[GHC] #13025: Type family reduction irregularity (change from 7.10.3 to 8.0.1)

[GHC]

#13025: Type family reduction irregularity (change from 7.10.3 to 8.0.1)
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        Reporter:  acowley           |                Owner:
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Compiler          |              Version:  8.0.1
      Resolution:                    |             Keywords:  TypeFamilies
Operating System:  Unknown/Multiple  |         Architecture:
 Type of failure:  Runtime           |  Unknown/Multiple
  performance bug                    |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by Simon Peyton Jones <simonpj@…>):

 In [changeset:"b4c3a66872a2b6e64fea9cc1f20ef4c8921ef7b6/ghc" b4c3a66/ghc]:
 {{{
 #!CommitTicketReference repository="ghc"
 revision="b4c3a66872a2b6e64fea9cc1f20ef4c8921ef7b6"
 Push coercions in exprIsConApp_maybe

 Trac #13025 showed up the fact that exprIsConApp_maybe isn't
 clever enough: it didn't push coercions through applicatins, and that
 meant we weren't getting as much superclass selection as we should.

 It's easy to fix, happily.

 See Note [Push coercions in exprIsConApp_maybe]
 }}}

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13025#comment:11>
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