#13774: Singletons code fails to typecheck when type signature involving type family is added -------------------------------------+------------------------------------- Reporter: RyanGlScott | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Compiler (Type | Version: 8.0.1 checker) | Keywords: FunDeps, Resolution: | TypeFamilies Operating System: Unknown/Multiple | Architecture: Type of failure: GHC rejects | Unknown/Multiple valid program | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by goldfire): I don't think this is related to those comments. To explain those comments: {{{ class C a b | a -> b where f :: a -> b class PC a b | a -> b where type F (x :: a) :: b }}} A use of `f` will trigger a need for a `C` instance. But a use of `F` won't. So, an inference that succeeds on terms fails on types. But that's not what's going on here. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/13774#comment:2 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler