18c97926a1
this is in preparation for #4542, and extracts from `findRecArg` the functionality for trying one particular argument. It also refactors the code a bit. In particular * It reports errors in the order of the parameters, not the order of in which they are tried (it tries non-indices first). * For every argument it will say why it wasn't tried, even if the reason is quite obviously (fixed prefix, or `Prop`-typed etc.) Therefore there is some error message churn.
38 lines
1 KiB
Text
38 lines
1 KiB
Text
terminationFailure.lean:7:2-7:3: error: fail to show termination for
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f.g
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f
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with errors
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structural recursion does not handle mutually recursive functions
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Could not find a decreasing measure.
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The arguments relate at each recursive call as follows:
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(<, ≤, =: relation proved, ? all proofs failed, _: no proof attempted)
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Call from f.g to f at 9:9-12:
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x1
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x =
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Call from f to f.g at 3:4-7:
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x
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x1 =
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Please use `termination_by` to specify a decreasing measure.
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f (x : Nat) : Nat
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f.g : Nat → Nat
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1
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2
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terminationFailure.lean:20:4-20:5: error: fail to show termination for
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h
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with errors
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structural recursion cannot be used:
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argument #1 cannot be used for structural recursion
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failed to eliminate recursive application
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h x
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failed to prove termination, possible solutions:
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- Use `have`-expressions to prove the remaining goals
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- Use `termination_by` to specify a different well-founded relation
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- Use `decreasing_by` to specify your own tactic for discharging this kind of goal
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x : Nat
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⊢ False
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h (x : Nat) : Foo
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Foo.a
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