#12046: AllowAmbiguousTypes doesn't work with UndecidableSuperClasses -------------------------------------+------------------------------------- Reporter: MikeIzbicki | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.0.1-rc3 (Type checker) | Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: None/Unknown Unknown/Multiple | Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- Given the code below, `test1` and `test2` are the same except the former has an ambiguous type and the latter does not. The compiler rejects the former and accepts the latter. {{{ {-# LANGUAGE UndecidableSuperClasses #-} {-# LANGUAGE AllowAmbiguousTypes #-} {-# LANGUAGE TypeFamilies #-} class A (T a) => A a where type T a test1 :: forall a. A a => () test1 = () test2 :: A a => proxy a -> () test2 _ = () }}} -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/12046 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler