[GHC] #10269: ApiAnnotations : RdrHsSyn.isFunLhs discards parentheses

[GHC]

#10269: ApiAnnotations : RdrHsSyn.isFunLhs discards parentheses
-------------------------------------+-------------------------------------
        Reporter:  alanz             |                   Owner:  alanz
            Type:  bug               |                  Status:  patch
        Priority:  normal            |               Milestone:  7.10.2
       Component:  Compiler          |                 Version:  7.10.1
      Resolution:                    |                Keywords:
Operating System:  Unknown/Multiple  |  ApiAnnotations
 Type of failure:  None/Unknown      |            Architecture:
      Blocked By:                    |  Unknown/Multiple
 Related Tickets:                    |               Test Case:
                                     |                Blocking:
                                     |  Differential Revisions:  Phab:D832
-------------------------------------+-------------------------------------

Comment (by Alan Zimmerman <alan.zimm@…>):

 In [changeset:"5bde9f7c1834ab4da1fad1838afec1a578c26530/ghc"]:
 {{{
 #!CommitTicketReference repository="ghc"
 revision="5bde9f7c1834ab4da1fad1838afec1a578c26530"
 ApiAnnotations : RdrHsSyn.isFunLhs discards parentheses

 Summary:
 The RdrHsSyn.isFunLhs function has the following

   isFunLhs e = go e []
    where
      go (L loc (HsVar f)) es
           | not (isRdrDataCon f)   = return (Just (L loc f, False, es))
      go (L _ (HsApp f e)) es       = go f (e:es)
      go (L _ (HsPar e))   es@(_:_) = go e es

 The treatment of HsPar means that any parentheses around an infix function
 will be discarded.

 e.g.

   (f =*= g) sa i = f (toF sa i) =^= g (toG sa i)

 will lose the ( before f and the closing one after g

 Test Plan: ./validate

 Reviewers: hvr, austin

 Reviewed By: austin

 Subscribers: bgamari, thomie

 Differential Revision: https://phabricator.haskell.org/D832

 GHC Trac Issues: #10269
 }}}

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10269#comment:4>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler