[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    |          Version:  7.9
  (Type checker)                     |         Keywords:
            Resolution:              |     Architecture:  Unknown/Multiple
      Operating System:              |       Difficulty:  Unknown
  Unknown/Multiple                   |       Blocked By:
       Type of failure:              |  Related Tickets:
  None/Unknown                       |
             Test Case:              |
              Blocking:              |
Differential Revisions:              |
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Comment (by simonpj):

 Great stuff.

  * I suggest making this a new data type, rather than simply replacing
 `TrieMap`.  The latter is simple, uniform, and efficient.  Let's not
 clutter it up!

  * But perhaps `TrieMap` itself can be modestly improved, by giving access
 to the key.

 Simon

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9805#comment:1>
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