[GHC] #6018: Injective type families

[GHC]

#6018: Injective type families
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              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:              |
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Comment (by goldfire):

 Simon's (very straightforward) example clarifies this in my mind -- I
 agree about just heading for plain old injectivity for open type families.
 If/when we want more involved reasoning for closed type families, where
 inference is possible, we can address that.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/6018#comment:59>
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