.flatten.all f = l.all (all · f) := by
+@[simp] theorem all_join {l : List (List α)} : l.join.all f = l.all (all · f) := by
  induction l <;> simp_all

-@[deprecated all_flatten (since := "2024-10-14")] abbrev all_join := @all_flatten
-
@[simp] theorem any_bind {l : List α} {f : α → List β} :
    (l.bind f).any p = l.any fun a => (f a).any p := by
  induction l <;> simp_all
@@ -3330,47 +3306,4 @@ theorem all_eq_not_any_not (l : List α) (p : α → Bool) : l.all p = !l.any (!
    (l.insert a).all f = (f a && l.all f) := by
  simp [all_eq]

-/-! ### Deprecations -/
-
-
-@[deprecated flatten_nil (since := "2024-10-14")] abbrev join_nil := @flatten_nil
-@[deprecated flatten_cons (since := "2024-10-14")] abbrev join_cons := @flatten_cons
-@[deprecated length_flatten (since := "2024-10-14")] abbrev length_join := @length_flatten
-@[deprecated flatten_singleton (since := "2024-10-14")] abbrev join_singleton := @flatten_singleton
-@[deprecated mem_flatten (since := "2024-10-14")] abbrev mem_join := @mem_flatten
-@[deprecated flatten_eq_nil_iff (since := "2024-09-05")] abbrev join_eq_nil := @flatten_eq_nil_iff
-@[deprecated flatten_eq_nil_iff (since := "2024-10-14")] abbrev join_eq_nil_iff := @flatten_eq_nil_iff
-@[deprecated flatten_ne_nil_iff (since := "2024-09-05")] abbrev join_ne_nil := @flatten_ne_nil_iff
-@[deprecated flatten_ne_nil_iff (since := "2024-10-14")] abbrev join_ne_nil_iff := @flatten_ne_nil_iff
-@[deprecated exists_of_mem_flatten (since := "2024-10-14")] abbrev exists_of_mem_join := @exists_of_mem_flatten
-@[deprecated mem_flatten_of_mem (since := "2024-10-14")] abbrev mem_join_of_mem := @mem_flatten_of_mem
-@[deprecated forall_mem_flatten (since := "2024-10-14")] abbrev forall_mem_join := @forall_mem_flatten
-@[deprecated flatten_eq_bind (since := "2024-10-14")] abbrev join_eq_bind := @flatten_eq_bind
-@[deprecated head?_flatten (since := "2024-10-14")] abbrev head?_join := @head?_flatten
-@[deprecated foldl_flatten (since := "2024-10-14")] abbrev foldl_join := @foldl_flatten
-@[deprecated foldr_flatten (since := "2024-10-14")] abbrev foldr_join := @foldr_flatten
-@[deprecated map_flatten (since := "2024-10-14")] abbrev map_join := @map_flatten
-@[deprecated filterMap_flatten (since := "2024-10-14")] abbrev filterMap_join := @filterMap_flatten
-@[deprecated filter_flatten (since := "2024-10-14")] abbrev filter_join := @filter_flatten
-@[deprecated flatten_filter_not_isEmpty (since := "2024-10-14")] abbrev join_filter_not_isEmpty := @flatten_filter_not_isEmpty
-@[deprecated flatten_filter_ne_nil (since := "2024-10-14")] abbrev join_filter_ne_nil := @flatten_filter_ne_nil
-@[deprecated filter_flatten (since := "2024-08-26")]
-theorem join_map_filter (p : α → Bool) (l : List (List α)) :
-    (l.map (filter p)).flatten = (l.flatten).filter p := by
-  rw [filter_flatten]
-@[deprecated flatten_append (since := "2024-10-14")] abbrev join_append := @flatten_append
-@[deprecated flatten_concat (since := "2024-10-14")] abbrev join_concat := @flatten_concat
-@[deprecated flatten_flatten (since := "2024-10-14")] abbrev join_join := @flatten_flatten
-@[deprecated flatten_eq_cons_iff (since := "2024-09-05")] abbrev join_eq_cons_iff := @flatten_eq_cons_iff
-@[deprecated flatten_eq_cons_iff (since := "2024-09-05")] abbrev join_eq_cons := @flatten_eq_cons_iff
-@[deprecated flatten_eq_append_iff (since := "2024-09-05")] abbrev join_eq_append := @flatten_eq_append_iff
-@[deprecated flatten_eq_append_iff (since := "2024-10-14")] abbrev join_eq_append_iff := @flatten_eq_append_iff
-@[deprecated eq_iff_flatten_eq (since := "2024-10-14")] abbrev eq_iff_join_eq := @eq_iff_flatten_eq
-@[deprecated flatten_replicate_nil (since := "2024-10-14")] abbrev join_replicate_nil := @flatten_replicate_nil
-@[deprecated flatten_replicate_singleton (since := "2024-10-14")] abbrev join_replicate_singleton := @flatten_replicate_singleton
-@[deprecated flatten_replicate_replicate (since := "2024-10-14")] abbrev join_replicate_replicate := @flatten_replicate_replicate
-@[deprecated reverse_flatten (since := "2024-10-14")] abbrev reverse_join := @reverse_flatten
-@[deprecated flatten_reverse (since := "2024-10-14")] abbrev join_reverse := @flatten_reverse
-@[deprecated getLast?_flatten (since := "2024-10-14")] abbrev getLast?_join := @getLast?_flatten
-
 end List
--- a/src/Init/Data/List/MapIdx.lean
+++ b/src/Init/Data/List/MapIdx.lean
@@ -1,248 +0,0 @@
-/-
-Copyright (c) 2024 Lean FRO. All rights reserved.
-Released under Apache 2.0 license as described in the file LICENSE.
-Authors: Kim Morrison, Mario Carneiro
-/
-
-prelude
-import Init.Data.Array.Lemmas
-import Init.Data.List.Nat.Range
-
-namespace List
-
-/-! ## Operations using indexes -/
-
-/-! ### mapIdx -/
-
-/--
-Given a function `f : Nat → α → β` and `as : list α`, `as = [a₀, a₁, ...]`, returns the list
-`[f 0 a₀, f 1 a₁, ...]`.
-/
-@[inline] def mapIdx (f : Nat → α → β) (as : List α) : List β := go as #[] where
-  /-- Auxiliary for `mapIdx`:
-  `mapIdx.go [a₀, a₁, ...] acc = acc.toList ++ [f acc.size a₀, f (acc.size + 1) a₁, ...]` -/
-  @[specialize] go : List α → Array β → List β
-  | [], acc => acc.toList
-  | a :: as, acc => go as (acc.push (f acc.size a))
-
-@[simp]
-theorem mapIdx_nil {f : Nat → α → β} : mapIdx f [] = [] :=
-  rfl
-
-theorem mapIdx_go_append  {l₁ l₂ : List α} {arr : Array β} :
-    mapIdx.go f (l₁ ++ l₂) arr = mapIdx.go f l₂ (List.toArray (mapIdx.go f l₁ arr)) := by
-  generalize h : (l₁ ++ l₂).length = len
-  induction len generalizing l₁ arr with
-  | zero =>
-    have l₁_nil : l₁ = [] := by
-      cases l₁
-      · rfl
-      · contradiction
-    have l₂_nil : l₂ = [] := by
-      cases l₂
-      · rfl
-      · rw [List.length_append] at h; contradiction
-    rw [l₁_nil, l₂_nil]; simp only [mapIdx.go, List.toArray_toList]
-  | succ len ih =>
-    cases l₁ with
-    | nil =>
-      simp only [mapIdx.go, nil_append, List.toArray_toList]
-    | cons head tail =>
-      simp only [mapIdx.go, List.append_eq]
-      rw [ih]
-      · simp only [cons_append, length_cons, length_append, Nat.succ.injEq] at h
-        simp only [length_append, h]
-
-theorem mapIdx_go_length {arr : Array β} :
-    length (mapIdx.go f l arr) = length l + arr.size := by
-  induction l generalizing arr with
-  | nil => simp only [mapIdx.go, length_nil, Nat.zero_add]
-  | cons _ _ ih =>
-    simp only [mapIdx.go, ih, Array.size_push, Nat.add_succ, length_cons, Nat.add_comm]
-
-@[simp] theorem mapIdx_concat {l : List α} {e : α} :
-    mapIdx f (l ++ [e]) = mapIdx f l ++ [f l.length e] := by
-  unfold mapIdx
-  rw [mapIdx_go_append]
-  simp only [mapIdx.go, Array.size_toArray, mapIdx_go_length, length_nil, Nat.add_zero,
-    Array.push_toList]
-
-@[simp] theorem mapIdx_singleton {a : α} : mapIdx f [a] = [f 0 a] := by
-  simpa using mapIdx_concat (l := [])
-
-theorem length_mapIdx_go : ∀ {l : List α} {arr : Array β},
-    (mapIdx.go f l arr).length = l.length + arr.size
-  | [], _ => by simp [mapIdx.go]
-  | a :: l, _ => by
-    simp only [mapIdx.go, length_cons]
-    rw [length_mapIdx_go]
-    simp
-    omega
-
-@[simp] theorem length_mapIdx {l : List α} : (l.mapIdx f).length = l.length := by
-  simp [mapIdx, length_mapIdx_go]
-
-theorem getElem?_mapIdx_go : ∀ {l : List α} {arr : Array β} {i : Nat},
-    (mapIdx.go f l arr)[i]? =
-      if h : i < arr.size then some arr[i] else Option.map (f i) l[i - arr.size]?
-  | [], arr, i => by
-    simp only [mapIdx.go, Array.toListImpl_eq, getElem?_eq, Array.length_toList,
-      Array.getElem_eq_getElem_toList, length_nil, Nat.not_lt_zero, ↓reduceDIte, Option.map_none']
-  | a :: l, arr, i => by
-    rw [mapIdx.go, getElem?_mapIdx_go]
-    simp only [Array.size_push]
-    split <;> split
-    · simp only [Option.some.injEq]
-      rw [Array.getElem_eq_getElem_toList]
-      simp only [Array.push_toList]
-      rw [getElem_append_left, Array.getElem_eq_getElem_toList]
-    · have : i = arr.size := by omega
-      simp_all
-    · omega
-    · have : i - arr.size = i - (arr.size + 1) + 1 := by omega
-      simp_all
-
-@[simp] theorem getElem?_mapIdx {l : List α} {i : Nat} :
-    (l.mapIdx f)[i]? = Option.map (f i) l[i]? := by
-  simp [mapIdx, getElem?_mapIdx_go]
-
-@[simp] theorem getElem_mapIdx {l : List α} {f : Nat → α → β} {i : Nat} {h : i < (l.mapIdx f).length} :
-    (l.mapIdx f)[i] = f i (l[i]'(by simpa using h)) := by
-  apply Option.some_inj.mp
-  rw [← getElem?_eq_getElem, getElem?_mapIdx, getElem?_eq_getElem (by simpa using h)]
-  simp
-
-theorem mapIdx_eq_enum_map {l : List α} :
-    l.mapIdx f = l.enum.map (Function.uncurry f) := by
-  ext1 i
-  simp only [getElem?_mapIdx, Option.map, getElem?_map, getElem?_enum]
-  split <;> simp
-
-@[simp]
-theorem mapIdx_cons {l : List α} {a : α} :
-    mapIdx f (a :: l) = f 0 a :: mapIdx (fun i => f (i + 1)) l := by
-  simp [mapIdx_eq_enum_map, enum_eq_zip_range, map_uncurry_zip_eq_zipWith,
-    range_succ_eq_map, zipWith_map_left]
-
-theorem mapIdx_append {K L : List α} :
-    (K ++ L).mapIdx f = K.mapIdx f ++ L.mapIdx fun i => f (i + K.length) := by
-  induction K generalizing f with
-  | nil => rfl
-  | cons _ _ ih => simp [ih (f := fun i => f (i + 1)), Nat.add_assoc]
-
-@[simp]
-theorem mapIdx_eq_nil_iff {l : List α} : List.mapIdx f l = [] ↔ l = [] := by
-  rw [List.mapIdx_eq_enum_map, List.map_eq_nil_iff, List.enum_eq_nil]
-
-theorem mapIdx_ne_nil_iff {l : List α} :
-    List.mapIdx f l ≠ [] ↔ l ≠ [] := by
-  simp
-
-theorem exists_of_mem_mapIdx {b : β} {l : List α}
-    (h : b ∈ mapIdx f l) : ∃ (i : Nat) (h : i < l.length), f i l[i] = b := by
-  rw [mapIdx_eq_enum_map] at h
-  replace h := exists_of_mem_map h
-  simp only [Prod.exists, mk_mem_enum_iff_getElem?, Function.uncurry_apply_pair] at h
-  obtain ⟨i, b, h, rfl⟩ := h
-  rw [getElem?_eq_some_iff] at h
-  obtain ⟨h, rfl⟩ := h
-  exact ⟨i, h, rfl⟩
-
-@[simp] theorem mem_mapIdx {b : β} {l : List α} :
-    b ∈ mapIdx f l ↔ ∃ (i : Nat) (h : i < l.length), f i l[i] = b := by
-  constructor
-  · intro h
-    exact exists_of_mem_mapIdx h
-  · rintro ⟨i, h, rfl⟩
-    rw [mem_iff_getElem]
-    exact ⟨i, by simpa using h, by simp⟩
-
-theorem mapIdx_eq_cons_iff {l : List α} {b : β} :
-    mapIdx f l = b :: l₂ ↔
-      ∃ (a : α) (l₁ : List α), l = a :: l₁ ∧ f 0 a = b ∧ mapIdx (fun i => f (i + 1)) l₁ = l₂ := by
-  cases l <;> simp [and_assoc]
-
-theorem mapIdx_eq_cons_iff' {l : List α} {b : β} :
-    mapIdx f l = b :: l₂ ↔
-      l.head?.map (f 0) = some b ∧ l.tail?.map (mapIdx fun i => f (i + 1)) = some l₂ := by
-  cases l <;> simp
-
-theorem mapIdx_eq_iff {l : List α} : mapIdx f l = l' ↔ ∀ i : Nat, l'[i]? = l[i]?.map (f i) := by
-  constructor
-  · intro w i
-    simpa using congrArg (fun l => l[i]?) w.symm
-  · intro w
-    ext1 i
-    simp [w]
-
-theorem mapIdx_eq_mapIdx_iff {l : List α} :
-    mapIdx f l = mapIdx g l ↔ ∀ i : Nat, (h : i < l.length) → f i l[i] = g i l[i] := by
-  constructor
-  · intro w i h
-    simpa [h] using congrArg (fun l => l[i]?) w
-  · intro w
-    apply ext_getElem
-    · simp
-    · intro i h₁ h₂
-      simp [w]
-
-@[simp] theorem mapIdx_set {l : List α} {i : Nat} {a : α} :
-    (l.set i a).mapIdx f = (l.mapIdx f).set i (f i a) := by
-  simp only [mapIdx_eq_iff, getElem?_set, length_mapIdx, getElem?_mapIdx]
-  intro i
-  split
-  · split <;> simp_all
-  · rfl
-
-@[simp] theorem head_mapIdx {l : List α} {f : Nat → α → β} {w : mapIdx f l ≠ []} :
-    (mapIdx f l).head w = f 0 (l.head (by simpa using w)) := by
-  cases l with
-  | nil => simp at w
-  | cons _ _ => simp
-
-@[simp] theorem head?_mapIdx {l : List α} {f : Nat → α → β} : (mapIdx f l).head? = l.head?.map (f 0) := by
-  cases l <;> simp
-
-@[simp] theorem getLast_mapIdx {l : List α} {f : Nat → α → β} {h} :
-    (mapIdx f l).getLast h = f (l.length - 1) (l.getLast (by simpa using h)) := by
-  cases l with
-  | nil => simp at h
-  | cons _ _ =>
-    simp only [← getElem_cons_length _ _ _ rfl]
-    simp only [mapIdx_cons]
-    simp only [← getElem_cons_length _ _ _ rfl]
-    simp only [← mapIdx_cons, getElem_mapIdx]
-    simp
-
-@[simp] theorem getLast?_mapIdx {l : List α} {f : Nat → α → β} :
-    (mapIdx f l).getLast? = (getLast? l).map (f (l.length - 1)) := by
-  cases l
-  · simp
-  · rw [getLast?_eq_getLast, getLast?_eq_getLast, getLast_mapIdx] <;> simp
-
-@[simp] theorem mapIdx_mapIdx {l : List α} {f : Nat → α → β} {g : Nat → β → γ} :
-    (l.mapIdx f).mapIdx g = l.mapIdx (fun i => g i ∘ f i) := by
-  simp [mapIdx_eq_iff]
-
-theorem mapIdx_eq_replicate_iff {l : List α} {f : Nat → α → β} {b : β} :
-    mapIdx f l = replicate l.length b ↔ ∀ (i : Nat) (h : i < l.length), f i l[i] = b := by
-  simp only [eq_replicate_iff, length_mapIdx, mem_mapIdx, forall_exists_index, true_and]
-  constructor
-  · intro w i h
-    apply w _ _ _ rfl
-  · rintro w _ i h rfl
-    exact w i h
-
-@[simp] theorem mapIdx_reverse {l : List α} {f : Nat → α → β} :
-    l.reverse.mapIdx f = (mapIdx (fun i => f (l.length - 1 - i)) l).reverse := by
-  simp [mapIdx_eq_iff]
-  intro i
-  by_cases h : i < l.length
-  · simp [getElem?_reverse, h]
-    congr
-    omega
-  · simp at h
-    rw [getElem?_eq_none (by simp [h]), getElem?_eq_none (by simp [h])]
-    simp
-
-end List
--- a/src/Init/Data/List/MinMax.lean
+++ b/src/Init/Data/List/MinMax.lean
@@ -7,7 +7,7 @@ prelude
 import Init.Data.List.Lemmas

 /-!
-# Lemmas about `List.min?` and `List.max?.
+# Lemmas about `List.minimum?` and `List.maximum?.
 -/

 namespace List
@@ -16,32 +16,24 @@ open Nat

 /-! ## Minima and maxima -/

-/-! ### min? -/
+/-! ### minimum? -/

-@[simp] theorem min?_nil [Min α] : ([] : List α).min? = none := rfl
+@[simp] theorem minimum?_nil [Min α] : ([] : List α).minimum? = none := rfl

-- We don't put `@[simp]` on `min?_cons'`,
+-- We don't put `@[simp]` on `minimum?_cons`,
 -- because the definition in terms of `foldl` is not useful for proofs.
-theorem min?_cons' [Min α] {xs : List α} : (x :: xs).min? = foldl min x xs := rfl
+theorem minimum?_cons [Min α] {xs : List α} : (x :: xs).minimum? = foldl min x xs := rfl

-@[simp] theorem min?_cons [Min α] [Std.Associative (min : α → α → α)] {xs : List α} :
-    (x :: xs).min? = some (xs.min?.elim x (min x)) := by
-  cases xs <;> simp [min?_cons', foldl_assoc]
+@[simp] theorem minimum?_eq_none_iff {xs : List α} [Min α] : xs.minimum? = none ↔ xs = [] := by
+  cases xs <;> simp [minimum?]

-@[simp] theorem min?_eq_none_iff {xs : List α} [Min α] : xs.min? = none ↔ xs = [] := by
-  cases xs <;> simp [min?]
-
-theorem isSome_min?_of_mem {l : List α} [Min α] {a : α} (h : a ∈ l) :
-    l.min?.isSome := by
-  cases l <;> simp_all [List.min?_cons']
-
-theorem min?_mem [Min α] (min_eq_or : ∀ a b : α, min a b = a ∨ min a b = b) :
-    {xs : List α} → xs.min? = some a → a ∈ xs := by
+theorem minimum?_mem [Min α] (min_eq_or : ∀ a b : α, min a b = a ∨ min a b = b) :
+    {xs : List α} → xs.minimum? = some a → a ∈ xs := by
  intro xs
  match xs with
  | nil => simp
  | x :: xs =>
-    simp only [min?_cons', Option.some.injEq, List.mem_cons]
+    simp only [minimum?_cons, Option.some.injEq, List.mem_cons]
    intro eq
    induction xs generalizing x with
    | nil =>
@@ -57,12 +49,12 @@ theorem min?_mem [Min α] (min_eq_or : ∀ a b : α, min a b = a ∨ min a b = b

 -- See also `Init.Data.List.Nat.Basic` for specialisations of the next two results to `Nat`.

-theorem le_min?_iff [Min α] [LE α]
+theorem le_minimum?_iff [Min α] [LE α]
    (le_min_iff : ∀ a b c : α, a ≤ min b c ↔ a ≤ b ∧ a ≤ c) :
-    {xs : List α} → xs.min? = some a → ∀ {x}, x ≤ a ↔ ∀ b, b ∈ xs → x ≤ b
+    {xs : List α} → xs.minimum? = some a → ∀ {x}, x ≤ a ↔ ∀ b, b ∈ xs → x ≤ b
  | nil => by simp
  | cons x xs => by
-    rw [min?]
+    rw [minimum?]
    intro eq y
    simp only [Option.some.injEq] at eq
    induction xs generalizing x with
@@ -75,58 +67,46 @@ theorem le_min?_iff [Min α] [LE α]

 -- This could be refactored by designing appropriate typeclasses to replace `le_refl`, `min_eq_or`,
 -- and `le_min_iff`.
-theorem min?_eq_some_iff [Min α] [LE α] [anti : Antisymm ((· : α) ≤ ·)]
+theorem minimum?_eq_some_iff [Min α] [LE α] [anti : Antisymm ((· : α) ≤ ·)]
    (le_refl : ∀ a : α, a ≤ a)
    (min_eq_or : ∀ a b : α, min a b = a ∨ min a b = b)
    (le_min_iff : ∀ a b c : α, a ≤ min b c ↔ a ≤ b ∧ a ≤ c) {xs : List α} :
-    xs.min? = some a ↔ a ∈ xs ∧ ∀ b, b ∈ xs → a ≤ b := by
-  refine ⟨fun h => ⟨min?_mem min_eq_or h, (le_min?_iff le_min_iff h).1 (le_refl _)⟩, ?_⟩
+    xs.minimum? = some a ↔ a ∈ xs ∧ ∀ b, b ∈ xs → a ≤ b := by
+  refine ⟨fun h => ⟨minimum?_mem min_eq_or h, (le_minimum?_iff le_min_iff h).1 (le_refl _)⟩, ?_⟩
  intro ⟨h₁, h₂⟩
  cases xs with
  | nil => simp at h₁
  | cons x xs =>
    exact congrArg some <| anti.1
-      ((le_min?_iff le_min_iff (xs := x::xs) rfl).1 (le_refl _) _ h₁)
-      (h₂ _ (min?_mem min_eq_or (xs := x::xs) rfl))
+      ((le_minimum?_iff le_min_iff (xs := x::xs) rfl).1 (le_refl _) _ h₁)
+      (h₂ _ (minimum?_mem min_eq_or (xs := x::xs) rfl))

-theorem min?_replicate [Min α] {n : Nat} {a : α} (w : min a a = a) :
-    (replicate n a).min? = if n = 0 then none else some a := by
+theorem minimum?_replicate [Min α] {n : Nat} {a : α} (w : min a a = a) :
+    (replicate n a).minimum? = if n = 0 then none else some a := by
  induction n with
  | zero => rfl
-  | succ n ih => cases n <;> simp_all [replicate_succ, min?_cons']
+  | succ n ih => cases n <;> simp_all [replicate_succ, minimum?_cons]

-@[simp] theorem min?_replicate_of_pos [Min α] {n : Nat} {a : α} (w : min a a = a) (h : 0 < n) :
-    (replicate n a).min? = some a := by
-  simp [min?_replicate, Nat.ne_of_gt h, w]
+@[simp] theorem minimum?_replicate_of_pos [Min α] {n : Nat} {a : α} (w : min a a = a) (h : 0 < n) :
+    (replicate n a).minimum? = some a := by
+  simp [minimum?_replicate, Nat.ne_of_gt h, w]

-theorem foldl_min [Min α] [Std.IdempotentOp (min : α → α → α)] [Std.Associative (min : α → α → α)]
-    {l : List α} {a : α} : l.foldl (init := a) min = min a (l.min?.getD a) := by
-  cases l <;> simp [min?, foldl_assoc, Std.IdempotentOp.idempotent]
+/-! ### maximum? -/

-/-! ### max? -/
+@[simp] theorem maximum?_nil [Max α] : ([] : List α).maximum? = none := rfl

-@[simp] theorem max?_nil [Max α] : ([] : List α).max? = none := rfl
-
-- We don't put `@[simp]` on `max?_cons'`,
+-- We don't put `@[simp]` on `maximum?_cons`,
 -- because the definition in terms of `foldl` is not useful for proofs.
-theorem max?_cons' [Max α] {xs : List α} : (x :: xs).max? = foldl max x xs := rfl
+theorem maximum?_cons [Max α] {xs : List α} : (x :: xs).maximum? = foldl max x xs := rfl

-@[simp] theorem max?_cons [Max α] [Std.Associative (max : α → α → α)] {xs : List α} :
-    (x :: xs).max? = some (xs.max?.elim x (max x)) := by
-  cases xs <;> simp [max?_cons', foldl_assoc]
+@[simp] theorem maximum?_eq_none_iff {xs : List α} [Max α] : xs.maximum? = none ↔ xs = [] := by
+  cases xs <;> simp [maximum?]

-@[simp] theorem max?_eq_none_iff {xs : List α} [Max α] : xs.max? = none ↔ xs = [] := by
-  cases xs <;> simp [max?]
-
-theorem isSome_max?_of_mem {l : List α} [Max α] {a : α} (h : a ∈ l) :
-    l.max?.isSome := by
-  cases l <;> simp_all [List.max?_cons']
-
-theorem max?_mem [Max α] (min_eq_or : ∀ a b : α, max a b = a ∨ max a b = b) :
-    {xs : List α} → xs.max? = some a → a ∈ xs
+theorem maximum?_mem [Max α] (min_eq_or : ∀ a b : α, max a b = a ∨ max a b = b) :
+    {xs : List α} → xs.maximum? = some a → a ∈ xs
  | nil => by simp
  | cons x xs => by
-    rw [max?]; rintro ⟨⟩
+    rw [maximum?]; rintro ⟨⟩
    induction xs generalizing x with simp at *
    | cons y xs ih =>
      rcases ih (max x y) with h | h <;> simp [h]
@@ -134,61 +114,40 @@ theorem max?_mem [Max α] (min_eq_or : ∀ a b : α, max a b = a ∨ max a b = b

 -- See also `Init.Data.List.Nat.Basic` for specialisations of the next two results to `Nat`.

