[GHC] #15354: QuantifiedConstraints not fully described in manual

[GHC]

#15354: QuantifiedConstraints not fully described in manual
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           Reporter:  goldfire       |             Owner:  (none)
               Type:  bug            |            Status:  new
           Priority:  normal         |         Milestone:  8.6.1
          Component:  Documentation  |           Version:  8.5
           Keywords:                 |  Operating System:  Unknown/Multiple
       Architecture:                 |   Type of failure:  None/Unknown
  Unknown/Multiple                   |
          Test Case:                 |        Blocked By:
           Blocking:                 |   Related Tickets:
Differential Rev(s):                 |         Wiki Page:
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 As pointed out in comment:4:ticket:15351, the section in the manual on
 `-XQuantifiedConstraints` says that an `=>` is essential in a quantified
 constraint. However, the following is accepted:

 {{{#!hs
 class C a

 foo :: (forall x. C x) => ()
 foo = ()
 }}}

 Note that there is no `=>` in the quantified constraint. We need to update
 the manual accordingly.

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15354>
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