[GHC] #9805: Use TrieMaps to speed up type class instance lookup

[GHC]

#9805: Use TrieMaps to speed up type class instance lookup
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        Reporter:  ezyang            |                Owner:  ezyang
            Type:  task              |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Compiler (Type    |              Version:  7.9
  checker)                           |
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by ezyang):

 It's been two years since I last poked this, and since then Richard
 Eisenberg merged kind equalities. This means that the match implementation
 I prototyped no longer works: matching has been rolled up with a very
 general unification algorithm, which keeps track of kind coercions so that
 the resulting substitutions are well typed. So I am uncertain whether or
 not we can still carve out the "matching" portion of the algorithm without
 having to handle all of this extra logic.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9805#comment:12>
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