[GHC] #11152: GND accepts ill-roled coercion when manually defining it won't typecheck

[GHC]

#11152: GND accepts ill-roled coercion when manually defining it won't typecheck
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        Reporter:  RyanGlScott       |                Owner:
            Type:  bug               |               Status:  closed
        Priority:  normal            |            Milestone:
       Component:  Compiler (Type    |              Version:  7.10.2
  checker)                           |
      Resolution:  invalid           |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
 Type of failure:  GHC accepts       |  Unknown/Multiple
  invalid program                    |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:  #9123             |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by goldfire):

 So, is there a bug here? I'm tempted to close, but I wanted to double-
 check.

 (And, yes, #9123 is a serious, open issue. I think there's a viable
 approach written up in the ticket, but it would need a fair bit of work --
 and quite possibly a research paper -- to sort out.)

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11152#comment:5>
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