[GHC] #9960: Performance problem with TrieMap

[GHC]

#9960: Performance problem with TrieMap
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        Reporter:  simonpj           |                   Owner:
            Type:  bug               |                  Status:  new
        Priority:  normal            |               Milestone:
       Component:  Compiler          |                 Version:  7.8.4
      Resolution:                    |                Keywords:
Operating System:  Unknown/Multiple  |            Architecture:
 Type of failure:  None/Unknown      |  Unknown/Multiple
      Blocked By:                    |               Test Case:
 Related Tickets:                    |                Blocking:
                                     |  Differential Revisions:  Phab:D606
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Comment (by ezyang):

 One subtlety: `eqTypeModuloDeBruijn` needs to respect equivalence by
 `coreView`, because that's how TrieMaps work too.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9960#comment:4>
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