[GHC] #10946: Typed hole inside typed Template Haskell bracket causes panic

[GHC]

#10946: Typed hole inside typed Template Haskell bracket causes panic
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        Reporter:  jstolarek         |                Owner:  (none)
            Type:  bug               |               Status:  new
        Priority:  high              |            Milestone:  8.4.1
       Component:  Template Haskell  |              Version:  7.10.1
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
 Type of failure:  Compile-time      |  Unknown/Multiple
  crash                              |            Test Case:  th/T10946
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by Tritlo):

 RyanGlScott: It seems like what's happening is that since the variable has
 no constraints on it at all, then it's matching everything in scope
 (including everything in scope in TemplateHaskell), and then doing the
 subsumption graph sorting on that, which takes a very long time. I'll give
 it some thought, but it seems like the right way to go would be to not try
 to find valid substitutions for this too general case.

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10946#comment:12>
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