[GHC] #12529: Error message: visible type application of constructor/variable that is not in scope

[GHC]

#12529: Error message: visible type application of constructor/variable that is not
in scope
-------------------------------------+-------------------------------------
        Reporter:  Iceland_jack      |                Owner:
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Compiler          |              Version:  8.0.1
      Resolution:                    |             Keywords:
                                     |  TypeApplications
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:                    |
-------------------------------------+-------------------------------------

Comment (by goldfire):

 The fact that GHC treats out-of-scope errors as type errors causes
 degradation of certain error messages, like what you see here. I'm sure
 there's another ticket tracking this problem, but I'm unable to find it at
 the moment. Perhaps you can? If I recall, the original error message was
 about a lack of class instances.

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12529#comment:2>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler