[GHC] #12459: UnboxedTuple makes overloaded labels fail to parse

[GHC]

#12459: UnboxedTuple makes overloaded labels fail to parse
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        Reporter:  Iceland_jack      |                Owner:  adamgundry
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:  8.2.1
       Component:  Compiler          |              Version:  8.0.1
  (Parser)                           |
      Resolution:                    |             Keywords:  orf
Operating System:  Unknown/Multiple  |         Architecture:
 Type of failure:  GHC rejects       |  Unknown/Multiple
  valid program                      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by jberryman):

 Does this have much to do with overloaded labels? As rwbarton points out,
 it seems any occurence of "(#" has issues:

 {{{
 ubuntu at ip-172-31-8-51:~/work/ghc-my$ ghci
 GHCi, version 8.1.20160920: http://www.haskell.org/ghc/  :? for help
 Prelude> :set -XUnboxedTuples
 Prelude> let (#) = (+)

 <interactive>:2:7: error: parse error on input ‘)’
 }}}

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12459#comment:8>
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