[GHC] #9834: GHC panic when used with deferred type errors

[GHC]

#9834: GHC panic when used with deferred type errors
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              Reporter:              |            Owner:
  Iceland_jack                       |           Status:  new
                  Type:  bug         |        Milestone:
              Priority:  normal      |          Version:  7.8.2
             Component:  Compiler    |         Keywords:
  (Type checker)                     |     Architecture:  Unknown/Multiple
            Resolution:              |       Difficulty:  Unknown
      Operating System:  Linux       |       Blocked By:
       Type of failure:  GHCi crash  |  Related Tickets:
             Test Case:              |
              Blocking:              |
Differential Revisions:              |
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Comment (by jstolarek):

 I just checked and I'm getting a panic on my branch forked from HEAD 5
 days ago. So if the fix indeed went into HEAD it must be really recent. I
 tried cherry-picking 2cc854b7133e38c7ad1107057931761782d03594 onto my
 branch because it does typed-holes-related stuff but that doesn't fix the
 panic.

 I also confirmed that this happens with GHC 7.8.4:

 Aside: To get the reported test case compiling with HEAD I had to change
 `import Control.Monad.Identity` to `import Data.Functor.Identity`.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9834#comment:3>
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