[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):

 On the other hand, this is the right behavior, since a type variable with
 no constraints on it could be substituted with any identifier of any type.
 So the time it is taking is really due to the bug giving the hole a too
 general type.

 simonpj: Yes, that's a good point. When we don't try to sort the
 substitution, that is indeed what happens. We should set some limit for
 how many substitutions we attempt to sort by the subsumption graph method,
 and default to some other method otherwise (like e.g. sorting by module).

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10946#comment:14>
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