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12052 commits

Author SHA1 Message Date
Leonardo de Moura
cffacf1b10
feat: support local hypotheses in simp [h] for sym => mode (#13042)
This PR extends the `simp` tactic in `sym =>` mode to support local
hypotheses in the extra theorem list.

`simp myVariant [h]` now resolves `h` against the local context first,
falling back to global constants. Local hypotheses are converted to
rewrite rules via `mkTheoremFromExpr`, which applies the `eq_true`/
`eq_false`/`propext` adapter from #13041.

- Add `ExtraTheorem` inductive (`.const` / `.fvar`) for cache keying
- Add `resolveExtraTheorems` that checks the local context before
globals
- Update `addExtraTheorems`, `mkDefaultMethods`, `elabVariant`
signatures

Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
2026-03-22 21:50:31 +00:00
Leonardo de Moura
b858d0fbf2
feat: adapt non-equality theorems in mkTheoremFromDecl (#13041)
This PR extends `mkTheoremFromDecl` and `mkTheoremFromExpr` to handle
theorems whose conclusion is not an equality, enabling `Sym.simp` to use
a broader class of lemmas as rewrite rules.

Adaptations:
- `¬ p` → `p = False` via `eq_false`
- `p ↔ q` → `p = q` via `propext`
- `p` (proposition) → `p = True` via `eq_true`

Conjunctions (`p ∧ q`) are not handled here since the `SymM` E-graph
aggressively splits them via case analysis.

Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
2026-03-22 19:34:37 +00:00
Leonardo de Moura
9a3678935d
feat: add sanity checks to register_sym_simp (#13040)
This PR adds validation to the `register_sym_simp` command:

- Reject duplicate variant names
- Validate `pre`/`post` syntax by elaborating them via `elabSymSimproc`
  in a minimal `GrindTacticM` context, catching unknown theorem names
  and unknown theorem set references at registration time

Adds `withGrindTacticM` helper for running `GrindTacticM` from
`CommandElabM`,
and `validateOptionSimprocSyntax` for optional syntax validation.

Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
2026-03-22 17:41:30 +00:00
Leonardo de Moura
8f6411ad57
feat: add interactive simp tactic for sym => mode (#13039)
This PR adds the `simp` tactic to the `sym =>` interactive mode,
completing
the `Sym.simp` interactive infrastructure.

The `simp` tactic supports:
- `simp` — default variant with `@[sym_simp]` theorem set, `simpControl
>> simpArrowTelescope` pre, `evalGround >> thms.rewrite` post
- `simp myVariant` — named variant registered via `register_sym_simp`
- `simp [thm₁, thm₂]` — default variant with extra rewrite theorems
appended to `post`
- `simp myVariant [thm₁, thm₂]` — named variant with extra theorems

Per-variant persistent caching: each unique (variant name, extra theorem
list)
combination gets its own `Sym.Simp.State` cache, shared across
invocations
within a `sym =>` block. Test 10 verifies cache hits using
`trace.sym.simp.debug.cache`.

Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
2026-03-22 15:55:05 +00:00
Sebastian Ullrich
88b746dd48 feat: unfold and rewrap instances in inferInstanceAs and deriving
This PR adjusts the results of `inferInstanceAs` and the `def` `deriving` handler to conform to recently strengthened restrictions on reducibility. This change ensures that when deriving or inferring an instance for a semireducible type definition, the definition's RHS is not leaked when the instance is reduced at lower than semireducible transparency.

More specifically, given the "source type" and "target type" (the given and expected type for `inferInstanceAs`, the right-hand side and applied left-hand side of the `def` for `deriving`), we synthesize an instance for the source type and then unfold and rewrap its components (fields, nested instances) as necessary to make them compatible with the target type. The individual steps are represented by the following options, which all default to enabled and can be disabled to help with porting:
- `backward.inferInstanceAs.wrap`: master switch for instance adjustment in both `inferInstanceAs` and the default `deriving` handler
- `backward.inferInstanceAs.wrap.reuseSubInstances`: reuse existing instances for the target type for sub-instance fields to avoid non-defeq instance diamonds
- `backward.inferInstanceAs.wrap.instances`: wrap non-reducible instances in auxiliary definitions
- `backward.inferInstanceAs.wrap.data`: wrap data fields in auxiliary definitions (proof fields are always wrapped)

This PR is an extension and rewrite of prior work in Mathlib: https://github.com/leanprover-community/mathlib4/pull/36420

Last(?) part of fix for #9077

🤖 Prepared with Claude Code

# Breaking changes

Proofs that relied on the prior "defeq abuse" of these instance or that depended on their specific structure may need adjustments. As `inferInstanceAs A` now needs to know the source and target types exactly before it can continue, it cannot be used anymore as a synonym for `(inferInstance : A)`, use the latter instead when source and target type are identical.
2026-03-22 13:25:46 +01:00
Leonardo de Moura
13f8ce8492
feat: add register_sym_simp command and SymSimpVariant infrastructure (#13034)
This PR adds the `register_sym_simp` command for declaring named
`Sym.simp`
variants with `pre`/`post` simproc chains and optional config overrides.

```
register_sym_simp myVariant where
  pre  := telescope
  post := ground >> rewrite [thm1, thm2] with self
  maxSteps := 50000
```

- `SymSimpVariant` structure storing `pre?`/`post?` syntax (elaborated
at use
  time in `GrindTacticM`) and `Config` overrides
- `SimpleScopedEnvExtension` for persistent cross-module variant storage
- `register_sym_simp` command syntax with `sym_simp_field` category
- Command elaborator with syntax quotation matching and duplicate field
detection
- `getSymSimpVariant?` lookup function
- `deriving Inhabited` on `Simp.Config` for extension support

Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
2026-03-22 04:30:58 +00:00
Leonardo de Moura
dbfd0d35f2
fix: simp +arith and grind loop on normalized Int equalities (#13033)
This PR adds `r == e` guards to the `norm_eq_var` and
`norm_eq_var_const` branches of `Int.Linear.simpEq?`. Without these
guards, `simpEq?` returns a non-trivial proof for already-normalized
equations like `x = -1`, causing `exists_prop_congr` to fire repeatedly
and build an infinitely growing term.

The existing `Nat.simpCnstrPos?` already had the equivalent guard (`if r
!= lhs then ... else return none`).

Closes #12812

---------

Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>
2026-03-22 04:04:56 +00:00
Leonardo de Moura
e848039ba9
feat: add built-in sym_simproc and sym_discharger elaborators (#13031)
This PR adds the built-in elaborators for the `sym_simproc` and
`sym_discharger` DSL syntax categories introduced in #13026.

Simproc elaborators (`@[builtin_sym_simproc]`):
- `ground` → `evalGround`
- `telescope` → `simpTelescope`
- `self` → `simp` (recursive simplification)
- `none` → identity (no simplification)
- `rewrite setName [with discharger]` → named theorem set rewriting
- `rewrite [thm₁, ...] [with discharger]` → inline theorem rewriting
- `>>` → `andThen` combinator
- `<|>` → `orElse` combinator

Discharger elaborators (`@[builtin_sym_discharger]`):
- `self` → `dischargeSimpSelf`
- `none` → `dischargeNone`

Note: `orElse` requires a fully-qualified attribute name
(`Lean.Parser.Sym.Simp.orElse`) to avoid a name resolution conflict
where the bare `orElse` resolves to a different syntax node kind.

---------

Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
2026-03-22 02:39:12 +00:00
Leonardo de Moura
9fa1a252f2
fix: nondeterministic crash in grind congruence closure (#13027)
This PR fixes a nondeterministic crash in `grind` caused by a
`BEq`/`Hashable` invariant
violation in the congruence table. `congrHash` uses each expression's
own `funCC` flag to
compute its hash (one-level decomposition for `funCC = true`, full
recursive decomposition
for `funCC = false`), but `isCongruent` only checked the stored
expression's flag. When two
expressions with mismatched `funCC` flags accidentally hash-collided
(via pointer-based
`ptrAddrUnsafe` hashing), `isCongruent` could declare them congruent
despite different
argument counts, leading to an assertion failure in `mkCongrProof`.

The fix requires matching `funCC` flags in `isCongruent`. The PR also
fixes the debug
invariant checker (`checkParents`) to skip `funCC` parents and adds a
regression test for
funCC congruence.

Observed as a nondeterministic crash in Mathlib at
`Analysis/ODE/PicardLindelof.lean`.

Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>
2026-03-21 22:54:58 +00:00
Leonardo de Moura
7897dc91e6
fix: grind fails to prove conjunction of independently provable goals (#13024)
This PR fixes an issue where `grind` could prove each conjunct
individually but failed on the conjunction. The root cause:
`solverAction`'s `.propagated` path calls `processNewFacts` which drains
the `newFacts` queue, but the resulting propagation cascade (congruence
closure, or-propagation, `propagateForallPropDown`) can call
`addNewRawFact`, enqueuing to the separate `newRawFacts` queue. These
raw facts were never drained.

The fix moves `Solvers.mkAction` from `Types.lean` to `Intro.lean` where
it can compose the core solver action with `assertAll`, unconditionally
draining `newRawFacts` after every solver step.

Closes #12581

Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>
2026-03-21 17:04:41 +00:00
Leonardo de Moura
973062e4e1
feat: add Sym.simp theorem set attributes (#13018)
This PR adds named theorem sets for `Sym.simp` with associated
attributes, following the same pattern as `Meta.simp`'s
`register_simp_attr`.

- `register_sym_simp_attr my_set` creates a named set with its own
`PersistentEnvExtension` and attribute
- `@[my_set] theorem ...` adds a rewrite theorem
- `@[my_set] def ...` adds equation theorems from the definition
- `builtin_initialize symSimpExtension` registers a default
`@[sym_simp]` set
- `getSymSimpTheorems` / `getSymSimpExtension?` retrieve theorem sets at
tactic time

New files:
- `Sym/Simp/Attr.lean`: attribute logic (`mkSymSimpAttr`,
`registerSymSimpAttr`)
- `Sym/Simp/RegisterCommand.lean`: `register_sym_simp_attr` macro

Tests:
- `tests/pkg/sym_simp_attr/`: package test with user-defined set
(`my_sym_simp`)
- `tests/elab/sym_simp_set.lean`: tests for the builtin `@[sym_simp]`
set
2026-03-21 03:53:39 +00:00
Henrik Böving
e2120d85c0
feat: throw an error when export declarations have borrow annotations (#13017)
This PR ensures that when a declaration is marked with `@[export]`, the
compiler throws an error if
any of its arguments are marked as borrowed.
2026-03-20 23:22:52 +00:00
Henrik Böving
d2ecad2e91
perf: forward propagation of user defined borrrow annotations (#13001)
This PR introduces additional propagation mechanisms for user defined
borrows to make them have priority over reset-reuse opportunities.
2026-03-20 19:03:17 +00:00
Joachim Breitner
1362cc6041
refactor: simplify structural recursion elaboration (#13008)
This PR removes the custom `M`/`State` monad from structural recursion
elaboration, replacing it with plain `MetaM`. This simplifies the code
and makes the control flow more explicit, in preparation for #12987
which
introduces named `_f` auxiliary definitions for structural recursion.

Key changes:
- Remove `State`/`M` types from `Structural.Basic`, use `MetaM`
throughout
- Extract `withRecFunsAsAxioms` helper for adding recursive functions as
temporary axioms
- Split `tryAllArgs` into `findRecArgCandidates` (analysis) and
`tryCandidates` (backtracking execution)
- Move `withoutModifyingEnv` into each phase that needs it
- For inductive predicates, return matchers from `mkIndPredBRecOnF`
instead of accumulating in state
- Pass `fnTypes` explicitly to `mkBRecOnMotive` instead of re-inferring

This is a pure refactoring with no behavior changes (except matcher
numbering in `inductive_pred` test due to changed
`saveState`/`restoreState` boundaries).

🤖 Generated with [Claude Code](https://claude.com/claude-code)

---------

Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>
2026-03-20 16:10:27 +00:00
Sebastian Ullrich
6f98a76d01
feat: stricter meta check for temporary programs in native_decide etc (#13005)
This PR further enforces that all modules used in compile-time execution
must be meta imported in preparation for enabling
https://github.com/leanprover/lean4/pull/10291

# Breaking changes

Metaprograms that call `compileDecl` directly may now need to call
`markMeta` first where appropriate, possibly based on the value of
`isMarkedMeta` of existing decls. `addAndCompile` should be split into
`addDecl` and `compileDecl` for this in order to insert the call in
between.
2026-03-20 15:51:18 +00:00
Henrik Böving
511be304d7
feat: respect user provided borrow annotations (#12830)
This PR enables support for respecting user provided borrow annotations.
This allows user to mark arguments of their definitions or local
functions with `(x : @&Ty)` and have the borrow inference try its best
to preserve this annotation, thus potentially reducing RC pressure. Note
that in some cases this might not be possible. For example, the compiler
prioritizes preserving tail calls over preserving borrow annotations. A
precise reasoning of why the compiler chose to make its inference
decisions can be obtained with `trace.Compiler.inferBorrow`.

The implementation consists of two parts:
1. A propagator in ToLCNF. This is required because the elaborator does
not place the borrow annotations in the function binders themselves but
just in type annotations of let binders/global declarations while LCNF
expects them in the lambda variable binders themselves. Thus ToLCNF now
implements a (very weak but strong enough for this purpose) propagator
of the borrow annotations of a type annotation into the variable binders
of the term affected by the annotations
2. A weakening of the InferBorrow heuristic. It now has a set of
"forced" and "non-forced" reasons to mark a variable as owned instead of
borrowed. If a variable is user annotated as borrowed, it will only be
marked as owned if the reason is a forced one, e.g. preservation of tail
calls.
2026-03-20 14:28:17 +00:00
Sebastian Ullrich
8e6f2750da
fix: namespace used in private import and current module vanishes dowstream (#12840)
This PR fixes an issue where the use of private imports led to unknown
namespaces in downstream modules.

Fixes #12833
2026-03-20 13:27:26 +00:00
Garmelon
492fda3bca
chore: speed up test suite slightly (#12969)
This PR speeds up some benchmarks when run as tests by lowering their
workload. It also stops testing some of the more expensive benchmarks
that can't be easily made smaller.
2026-03-20 12:24:32 +00:00
Henrik Böving
9676f54cc5
chore: pass the previous stage libLake as plugin (#13000)
This PR avoids bootstrapping headaches when ABI breakages affect lake.
2026-03-20 12:23:20 +00:00
Wojciech Różowski
7e3e7cf5d9
feat: add cbv annotations to iterators and strings (#12961)
This PR adds `cbv` annotations to some iterator and string operations.

---------

Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>
2026-03-20 11:39:40 +00:00
Sebastian Ullrich
c6a89cc716
feat: experimental option to move non-meta compilation out of lean build step (#10291)
The ultimate goal of this work is to turn production of `.ir` files into
separate build step so that it does not block non-`meta` imports and can
be skipped entirely when not needed. This PR implements the main logic
of this new `leanir` compiler executable and runs it after `lean` inside
the same Lake build step but leaves its use disabled behind a
`compiler.postponeCompile` flag until further Lake adjustments move it
to a separate facet so that its use can be actually beneficial.

---------

Co-authored-by: Joscha <joscha@plugh.de>
2026-03-20 10:39:39 +00:00
Leonardo de Moura
d2907b5c96
feat: add contextDependent to Sym.simp Result with two-tier cache (#12996)
This PR adds per-result `contextDependent` tracking to `Sym.Simp.Result`
and splits the simplifier cache into persistent (context-independent)
and transient (context-dependent, cleared on binder entry). This
replaces the coarse `wellBehavedMethods` flag.

Key changes:
- Add `contextDependent : Bool := false` to `Result.rfl` and
`Result.step`
- Split `State.cache` into `persistentCache` and `transientCache`
- Remove `wellBehavedMethods` from `Methods`
- Replace `withoutModifyingCacheIfNotWellBehaved` with
`withFreshTransientCache`
- Change `DischargeResult` to an inductive (`.failed`/`.solved`)
- Add `dischargeAssumption` (context-dependent discharger for testing)
- Add `sym.simp.debug.cache` trace class
- Propagate `contextDependent` through all combinators (congruence,
transitivity, control flow, arrows, rewriting)
- Add `mkRflResult`/`mkRflResultCD` to avoid dynamic allocation of rfl
results
- Fix `isRfl` to ignore `contextDependent` (was silently broken by the
extra field)

Propagation invariant: when combining sub-results, `cd` is the
disjunction of ALL sub-results' flags — including `.rfl` results. If
`simp` returned `.rfl (contextDependent := true)`, it means `simp` might
take a completely different code path in another local context, so all
downstream results must be marked context-dependent.

---------

Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
2026-03-20 00:22:08 +00:00
Mac Malone
d78525b302
fix: lake: ltar caching bug with build -o (#12993)
This PR fixes a bug with Lake where caching an `ltar` produced via `lake
build -o` would fail if `restoreAllArtifacts` was also `true`.
2026-03-19 22:51:09 +00:00
Sofia Rodrigues
90125ed205
feat: introduce URI data type for HTTP (#12128)
This PR introduces the `URI` data type.

This contains the same code as #10478, divided into separate pieces to
facilitate easier review.

The pieces of this feature are:
- Core data structures: #12126
- Headers: #12127
- URI:  #12128
- Body: #12144
- H1: #12146
- Server: #12151
- Client:

---------

Co-authored-by: Rob23oba <152706811+Rob23oba@users.noreply.github.com>
2026-03-19 19:34:28 +00:00
Wojciech Różowski
5cc6585c9b
chore: disable cbv usage warning (#12986)
This disables `cbv` usage warning and reflects that in the corresponding
unit tests.
2026-03-19 14:12:04 +00:00
Sebastian Ullrich
d9c3bbf1b4
fix: prevent induction/cases from swallowing diagnostics when using clause contains by (#12953)
This PR fixes an issue where the `induction` and `cases` tactics would
swallow diagnostics (such as unsolved goals errors) when the `using`
clause contains a nested tactic.

Closes #12815
2026-03-19 13:52:16 +00:00
Wojciech Różowski
8f6ade06ea
fix: interaction between cbv_opaque and inline (#12981)
This PR fixes the interaction between `cbv_opaque` and
`inline`/`always_inline` annotations, to make sure that inlined
definitions marked as `cbv_opaque` are not unfolded during the
preprocessing stage of `cbv` tactic.
2026-03-19 11:23:57 +00:00
Joachim Breitner
747262e498
fix: respect pp.privateNames in #print signature (#12979)
This PR makes `#print` show the full internal private name (including
module prefix) in the declaration signature when `pp.privateNames` is
set to true. Previously, `pp.privateNames` only affected names in the
body but the signature always stripped the private prefix.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>
2026-03-19 09:16:48 +00:00
Derrik Petrin
87180a09c4
fix: fix a collection of docstring errors (#12959)
This PR fixes a series of errors in docstrings.

This includes:
- incorrect gramar
- errant reference to "dependent" in the non-dependent `HashMap` files
- reference to expression metavariables as universe level metavariables
- outdated reference to `usizeSz` instead of `USize.size`
- syntax errors in code examples
- a broken link to a paper

---------

Co-authored-by: Derrik Petrin <derrik.petrin@pm.me>
2026-03-19 06:42:11 +00:00
Joachim Breitner
b7380758ae
refactor: remove Lean.Environment.replay from core (#12972)
This PR removes the obsolete `Lean.Environment.replay` from
`src/Lean/Replay.lean` and replaces it with the improved version from
`src/LeanChecker/Replay.lean`, which includes fixes for duplicate
theorem handling and Quot/Eq dependency ordering. The primed names
(`Replay'`, `replay'`) are renamed back to `Replay` and `replay`.

A test for the original issue (nested inductives failing with `replay`)
is added as `tests/elab/issue12819.lean`.

Closes #12819

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>
2026-03-18 22:11:42 +00:00
Leonardo de Moura
58ef418dda
feat: add sym => interactive mode (#12970)
This PR adds a `sym =>` tactic that enters an interactive symbolic
simulation
mode built on `grind`. Unlike `grind =>`, it does not eagerly introduce
hypotheses or apply by-contradiction, giving users explicit control over
`intro`, `apply`, and `internalize` steps.

New tactics available in `sym =>` mode:
- `intro` / `intros`: introduce binders and internalize into the E-graph
by
  default. Use `intro~` or `intro (internalize := false)` to skip
  internalization.
- `apply t`: apply backward rules with caching for `repeat`.
- `internalize` / `internalize_all`: internalize hypotheses into the
E-graph.
- `by_contra`: apply proof by contradiction, negating the target.

Satellite solvers (`lia`, `ring`, `linarith`) automatically introduce
remaining
binders and apply by-contradiction in `sym =>` mode, matching their
behavior in
default tactic mode. All existing `grind =>` tactics (`finish`,
`instantiate`,
`cases`, etc.) also work in `sym =>` mode. The sym-specific tactics are
guarded
and rejected in regular `grind =>` mode.

```lean
example (x : Nat) : myP x → myQ x := by
  sym [myP_myQ] =>
    intro h
    finish

example (x y z : Nat) : x > 1 → x + y + z > 0 := by
  sym =>
    lia
```
2026-03-18 14:29:18 +00:00
Joachim Breitner
b2aec782eb
fix: re-privatize constant name prefix in realizeConst to avoid diamond import collisions (#12964)
This PR fixes an issue where `realizeConst` would generate auxiliary
declarations
(like `_sparseCasesOn`) using the original defining module's private
name prefix
rather than the realizing module's prefix. When two modules
independently realized
the same imported constant, they produced identically-named auxiliary
declarations,
causing "environment already contains" errors on diamond import.

The fix re-privatizes the constant name under the current module before
passing it
to `withDeclNameForAuxNaming`, ensuring each realizing module generates
distinctly
named auxiliary declarations.

Fixes #12825

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

---------

Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>
2026-03-18 13:54:50 +00:00
Markus Himmel
cb0455e379
feat: simprocs for n.digitChar = c (#12966)
This PR adds simp lemmas that simplify `n.digitChar = '0'` to `n = 0`
and a simproc that simplifies `n.digitChar = '!'` to `False`.
2026-03-18 12:00:24 +00:00
Garmelon
e14230c0f3
chore: import measure.py instead of calling it (#12962)
Thereby avoiding the overhead of one python interpreter per wrapped lean
call during the build benchmarks.
2026-03-18 10:23:32 +00:00
Leonardo de Moura
f0b367d7aa
fix: mark List.length as @[implicit_reducible] (#12924)
This PR fixes a regression introduced in Lean 4.29.0-rc2 where `simp` no
longer simplifies inside type class instance arguments due to the
`backward.isDefEq.respectTransparency` change. This breaks proofs where
a term like `(a :: l).length` appears both in the main expression and
inside implicit instance arguments (e.g., determining a `BitVec` width).

**The problem:** After `simp only [List.length_cons]`, the main
expression has `l.length + 1` but instances still have `(a ::
l).length`. Since `simp` no longer simplifies inside instances, and
`isDefEq` won't unfold `List.length` at the default transparency,
subsequent lemma applications fail.

**Reproducer** (from Son Ho, reported by Sebastian Ullrich):
```lean
theorem BitVec.getElem!_eq_testBit_toNat {w : Nat} (x : BitVec w) (i : Nat) :
     x[i]! = x.toNat.testBit i := by sorry

example (l : List Nat) (a : Nat) (j : Nat) :
  (0#((a :: l).length))[j]! = (0#((a :: l).length)).toNat.testBit j := by
  simp only [List.length_cons]
  simp only [BitVec.getElem!_eq_testBit_toNat] -- works in 4.28.0-rc1, fails in 4.29.0-rc6
```

**The fix:** Mark `List.length` as `@[implicit_reducible]`, allowing
`isDefEq` to unfold it when checking implicit arguments. Several proofs
that previously needed a trailing `rfl` after `simp` now close directly,
since `simp` can see through `List.length` in more positions.

**Longer term:** The root cause is that `GetElem` carries complex proof
obligations in its type class instances, making implicit arguments
sensitive to definitional equality of collection sizes. We are
considering a redesign with a noncomputable `GetElemV` variant based on
`Nonempty` that avoids these casts entirely, but that is a larger change
planned for a future release.

---------

Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>
2026-03-18 08:45:15 +00:00
Mac Malone
61a3443a95
feat: lake: track platform dependency in cache maps (#12954)
This PR changes the Lake `CacheMap` data structure to track the
platform-dependence of outputs. Platform-independent packages will no
longer include platform-dependent mappings in the output files produced
by `lake build -o`.
2026-03-18 01:18:57 +00:00
Garmelon
6b7f0ad5fc
chore: check test output before exit code in piles (#12947)
This improves the feedback when tests fail. Getting a diff is more
useful than a vague exit code.
2026-03-17 16:34:21 +00:00
Garmelon
7c011aa522
fix: use process signal numbers from correct architecture (#12900)
This PR fixes some process signals that were incorrectly numbered.

From what I can tell, the code used signals and signal numbers for
Alpha/SPARC, not x86/ARM. The test was also broken and always green,
hiding the mistake.
2026-03-17 13:33:13 +00:00
Wojciech Różowski
6160d17e2d
feat: allow @[cbv_eval] to override @[cbv_opaque] (#12944)
This PR changes the interaction between `@[cbv_opaque]` and
`@[cbv_eval]`
attributes in the `cbv` tactic. Previously, `@[cbv_opaque]` completely
blocked
all reduction including `@[cbv_eval]` rewrite rules. Now, `@[cbv_eval]`
rules
can fire on `@[cbv_opaque]` constants, allowing users to provide custom
rewrite
rules without exposing the full definition. Equation theorems, unfold
theorems,
and kernel reduction remain suppressed for opaque constants.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>
2026-03-17 13:08:21 +00:00
Sofia Rodrigues
a0048bf703
feat: introduce Headers data type for HTTP (#12127)
This PR introduces the `Headers` data type, that provides a good and
convenient abstraction for parsing, querying, and encoding HTTP/1.1
headers.

This contains the same code as #10478, divided into separate pieces to
facilitate easier review.

The pieces of this feature are:
- Core data structures: #12126
- Headers: #12127
- URI:  #12128
- Body: #12144
- H1: #12146
- Server: #12151
- Client:

---------

Co-authored-by: Rob23oba <152706811+Rob23oba@users.noreply.github.com>
2026-03-17 12:25:01 +00:00
Robin Arnez
aa18927d2e
fix: segfault in idbgClientLoop (#12940)
This PR fixes a segfault when running `idbgClientLoop`. `@[extern]`
expects that the function doesn't include erased arguments in the
signature; however, `@[export]` exports the function with all arguments,
including erased ones. This causes a function signature mismatch between
`idbgClientLoopImpl` and `idbgClientLoop`, causing segfaults. However,
instead of solving the deeper problem that `@[extern]` - `@[export]`
pairs can cause such problems, this PR removes the erased arguments from
`idbgClientLoopImpl` and replaces occurrences of `α` with `NonScalar`.
2026-03-17 10:55:54 +00:00
damiano
6b604625f2
fix: add missing pp-spaces in grind_pattern (#11686)
This PR adds a pretty-printed space in `grind_pattern`.

