Re: [GHC] #9901: Error message: f is applied to two arguments, but its type has only two (sic)

26 Jan 2015

      #9901: Error message: f is applied to two arguments, but its type has only two
(sic)
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        Reporter:  zardoz            |                   Owner:
            Type:  bug               |                  Status:  new
        Priority:  normal            |               Milestone:
       Component:  Compiler (Type    |                 Version:  7.8.3
  checker)                           |                Keywords:
      Resolution:                    |            Architecture:
Operating System:  Unknown/Multiple  |  Unknown/Multiple
 Type of failure:  None/Unknown      |               Test Case:
      Blocked By:                    |                Blocking:
 Related Tickets:                    |  Differential Revisions:
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Comment (by zardoz):

 I’ve updated the attachment. Hopefully this should go through with just
 «base» installed.

 I’m out of my depth on the language pragmas. I added them as requested by
 GHC when mocking the respective types. The error message seems to be the
 same as before.

 This program yields me:

 {{{
 test.hs:22:17:
     Couldn't match type ‘Either String Int’ with ‘Maybe a0’
     Expected type: Either a1 [Char] -> Either String Int
       Actual type: Either a1 [Char] -> Maybe a0
     The function ‘preview’ is applied to two arguments,
     but its type ‘Getting (Data.Monoid.First a0) s0 a0
                   -> Either a1 [Char] -> Maybe a0’
     has only two
     In the second argument of ‘($)’, namely
       ‘(preview _Left (Right "abc") :: Either String Int)’
     In the expression:
       print $ (preview _Left (Right "abc") :: Either String Int)
 Failed, modules loaded: none.
 }}}

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Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/9901#comment:5
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