#16248: ImplicitParams does not imply FlexibleContexts or FlexibleInstances -------------------------------------+------------------------------------- Reporter: NeilMitchell | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Documentation | Version: 8.6.3 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: {{{#!hs {-# LANGUAGE ImplicitParams #-} {-# LANGUAGE FlexibleInstances #-} module Test where data X a = X type XI = X Int class Foo a where foo :: (?p :: Int) => a -> Int instance Foo XI where foo = undefined }}} This code compiles. However, the documentation at https://downloads.haskell.org/~ghc/master/users-guide/glasgow_exts.html #language-options says that ImplicitParams implies FlexibleInstances, so we should be able to remove the FlexibleInstances extension. However, doing so makes it stop compiling. My guess is that ImplicitParams doesn't really imply either of the type class extensions, and that the documentation is buggy. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/16248 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler