[GHC] #12092: Wrong error message with TypeApplications

20 May 2016

      #12092: Wrong error message with TypeApplications
-------------------------------------+-------------------------------------
           Reporter:  kwf            |             Owner:
               Type:  bug            |            Status:  new
           Priority:  normal         |         Milestone:
          Component:  Compiler       |           Version:  8.0.1
  (Type checker)                     |
           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:
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 When I write the following:

 {{{#!hs
 {-# language TypeApplications #-}

 module Bug where

 huh = spam @Int
 }}}

 I expect to get the error:

 {{{
     • Variable not in scope: spam
     • Perhaps you meant ‘span’ (imported from Prelude)
 }}}

 But instead, I get the error:

 {{{
     • Cannot apply expression of type ‘t0’
       to a visible type argument ‘Int’
     • In the expression: spam @Int
       In an equation for ‘huh’: huh = spam @Int
 }}}

 While it is //technically// true that I cannot apply an out-of-scope
 identifier to a visible type argument, this is probably the less useful
 error to receive.

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Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/12092
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