[GHC] #15252: syn_arg_wraps and syn_res_wrap are only populated after typechecking

[GHC]

#15252: syn_arg_wraps and syn_res_wrap are only populated after typechecking
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        Reporter:  mpickering        |                Owner:  (none)
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:  8.6.1
       Component:  Compiler          |              Version:  8.4.3
      Resolution:                    |             Keywords:  newcomer
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by Shayan-Najd):

 Thanks for reporting this.

 I also battled with this before. As far as I remember, all instances of
 `SyntaxExpr` should be considered as extensions.
 I am revisiting the current implementation of TTG to match
 [wiki:ImplementingTreesThatGrow/TreesThatGrowGuidance the idiom].
 I will close this ticket once I am done.

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15252#comment:3>
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