[GHC] #11345: Template Haskell's handling of infix GADT constructors is broken

[GHC]

#11345: Template Haskell's handling of infix GADT constructors is broken
-------------------------------------+-------------------------------------
        Reporter:  RyanGlScott       |                Owner:  RyanGlScott
            Type:  bug               |               Status:  patch
        Priority:  normal            |            Milestone:
       Component:  Template Haskell  |              Version:  8.1
      Resolution:                    |             Keywords:
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:D1744
       Wiki Page:                    |
-------------------------------------+-------------------------------------

Comment (by Ben Gamari <ben@…>):

 In [changeset:"0163427761c0e72a3acf09f854b3447f2e553f1b/ghc"
 01634277/ghc]:
 {{{
 #!CommitTicketReference repository="ghc"
 revision="0163427761c0e72a3acf09f854b3447f2e553f1b"
 Fix Template Haskell's handling of infix GADT constructors

 This is the second (and hopefully last) fix needed to make TH handle
 GADTs properly (after D1465). This Diff addresses some issues with infix
 GADT constructors, specifically:

 * Before, you could not determine if a GADT constructor was declared
   infix because TH did not give you the ability to determine if there is
   a //user-specified// fixity declaration for that constructor. The
   return type of `reifyFixity` was changed to `Maybe Fixity` so that it
   yields `Just` the fixity is there is a fixity declaration, and
   `Nothing` otherwise (indicating it has `defaultFixity`).
 * `DsMeta`/`Convert` were changed so that infix GADT constructors are
   turned into `GadtC`, not `InfixC` (which should be reserved for
   Haskell98 datatype declarations).
 * Some minor fixes to the TH pretty-printer so that infix GADT
   constructors will be parenthesized in GADT signatures.

 Fixes #11345.

 Test Plan: ./validate

 Reviewers: goldfire, austin, bgamari, jstolarek

 Reviewed By: jstolarek

 Subscribers: thomie

 Differential Revision: https://phabricator.haskell.org/D1744

 GHC Trac Issues: #11345
 }}}

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11345#comment:10>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler