[GHC] #13838: -Wdeferred-type-errors on a program with main not of type IO () yields "main thread exited (uncaught exception)" (was: -Wdeferred-type-errors; ghc: panic!; VoidRep; ((() -> ()) :: *) ~# (IO Any :: *))

[GHC]

#13838: -Wdeferred-type-errors on a program with main not of type IO () yields
"main thread exited (uncaught exception)"
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        Reporter:  harry             |                Owner:  (none)
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Compiler          |              Version:  8.0.1
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
 Type of failure:  Compile-time      |  Unknown/Multiple
  crash or panic                     |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:  #13292            |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by RyanGlScott):

 Correct, that is entirely expected. To be clear: the GHC panic/Core Lint
 error bug exists in GHC 8.0.2, but not 8.2. However, a bug persists in GHC
 8.2 where actually running the code yields `main thread exited (uncaught
 exception)`, which shouldn't happen. I'll update the title accordingly.

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13838#comment:4>
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