#12820: Regression around pattern synonyms and higher-rank types -------------------------------------+------------------------------------- Reporter: goldfire | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler (Type | Version: 8.1 checker) | Resolution: | Keywords: 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 simonpj): Hmm. Works ok if you put the forall after the arrow {{{ pattern P x <- (((\ _ -> id) :: forall b. b -> forall c. c -> c) -> x) }}} Reason: we infer the type of `f`, and then try to decompose and arrow, instantiating if necessary. But we don't re-generalise. I suppose we could but this is a pretty exotic corner and it's not keeping me awake at night. Simon -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/12820#comment:3 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler