Re: [GHC] #11548: Absolutely misleading error message on kind error

11 Sep 2016

      #11548: Absolutely misleading error message on kind error
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        Reporter:  mniip             |                Owner:  goldfire
            Type:  bug               |               Status:  new
        Priority:  high              |            Milestone:
       Component:  Compiler (Type    |              Version:  8.1
  checker)                           |
      Resolution:                    |             Keywords:  TypeInType
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:                    |
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Comment (by RyanGlScott):

 For reference, here is the current error message in GHC 8.0.1/HEAD:

 {{{
     • Couldn't match type ‘* -> *’ with ‘*’
       Expected type: Proxy Maybe
         Actual type: Proxy Maybe
       Use -fprint-explicit-kinds to see the kind arguments
     • 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)
 }}}

 I think this is much clearer, and doesn't incorrectly label the type as a
 kind.

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Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/11548#comment:7
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The Glasgow Haskell Compiler