5b87ab6625
This PR replaces the transparency bump from `.reducible` to `.instances`
in `whnfMatcher` with an explicit allowlist in `canUnfoldAtMatcher`.
Previously, `whnfMatcher` would unfold all `implicitReducible`
definitions and all `fromClass` projections when reducing match
discriminants. This made it impossible to mark definitions as
`implicit_reducible` without silently affecting match reduction
behavior.
The new `canUnfoldAtMatcher` delegates to `canUnfoldDefault` first
(respecting the ambient transparency), then allows unfolding of
`match_pattern`-attributed definitions, and finally checks an explicit
allowlist:
- `OfNat.ofNat` — numeric literals in match discriminants
- `NatCast.natCast` — `↑m` coercions (pervasive in Int proofs)
- `Zero.zero`, `One.one` — `0`/`1` class projections in match
discriminants
- `Fin.ofNat`, `HMod.hMod`, `Mod.mod` — Fin literal reduction
- `decEq`, `Nat.decEq` — decidable equality
- `Char.ofNat`, `Char.ofNatAux` — character literals
- `String.decEq`, `List.hasDecEq` — string/list equality
- `UInt{8,16,32,64}.{ofNat,decEq}` — unsigned integer literals and
equality
The key change is removing the blanket `implicitReducible` and
`fromClass` checks, so that marking definitions as `implicit_reducible`
no longer silently affects match reduction.
Additionally, `reduceMatcher?` and `reduceRecMatcher?` now call
`consumeMData` on their input to handle mdata-wrapped matcher
expressions.
Mathlib adaptation: the removal of the `fromClass` projection check
means class projections like `CategoryStruct.comp`, `CategoryStruct.id`,
`Min.min` etc. are no longer auto-unfolded in match discriminants.
Affected proofs add these projections explicitly to `simp`/`dsimp`
calls.
---------
Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>
17 lines
307 B
Text
17 lines
307 B
Text
case succ
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x : Nat
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ih : isEven (2 * x) = true
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⊢ (match 2 * (x + 1) with
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| 0 => true
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| n.succ => isOdd n) =
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true
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case succ
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x : Nat
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ih : isEven (2 * x) = true
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⊢ (match 2 * (x + 1) with
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| 0 => true
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| n.succ =>
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match n with
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| 0 => false
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| n.succ => isEven n) =
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true
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