-theorem max?_le_iff [Max α] [LE α]
+theorem maximum?_le_iff [Max α] [LE α]
    (max_le_iff : ∀ a b c : α, max b c ≤ a ↔ b ≤ a ∧ c ≤ a) :
-    {xs : List α} → xs.max? = some a → ∀ {x}, a ≤ x ↔ ∀ b ∈ xs, b ≤ x
+    {xs : List α} → xs.maximum? = some a → ∀ {x}, a ≤ x ↔ ∀ b ∈ xs, b ≤ x
  | nil => by simp
  | cons x xs => by
-    rw [max?]; rintro ⟨⟩ y
+    rw [maximum?]; rintro ⟨⟩ y
    induction xs generalizing x with
    | nil => simp
    | cons y xs ih => simp [ih, max_le_iff, and_assoc]

 -- This could be refactored by designing appropriate typeclasses to replace `le_refl`, `max_eq_or`,
 -- and `le_min_iff`.
-theorem max?_eq_some_iff [Max α] [LE α] [anti : Antisymm ((· : α) ≤ ·)]
+theorem maximum?_eq_some_iff [Max α] [LE α] [anti : Antisymm ((· : α) ≤ ·)]
    (le_refl : ∀ a : α, a ≤ a)
    (max_eq_or : ∀ a b : α, max a b = a ∨ max a b = b)
    (max_le_iff : ∀ a b c : α, max b c ≤ a ↔ b ≤ a ∧ c ≤ a) {xs : List α} :
-    xs.max? = some a ↔ a ∈ xs ∧ ∀ b ∈ xs, b ≤ a := by
-  refine ⟨fun h => ⟨max?_mem max_eq_or h, (max?_le_iff max_le_iff h).1 (le_refl _)⟩, ?_⟩
+    xs.maximum? = some a ↔ a ∈ xs ∧ ∀ b ∈ xs, b ≤ a := by
+  refine ⟨fun h => ⟨maximum?_mem max_eq_or h, (maximum?_le_iff max_le_iff h).1 (le_refl _)⟩, ?_⟩
  intro ⟨h₁, h₂⟩
  cases xs with
  | nil => simp at h₁
  | cons x xs =>
    exact congrArg some <| anti.1
-      (h₂ _ (max?_mem max_eq_or (xs := x::xs) rfl))
-      ((max?_le_iff max_le_iff (xs := x::xs) rfl).1 (le_refl _) _ h₁)
+      (h₂ _ (maximum?_mem max_eq_or (xs := x::xs) rfl))
+      ((maximum?_le_iff max_le_iff (xs := x::xs) rfl).1 (le_refl _) _ h₁)

-theorem max?_replicate [Max α] {n : Nat} {a : α} (w : max a a = a) :
-    (replicate n a).max? = if n = 0 then none else some a := by
+theorem maximum?_replicate [Max α] {n : Nat} {a : α} (w : max a a = a) :
+    (replicate n a).maximum? = if n = 0 then none else some a := by
  induction n with
  | zero => rfl
-  | succ n ih => cases n <;> simp_all [replicate_succ, max?_cons']
+  | succ n ih => cases n <;> simp_all [replicate_succ, maximum?_cons]

-@[simp] theorem max?_replicate_of_pos [Max α] {n : Nat} {a : α} (w : max a a = a) (h : 0 < n) :
-    (replicate n a).max? = some a := by
-  simp [max?_replicate, Nat.ne_of_gt h, w]
-
-theorem foldl_max [Max α] [Std.IdempotentOp (max : α → α → α)] [Std.Associative (max : α → α → α)]
-    {l : List α} {a : α} : l.foldl (init := a) max = max a (l.max?.getD a) := by
-  cases l <;> simp [max?, foldl_assoc, Std.IdempotentOp.idempotent]
-
-@[deprecated min?_nil (since := "2024-09-29")] abbrev minimum?_nil := @min?_nil
-@[deprecated min?_cons (since := "2024-09-29")] abbrev minimum?_cons := @min?_cons
-@[deprecated min?_eq_none_iff (since := "2024-09-29")] abbrev mininmum?_eq_none_iff := @min?_eq_none_iff
-@[deprecated min?_mem (since := "2024-09-29")] abbrev minimum?_mem := @min?_mem
-@[deprecated le_min?_iff (since := "2024-09-29")] abbrev le_minimum?_iff := @le_min?_iff
-@[deprecated min?_eq_some_iff (since := "2024-09-29")] abbrev minimum?_eq_some_iff := @min?_eq_some_iff
-@[deprecated min?_replicate (since := "2024-09-29")] abbrev minimum?_replicate := @min?_replicate
-@[deprecated min?_replicate_of_pos (since := "2024-09-29")] abbrev minimum?_replicate_of_pos := @min?_replicate_of_pos
-@[deprecated max?_nil (since := "2024-09-29")] abbrev maximum?_nil := @max?_nil
-@[deprecated max?_cons (since := "2024-09-29")] abbrev maximum?_cons := @max?_cons
-@[deprecated max?_eq_none_iff (since := "2024-09-29")] abbrev maximum?_eq_none_iff := @max?_eq_none_iff
-@[deprecated max?_mem (since := "2024-09-29")] abbrev maximum?_mem := @max?_mem
-@[deprecated max?_le_iff (since := "2024-09-29")] abbrev maximum?_le_iff := @max?_le_iff
-@[deprecated max?_eq_some_iff (since := "2024-09-29")] abbrev maximum?_eq_some_iff := @max?_eq_some_iff
-@[deprecated max?_replicate (since := "2024-09-29")] abbrev maximum?_replicate := @max?_replicate
-@[deprecated max?_replicate_of_pos (since := "2024-09-29")] abbrev maximum?_replicate_of_pos := @max?_replicate_of_pos
+@[simp] theorem maximum?_replicate_of_pos [Max α] {n : Nat} {a : α} (w : max a a = a) (h : 0 < n) :
+    (replicate n a).maximum? = some a := by
+  simp [maximum?_replicate, Nat.ne_of_gt h, w]

 end List
--- a/src/Init/Data/List/Monadic.lean
+++ b/src/Init/Data/List/Monadic.lean
@@ -51,27 +51,6 @@ theorem mapM'_eq_mapM [Monad m] [LawfulMonad m] (f : α → m β) (l : List α)
@[simp] theorem mapM_append [Monad m] [LawfulMonad m] (f : α → m β) {l₁ l₂ : List α} :
    (l₁ ++ l₂).mapM f = (return (← l₁.mapM f) ++ (← l₂.mapM f)) := by induction l₁ <;> simp [*]

-/-- Auxiliary lemma for `mapM_eq_reverse_foldlM_cons`. -/
-theorem foldlM_cons_eq_append [Monad m] [LawfulMonad m] (f : α → m β) (as : List α) (b : β) (bs : List β) :
-    (as.foldlM (init := b :: bs) fun acc a => return ((← f a) :: acc)) =
-      (· ++ b :: bs) <$> as.foldlM (init := []) fun acc a => return ((← f a) :: acc) := by
-  induction as generalizing b bs with
-  | nil => simp
-  | cons a as ih =>
-    simp only [bind_pure_comp] at ih
-    simp [ih, _root_.map_bind, Functor.map_map, Function.comp_def]
-
-theorem mapM_eq_reverse_foldlM_cons [Monad m] [LawfulMonad m] (f : α → m β) (l : List α) :
-    mapM f l = reverse <$> (l.foldlM (fun acc a => return ((← f a) :: acc)) []) := by
-  rw [← mapM'_eq_mapM]
-  induction l with
-  | nil => simp
-  | cons a as ih =>
-    simp only [mapM'_cons, ih, bind_map_left, foldlM_cons, LawfulMonad.bind_assoc, pure_bind,
-      foldlM_cons_eq_append, _root_.map_bind, Functor.map_map, Function.comp_def, reverse_append,
-      reverse_cons, reverse_nil, nil_append, singleton_append]
-    simp [bind_pure_comp]
-
 /-! ### forM -/

 -- We use `List.forM` as the simp normal form, rather that `ForM.forM`.
@@ -87,16 +66,4 @@ theorem mapM_eq_reverse_foldlM_cons [Monad m] [LawfulMonad m] (f : α → m β)
    (l₁ ++ l₂).forM f = (do l₁.forM f; l₂.forM f) := by
  induction l₁ <;> simp [*]

-/-! ### allM -/
-
-theorem allM_eq_not_anyM_not [Monad m] [LawfulMonad m] (p : α → m Bool) (as : List α) :
-    allM p as = (! ·) <$> anyM ((! ·) <$> p ·) as := by
-  induction as with
-  | nil => simp
-  | cons a as ih =>
-    simp only [allM, anyM, bind_map_left, _root_.map_bind]
-    congr
-    funext b
-    split <;> simp_all
-
 end List
--- a/src/Init/Data/List/Nat/Basic.lean
+++ b/src/Init/Data/List/Nat/Basic.lean
@@ -86,66 +86,164 @@ theorem mem_eraseIdx_iff_getElem? {x : α} {l} {k} : x ∈ eraseIdx l k ↔ ∃
    obtain ⟨h', -⟩ := getElem?_eq_some_iff.1 h
    exact ⟨h', h⟩

-/-! ### min? -/
+/-! ### minimum? -/

-- A specialization of `min?_eq_some_iff` to Nat.
-theorem min?_eq_some_iff' {xs : List Nat} :
-    xs.min? = some a ↔ (a ∈ xs ∧ ∀ b ∈ xs, a ≤ b) :=
-  min?_eq_some_iff
+-- A specialization of `minimum?_eq_some_iff` to Nat.
+theorem minimum?_eq_some_iff' {xs : List Nat} :
+    xs.minimum? = some a ↔ (a ∈ xs ∧ ∀ b ∈ xs, a ≤ b) :=
+  minimum?_eq_some_iff
    (le_refl := Nat.le_refl)
-    (min_eq_or := fun _ _ => Nat.min_def .. ▸ by split <;> simp)
-    (le_min_iff := fun _ _ _ => Nat.le_min)
+    (min_eq_or := fun _ _ => by omega)
+    (le_min_iff := fun _ _ _ => by omega)

-theorem min?_get_le_of_mem {l : List Nat} {a : Nat} (h : a ∈ l) :
-    l.min?.get (isSome_min?_of_mem h) ≤ a := by
-  induction l with
+-- This could be generalized,
+-- but will first require further work on order typeclasses in the core repository.
+theorem minimum?_cons' {a : Nat} {l : List Nat} :
+    (a :: l).minimum? = some (match l.minimum? with
+    | none => a
+    | some m => min a m) := by
+  rw [minimum?_eq_some_iff']
+  split <;> rename_i h m
+  · simp_all
+  · rw [minimum?_eq_some_iff'] at m
+    obtain ⟨m, le⟩ := m
+    rw [Nat.min_def]
+    constructor
+    · split
+      · exact mem_cons_self a l
+      · exact mem_cons_of_mem a m
+    · intro b m
+      cases List.mem_cons.1 m with
+      | inl => split <;> omega
+      | inr h =>
+        specialize le b h
+        split <;> omega
+
+theorem foldl_min
+    {α : Type _} [Min α] [Std.IdempotentOp (min : α → α → α)] [Std.Associative (min : α → α → α)]
+    {l : List α} {a : α} :
+    l.foldl (init := a) min = min a (l.minimum?.getD a) := by
+  cases l with
+  | nil => simp [Std.IdempotentOp.idempotent]
+  | cons b l =>
+    simp only [minimum?]
+    induction l generalizing a b with
+    | nil => simp
+    | cons c l ih => simp [ih, Std.Associative.assoc]
+
+theorem foldl_min_right {α β : Type _}
+    [Min β] [Std.IdempotentOp (min : β → β → β)] [Std.Associative (min : β → β → β)]
+    {l : List α} {b : β} {f : α → β} :
+    (l.foldl (init := b) fun acc a => min acc (f a)) = min b ((l.map f).minimum?.getD b) := by
+  rw [← foldl_map, foldl_min]
+
+theorem foldl_min_le {l : List Nat} {a : Nat} : l.foldl (init := a) min ≤ a := by
+  induction l generalizing a with
+  | nil => simp
+  | cons c l ih =>
+    simp only [foldl_cons]
+    exact Nat.le_trans ih (Nat.min_le_left _ _)
+
+theorem foldl_min_min_of_le {l : List Nat} {a b : Nat} (h : a ≤ b) :
+    l.foldl (init := a) min ≤ b :=
+  Nat.le_trans (foldl_min_le) h
+
+theorem minimum?_getD_le_of_mem {l : List Nat} {a k : Nat} (h : a ∈ l) :
+    l.minimum?.getD k ≤ a := by
+  cases l with
  | nil => simp at h
-  | cons b t ih =>
-    simp only [min?_cons, Option.get_some] at ih ⊢
-    rcases mem_cons.1 h with (rfl|h)
-    · cases t.min? with
-      | none => simp
-      | some b => simpa using Nat.min_le_left _ _
-    · obtain ⟨q, hq⟩ := Option.isSome_iff_exists.1 (isSome_min?_of_mem h)
-      simp only [hq, Option.elim_some] at ih ⊢
-      exact Nat.le_trans (Nat.min_le_right _ _) (ih h)
+  | cons b l =>
+    simp [minimum?_cons]
+    simp at h
+    rcases h with (rfl | h)
+    · exact foldl_min_le
+    · induction l generalizing b with
+      | nil => simp_all
+      | cons c l ih =>
+        simp only [foldl_cons]
+        simp at h
+        rcases h with (rfl | h)
+        · exact foldl_min_min_of_le (Nat.min_le_right _ _)
+        · exact ih _ h

-theorem min?_getD_le_of_mem {l : List Nat} {a k : Nat} (h : a ∈ l) : l.min?.getD k ≤ a :=
-  Option.get_eq_getD _ ▸ min?_get_le_of_mem h
+/-! ### maximum? -/

-/-! ### max? -/
-
-- A specialization of `max?_eq_some_iff` to Nat.
-theorem max?_eq_some_iff' {xs : List Nat} :
-    xs.max? = some a ↔ (a ∈ xs ∧ ∀ b ∈ xs, b ≤ a) :=
-  max?_eq_some_iff
+-- A specialization of `maximum?_eq_some_iff` to Nat.
+theorem maximum?_eq_some_iff' {xs : List Nat} :
+    xs.maximum? = some a ↔ (a ∈ xs ∧ ∀ b ∈ xs, b ≤ a) :=
+  maximum?_eq_some_iff
    (le_refl := Nat.le_refl)
-    (max_eq_or := fun _ _ => Nat.max_def .. ▸ by split <;> simp)
-    (max_le_iff := fun _ _ _ => Nat.max_le)
+    (max_eq_or := fun _ _ => by omega)
+    (max_le_iff := fun _ _ _ => by omega)

-theorem le_max?_get_of_mem {l : List Nat} {a : Nat} (h : a ∈ l) :
-    a ≤ l.max?.get (isSome_max?_of_mem h) := by
-  induction l with
+-- This could be generalized,
+-- but will first require further work on order typeclasses in the core repository.
+theorem maximum?_cons' {a : Nat} {l : List Nat} :
+    (a :: l).maximum? = some (match l.maximum? with
+    | none => a
+    | some m => max a m) := by
+  rw [maximum?_eq_some_iff']
+  split <;> rename_i h m
+  · simp_all
+  · rw [maximum?_eq_some_iff'] at m
+    obtain ⟨m, le⟩ := m
+    rw [Nat.max_def]
+    constructor
+    · split
+      · exact mem_cons_of_mem a m
+      · exact mem_cons_self a l
+    · intro b m
+      cases List.mem_cons.1 m with
+      | inl => split <;> omega
+      | inr h =>
+        specialize le b h
+        split <;> omega
+
+theorem foldl_max
+    {α : Type _} [Max α] [Std.IdempotentOp (max : α → α → α)] [Std.Associative (max : α → α → α)]
+    {l : List α} {a : α} :
+    l.foldl (init := a) max = max a (l.maximum?.getD a) := by
+  cases l with
+  | nil => simp [Std.IdempotentOp.idempotent]
+  | cons b l =>
+    simp only [maximum?]
+    induction l generalizing a b with
+    | nil => simp
+    | cons c l ih => simp [ih, Std.Associative.assoc]
+
+theorem foldl_max_right {α β : Type _}
+    [Max β] [Std.IdempotentOp (max : β → β → β)] [Std.Associative (max : β → β → β)]
+    {l : List α} {b : β} {f : α → β} :
+    (l.foldl (init := b) fun acc a => max acc (f a)) = max b ((l.map f).maximum?.getD b) := by
+  rw [← foldl_map, foldl_max]
+
+theorem le_foldl_max {l : List Nat} {a : Nat} : a ≤ l.foldl (init := a) max := by
+  induction l generalizing a with
+  | nil => simp
+  | cons c l ih =>
+    simp only [foldl_cons]
+    exact Nat.le_trans (Nat.le_max_left _ _) ih
+
+theorem le_foldl_max_of_le {l : List Nat} {a b : Nat} (h : a ≤ b) :
+    a ≤ l.foldl (init := b) max :=
+  Nat.le_trans h (le_foldl_max)
+
+theorem le_maximum?_getD_of_mem {l : List Nat} {a k : Nat} (h : a ∈ l) :
+    a ≤ l.maximum?.getD k := by
+  cases l with
  | nil => simp at h
-  | cons b t ih =>
-    simp only [max?_cons, Option.get_some] at ih ⊢
-    rcases mem_cons.1 h with (rfl|h)
-    · cases t.max? with
-      | none => simp
-      | some b => simpa using Nat.le_max_left _ _
-    · obtain ⟨q, hq⟩ := Option.isSome_iff_exists.1 (isSome_max?_of_mem h)
-      simp only [hq, Option.elim_some] at ih ⊢
-      exact Nat.le_trans (ih h) (Nat.le_max_right _ _)
-
-theorem le_max?_getD_of_mem {l : List Nat} {a k : Nat} (h : a ∈ l) :
-    a ≤ l.max?.getD k :=
-  Option.get_eq_getD _ ▸ le_max?_get_of_mem h
-
-@[deprecated min?_eq_some_iff' (since := "2024-09-29")] abbrev minimum?_eq_some_iff' := @min?_eq_some_iff'
-@[deprecated min?_cons' (since := "2024-09-29")] abbrev minimum?_cons' := @min?_cons'
-@[deprecated min?_getD_le_of_mem (since := "2024-09-29")] abbrev minimum?_getD_le_of_mem := @min?_getD_le_of_mem
-@[deprecated max?_eq_some_iff' (since := "2024-09-29")] abbrev maximum?_eq_some_iff' := @max?_eq_some_iff'
-@[deprecated max?_cons' (since := "2024-09-29")] abbrev maximum?_cons' := @max?_cons'
-@[deprecated le_max?_getD_of_mem (since := "2024-09-29")] abbrev le_maximum?_getD_of_mem := @le_max?_getD_of_mem
+  | cons b l =>
+    simp [maximum?_cons]
+    simp at h
+    rcases h with (rfl | h)
+    · exact le_foldl_max
+    · induction l generalizing b with
+      | nil => simp_all
+      | cons c l ih =>
+        simp only [foldl_cons]
+        simp at h
+        rcases h with (rfl | h)
+        · exact le_foldl_max_of_le (Nat.le_max_right b a)
+        · exact ih _ h

 end List
--- a/src/Init/Data/List/Nat/Erase.lean
+++ b/src/Init/Data/List/Nat/Erase.lean
@@ -10,7 +10,7 @@ import Init.Data.List.Erase
 namespace List

 theorem getElem?_eraseIdx (l : List α) (i : Nat) (j : Nat) :
-    (l.eraseIdx i)[j]? = if j < i then l[j]? else l[j + 1]? := by
+    (l.eraseIdx i)[j]? = if h : j < i then l[j]? else l[j + 1]? := by
  rw [eraseIdx_eq_take_drop_succ, getElem?_append]
  split <;> rename_i h
  · rw [getElem?_take]
--- a/src/Init/Data/List/Nat/Range.lean
+++ b/src/Init/Data/List/Nat/Range.lean
@@ -154,7 +154,7 @@ theorem erase_range' :
 /-! ### range -/

 theorem reverse_range' : ∀ s n : Nat, reverse (range' s n) = map (s + n - 1 - ·) (range n)
-  | _, 0 => rfl
+  | s, 0 => rfl
  | s, n + 1 => by
    rw [range'_1_concat, reverse_append, range_succ_eq_map,
      show s + (n + 1) - 1 = s + n from rfl, map, map_map]
@@ -500,13 +500,4 @@ theorem enum_eq_zip_range (l : List α) : l.enum = (range l.length).zip l :=
 theorem unzip_enum_eq_prod (l : List α) : l.enum.unzip = (range l.length, l) := by
  simp only [enum_eq_zip_range, unzip_zip, length_range]

-theorem enum_eq_cons_iff {l : List α} :
-    l.enum = x :: l' ↔ ∃ a as, l = a :: as ∧ x = (0, a) ∧ l' = enumFrom 1 as := by
-  rw [enum, enumFrom_eq_cons_iff]
-
-theorem enum_eq_append_iff {l : List α} :
-    l.enum = l₁ ++ l₂ ↔
-      ∃ l₁' l₂', l = l₁' ++ l₂' ∧ l₁ = l₁'.enum ∧ l₂ = l₂'.enumFrom l₁'.length := by
-  simp [enum, enumFrom_eq_append_iff]
-
 end List
--- a/src/Init/Data/List/Nat/TakeDrop.lean
+++ b/src/Init/Data/List/Nat/TakeDrop.lean
@@ -42,7 +42,7 @@ theorem getElem_take' (L : List α) {i j : Nat} (hi : i < L.length) (hj : i < j)

 /-- The `i`-th element of a list coincides with the `i`-th element of any of its prefixes of
 length `> i`. Version designed to rewrite from the small list to the big list. -/
-@[simp] theorem getElem_take (L : List α) {j i : Nat} {h : i < (L.take j).length} :
+theorem getElem_take (L : List α) {j i : Nat} {h : i < (L.take j).length} :
    (L.take j)[i] =
    L[i]'(Nat.lt_of_lt_of_le h (length_take_le' _ _)) := by
  rw [length_take, Nat.lt_min] at h; rw [getElem_take' L _ h.1]
@@ -52,7 +52,7 @@ length `> i`. Version designed to rewrite from the big list to the small list. -
@[deprecated getElem_take' (since := "2024-06-12")]
 theorem get_take (L : List α) {i j : Nat} (hi : i < L.length) (hj : i < j) :
    get L ⟨i, hi⟩ = get (L.take j) ⟨i, length_take .. ▸ Nat.lt_min.mpr ⟨hj, hi⟩⟩ := by
-  simp
+  simp [getElem_take' _ hi hj]

 /-- The `i`-th element of a list coincides with the `i`-th element of any of its prefixes of
 length `> i`. Version designed to rewrite from the small list to the big list. -/
--- a/src/Init/Data/List/Pairwise.lean
+++ b/src/Init/Data/List/Pairwise.lean
@@ -160,23 +160,21 @@ theorem pairwise_middle {R : α → α → Prop} (s : ∀ {x y}, R x y → R y x
  rw [← append_assoc, pairwise_append, @pairwise_append _ _ ([a] ++ l₁), pairwise_append_comm s]
  simp only [mem_append, or_comm]

-theorem pairwise_flatten {L : List (List α)} :
-    Pairwise R (flatten L) ↔
+theorem pairwise_join {L : List (List α)} :
+    Pairwise R (join L) ↔
      (∀ l ∈ L, Pairwise R l) ∧ Pairwise (fun l₁ l₂ => ∀ x ∈ l₁, ∀ y ∈ l₂, R x y) L := by
  induction L with
  | nil => simp
  | cons l L IH =>
-    simp only [flatten, pairwise_append, IH, mem_flatten, exists_imp, and_imp, forall_mem_cons,
+    simp only [join, pairwise_append, IH, mem_join, exists_imp, and_imp, forall_mem_cons,
      pairwise_cons, and_assoc, and_congr_right_iff]
    rw [and_comm, and_congr_left_iff]
    intros; exact ⟨fun h a b c d e => h c d e a b, fun h c d e a b => h a b c d e⟩

-@[deprecated pairwise_flatten (since := "2024-10-14")] abbrev pairwise_join := @pairwise_flatten
-
 theorem pairwise_bind {R : β → β → Prop} {l : List α} {f : α → List β} :
    List.Pairwise R (l.bind f) ↔
      (∀ a ∈ l, Pairwise R (f a)) ∧ Pairwise (fun a₁ a₂ => ∀ x ∈ f a₁, ∀ y ∈ f a₂, R x y) l := by
-  simp [List.bind, pairwise_flatten, pairwise_map]
+  simp [List.bind, pairwise_join, pairwise_map]

 theorem pairwise_reverse {l : List α} :
    l.reverse.Pairwise R ↔ l.Pairwise (fun a b => R b a) := by
--- a/src/Init/Data/List/Perm.lean
+++ b/src/Init/Data/List/Perm.lean
@@ -98,8 +98,8 @@ theorem Perm.append_cons (a : α) {h₁ h₂ t₁ t₂ : List α} (p₁ : h₁ ~
  perm_middle.trans <| by rw [append_nil]

 theorem perm_append_comm : ∀ {l₁ l₂ : List α}, l₁ ++ l₂ ~ l₂ ++ l₁
-  | [], _ => by simp
-  | _ :: _, _ => (perm_append_comm.cons _).trans perm_middle.symm
+  | [], l₂ => by simp
+  | a :: t, l₂ => (perm_append_comm.cons _).trans perm_middle.symm

 theorem perm_append_comm_assoc (l₁ l₂ l₃ : List α) :
    Perm (l₁ ++ (l₂ ++ l₃)) (l₂ ++ (l₁ ++ l₃)) := by
@@ -248,10 +248,6 @@ theorem countP_eq_countP_filter_add (l : List α) (p q : α → Bool) :
 theorem Perm.count_eq [DecidableEq α] {l₁ l₂ : List α} (p : l₁ ~ l₂) (a) :
    count a l₁ = count a l₂ := p.countP_eq _

-/-
-This theorem is a variant of `Perm.foldl_eq` defined in Mathlib which uses typeclasses rather
-than the explicit `comm` argument.
-/
 theorem Perm.foldl_eq' {f : β → α → β} {l₁ l₂ : List α} (p : l₁ ~ l₂)
    (comm : ∀ x ∈ l₁, ∀ y ∈ l₁, ∀ (z), f (f z x) y = f (f z y) x)
    (init) : foldl f init l₁ = foldl f init l₂ := by
@@ -268,28 +264,6 @@ theorem Perm.foldl_eq' {f : β → α → β} {l₁ l₂ : List α} (p : l₁ ~
    refine (IH₁ comm init).trans (IH₂ ?_ _)
    intros; apply comm <;> apply p₁.symm.subset <;> assumption

