ac9a1cb415
This PR introduces stricter inference for the `@[defeq]` attribute and a companion `@[backward_defeq]` attribute that preserves the pre-PR behavior as an opt-in. ### What changed * `@[defeq]` is now inferred only when the equation holds at `.instances` transparency (the transparency `dsimp` operates at). * `@[backward_defeq]` is the old set: every theorem whose `rfl` proof the legacy inference would have accepted is tagged `@[backward_defeq]`, so `defeq ⊆ backward_defeq` holds by construction. * The option `backward.defeqAttrib.useBackward` (default `false`) makes `dsimp` also use `@[backward_defeq]` theorems, restoring the pre-PR behavior for a specific proof or file. * The option is eqn-affecting: its value at the point of a function's definition is recorded so that the equation lemmas later generated for that function use the same value, regardless of the ambient option at the use site. ### Mathlib adaption A companion adaption branch (`lean-pr-testing-backward-defeq-attrib` on mathlib4) builds cleanly against this PR and passes `lake test` without warnings. Most adaption changes are scoped `set_option backward.defeqAttrib.useBackward true in` additions on the failing declarations; a small number of files needed proof-level edits where the stored form of a `dsimp%`/`@[reassoc]`/`@[elementwise]` /`@[simps]`/`@[to_app]`-generated lemma had drifted under the stricter regime. --------- Co-authored-by: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
62 lines
2.5 KiB
Text
62 lines
2.5 KiB
Text
/-!
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# Ensure equational theorems generation doesn't fail when metadata is involved
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https://github.com/leanprover/lean4/issues/6789
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The original error would happen because `casesOnStuckLHS` (https://github.com/leanprover/lean4/blob/4ca98dcca2b0995dddff444cfef1f3ccc89c7b12/src/Lean/Meta/Match/MatchEqs.lean#L51)
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would fail to find an fvar to do `cases` on when that fvar would be encapsulated by some metadata.
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-/
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inductive Con
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| nil
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| ext (Γ : Con) (n : Nat)
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variable {Op : Con → Con → Type u}
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inductive Extension : Con → Con → Type
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| zero : Extension Γ Γ
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| succ : Extension Γ Δ → (n : Nat) → Extension Γ (.ext Δ n)
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def Extension.recOn'
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{motive : (Γ Δ : Con) → Extension Γ Δ → Sort v}
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(zero : {Γ : Con} → motive Γ Γ .zero)
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(succ
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: {Γ Δ : Con} → (xt : Extension Γ Δ)
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→ (A : Nat)
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→ motive Γ Δ xt
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→ motive Γ (.ext Δ A) (.succ xt A))
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: {Γ Δ : Con} → (xt : Extension Γ Δ) → motive Γ Δ xt
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| _, _, .zero => zero
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| _, _, .succ xt A => succ xt A (Extension.recOn' zero succ xt)
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/--
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info: equations:
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theorem Extension.recOn'.eq_1.{v} : ∀ {motive : (Γ Δ : Con) → Extension Γ Δ → Sort v}
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(zero : {Γ : Con} → motive Γ Γ Extension.zero)
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(succ : {Γ Δ : Con} → (xt : Extension Γ Δ) → (A : Nat) → motive Γ Δ xt → motive Γ (Δ.ext A) (xt.succ A)) (x : Con),
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Extension.recOn' zero succ Extension.zero = zero
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@[backward_defeq] theorem Extension.recOn'.eq_2.{v} : ∀ {motive : (Γ Δ : Con) → Extension Γ Δ → Sort v}
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(zero : {Γ : Con} → motive Γ Γ Extension.zero)
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(succ : {Γ Δ : Con} → (xt : Extension Γ Δ) → (A : Nat) → motive Γ Δ xt → motive Γ (Δ.ext A) (xt.succ A)) (x Δ : Con)
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(A : Nat) (xt : Extension x Δ),
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Extension.recOn' zero succ (xt.succ A) = succ xt A (Extension.recOn' (fun {Γ} => zero) (fun {Γ Δ} => succ) xt)
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-/
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#guard_msgs in
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#print equations Extension.recOn'
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def Extension.pullback_con
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: (xt : Extension B Δ) → (σ : Op B' B)
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→ Con
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| .zero, σ => B'
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| .succ xt A, σ => .ext (pullback_con xt σ) A
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/--
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info: equations:
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@[backward_defeq] theorem Extension.pullback_con.eq_1.{u} : ∀ {Op : Con → Con → Type u} {B B' : Con} (x : Op B' B),
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Extension.zero.pullback_con x = B'
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@[backward_defeq] theorem Extension.pullback_con.eq_2.{u} : ∀ {Op : Con → Con → Type u} {B B' : Con} (x : Op B' B)
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(Δ_2 : Con) (xt : Extension B Δ_2) (A : Nat), (xt.succ A).pullback_con x = (xt.pullback_con x).ext A
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-/
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#guard_msgs in
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#print equations Extension.pullback_con
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