[#lean4 > Some pretty printing quirks @
💬](https://leanprover.zulipchat.com/#narrow/channel/270676-lean4/topic/Some.20pretty.20printing.20quirks/near/563848793)

Co-authored-by: Kim Morrison <kim@tqft.net>
2026-03-17 04:15:02 +00:00
Mac Malone
9e0aa14b6f
feat: lake: fixedToolchain package configuration (#12935)
This PR adds the `fixedToolchain` Lake package configuration option.
Setting this to `true` informs Lake that the package is only expected to
function on a single toolchain (like Mathlib). This causes Lake's
toolchain update procedure to prioritize its toolchain and avoids the
need to separate input-to-output mappings for the package by toolchain
version in the Lake cache.
2026-03-17 02:37:55 +00:00
Garmelon
5c685465bd
chore: handle absence of meld in fix_expected.py (#12934) 2026-03-16 19:07:44 +00:00
Garmelon
ef87f6b9ac
chore: delete temp files before, not after tests (#12932) 2026-03-16 19:02:28 +00:00
Garmelon
49715fe63c
chore: improve how test suite interacts with stages (#12913)
The tests need to run with certain environment variables set that only
cmake really knows and that differ between stages. Cmake could just set
the variables directly when running the tests and benchmarks, but that
would leave no good way to manually run a single benchmark. So cmake
generates some stage-specific scripts instead that set the required
environment variables.

Previously, those scripts were sourced directly by the individual
`run_*` scripts, so the env scripts of different stages would overwrite
each other. This PR changes the setup so they can instead be generated
next to each other. This also simplifies the `run_*` scripts themselves
a bit, and makes `tests/bench/build` less of a hack.
2026-03-16 15:20:03 +00:00
Jesse Alama
fa9a32b5c8
fix: correct swapped operands in Std.Time subtraction instances (#12919)
This PR fixes the `HSub PlainTime Duration` instance, which had its
operands reversed: it computed `duration - time` instead of `time -
duration`. For example, subtracting 2 minutes from `time("13:02:01")`
would give `time("10:57:59")` rather than the expected
`time("13:00:01")`. We also noticed that `HSub PlainDateTime
Millisecond.Offset` is similarly affected.

Closes #12918
2026-03-16 10:52:06 +00:00
Mac Malone
57df23f27e
feat: lake: cached compressed module artifacts (#12914)
This PR adds packing and unpacking of module artifacts into `.ltar`
archives using `leantar`.
2026-03-16 04:36:19 +00:00
Mac Malone
ea8fca2d9f
refactor: lake: download arts by default in cache get (#12927)
This PR changes `lake cache get` to download artifacts by default.
Artifacts can be downloaded on demand with the new `--mappings-only`
option (`--download-arts` is now obsolete).

In the future, the plan is to have Lake download mappings when cloning
dependencies. Then, `lake cache get` will primarily be used to download
artifacts eagerly. Thus, it makes sense to have that as the default.
2026-03-16 02:29:44 +00:00
Leonardo de Moura
cfa8c5a036
fix: handle universe level commutativity in sym pattern matching (#12923)
This PR fixes a bug where `max u v` and `max v u` fail to match in
SymM's pattern matching. Both `processLevel` (Phase 1) and
`isLevelDefEqS` (Phase 2) treated `max` positionally, so `max u v ≠ max
v u` structurally even though they are semantically equal.

The fix has three parts:
- Eagerly normalize universe levels in patterns at creation time
(`preprocessDeclPattern`, `preprocessExprPattern`,
`mkSimprocPatternFromExpr`)
- Normalize the target level in `processLevel` before matching, using a
`where go` refactor
- Add `tryApproxMaxMax` to `processLevel` and `isLevelDefEqS`: when
positional `max/max` matching would fail, check if one argument from
each side matches structurally and match the remaining pair

Also moves `normalizeLevels` from `Grind.Util` to `Sym.Util` to avoid
code duplication, since both Sym and Grind need it.

Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>
2026-03-15 01:06:16 +00:00