[GHC] #6018: Injective type families

[GHC]

#6018: Injective type families
-------------------------------------+-------------------------------------
              Reporter:  lunaris     |            Owner:  jstolarek
                  Type:  feature     |           Status:  new
  request                            |        Milestone:  7.10.1
              Priority:  normal      |          Version:  7.4.1
             Component:  Compiler    |         Keywords:  TypeFamilies,
            Resolution:              |  Injective
      Operating System:              |     Architecture:  Unknown/Multiple
  Unknown/Multiple                   |       Difficulty:  Unknown
       Type of failure:              |       Blocked By:
  None/Unknown                       |  Related Tickets:  #4259
             Test Case:              |
              Blocking:              |
Differential Revisions:  Phab:D202   |
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Comment (by jstolarek):

 > I don't know how to do this either. Luckily, we can reject E2 on a first
 pass.

 Yes, I believe that's what we should do. If we ever have analysis of
 unreachable equations for type families then we can use it to deal with
 `E2` but until then we should simply reject it.

 As for answers to 1-5 I'll read some more and get back if that doesn't
 help.

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/6018#comment:88>
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