[GHC] #12389: Limit duplicate export warnings for datatypes

[GHC]

#12389: Limit duplicate export warnings for datatypes
-------------------------------------+-------------------------------------
        Reporter:  dfeuer            |                Owner:
            Type:  feature request   |               Status:  new
        Priority:  normal            |            Milestone:  8.2.1
       Component:  Compiler          |              Version:  7.10.3
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
 Type of failure:  Incorrect         |  Unknown/Multiple
  warning at compile-time            |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:  #11959            |  Differential Rev(s):
       Wiki Page:                    |
-------------------------------------+-------------------------------------

Comment (by dfeuer):

 Replying to [comment:1 rwbarton]:
 > Well the first `Foo` export certainly looks redundant (as long as at
 least one of the CPP flags is enabled).
 >
 > I don't really see how your second version is any better than what you
 say is "so horrible [...]":
 > {{{#!hs
 > module Foo (
 >    Foo (
 > #ifdef TESTING
 >      Foo,
 > #endif
 > #ifdef USE_PATTERN_SYNONYMS
 >      Pat1, Pat2,
 > #endif
 >    )
 >   )
 > }}}
 >
 > (A trailing comma is legal here right? Otherwise it really is a mess.)


 I don't know about GHC 8, but in 7.10, a trailing comma is *not* legal,
 and neither is a leading one.

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12389#comment:2>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler