[GHC] #13854: the 'impossible' happened initTc: unsolved constraints

[GHC]

#13854: the 'impossible' happened initTc: unsolved constraints
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        Reporter:  bitemyapp         |                Owner:  (none)
            Type:  bug               |               Status:  closed
        Priority:  normal            |            Milestone:
       Component:  Compiler          |              Version:  8.0.2
      Resolution:  duplicate         |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
 Type of failure:  Compile-time      |  Unknown/Multiple
  crash or panic                     |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:  #13106            |  Differential Rev(s):
       Wiki Page:                    |
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Changes (by RyanGlScott):

 * status:  new => closed
 * resolution:   => duplicate
 * related:   => #13106


Comment:

 Thanks for the bug report. This is a duplicate of #13106, which has been
 fixed in GHC 8.2.

 Note that this panic is usually caused by using identifiers that aren't
 in-scope (in your case, `over` and `ix`) in just the right way.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13854#comment:1>
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