#11977: ghc doesn't agree with its own inferred pattern type -------------------------------------+------------------------------------- Reporter: Iceland_jack | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.1 Resolution: | Keywords: | PatternSynonyms 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 Iceland_jack): Here's is an odd thing, it works if you quantify it! {{{#!hs -- Doesn't work! -- pattern F :: b -> forall x. Char -> b -- pattern F a <- (($ 'a') -> a) -- Does work for some reason pattern F1 :: b -> forall x. Char -> b pattern F1 a <- (($ 'a') -> a) -- Wait what? pattern F2 :: b -> forall b. Char -> b pattern F2 a <- (($ 'a') -> a) }}} How does this play out {{{#!hs -- Inferred type f1 :: (forall (x :: k). Char -> b) -> b f1 (F1 x) = x -- Works exactly like: -- -- f1 (($ 'a') -> x) = x -- f1 :: (Char -> b) -> b f1 (F1 x) = x }}} with `F2`: {{{#!hs f2 :: (forall b. Char -> b) -> b1 f2 (F2 x) = ... }}} -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/11977#comment:6 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler