Type synonym not normalized in instance head
Consider
{-# LANGUAGE ConstraintKinds, KindSignatures #-}
type Foo (m :: * -> *) = Monad m
data T a = T (Maybe a)
instance Foo T where
return = T Nothing
this gives the bogus error
T.hs:8:3: ‘return’ is not a (visible) method of class ‘Foo’
incidentally, it works okay when giving no where clause.
Trac metadata
Trac field | Value |
---|---|
Version | 7.8.2 |
Type | Bug |
TypeOfFailure | OtherFailure |
Priority | normal |
Resolution | Unresolved |
Component | Compiler |
Test case | |
Differential revisions | |
BlockedBy | |
Related | |
Blocking | |
CC | |
Operating system | |
Architecture |