23236ef520
This PR fixes a bug that could cause the `injectivity` tactic to fail in reducible mode, which could cause unfolding lemma generation to fail (used by tactics such as `unfold`). In particular, `Lean.Meta.isConstructorApp'?` was not aware that `n + 1` is equivalent to `Nat.succ n`. Closes #5064
27 lines
578 B
Text
27 lines
578 B
Text
/-!
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# Make sure `injection` tactic can handle `0 = n + 1`
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https://github.com/leanprover/lean4/issues/5064
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-/
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/-!
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Motivating example from #5064.
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This failed when generating the splitter theorem for `thingy`.
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-/
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def thingy : List (Nat ⊕ Nat) → List Bool
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| Sum.inr (_n + 2) :: l => thingy l
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| _ => []
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termination_by l => l.length
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/-- info: ⊢ [] = [] -/
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#guard_msgs in
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theorem thingy_empty : thingy [] = [] := by
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unfold thingy
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trace_state
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rfl
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/-!
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Test using `injection` directly.
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-/
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example (n : Nat) (h : 0 = n + 1) : False := by
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with_reducible injection h
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