[GHC] #13749: Panic (initTc: unresolved constraints) on some bad code

[GHC]

#13749: Panic (initTc: unresolved constraints) on some bad code
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           Reporter:  uranium        |             Owner:  (none)
               Type:  bug            |            Status:  new
           Priority:  normal         |         Milestone:
          Component:  Compiler       |           Version:  8.0.2
           Keywords:                 |  Operating System:  Linux
       Architecture:                 |   Type of failure:  Compile-time
  Unknown/Multiple                   |  crash or panic
          Test Case:                 |        Blocked By:
           Blocking:                 |   Related Tickets:
Differential Rev(s):                 |         Wiki Page:
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 I was just refactoring some code, and partway through, before it was all
 compiling, I hit the below error.  The code's probably just terrible in an
 interestingly new way; I'm pretty inexperienced at Haskell.  I'll attach
 the file.

 Prelude> :r
 [1 of 1] Compiling Main             (
 /home/uranium/projects/server/src/Main.hs, interpreted )
 ghc: panic! (the 'impossible' happened)
   (GHC version 8.0.2 for x86_64-unknown-linux):
         initTc: unsolved constraints
   WC {wc_insol =
         [W] get_aGsK :: t_aGsJ[tau:1] (CHoleCan: get)
         [W] execState_aGsX :: t_aGsW[tau:1] (CHoleCan: execState)
         [W] get_aGvL :: t_aGvK[tau:1] (CHoleCan: get)
         [W] lift_aGvU :: t_aGvT[tau:1] (CHoleCan: lift)
         [W] put_aGw3 :: t_aGw2[tau:1] (CHoleCan: put)
         [W] cellType_aGwy :: t_aGwx[tau:1] (CHoleCan: cellType)
         [W] insts_aGwB :: t_aGwA[tau:1] (CHoleCan: insts)
         [W] ports_aGwE :: t_aGwD[tau:1] (CHoleCan: ports)
         [W] conns_aGwH :: t_aGwG[tau:1] (CHoleCan: conns)
         [W] annos_aGwK :: t_aGwJ[tau:1] (CHoleCan: annos)
         [W] comms_aGwN :: t_aGwM[tau:1] (CHoleCan: comms)}

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

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13749>
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