[GHC] #14703: T14507 testcase fragile due to unique exposed in error message

[GHC]

#14703: T14507 testcase fragile due to unique exposed in error message
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           Reporter:  bgamari        |             Owner:  (none)
               Type:  bug            |            Status:  new
           Priority:  normal         |         Milestone:
          Component:  Test Suite     |           Version:  8.4.1-alpha1
           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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 I noticed this failure in the CircleCI output:

 {{{#!patch
 --- ./patsyn/should_fail/T14507.run/T14507.stderr.normalised    2018-01-22
 18:57:32.381575253 +0000
 +++ ./patsyn/should_fail/T14507.run/T14507.comp.stderr.normalised
 2018-01-22 18:57:32.381575253 +0000
 @@ -2,7 +2,7 @@
  T14507.hs:18:9:
       Iceland Jack!  Iceland Jack! Stop torturing me!
        Pattern-bound variable x :: TypeRep a
 -        has a type that mentions pattern-bound coercion: co_a2CF
 +        has a type that mentions pattern-bound coercion: co_a2D4
        Hint: use -fprint-explicit-coercions to see the coercions
        Probable fix: add a pattern signature
       In the declaration for pattern synonym ‘SO’
 }}}

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14703>
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