249530f3c1
Rather than having a special pass where `mkInhabitantFor` uses the `assumption` tactic, it creates `Inhabited` instances for each parameter and just searches for an `Inhabited`/`Nonempty` instance for the return type. This makes examples like the following work: ```lean partial def f (x : X) : Bool × X := ... ``` Removes the strategy where it looks for `Inhabited`/`Nonempty` instances for every suffix of the signature. This is a follow-up to #5780. Motivated [by Zulip](https://leanprover.zulipchat.com/#narrow/channel/113489-new-members/topic/Why.20return.20type.20of.20partial.20function.20MUST.20.60inhabited.60.3F/near/477905312).
26 lines
1.5 KiB
Text
26 lines
1.5 KiB
Text
sanitychecks.lean:1:8-1:15: error: fail to show termination for
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unsound
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with errors
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failed to infer structural recursion:
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no parameters suitable for structural recursion
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well-founded recursion cannot be used, 'unsound' does not take any (non-fixed) arguments
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sanitychecks.lean:4:8-4:32: error: 'partial' theorems are not allowed, 'partial' is a code generation directive
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sanitychecks.lean:7:7-7:31: error: 'unsafe' theorems are not allowed
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sanitychecks.lean:10:0-10:23: error: failed to synthesize
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Inhabited False
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Additional diagnostic information may be available using the `set_option diagnostics true` command.
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sanitychecks.lean:18:12-18:20: error: invalid use of 'partial', 'Foo.unsound3' is not a function
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False
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sanitychecks.lean:20:0-20:54: error: failed to compile 'partial' definition 'Foo.unsound4', could not prove that the type
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Unit → False
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is nonempty.
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This process uses multiple strategies:
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- It looks for a parameter that matches the return type.
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- It tries synthesizing 'Inhabited' and 'Nonempty' instances for the return type, while making every parameter into a local 'Inhabited' instance.
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- It tries unfolding the return type.
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If the return type is defined using the 'structure' or 'inductive' command, you can try adding a 'deriving Nonempty' clause to it.
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sanitychecks.lean:22:12-22:20: error: (kernel) invalid declaration, it uses unsafe declaration 'unsafeCast'
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sanitychecks.lean:25:12-25:20: error: (kernel) invalid declaration, it uses unsafe declaration 'unsafeCast'
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