[GHC] #12987: Core lint error with levity polymorphism

[GHC]

#12987: Core lint error with levity polymorphism
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        Reporter:  Iceland_jack      |                Owner:
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Compiler          |              Version:  8.0.1
      Resolution:                    |             Keywords:
                                     |  LevityPolymorphism
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by RyanGlScott):

 I can reproduce this in GHC 8.0.2, but not in GHC HEAD:

 {{{
 $ inplace/bin/ghc-stage2 --interactive
 GHCi, version 8.1.20161215: http://www.haskell.org/ghc/  :? for help
 Loaded GHCi configuration from /home/rgscott/.ghci
 λ> import GHC.Types
 λ> :set -XTypeInType -dcore-lint
 λ> class NUM (a :: TYPE rep) where add :: a -> a -> a
 λ> :t add
 add :: NUM a => a -> a -> a
 }}}

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12987#comment:1>
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