-/-
-This theorem is a variant of `Perm.foldr_eq` defined in Mathlib which uses typeclasses rather
-than the explicit `comm` argument.
-/
-theorem Perm.foldr_eq' {f : α → β → β} {l₁ l₂ : List α} (p : l₁ ~ l₂)
-    (comm : ∀ x ∈ l₁, ∀ y ∈ l₁, ∀ (z), f y (f x z) = f x (f y z))
-    (init) : foldr f init l₁ = foldr f init l₂ := by
-  induction p using recOnSwap' generalizing init with
-  | nil => simp
-  | cons x _p IH =>
-    simp only [foldr]
-    congr 1
-    apply IH; intros; apply comm <;> exact .tail _ ‹_›
-  | swap' x y _p IH =>
-    simp only [foldr]
-    rw [comm x (.tail _ <| .head _) y (.head _)]
-    congr 2
-    apply IH; intros; apply comm <;> exact .tail _ (.tail _ ‹_›)
-  | trans p₁ _p₂ IH₁ IH₂ =>
-    refine (IH₁ comm init).trans (IH₂ ?_ _)
-    intros; apply comm <;> apply p₁.symm.subset <;> assumption
-
 theorem Perm.rec_heq {β : List α → Sort _} {f : ∀ a l, β l → β (a :: l)} {b : β []} {l l' : List α}
    (hl : l ~ l') (f_congr : ∀ {a l l' b b'}, l ~ l' → HEq b b' → HEq (f a l b) (f a l' b'))
    (f_swap : ∀ {a a' l b}, HEq (f a (a' :: l) (f a' l b)) (f a' (a :: l) (f a l b))) :
@@ -461,17 +435,15 @@ theorem Perm.nodup {l l' : List α} (hl : l ~ l') (hR : l.Nodup) : l'.Nodup := h
 theorem Perm.nodup_iff {l₁ l₂ : List α} : l₁ ~ l₂ → (Nodup l₁ ↔ Nodup l₂) :=
  Perm.pairwise_iff <| @Ne.symm α

-theorem Perm.flatten {l₁ l₂ : List (List α)} (h : l₁ ~ l₂) : l₁.flatten ~ l₂.flatten := by
+theorem Perm.join {l₁ l₂ : List (List α)} (h : l₁ ~ l₂) : l₁.join ~ l₂.join := by
  induction h with
  | nil => rfl
-  | cons _ _ ih => simp only [flatten_cons, perm_append_left_iff, ih]
-  | swap => simp only [flatten_cons, ← append_assoc, perm_append_right_iff]; exact perm_append_comm ..
+  | cons _ _ ih => simp only [join_cons, perm_append_left_iff, ih]
+  | swap => simp only [join_cons, ← append_assoc, perm_append_right_iff]; exact perm_append_comm ..
  | trans _ _ ih₁ ih₂ => exact trans ih₁ ih₂

-@[deprecated Perm.flatten (since := "2024-10-14")] abbrev Perm.join := @Perm.flatten
-
 theorem Perm.bind_right {l₁ l₂ : List α} (f : α → List β) (p : l₁ ~ l₂) : l₁.bind f ~ l₂.bind f :=
-  (p.map _).flatten
+  (p.map _).join

 theorem Perm.eraseP (f : α → Bool) {l₁ l₂ : List α}
    (H : Pairwise (fun a b => f a → f b → False) l₁) (p : l₁ ~ l₂) : eraseP f l₁ ~ eraseP f l₂ := by
--- a/src/Init/Data/List/Range.lean
+++ b/src/Init/Data/List/Range.lean
@@ -20,6 +20,7 @@ open Nat

 /-! ## Ranges and enumeration -/

+
 /-! ### range' -/

 theorem range'_succ (s n step) : range' s (n + 1) step = s :: range' (s + step) n step := by
@@ -91,7 +92,7 @@ theorem map_add_range' (a) : ∀ s n step, map (a + ·) (range' s n step) = rang

 theorem range'_append : ∀ s m n step : Nat,
    range' s m step ++ range' (s + step * m) n step = range' s (n + m) step
-  | _, 0, _, _ => rfl
+  | s, 0, n, step => rfl
  | s, m + 1, n, step => by
    simpa [range', Nat.mul_succ, Nat.add_assoc, Nat.add_comm]
      using range'_append (s + step) m n step
@@ -130,7 +131,7 @@ theorem range'_eq_cons_iff : range' s n = a :: xs ↔ s = a ∧ 0 < n ∧ xs = r
 /-! ### range -/

 theorem range_loop_range' : ∀ s n : Nat, range.loop s (range' s n) = range' 0 (n + s)
-  | 0, _ => rfl
+  | 0, n => rfl
  | s + 1, n => by rw [← Nat.add_assoc, Nat.add_right_comm n s 1]; exact range_loop_range' s (n + 1)

 theorem range_eq_range' (n : Nat) : range n = range' 0 n :=
@@ -213,9 +214,9 @@ theorem enumFrom_eq_nil {n : Nat} {l : List α} : List.enumFrom n l = [] ↔ l =
@[simp]
 theorem getElem?_enumFrom :
    ∀ n (l : List α) m, (enumFrom n l)[m]? = l[m]?.map fun a => (n + m, a)
-  | _, [], _ => rfl
-  | _, _ :: _, 0 => by simp
-  | n, _ :: l, m + 1 => by
+  | n, [], m => rfl
+  | n, a :: l, 0 => by simp
+  | n, a :: l, m + 1 => by
    simp only [enumFrom_cons, getElem?_cons_succ]
    exact (getElem?_enumFrom (n + 1) l m).trans <| by rw [Nat.add_right_comm]; rfl

--- a/src/Init/Data/List/Sort/Impl.lean
+++ b/src/Init/Data/List/Sort/Impl.lean
@@ -102,7 +102,7 @@ def mergeSortTR (l : List α) (le : α → α → Bool := by exact fun a b => a
 where run : {n : Nat} → { l : List α // l.length = n } → List α
  | 0, ⟨[], _⟩ => []
  | 1, ⟨[a], _⟩ => [a]
-  | _+2, xs =>
+  | n+2, xs =>
    let (l, r) := splitInTwo xs
    mergeTR (run l) (run r) le

@@ -136,13 +136,13 @@ where
  run : {n : Nat} → { l : List α // l.length = n } → List α
  | 0, ⟨[], _⟩ => []
  | 1, ⟨[a], _⟩ => [a]
-  | _+2, xs =>
+  | n+2, xs =>
    let (l, r) := splitRevInTwo xs
    mergeTR (run' l) (run r) le
  run' : {n : Nat} → { l : List α // l.length = n } → List α
  | 0, ⟨[], _⟩ => []
  | 1, ⟨[a], _⟩ => [a]
-  | _+2, xs =>
+  | n+2, xs =>
    let (l, r) := splitRevInTwo' xs
    mergeTR (run' r) (run l) le

--- a/src/Init/Data/List/Sublist.lean
+++ b/src/Init/Data/List/Sublist.lean
@@ -483,30 +483,30 @@ theorem sublist_replicate_iff : l <+ replicate m a ↔ ∃ n, n ≤ m ∧ l = re
      rw [w]
      exact (replicate_sublist_replicate a).2 le

-theorem sublist_flatten_of_mem {L : List (List α)} {l} (h : l ∈ L) : l <+ L.flatten := by
+theorem sublist_join_of_mem {L : List (List α)} {l} (h : l ∈ L) : l <+ L.join := by
  induction L with
  | nil => cases h
  | cons l' L ih =>
    rcases mem_cons.1 h with (rfl | h)
    · simp [h]
-    · simp [ih h, flatten_cons, sublist_append_of_sublist_right]
+    · simp [ih h, join_cons, sublist_append_of_sublist_right]

-theorem sublist_flatten_iff {L : List (List α)} {l} :
-    l <+ L.flatten ↔
-      ∃ L' : List (List α), l = L'.flatten ∧ ∀ i (_ : i < L'.length), L'[i] <+ L[i]?.getD [] := by
+theorem sublist_join_iff {L : List (List α)} {l} :
+    l <+ L.join ↔
+      ∃ L' : List (List α), l = L'.join ∧ ∀ i (_ : i < L'.length), L'[i] <+ L[i]?.getD [] := by
  induction L generalizing l with
  | nil =>
    constructor
    · intro w
-      simp only [flatten_nil, sublist_nil] at w
+      simp only [join_nil, sublist_nil] at w
      subst w
      exact ⟨[], by simp, fun i x => by cases x⟩
    · rintro ⟨L', rfl, h⟩
-      simp only [flatten_nil, sublist_nil, flatten_eq_nil_iff]
+      simp only [join_nil, sublist_nil, join_eq_nil_iff]
      simp only [getElem?_nil, Option.getD_none, sublist_nil] at h
      exact (forall_getElem (p := (· = []))).1 h
  | cons l' L ih =>
-    simp only [flatten_cons, sublist_append_iff, ih]
+    simp only [join_cons, sublist_append_iff, ih]
    constructor
    · rintro ⟨l₁, l₂, rfl, s, L', rfl, h⟩
      refine ⟨l₁ :: L', by simp, ?_⟩
@@ -517,21 +517,21 @@ theorem sublist_flatten_iff {L : List (List α)} {l} :
      | nil =>
        exact ⟨[], [], by simp, by simp, [], by simp, fun i x => by cases x⟩
      | cons l₁ L' =>
-        exact ⟨l₁, L'.flatten, by simp, by simpa using h 0 (by simp), L', rfl,
+        exact ⟨l₁, L'.join, by simp, by simpa using h 0 (by simp), L', rfl,
          fun i lt => by simpa using h (i+1) (Nat.add_lt_add_right lt 1)⟩

-theorem flatten_sublist_iff {L : List (List α)} {l} :
-    L.flatten <+ l ↔
-      ∃ L' : List (List α), l = L'.flatten ∧ ∀ i (_ : i < L.length), L[i] <+ L'[i]?.getD [] := by
+theorem join_sublist_iff {L : List (List α)} {l} :
+    L.join <+ l ↔
+      ∃ L' : List (List α), l = L'.join ∧ ∀ i (_ : i < L.length), L[i] <+ L'[i]?.getD [] := by
  induction L generalizing l with
  | nil =>
    constructor
    · intro _
      exact ⟨[l], by simp, fun i x => by cases x⟩
    · rintro ⟨L', rfl, _⟩
-      simp only [flatten_nil, nil_sublist]
+      simp only [join_nil, nil_sublist]
  | cons l' L ih =>
-    simp only [flatten_cons, append_sublist_iff, ih]
+    simp only [join_cons, append_sublist_iff, ih]
    constructor
    · rintro ⟨l₁, l₂, rfl, s, L', rfl, h⟩
      refine ⟨l₁ :: L', by simp, ?_⟩
@@ -543,7 +543,7 @@ theorem flatten_sublist_iff {L : List (List α)} {l} :
        exact ⟨[], [], by simp, by simpa using h 0 (by simp), [], by simp,
          fun i x => by simpa using h (i+1) (Nat.add_lt_add_right x 1)⟩
      | cons l₁ L' =>
-        exact ⟨l₁, L'.flatten, by simp, by simpa using h 0 (by simp), L', rfl,
+        exact ⟨l₁, L'.join, by simp, by simpa using h 0 (by simp), L', rfl,
          fun i lt => by simpa using h (i+1) (Nat.add_lt_add_right lt 1)⟩

@[simp] theorem isSublist_iff_sublist [BEq α] [LawfulBEq α] {l₁ l₂ : List α} :
@@ -725,25 +725,16 @@ theorem infix_iff_suffix_prefix {l₁ l₂ : List α} : l₁ <:+: l₂ ↔ ∃ t
 theorem IsInfix.eq_of_length (h : l₁ <:+: l₂) : l₁.length = l₂.length → l₁ = l₂ :=
  h.sublist.eq_of_length

-theorem IsInfix.eq_of_length_le (h : l₁ <:+: l₂) : l₂.length ≤ l₁.length → l₁ = l₂ :=
-  h.sublist.eq_of_length_le
-
 theorem IsPrefix.eq_of_length (h : l₁ <+: l₂) : l₁.length = l₂.length → l₁ = l₂ :=
  h.sublist.eq_of_length

-theorem IsPrefix.eq_of_length_le (h : l₁ <+: l₂) : l₂.length ≤ l₁.length → l₁ = l₂ :=
-  h.sublist.eq_of_length_le
-
 theorem IsSuffix.eq_of_length (h : l₁ <:+ l₂) : l₁.length = l₂.length → l₁ = l₂ :=
  h.sublist.eq_of_length

-theorem IsSuffix.eq_of_length_le (h : l₁ <:+ l₂) : l₂.length ≤ l₁.length → l₁ = l₂ :=
-  h.sublist.eq_of_length_le
-
 theorem prefix_of_prefix_length_le :
    ∀ {l₁ l₂ l₃ : List α}, l₁ <+: l₃ → l₂ <+: l₃ → length l₁ ≤ length l₂ → l₁ <+: l₂
-  | [], _, _, _, _, _ => nil_prefix
-  | _ :: _, b :: _, _, ⟨_, rfl⟩, ⟨_, e⟩, ll => by
+  | [], l₂, _, _, _, _ => nil_prefix
+  | a :: l₁, b :: l₂, _, ⟨r₁, rfl⟩, ⟨r₂, e⟩, ll => by
    injection e with _ e'; subst b
    rcases prefix_of_prefix_length_le ⟨_, rfl⟩ ⟨_, e'⟩ (le_of_succ_le_succ ll) with ⟨r₃, rfl⟩
    exact ⟨r₃, rfl⟩
@@ -838,24 +829,6 @@ theorem isPrefix_iff : l₁ <+: l₂ ↔ ∀ i (h : i < l₁.length), l₂[i]? =
      rw (config := {occs := .pos [2]}) [← Nat.and_forall_add_one]
      simp [Nat.succ_lt_succ_iff, eq_comm]

-theorem isPrefix_iff_getElem {l₁ l₂ : List α} :
-    l₁ <+: l₂ ↔ ∃ (h : l₁.length ≤ l₂.length), ∀ x (hx : x < l₁.length),
-      l₁[x] = l₂[x]'(Nat.lt_of_lt_of_le hx h) where
-  mp h := ⟨h.length_le, fun _ _ ↦ h.getElem _⟩
-  mpr h := by
-    obtain ⟨hl, h⟩ := h
-    induction l₂ generalizing l₁ with
-    | nil =>
-      simpa using hl
-    | cons _ _ tail_ih =>
-      cases l₁ with
-      | nil =>
-        exact nil_prefix
-      | cons _ _ =>
-        simp only [length_cons, Nat.add_le_add_iff_right, Fin.getElem_fin] at hl h
-        simp only [cons_prefix_cons]
-        exact ⟨h 0 (zero_lt_succ _), tail_ih hl fun a ha ↦ h a.succ (succ_lt_succ ha)⟩
-
 -- See `Init.Data.List.Nat.Sublist` for `isSuffix_iff` and `ifInfix_iff`.

 theorem isPrefix_filterMap_iff {β} {f : α → Option β} {l₁ : List α} {l₂ : List β} :
@@ -938,14 +911,14 @@ theorem isInfix_replicate_iff {n} {a : α} {l : List α} :
    · simpa using Nat.sub_add_cancel h
    · simpa using w

-theorem infix_of_mem_flatten : ∀ {L : List (List α)}, l ∈ L → l <:+: flatten L
+theorem infix_of_mem_join : ∀ {L : List (List α)}, l ∈ L → l <:+: join L
  | l' :: _, h =>
    match h with
    | List.Mem.head .. => infix_append [] _ _
    | List.Mem.tail _ hlMemL =>
-      IsInfix.trans (infix_of_mem_flatten hlMemL) <| (suffix_append _ _).isInfix
+      IsInfix.trans (infix_of_mem_join hlMemL) <| (suffix_append _ _).isInfix

-@[simp] theorem prefix_append_right_inj (l) : l ++ l₁ <+: l ++ l₂ ↔ l₁ <+: l₂ :=
+theorem prefix_append_right_inj (l) : l ++ l₁ <+: l ++ l₂ ↔ l₁ <+: l₂ :=
  exists_congr fun r => by rw [append_assoc, append_right_inj]

 theorem prefix_cons_inj (a) : a :: l₁ <+: a :: l₂ ↔ l₁ <+: l₂ :=
@@ -976,7 +949,7 @@ theorem mem_of_mem_drop {n} {l : List α} (h : a ∈ l.drop n) : a ∈ l :=
  drop_subset _ _ h

 theorem drop_suffix_drop_left (l : List α) {m n : Nat} (h : m ≤ n) : drop n l <:+ drop m l := by
-  rw [← Nat.sub_add_cancel h, Nat.add_comm, ← drop_drop]
+  rw [← Nat.sub_add_cancel h, ← drop_drop]
  apply drop_suffix

 -- See `Init.Data.List.Nat.TakeDrop` for `take_prefix_take_left`.
@@ -1087,11 +1060,4 @@ theorem prefix_iff_eq_take : l₁ <+: l₂ ↔ l₁ = take (length l₁) l₂ :=

 -- See `Init.Data.List.Nat.Sublist` for `suffix_iff_eq_append`, `prefix_take_iff`, and `suffix_iff_eq_drop`.

-/-! ### Deprecations -/
-
-@[deprecated sublist_flatten_of_mem (since := "2024-10-14")] abbrev sublist_join_of_mem := @sublist_flatten_of_mem
-@[deprecated sublist_flatten_iff (since := "2024-10-14")] abbrev sublist_join_iff := @sublist_flatten_iff
-@[deprecated flatten_sublist_iff (since := "2024-10-14")] abbrev flatten_join_iff := @flatten_sublist_iff
-@[deprecated infix_of_mem_flatten (since := "2024-10-14")] abbrev infix_of_mem_join := @infix_of_mem_flatten
-
 end List
--- a/src/Init/Data/List/TakeDrop.lean
+++ b/src/Init/Data/List/TakeDrop.lean
@@ -97,14 +97,14 @@ theorem get?_take {l : List α} {n m : Nat} (h : m < n) : (l.take n).get? m = l.

 theorem getElem?_take_of_succ {l : List α} {n : Nat} : (l.take (n + 1))[n]? = l[n]? := by simp

-@[simp] theorem drop_drop (n : Nat) : ∀ (m) (l : List α), drop n (drop m l) = drop (m + n) l
+@[simp] theorem drop_drop (n : Nat) : ∀ (m) (l : List α), drop n (drop m l) = drop (n + m) l
  | m, [] => by simp
  | 0, l => by simp
  | m + 1, a :: l =>
    calc
      drop n (drop (m + 1) (a :: l)) = drop n (drop m l) := rfl
-      _ = drop (m + n) l := drop_drop n m l
-      _ = drop ((m + 1) + n) (a :: l) := by rw [Nat.add_right_comm]; rfl
+      _ = drop (n + m) l := drop_drop n m l
+      _ = drop (n + (m + 1)) (a :: l) := rfl

 theorem take_drop : ∀ (m n : Nat) (l : List α), take n (drop m l) = drop m (take (m + n) l)
  | 0, _, _ => by simp
@@ -112,7 +112,7 @@ theorem take_drop : ∀ (m n : Nat) (l : List α), take n (drop m l) = drop m (t
  | _+1, _, _ :: _ => by simpa [Nat.succ_add, take_succ_cons, drop_succ_cons] using take_drop ..

@[deprecated drop_drop (since := "2024-06-15")]
-theorem drop_add (m n) (l : List α) : drop (m + n) l = drop n (drop m l) := by
+theorem drop_add (m n) (l : List α) : drop (m + n) l = drop m (drop n l) := by
  simp [drop_drop]

@[simp]
@@ -126,7 +126,7 @@ theorem tail_drop (l : List α) (n : Nat) : (l.drop n).tail = l.drop (n + 1) :=

@[simp]
 theorem drop_tail (l : List α) (n : Nat) : l.tail.drop n = l.drop (n + 1) := by
-  rw [Nat.add_comm, ← drop_drop, drop_one]
+  rw [← drop_drop, drop_one]

@[simp]
 theorem drop_eq_nil_iff {l : List α} {k : Nat} : l.drop k = [] ↔ l.length ≤ k := by
--- a/src/Init/Data/List/ToArray.lean
+++ b/src/Init/Data/List/ToArray.lean
@@ -1,23 +0,0 @@
-/-
-Copyright (c) 2024 Lean FRO. All rights reserved.
-Released under Apache 2.0 license as described in the file LICENSE.
-Authors: Henrik Böving
-/
-prelude
-import Init.Data.List.Basic
-
-/--
-Auxiliary definition for `List.toArray`.
-`List.toArrayAux as r = r ++ as.toArray`
-/
-@[inline_if_reduce]
-def List.toArrayAux : List α → Array α → Array α
-  | nil,       r => r
-  | cons a as, r => toArrayAux as (r.push a)
-
-/-- Convert a `List α` into an `Array α`. This is O(n) in the length of the list.  -/
-- This function is exported to C, where it is called by `Array.mk`
-- (the constructor) to implement this functionality.
-@[inline, match_pattern, pp_nodot, export lean_list_to_array]
-def List.toArrayImpl (as : List α) : Array α :=
-  as.toArrayAux (Array.mkEmpty as.length)
--- a/src/Init/Data/List/Zip.lean
+++ b/src/Init/Data/List/Zip.lean
@@ -5,7 +5,6 @@ Authors: Parikshit Khanna, Jeremy Avigad, Leonardo de Moura, Floris van Doorn, M
 -/
 prelude
 import Init.Data.List.TakeDrop
-import Init.Data.Function

 /-!
 # Lemmas about `List.zip`, `List.zipWith`, `List.zipWithAll`, and `List.unzip`.
@@ -239,14 +238,6 @@ theorem zipWith_eq_append_iff {f : α → β → γ} {l₁ : List α} {l₂ : Li
  | zero => rfl
  | succ n ih => simp [replicate_succ, ih]

-theorem map_uncurry_zip_eq_zipWith (f : α → β → γ) (l : List α) (l' : List β) :
-    map (Function.uncurry f) (l.zip l') = zipWith f l l' := by
-  rw [zip]
-  induction l generalizing l' with
-  | nil => simp
-  | cons hl tl ih =>
-    cases l' <;> simp [ih]
-
 /-! ### zip -/

 theorem zip_eq_zipWith : ∀ (l₁ : List α) (l₂ : List β), zip l₁ l₂ = zipWith Prod.mk l₁ l₂
@@ -256,9 +247,9 @@ theorem zip_eq_zipWith : ∀ (l₁ : List α) (l₂ : List β), zip l₁ l₂ =

 theorem zip_map (f : α → γ) (g : β → δ) :
    ∀ (l₁ : List α) (l₂ : List β), zip (l₁.map f) (l₂.map g) = (zip l₁ l₂).map (Prod.map f g)
-  | [], _ => rfl
-  | _, [] => by simp only [map, zip_nil_right]
-  | _ :: _, _ :: _ => by
+  | [], l₂ => rfl
+  | l₁, [] => by simp only [map, zip_nil_right]
+  | a :: l₁, b :: l₂ => by
    simp only [map, zip_cons_cons, zip_map, Prod.map]; constructor

 theorem zip_map_left (f : α → γ) (l₁ : List α) (l₂ : List β) :
@@ -296,12 +287,12 @@ theorem of_mem_zip {a b} : ∀ {l₁ : List α} {l₂ : List β}, (a, b) ∈ zip

 theorem map_fst_zip :
    ∀ (l₁ : List α) (l₂ : List β), l₁.length ≤ l₂.length → map Prod.fst (zip l₁ l₂) = l₁
-  | [], _, _ => rfl
+  | [], bs, _ => rfl
  | _ :: as, _ :: bs, h => by
    simp [Nat.succ_le_succ_iff] at h
    show _ :: map Prod.fst (zip as bs) = _ :: as
    rw [map_fst_zip as bs h]
-  | _ :: _, [], h => by simp at h
+  | a :: as, [], h => by simp at h

 theorem map_snd_zip :
    ∀ (l₁ : List α) (l₂ : List β), l₂.length ≤ l₁.length → map Prod.snd (zip l₁ l₂) = l₂
@@ -439,9 +430,9 @@ theorem zip_unzip : ∀ l : List (α × β), zip (unzip l).1 (unzip l).2 = l

 theorem unzip_zip_left :
    ∀ {l₁ : List α} {l₂ : List β}, length l₁ ≤ length l₂ → (unzip (zip l₁ l₂)).1 = l₁
-  | [], _, _ => rfl
-  | _, [], h => by rw [eq_nil_of_length_eq_zero (Nat.eq_zero_of_le_zero h)]; rfl
-  | _ :: _, _ :: _, h => by
+  | [], l₂, _ => rfl
+  | l₁, [], h => by rw [eq_nil_of_length_eq_zero (Nat.eq_zero_of_le_zero h)]; rfl
+  | a :: l₁, b :: l₂, h => by
    simp only [zip_cons_cons, unzip_cons, unzip_zip_left (le_of_succ_le_succ h)]

 theorem unzip_zip_right :
--- a/src/Init/Data/Nat/Basic.lean
+++ b/src/Init/Data/Nat/Basic.lean
@@ -248,7 +248,7 @@ protected theorem add_mul (n m k : Nat) : (n + m) * k = n * k + m * k :=
  Nat.right_distrib n m k

 protected theorem mul_assoc : ∀ (n m k : Nat), (n * m) * k = n * (m * k)
-  | _, _, 0      => rfl
+  | n, m, 0      => rfl
  | n, m, succ k => by simp [mul_succ, Nat.mul_assoc n m k, Nat.left_distrib]
 instance : Std.Associative (α := Nat) (· * ·) := ⟨Nat.mul_assoc⟩

@@ -634,8 +634,6 @@ theorem lt_succ_of_lt (h : a < b) : a < succ b := le_succ_of_le h

 theorem lt_add_one_of_lt (h : a < b) : a < b + 1 := le_succ_of_le h

-@[simp] theorem lt_one_iff : n < 1 ↔ n = 0 := Nat.lt_succ_iff.trans <| by rw [le_zero_eq]
-
 theorem succ_pred_eq_of_ne_zero : ∀ {n}, n ≠ 0 → succ (pred n) = n
  | _+1, _ => rfl

--- a/src/Init/Data/Nat/Div.lean
+++ b/src/Init/Data/Nat/Div.lean
@@ -269,7 +269,7 @@ protected theorem div_div_eq_div_mul (m n k : Nat) : m / n / k = m / (n * k) :=

 theorem div_mul_le_self : ∀ (m n : Nat), m / n * n ≤ m
  | m, 0   => by simp
-  | _, _+1 => (le_div_iff_mul_le (Nat.succ_pos _)).1 (Nat.le_refl _)
+  | m, n+1 => (le_div_iff_mul_le (Nat.succ_pos _)).1 (Nat.le_refl _)

 theorem div_lt_iff_lt_mul (Hk : 0 < k) : x / k < y ↔ x < y * k := by
  rw [← Nat.not_le, ← Nat.not_le]; exact not_congr (le_div_iff_mul_le Hk)
--- a/src/Init/Data/Nat/Lemmas.lean
+++ b/src/Init/Data/Nat/Lemmas.lean
@@ -605,9 +605,6 @@ theorem add_mod (a b n : Nat) : (a + b) % n = ((a % n) + (b % n)) % n := by
    | zero => simp_all
    | succ k => omega

