[GHC] #6018: Injective type families

[GHC]

#6018: Injective type families
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    Reporter:  lunaris                  |       Owner:                  
        Type:  feature request          |      Status:  new             
    Priority:  normal                   |   Milestone:                  
   Component:  Compiler                 |     Version:  7.4.1           
    Keywords:  TypeFamilies, Injective  |          Os:  Unknown/Multiple
Architecture:  Unknown/Multiple         |     Failure:  None/Unknown    
  Difficulty:  Unknown                  |    Testcase:                  
   Blockedby:                           |    Blocking:                  
     Related:                           |  
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Changes (by simonpj):

  * difficulty:  => Unknown


Comment:

 Some functions might be injective in one argument but not another.  For
 example:
 {{{
   F a b ~ F c d   ===>    a ~ c
                 but not   b ~ d
 }}}

-- 
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/6018#comment:2>
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