[GHC] #10225: GHC does not specialize based on type equality

[GHC]

#10225: GHC does not specialize based on type equality
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        Reporter:  yongqli           |                   Owner:
            Type:  feature request   |                  Status:  new
        Priority:  normal            |               Milestone:
       Component:  Compiler          |                 Version:  7.10.1
      Resolution:                    |                Keywords:
Operating System:  Unknown/Multiple  |            Architecture:
 Type of failure:  None/Unknown      |  Unknown/Multiple
      Blocked By:                    |               Test Case:
 Related Tickets:                    |                Blocking:
                                     |  Differential Revisions:
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Comment (by simonpj):

 Can you give a concrete example of what you mean?  Does `f` need the fact
 that `(v ~ V2)`?  If not, I'm surprised that the former is slower than the
 latter. Can you give a test case?  The smaller the better

 Simon

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10225#comment:2>
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