[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
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by AntC):

 Replying to [comment:1 Simon Peyton Jones <simonpj@…>]:
 > {{{
 > This is a documentation-only fix, addressing Trac #15354.
 > }}}

 Thanks Simon, is there a typo?

 {{{
     class ::= ...
              | [forall tyavrs .] [context =>] qtycls inst1 ... instn
              | [forall tyavrs .] [context =>] tyvar inst1 ... instn
 }}}
 should be `| [forall tyvars .] ...`? (I think this has come through from
 the github proposal.)

 So to know if some code is using `QuantifiedConstraints`: either there's a
 `context =>` or a `forall` (or both). If neither appear (despite having
 `{-# LANGUAGE QuantifiedConstraints #-}`), then it's a regular class
 appearing in a context, whatever "regular" means ;-).

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15354#comment:2>
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