
#11540: ghc accepts non-standard type without language extension -------------------------------------+------------------------------------- Reporter: augustss | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.8.4 (Parser) | 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 rwbarton): If we want to control this with a language extension, then `Rank2Types`/`RankNTypes` should be a good choice. After all we already have {{{ Prelude> let f :: a -> Eq a => a; f = undefined <interactive>:4:10: Illegal polymorphic or qualified type: Eq a => a Perhaps you intended to use RankNTypes or Rank2Types In the type signature for âfâ: f :: a -> Eq a => a }}} -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/11540#comment:2 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler