[GHC] #12700: Don't warn about redundant constraints for type equalities

[GHC]

#12700: Don't warn about redundant constraints for type equalities
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        Reporter:  crockeea          |                Owner:
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Compiler          |              Version:  8.0.1
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
 Type of failure:  Incorrect         |  Unknown/Multiple
  warning at compile-time            |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by simonpj):

 I don't get what you mean by "the meaning changes".

 I understand that writing
 {{{
 foo :: (RealFrac a, Integral (Foo a)) => a -> Foo a
 }}}
 requires `FlexibleContexts` whereas the version you wrote does not; but
 that's not too terrible is it?  Maybe putting equalities in contexts
 should require `FlexibleContexts` too, since it's just as flexible.

 You say that "the function it suggests is the much more general...".  But
 the two are fully equivalent, so I don't know what you have in mind by
 "suggests" here.

 Would you care to elaborate?

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12700#comment:1>
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