30 Sep
2015
30 Sep
'15
6:04 p.m.
The type of a pattern synonym like pattern FOO = 1234 seems to be '(Eq a, Num a) => a', which makes partially makes sense, although it's not immediately clear to me where the 'Eq a' part comes from. But probably that would be clear if I read the desugaring rules closely enough. ;-) My real question is about: pattern FOO = 1234 :: Int This doesn't compile out of the box, GHC seems to require ScopedTypeVariables, too: Illegal type signature: `Int' Perhaps you intended to use ScopedTypeVariables In a pattern type-signature Why is this the case? From a user perspective, the error is totally bogus, there are no visible type variables at all. Can GHC be fixed to avoid enabling ScopedTypeVariables? Cheers, S.