Apply bindings before returning unification mismatch error #1972
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nitinprakash96
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Jun 23, 2024
xsebek
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Jun 23, 2024
| deriving (Functor) | ||
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| instance Foldable Join where | ||
| foldMap :: Monoid m => (a -> m) -> Join a -> m |
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Not directly, but Foldable is a prerequisite of Traversable.
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Closes #1888. When we discovered a type mismatch, we were not fully substituting everything we had learned about the types (via
applyBindings) before reporting the error. For example, in #1888 we had2 : u1and a unification constraintu1 = Int -> u2, but we were just reporting the type of2asu1rather than first substitutingInt -> u2foru1.I think we have had this problem for a while, but the recent rewrite of the unification engine possibly made the effects more noticeable.
This incidentally improved a couple more error messages in the test suite. =)