c78bb62c51
The goal at the crucial step is ``` a : Array Nat i : Fin ?m.27 ⊢ ↑i < a.size ``` and after the `apply Fin.val_lt_of_le;` we have ``` a : Array Nat i : Fin ?m.27 ⊢ ?m.27 ≤ a.size ``` and now `apply Fin.val_lt_of_le` applies again, due to accidential defeq. Adding `with_reducible` helps here. fixes #5061
33 lines
1.1 KiB
Text
33 lines
1.1 KiB
Text
opaque fin_max {n: Nat} (f: Fin n → Nat) : Nat
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set_option maxRecDepth 30 in
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-- NB: Important to not specify the implicit argument of fin_max here
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def test (a: Array Nat) : Nat := @fin_max _ fun i =>
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let h : i < a.size := by
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-- this may apply once
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with_reducible apply Fin.val_lt_of_le
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fail_if_success with_reducible apply Fin.val_lt_of_le;
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exact Nat.le_refl _
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a.get ⟨i, h⟩
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set_option pp.mvars false
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-- This used to cause
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-- error: maximum recursion depth has been reached in #5061
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/--
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error: failed to prove index is valid, possible solutions:
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- Use `have`-expressions to prove the index is valid
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- Use `a[i]!` notation instead, runtime check is perfomed, and 'Panic' error message is produced if index is not valid
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- Use `a[i]?` notation instead, result is an `Option` type
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- Use `a[i]'h` notation instead, where `h` is a proof that index is valid
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a : Array Nat
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i : Fin ?_
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⊢ ↑i < a.size
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-/
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#guard_msgs in
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set_option maxRecDepth 40 in
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def test2 (a: Array Nat) : Nat := @fin_max _ fun i =>
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let h : i < a.size := by
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get_elem_tactic
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a.get ⟨i, h⟩
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