-@[simp] theorem mod_mul_mod {a b c : Nat} : (a % c * b) % c = a * b % c := by
-  rw [mul_mod, mod_mod, ← mul_mod]
-
 /-! ### pow -/

 theorem pow_succ' {m n : Nat} : m ^ n.succ = m * m ^ n := by
@@ -770,16 +767,6 @@ protected theorem two_pow_pred_mod_two_pow (h : 0 < w) :
  rw [mod_eq_of_lt]
  apply Nat.pow_pred_lt_pow (by omega) h

-protected theorem pow_lt_pow_iff_pow_mul_le_pow {a n m : Nat} (h : 1 < a) :
-    a ^ n < a ^ m ↔ a ^ n * a ≤ a ^ m := by
-  rw [←Nat.pow_add_one, Nat.pow_le_pow_iff_right (by omega), Nat.pow_lt_pow_iff_right (by omega)]
-  omega
-
-@[simp]
-theorem two_pow_pred_mul_two (h : 0 < w) :
-    2 ^ (w - 1) * 2 = 2 ^ w := by
-  simp [← Nat.pow_succ, Nat.sub_add_cancel h]
-
 /-! ### log2 -/

@[simp]
@@ -874,15 +861,15 @@ theorem shiftLeft_succ_inside (m n : Nat) : m <<< (n+1) = (2*m) <<< n := rfl

 /-- Shiftleft on successor with multiple moved to outside. -/
 theorem shiftLeft_succ : ∀(m n), m <<< (n + 1) = 2 * (m <<< n)
-| _, 0 => rfl
-| _, k + 1 => by
+| m, 0 => rfl
+| m, k + 1 => by
  rw [shiftLeft_succ_inside _ (k+1)]
  rw [shiftLeft_succ _ k, shiftLeft_succ_inside]

 /-- Shiftright on successor with division moved inside. -/
 theorem shiftRight_succ_inside : ∀m n, m >>> (n+1) = (m/2) >>> n
-| _, 0 => rfl
-| _, k + 1 => by
+| m, 0 => rfl
+| m, k + 1 => by
  rw [shiftRight_succ _ (k+1)]
  rw [shiftRight_succ_inside _ k, shiftRight_succ]

--- a/src/Init/Data/NeZero.lean
+++ b/src/Init/Data/NeZero.lean
@@ -35,4 +35,4 @@ theorem neZero_iff {n : R} : NeZero n ↔ n ≠ 0 :=
  ⟨fun h ↦ h.out, NeZero.mk⟩

@[simp] theorem neZero_zero_iff_false {α : Type _} [Zero α] : NeZero (0 : α) ↔ False :=
-  ⟨fun _ ↦ NeZero.ne (0 : α) rfl, fun h ↦ h.elim⟩
+  ⟨fun h ↦ h.ne rfl, fun h ↦ h.elim⟩
--- a/src/Init/Data/Option.lean
+++ b/src/Init/Data/Option.lean
@@ -8,5 +8,3 @@ import Init.Data.Option.Basic
 import Init.Data.Option.BasicAux
 import Init.Data.Option.Instances
 import Init.Data.Option.Lemmas
-import Init.Data.Option.Attach
-import Init.Data.Option.List
--- a/src/Init/Data/Option/Attach.lean
+++ b/src/Init/Data/Option/Attach.lean
@@ -1,242 +0,0 @@
-/-
-Copyright (c) 2024 Lean FRO. All rights reserved.
-Released under Apache 2.0 license as described in the file LICENSE.
-Authors: Kim Morrison
-/
-prelude
-import Init.Data.Option.Basic
-import Init.Data.Option.List
-import Init.Data.List.Attach
-import Init.BinderPredicates
-
-namespace Option
-
-/--
-Unsafe implementation of `attachWith`, taking advantage of the fact that the representation of
-`Option {x // P x}` is the same as the input `Option α`.
-/
-@[inline] private unsafe def attachWithImpl
-    (o : Option α) (P : α → Prop) (_ : ∀ x ∈ o, P x) : Option {x // P x} := unsafeCast o
-
-/-- "Attach" a proof `P x` that holds for the element of `o`, if present,
-to produce a new option with the same element but in the type `{x // P x}`. -/
-@[implemented_by attachWithImpl] def attachWith
-    (xs : Option α) (P : α → Prop) (H : ∀ x ∈ xs, P x) : Option {x // P x} :=
-  match xs with
-  | none => none
-  | some x => some ⟨x, H x (mem_some_self x)⟩
-
-/-- "Attach" the proof that the element of `xs`, if present, is in `xs`
-to produce a new option with the same elements but in the type `{x // x ∈ xs}`. -/
-@[inline] def attach (xs : Option α) : Option {x // x ∈ xs} := xs.attachWith _ fun _ => id
-
-@[simp] theorem attach_none : (none : Option α).attach = none := rfl
-@[simp] theorem attachWith_none : (none : Option α).attachWith P H = none := rfl
-
-@[simp] theorem attach_some {x : α} :
-    (some x).attach = some ⟨x, rfl⟩ := rfl
-@[simp] theorem attachWith_some {x : α} {P : α → Prop} (h : ∀ (b : α), b ∈ some x → P b) :
-    (some x).attachWith P h = some ⟨x, by simpa using h⟩ := rfl
-
-theorem attach_congr {o₁ o₂ : Option α} (h : o₁ = o₂) :
-    o₁.attach = o₂.attach.map (fun x => ⟨x.1, h ▸ x.2⟩) := by
-  subst h
-  simp
-
-theorem attachWith_congr {o₁ o₂ : Option α} (w : o₁ = o₂) {P : α → Prop} {H : ∀ x ∈ o₁, P x} :
-    o₁.attachWith P H = o₂.attachWith P fun x h => H _ (w ▸ h) := by
-  subst w
-  simp
-
-theorem attach_map_coe (o : Option α) (f : α → β) :
-    (o.attach.map fun (i : {i // i ∈ o}) => f i) = o.map f := by
-  cases o <;> simp
-
-theorem attach_map_val (o : Option α) (f : α → β) :
-    (o.attach.map fun i => f i.val) = o.map f :=
-  attach_map_coe _ _
-
-@[simp]
-theorem attach_map_subtype_val (o : Option α) :
-    o.attach.map Subtype.val = o :=
-  (attach_map_coe _ _).trans (congrFun Option.map_id _)
-
-theorem attachWith_map_coe {p : α → Prop} (f : α → β) (o : Option α) (H : ∀ a ∈ o, p a) :
-    ((o.attachWith p H).map fun (i : { i // p i}) => f i.val) = o.map f := by
-  cases o <;> simp [H]
-
-theorem attachWith_map_val {p : α → Prop} (f : α → β) (o : Option α) (H : ∀ a ∈ o, p a) :
-    ((o.attachWith p H).map fun i => f i.val) = o.map f :=
-  attachWith_map_coe _ _ _
-
-@[simp]
-theorem attachWith_map_subtype_val {p : α → Prop} (o : Option α) (H : ∀ a ∈ o, p a) :
-    (o.attachWith p H).map Subtype.val = o :=
-  (attachWith_map_coe _ _ _).trans (congrFun Option.map_id _)
-
-@[simp] theorem mem_attach : ∀ (o : Option α) (x : {x // x ∈ o}), x ∈ o.attach
-  | none, ⟨x, h⟩ => by simp at h
-  | some a, ⟨x, h⟩ => by simpa using h
-
-@[simp] theorem isNone_attach (o : Option α) : o.attach.isNone = o.isNone := by
-  cases o <;> simp
-
-@[simp] theorem isNone_attachWith {p : α → Prop} (o : Option α) (H : ∀ a ∈ o, p a) :
-    (o.attachWith p H).isNone = o.isNone := by
-  cases o <;> simp
-
-@[simp] theorem isSome_attach (o : Option α) : o.attach.isSome = o.isSome := by
-  cases o <;> simp
-
-@[simp] theorem isSome_attachWith {p : α → Prop} (o : Option α) (H : ∀ a ∈ o, p a) :
-    (o.attachWith p H).isSome = o.isSome := by
-  cases o <;> simp
-
-@[simp] theorem attach_eq_none_iff (o : Option α) : o.attach = none ↔ o = none := by
-  cases o <;> simp
-
-@[simp] theorem attach_eq_some_iff {o : Option α} {x : {x // x ∈ o}} :
-    o.attach = some x ↔ o = some x.val := by
-  cases o <;> cases x <;> simp
-
-@[simp] theorem attachWith_eq_none_iff {p : α → Prop} (o : Option α) (H : ∀ a ∈ o, p a) :
-    o.attachWith p H = none ↔ o = none := by
-  cases o <;> simp
-
-@[simp] theorem attachWith_eq_some_iff {p : α → Prop} {o : Option α} (H : ∀ a ∈ o, p a) {x : {x // p x}} :
-    o.attachWith p H = some x ↔ o = some x.val := by
-  cases o <;> cases x <;> simp
-
-@[simp] theorem get_attach {o : Option α} (h : o.attach.isSome = true) :
-    o.attach.get h = ⟨o.get (by simpa using h), by simp⟩ := by
-  cases o
-  · simp at h
-  · simp [get_some]
-
-@[simp] theorem get_attachWith {p : α → Prop} {o : Option α} (H : ∀ a ∈ o, p a) (h : (o.attachWith p H).isSome) :
-    (o.attachWith p H).get h = ⟨o.get (by simpa using h), H _ (by simp)⟩ := by
-  cases o
-  · simp at h
-  · simp [get_some]
-
-@[simp] theorem toList_attach (o : Option α) :
-    o.attach.toList = o.toList.attach.map fun ⟨x, h⟩ => ⟨x, by simpa using h⟩ := by
-  cases o <;> simp
-
-theorem attach_map {o : Option α} (f : α → β) :
-    (o.map f).attach = o.attach.map (fun ⟨x, h⟩ => ⟨f x, mem_map_of_mem f h⟩) := by
-  cases o <;> simp
-
-theorem attachWith_map {o : Option α} (f : α → β) {P : β → Prop} {H : ∀ (b : β), b ∈ o.map f → P b} :
-    (o.map f).attachWith P H = (o.attachWith (P ∘ f) (fun a h => H _ (mem_map_of_mem f h))).map
-      fun ⟨x, h⟩ => ⟨f x, h⟩ := by
-  cases o <;> simp
-
-theorem map_attach {o : Option α} (f : { x // x ∈ o } → β) :
-    o.attach.map f = o.pmap (fun a (h : a ∈ o) => f ⟨a, h⟩) (fun a h => h) := by
-  cases o <;> simp
-
-theorem map_attachWith {o : Option α} {P : α → Prop} {H : ∀ (a : α), a ∈ o → P a}
-    (f : { x // P x } → β) :
-    (o.attachWith P H).map f =
-      o.pmap (fun a (h : a ∈ o ∧ P a) => f ⟨a, h.2⟩) (fun a h => ⟨h, H a h⟩) := by
-  cases o <;> simp
-
-theorem attach_bind {o : Option α} {f : α → Option β} :
-    (o.bind f).attach =
-      o.attach.bind fun ⟨x, h⟩ => (f x).attach.map fun ⟨y, h'⟩ => ⟨y, mem_bind_iff.mpr ⟨x, h, h'⟩⟩ := by
-  cases o <;> simp
-
-theorem bind_attach {o : Option α} {f : {x // x ∈ o} → Option β} :
-    o.attach.bind f = o.pbind fun a h => f ⟨a, h⟩ := by
-  cases o <;> simp
-
-theorem pbind_eq_bind_attach {o : Option α} {f : (a : α) → a ∈ o → Option β} :
-    o.pbind f = o.attach.bind fun ⟨x, h⟩ => f x h := by
-  cases o <;> simp
-
-theorem attach_filter {o : Option α} {p : α → Bool} :
-    (o.filter p).attach =
-      o.attach.bind fun ⟨x, h⟩ => if h' : p x then some ⟨x, by simp_all⟩ else none := by
-  cases o with
-  | none => simp
-  | some a =>
-    simp only [filter_some, attach_some]
-    ext
-    simp only [mem_def, attach_eq_some_iff, ite_none_right_eq_some, some.injEq, some_bind,
-      dite_none_right_eq_some]
-    constructor
-    · rintro ⟨h, w⟩
-      refine ⟨h, by ext; simpa using w⟩
-    · rintro ⟨h, rfl⟩
-      simp [h]
-
-theorem filter_attach {o : Option α} {p : {x // x ∈ o} → Bool} :
-    o.attach.filter p = o.pbind fun a h => if p ⟨a, h⟩ then some ⟨a, h⟩ else none := by
-  cases o <;> simp [filter_some]
-
-/-! ## unattach
-
-`Option.unattach` is the (one-sided) inverse of `Option.attach`. It is a synonym for `Option.map Subtype.val`.
-
-We use it by providing a simp lemma `l.attach.unattach = l`, and simp lemmas which recognize higher order
-functions applied to `l : Option { x // p x }` which only depend on the value, not the predicate, and rewrite these
-in terms of a simpler function applied to `l.unattach`.
-
-Further, we provide simp lemmas that push `unattach` inwards.
-/
-
-/--
-A synonym for `l.map (·.val)`. Mostly this should not be needed by users.
-It is introduced as an intermediate step by lemmas such as `map_subtype`,
-and is ideally subsequently simplified away by `unattach_attach`.
-
-If not, usually the right approach is `simp [Option.unattach, -Option.map_subtype]` to unfold.
-/
-def unattach {α : Type _} {p : α → Prop} (o : Option { x // p x }) := o.map (·.val)
-
-@[simp] theorem unattach_none {p : α → Prop} : (none : Option { x // p x }).unattach = none := rfl
-@[simp] theorem unattach_some {p : α → Prop} {a : { x // p x }} :
-  (some a).unattach = a.val := rfl
-
-@[simp] theorem isSome_unattach {p : α → Prop} {o : Option { x // p x }} :
-    o.unattach.isSome = o.isSome := by
-  simp [unattach]
-
-@[simp] theorem isNone_unattach {p : α → Prop} {o : Option { x // p x }} :
-    o.unattach.isNone = o.isNone := by
-  simp [unattach]
-
-@[simp] theorem unattach_attach (o : Option α) : o.attach.unattach = o := by
-  cases o <;> simp
-
-@[simp] theorem unattach_attachWith {p : α → Prop} {o : Option α}
-    {H : ∀ a ∈ o, p a} :
-    (o.attachWith p H).unattach = o := by
-  cases o <;> simp
-
-/-! ### Recognizing higher order functions on subtypes using a function that only depends on the value. -/
-
-/--
-This lemma identifies maps over lists of subtypes, where the function only depends on the value, not the proposition,
-and simplifies these to the function directly taking the value.
-/
-@[simp] theorem map_subtype {p : α → Prop} {o : Option { x // p x }}
-    {f : { x // p x } → β} {g : α → β} {hf : ∀ x h, f ⟨x, h⟩ = g x} :
-    o.map f = o.unattach.map g := by
-  cases o <;> simp [hf]
-
-@[simp] theorem bind_subtype {p : α → Prop} {o : Option { x // p x }}
-    {f : { x // p x } → Option β} {g : α → Option β} {hf : ∀ x h, f ⟨x, h⟩ = g x} :
-    (o.bind f) = o.unattach.bind g := by
-  cases o <;> simp [hf]
-
-@[simp] theorem unattach_filter {p : α → Prop} {o : Option { x // p x }}
-    {f : { x // p x } → Bool} {g : α → Bool} {hf : ∀ x h, f ⟨x, h⟩ = g x} :
-    (o.filter f).unattach = o.unattach.filter g := by
-  cases o
-  · simp
-  · simp only [filter_some, hf, unattach_some]
-    split <;> simp
-
-end Option
--- a/src/Init/Data/Option/Basic.lean
+++ b/src/Init/Data/Option/Basic.lean
@@ -202,7 +202,7 @@ result.
 instance (α) [BEq α] [LawfulBEq α] : LawfulBEq (Option α) where
  rfl {x} :=
    match x with
-    | some _ => LawfulBEq.rfl (α := α)
+    | some x => LawfulBEq.rfl (α := α)
    | none => rfl
  eq_of_beq {x y h} := by
    match x, y with
--- a/src/Init/Data/Option/Lemmas.lean
+++ b/src/Init/Data/Option/Lemmas.lean
@@ -79,7 +79,7 @@ theorem eq_none_iff_forall_not_mem : o = none ↔ ∀ a, a ∉ o :=

 theorem isSome_iff_exists : isSome x ↔ ∃ a, x = some a := by cases x <;> simp [isSome]

-theorem isSome_eq_isSome : (isSome x = isSome y) ↔ (x = none ↔ y = none) := by
+@[simp] theorem isSome_eq_isSome : (isSome x = isSome y) ↔ (x = none ↔ y = none) := by
  cases x <;> cases y <;> simp

@[simp] theorem isNone_none : @isNone α none = true := rfl
@@ -138,10 +138,6 @@ theorem bind_eq_none' {o : Option α} {f : α → Option β} :
    o.bind f = none ↔ ∀ b a, a ∈ o → b ∉ f a := by
  simp only [eq_none_iff_forall_not_mem, not_exists, not_and, mem_def, bind_eq_some]

-theorem mem_bind_iff {o : Option α} {f : α → Option β} :
-    b ∈ o.bind f ↔ ∃ a, a ∈ o ∧ b ∈ f a := by
-  cases o <;> simp
-
 theorem bind_comm {f : α → β → Option γ} (a : Option α) (b : Option β) :
    (a.bind fun x => b.bind (f x)) = b.bind fun y => a.bind fun x => f x y := by
  cases a <;> cases b <;> rfl
@@ -236,27 +232,9 @@ theorem isSome_filter_of_isSome (p : α → Bool) (o : Option α) (h : (o.filter
  cases o <;> simp at h ⊢

@[simp] theorem filter_eq_none {p : α → Bool} :
-    o.filter p = none ↔ o = none ∨ ∀ a, a ∈ o → ¬ p a := by
+    Option.filter p o = none ↔ o = none ∨ ∀ a, a ∈ o → ¬ p a := by
  cases o <;> simp [filter_some]

-@[simp] theorem filter_eq_some {o : Option α} {p : α → Bool} :
-    o.filter p = some a ↔ a ∈ o ∧ p a := by
-  cases o with
-  | none => simp
-  | some a =>
-    simp [filter_some]
-    split <;> rename_i h
-    · simp only [some.injEq, iff_self_and]
-      rintro rfl
-      exact h
-    · simp only [reduceCtorEq, false_iff, not_and, Bool.not_eq_true]
-      rintro rfl
-      simpa using h
-
-theorem mem_filter_iff {p : α → Bool} {a : α} {o : Option α} :
-    a ∈ o.filter p ↔ a ∈ o ∧ p a := by
-  simp
-
@[simp] theorem all_guard (p : α → Prop) [DecidablePred p] (a : α) :
    Option.all q (guard p a) = (!p a || q a) := by
  simp only [guard]
@@ -330,8 +308,8 @@ theorem guard_comp {p : α → Prop} [DecidablePred p] {f : β → α} :
 theorem liftOrGet_eq_or_eq {f : α → α → α} (h : ∀ a b, f a b = a ∨ f a b = b) :
    ∀ o₁ o₂, liftOrGet f o₁ o₂ = o₁ ∨ liftOrGet f o₁ o₂ = o₂
  | none, none => .inl rfl
-  | some _, none => .inl rfl
-  | none, some _ => .inr rfl
+  | some a, none => .inl rfl
+  | none, some b => .inr rfl
  | some a, some b => by have := h a b; simp [liftOrGet] at this ⊢; exact this

@[simp] theorem liftOrGet_none_left {f} {b : Option α} : liftOrGet f none b = b := by
@@ -372,8 +350,6 @@ end choice

@[simp] theorem toList_none (α : Type _) : (none : Option α).toList = [] := rfl

-- See `Init.Data.Option.List` for lemmas about `toList`.
-
@[simp] theorem or_some : (some a).or o = some a := rfl
@[simp] theorem none_or : none.or o = o := rfl

--- a/src/Init/Data/Option/List.lean
+++ b/src/Init/Data/Option/List.lean
@@ -1,14 +0,0 @@
-/-
-Copyright (c) 2024 Lean FRO. All rights reserved.
-Released under Apache 2.0 license as described in the file LICENSE.
-Authors: Kim Morrison
-/
-prelude
-import Init.Data.List.Lemmas
-
-namespace Option
-
-@[simp] theorem mem_toList {a : α} {o : Option α} : a ∈ o.toList ↔ a ∈ o := by
-  cases o <;> simp [eq_comm]
-
-end Option
--- a/src/Init/Data/String/Basic.lean
+++ b/src/Init/Data/String/Basic.lean
@@ -317,15 +317,12 @@ theorem _root_.Char.utf8Size_le_four (c : Char) : c.utf8Size ≤ 4 := by

@[simp] theorem pos_add_char (p : Pos) (c : Char) : (p + c).byteIdx = p.byteIdx + c.utf8Size := rfl

-protected theorem Pos.ne_zero_of_lt : {a b : Pos} → a < b → b ≠ 0
-  | _, _, hlt, rfl => Nat.not_lt_zero _ hlt
-
 theorem lt_next (s : String) (i : Pos) : i.1 < (s.next i).1 :=
  Nat.add_lt_add_left (Char.utf8Size_pos _) _

 theorem utf8PrevAux_lt_of_pos : ∀ (cs : List Char) (i p : Pos), p ≠ 0 →
    (utf8PrevAux cs i p).1 < p.1
-  | [], _, _, h =>
+  | [], i, p, h =>
    Nat.lt_of_le_of_lt (Nat.zero_le _)
      (Nat.zero_lt_of_ne_zero (mt (congrArg Pos.mk) h))
  | c::cs, i, p, h => by
@@ -1024,66 +1021,6 @@ instance hasBeq : BEq Substring := ⟨beq⟩
 def sameAs (ss1 ss2 : Substring) : Bool :=
  ss1.startPos == ss2.startPos && ss1 == ss2

-/--
-Returns the longest common prefix of two substrings.
-The returned substring will use the same underlying string as `s`.
-/
-def commonPrefix (s t : Substring) : Substring :=
-  { s with stopPos := loop s.startPos t.startPos }
-where
-  /-- Returns the ending position of the common prefix, working up from `spos, tpos`. -/
-  loop spos tpos :=
-    if h : spos < s.stopPos ∧ tpos < t.stopPos then
-      if s.str.get spos == t.str.get tpos then
-        have := Nat.sub_lt_sub_left h.1 (s.str.lt_next spos)
-        loop (s.str.next spos) (t.str.next tpos)
-      else
-        spos
-    else
-      spos
-  termination_by s.stopPos.byteIdx - spos.byteIdx
-
-/--
-Returns the longest common suffix of two substrings.
-The returned substring will use the same underlying string as `s`.
-/
-def commonSuffix (s t : Substring) : Substring :=
-  { s with startPos := loop s.stopPos t.stopPos }
-where
-  /-- Returns the starting position of the common prefix, working down from `spos, tpos`. -/
-  loop spos tpos :=
-    if h : s.startPos < spos ∧ t.startPos < tpos then
-      let spos' := s.str.prev spos
-      let tpos' := t.str.prev tpos
-      if s.str.get spos' == t.str.get tpos' then
-        have : spos' < spos := s.str.prev_lt_of_pos spos (String.Pos.ne_zero_of_lt h.1)
-        loop spos' tpos'
-      else
-        spos
-    else
-      spos
-  termination_by spos.byteIdx
-
-/--
-If `pre` is a prefix of `s`, i.e. `s = pre ++ t`, returns the remainder `t`.
-/
-def dropPrefix? (s : Substring) (pre : Substring) : Option Substring :=
-  let t := s.commonPrefix pre
-  if t.bsize = pre.bsize then
-    some { s with startPos := t.stopPos }
-  else
-    none
-
-/--
-If `suff` is a suffix of `s`, i.e. `s = t ++ suff`, returns the remainder `t`.
-/
-def dropSuffix? (s : Substring) (suff : Substring) : Option Substring :=
-  let t := s.commonSuffix suff
-  if t.bsize = suff.bsize then
-    some { s with stopPos := t.startPos }
-  else
-    none
-
 end Substring

 namespace String
@@ -1145,28 +1082,6 @@ namespace String
@[inline] def decapitalize (s : String) :=
  s.set 0 <| s.get 0 |>.toLower

-/--
-If `pre` is a prefix of `s`, i.e. `s = pre ++ t`, returns the remainder `t`.
-/
-def dropPrefix? (s : String) (pre : Substring) : Option Substring :=
-  s.toSubstring.dropPrefix? pre
-
-/--
-If `suff` is a suffix of `s`, i.e. `s = t ++ suff`, returns the remainder `t`.
-/
-def dropSuffix? (s : String) (suff : Substring) : Option Substring :=
-  s.toSubstring.dropSuffix? suff
-
-/-- `s.stripPrefix pre` will remove `pre` from the beginning of `s` if it occurs there,
-or otherwise return `s`. -/
-def stripPrefix (s : String) (pre : Substring) : String :=
-  s.dropPrefix? pre |>.map Substring.toString |>.getD s
-
-/-- `s.stripSuffix suff` will remove `suff` from the end of `s` if it occurs there,
-or otherwise return `s`. -/
-def stripSuffix (s : String) (suff : Substring) : String :=
-  s.dropSuffix? suff |>.map Substring.toString |>.getD s
-
 end String

 namespace Char
--- a/src/Init/Data/String/Extra.lean
+++ b/src/Init/Data/String/Extra.lean
@@ -121,7 +121,7 @@ def toUTF8 (a : @& String) : ByteArray :=

@[simp] theorem size_toUTF8 (s : String) : s.toUTF8.size = s.utf8ByteSize := by
  simp [toUTF8, ByteArray.size, Array.size, utf8ByteSize, List.bind]
-  induction s.data <;> simp [List.map, List.flatten, utf8ByteSize.go, Nat.add_comm, *]
+  induction s.data <;> simp [List.map, List.join, utf8ByteSize.go, Nat.add_comm, *]

 /-- Accesses a byte in the UTF-8 encoding of the `String`. O(1) -/
@[extern "lean_string_get_byte_fast"]
--- a/src/Init/Notation.lean
+++ b/src/Init/Notation.lean
@@ -535,21 +535,24 @@ syntax (name := includeStr) "include_str " term : term

 /--
 The `run_cmd doSeq` command executes code in `CommandElabM Unit`.
-This is the same as `#eval show CommandElabM Unit from discard do doSeq`.
+This is almost the same as `#eval show CommandElabM Unit from do doSeq`,
+except that it doesn't print an empty diagnostic.
 -/
 syntax (name := runCmd) "run_cmd " doSeq : command

 /--
 The `run_elab doSeq` command executes code in `TermElabM Unit`.
-This is the same as `#eval show TermElabM Unit from discard do doSeq`.
+This is almost the same as `#eval show TermElabM Unit from do doSeq`,
+except that it doesn't print an empty diagnostic.
 -/
 syntax (name := runElab) "run_elab " doSeq : command

 /--
 The `run_meta doSeq` command executes code in `MetaM Unit`.
-This is the same as `#eval show MetaM Unit from do discard doSeq`.
+This is almost the same as `#eval show MetaM Unit from do doSeq`,
+except that it doesn't print an empty diagnostic.

