[GHC] #11948: GHC forgets constraints

[GHC]

#11948: GHC forgets constraints
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        Reporter:  crockeea          |                Owner:
            Type:  bug               |               Status:  closed
        Priority:  normal            |            Milestone:  8.0.2
       Component:  Compiler          |              Version:  7.10.3
      Resolution:  fixed             |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  GHC rejects       |            Test Case:
  valid program                      |  typecheck/should_fail/T11948
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Changes (by simonpj):

 * testcase:   => typecheck/should_fail/T11948
 * status:  new => closed
 * resolution:   => fixed


Comment:

 OK I've added a warning for simplifiable class constraints.

 I anticipate a discussion about whether it should be on by default, but
 currently it is.

 Simon

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11948#comment:4>
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