[GHC] #10519: Can't put wildcard behind forall

[GHC]

#10519: Can't put wildcard behind forall
-------------------------------------+-------------------------------------
              Reporter:  yongqli     |             Owner:
                  Type:  bug         |            Status:  new
              Priority:  normal      |         Milestone:
             Component:  Compiler    |           Version:  7.10.1-rc3
              Keywords:              |  Operating System:  Unknown/Multiple
          Architecture:              |   Type of failure:  None/Unknown
  Unknown/Multiple                   |        Blocked By:
             Test Case:              |   Related Tickets:
              Blocking:              |
Differential Revisions:              |
-------------------------------------+-------------------------------------
 This type signature doesn't compile:

 {{{
 forall v. _
 => Acc (Array DIM2 (v Double))
 -> Acc (Array DIM2 (v Double))
 -> Acc (A.Vector Double)
 -> Acc (Array DIM2 Double)
 }}}

 with "Invalid partial type signature ... An extra-constraints wildcard is
 only allowed at the top-level of the signature"

 I need the forall because I use `v` in the body of the function.

 This occurs with version 7.10.1.20150612 but not 7.10.1.20150519

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10519>
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