[GHC] #16233: HIE file generation is inefficient

[GHC]

#16233: HIE file generation is inefficient
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        Reporter:  harpocrates       |                Owner:  (none)
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Compiler          |              Version:  8.7
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:  #15320            |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by harpocrates):

 Since 5ed48d25decc9dec29659482644b136cff91606e, we avoid most of the
 expensive calls to `deSugarExpr`.

 For a handful of expressions (ex: `HsLam`), the type already exists in the
 extensions field, so we use that. For some other expressions that are
 prone to the quartic desugaring performance (eg. `HsApp`), we've just
 disabled getting their type information completely for now. The rest (ex.
 `HsVar`), we still perform the desugaring.

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/16233#comment:2>
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