#9000: Kind checking fails when using PolyKinds -------------------------------------+------------------------------------- Reporter: facundo.dominguez | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler (Type | Version: 7.8.2 checker) | Operating System: Linux Keywords: | Type of failure: GHC rejects Architecture: x86_64 (amd64) | valid program Difficulty: Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | -------------------------------------+------------------------------------- GHC HEAD and earlier versions are failing on the following program: {{{ {-# LANGUAGE PolyKinds #-} import GHC.Exts(Any) f = (undefined :: a -> m a) :: Any -> Any Any }}} {{{ ../tmp/test-polykinds.hs:3:6: Couldn't match kind ‘k1’ with ‘*’ ‘k1’ is a rigid type variable bound by an expression type signature: Any -> Any Any at ../tmp/test-polykinds.hs:3:5 Expected type: Any -> Any Any Actual type: Any -> m0 Any In the expression: (undefined :: a -> m a) :: Any -> Any Any In an equation for ‘f’: f = (undefined :: a -> m a) :: Any -> Any Any }}} Rewriting the program as follows has compilation succeed. {{{ f = (undefined :: a -> m a) `asTypeOf` (undefined :: Any -> Any Any) }}} And removing the {{{PolyKinds}}} extension also has compilation succeed. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/9000 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler