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

[GHC]

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

 {{{#!hs
 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.

 {{{#!hs
 (f =*= g) sa i = f (toF sa i) =^= g (toG sa i)
 }}}

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

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10269>
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