[GHC] #10254: parser : the API annotation on opt_sig is being discarded

[GHC]

#10254: parser : the API annotation on opt_sig is being discarded
-------------------------------------+-------------------------------------
              Reporter:  alanz       |             Owner:  alanz
                  Type:  bug         |            Status:  new
              Priority:  normal      |         Milestone:  7.10.2
             Component:  Compiler    |           Version:  7.10.1
  (Parser)                           |  Operating System:  Unknown/Multiple
              Keywords:              |   Type of failure:  None/Unknown
  ApiAnnotations                     |        Blocked By:
          Architecture:              |   Related Tickets:
  Unknown/Multiple                   |
             Test Case:              |
              Blocking:              |
Differential Revisions:              |
-------------------------------------+-------------------------------------
 The `opt_sig` production is defined as

 {{{
 opt_sig :: { ([AddAnn],Maybe (LHsType RdrName)) }
         : {- empty -}                   { ([],Nothing) }
         | '::' sigtype                  { ([mj AnnDcolon $1],Just $2) }
 }}}

 It is used in the `alt` and `decl_no_th` productions, but neither of them
 add the returned annotations.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10254>
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