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>
56 lines
2 KiB
Text
56 lines
2 KiB
Text
module
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/-!
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# Test: `simp` with `@[reducible]` class field projections
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When a class field like `X.x` is marked `@[reducible]`, `isDefEqDelta` unfolds it to `.proj` form.
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`isDefEqProj` must then bump transparency to `.instances` when comparing the struct arguments,
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since the projection's parameter is instance-implicit. Without this bump, `eq_self` fails because
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instances like `instX a` vs `instX b` are stuck at `.reducible`.
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-/
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namespace SimpReducibleClassField
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@[implicit_reducible] def a := 0
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@[implicit_reducible] def b := 0
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class X where
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x : Nat
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instance instX (n : Nat) : X where
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x := n
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-- Test 1: plain simp, semireducible X.x (works on master)
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-- isDefEqArgs bumps to .instances for instance-implicit param of X.x
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example : (instX a).x = (instX b).x := by simp
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-- Test 2: plain simp, @[reducible] X.x
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-- With backward.whnf.reducibleClassField = false: isDefEqDelta unfolds X.x to .proj form,
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-- isDefEqProj bumps to .instances via withInstanceConfig.
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-- With backward.whnf.reducibleClassField = true: tryHeuristic in isDefEqDelta applies the
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-- argument-comparison heuristic, and isDefEqArgs bumps to .instances for instance-implicit params.
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set_option allowUnsafeReducibility true in
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attribute [reducible] X.x in
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example : (instX a).x = (instX b).x := by simp
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-- Test 2b: same as Test 2 with backward.whnf.reducibleClassField explicitly enabled
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set_option allowUnsafeReducibility true in
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attribute [reducible] X.x in
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set_option backward.whnf.reducibleClassField true in
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example : (instX a).x = (instX b).x := by simp
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-- Test 3: simp [X.x] with semireducible args exposes stuck .proj node
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-- reduceProjFn? unfolds X.x at .instances, but the .proj can't reduce further
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-- because instX a' is not a constructor app at .reducible. This is expected:
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-- the user explicitly requested the unfolding.
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def a' := 0
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def b' := 0
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/--
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error: unsolved goals
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⊢ (instX a').1 = (instX b').1
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-/
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#guard_msgs in
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example : (instX a').x = (instX b').x := by simp [X.x]
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end SimpReducibleClassField
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