[GHC] #11371: Bogus in-scope set in substitutions

[GHC]

#11371: Bogus in-scope set in substitutions
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        Reporter:  simonpj           |                Owner:  niteria
            Type:  bug               |               Status:  new
        Priority:  high              |            Milestone:  8.2.1
       Component:  Compiler          |              Version:  7.10.3
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:  #11360            |  Differential Rev(s):  phab:D1792,
       Wiki Page:                    |  phab:D1801, phab:D1802
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Comment (by Simon Peyton Jones <simonpj@…>):

 In [changeset:"4d031cf91c5eed9b162703daee274bbbe94bdc42/ghc" 4d031cf/ghc]:
 {{{
 #!CommitTicketReference repository="ghc"
 revision="4d031cf91c5eed9b162703daee274bbbe94bdc42"
 Improve piResultTys and friends

 Several things here:

 * Re-implement piResultTys so that its substitution has
   the correct in-scope set

   That means paying close attention to performance, since as we
   discovered in Trac #11371, it's a heavily used function and
   is often used on ordinary function types, with no foralls to
   worry about substituting.

 * Kill off applyTys, which was just the same as piResultTys.

 * Re-engineer MkCore.mkCoreApps so that it calls piResultTys,
   rather than repeatedly calling piResultTy.
 }}}

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11371#comment:49>
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