[GHC] #10828: TH could do a better job of representing GADTs

[GHC]

#10828: TH could do a better job of representing GADTs
-------------------------------------+-------------------------------------
        Reporter:  spinda            |                Owner:  jstolarek
            Type:  feature request   |               Status:  new
        Priority:  normal            |            Milestone:  8.0.1
       Component:  Template Haskell  |              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 goldfire):

 Replying to [comment:8 jstolarek]:
 > It is possible to automatically derive `Foldable` for all three
 declarations `T1`, `T2` and `T3`, both in GADT form as well as in the
 standard form given above, so `DerivingFoldable` makes no distinction
 between these three declarations.

 I agree that deriving `Foldable` works for all of them, but does it do the
 same thing? I would expect not, from the commentary on #10447.

 Your `GadtC` is missing a place for a `[TyVarBndr]` (to store the
 quantified type variables, both universals and existentials) and a `Cxt`
 to store any extra constraints. It also forbids record syntax, but maybe
 we can live without GADT record syntax.

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10828#comment:10>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler