[GHC] #11358: GHC generics has differing conFixity behavior between 7.10.3 and 8.1

[GHC]

#11358: GHC generics has differing conFixity behavior between 7.10.3 and 8.1
-------------------------------------+-------------------------------------
        Reporter:  RyanGlScott       |                Owner:  RyanGlScott
            Type:  bug               |               Status:  patch
        Priority:  high              |            Milestone:  8.0.1
       Component:  Compiler          |              Version:  8.1
  (CodeGen)                          |
      Resolution:                    |             Keywords:  Generics
Operating System:  Unknown/Multiple  |         Architecture:
 Type of failure:  Incorrect result  |  Unknown/Multiple
  at runtime                         |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):  Phab:D1740
       Wiki Page:                    |
-------------------------------------+-------------------------------------

Comment (by Ben Gamari <ben@…>):

 In [changeset:"852b603029a047609a54453b1f9cd65035a43afe/ghc"
 852b6030/ghc]:
 {{{
 #!CommitTicketReference repository="ghc"
 revision="852b603029a047609a54453b1f9cd65035a43afe"
 Restore old GHC generics behavior vis-à-vis Fixity

 Phab:D493 accidentally changed the way GHC generics looks up `Fixity`
 information when deriving `Generic` or `Generic1`. Before, a `Fixity` of
 `Infix` would be given only if a data constructor was declared infix,
 but now, `Infix` is given to any data constructor that has a fixity
 declaration (not to be confused with being declared infix!). This commit
 reverts back to the original behavior for consistency's sake.

 Fixes #11358.

 Test Plan: ./validate

 Reviewers: kosmikus, dreixel, austin, bgamari

 Reviewed By: bgamari

 Subscribers: thomie

 Differential Revision: https://phabricator.haskell.org/D1740

 GHC Trac Issues: #11358
 }}}

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11358#comment:3>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler