[GHC] #11711: Typechecker assertion failure

[GHC]

#11711: Typechecker assertion failure
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        Reporter:  bgamari           |                Owner:
            Type:  bug               |               Status:  new
        Priority:  high              |            Milestone:  8.0.1
       Component:  Compiler (Type    |              Version:  8.0.1-rc2
  checker)                           |
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
 Type of failure:  Compile-time      |  Unknown/Multiple
  crash                              |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by Richard Eisenberg <eir@…>):

 In [changeset:"b5565f1a79fd24fc45a6f1a58821a317852d4b89/ghc" b5565f1/ghc]:
 {{{
 #!CommitTicketReference repository="ghc"
 revision="b5565f1a79fd24fc45a6f1a58821a317852d4b89"
 Fix #11711.

 There were two bugs here, both simple: we need to filter out
 covars before calling isMetaTyVar in the solver, and TcPat had
 a tcSubType the wrong way round.

 test case: dependent/should_compile/T11711
 }}}

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11711#comment:7>
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