#11548: Absolutely misleading error message on kind error -------------------------------------+------------------------------------- Reporter: mniip | Owner: Type: bug | Status: new Priority: high | Milestone: Component: Compiler (Type | Version: 8.1 checker) | Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: Type of failure: Incorrect | Unknown/Multiple warning at compile-time | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Changes (by bgamari): * component: Compiler => Compiler (Type checker) Comment: Note that if you pass `-fprint-explicit-kinds` the error is a bit better (although arguably still not as clear as 7.10's error), {{{ Bug.hs:9:12: error: • Expected kind ‘Proxy * Maybe’, but ‘Data.Proxy.Proxy :: Proxy Maybe’ has kind ‘Proxy (* -> *) Maybe’ • In the first argument of ‘fun’, namely ‘(Proxy :: Proxy Maybe)’ In the expression: fun (Proxy :: Proxy Maybe) In an equation for ‘bug’: bug = fun (Proxy :: Proxy Maybe) }}} Of course, this isn't a great situation; surely the compiler can see that the types as printed are indistinguishable and it should therefore providing kinds as well. I'm not certain of this, but I suspect Richard is already aware of this issue. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/11548#comment:1 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler