[GHC] #8782: Using GADT's to maintain invariant in GHC libraries

[GHC]

#8782: Using GADT's to maintain invariant in GHC libraries
-------------------------------------+-------------------------------------
              Reporter:              |            Owner:
  Iceland_jack                       |           Status:  infoneeded
                  Type:  task        |        Milestone:  7.10.1
              Priority:  lowest      |          Version:  7.9
             Component:  Compiler    |         Keywords:
            Resolution:              |     Architecture:  Unknown/Multiple
      Operating System:              |       Difficulty:  Unknown
  Unknown/Multiple                   |       Blocked By:
       Type of failure:              |  Related Tickets:
  None/Unknown                       |
             Test Case:              |
              Blocking:              |
Differential Revisions:              |
-------------------------------------+-------------------------------------
Changes (by thoughtpolice):

 * status:  patch => infoneeded
 * milestone:   => 7.10.1


Comment:

 Iceland_Jack, now that HEAD requires 7.6 to bootstrap
 (527bcc41630918977c73584d99125ff164400695), I think this change can go in
 as long as the patch is changed to use an actual open type family. Would
 you mind doing that, and also submitting the patch in `git` format (Note
 you'll also need some minor changes like instances, see
 93b1a43ebe8bf145b35e903966d4a62b7847f213)? That would be great.

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8782#comment:3>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler