[GHC] #11224: Program doesn't preserve semantics after pattern synonym inlining.

[GHC]

#11224: Program doesn't preserve semantics after pattern synonym inlining.
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        Reporter:  anton.dubovik     |                Owner:
            Type:  bug               |               Status:  new
        Priority:  highest           |            Milestone:  8.0.1
       Component:  Compiler          |              Version:  7.10.2
      Resolution:                    |             Keywords:
                                     |  PatternSynonyms
Operating System:  Windows           |         Architecture:  x86_64
 Type of failure:  Incorrect result  |  (amd64)
  at runtime                         |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:  #11225            |  Differential Rev(s):  Phab:D1632
       Wiki Page:                    |
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Comment (by rvion):

 Hello,

 will expressions like:

 {{{
 module Data.Aeson.Types.AsJs where
 import qualified Data.Aeson.Types as I
 pattern JsOptions a b c d e <- I.Options a b c d e
 }}}

 keep working correctly after this fix ?

 I use patterns a lot to automatically reexport "qualified" modules. (WIP
 project)
 see example here:
 https://github.com/rvion/ride/blob/94767d043b33fa5702852fba384b4e6dcf4007a5/jetpack/src/Data/Aeson/Types/AsJs.hs#L38
 or here:
 https://github.com/rvion/ride/blob/94767d043b33fa5702852fba384b4e6dcf4007a5/jetpack/src/Codec/Archive/Tar/AsTar.hs#L44

 Otherwise, according to http://mpickering.github.io/posts/2015-12-12
 -pattern-synonyms-8.html, most of my remaining issues seems to be solved
 in HEAD, thanks very much for all those great enhancements!

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11224#comment:18>
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