[GHC] #12549: Panic on ":t datatypeName"

[GHC]

#12549: Panic on ":t datatypeName"
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        Reporter:  johnleo       |                Owner:  johnleo
            Type:  bug           |               Status:  new
        Priority:  normal        |            Milestone:
       Component:  Compiler      |              Version:  8.1
      Resolution:                |             Keywords:
Operating System:  MacOS X       |         Architecture:  x86_64 (amd64)
 Type of failure:  None/Unknown  |            Test Case:
      Blocked By:                |             Blocking:
 Related Tickets:                |  Differential Rev(s):
       Wiki Page:                |
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Comment (by goldfire):

 Instantiating variables in groups should be OK... but you should also keep
 track properly of what's in scope and what should be substituted during
 the instantiation. In other words, once the `k` has been instantiated,
 then you should apply the instantiating substitution to the entire body of
 `k`, including in the kinds of other bound variables.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12549#comment:15>
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