[GHC] #821: implicit parameters and type synonyms

[GHC]

#821: implicit parameters and type synonyms
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  Reporter:  tullsen at galois.com  |          Owner:         
      Type:  support request     |         Status:  closed 
  Priority:  normal              |      Milestone:         
 Component:  Compiler            |        Version:  6.5    
  Severity:  normal              |     Resolution:  fixed  
  Keywords:                      |             Os:  Unknown
Difficulty:  Unknown             |   Architecture:  Unknown
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Changes (by simonpj):

  * resolution:  => fixed
  * status:  new => closed

Comment:

 Thanks for a useful report.  It alerted me to a shortcoming in our "boxy
 type inference paper" (on my home page).  GHC now supports impredicative
 polymorphism, but that had inadvertently made things worse here, as you
 pointed out.

 Fortunately, it was easily fixed, by using "pre-subsumption" in the main
 subsumption check as well as in "smart-app".  We'd missed that before.

 Test tc205 checks this case now.

 Simon

-- 
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/821>
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