[GHC] #13557: error found hole: _ is not appropriate in the following case

[GHC]

#13557: error found hole: _ is not appropriate in the following case
-------------------------------------+-------------------------------------
        Reporter:  vanto             |                Owner:  (none)
            Type:  feature request   |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Compiler          |              Version:  8.0.2
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
 Type of failure:  Incorrect         |  Unknown/Multiple
  error/warning at compile-time      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
-------------------------------------+-------------------------------------

Comment (by vanto):

 Hi, the code above works well if we write the flag {{{-fdefer-typed-
 holes}}} in the command line.\\
 the result is correct and has a sense.\\
 To avoid under certain circumstances a nonsense I propose that Typed Holes
 are not always enabled in GHC.\\
 what do you think?

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13557#comment:3>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler