c2ec2ecab1
This PR fixes the interaction between `backward.whnf.reducibleClassField` and `isDefEqDelta`'s argument-comparison heuristic. When `backward.whnf.reducibleClassField` is enabled, `unfoldDefault` reduces class field projections past the `.proj` form at `.instances` transparency. This causes `isDefEqDelta` to lose the instance structure that `isDefEqProj` needs to bump transparency for instance-implicit parameters. The fix adds an `.abbrev` branch in `isNonTrivialRegular` that classifies class field projections as nontrivial when the option is enabled, so `tryHeuristic` applies the argument-comparison heuristic (with the correct transparency bump) instead of unfolding. Key insight: all projection functions receive `.abbrev` kernel hints (not `.regular`), regardless of their reducibility status. Structure projections default to `.reducible` status, while class projections default to `.semireducible` status. The old code only handled the `.regular` case and treated everything else (including `.abbrev`) as trivial. Also fixes two minor comment issues in `tryHeuristic`: "non-trivial regular definition" → "non-trivial definition" (since `.abbrev` definitions can now be nontrivial too), and "when `f` is not simple" → "when `f` is simple" (logic inversion in the original comment). 🤖 Generated with [Claude Code](https://claude.com/claude-code) Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>
48 lines
1.5 KiB
Text
48 lines
1.5 KiB
Text
import Lean
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/-!
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# Test: projection functions have `.abbrev` kernel hints
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All projection functions receive `.abbrev` kernel hints at creation time.
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Structure projections default to `.reducible` status, while class projections
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default to `.semireducible` status. The `@[reducible]` attribute changes the
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reducibility status but does **not** change the kernel hint.
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These properties are relied upon by `isNonTrivialRegular` in `ExprDefEq.lean`.
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That function uses the `.abbrev` branch to detect class projections and treat
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them as nontrivial when `backward.whnf.reducibleClassField` is enabled, so that
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`tryHeuristic` applies the argument-comparison heuristic (with the correct
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transparency bump for instance-implicit parameters) instead of unfolding past
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the `.proj` form. If the kernel hints or default reducibility status for
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projections change, `isNonTrivialRegular` must be updated accordingly.
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-/
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structure Y where
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x : Nat
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class X where
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x : Nat
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open Lean
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deriving instance Repr for ReducibilityHints
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def showHintAndReduceAttr (declName : Name) : CoreM Unit := do
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let info ← getConstInfo declName
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IO.println (repr info.hints)
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IO.println (repr (← getReducibilityStatus declName))
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-- Structure projection: `.abbrev` hint, `.reducible` status
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/--
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info: Lean.ReducibilityHints.abbrev
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Lean.ReducibilityStatus.reducible
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-/
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#guard_msgs in
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#eval showHintAndReduceAttr ``Y.x
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-- Class projection: `.abbrev` hint, `.semireducible` status
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/--
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info: Lean.ReducibilityHints.abbrev
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Lean.ReducibilityStatus.semireducible
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-/
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#guard_msgs in
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#eval showHintAndReduceAttr ``X.x
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