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

[GHC]

#13557: error found hole: _ is not appropriate in the following case
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        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:                    |
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Comment (by vanto):

 Hello Ben,\\
 In fact the cause does not come from Typed Holes in my opinion.\\
 We need to go back in the language implementation and redefine the role
 of underscore {{{_}}} in an expression.\\
 And hence Typed Holes will become clearer.\\
 See ticket {{{#13602}}} please.\\
 what do you think?\\

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13557#comment:5>
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