#12652: Type checker no longer accepting code using function composition and rank-n types -------------------------------------+------------------------------------- Reporter: ezyang | Owner: simonpj Type: bug | Status: new Priority: normal | Milestone: 8.2.1 Component: Compiler (Type | Version: 8.1 checker) | Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by goldfire): The new behavior looks correct to me. `g`'s type expands to `Int -> (?x :: Int) => IO ()`, and it's critical that the `(?x :: Int)` bit does not get instantiated for this to type-check. Accordingly, the type parameters to `(.)` would have to be qualified types for this to work, so I say this is an improvement in behavior. Of course, it might just be time to extend the `($)` hack to work with `(.)`, too. Until we do so, though, we should reject the original program. Simon, what do you think? -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/12652#comment:4 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler