[GHC] #14040: Typed holes regression in GHC 8.0.2: No skolem info: z_a1sY[sk:2]

[GHC]

#14040: Typed holes regression in GHC 8.0.2: No skolem info: z_a1sY[sk:2]
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        Reporter:  RyanGlScott       |                Owner:  (none)
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Compiler (Type    |              Version:  8.0.2
  checker)                           |             Keywords:  TypeInType,
      Resolution:                    |  TypeFamilies, PartialTypeSignatures
Operating System:  Unknown/Multiple  |         Architecture:
 Type of failure:  Compile-time      |  Unknown/Multiple
  crash or panic                     |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:  #13877            |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by RyanGlScott):

 Interestingly, the original program no longer panics on GHC HEAD, but the
 program in comment:2 still panics, this time with a slightly different
 panic:

 {{{
 GHCi, version 8.5.20171205: http://www.haskell.org/ghc/  :? for help
 Loaded GHCi configuration from /home/rgscott/.ghci
 [1 of 1] Compiling Bug              ( Bug.hs, interpreted )

 Bug.hs:56:28: error:ghc-stage2: panic! (the 'impossible' happened)
   (GHC version 8.5.20171205 for x86_64-unknown-linux):
         No skolem info:
   [a1_a1yY[sk:1]]
   Call stack:
       CallStack (from HasCallStack):
         callStackDoc, called at compiler/utils/Outputable.hs:1150:37 in
 ghc:Outputable
         pprPanic, called at compiler/typecheck/TcErrors.hs:2892:5 in
 ghc:TcErrors

 Please report this as a GHC bug:  http://www.haskell.org/ghc/reportabug
 }}}

 Is it worth adding a regression test for the original program, or should I
 wait until the program in comment:2 has been fixed as well?

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14040#comment:3>
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