[GHC] #16375: TypeApplications obscure "Variable not in scope" error message

1 Mar 2019

      #16375: TypeApplications obscure "Variable not in scope" error message
-------------------------------------+-------------------------------------
           Reporter:  roland         |             Owner:  (none)
               Type:  bug            |            Status:  new
           Priority:  normal         |         Milestone:
          Component:  Compiler       |           Version:  8.6.3
           Keywords:                 |  Operating System:  Unknown/Multiple
       Architecture:                 |   Type of failure:  None/Unknown
  Unknown/Multiple                   |
          Test Case:                 |        Blocked By:
           Blocking:                 |   Related Tickets:
Differential Rev(s):                 |         Wiki Page:
-------------------------------------+-------------------------------------
 Compiling

 {{{#!hs
 {-# LANGUAGE TypeApplications #-}

 module Foo where

 foo = bar @Int
 }}}

 gives

 {{{
 Foo.hs:5:7: error:
     • Cannot apply expression of type ‘t1’
       to a visible type argument ‘Int’
     • In the expression: bar @Int
       In an equation for ‘foo’: foo = bar @Int
 }}}

 instead of:
 {{{
 Foo.hs:5:7: error: Variable not in scope: bar
 }}}

 This makes a potential typo appear like a typing error (no pun intended).
 If we delete `@Int`, the second message is given.

-- 
Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/16375
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