409c6cac4c
Recursive predefinitions contains “rec app” markers as mdata in the predefinitions, but sometimes these get in the way of termination checking, when you have ``` [mdata (fun x => f)] arg ``` Therefore, the `preprocess` pass floats them out of applications (originally only for structural recursion, since #2818 also for well-founded recursion). But the code was incomplete: Because `Meta.transform` calls `post` on `f x y` only once (and not also on `f x`) one has to float out of nested applications as well. A consequence of this can be that in a recursive proof, `rw [foo]` does not work although `rw [foo _ _]` does. Also adding the testcase where @david-christiansen and I stumbled over this (Maybe the two preprocess modules can be combined, now that #2973 is landed, will try that in a follow-up).
17 lines
532 B
Text
17 lines
532 B
Text
def zero_out (arr : Array Nat) (i : Nat) : Array Nat :=
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if h : i < arr.size then
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zero_out (arr.set ⟨i, h⟩ 0) (i + 1)
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else
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arr
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termination_by arr.size - i
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decreasing_by simp_wf; apply Nat.sub_succ_lt_self _ _ h
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-- set_option trace.Elab.definition true
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theorem size_zero_out (arr : Array Nat) (i : Nat) : (zero_out arr i).size = arr.size := by
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unfold zero_out
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split
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· rw [size_zero_out]
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rw [Array.size_set]
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· rfl
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termination_by arr.size - i
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decreasing_by simp_wf; apply Nat.sub_succ_lt_self; assumption
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