dede354e77
This didn't work before ``` def f (n : Nat) : Nat := match n with | 0 => 0 | n + 1 => (f) n ``` because the `RecApp` metadata marker gets in the way. More practically relevant, such code is to be produced when using `rw` or `simp` in recursive theorems (see included test case). We can fix this by preprocessing the definitions and floating the `.mdata` marker out of applications. For structural recursion, there already exists a `preprocess` function; this now also floats out `.mdata` markers. For well-founded recursion, this introduces an analogous `preprocess` function. Fixes #2810. One test case output changes: With the `.mdata` out of the way, we get a different error message. Seems fine. Alternative approaches are: * Leaving the `.mdata` marker where it is, and looking around it. Tried in #2813, but not nice (many many places where `withApp` etc. need to be adjusted). * Moving the `.mdata` _inside_ the application, so that `withApp` still works. Tried in #2814. Also not nice, the invariant that the `.mdata` is around the `.const` is tedious to maintain.
6 lines
199 B
Text
6 lines
199 B
Text
1673.lean:1:4-1:9: error: fail to show termination for
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foo.a
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with errors
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structural recursion cannot be used
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well-founded recursion cannot be used, 'foo.a' does not take any (non-fixed) arguments
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