-(This is effectively a synonym for `run_elab` since `MetaM` lifts to `TermElabM`.)
+(This is effectively a synonym for `run_elab`.)
 -/
 syntax (name := runMeta) "run_meta " doSeq : command

@@ -672,13 +675,6 @@ Message ordering:

 For example, `#guard_msgs (error, drop all) in cmd` means to check warnings and drop
 everything else.
-
-The command elaborator has special support for `#guard_msgs` for linting.
-The `#guard_msgs` itself wants to capture linter warnings,
-so it elaborates the command it is attached to as if it were a top-level command.
-However, the command elaborator runs linters for *all* top-level commands,
-which would include `#guard_msgs` itself, and would cause duplicate and/or uncaptured linter warnings.
-The top-level command elaborator only runs the linters if `#guard_msgs` is not present.
 -/
 syntax (name := guardMsgsCmd)
  (docComment)? "#guard_msgs" (ppSpace guardMsgsSpec)? " in" ppLine command : command
--- a/src/Init/NotationExtra.lean
+++ b/src/Init/NotationExtra.lean
@@ -223,6 +223,38 @@ end Lean
  | `($_ $array $index) => `($array[$index]?)
  | _ => throw ()

+@[app_unexpander Name.mkStr1] def unexpandMkStr1 : Lean.PrettyPrinter.Unexpander
+  | `($(_) $a:str) => return mkNode `Lean.Parser.Term.quotedName #[Syntax.mkNameLit ("`" ++  a.getString)]
+  | _  => throw ()
+
+@[app_unexpander Name.mkStr2] def unexpandMkStr2 : Lean.PrettyPrinter.Unexpander
+  | `($(_) $a1:str $a2:str) => return mkNode `Lean.Parser.Term.quotedName #[Syntax.mkNameLit ("`" ++ a1.getString ++ "." ++ a2.getString)]
+  | _  => throw ()
+
+@[app_unexpander Name.mkStr3] def unexpandMkStr3 : Lean.PrettyPrinter.Unexpander
+  | `($(_) $a1:str $a2:str $a3:str) => return mkNode `Lean.Parser.Term.quotedName #[Syntax.mkNameLit ("`" ++ a1.getString ++ "." ++ a2.getString ++ "." ++ a3.getString)]
+  | _  => throw ()
+
+@[app_unexpander Name.mkStr4] def unexpandMkStr4 : Lean.PrettyPrinter.Unexpander
+  | `($(_) $a1:str $a2:str $a3:str $a4:str) => return mkNode `Lean.Parser.Term.quotedName #[Syntax.mkNameLit ("`" ++ a1.getString ++ "." ++ a2.getString ++ "." ++ a3.getString ++ "." ++ a4.getString)]
+  | _  => throw ()
+
+@[app_unexpander Name.mkStr5] def unexpandMkStr5 : Lean.PrettyPrinter.Unexpander
+  | `($(_) $a1:str $a2:str $a3:str $a4:str $a5:str) => return mkNode `Lean.Parser.Term.quotedName #[Syntax.mkNameLit ("`" ++ a1.getString ++ "." ++ a2.getString ++ "." ++ a3.getString ++ "." ++ a4.getString ++ "." ++ a5.getString)]
+  | _  => throw ()
+
+@[app_unexpander Name.mkStr6] def unexpandMkStr6 : Lean.PrettyPrinter.Unexpander
+  | `($(_) $a1:str $a2:str $a3:str $a4:str $a5:str $a6:str) => return mkNode `Lean.Parser.Term.quotedName #[Syntax.mkNameLit ("`" ++ a1.getString ++ "." ++ a2.getString ++ "." ++ a3.getString ++ "." ++ a4.getString ++ "." ++ a5.getString ++ "." ++ a6.getString)]
+  | _  => throw ()
+
+@[app_unexpander Name.mkStr7] def unexpandMkStr7 : Lean.PrettyPrinter.Unexpander
+  | `($(_) $a1:str $a2:str $a3:str $a4:str $a5:str $a6:str $a7:str) => return mkNode `Lean.Parser.Term.quotedName #[Syntax.mkNameLit ("`" ++ a1.getString ++ "." ++ a2.getString ++ "." ++ a3.getString ++ "." ++ a4.getString ++ "." ++ a5.getString ++ "." ++ a6.getString ++ "." ++ a7.getString)]
+  | _  => throw ()
+
+@[app_unexpander Name.mkStr8] def unexpandMkStr8 : Lean.PrettyPrinter.Unexpander
+  | `($(_) $a1:str $a2:str $a3:str $a4:str $a5:str $a6:str $a7:str $a8:str) => return mkNode `Lean.Parser.Term.quotedName #[Syntax.mkNameLit ("`" ++ a1.getString ++ "." ++ a2.getString ++ "." ++ a3.getString ++ "." ++ a4.getString ++ "." ++ a5.getString ++ "." ++ a6.getString ++ "." ++ a7.getString ++ "." ++ a8.getString)]
+  | _  => throw ()
+
@[app_unexpander Array.empty] def unexpandArrayEmpty : Lean.PrettyPrinter.Unexpander
  | _ => `(#[])

--- a/src/Init/Prelude.lean
+++ b/src/Init/Prelude.lean
@@ -2716,6 +2716,28 @@ def Array.extract (as : Array α) (start stop : Nat) : Array α :=
  let sz' := Nat.sub (min stop as.size) start
  loop sz' start (mkEmpty sz')

+/--
+Auxiliary definition for `List.toArray`.
+`List.toArrayAux as r = r ++ as.toArray`
+-/
+@[inline_if_reduce]
+def List.toArrayAux : List α → Array α → Array α
+  | nil,       r => r
+  | cons a as, r => toArrayAux as (r.push a)
+
+/-- A non-tail-recursive version of `List.length`, used for `List.toArray`. -/
+@[inline_if_reduce]
+def List.redLength : List α → Nat
+  | nil       => 0
+  | cons _ as => as.redLength.succ
+
+/-- Convert a `List α` into an `Array α`. This is O(n) in the length of the list.  -/
+-- This function is exported to C, where it is called by `Array.mk`
+-- (the constructor) to implement this functionality.
+@[inline, match_pattern, pp_nodot, export lean_list_to_array]
+def List.toArrayImpl (as : List α) : Array α :=
+  as.toArrayAux (Array.mkEmpty as.redLength)
+
 /-- The typeclass which supplies the `>>=` "bind" function. See `Monad`. -/
 class Bind (m : Type u → Type v) where
  /-- If `x : m α` and `f : α → m β`, then `x >>= f : m β` represents the
@@ -2869,32 +2891,6 @@ instance (m n o) [MonadLift n o] [MonadLiftT m n] : MonadLiftT m o where
 instance (m) : MonadLiftT m m where
  monadLift x := x

-/--
-Typeclass used for adapting monads. This is similar to `MonadLift`, but instances are allowed to
-make use of default state for the purpose of synthesizing such an instance, if necessary.
-Every `MonadLift` instance gives a `MonadEval` instance.
-
-The purpose of this class is for the `#eval` command,
-which looks for a `MonadEval m CommandElabM` or `MonadEval m IO` instance.
-/
-class MonadEval (m : semiOutParam (Type u → Type v)) (n : Type u → Type w) where
-  /-- Evaluates a value from monad `m` into monad `n`. -/
-  monadEval : {α : Type u} → m α → n α
-
-instance [MonadLift m n] : MonadEval m n where
-  monadEval := MonadLift.monadLift
-
-/-- The transitive closure of `MonadEval`. -/
-class MonadEvalT (m : Type u → Type v) (n : Type u → Type w) where
-  /-- Evaluates a value from monad `m` into monad `n`. -/
-  monadEval : {α : Type u} → m α → n α
-
-instance (m n o) [MonadEval n o] [MonadEvalT m n] : MonadEvalT m o where
-  monadEval x := MonadEval.monadEval (m := n) (MonadEvalT.monadEval x)
-
-instance (m) : MonadEvalT m m where
-  monadEval x := x
-
 /--
 A functor in the category of monads. Can be used to lift monad-transforming functions.
 Based on [`MFunctor`] from the `pipes` Haskell package, but not restricted to
--- a/src/Init/PropLemmas.lean
+++ b/src/Init/PropLemmas.lean
@@ -352,10 +352,10 @@ theorem not_forall_of_exists_not {p : α → Prop} : (∃ x, ¬p x) → ¬∀ x,
@[simp] theorem exists_or_eq_left' (y : α) (p : α → Prop) : ∃ x : α, y = x ∨ p x := ⟨y, .inl rfl⟩
@[simp] theorem exists_or_eq_right' (y : α) (p : α → Prop) : ∃ x : α, p x ∨ y = x := ⟨y, .inr rfl⟩

-theorem exists_prop' {p : Prop} : (∃ _ : α, p) ↔ Nonempty α ∧ p :=
+@[simp] theorem exists_prop' {p : Prop} : (∃ _ : α, p) ↔ Nonempty α ∧ p :=
  ⟨fun ⟨a, h⟩ => ⟨⟨a⟩, h⟩, fun ⟨⟨a⟩, h⟩ => ⟨a, h⟩⟩

-@[simp] theorem exists_prop : (∃ _h : a, b) ↔ a ∧ b :=
+theorem exists_prop : (∃ _h : a, b) ↔ a ∧ b :=
  ⟨fun ⟨hp, hq⟩ => ⟨hp, hq⟩, fun ⟨hp, hq⟩ => ⟨hp, hq⟩⟩

@[simp] theorem exists_apply_eq_apply (f : α → β) (a' : α) : ∃ a, f a = f a' := ⟨a', rfl⟩
@@ -458,7 +458,7 @@ theorem Decidable.imp_iff_not_or [Decidable a] : (a → b) ↔ (¬a ∨ b) :=
 theorem Decidable.imp_iff_or_not [Decidable b] : b → a ↔ a ∨ ¬b :=
  Decidable.imp_iff_not_or.trans or_comm

-theorem Decidable.imp_or [Decidable a] : (a → b ∨ c) ↔ (a → b) ∨ (a → c) :=
+theorem Decidable.imp_or [h : Decidable a] : (a → b ∨ c) ↔ (a → b) ∨ (a → c) :=
  if h : a then by
    rw [imp_iff_right h, imp_iff_right h, imp_iff_right h]
  else by
--- a/src/Init/System/IO.lean
+++ b/src/Init/System/IO.lean
@@ -928,6 +928,41 @@ def withIsolatedStreams [Monad m] [MonadFinally m] [MonadLiftT BaseIO m] (x : m
 end FS
 end IO

+universe u
+
+namespace Lean
+
+/-- Typeclass used for presenting the output of an `#eval` command. -/
+class Eval (α : Type u) where
+  -- We default `hideUnit` to `true`, but set it to `false` in the direct call from `#eval`
+  -- so that `()` output is hidden in chained instances such as for some `IO Unit`.
+  -- We take `Unit → α` instead of `α` because ‵α` may contain effectful debugging primitives (e.g., `dbg_trace`)
+  eval : (Unit → α) → (hideUnit : Bool := true) → IO Unit
+
+instance instEval [ToString α] : Eval α where
+  eval a _ := IO.println (toString (a ()))
+
+instance [Repr α] : Eval α where
+  eval a _ := IO.println (repr (a ()))
+
+instance : Eval Unit where
+  eval u hideUnit := if hideUnit then pure () else IO.println (repr (u ()))
+
+instance [Eval α] : Eval (IO α) where
+  eval x _ := do
+    let a ← x ()
+    Eval.eval fun _ => a
+
+instance [Eval α] : Eval (BaseIO α) where
+  eval x _ := do
+    let a ← x ()
+    Eval.eval fun _ => a
+
+def runEval [Eval α] (a : Unit → α) : IO (String × Except IO.Error Unit) :=
+  IO.FS.withIsolatedStreams (Eval.eval a false |>.toBaseIO)
+
+end Lean
+
 syntax "println! " (interpolatedStr(term) <|> term) : term

 macro_rules
--- a/src/Init/Tactics.lean
+++ b/src/Init/Tactics.lean
@@ -149,27 +149,26 @@ syntax (name := assumption) "assumption" : tactic

 /--
 `contradiction` closes the main goal if its hypotheses are "trivially contradictory".
-
 - Inductive type/family with no applicable constructors
-  ```lean
-  example (h : False) : p := by contradiction
-  ```
+```lean
+example (h : False) : p := by contradiction
+```
 - Injectivity of constructors
-  ```lean
-  example (h : none = some true) : p := by contradiction  --
-  ```
+```lean
+example (h : none = some true) : p := by contradiction  --
+```
 - Decidable false proposition
-  ```lean
-  example (h : 2 + 2 = 3) : p := by contradiction
-  ```
+```lean
+example (h : 2 + 2 = 3) : p := by contradiction
+```
 - Contradictory hypotheses
-  ```lean
-  example (h : p) (h' : ¬ p) : q := by contradiction
-  ```
+```lean
+example (h : p) (h' : ¬ p) : q := by contradiction
+```
 - Other simple contradictions such as
-  ```lean
-  example (x : Nat) (h : x ≠ x) : p := by contradiction
-  ```
+```lean
+example (x : Nat) (h : x ≠ x) : p := by contradiction
+```
 -/
 syntax (name := contradiction) "contradiction" : tactic

@@ -364,24 +363,31 @@ syntax (name := fail) "fail" (ppSpace str)? : tactic
 syntax (name := eqRefl) "eq_refl" : tactic

 /--
-This tactic applies to a goal whose target has the form `x ~ x`,
-where `~` is equality, heterogeneous equality or any relation that
-has a reflexivity lemma tagged with the attribute @[refl].
+`rfl` tries to close the current goal using reflexivity.
+This is supposed to be an extensible tactic and users can add their own support
+for new reflexive relations.
+
+Remark: `rfl` is an extensible tactic. We later add `macro_rules` to try different
+reflexivity theorems (e.g., `Iff.rfl`).
 -/
-syntax "rfl" : tactic
+macro "rfl" : tactic => `(tactic| case' _ => fail "The rfl tactic failed. Possible reasons:
+- The goal is not a reflexive relation (neither `=` nor a relation with a @[refl] lemma).
+- The arguments of the relation are not equal.
+Try using the reflexivity lemma for your relation explicitly, e.g. `exact Eq.refl _` or
+`exact HEq.rfl` etc.")
+
+macro_rules | `(tactic| rfl) => `(tactic| eq_refl)
+macro_rules | `(tactic| rfl) => `(tactic| exact HEq.rfl)

 /--
-The same as `rfl`, but without trying `eq_refl` at the end.
+This tactic applies to a goal whose target has the form `x ~ x`,
+where `~` is a reflexive relation other than `=`,
+that is, a relation which has a reflexive lemma tagged with the attribute @[refl].
 -/
 syntax (name := applyRfl) "apply_rfl" : tactic

-- We try `apply_rfl` first, because it produces a nice error message
 macro_rules | `(tactic| rfl) => `(tactic| apply_rfl)

-- But, mostly for backward compatibility, we try `eq_refl` too (reduces more aggressively)
-macro_rules | `(tactic| rfl) => `(tactic| eq_refl)
-- Also for backward compatibility, because `exact` can trigger the implicit lambda feature (see #5366)
-macro_rules | `(tactic| rfl) => `(tactic| exact HEq.rfl)
 /--
 `rfl'` is similar to `rfl`, but disables smart unfolding and unfolds all kinds of definitions,
 theorems included (relevant for declarations defined by well-founded recursion).
@@ -788,7 +794,7 @@ syntax inductionAlt  := ppDedent(ppLine) inductionAltLHS+ " => " (hole <|> synth
 After `with`, there is an optional tactic that runs on all branches, and
 then a list of alternatives.
 -/
-syntax inductionAlts := " with" (ppSpace colGt tactic)? withPosition((colGe inductionAlt)+)
+syntax inductionAlts := " with" (ppSpace tactic)? withPosition((colGe inductionAlt)+)

 /--
 Assuming `x` is a variable in the local context with an inductive type,
@@ -1159,9 +1165,6 @@ Currently the preprocessor is implemented as `try simp only [bv_toNat] at *`.
 -/
 macro "bv_omega" : tactic => `(tactic| (try simp only [bv_toNat] at *) <;> omega)

-/-- Implementation of `ac_nf` (the full `ac_nf` calls `trivial` afterwards). -/
-syntax (name := acNf0) "ac_nf0" (location)? : tactic
-
 /-- Implementation of `norm_cast` (the full `norm_cast` calls `trivial` afterwards). -/
 syntax (name := normCast0) "norm_cast0" (location)? : tactic

@@ -1212,24 +1215,6 @@ See also `push_cast`, which moves casts inwards rather than lifting them outward
 macro "norm_cast" loc:(location)? : tactic =>
  `(tactic| norm_cast0 $[$loc]? <;> try trivial)

-/--
-`ac_nf` normalizes equalities up to application of an associative and commutative operator.
- `ac_nf` normalizes all hypotheses and the goal target of the goal.
- `ac_nf at l` normalizes at location(s) `l`, where `l` is either `*` or a
-  list of hypotheses in the local context. In the latter case, a turnstile `⊢` or `|-`
-  can also be used, to signify the target of the goal.
-```
-instance : Associative (α := Nat) (.+.) := ⟨Nat.add_assoc⟩
-instance : Commutative (α := Nat) (.+.) := ⟨Nat.add_comm⟩
-
-example (a b c d : Nat) : a + b + c + d = d + (b + c) + a := by
- ac_nf
- -- goal: a + (b + (c + d)) = a + (b + (c + d))
-```
-/
-macro "ac_nf" loc:(location)? : tactic =>
-  `(tactic| ac_nf0 $[$loc]? <;> try trivial)
-
 /--
 `push_cast` rewrites the goal to move certain coercions (*casts*) inward, toward the leaf nodes.
 This uses `norm_cast` lemmas in the forward direction.
--- a/src/Init/WF.lean
+++ b/src/Init/WF.lean
@@ -249,8 +249,8 @@ theorem lex_def {r : α → α → Prop} {s : β → β → Prop} {p q : α ×
    Prod.Lex r s p q ↔ r p.1 q.1 ∨ p.1 = q.1 ∧ s p.2 q.2 :=
  ⟨fun h => by cases h <;> simp [*], fun h =>
    match p, q, h with
-    | _, _, Or.inl h => Lex.left _ _ h
-    | (_, _), (_, _), Or.inr ⟨e, h⟩ => by subst e; exact Lex.right _ h⟩
+    | (a, b), (c, d), Or.inl h => Lex.left _ _ h
+    | (a, b), (c, d), Or.inr ⟨e, h⟩ => by subst e; exact Lex.right _ h⟩

 namespace Lex

--- a/src/Lean.lean
+++ b/src/Lean.lean
@@ -20,6 +20,7 @@ import Lean.MetavarContext
 import Lean.AuxRecursor
 import Lean.Meta
 import Lean.Util
+import Lean.Eval
 import Lean.Structure
 import Lean.PrettyPrinter
 import Lean.CoreM
@@ -37,4 +38,3 @@ import Lean.Linter
 import Lean.SubExpr
 import Lean.LabelAttribute
 import Lean.AddDecl
-import Lean.Replay
--- a/src/Lean/Attributes.lean
+++ b/src/Lean/Attributes.lean
@@ -305,16 +305,15 @@ def registerAttributeImplBuilder (builderId : Name) (builder : AttributeImplBuil
  if table.contains builderId then throw (IO.userError ("attribute implementation builder '" ++ toString builderId ++ "' has already been declared"))
  attributeImplBuilderTableRef.modify fun table => table.insert builderId builder

-structure AttributeExtensionOLeanEntry where
-  builderId : Name
-  ref : Name
-  args : List DataValue
-
-def mkAttributeImplOfEntry (e : AttributeExtensionOLeanEntry) : IO AttributeImpl := do
+def mkAttributeImplOfBuilder (builderId ref : Name) (args : List DataValue) : IO AttributeImpl := do
  let table ← attributeImplBuilderTableRef.get
-  match table[e.builderId]? with
-  | none         => throw (IO.userError ("unknown attribute implementation builder '" ++ toString e.builderId ++ "'"))
-  | some builder => IO.ofExcept <| builder e.ref e.args
+  match table[builderId]? with
+  | none         => throw (IO.userError ("unknown attribute implementation builder '" ++ toString builderId ++ "'"))
+  | some builder => IO.ofExcept <| builder ref args
+
+inductive AttributeExtensionOLeanEntry where
+  | decl (declName : Name) -- `declName` has type `AttributeImpl`
+  | builder (builderId ref : Name) (args : List DataValue)

 structure AttributeExtensionState where
  newEntries : List AttributeExtensionOLeanEntry := []
@@ -338,13 +337,19 @@ unsafe def mkAttributeImplOfConstantUnsafe (env : Environment) (opts : Options)
@[implemented_by mkAttributeImplOfConstantUnsafe]
 opaque mkAttributeImplOfConstant (env : Environment) (opts : Options) (declName : Name) : Except String AttributeImpl

+def mkAttributeImplOfEntry (env : Environment) (opts : Options) (e : AttributeExtensionOLeanEntry) : IO AttributeImpl :=
+  match e with
+  | .decl declName              => IO.ofExcept <| mkAttributeImplOfConstant env opts declName
+  | .builder builderId ref args => mkAttributeImplOfBuilder builderId ref args
+
 private def AttributeExtension.addImported (es : Array (Array AttributeExtensionOLeanEntry)) : ImportM AttributeExtensionState := do
+  let ctx ← read
  let map ← attributeMapRef.get
  let map ← es.foldlM
    (fun map entries =>
      entries.foldlM
        (fun (map : Std.HashMap Name AttributeImpl) entry => do
-          let attrImpl ← mkAttributeImplOfEntry entry
+          let attrImpl ← mkAttributeImplOfEntry ctx.env ctx.opts entry
          return map.insert attrImpl.name attrImpl)
        map)
    map
@@ -395,13 +400,19 @@ def getAttributeImpl (env : Environment) (attrName : Name) : Except String Attri
  | some attr => pure attr
  | none      => throw ("unknown attribute '" ++ toString attrName ++ "'")

+def registerAttributeOfDecl (env : Environment) (opts : Options) (attrDeclName : Name) : Except String Environment := do
+  let attrImpl ← mkAttributeImplOfConstant env opts attrDeclName
+  if isAttribute env attrImpl.name then
+    throw ("invalid builtin attribute declaration, '" ++ toString attrImpl.name ++ "' has already been used")
+  else
+    return attributeExtension.addEntry env (.decl attrDeclName, attrImpl)
+
 def registerAttributeOfBuilder (env : Environment) (builderId ref : Name) (args : List DataValue) : IO Environment := do
-  let entry := {builderId, ref, args}
-  let attrImpl ← mkAttributeImplOfEntry entry
+  let attrImpl ← mkAttributeImplOfBuilder builderId ref args
  if isAttribute env attrImpl.name then
    throw (IO.userError ("invalid builtin attribute declaration, '" ++ toString attrImpl.name ++ "' has already been used"))
  else
-    return attributeExtension.addEntry env (entry, attrImpl)
+    return attributeExtension.addEntry env (.builder builderId ref args, attrImpl)

 def Attribute.add (declName : Name) (attrName : Name) (stx : Syntax) (kind := AttributeKind.global) : AttrM Unit := do
  let attr ← ofExcept <| getAttributeImpl (← getEnv) attrName
--- a/src/Lean/Compiler/IR/SimpCase.lean
+++ b/src/Lean/Compiler/IR/SimpCase.lean
@@ -20,18 +20,18 @@ def ensureHasDefault (alts : Array Alt) : Array Alt :=
 private def getOccsOf (alts : Array Alt) (i : Nat) : Nat := Id.run do
  let aBody := (alts.get! i).body
  let mut n := 1
-  for h : j in [i+1:alts.size] do
-    if alts[j].body == aBody then
+  for j in [i+1:alts.size] do
+    if alts[j]!.body == aBody then
      n := n+1
  return n

 private def maxOccs (alts : Array Alt) : Alt × Nat := Id.run do
  let mut maxAlt := alts[0]!
  let mut max    := getOccsOf alts 0
-  for h : i in [1:alts.size] do
+  for i in [1:alts.size] do
    let curr := getOccsOf alts i
    if curr > max then
-       maxAlt := alts[i]
+       maxAlt := alts[i]!
       max    := curr
  return (maxAlt, max)

--- a/src/Lean/Compiler/LCNF/Check.lean
+++ b/src/Lean/Compiler/LCNF/Check.lean
@@ -110,8 +110,8 @@ def isCtorParam (f : Expr) (i : Nat) : CoreM Bool := do
 def checkAppArgs (f : Expr) (args : Array Arg) : CheckM Unit := do
  let mut fType ← inferType f
  let mut j := 0
-  for h : i in [:args.size] do
-    let arg := args[i]
+  for i in [:args.size] do
+    let arg := args[i]!
    if fType.isErased then
      return ()
    fType := fType.headBeta
--- a/src/Lean/Compiler/LCNF/ElimDeadBranches.lean
+++ b/src/Lean/Compiler/LCNF/ElimDeadBranches.lean
@@ -505,8 +505,8 @@ ones. Return whether any `Value` got updated in the process.
 -/
 def inferStep : InterpM Bool := do
  let ctx ← read
-  for h : idx in [0:ctx.decls.size] do
-    let decl := ctx.decls[idx]
+  for idx in [0:ctx.decls.size] do
+    let decl := ctx.decls[idx]!
    if !decl.safe then
      continue

--- a/src/Lean/Compiler/LCNF/MonoTypes.lean
+++ b/src/Lean/Compiler/LCNF/MonoTypes.lean
@@ -48,8 +48,8 @@ def hasTrivialStructure? (declName : Name) : CoreM (Option TrivialStructureInfo)
  let [ctorName] := info.ctors | return none
  let mask ← getRelevantCtorFields ctorName
  let mut result := none
-  for h : i in [:mask.size] do
-    if mask[i] then
+  for i in [:mask.size] do
+    if mask[i]! then
      if result.isSome then return none
      result := some { ctorName, fieldIdx := i, numParams := info.numParams }
  return result
@@ -129,4 +129,4 @@ def getOtherDeclMonoType (declName : Name) : CoreM Expr := do
    modifyEnv fun env => monoTypeExt.modifyState env fun s => { s with mono := s.mono.insert declName type }
    return type

