5f38a483f2
`MVarId.congr?` and `MVarId.hcongr?` should return `none` if an exception is thrown while applying congruence theorem. `MVarId.hcongr?` should try `eq_of_heq` before trying to apply `hcongr` theorem. closes #1787 BTW: Lean 4 `congr` tactic is applying `assumption`. Lean 3 version does not.
13 lines
418 B
Text
13 lines
418 B
Text
open Function
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def Set (α : Type u) := α → Prop
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example {α : Type u}
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(f : α → Type (max u v))
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(U : α) (hU : f U = Set (Sigma f)) :
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let g : Set (Sigma f) → Sigma f := fun (s : Set (Sigma f)) => ⟨U, cast hU.symm s⟩
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∀ ⦃s t : Set (Sigma f)⦄,
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g s = g t → cast hU (g s).snd = cast hU (g t).snd :=
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by
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intros g s t h
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congr -- reduces to `(g s).snd = (g t).snd`, not `g s = g t`
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