[GHC] #4259: Relax restrictions on type family instance overlap

[GHC]

#4259: Relax restrictions on type family instance overlap
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    Reporter:  lilac                    |        Owner:              
        Type:  feature request          |       Status:  new         
    Priority:  normal                   |    Milestone:  7.4.1       
   Component:  Compiler (Type checker)  |      Version:  6.12.1      
    Keywords:                           |     Testcase:              
   Blockedby:                           |   Difficulty:              
          Os:  Unknown/Multiple         |     Blocking:              
Architecture:  Unknown/Multiple         |      Failure:  None/Unknown
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Comment(by basvandijk):

 Replying to [comment:12 simonpj]:
 > would it be enough to allow overlapping type family instances, but
 ''only if the overlapping ones were declared together'' (or at least in
 the same module)?

 Yes that would work here since both `newtype RegionStIO (RegionT s pr) α`
 and `newtype RegionStIO m α` are defined in the same module.

-- 
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/4259#comment:14>
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