#7082: Default type family instances
---------------------------------------+------------------------------------
Reporter: guest | Owner:
Type: bug | Status: new
Priority: normal | Component: Compiler (Type
checker)
Version: 7.4.1 | Keywords:
Os: Unknown/Multiple | Architecture: Unknown/Multiple
Failure: GHC rejects valid program | Testcase:
Blockedby: | Blocking:
Related: |
---------------------------------------+------------------------------------
The following code does not compile in GHC 7.4, unless line (2) is
uncommented. I thought line (1) would remove need for (2). If it does not,
probably declaration (1) should cause an error.
{{{
{-# LANGUAGE TypeFamilies #-}
class R m where
type D m a :: *
type D m a = () -- (1)
f :: m a -> D m a -> ()
instance R Maybe where
-- type D Maybe a = () -- (2)
f = undefined
x = f (Nothing :: Maybe Int) ()
}}}
--
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/7082>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler
_______________________________________________
Glasgow-haskell-bugs mailing list
Glasgow-haskell-bugs@haskell.org
http://www.haskell.org/mailman/listinfo/glasgow-haskell-bugs
