[GHC] #9582: Associated Type Synonyms do not unfold in InstanceSigs

[GHC]

#9582: Associated Type Synonyms do not unfold in InstanceSigs
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              Reporter:              |            Owner:
  andreas.abel                       |           Status:  patch
                  Type:  bug         |        Milestone:
              Priority:  normal      |          Version:  7.8.3
             Component:  Compiler    |         Keywords:  InstanceSigs
  (Type checker)                     |  TypeFamilies
            Resolution:              |     Architecture:  Unknown/Multiple
      Operating System:              |       Difficulty:  Unknown
  Unknown/Multiple                   |       Blocked By:
       Type of failure:              |  Related Tickets:
  None/Unknown                       |
             Test Case:              |
              Blocking:              |
Differential Revisions:              |
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Comment (by simonpj):

 The hack is horrible!

 I suggest instead replacing the `CtOrigin` arg to `tcSubPat` with
 `BasicTypes.SwapFlag`.  If `NotSwapped` then `ty1` is acutal, `ty2` is
 expected; if `Swapped` then the other way round.

 That would make all the other calls more perspicuous too.

 Simon

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9582#comment:8>
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