[GHC] #11186: Give strong preference to type variable names in scope when reporting hole contexts

[GHC]

#11186: Give strong preference to type variable names in scope when reporting hole
contexts
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        Reporter:  dfeuer            |                Owner:
            Type:  feature request   |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Compiler (Type    |              Version:  7.10.2
  checker)                           |
      Resolution:                    |             Keywords:  typed-holes
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by dfeuer):

 Replying to [comment:5 simonpj]:
 > And indeed, the same skolem bound in the pattern might have different
 lexical names in different places:
 > {{{
 > bla2 (Foop q) = ( (\(r::pah) -> length ([r] :: _x)) q
 >                 , (\(r::hap) -> length ([r] :: _y)) q )
 > }}}
 > Now what would you expect?

 I would expect the report about `_x` to tell me about `pah` and the one
 about `_y` to tell me about `hap`. May I ask what you think will be hard
 about this?

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11186#comment:7>
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