GeneralizedNewtypeDeriving + MultiParamTypeClasses sends typechecker into an infinite loop
This worked in GHC 7.6.3, but ever since GHC 7.8, this code will cause the typechecker to loop infinitely:
{-# LANGUAGE FunctionalDependencies #-}
{-# LANGUAGE GeneralizedNewtypeDeriving #-}
{-# LANGUAGE MultiParamTypeClasses #-}
module Bug where
class C a b | a -> b where
c :: a -> Int
newtype Foo a = Foo a
deriving (C b)
Trac metadata
Trac field | Value |
---|---|
Version | 8.0.1 |
Type | Bug |
TypeOfFailure | OtherFailure |
Priority | normal |
Resolution | Unresolved |
Component | Compiler (Type checker) |
Test case | |
Differential revisions | |
BlockedBy | |
Related | |
Blocking | |
CC | |
Operating system | |
Architecture |