[GHC] #7766: equality constraints exposed by patterns mess up constraint inference

GHC cvs-ghc at haskell.org
Wed Mar 13 13:47:54 CET 2013


#7766: equality constraints exposed by patterns mess up constraint inference
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Reporter:  heisenbug                  |          Owner:                  
    Type:  bug                        |         Status:  new             
Priority:  normal                     |      Component:  Compiler        
 Version:  7.7                        |       Keywords:                  
      Os:  Unknown/Multiple           |   Architecture:  Unknown/Multiple
 Failure:  GHC rejects valid program  |      Blockedby:                  
Blocking:                             |        Related:                  
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 When patterns bring (equality) constraints into scope, the inference
 mechanism for other (unrelated) constraints breaks down.

 This is a new problem that appeared between
    * ghc-7.7.20121025 and
    * ghc-7.7.20121114

 I can try to track down the commit if that helps.

 Testcase against HEAD attached.

-- 
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/7766>
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