[GHC] #11028: Refactor ConDecl

[GHC]

#11028: Refactor ConDecl
-------------------------------------+-------------------------------------
        Reporter:  simonpj           |                Owner:  alanz
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Compiler          |              Version:  7.10.2
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
-------------------------------------+-------------------------------------

Comment (by alanz):

 Ok, the problem is in `rnConDecl` in the `ConDeclGADT` case, which in this
 branch simply calls `rnHsSigType`.

 Instead it should perform as per the original, which splits the result
 type,leaving it as `MaybeO ex t` in this case.

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11028#comment:22>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler