fix: bug at typeOccursCheck
#6104
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| visitMVar (mvarId' : MVarId) (numArgs : Nat := 0) : Bool := | ||
| if let some mvarDecl := mctx.findDecl? mvarId' then | ||
| occursCheck (skipAtMostNumBinders mvarDecl.type numArgs) | ||
| if let some b := skipAtMostNumBinders? mvarDecl.type numArgs then |
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Wouldn't it make more sense to get rid of skipAtMostNumBinders? altogether? Its only purpose now is to avoid doing the occurs check in some forall binder types. But not doing the type occurs check is exactly the bug we're trying to fix.
This PR fixes bug at `typeOccursCheck` that allowed cycles in the metavariable assignments. closes #6013
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This needed one extra type ascription in |
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Oh! The change required in Plausible is exactly what is now failing in the test |
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This PR does the same fix as #6104, but such that it doesn't break the test/the file in `Plausible`. This is done by not creating unused let binders in metavariable types that are made by `elimMVar`. (This is also a positive thing for users looking at metavariable types, for example in error messages) We get rid of `skipAtMostNumBinders`. This function was originally defined for the purpose of making this test work, but it is a hack because it allows cycles in the metavariable context. It would make sense to split these changes into 2 PRs, but I combined them here to show that the combination of them closes #6013 without breaking anything Closes #6013
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This PR fixes bug at
typeOccursCheckthat allowed cycles in the metavariable assignments.closes #6013