[GHC] #5267: Arrow command combinators

[GHC]

#5267: Arrow command combinators
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  Reporter:  peteg                        |          Owner:  ross            
      Type:  bug                          |         Status:  new             
  Priority:  normal                       |      Milestone:  7.4.1           
 Component:  Compiler                     |        Version:  7.0.3           
Resolution:                               |       Keywords:                  
  Testcase:                               |      Blockedby:                  
Difficulty:                               |             Os:  Unknown/Multiple
  Blocking:                               |   Architecture:  Unknown/Multiple
   Failure:  GHC accepts invalid program  |  
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Changes (by ross):

  * failure:  GHC rejects valid program => GHC accepts invalid program


Comment:

 Replying to [comment:12 simonpj]:
 > The key thing I don't know is: how long should nested tuple be.  We
 ''can't'' discover this by zonking the `tup_ty` and looking at it, because
 that won't work with suspended unification constraints.  It must surely be
 a lexical property of the code... ?

 Aye, there's the rub.  It's not a lexical property; the depth of this
 nested pair comes only from the type of the operator expression in the
 `ArrForm`.  If it helps, the only allowed possibilities at each point are
 a pair and the skolem type variable w.  (I realize that's one too many.)

-- 
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/5267#comment:13>
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