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fix: predefinition preprocessing: float .mdata out of non-unary appli…
…cations (#3204) 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).
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Original file line number | Diff line number | Diff line change |
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def zero_out (arr : Array Nat) (i : Nat) : Array Nat := | ||
if h : i < arr.size then | ||
zero_out (arr.set ⟨i, h⟩ 0) (i + 1) | ||
else | ||
arr | ||
termination_by arr.size - i | ||
decreasing_by simp_wf; apply Nat.sub_succ_lt_self _ _ h | ||
|
||
-- set_option trace.Elab.definition true | ||
theorem size_zero_out (arr : Array Nat) (i : Nat) : (zero_out arr i).size = arr.size := by | ||
unfold zero_out | ||
split | ||
· rw [size_zero_out] | ||
rw [Array.size_set] | ||
· rfl | ||
termination_by arr.size - i | ||
decreasing_by simp_wf; apply Nat.sub_succ_lt_self; assumption |