-end Lean.Compiler.LCNF
+end Lean.Compiler.LCNF
--- a/src/Lean/Compiler/LCNF/PullFunDecls.lean
+++ b/src/Lean/Compiler/LCNF/PullFunDecls.lean
@@ -96,9 +96,9 @@ where
    unless (← visited i) do
      modify fun (k, visited) => (k, visited.set! i true)
      let pi := ps[i]!
-      for h : j in [:ps.size] do
+      for j in [:ps.size] do
        unless (← visited j) do
-          let pj := ps[j]
+          let pj := ps[j]!
          if pj.used.contains pi.decl.fvarId then
            visit j
      modify fun (k, visited) => (pi.attach k, visited)
--- a/src/Lean/Compiler/LCNF/Simp/DefaultAlt.lean
+++ b/src/Lean/Compiler/LCNF/Simp/DefaultAlt.lean
@@ -18,10 +18,10 @@ or not.
 private def getMaxOccs (alts : Array Alt) : Alt × Nat := Id.run do
  let mut maxAlt := alts[0]!
  let mut max    := getNumOccsOf alts 0
-  for h : i in [1:alts.size] do
+  for i in [1:alts.size] do
    let curr := getNumOccsOf alts i
    if curr > max then
-       maxAlt := alts[i]
+       maxAlt := alts[i]!
       max    := curr
  return (maxAlt, max)
 where
@@ -34,8 +34,8 @@ where
  getNumOccsOf (alts : Array Alt) (i : Nat) : Nat := Id.run do
    let code := alts[i]!.getCode
    let mut n := 1
-    for h : j in [i+1:alts.size] do
-      if Code.alphaEqv alts[j].getCode code then
+    for j in [i+1:alts.size] do
+      if Code.alphaEqv alts[j]!.getCode code then
        n := n+1
    return n

--- a/src/Lean/Compiler/LCNF/Simp/JpCases.lean
+++ b/src/Lean/Compiler/LCNF/Simp/JpCases.lean
@@ -121,8 +121,8 @@ where
    let mut paramsNew := #[]
    let singleton : FVarIdSet := ({} : FVarIdSet).insert params[targetParamIdx]!.fvarId
    let dependsOnDiscr := k.dependsOn singleton || decls.any (·.dependsOn singleton)
-    for h : i in [:params.size] do
-      let param := params[i]
+    for i in [:params.size] do
+      let param := params[i]!
      if targetParamIdx == i then
        if dependsOnDiscr then
          paramsNew := paramsNew.push (← internalizeParam param)
@@ -300,3 +300,4 @@ builtin_initialize
  registerTraceClass `Compiler.simp.jpCases

 end Lean.Compiler.LCNF
+
--- a/src/Lean/Compiler/LCNF/SpecInfo.lean
+++ b/src/Lean/Compiler/LCNF/SpecInfo.lean
@@ -129,9 +129,9 @@ See comment at `.fixedNeutral`.
 -/
 private def hasFwdDeps (decl : Decl) (paramsInfo : Array SpecParamInfo) (j : Nat) : Bool := Id.run do
  let param := decl.params[j]!
-  for h : k in [j+1 : decl.params.size] do
+  for k in [j+1 : decl.params.size] do
    if paramsInfo[k]! matches .user | .fixedHO | .fixedInst then
-      let param' := decl.params[k]
+      let param' := decl.params[k]!
      if param'.type.containsFVar param.fvarId then
        return true
  return false
@@ -214,3 +214,4 @@ builtin_initialize
  registerTraceClass `Compiler.specialize.info

 end Lean.Compiler.LCNF
+
--- a/src/Lean/Compiler/LCNF/ToDecl.lean
+++ b/src/Lean/Compiler/LCNF/ToDecl.lean
@@ -50,9 +50,9 @@ partial def inlineMatchers (e : Expr) : CoreM Expr :=
      let numAlts := info.numAlts
      let altNumParams := info.altNumParams
      let rec inlineMatcher (i : Nat) (args : Array Expr) (letFVars : Array Expr) : MetaM Expr := do
-        if h : i < numAlts then
+        if i < numAlts then
          let altIdx := i + info.getFirstAltPos
-          let numParams := altNumParams[i]
+          let numParams := altNumParams[i]!
          let alt ← normalizeAlt args[altIdx]! numParams
          Meta.withLetDecl (← mkFreshUserName `_alt) (← Meta.inferType alt) alt fun altFVar =>
            inlineMatcher (i+1) (args.set! altIdx altFVar) (letFVars.push altFVar)
--- a/src/Lean/CoreM.lean
+++ b/src/Lean/CoreM.lean
@@ -7,6 +7,7 @@ prelude
 import Lean.Util.RecDepth
 import Lean.Util.Trace
 import Lean.Log
+import Lean.Eval
 import Lean.ResolveName
 import Lean.Elab.InfoTree.Types
 import Lean.MonadEnv
@@ -276,6 +277,12 @@ def mkFreshUserName (n : Name) : CoreM Name :=
  | Except.error (Exception.internal id _) => throw <| IO.userError <| "internal exception #" ++ toString id.idx
  | Except.ok a                            => return a

+instance [MetaEval α] : MetaEval (CoreM α) where
+  eval env opts x _ := do
+    let x : CoreM α := do try x finally printTraces
+    let (a, s) ← (withConsistentCtx x).toIO { fileName := "<CoreM>", fileMap := default, options := opts } { env := env }
+    MetaEval.eval s.env opts a (hideUnit := true)
+
 -- withIncRecDepth for a monad `m` such that `[MonadControlT CoreM n]`
 protected def withIncRecDepth [Monad m] [MonadControlT CoreM m] (x : m α) : m α :=
  controlAt CoreM fun runInBase => withIncRecDepth (runInBase x)
@@ -302,7 +309,7 @@ register_builtin_option debug.moduleNameAtTimeout : Bool := {
 def throwMaxHeartbeat (moduleName : Name) (optionName : Name) (max : Nat) : CoreM Unit := do
  let includeModuleName := debug.moduleNameAtTimeout.get (← getOptions)
  let atModuleName := if includeModuleName then s!" at `{moduleName}`" else ""
-  throw <| Exception.error (← getRef) <| .tagged `runtime.maxHeartbeats m!"\
+  throw <| Exception.error (← getRef) m!"\
    (deterministic) timeout{atModuleName}, maximum number of heartbeats ({max/1000}) has been reached\n\
    Use `set_option {optionName} <num>` to set the limit.\
    {useDiagnosticMsg}"
@@ -388,7 +395,10 @@ export Core (CoreM mkFreshUserName checkSystem withCurrHeartbeats)
  This function is a bit hackish. The heartbeat exception should probably be an internal exception.
  We used a similar hack at `Exception.isMaxRecDepth` -/
 def Exception.isMaxHeartbeat (ex : Exception) : Bool :=
-  ex matches Exception.error _ (.tagged `runtime.maxHeartbeats _)
+  match ex with
+  | Exception.error _ (MessageData.ofFormatWithInfos ⟨Std.Format.text msg, _⟩) =>
+    "(deterministic) timeout".isPrefixOf msg
+  | _ => false

 /-- Creates the expression `d → b` -/
 def mkArrow (d b : Expr) : CoreM Expr :=
--- a/src/Lean/Data/Lsp/LanguageFeatures.lean
+++ b/src/Lean/Data/Lsp/LanguageFeatures.lean
@@ -41,18 +41,6 @@ structure InsertReplaceEdit where
  replace : Range
  deriving FromJson, ToJson

-inductive CompletionItemTag where
-  | deprecated
-  deriving Inhabited, DecidableEq, Repr
-
-instance : ToJson CompletionItemTag where
-  toJson t := toJson (t.toCtorIdx + 1)
-
-instance : FromJson CompletionItemTag where
-  fromJson? v := do
-    let i : Nat ← fromJson? v
-    return CompletionItemTag.ofNat (i-1)
-
 structure CompletionItem where
  label          : String
  detail?        : Option String := none
@@ -61,8 +49,8 @@ structure CompletionItem where
  textEdit?      : Option InsertReplaceEdit := none
  sortText?      : Option String := none
  data?          : Option Json := none
-  tags?          : Option (Array CompletionItemTag) := none
  /-
+  tags? : CompletionItemTag[]
  deprecated? : boolean
  preselect? : boolean
  filterText? : string
@@ -71,8 +59,7 @@ structure CompletionItem where
  insertTextMode? : InsertTextMode
  additionalTextEdits? : TextEdit[]
  commitCharacters? : string[]
-  command? : Command
-  -/
+  command? : Command -/
  deriving FromJson, ToJson, Inhabited

 structure CompletionList where
--- a/src/Lean/Data/Trie.lean
+++ b/src/Lean/Data/Trie.lean
@@ -76,7 +76,7 @@ partial def upsert (t : Trie α) (s : String) (f : Option α → α) : Trie α :
        let c := s.getUtf8Byte i h
        if c == c'
        then node1 v c' (loop (i + 1) t')
-        else
+        else 
          let t := insertEmpty (i + 1)
          node v (.mk #[c, c']) #[t, t']
      else
@@ -190,7 +190,7 @@ private partial def toStringAux {α : Type} : Trie α → List Format
  | node1 _ c t =>
    [ format (repr c), Format.group $ Format.nest 4 $ flip Format.joinSep Format.line $ toStringAux t ]
  | node _ cs ts =>
-    List.flatten $ List.zipWith (fun c t =>
+    List.join $ List.zipWith (fun c t =>
      [ format (repr c), (Format.group $ Format.nest 4 $ flip Format.joinSep Format.line $ toStringAux t) ]
    ) cs.toList ts.toList

--- a/src/Lean/DeclarationRange.lean
+++ b/src/Lean/DeclarationRange.lean
@@ -42,9 +42,8 @@ builtin_initialize declRangeExt : MapDeclarationExtension DeclarationRanges ←
 def addBuiltinDeclarationRanges (declName : Name) (declRanges : DeclarationRanges) : IO Unit :=
  builtinDeclRanges.modify (·.insert declName declRanges)

-def addDeclarationRanges [Monad m] [MonadEnv m] (declName : Name) (declRanges : DeclarationRanges) : m Unit := do
-  unless declRangeExt.contains (← getEnv) declName do
-    modifyEnv fun env => declRangeExt.insert env declName declRanges
+def addDeclarationRanges [MonadEnv m] (declName : Name) (declRanges : DeclarationRanges) : m Unit :=
+  modifyEnv fun env => declRangeExt.insert env declName declRanges

 def findDeclarationRangesCore? [Monad m] [MonadEnv m] (declName : Name) : m (Option DeclarationRanges) :=
  return declRangeExt.find? (← getEnv) declName
--- a/src/Lean/DocString/Extension.lean
+++ b/src/Lean/DocString/Extension.lean
@@ -16,7 +16,7 @@ import Init.Data.String.Extra
 namespace Lean

 private builtin_initialize builtinDocStrings : IO.Ref (NameMap String) ← IO.mkRef {}
-builtin_initialize docStringExt : MapDeclarationExtension String ← mkMapDeclarationExtension
+private builtin_initialize docStringExt : MapDeclarationExtension String ← mkMapDeclarationExtension

 def addBuiltinDocString (declName : Name) (docString : String) : IO Unit :=
  builtinDocStrings.modify (·.insert declName docString.removeLeadingSpaces)
--- a/src/Lean/Elab.lean
+++ b/src/Lean/Elab.lean
@@ -42,7 +42,6 @@ import Lean.Elab.Notation
 import Lean.Elab.Mixfix
 import Lean.Elab.MacroRules
 import Lean.Elab.BuiltinCommand
-import Lean.Elab.BuiltinEvalCommand
 import Lean.Elab.RecAppSyntax
 import Lean.Elab.Eval
 import Lean.Elab.Calc
--- a/src/Lean/Elab/App.lean
+++ b/src/Lean/Elab/App.lean
@@ -411,23 +411,21 @@ private def finalize : M Expr := do
  synthesizeAppInstMVars
  return e

-/--
-Returns a named argument that depends on the next argument, otherwise `none`.
-/
-private def findNamedArgDependsOnCurrent? : M (Option NamedArg) := do
+/-- Return `true` if there is a named argument that depends on the next argument. -/
+private def anyNamedArgDependsOnCurrent : M Bool := do
  let s ← get
  if s.namedArgs.isEmpty then
-    return none
+    return false
  else
    forallTelescopeReducing s.fType fun xs _ => do
      let curr := xs[0]!
-      for h : i in [1:xs.size] do
-        let xDecl ← xs[i].fvarId!.getDecl
-        if let some arg := s.namedArgs.find? fun arg => arg.name == xDecl.userName then
+      for i in [1:xs.size] do
+        let xDecl ← xs[i]!.fvarId!.getDecl
+        if s.namedArgs.any fun arg => arg.name == xDecl.userName then
          /- Remark: a default value at `optParam` does not count as a dependency -/
          if (← exprDependsOn xDecl.type.cleanupAnnotations curr.fvarId!) then
-            return arg
-      return none
+            return true
+      return false


 /-- Return `true` if there are regular or named arguments to be processed. -/
@@ -435,13 +433,11 @@ private def hasArgsToProcess : M Bool := do
  let s ← get
  return !s.args.isEmpty || !s.namedArgs.isEmpty

-/--
-Returns the argument syntax if the next argument at `args` is of the form `_`.
-/
-private def nextArgHole? : M (Option Syntax) := do
+/-- Return `true` if the next argument at `args` is of the form `_` -/
+private def isNextArgHole : M Bool := do
  match (← get).args with
-  | Arg.stx stx@(Syntax.node _ ``Lean.Parser.Term.hole _) :: _ => pure stx
-  | _ => pure none
+  | Arg.stx (Syntax.node _ ``Lean.Parser.Term.hole _) :: _ => pure true
+  | _ => pure false

 /--
  Return `true` if the next argument to be processed is the outparam of a local instance, and it the result type
@@ -516,9 +512,8 @@ where

 mutual
  /--
-  Create a fresh local variable with the current binder name and argument type, add it to `etaArgs` and `f`,
-  and then execute the main loop.
-  -/
+    Create a fresh local variable with the current binder name and argument type, add it to `etaArgs` and `f`,
+    and then execute the main loop.-/
  private partial def addEtaArg (argName : Name) : M Expr := do
    let n    ← getBindingName
    let type ← getArgExpectedType
@@ -527,9 +522,6 @@ mutual
      addNewArg argName x
      main

-  /--
-  Create a fresh metavariable for the implicit argument, add it to `f`, and then execute the main loop.
-  -/
  private partial def addImplicitArg (argName : Name) : M Expr := do
    let argType ← getArgExpectedType
    let arg ← if (← isNextOutParamOfLocalInstanceAndResult) then
@@ -547,47 +539,35 @@ mutual
    main

  /--
-  Process a `fType` of the form `(x : A) → B x`.
-  This method assume `fType` is a function type.
-  -/
+    Process a `fType` of the form `(x : A) → B x`.
+    This method assume `fType` is a function type -/
  private partial def processExplicitArg (argName : Name) : M Expr := do
    match (← get).args with
    | arg::args =>
-      -- Note: currently the following test never succeeds in explicit mode since `@x.f` notation does not exist.
-      if let some true := NamedArg.suppressDeps <$> (← findNamedArgDependsOnCurrent?) then
+      if (← anyNamedArgDependsOnCurrent) then
        /-
-        We treat the explicit argument `argName` as implicit
-        if we have a named arguments that depends on it whose `suppressDeps` flag set to `true`.
-        The motivation for this is class projections (issue #1851).
-        In some cases, class projections can have explicit parameters. For example, in
+        We treat the explicit argument `argName` as implicit if we have named arguments that depend on it.
+        The idea is that this explicit argument can be inferred using the type of the named argument one.
+        Note that we also use this approach in the branch where there are no explicit arguments left.
+        This is important to make sure the system behaves in a uniform way.
+        Moreover, users rely on this behavior. For example, consider the example on issue #1851
        ```
        class Approx {α : Type} (a : α) (X : Type) : Type where
          val : X
-        ```
-        the type of `Approx.val` is `{α : Type} → (a : α) → {X : Type} → [self : Approx a X] → X`.
-        Note that the parameter `a` is explicit since there is no way to infer it from the expected
-        type or from the types of other explicit parameters.
-        Being a parameter of the class, `a` is determined by the type of `self`.

-        Consider
-        ```
-        variable {α β X Y : Type} {f' : α → β} {x' : α} [f : Approx f' (X → Y)]
-        ```
-        Recall that `f.val` is, to first approximation, sugar for `Approx.val (self := f)`.
-        Without further refinement, this would expand to `fun f'' : α → β => Approx.val f'' f`,
-        which is a type error, since `f''` must be defeq to `f'`.
-        Furthermore, with projection notation, users expect all structure parameters
-        to be uniformly implicit; after all, they are determined by `self`.
-        To handle this, the `(self := f)` named argument is annotated with the `suppressDeps` flag.
-        This causes the `a` parameter to become implicit, and `f.val` instead expands to `Approx.val f' f`.
+        variable {α β X Y : Type} {f' : α → β} {x' : α} [f : Approx f' (X → Y)] [x : Approx x' X]

-        This feature previously was enabled for *all* explicit arguments, which confused users
-        and was frequently reported as a bug (issue #1867).
-        Now it is only enabled for the `self` argument in structure projections.
-
-        We used to do this only when `(← get).args` was empty,
-        but it created an asymmetry because `f.val` worked as expected,
-        yet one would have to write `f.val _ x` when there are further arguments.
+        #check f.val
+        #check f.val x.val
+        ```
+        The type of `Approx.val` is `{α : Type} → (a : α) → {X : Type} → [self : Approx a X] → X`
+        Note that the argument `a` is explicit since there is no way to infer it from the expected
+        type or the type of other explicit arguments.
+        Recall that `f.val` is sugar for `Approx.val (self := f)`. In both `#check` commands above
+        the user assumed that `a` does not need to be provided since it can be inferred from the type
+        of `self`.
+        We used to that only in the branch where `(← get).args` was empty, but it created an asymmetry
+        because `#check f.val` worked as expected, but one would have to write `#check f.val _ x.val`
        -/
        return (← addImplicitArg argName)
      propagateExpectedType arg
@@ -604,6 +584,7 @@ mutual
        match evalSyntaxConstant env opts tacticDecl with
        | Except.error err       => throwError err
        | Except.ok tacticSyntax =>
+          -- TODO(Leo): does this work correctly for tactic sequences?
          let tacticBlock ← `(by $(⟨tacticSyntax⟩))
          /-
          We insert position information from the current ref into `stx` everywhere, simulating this being
@@ -615,32 +596,24 @@ mutual
          -/
          let info := (← getRef).getHeadInfo
          let tacticBlock := tacticBlock.raw.rewriteBottomUp (·.setInfo info)
-          let mvar ← mkTacticMVar argType.consumeTypeAnnotations tacticBlock (.autoParam argName)
-          -- Note(kmill): We are adding terminfo to simulate a previous implementation that elaborated `tacticBlock`.
-          -- We should look into removing this since terminfo for synthetic syntax is suspect,
-          -- but we noted it was necessary to preserve the behavior of the unused variable linter.
-          addTermInfo' tacticBlock mvar
-          let argNew := Arg.expr mvar
+          let argNew := Arg.stx tacticBlock
          propagateExpectedType argNew
          elabAndAddNewArg argName argNew
          main
      | false, _, some _ =>
        throwError "invalid autoParam, argument must be a constant"
      | _, _, _ =>
-        if (← read).ellipsis then
-          addImplicitArg argName
-        else if !(← get).namedArgs.isEmpty then
-          if let some _ ← findNamedArgDependsOnCurrent? then
-            /-
-            Dependencies of named arguments cannot be turned into eta arguments
-            since they are determined by the named arguments.
-            Instead we can turn them into implicit arguments.
-            -/
+        if !(← get).namedArgs.isEmpty then
+          if (← anyNamedArgDependsOnCurrent) then
+            addImplicitArg argName
+          else if (← read).ellipsis then
            addImplicitArg argName
          else
            addEtaArg argName
        else if !(← read).explicit then
-          if (← fTypeHasOptAutoParams) then
+          if (← read).ellipsis then
+            addImplicitArg argName
+          else if (← fTypeHasOptAutoParams) then
            addEtaArg argName
          else
            finalize
@@ -668,30 +641,24 @@ mutual
      finalize

  /--
-  Process a `fType` of the form `[x : A] → B x`.
-  This method assume `fType` is a function type.
-  -/
+    Process a `fType` of the form `[x : A] → B x`.
+    This method assume `fType` is a function type -/
  private partial def processInstImplicitArg (argName : Name) : M Expr := do
    if (← read).explicit then
-      if let some stx ← nextArgHole? then
-        -- We still use typeclass resolution for `_` arguments.
-        -- This behavior can be suppressed with `(_)`.
-        let ty ← getArgExpectedType
-        let arg ← mkInstMVar ty
-        addTermInfo' stx arg ty
+      if (← isNextArgHole) then
+        /- Recall that if '@' has been used, and the argument is '_', then we still use type class resolution -/
+        let arg ← mkFreshExprMVar (← getArgExpectedType) MetavarKind.synthetic
        modify fun s => { s with args := s.args.tail! }
+        addInstMVar arg.mvarId!
+        addNewArg argName arg
        main
      else
        processExplicitArg argName
    else
-      discard <| mkInstMVar (← getArgExpectedType)
-      main
-  where
-    mkInstMVar (ty : Expr) : M Expr := do
-      let arg ← mkFreshExprMVar ty MetavarKind.synthetic
+      let arg ← mkFreshExprMVar (← getArgExpectedType) MetavarKind.synthetic
      addInstMVar arg.mvarId!
      addNewArg argName arg
-      return arg
+      main

  /-- Elaborate function application arguments. -/
  partial def main : M Expr := do
@@ -722,104 +689,6 @@ end

 end ElabAppArgs

-
-/-! # Eliminator-like function application elaborator -/
-
-/--
-Information about an eliminator used by the elab-as-elim elaborator.
-This is not to be confused with `Lean.Meta.ElimInfo`, which is for `induction` and `cases`.
-The elab-as-elim routine is less restrictive in what counts as an eliminator, and it doesn't need
-to have a strict notion of what is a "target" — all it cares about are
-1. that the return type of a function is of the form `m ...` where `m` is a parameter
-   (unlike `induction` and `cases` eliminators, the arguments to `m`, known as "discriminants",
-   can be any expressions, not just parameters), and
-2. which arguments should be eagerly elaborated, to make discriminants be as elaborated as
-   possible for the expected type generalization procedure,
-   and which should be postponed (since they are the "minor premises").
-
-Note that the routine isn't doing induction/cases *on* particular expressions.
-The purpose of elab-as-elim is to successfully solve the higher-order unification problem
-between the return type of the function and the expected type.
-/
-structure ElabElimInfo where
-  /-- The eliminator. -/
-  elimExpr   : Expr
-  /-- The type of the eliminator. -/
-  elimType   : Expr
-  /-- The position of the motive parameter. -/
-  motivePos  : Nat
-  /--
-  Positions of "major" parameters (those that should be eagerly elaborated
-  because they can contribute to the motive inference procedure).
-  All parameters that are neither the motive nor a major parameter are "minor" parameters.
-  The major parameters include all of the parameters that transitively appear in the motive's arguments,
-  as well as "first-order" arguments that include such parameters,
-  since they too can help with elaborating discriminants.
-
-  For example, in the following theorem the argument `h : a = b`
-  should be elaborated eagerly because it contains `b`, which occurs in `motive b`.
-  ```
-  theorem Eq.subst' {α} {motive : α → Prop} {a b : α} (h : a = b) : motive a → motive b
-  ```
-  For another example, the term `isEmptyElim (α := α)` is an underapplied eliminator, and it needs
-  argument `α` to be elaborated eagerly to create a type-correct motive.
-  ```
-  def isEmptyElim [IsEmpty α] {p : α → Sort _} (a : α) : p a := ...
-  example {α : Type _} [IsEmpty α] : id (α → False) := isEmptyElim (α := α)
-  ```
-  -/
-  majorsPos : Array Nat := #[]
-  deriving Repr, Inhabited
-
-def getElabElimExprInfo (elimExpr : Expr) : MetaM ElabElimInfo := do
-  let elimType ← inferType elimExpr
-  trace[Elab.app.elab_as_elim] "eliminator {indentExpr elimExpr}\nhas type{indentExpr elimType}"
-  forallTelescopeReducing elimType fun xs type => do
-    let motive  := type.getAppFn
-    let motiveArgs := type.getAppArgs
-    unless motive.isFVar && motiveArgs.size > 0 do
-      throwError "unexpected eliminator resulting type{indentExpr type}"
-    let motiveType ← inferType motive
-    forallTelescopeReducing motiveType fun motiveParams motiveResultType => do
-      unless motiveParams.size == motiveArgs.size do
-        throwError "unexpected number of arguments at motive type{indentExpr motiveType}"
-      unless motiveResultType.isSort do
-        throwError "motive result type must be a sort{indentExpr motiveType}"
-    let some motivePos ← pure (xs.indexOf? motive) |
-      throwError "unexpected eliminator type{indentExpr elimType}"
-    /-
-    Compute transitive closure of fvars appearing in arguments to the motive.
-    These are the primary set of major parameters.
-    -/
-    let initMotiveFVars : CollectFVars.State := motiveArgs.foldl (init := {}) collectFVars
-    let motiveFVars ← xs.size.foldRevM (init := initMotiveFVars) fun i s => do
-      let x := xs[i]!
-      if s.fvarSet.contains x.fvarId! then
-        return collectFVars s (← inferType x)
-      else
-        return s
-    /- Collect the major parameter positions -/
-    let mut majorsPos := #[]
-    for h : i in [:xs.size] do
-      let x := xs[i]
-      unless motivePos == i do
-        let xType ← x.fvarId!.getType
-        /-
-        We also consider "first-order" types because we can reliably "extract" information from them.
-        We say a term is "first-order" if all applications are of the form `f ...` where `f` is a constant.
-        -/
-        let isFirstOrder (e : Expr) : Bool := Option.isNone <| e.find? fun e => e.isApp && !e.getAppFn.isConst
-        if motiveFVars.fvarSet.contains x.fvarId!
-            || (isFirstOrder xType
-                && Option.isSome (xType.find? fun e => e.isFVar && motiveFVars.fvarSet.contains e.fvarId!)) then
-          majorsPos := majorsPos.push i
-    trace[Elab.app.elab_as_elim] "motivePos: {motivePos}"
-    trace[Elab.app.elab_as_elim] "majorsPos: {majorsPos}"
-    return { elimExpr, elimType,  motivePos, majorsPos }
-
-def getElabElimInfo (elimName : Name) : MetaM ElabElimInfo := do
-  getElabElimExprInfo (← mkConstWithFreshMVarLevels elimName)
-
 builtin_initialize elabAsElim : TagAttribute ←
  registerTagAttribute `elab_as_elim
    "instructs elaborator that the arguments of the function application should be elaborated as were an eliminator"
@@ -834,15 +703,33 @@ builtin_initialize elabAsElim : TagAttribute ←
        let info ← getConstInfo declName
        if (← hasOptAutoParams info.type) then
          throwError "[elab_as_elim] attribute cannot be used in declarations containing optional and auto parameters"
-        discard <| getElabElimInfo declName
+        discard <| getElimInfo declName
      go.run' {} {}

