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

[GHC]

#13854: the 'impossible' happened initTc: unsolved constraints
-------------------------------------+-------------------------------------
           Reporter:  bitemyapp      |             Owner:  (none)
               Type:  bug            |            Status:  new
           Priority:  normal         |         Milestone:
          Component:  Compiler       |           Version:  8.0.2
           Keywords:                 |  Operating System:  Unknown/Multiple
       Architecture:                 |   Type of failure:  Compile-time
  Unknown/Multiple                   |  crash or panic
          Test Case:                 |        Blocked By:
           Blocking:                 |   Related Tickets:
Differential Rev(s):                 |         Wiki Page:
-------------------------------------+-------------------------------------
 {{{
 [7 of 7] Compiling Texas.Api.OrderItems ( src/Texas/Api/OrderItems.hs,
 interpreted )
 ghc: panic! (the 'impossible' happened)
   (GHC version 8.0.2 for x86_64-unknown-linux):
         initTc: unsolved constraints
   WC {wc_insol =
         [W] OrderItemModified_a1mbC :: t_a1mbB[tau:1] (CHoleCan:
 OrderItemModified)
         [W] val_a1mbH :: t_a1mbG[tau:1] (CHoleCan: val)
         [W] runAccountDB_a1md0 :: t_a1mcZ[tau:1] (CHoleCan: runAccountDB)
         [W] getOrderItemsByOrderId_a1mdb :: t_a1mda[tau:1] (CHoleCan:
 getOrderItemsByOrderId)}

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

 I have what I believe is a repro of this error, albeit slightly different,
 located here: https://github.com/bitemyapp/panic-repro-initTc-unsolved-
 constraints

 {{{
 [3 of 3] Compiling Lib              ( src/Lib.hs, .stack-
 work/dist/x86_64-linux/Cabal-1.24.2.0/build/Lib.o )
 ghc: panic! (the 'impossible' happened)
   (GHC version 8.0.2 for x86_64-unknown-linux):
         initTc: unsolved constraints
   WC {wc_insol =
         [W] over_amEW :: t_amEV[tau:1] (CHoleCan: over)
         [W] ix_amF5 :: t_amF4[tau:1] (CHoleCan: ix)}

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

 This is the error I get there. If I learn more in the process of fixing
 the original code, I'll report it here. This panic occurs w/ GHC and GHCi.

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13854>
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