[GHC] #8138: Core lint fails with error "Role incompatibility: expected N, got R"

[GHC]

#8138: Core lint fails with error "Role incompatibility: expected N, got R"
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       Reporter:  gmainland         |             Owner:
           Type:  bug               |            Status:  new
       Priority:  normal            |         Milestone:
      Component:  Compiler          |           Version:  7.7
       Keywords:                    |  Operating System:  Unknown/Multiple
   Architecture:  Unknown/Multiple  |   Type of failure:  Other
     Difficulty:  Unknown           |         Test Case:
     Blocked By:                    |          Blocking:
Related Tickets:                    |
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 I'm seeing a core lint error, "Role incompatibility: expected N, got R",
 on 333273792479695cf79a72cffa4c579d0c9deb21. The attached program will
 reproduce the error when compiled as:

 {{{
 ghc -O2 -dcore-lint Role.hs
 }}}

 Note that `-O2` is required for core lint to complain.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8138>
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