Polymorphic kind annotations on type classes don't always work as expected
Consider the following code for defining Atkey-style parameterised monads:
{-# LANGUAGE
PolyKinds
#-}
class PMonad m where
ret :: a -> m i i a
bind :: m i j a -> (a -> m j k b) -> m i k b
class PMonad' (m :: i -> i -> * -> *) where
ret' :: a -> m i i a
bind' :: m i j a -> (a -> m j k b) -> m i k b
The following types are inferred for ret
and ret'
:
*Main> :t ret
ret :: PMonad * m => a -> m i i a
*Main> :t ret'
ret' :: PMonad' m => a -> m BOX BOX a
But ret'
should have the former type.
Trac metadata
Trac field | Value |
---|---|
Version | 7.6.1-rc1 |
Type | Bug |
TypeOfFailure | OtherFailure |
Priority | normal |
Resolution | Unresolved |
Component | Compiler (Type checker) |
Test case | |
Differential revisions | |
BlockedBy | |
Related | |
Blocking | |
CC | |
Operating system | |
Architecture |