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>
69 lines
1.6 KiB
Text
69 lines
1.6 KiB
Text
def Option_map (f : α → β) : Option α → Option β
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| none => none
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| some x => some (f x)
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/--
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info: equations:
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@[backward_defeq] theorem Option_map.eq_1.{u_1, u_2} : ∀ {α : Type u_1} {β : Type u_2} (f : α → β),
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Option_map f none = none
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@[backward_defeq] theorem Option_map.eq_2.{u_1, u_2} : ∀ {α : Type u_1} {β : Type u_2} (f : α → β) (x_1 : α),
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Option_map f (some x_1) = some (f x_1)
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-/
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#guard_msgs in
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#print equations Option_map
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/--
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info: Option_map.eq_def.{u_1, u_2} {α : Type u_1} {β : Type u_2} (f : α → β) (x✝ : Option α) :
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Option_map f x✝ =
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match x✝ with
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| none => none
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| some x => some (f x)
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-/
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#guard_msgs in
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#check Option_map.eq_def
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/--
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info: Option_map.eq_unfold.{u_1, u_2} :
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@Option_map = fun {α} {β} f x =>
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match x with
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| none => none
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| some x => some (f x)
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-/
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#guard_msgs in
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#check Option_map.eq_unfold
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def answer := 42
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/-- info: answer.eq_unfold : answer = 42 -/
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#guard_msgs in
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#check answer.eq_unfold
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-- structural recursion
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def List_map (f : α → β) : List α → List β
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| [] => []
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| x::xs => f x :: List_map f xs
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/--
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info: List_map.eq_unfold.{u_1, u_2} :
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@List_map = fun {α} {β} f x =>
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match x with
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| [] => []
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| x :: xs => f x :: List_map f xs
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-/
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#guard_msgs in
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#check List_map.eq_unfold
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-- wf recursion
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def List_map2 (f : α → β) : List α → List β
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| [] => []
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| x::xs => f x :: List_map2 f xs
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termination_by l => l
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/--
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info: List_map2.eq_unfold.{u_1, u_2} :
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@List_map2 = fun {α} {β} f x =>
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match x with
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| [] => []
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| x :: xs => f x :: List_map2 f xs
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-/
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#guard_msgs in
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#check List_map2.eq_unfold
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