[GHC] #11039: Panic with incorrect pattern synonym signature

[GHC]

#11039: Panic with incorrect pattern synonym signature
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           Reporter:  mpickering     |             Owner:
               Type:  bug            |            Status:  new
           Priority:  high           |         Milestone:
          Component:  Compiler       |           Version:  7.11
           Keywords:                 |  Operating System:  Unknown/Multiple
       Architecture:                 |   Type of failure:  None/Unknown
  Unknown/Multiple                   |
          Test Case:                 |        Blocked By:
           Blocking:                 |   Related Tickets:
Differential Rev(s):                 |         Wiki Page:
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 {{{
 {-# LANGUAGE PatternSynonyms #-}
 module Foo () where

 data A a = A a

 pattern Q :: () => (A ~ f) => a -> f a
 pattern Q a = A a
 }}}

 error with HEAD

 {{{
 poly-export2.hs:7:9: error:ghc-stage2: panic! (the 'impossible' happened)
   (GHC version 7.11.20151030 for x86_64-apple-darwin):
         No skolem info: f_amp[sk]
 }}}

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11039>
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