[GHC] #10747: Infix pattern synonyms fail to parse (regression)

[GHC]

#10747: Infix pattern synonyms fail to parse (regression)
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        Reporter:  heisenbug         |                Owner:
            Type:  bug               |               Status:  new
        Priority:  high              |            Milestone:  7.10.3
       Component:  Compiler          |              Version:  7.10.1
  (Parser)                           |             Keywords:
      Resolution:                    |  PatternSynonyms
Operating System:  Unknown/Multiple  |         Architecture:
 Type of failure:  GHC rejects       |  Unknown/Multiple
  valid program                      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
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Comment (by heisenbug):

 Replying to [comment:6 mpickering]:
 > I'm yet to look at this in detail but I suspect that this was never
 meant to work. I assumed that infix pattern synonyms definitions were
 meant to be like infix data constructor definitions.

 Then it should work:
 {{{
 $ ghci
 GHCi, version 7.11.20150928: http://www.haskell.org/ghc/  :? for help
 Prelude> data List a = Nil | a `Cons` List a deriving Show
 Prelude> 4 `Cons` Nil
 4 `Cons` Nil
 }}}
 This has been working for ages!

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10747#comment:7>
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