[GHC] #15147: Type checker plugin receives Wanteds that are not completely unflattened

[GHC]

#15147: Type checker plugin receives Wanteds that are not completely unflattened
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        Reporter:  nfrisby           |                Owner:  (none)
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:  8.6.1
       Component:  Compiler (Type    |              Version:  8.4.1
  checker)                           |             Keywords:
      Resolution:                    |  TypeCheckerPlugins
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by adamgundry):

 Originally plugins would see flattened givens but unflattened wanteds
 (https://ghc.haskell.org/trac/ghc/wiki/Plugins/TypeChecker#Callingpluginsfromthetypechecker).
 The issue here is that the wanteds are now sometimes not fully
 unflattened, isn't it?

 If we were to provide only flattened wanteds, that might well be more
 consistent, but we're back to plugins needing to implement unflattening
 themselves...

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15147#comment:9>
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