[GHC] #13255: aws package fails to build with master

[GHC]

#13255: aws package fails to build with master
-------------------------------------+-------------------------------------
           Reporter:  bgamari        |             Owner:
               Type:  bug            |            Status:  new
           Priority:  highest        |         Milestone:  8.2.1
          Component:  Compiler       |           Version:  8.0.1
           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:
-------------------------------------+-------------------------------------
 The `aws` package from Hackage fails to build with `master`,
 {{{
 [22 of 76] Compiling Aws.DynamoDb.Core ( Aws/DynamoDb/Core.hs,
 /home/ben/code/mediawiki-annotate/dist-
 newstyle/build/x86_64-linux/ghc-8.1.20170209/aws-0.14.1/build/Aws/DynamoDb/Core.p_o
 )
 ghc: panic! (the 'impossible' happened)
   (GHC version 8.1.20170209 for x86_64-unknown-linux):
         completeCall
   $wloop_length_s18Cv
   Stop[BoringCtxt] Int# -> Int# -> Int
   Call stack:
       CallStack (from HasCallStack):
         prettyCurrentCallStack, called at
 compiler/utils/Outputable.hs:1188:58 in ghc:Outputable
         callStackDoc, called at compiler/utils/Outputable.hs:1192:37 in
 ghc:Outputable
         pprPanic, called at compiler/simplCore/Simplify.hs:1598:9 in
 ghc:Simplify

 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/13255>
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