[GHC] #12378: Not enough inlining happens with single-method type classes

[GHC]

#12378: Not enough inlining happens with single-method type classes
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           Reporter:  akio           |             Owner:
               Type:  bug            |            Status:  new
           Priority:  normal         |         Milestone:
          Component:  Compiler       |           Version:  8.0.1
           Keywords:                 |  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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 In the attached file, GHC produces code (with `-O2`) for `foo` that
 references a top-level definition of type `Small (Either () ())`, despite
 the fact that all bindings in the module are marked INLINE.

 If I use `-DOTHER_METHOD` to add another method to the class, this problem
 goes away. It looks like a ClassOp rule is helping here.

 I'm not sure if this is a bug, but it was a surprising behavior for me, so
 I'm reporting it. Please feel free to close this ticket if it's the
 correct behavior.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12378>
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