[GHC] #7854: Constrained method type accepted in Haskell 98 mode

[GHC]

#7854: Constrained method type accepted in Haskell 98 mode
-------------------------------------+-------------------------------------
        Reporter:  refold            |                   Owner:  thomie
            Type:  bug               |                  Status:  closed
        Priority:  normal            |               Milestone:  7.12.1
       Component:  Compiler (Type    |                 Version:  7.6.3
  checker)                           |                Keywords:  newcomer
      Resolution:  fixed             |            Architecture:
Operating System:  Unknown/Multiple  |  Unknown/Multiple
 Type of failure:  None/Unknown      |               Test Case:
      Blocked By:                    |  module/mod39
 Related Tickets:  #10118, #10119    |                Blocking:
                                     |  Differential Revisions:  Phab:D688
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Comment (by simonpj):

 Well, bugs (and this was a bug) are like that!

 It's not so hard, and it is truthful, to add `ConstrainedClassMethods` to
 those libraries. But if the CLC advises, we can also make
 `FlexibleContexts` imply it.

 Remember this is not in 7.10 so libraries have time to adapt.

 Simon

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/7854#comment:20>
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