[GHC] #13689: Data.Either doesn't export INLINABLE short functions like "rights"

[GHC]

#13689: Data.Either doesn't export INLINABLE short functions like "rights"
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        Reporter:  varosi            |                Owner:  (none)
            Type:  bug               |               Status:  patch
        Priority:  normal            |            Milestone:
       Component:  Core Libraries    |              Version:  8.0.2
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
 Type of failure:  Incorrect API     |  Unknown/Multiple
  annotation                         |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):  Phab:D3576
       Wiki Page:                    |
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Comment (by bgamari):

 varosi, the problem is that GHC considers the definitions of `lefts` and
 `rights` to be too large to inline and consequently doesn't produce
 unfoldings for them when compiling `GHC.Eithers`. This means that by the
 time we get to compiling your code we couldn't inline `lefts` and `rights`
 even if we wanted to.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13689#comment:21>
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