[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):

 But you don't have `+v` in 8.0. The type that you're seeing has been
 instantiated and then regeneralized, so all the variable ordering has been
 forgotten. I still claim that the internal types assigned to `f` are the
 same. You just can't ask GHCi for this type in 8.0. You could, though do a
 `pprTrace` or `traceTc` from `TcExpr.tcInferId` which can print out the
 uninstantiated type.

 In your last sentence: that `k` really ought to be in scope throughout the
 type. If it's not, there's your bug!

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12549#comment:13>
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