[GHC] #15346: Core Lint error in GHC 8.6.1: From-type of Cast differs from type of enclosed expression

[GHC]

#15346: Core Lint error in GHC 8.6.1: From-type of Cast differs from type of
enclosed expression
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        Reporter:  RyanGlScott       |                Owner:  (none)
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:  8.6.1
       Component:  Compiler (Type    |              Version:  8.5
  checker)                           |
      Resolution:                    |             Keywords:  TypeInType
Operating System:  Unknown/Multiple  |         Architecture:
 Type of failure:  Compile-time      |  Unknown/Multiple
  crash or panic                     |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by RyanGlScott):

 That being said, `Rep ()` should be equivalent to `U1`, so I don't
 understand why the Core Lint error happens in the first place.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15346#comment:1>
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