#12384: Type family not reduced, again -------------------------------------+------------------------------------- Reporter: kosmikus | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.0.1 Resolution: | Keywords: Operating System: Linux | Architecture: Type of failure: GHC rejects | Unknown/Multiple valid program | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by alexvieth): #12381 and #11348 were all about the order in which instance declarations are checked, but this case seems to be something different. Here there's no choice but to check these declarations in the order that they're written: the type family, then the class, then the instance of that class. I suppose the type of `D ()` should be `(F a ~ Bool) => True` but as far as I know GHC can't handle such a thing. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/12384#comment:2 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler