[GHC] #9211: Untouchable type variable (regression from 7.6)

[GHC]

#9211: Untouchable type variable (regression from 7.6)
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        Reporter:  simonpj           |            Owner:
            Type:  bug               |           Status:  new
        Priority:  normal            |        Milestone:
       Component:  Compiler          |          Version:  7.8.2
      Resolution:                    |         Keywords:
Operating System:  Unknown/Multiple  |     Architecture:  Unknown/Multiple
 Type of failure:  None/Unknown      |       Difficulty:  Unknown
       Test Case:                    |       Blocked By:
        Blocking:                    |  Related Tickets:
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Comment (by oleg):

 Indeed I use the equality constraint to essentially let-bind a type
 variable, which is quite handy. I'm glad to hear that it is also easy to
 implement. I, too, am curious what Dimitrios thinks.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9211#comment:6>
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