[GHC] #13071: GHCi 8.0.1 panic with PatternSynonyms

[GHC]

#13071: GHCi 8.0.1 panic with PatternSynonyms
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           Reporter:  taktoa            |             Owner:
               Type:  bug               |            Status:  new
           Priority:  normal            |         Milestone:
          Component:  GHCi              |           Version:  8.0.1
           Keywords:  PatternSynonyms   |  Operating System:  Linux
       Architecture:  Unknown/Multiple  |   Type of failure:  GHCi crash
          Test Case:                    |        Blocked By:
           Blocking:                    |   Related Tickets:
Differential Rev(s):                    |         Wiki Page:
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 Loading this code:

 {{{#!hs
 {-# LANGUAGE PatternSynonyms #-}

 data D1 = MkD1 ()
 data D2 = MkD2 D1

 pattern P1 x = MkD1 x
 pattern P2 x = MkD2 (P1 x)
 }}}

 in GHCi 8.0.1 results in the following panic:

 {{{
 $ ghci Broken.hs
 GHCi, version 8.0.1: http://www.haskell.org/ghc/  :? for help
 [1 of 1] Compiling Main             ( Broken.hs, interpreted )
 ghc: panic! (the 'impossible' happened)
   (GHC version 8.0.1 for x86_64-unknown-linux):
         kindPrimRep.go rep_a18s

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

 >
 }}}

 The unique name in the error message (`rep_a18s`) seems to be consistent
 between executions, but varies after `:reload`ing.

 The panic does not occur when the module is simply compiled with `ghc`; it
 only occurs when loaded into `ghci`.

 According to ​Gergő Érdi, who is CCed, the error does not occur in GHCi
 7.10.3

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13071>
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