[GHC] #13602: Pattern syntax in expression context must be clarified

[GHC]

#13602: Pattern syntax in expression context must be clarified
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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 bgamari):

 Replying to [ticket:13602 vanto]:
 >
 > {{{let f = [True | x <- [_, _]]}}} raise the error
 > {{{pattern syntax in expression context: _}}}\\
 > But as Typed Holes, this error has no sense here.\\
 >
 > {{{let f' = [_ | x <- [1,2]]}}}will give a result like
 > {{{"__"}}} And this calculation also makes sense if one refers to the
 rule of inference, as the function
 > {{{f}}}
 > .\\

 I'm afraid I still don't follow. What, specifically, is the issue you want
 solved? It seems to have something to do with holes, but I can't discern
 what from your text.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13602#comment:1>
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