#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