[GHC] #8863: ghc 7.6.3: type parser accepts => as -> (sometimes)

[GHC]

#8863: ghc 7.6.3: type parser accepts => as -> (sometimes)
--------------------------+------------------------------------------------
       Reporter:          |             Owner:
  patrikj                 |            Status:  new
           Type:  bug     |         Milestone:
       Priority:  normal  |           Version:  7.6.3
      Component:          |  Operating System:  Linux
  Compiler                |   Type of failure:  GHC accepts invalid program
       Keywords:          |         Test Case:
   Architecture:  x86_64  |          Blocking:
  (amd64)                 |
     Difficulty:          |
  Unknown                 |
     Blocked By:          |
Related Tickets:          |
--------------------------+------------------------------------------------
 The following examples are all parsed and type checked even though they
 don't seem to be conforming to the Haskell standard syntax:

 a :: Int => Int
 a = (1+)

 b :: a -> a => a
 b = const

 c :: Num a => [a => a => a]
 c = [(+)]

 Slight variations fail (as the should) - for example

 b' :: a -> b => a
 b' = const

 /Patrik

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 Linux cse-814009 3.11.0-18-generic #32-Ubuntu SMP Tue Feb 18 21:11:14 UTC
 2014 x86_64 x86_64 x86_64 GNU/Linux

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8863>
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