[GHC] #12367: Commit adding instances to GHC.Generics regression compiler performance

[GHC]

#12367: Commit adding instances to GHC.Generics regression compiler performance
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        Reporter:  bgamari           |                Owner:  bgamari
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:  8.0.2
       Component:  Compiler          |              Version:  8.0.1
      Resolution:                    |             Keywords:  Generics
Operating System:  Unknown/Multiple  |         Architecture:
 Type of failure:  Compile-time      |  Unknown/Multiple
  performance bug                    |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by bgamari):

 I've made a bit of progress tracking down the cause of GHC.Generics
 being loaded when looking for a `Foldable []` instance. It looks like
 the cause is the evaluation of the `mod` binding in
 IfaceEnv.instIsVisible. The RHS of this binding pulls on is_dfun to get
 its `idName` (which it only need the Module from).

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12367#comment:14>
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