[GHC] #6069: Rank 2 Polymorphism Compile Error

[GHC]

#6069: Rank 2 Polymorphism Compile Error
------------------------------------------+---------------------------------
  Reporter:  clinton                      |          Owner:  simonpj         
      Type:  bug                          |         Status:  closed          
  Priority:  normal                       |      Milestone:  7.8.1           
 Component:  Compiler                     |        Version:  7.4.1           
Resolution:  fixed                        |       Keywords:                  
        Os:  Unknown/Multiple             |   Architecture:  Unknown/Multiple
   Failure:  None/Unknown                 |     Difficulty:  Unknown         
  Testcase:  typecheck/should_fail/T6069  |      Blockedby:                  
  Blocking:                               |        Related:                  
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Changes (by simonpj):

  * status:  new => closed
  * testcase:  => typecheck/should_fail/T6069
  * resolution:  => fixed


Comment:

 Now all three fail, as they should, and fail in the same way:
 {{{
 T6069.hs:13:15:
     Couldn't match type `ST s0 Int' with `forall s. ST s b0'
     Expected type: ST s0 Int -> b0
       Actual type: (forall s. ST s b0) -> b0
     In the second argument of `(.)', namely `runST'
     In the expression: print . runST
     In the expression: (print . runST) fourty_two

 T6069.hs:14:15:
     Couldn't match type `ST s1 Int' with `forall s. ST s b1'
     Expected type: ST s1 Int -> b1
       Actual type: (forall s. ST s b1) -> b1
     In the second argument of `(.)', namely `runST'
     In the expression: (print . runST)
     In the expression: (print . runST) $ fourty_two

 T6069.hs:15:16:
     Couldn't match type `ST s2 Int' with `forall s. ST s b2'
     Expected type: ST s2 Int -> b2
       Actual type: (forall s. ST s b2) -> b2
     In the second argument of `(.)', namely `runST'
     In the first argument of `($)', namely `(print . runST)'
     In the expression: (print . runST) $
 }}}

-- 
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/6069#comment:5>
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