+/-! # Eliminator-like function application elaborator -/
 namespace ElabElim

 /-- Context of the `elab_as_elim` elaboration procedure. -/
 structure Context where
-  elimInfo : ElabElimInfo
+  elimInfo : ElimInfo
  expectedType : Expr
+  /--
+  Position of additional arguments that should be elaborated eagerly
+  because they can contribute to the motive inference procedure.
+  For example, in the following theorem the argument `h : a = b`
+  should be elaborated eagerly because it contains `b` which occurs
+  in `motive b`.
+  ```
+  theorem Eq.subst' {α} {motive : α → Prop} {a b : α} (h : a = b) : motive a → motive b
+  ```
+  For another example, the term `isEmptyElim (α := α)` is an underapplied eliminator, and it needs
+  argument `α` to be elaborated eagerly to create a type-correct motive.
+  ```
+  def isEmptyElim [IsEmpty α] {p : α → Sort _} (a : α) : p a := ...
+  example {α : Type _} [IsEmpty α] : id (α → False) := isEmptyElim (α := α)
+  ```
+  -/
+  extraArgsPos : Array Nat

 /-- State of the `elab_as_elim` elaboration procedure. -/
 structure State where
@@ -854,6 +741,8 @@ structure State where
  namedArgs    : List NamedArg
  /-- User-provided arguments that still have to be processed. -/
  args         : List Arg
+  /-- Discriminants (targets) processed so far. -/
+  discrs       : Array (Option Expr)
  /-- Instance implicit arguments collected so far. -/
  instMVars    : Array MVarId := #[]
  /-- Position of the next argument to be processed. We use it to decide whether the argument is the motive or a discriminant. -/
@@ -899,7 +788,7 @@ def finalize : M Expr := do
  let some motive := (← get).motive?
    | throwError "failed to elaborate eliminator, insufficient number of arguments"
  trace[Elab.app.elab_as_elim] "motive: {motive}"
-  forallTelescope (← get).fType fun xs fType => do
+  forallTelescope (← get).fType fun xs _ => do
    trace[Elab.app.elab_as_elim] "xs: {xs}"
    let mut expectedType := (← read).expectedType
    trace[Elab.app.elab_as_elim] "expectedType:{indentD expectedType}"
@@ -908,7 +797,6 @@ def finalize : M Expr := do
    let mut f := (← get).f
    if xs.size > 0 then
      -- under-application, specialize the expected type using `xs`
-      -- Note: if we ever wanted to support optParams and autoParams, this is where it could be.
      assert! (← get).args.isEmpty
      for x in xs do
        let .forallE _ t b _ ← whnf expectedType | throwInsufficient
@@ -925,11 +813,18 @@ def finalize : M Expr := do
    trace[Elab.app.elab_as_elim] "expectedType after processing:{indentD expectedType}"
    let result := mkAppN f xs
    trace[Elab.app.elab_as_elim] "result:{indentD result}"
-    unless fType.getAppFn == (← get).motive? do
-      throwError "Internal error, eliminator target type isn't an application of the motive"
-    let discrs := fType.getAppArgs
-    trace[Elab.app.elab_as_elim] "discrs: {discrs}"
-    let motiveVal ← mkMotive discrs expectedType
+    let mut discrs := (← get).discrs
+    let idx := (← get).idx
+    if discrs.any Option.isNone then
+      for i in [idx:idx + xs.size], x in xs do
+        if let some tidx := (← read).elimInfo.targetsPos.indexOf? i then
+          discrs := discrs.set! tidx x
+    if let some idx := discrs.findIdx? Option.isNone then
+      -- This should not happen.
+      trace[Elab.app.elab_as_elim] "Internal error, missing target with index {idx}"
+      throwError "failed to elaborate eliminator, insufficient number of arguments"
+    trace[Elab.app.elab_as_elim] "discrs: {discrs.map Option.get!}"
+    let motiveVal ← mkMotive (discrs.map Option.get!) expectedType
    unless (← isTypeCorrect motiveVal) do
      throwError "failed to elaborate eliminator, motive is not type correct:{indentD motiveVal}"
    unless (← isDefEq motive motiveVal) do
@@ -963,6 +858,10 @@ def getNextArg? (binderName : Name) (binderInfo : BinderInfo) : M (LOption Arg)
 def setMotive (motive : Expr) : M Unit :=
  modify fun s => { s with motive? := motive }

+/-- Push the given expression into the `discrs` field in the state, where `i` is which target it is for. -/
+def addDiscr (i : Nat) (discr : Expr) : M Unit :=
+  modify fun s => { s with discrs := s.discrs.set! i discr }
+
 /-- Elaborate the given argument with the given expected type. -/
 private def elabArg (arg : Arg) (argExpectedType : Expr) : M Expr := do
  match arg with
@@ -1005,13 +904,18 @@ partial def main : M Expr := do
        mkImplicitArg binderType binderInfo
    setMotive motive
    addArgAndContinue motive
-  else if (← read).elimInfo.majorsPos.contains idx then
+  else if let some tidx := (← read).elimInfo.targetsPos.indexOf? idx then
    match (← getNextArg? binderName binderInfo) with
-    | .some arg => let discr ← elabArg arg binderType; addArgAndContinue discr
+    | .some arg => let discr ← elabArg arg binderType; addDiscr tidx discr; addArgAndContinue discr
    | .undef => finalize
-    | .none => let discr ← mkImplicitArg binderType binderInfo; addArgAndContinue discr
+    | .none => let discr ← mkImplicitArg binderType binderInfo; addDiscr tidx discr; addArgAndContinue discr
  else match (← getNextArg? binderName binderInfo) with
-    | .some (.stx stx) => addArgAndContinue (← postponeElabTerm stx binderType)
+    | .some (.stx stx) =>
+      if (← read).extraArgsPos.contains idx then
+        let arg ← elabArg (.stx stx) binderType
+        addArgAndContinue arg
+      else
+        addArgAndContinue (← postponeElabTerm stx binderType)
    | .some (.expr val) => addArgAndContinue (← ensureArgType (← get).f val binderType)
    | .undef => finalize
    | .none => addArgAndContinue (← mkImplicitArg binderType binderInfo)
@@ -1065,10 +969,13 @@ def elabAppArgs (f : Expr) (namedArgs : Array NamedArg) (args : Array Arg)
    let some expectedType := expectedType? | throwError "failed to elaborate eliminator, expected type is not available"
    let expectedType ← instantiateMVars expectedType
    if expectedType.getAppFn.isMVar then throwError "failed to elaborate eliminator, expected type is not available"
-    ElabElim.main.run { elimInfo, expectedType } |>.run' {
+    let extraArgsPos ← getElabAsElimExtraArgsPos elimInfo
+    trace[Elab.app.elab_as_elim] "extraArgsPos: {extraArgsPos}"
+    ElabElim.main.run { elimInfo, expectedType, extraArgsPos } |>.run' {
      f, fType
      args := args.toList
      namedArgs := namedArgs.toList
+      discrs := mkArray elimInfo.targetsPos.size none
    }
  else
    ElabAppArgs.main.run { explicit, ellipsis, resultIsOutParamSupport } |>.run' {
@@ -1079,12 +986,12 @@ def elabAppArgs (f : Expr) (namedArgs : Array NamedArg) (args : Array Arg)
    }
 where
  /-- Return `some info` if we should elaborate as an eliminator. -/
-  elabAsElim? : TermElabM (Option ElabElimInfo) := do
+  elabAsElim? : TermElabM (Option ElimInfo) := do
    unless (← read).heedElabAsElim do return none
    if explicit || ellipsis then return none
    let .const declName _ := f | return none
    unless (← shouldElabAsElim declName) do return none
-    let elimInfo ← getElabElimInfo declName
+    let elimInfo ← getElimInfo declName
    forallTelescopeReducing (← inferType f) fun xs _ => do
      /- Process arguments similar to `Lean.Elab.Term.ElabElim.main` to see if the motive has been
         provided, in which case we use the standard app elaborator.
@@ -1115,20 +1022,47 @@ where
            return none
        | _, _ => return some elimInfo

+  /--
+  Collect extra argument positions that must be elaborated eagerly when using `elab_as_elim`.
+  The idea is that they contribute to motive inference. See comment at `ElamElim.Context.extraArgsPos`.
+  -/
+  getElabAsElimExtraArgsPos (elimInfo : ElimInfo) : MetaM (Array Nat) := do
+    forallTelescope elimInfo.elimType fun xs type => do
+      let targets := type.getAppArgs
+      /- Compute transitive closure of fvars appearing in the motive and the targets. -/
+      let initMotiveFVars : CollectFVars.State := targets.foldl (init := {}) collectFVars
+      let motiveFVars ← xs.size.foldRevM (init := initMotiveFVars) fun i s => do
+        let x := xs[i]!
+        if elimInfo.motivePos == i || elimInfo.targetsPos.contains i || s.fvarSet.contains x.fvarId! then
+          return collectFVars s (← inferType x)
+        else
+          return s
+      /- Collect the extra argument positions -/
+      let mut extraArgsPos := #[]
+      for i in [:xs.size] do
+        let x := xs[i]!
+        unless elimInfo.motivePos == i || elimInfo.targetsPos.contains i do
+          let xType ← x.fvarId!.getType
+          /- We only consider "first-order" types because we can reliably "extract" information from them. -/
+          if motiveFVars.fvarSet.contains x.fvarId!
+             || (isFirstOrder xType
+                 && Option.isSome (xType.find? fun e => e.isFVar && motiveFVars.fvarSet.contains e.fvarId!)) then
+            extraArgsPos := extraArgsPos.push i
+      return extraArgsPos
+
+  /-
+  Helper function for implementing `elab_as_elim`.
+  We say a term is "first-order" if all applications are of the form `f ...` where `f` is a constant.
+  -/
+  isFirstOrder (e : Expr) : Bool :=
+    Option.isNone <| e.find? fun e =>
+      e.isApp && !e.getAppFn.isConst

 /-- Auxiliary inductive datatype that represents the resolution of an `LVal`. -/
 inductive LValResolution where
-  /-- When applied to `f`, effectively expands to `BaseStruct.fieldName (self := Struct.toBase f)`.
-  This is a special named argument where it suppresses any explicit arguments depending on it so that type parameters don't need to be supplied. -/
  | projFn   (baseStructName : Name) (structName : Name) (fieldName : Name)
-  /-- Similar to `projFn`, but for extracting field indexed by `idx`. Works for structure-like inductive types in general. -/
  | projIdx  (structName : Name) (idx : Nat)
-  /-- When applied to `f`, effectively expands to `constName ... (Struct.toBase f)`, with the argument placed in the correct
-  positional argument if possible, or otherwise as a named argument. The `Struct.toBase` is not present if `baseStructName == structName`,
-  in which case these do not need to be structures. Supports generalized field notation. -/
  | const    (baseStructName : Name) (structName : Name) (constName : Name)
-  /-- Like `const`, but with `fvar` instead of `constName`.
-  The `fullName` is the name of the recursive function, and `baseName` is the base name of the type to search for in the parameter list. -/
  | localRec (baseName : Name) (fullName : Name) (fvar : Expr)

 private def throwLValError (e : Expr) (eType : Expr) (msg : MessageData) : TermElabM α :=
@@ -1287,7 +1221,7 @@ private partial def mkBaseProjections (baseStructName : Name) (structName : Name
    let mut e := e
    for projFunName in path do
      let projFn ← mkConst projFunName
-      e ← elabAppArgs projFn #[{ name := `self, val := Arg.expr e, suppressDeps := true }] (args := #[]) (expectedType? := none) (explicit := false) (ellipsis := false)
+      e ← elabAppArgs projFn #[{ name := `self, val := Arg.expr e }] (args := #[]) (expectedType? := none) (explicit := false) (ellipsis := false)
    return e

 private def typeMatchesBaseName (type : Expr) (baseName : Name) : MetaM Bool := do
@@ -1298,70 +1232,45 @@ private def typeMatchesBaseName (type : Expr) (baseName : Name) : MetaM Bool :=
  else
    return (← whnfR type).isAppOf baseName

-/--
-Auxiliary method for field notation. Tries to add `e` as a new argument to `args` or `namedArgs`.
-This method first finds the parameter with a type of the form `(baseName ...)`.
-When the parameter is found, if it an explicit one and `args` is big enough, we add `e` to `args`.
-Otherwise, if there isn't another parameter with the same name, we add `e` to `namedArgs`.
+/-- Auxiliary method for field notation. It tries to add `e` as a new argument to `args` or `namedArgs`.
+   This method first finds the parameter with a type of the form `(baseName ...)`.
+   When the parameter is found, if it an explicit one and `args` is big enough, we add `e` to `args`.
+   Otherwise, if there isn't another parameter with the same name, we add `e` to `namedArgs`.

-Remark: `fullName` is the name of the resolved "field" access function. It is used for reporting errors
-/
-private partial def addLValArg (baseName : Name) (fullName : Name) (e : Expr) (args : Array Arg) (namedArgs : Array NamedArg) (f : Expr) :
-    MetaM (Array Arg × Array NamedArg) := do
-  withoutModifyingState <| go f (← inferType f) 0 namedArgs (namedArgs.map (·.name)) true
-where
-  /--
-  * `argIdx` is the position into `args` for the next place an explicit argument can be inserted.
-  * `remainingNamedArgs` keeps track of named arguments that haven't been visited yet,
-    for handling the case where multiple parameters have the same name.
-  * `unusableNamedArgs` keeps track of names that can't be used as named arguments. This is initialized with user-provided named arguments.
-  * `allowNamed` is whether or not to allow using named arguments.
-    Disabled after using `CoeFun` since those parameter names unlikely to be meaningful,
-    and otherwise whether dot notation works or not could feel random.
-  -/
-  go (f fType : Expr) (argIdx : Nat) (remainingNamedArgs : Array NamedArg) (unusableNamedArgs : Array Name) (allowNamed : Bool) := withIncRecDepth do
-    /- Use metavariables (rather than `forallTelescope`) to prevent `coerceToFunction?` from succeeding when multiple instances could apply -/
-    let (xs, bInfos, fType') ← forallMetaTelescope fType
-    let mut argIdx := argIdx
-    let mut remainingNamedArgs := remainingNamedArgs
-    let mut unusableNamedArgs := unusableNamedArgs
-    for x in xs, bInfo in bInfos do
-      let xDecl ← x.mvarId!.getDecl
-      if let some idx := remainingNamedArgs.findIdx? (·.name == xDecl.userName) then
-        /- If there is named argument with name `xDecl.userName`, then it is accounted for and we can't make use of it. -/
+   Remark: `fullName` is the name of the resolved "field" access function. It is used for reporting errors -/
+private def addLValArg (baseName : Name) (fullName : Name) (e : Expr) (args : Array Arg) (namedArgs : Array NamedArg) (fType : Expr)
+    : TermElabM (Array Arg × Array NamedArg) :=
+  forallTelescopeReducing fType fun xs _ => do
+    let mut argIdx := 0 -- position of the next explicit argument
+    let mut remainingNamedArgs := namedArgs
+    for i in [:xs.size] do
+      let x := xs[i]!
+      let xDecl ← x.fvarId!.getDecl
+      /- If there is named argument with name `xDecl.userName`, then we skip it. -/
+      match remainingNamedArgs.findIdx? (fun namedArg => namedArg.name == xDecl.userName) with
+      | some idx =>
        remainingNamedArgs := remainingNamedArgs.eraseIdx idx
-      else
-        if (← typeMatchesBaseName xDecl.type baseName) then
+      | none =>
+        let type := xDecl.type
+        if (← typeMatchesBaseName type baseName) then
          /- We found a type of the form (baseName ...).
             First, we check if the current argument is an explicit one,
-             and if the current explicit position "fits" at `args` (i.e., it must be ≤ arg.size) -/
-          if argIdx ≤ args.size && bInfo.isExplicit then
-            /- We can insert `e` as an explicit argument -/
+             and the current explicit position "fits" at `args` (i.e., it must be ≤ arg.size) -/
+          if argIdx ≤ args.size && xDecl.binderInfo.isExplicit then
+            /- We insert `e` as an explicit argument -/
            return (args.insertAt! argIdx (Arg.expr e), namedArgs)
-          else
-            /- If we can't add `e` to `args`, we try to add it using a named argument, but this is only possible
-               if there isn't an argument with the same name occurring before it. -/
-            if !allowNamed || unusableNamedArgs.contains xDecl.userName then
-              throwError "\
-                invalid field notation, function '{fullName}' has argument with the expected type\
-                {indentExpr xDecl.type}\n\
-                but it cannot be used"
-            else
-              return (args, namedArgs.push { name := xDecl.userName, val := Arg.expr e })
-        /- Advance `argIdx` and update seen named arguments. -/
-        if bInfo.isExplicit then
+          /- If we can't add `e` to `args`, we try to add it using a named argument, but this is only possible
+             if there isn't an argument with the same name occurring before it. -/
+          for j in [:i] do
+            let prev := xs[j]!
+            let prevDecl ← prev.fvarId!.getDecl
+            if prevDecl.userName == xDecl.userName then
+              throwError "invalid field notation, function '{fullName}' has argument with the expected type{indentExpr type}\nbut it cannot be used"
+          return (args, namedArgs.push { name := xDecl.userName, val := Arg.expr e })
+        if xDecl.binderInfo.isExplicit then
+          -- advance explicit argument position
          argIdx := argIdx + 1
-        unusableNamedArgs := unusableNamedArgs.push xDecl.userName
-    /- If named arguments aren't allowed, then it must still be possible to pass the value as an explicit argument.
-       Otherwise, we can abort now. -/
-    if allowNamed || argIdx ≤ args.size then
-      if let fType'@(.forallE ..) ← whnf fType' then
-        return ← go (mkAppN f xs) fType' argIdx remainingNamedArgs unusableNamedArgs allowNamed
-      if let some f' ← coerceToFunction? (mkAppN f xs) then
-        return ← go f' (← inferType f') argIdx remainingNamedArgs unusableNamedArgs false
-    throwError "\
-      invalid field notation, function '{fullName}' does not have argument with type ({baseName} ...) that can be used, \
-      it must be explicit or implicit with a unique name"
+    throwError "invalid field notation, function '{fullName}' does not have argument with type ({baseName} ...) that can be used, it must be explicit or implicit with a unique name"

 /-- Adds the `TermInfo` for the field of a projection. See `Lean.Parser.Term.identProjKind`. -/
 private def addProjTermInfo
@@ -1396,10 +1305,10 @@ private def elabAppLValsAux (namedArgs : Array NamedArg) (args : Array Arg) (exp
        let projFn ← mkConst info.projFn
        let projFn ← addProjTermInfo lval.getRef projFn
        if lvals.isEmpty then
-          let namedArgs ← addNamedArg namedArgs { name := `self, val := Arg.expr f, suppressDeps := true }
+          let namedArgs ← addNamedArg namedArgs { name := `self, val := Arg.expr f }
          elabAppArgs projFn namedArgs args expectedType? explicit ellipsis
        else
-          let f ← elabAppArgs projFn #[{ name := `self, val := Arg.expr f, suppressDeps := true }] #[] (expectedType? := none) (explicit := false) (ellipsis := false)
+          let f ← elabAppArgs projFn #[{ name := `self, val := Arg.expr f }] #[] (expectedType? := none) (explicit := false) (ellipsis := false)
          loop f lvals
      else
        unreachable!
@@ -1408,7 +1317,8 @@ private def elabAppLValsAux (namedArgs : Array NamedArg) (args : Array Arg) (exp
      let projFn ← mkConst constName
      let projFn ← addProjTermInfo lval.getRef projFn
      if lvals.isEmpty then
-        let (args, namedArgs) ← addLValArg baseStructName constName f args namedArgs projFn
+        let projFnType ← inferType projFn
+        let (args, namedArgs) ← addLValArg baseStructName constName f args namedArgs projFnType
        elabAppArgs projFn namedArgs args expectedType? explicit ellipsis
      else
        let f ← elabAppArgs projFn #[] #[Arg.expr f] (expectedType? := none) (explicit := false) (ellipsis := false)
@@ -1416,7 +1326,8 @@ private def elabAppLValsAux (namedArgs : Array NamedArg) (args : Array Arg) (exp
    | LValResolution.localRec baseName fullName fvar =>
      let fvar ← addProjTermInfo lval.getRef fvar
      if lvals.isEmpty then
-        let (args, namedArgs) ← addLValArg baseName fullName f args namedArgs fvar
+        let fvarType ← inferType fvar
+        let (args, namedArgs) ← addLValArg baseName fullName f args namedArgs fvarType
        elabAppArgs fvar namedArgs args expectedType? explicit ellipsis
      else
        let f ← elabAppArgs fvar #[] #[Arg.expr f] (expectedType? := none) (explicit := false) (ellipsis := false)
@@ -1425,6 +1336,8 @@ private def elabAppLValsAux (namedArgs : Array NamedArg) (args : Array Arg) (exp

 private def elabAppLVals (f : Expr) (lvals : List LVal) (namedArgs : Array NamedArg) (args : Array Arg)
    (expectedType? : Option Expr) (explicit ellipsis : Bool) : TermElabM Expr := do
+  if !lvals.isEmpty && explicit then
+    throwError "invalid use of field notation with `@` modifier"
  elabAppLValsAux namedArgs args expectedType? explicit ellipsis f lvals

 def elabExplicitUnivs (lvls : Array Syntax) : TermElabM (List Level) := do
@@ -1523,21 +1436,19 @@ private partial def elabAppFn (f : Syntax) (lvals : List LVal) (namedArgs : Arra
    withReader (fun ctx => { ctx with errToSorry := false }) do
      f.getArgs.foldlM (init := acc) fun acc f => elabAppFn f lvals namedArgs args expectedType? explicit ellipsis true acc
  else
-    let elabFieldName (e field : Syntax) (explicit : Bool) := do
+    let elabFieldName (e field : Syntax) := do
      let newLVals := field.identComponents.map fun comp =>
        -- We use `none` in `suffix?` since `field` can't be part of a composite name
        LVal.fieldName comp comp.getId.getString! none f
      elabAppFn e (newLVals ++ lvals) namedArgs args expectedType? explicit ellipsis overloaded acc
-    let elabFieldIdx (e idxStx : Syntax) (explicit : Bool) := do
+    let elabFieldIdx (e idxStx : Syntax) := do
      let some idx := idxStx.isFieldIdx? | throwError "invalid field index"
      elabAppFn e (LVal.fieldIdx idxStx idx :: lvals) namedArgs args expectedType? explicit ellipsis overloaded acc
    match f with
-    | `($(e).$idx:fieldIdx) => elabFieldIdx e idx explicit
-    | `($e |>.$idx:fieldIdx) => elabFieldIdx e idx explicit
-    | `($(e).$field:ident) => elabFieldName e field explicit
-    | `($e |>.$field:ident) => elabFieldName e field explicit
-    | `(@$(e).$idx:fieldIdx) => elabFieldIdx e idx (explicit := true)
-    | `(@$(e).$field:ident) => elabFieldName e field (explicit := true)
+    | `($(e).$idx:fieldIdx) => elabFieldIdx e idx
+    | `($e |>.$idx:fieldIdx) => elabFieldIdx e idx
+    | `($(e).$field:ident) => elabFieldName e field
+    | `($e |>.$field:ident) => elabFieldName e field
    | `($_:ident@$_:term) =>
      throwError "unexpected occurrence of named pattern"
    | `($id:ident) => do
@@ -1694,10 +1605,8 @@ private def elabAtom : TermElab := fun stx expectedType? => do

@[builtin_term_elab explicit] def elabExplicit : TermElab := fun stx expectedType? =>
  match stx with
-  | `(@$_:ident)          => elabAtom stx expectedType?  -- Recall that `elabApp` also has support for `@`
+  | `(@$_:ident)         => elabAtom stx expectedType?  -- Recall that `elabApp` also has support for `@`
  | `(@$_:ident.{$_us,*}) => elabAtom stx expectedType?
-  | `(@$(_).$_:fieldIdx)  => elabAtom stx expectedType?
-  | `(@$(_).$_:ident)     => elabAtom stx expectedType?
  | `(@($t))             => elabTerm t expectedType? (implicitLambda := false)    -- `@` is being used just to disable implicit lambdas
  | `(@$t)               => elabTerm t expectedType? (implicitLambda := false)   -- `@` is being used just to disable implicit lambdas
  | _                    => throwUnsupportedSyntax
--- a/src/Lean/Elab/Arg.lean
+++ b/src/Lean/Elab/Arg.lean
@@ -9,22 +9,18 @@ import Lean.Elab.Term
 namespace Lean.Elab.Term

 /--
-Auxiliary inductive datatype for combining unelaborated syntax
-and already elaborated expressions. It is used to elaborate applications.
-/
+  Auxiliary inductive datatype for combining unelaborated syntax
+  and already elaborated expressions. It is used to elaborate applications. -/
 inductive Arg where
  | stx  (val : Syntax)
  | expr (val : Expr)
  deriving Inhabited

-/-- Named arguments created using the notation `(x := val)`. -/
+/-- Named arguments created using the notation `(x := val)` -/
 structure NamedArg where
  ref  : Syntax := Syntax.missing
  name : Name
  val  : Arg
-  /-- If `true`, then make all parameters that depend on this one become implicit.
-  This is used for projection notation, since structure parameters might be explicit for classes. -/
-  suppressDeps : Bool := false
  deriving Inhabited

 /--
--- a/src/Lean/Elab/BuiltinCommand.lean
+++ b/src/Lean/Elab/BuiltinCommand.lean
@@ -311,6 +311,167 @@ def failIfSucceeds (x : CommandElabM Unit) : CommandElabM Unit := do
    failIfSucceeds <| elabCheckCore (ignoreStuckTC := false) (← `(#check $term))
  | _ => throwUnsupportedSyntax

+private def mkEvalInstCore (evalClassName : Name) (e : Expr) : MetaM Expr := do
+  let α    ← inferType e
+  let u    ← getDecLevel α
+  let inst := mkApp (Lean.mkConst evalClassName [u]) α
+  try
+    synthInstance inst
+  catch _ =>
+    -- Put `α` in WHNF and try again
+    try
+      let α ← whnf α
+      synthInstance (mkApp (Lean.mkConst evalClassName [u]) α)
+    catch _ =>
+      -- Fully reduce `α` and try again
+      try
+        let α ← reduce (skipTypes := false) α
+        synthInstance (mkApp (Lean.mkConst evalClassName [u]) α)
+      catch _ =>
+        throwError "expression{indentExpr e}\nhas type{indentExpr α}\nbut instance{indentExpr inst}\nfailed to be synthesized, this instance instructs Lean on how to display the resulting value, recall that any type implementing the `Repr` class also implements the `{evalClassName}` class"
+
+private def mkRunMetaEval (e : Expr) : MetaM Expr :=
+  withLocalDeclD `env (mkConst ``Lean.Environment) fun env =>
+  withLocalDeclD `opts (mkConst ``Lean.Options) fun opts => do
+    let α ← inferType e
+    let u ← getDecLevel α
+    let instVal ← mkEvalInstCore ``Lean.MetaEval e
+    let e := mkAppN (mkConst ``Lean.runMetaEval [u]) #[α, instVal, env, opts, e]
+    instantiateMVars (← mkLambdaFVars #[env, opts] e)
+
+private def mkRunEval (e : Expr) : MetaM Expr := do
+  let α ← inferType e
+  let u ← getDecLevel α
+  let instVal ← mkEvalInstCore ``Lean.Eval e
+  instantiateMVars (mkAppN (mkConst ``Lean.runEval [u]) #[α, instVal, mkSimpleThunk e])
+
+unsafe def elabEvalCoreUnsafe (bang : Bool) (tk term : Syntax): CommandElabM Unit := do
+    let declName := `_eval
+    let addAndCompile (value : Expr) : TermElabM Unit := do
+      let value ← Term.levelMVarToParam (← instantiateMVars value)
+      let type ← inferType value
+      let us := collectLevelParams {} value |>.params
+      let value ← instantiateMVars value
+      let decl := Declaration.defnDecl {
+        name        := declName
+        levelParams := us.toList
+        type        := type
+        value       := value
+        hints       := ReducibilityHints.opaque
+        safety      := DefinitionSafety.unsafe
+      }
+      Term.ensureNoUnassignedMVars decl
+      addAndCompile decl
+    -- Check for sorry axioms
+    let checkSorry (declName : Name) : MetaM Unit := do
+      unless bang do
+        let axioms ← collectAxioms declName
+        if axioms.contains ``sorryAx then
+          throwError ("cannot evaluate expression that depends on the `sorry` axiom.\nUse `#eval!` to " ++
+            "evaluate nevertheless (which may cause lean to crash).")
+    -- Elaborate `term`
+    let elabEvalTerm : TermElabM Expr := do
+      let e ← Term.elabTerm term none
+      Term.synthesizeSyntheticMVarsNoPostponing
+      if (← Term.logUnassignedUsingErrorInfos (← getMVars e)) then throwAbortTerm
+      if (← isProp e) then
+        mkDecide e
+      else
+        return e
+    -- Evaluate using term using `MetaEval` class.
+    let elabMetaEval : CommandElabM Unit := do
+      -- Generate an action without executing it. We use `withoutModifyingEnv` to ensure
+      -- we don't pollute the environment with auxliary declarations.
+      -- We have special support for `CommandElabM` to ensure `#eval` can be used to execute commands
+      -- that modify `CommandElabM` state not just the `Environment`.
+      let act : Sum (CommandElabM Unit) (Environment → Options → IO (String × Except IO.Error Environment)) ←
+        runTermElabM fun _ => Term.withDeclName declName do withoutModifyingEnv do
+          let e ← elabEvalTerm
+          let eType ← instantiateMVars (← inferType e)
+          if eType.isAppOfArity ``CommandElabM 1 then
+            let mut stx ← Term.exprToSyntax e
+            unless (← isDefEq eType.appArg! (mkConst ``Unit)) do
+              stx ← `($stx >>= fun v => IO.println (repr v))
+            let act ← Lean.Elab.Term.evalTerm (CommandElabM Unit) (mkApp (mkConst ``CommandElabM) (mkConst ``Unit)) stx
+            pure <| Sum.inl act
+          else
+            let e ← mkRunMetaEval e
+            addAndCompile e
+            checkSorry declName
+            let act ← evalConst (Environment → Options → IO (String × Except IO.Error Environment)) declName
+            pure <| Sum.inr act
+      match act with
+      | .inl act => act
+      | .inr act =>
+        let (out, res) ← act (← getEnv) (← getOptions)
+        logInfoAt tk out
+        match res with
+        | Except.error e => throwError e.toString
+        | Except.ok env  => setEnv env; pure ()
+    -- Evaluate using term using `Eval` class.
+    let elabEval : CommandElabM Unit := runTermElabM fun _ => Term.withDeclName declName do withoutModifyingEnv do
+      -- fall back to non-meta eval if MetaEval hasn't been defined yet
+      -- modify e to `runEval e`
+      let e ← mkRunEval (← elabEvalTerm)
+      addAndCompile e
+      checkSorry declName
+      let act ← evalConst (IO (String × Except IO.Error Unit)) declName
+      let (out, res) ← liftM (m := IO) act
+      logInfoAt tk out
+      match res with
+      | Except.error e => throwError e.toString
+      | Except.ok _    => pure ()
+    if (← getEnv).contains ``Lean.MetaEval then do
+      elabMetaEval
+    else
+      elabEval
+
+@[implemented_by elabEvalCoreUnsafe]
+opaque elabEvalCore (bang : Bool) (tk term : Syntax): CommandElabM Unit
+
+@[builtin_command_elab «eval»]
+def elabEval : CommandElab
+  | `(#eval%$tk $term) => elabEvalCore false tk term
+  | _ => throwUnsupportedSyntax
+
+@[builtin_command_elab evalBang]
+def elabEvalBang : CommandElab
+  | `(Parser.Command.evalBang|#eval!%$tk $term) => elabEvalCore true tk term
+  | _ => throwUnsupportedSyntax
+
+private def checkImportsForRunCmds : CommandElabM Unit := do
+  unless (← getEnv).contains ``CommandElabM do
+    throwError "to use this command, include `import Lean.Elab.Command`"
+
+@[builtin_command_elab runCmd]
+def elabRunCmd : CommandElab
+  | `(run_cmd $elems:doSeq) => do
+    checkImportsForRunCmds
+    (← liftTermElabM <| Term.withDeclName `_run_cmd <|
+      unsafe Term.evalTerm (CommandElabM Unit)
+        (mkApp (mkConst ``CommandElabM) (mkConst ``Unit))
+        (← `(discard do $elems)))
+  | _ => throwUnsupportedSyntax
+
+@[builtin_command_elab runElab]
+def elabRunElab : CommandElab
+  | `(run_elab $elems:doSeq) => do
+    checkImportsForRunCmds
+    (← liftTermElabM <| Term.withDeclName `_run_elab <|
+      unsafe Term.evalTerm (CommandElabM Unit)
+        (mkApp (mkConst ``CommandElabM) (mkConst ``Unit))
+        (← `(Command.liftTermElabM <| discard do $elems)))
+  | _ => throwUnsupportedSyntax
+
+@[builtin_command_elab runMeta]
+def elabRunMeta : CommandElab := fun stx =>
+  match stx with
+  | `(run_meta $elems:doSeq) => do
+     checkImportsForRunCmds
+     let stxNew ← `(command| run_elab (show Lean.Meta.MetaM Unit from do $elems))
+     withMacroExpansion stx stxNew do elabCommand stxNew
+  | _ => throwUnsupportedSyntax
+
@[builtin_command_elab «synth»] def elabSynth : CommandElab := fun stx => do
  let term := stx[1]
  withoutModifyingEnv <| runTermElabM fun _ => Term.withDeclName `_synth_cmd do
--- a/src/Lean/Elab/BuiltinEvalCommand.lean
+++ b/src/Lean/Elab/BuiltinEvalCommand.lean
@@ -1,277 +0,0 @@
-/-
-Copyright (c) 2024 Lean FRO, LLC. All rights reserved.
-Released under Apache 2.0 license as described in the file LICENSE.
-Authors: Kyle Miller
-/
-prelude
-import Lean.Util.CollectAxioms
-import Lean.Elab.Deriving.Basic
-import Lean.Elab.MutualDef
-
-/-!
-# Implementation of `#eval` command
-/
-
-namespace Lean.Elab.Command
-open Meta
-
-register_builtin_option eval.pp : Bool := {
-  defValue := true
-  descr    := "('#eval' command) enables using 'ToExpr' instances to pretty print the result, \
-               otherwise uses 'Repr' or 'ToString' instances"
-}
-
-register_builtin_option eval.type : Bool := {
-  defValue := false -- TODO: set to 'true'
-  descr    := "('#eval' command) enables pretty printing the type of the result"
-}
-
-register_builtin_option eval.derive.repr : Bool := {
-  defValue := true
-  descr    := "('#eval' command) enables auto-deriving 'Repr' instances as a fallback"
-}
-
-builtin_initialize
-  registerTraceClass `Elab.eval
-
-/--
-Elaborates the term, ensuring the result has no expression metavariables.
-If there would be unsolved-for metavariables, tries hinting that the resulting type
-is a monadic value with the `CommandElabM`, `TermElabM`, or `IO` monads.
-Throws errors if the term is a proof or a type, but lifts props to `Bool` using `mkDecide`.
-/
-private def elabTermForEval (term : Syntax) (expectedType? : Option Expr) : TermElabM Expr := do
-  let ty ← expectedType?.getDM mkFreshTypeMVar
-  let e ← Term.elabTermEnsuringType term ty
-  synthesizeWithHinting ty
-  let e ← instantiateMVars e
-  if (← Term.logUnassignedUsingErrorInfos (← getMVars e)) then throwAbortTerm
-  if ← isProof e then
-    throwError m!"cannot evaluate, proofs are not computationally relevant"
-  let e ← if (← isProp e) then mkDecide e else pure e
-  if ← isType e then
-    throwError m!"cannot evaluate, types are not computationally relevant"
-  trace[Elab.eval] "elaborated term:{indentExpr e}"
-  return e
-where
-  /-- Try different strategies to make `Term.synthesizeSyntheticMVarsNoPostponing` succeed. -/
-  synthesizeWithHinting (ty : Expr) : TermElabM Unit := do
-    Term.synthesizeSyntheticMVarsUsingDefault
-    let s ← saveState
-    try
-      Term.synthesizeSyntheticMVarsNoPostponing
-    catch ex =>
-      let exS ← saveState
-      -- Try hinting that `ty` is a monad application.
-      for m in #[``CommandElabM, ``TermElabM, ``IO] do
-        s.restore true
-        try
-          if ← isDefEq ty (← mkFreshMonadApp m) then
-            Term.synthesizeSyntheticMVarsNoPostponing
-            return
-        catch _ => pure ()
-      -- None of the hints worked, so throw the original error.
-      exS.restore true
-      throw ex
-  mkFreshMonadApp (n : Name) : MetaM Expr := do
-    let m ← mkConstWithFreshMVarLevels n
-    let (args, _, _) ← forallMetaBoundedTelescope (← inferType m) 1
-    return mkAppN m args
-
-private def addAndCompileExprForEval (declName : Name) (value : Expr) (allowSorry := false) : TermElabM Unit := do
-  -- Use the `elabMutualDef` machinery to be able to support `let rec`.
-  -- Hack: since we are using the `TermElabM` version, we can insert the `value` as a metavariable via `exprToSyntax`.
-  -- An alternative design would be to make `elabTermForEval` into a term elaborator and elaborate the command all at once
-  -- with `unsafe def _eval := term_for_eval% $t`, which we did try, but unwanted error messages
-  -- such as "failed to infer definition type" can surface.
-  let defView := mkDefViewOfDef { isUnsafe := true }
-    (← `(Parser.Command.definition|
-          def $(mkIdent <| `_root_ ++ declName) := $(← Term.exprToSyntax value)))
-  Term.elabMutualDef #[] { header := "" } #[defView]
-  unless allowSorry do
-    let axioms ← collectAxioms declName
-    if axioms.contains ``sorryAx then
-      throwError "\
-        aborting evaluation since the expression depends on the 'sorry' axiom, \
-        which can lead to runtime instability and crashes.\n\n\
-        To attempt to evaluate anyway despite the risks, use the '#eval!' command."
-
-/--
-Try to make a `@projFn ty inst e` application, even if it takes unfolding the type `ty` of `e` to synthesize the instance `inst`.
-/
-private partial def mkDeltaInstProj (inst projFn : Name) (e : Expr) (ty? : Option Expr := none) (tryReduce : Bool := true) : MetaM Expr := do
-  let ty ← ty?.getDM (inferType e)
-  if let .some inst ← trySynthInstance (← mkAppM inst #[ty]) then
-    mkAppOptM projFn #[ty, inst, e]
-  else
-    let ty ← whnfCore ty
-    let some ty ← unfoldDefinition? ty
-      | guard tryReduce
-        -- Reducing the type is a strategy `#eval` used before the refactor of #5627.
-        -- The test lean/run/hlistOverload.lean depends on it, so we preserve the behavior.
-        let ty ← reduce (skipTypes := false) ty
-        mkDeltaInstProj inst projFn e ty (tryReduce := false)
-    mkDeltaInstProj inst projFn e ty tryReduce
-
-/-- Try to make a `toString e` application, even if it takes unfolding the type of `e` to find a `ToString` instance. -/
-private def mkToString (e : Expr) (ty? : Option Expr := none) : MetaM Expr := do
-  mkDeltaInstProj ``ToString ``toString e ty?
-
-/-- Try to make a `repr e` application, even if it takes unfolding the type of `e` to find a `Repr` instance. -/
-private def mkRepr (e : Expr) (ty? : Option Expr := none) : MetaM Expr := do
-  mkDeltaInstProj ``Repr ``repr e ty?
-
-/-- Try to make a `toExpr e` application, even if it takes unfolding the type of `e` to find a `ToExpr` instance. -/
-private def mkToExpr (e : Expr) (ty? : Option Expr := none) : MetaM Expr := do
-  mkDeltaInstProj ``ToExpr ``toExpr e ty?
-
-/--
-Returns a representation of `e` using `Format`, or else fails.
-If the `eval.derive.repr` option is true, then tries automatically deriving a `Repr` instance first.
-Currently auto-derivation does not attempt to derive recursively.
-/
-private def mkFormat (e : Expr) : MetaM Expr := do
-  mkRepr e <|> (do mkAppM ``Std.Format.text #[← mkToString e])
-  <|> do
-    if eval.derive.repr.get (← getOptions) then
-      if let .const name _ := (← whnf (← inferType e)).getAppFn then
-        try
-          trace[Elab.eval] "Attempting to derive a 'Repr' instance for '{MessageData.ofConstName name}'"
-          liftCommandElabM do applyDerivingHandlers ``Repr #[name] none
-          resetSynthInstanceCache
-          return ← mkRepr e
-        catch ex =>
-          trace[Elab.eval] "Failed to use derived 'Repr' instance. Exception: {ex.toMessageData}"
-    throwError m!"could not synthesize a 'Repr' or 'ToString' instance for type{indentExpr (← inferType e)}"
-
-/--
-Returns a representation of `e` using `MessageData`, or else fails.
-Tries `mkFormat` if a `ToExpr` instance can't be synthesized.
-/
-private def mkMessageData (e : Expr) : MetaM Expr := do
-  (do guard <| eval.pp.get (← getOptions); mkAppM ``MessageData.ofExpr #[← mkToExpr e])
-  <|> (return mkApp (mkConst ``MessageData.ofFormat) (← mkFormat e))
-  <|> do throwError m!"could not synthesize a 'ToExpr', 'Repr', or 'ToString' instance for type{indentExpr (← inferType e)}"
-
-private structure EvalAction where
-  eval : CommandElabM MessageData
-  /-- Whether to print the result of evaluation.
-  If `some`, the expression is what type to use for the type ascription when `pp.type` is true. -/
-  printVal : Option Expr
-
-unsafe def elabEvalCoreUnsafe (bang : Bool) (tk term : Syntax) (expectedType? : Option Expr) : CommandElabM Unit := withRef tk do
-  let declName := `_eval
-  -- `t` is either `MessageData` or `Format`, and `mkT` is for synthesizing an expression that yields a `t`.
-  -- The `toMessageData` function adapts `t` to `MessageData`.
-  let mkAct {t : Type} [Inhabited t] (toMessageData : t → MessageData) (mkT : Expr → MetaM Expr) (e : Expr) : TermElabM EvalAction := do
-    -- Create a monadic action given the name of the monad `mc`, the monad `m` itself,
-    -- and an expression `e` to evaluate in this monad.
-    -- A trick here is that `mkMAct?` makes use of `MonadEval` instances are currently available in this stage,
-    -- and we do not need them to be available in the target environment.
-    let mkMAct? (mc : Name) (m : Type → Type) [Monad m] [MonadEvalT m CommandElabM] (e : Expr) : TermElabM (Option EvalAction) := do
-      let some e ← observing? (mkAppOptM ``MonadEvalT.monadEval #[none, mkConst mc, none, none, e])
-        | return none
-      let eType := e.appFn!.appArg!
-      if ← isDefEq eType (mkConst ``Unit) then
-        addAndCompileExprForEval declName e (allowSorry := bang)
-        let mf : m Unit ← evalConst (m Unit) declName
-        return some { eval := do MonadEvalT.monadEval mf; pure "", printVal := none }
-      else
-        let rf ← withLocalDeclD `x eType fun x => do mkLambdaFVars #[x] (← mkT x)
-        let r ← mkAppM ``Functor.map #[rf, e]
-        addAndCompileExprForEval declName r (allowSorry := bang)
-        let mf : m t ← evalConst (m t) declName
-        return some { eval := toMessageData <$> MonadEvalT.monadEval mf, printVal := some eType }
-    if let some act ← mkMAct? ``CommandElabM CommandElabM e
-                    -- Fallbacks in case we are in the Lean package but don't have `CommandElabM` yet
-                    <||> mkMAct? ``TermElabM TermElabM e <||> mkMAct? ``MetaM MetaM e <||> mkMAct? ``CoreM CoreM e
-                    -- Fallback in case nothing is imported
-                    <||> mkMAct? ``IO IO e then
-      return act
-    else
-      -- Otherwise, assume this is a pure value.
-      -- There is no need to adapt pure values to `CommandElabM`.
-      -- This enables `#eval` to work on pure values even when `CommandElabM` is not available.
-      let r ← try mkT e catch ex => do
-        -- Diagnose whether the value is monadic for a representable value, since it's better to mention `MonadEval` in that case.
-        try
-          let some (m, ty) ← isTypeApp? (← inferType e) | failure
-          guard <| (← isMonad? m).isSome
-          -- Verify that there is a way to form some representation:
-          discard <| withLocalDeclD `x ty fun x => mkT x
-        catch _ =>
-          throw ex
-        throwError m!"unable to synthesize '{MessageData.ofConstName ``MonadEval}' instance \
-          to adapt{indentExpr (← inferType e)}\n\
-          to '{MessageData.ofConstName ``IO}' or '{MessageData.ofConstName ``CommandElabM}'."
-      addAndCompileExprForEval declName r (allowSorry := bang)
-      -- `evalConst` may emit IO, but this is collected by `withIsolatedStreams` below.
-      let r ← toMessageData <$> evalConst t declName
-      return { eval := pure r, printVal := some (← inferType e) }
-  let (output, exOrRes) ← IO.FS.withIsolatedStreams do
-    try
-      -- Generate an action without executing it. We use `withoutModifyingEnv` to ensure
-      -- we don't pollute the environment with auxiliary declarations.
-      let act : EvalAction ← liftTermElabM do Term.withDeclName declName do withoutModifyingEnv do
-        let e ← elabTermForEval term expectedType?
-        -- If there is an elaboration error, don't evaluate!
-        if e.hasSyntheticSorry then throwAbortTerm
-        -- We want `#eval` to work even in the core library, so if `ofFormat` isn't available,
-        -- we fall back on a `Format`-based approach.
-        if (← getEnv).contains ``Lean.MessageData.ofFormat then
-          mkAct id (mkMessageData ·) e
-        else
-          mkAct Lean.MessageData.ofFormat (mkFormat ·) e
-      let res ← act.eval
-      return Sum.inr (res, act.printVal)
-    catch ex =>
-      return Sum.inl ex
-  if !output.isEmpty then logInfoAt tk output
-  match exOrRes with
-  | .inl ex => logException ex
-  | .inr (_, none) => pure ()
-  | .inr (res, some type) =>
-    if eval.type.get (← getOptions) then
-      logInfo m!"{res} : {type}"
-    else
-      logInfo res
-
-@[implemented_by elabEvalCoreUnsafe]
-opaque elabEvalCore (bang : Bool) (tk term : Syntax) (expectedType? : Option Expr) : CommandElabM Unit
-
-@[builtin_command_elab «eval»]
-def elabEval : CommandElab
-  | `(#eval%$tk $term) => elabEvalCore false tk term none
-  | _ => throwUnsupportedSyntax
-
-@[builtin_command_elab evalBang]
-def elabEvalBang : CommandElab
-  | `(#eval!%$tk $term) => elabEvalCore true tk term none
-  | _ => throwUnsupportedSyntax
-
-@[builtin_command_elab runCmd]
-def elabRunCmd : CommandElab
-  | `(run_cmd%$tk $elems:doSeq) => do
-    unless (← getEnv).contains ``CommandElabM do
-      throwError "to use this command, include `import Lean.Elab.Command`"
-    elabEvalCore false tk (← `(discard do $elems)) (mkApp (mkConst ``CommandElabM) (mkConst ``Unit))
-  | _ => throwUnsupportedSyntax
-
-@[builtin_command_elab runElab]
-def elabRunElab : CommandElab
-  | `(run_elab%$tk $elems:doSeq) => do
-    unless (← getEnv).contains ``TermElabM do
-      throwError "to use this command, include `import Lean.Elab.Term`"
-    elabEvalCore false tk (← `(discard do $elems)) (mkApp (mkConst ``TermElabM) (mkConst ``Unit))
-  | _ => throwUnsupportedSyntax
-
-@[builtin_command_elab runMeta]
-def elabRunMeta : CommandElab := fun stx =>
-  match stx with
-  | `(run_meta%$tk $elems:doSeq) => do
-    unless (← getEnv).contains ``MetaM do
-      throwError "to use this command, include `import Lean.Meta.Basic`"
-    elabEvalCore false tk (← `(discard do $elems)) (mkApp (mkConst ``MetaM) (mkConst ``Unit))
-  | _ => throwUnsupportedSyntax
-
-end Lean.Elab.Command
--- a/src/Lean/Elab/BuiltinNotation.lean
+++ b/src/Lean/Elab/BuiltinNotation.lean
@@ -55,8 +55,8 @@ open Meta
            let cinfo ← getConstInfoCtor ctor
            let numExplicitFields ← forallTelescopeReducing cinfo.type fun xs _ => do
              let mut n := 0
-              for h : i in [cinfo.numParams:xs.size] do
-                if (← getFVarLocalDecl xs[i]).binderInfo.isExplicit then
+              for i in [cinfo.numParams:xs.size] do
+                if (← getFVarLocalDecl xs[i]!).binderInfo.isExplicit then
                  n := n + 1
              return n
            let args := args.getElems
--- a/src/Lean/Elab/BuiltinTerm.lean
+++ b/src/Lean/Elab/BuiltinTerm.lean
@@ -103,11 +103,9 @@ private def elabOptLevel (stx : Syntax) : TermElabM Level :=
@[builtin_term_elab Lean.Parser.Term.omission] def elabOmission : TermElab := fun stx expectedType? => do
  logWarning m!"\
    The '⋯' token is used by the pretty printer to indicate omitted terms, and it should not be used directly. \
-    It logs this warning and then elaborates like '_'.\
-    \n\n\
-    The presence of '⋯' in pretty printing output is controlled by the 'pp.maxSteps', 'pp.deepTerms' and 'pp.proofs' options. \
-    These options can be further adjusted using 'pp.deepTerms.threshold' and 'pp.proofs.threshold'. \
-    If this '⋯' was copied from the Infoview, the hover there for the original '⋯' explains which of these options led to the omission."
+    It logs this warning and then elaborates like `_`.\
+    \n\nThe presence of `⋯` in pretty printing output is controlled by the 'pp.deepTerms' and `pp.proofs` options. \
+    These options can be further adjusted using `pp.deepTerms.threshold` and `pp.proofs.threshold`."
  elabHole stx expectedType?

@[builtin_term_elab «letMVar»] def elabLetMVar : TermElab := fun stx expectedType? => do
@@ -152,10 +150,26 @@ private def getMVarFromUserName (ident : Syntax) : MetaM Expr := do
    elabTerm b expectedType?
  | _ => throwUnsupportedSyntax

+private def mkTacticMVar (type : Expr) (tacticCode : Syntax) : TermElabM Expr := do
+  let mvar ← mkFreshExprMVar type MetavarKind.syntheticOpaque
+  let mvarId := mvar.mvarId!
+  let ref ← getRef
+  registerSyntheticMVar ref mvarId <| SyntheticMVarKind.tactic tacticCode (← saveContext)
+  return mvar
+
+register_builtin_option debug.byAsSorry : Bool := {
+  defValue := false
+  group    := "debug"
+  descr    := "replace `by ..` blocks with `sorry` IF the expected type is a proposition"
+}
+
@[builtin_term_elab byTactic] def elabByTactic : TermElab := fun stx expectedType? => do
  match expectedType? with
  | some expectedType =>
-    mkTacticMVar expectedType stx .term
+    if ← pure (debug.byAsSorry.get (← getOptions)) <&&> isProp expectedType then
+      mkSorry expectedType false
+    else
+      mkTacticMVar expectedType stx
  | none =>
    tryPostpone
    throwError ("invalid 'by' tactic, expected type has not been provided")
--- a/src/Lean/Elab/Command.lean
+++ b/src/Lean/Elab/Command.lean
@@ -520,12 +520,8 @@ def elabCommandTopLevel (stx : Syntax) : CommandElabM Unit := withRef stx do pro
    -- recovery more coarse. In particular, If `c` in `set_option ... in $c` fails, the remaining
    -- `end` command of the `in` macro would be skipped and the option would be leaked to the outside!
    elabCommand stx
-    -- Run the linters, unless `#guard_msgs` is present, which is special and runs `elabCommandTopLevel` itself,
-    -- so it is a "super-top-level" command. This is the only command that does this, so we just special case it here
-    -- rather than engineer a general solution.
-    unless (stx.find? (·.isOfKind ``Lean.guardMsgsCmd)).isSome do
-      withLogging do
-        runLinters stx
+    withLogging do
+      runLinters stx
  finally
    -- note the order: first process current messages & info trees, then add back old messages & trees,
    -- then convert new traces to messages
@@ -619,9 +615,6 @@ def liftTermElabM (x : TermElabM α) : CommandElabM α := do
  let ((ea, _), _) ← runCore x
  MonadExcept.ofExcept ea

-instance : MonadEval TermElabM CommandElabM where
-  monadEval := liftTermElabM
-
 /--
 Execute the monadic action `elabFn xs` as a `CommandElabM` monadic action, where `xs` are free variables
 corresponding to all active scoped variables declared using the `variable` command.
@@ -730,12 +723,6 @@ Commands that modify the processing of subsequent commands,
 such as `open` and `namespace` commands,
 only have an effect for the remainder of the `CommandElabM` computation passed here,
 and do not affect subsequent commands.
-
-*Warning:* when using this from `MetaM` monads, the caches are *not* reset.
-If the command defines new instances for example, you should use `Lean.Meta.resetSynthInstanceCache`
-to reset the instance cache.
-While the `modifyEnv` function for `MetaM` clears its caches entirely,
-`liftCommandElabM` has no way to reset these caches.
 -/
 def liftCommandElabM (cmd : CommandElabM α) : CoreM α := do
  let (a, commandState) ←
--- a/Show More
+++ b/Show More
				`@@ -0,0 +1 @@`
				* #4963 [LibUV](https://libuv.org/) is now required to build Lean. This change only affects developers who compile Lean themselves instead of obtaining toolchains via `elan`. We have updated the official build instructions with information on how to obtain LibUV on our supported platforms.