[GHC] #16391: "Quantified type's kind mentions quantified type variable" error with fancy-kinded GADT

[GHC]

#16391: "Quantified type's kind mentions quantified type variable" error with
fancy-kinded GADT
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        Reporter:  RyanGlScott       |                Owner:  (none)
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Compiler (Type    |              Version:  8.6.3
  checker)                           |
      Resolution:                    |             Keywords:  TypeInType
Operating System:  Unknown/Multiple  |         Architecture:
 Type of failure:  GHC rejects       |  Unknown/Multiple
  valid program                      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by simonpj):

 PS: here is a test caes that is rightly rejected by the test in
 `TcFValidity`.
 {{{
 type family T (r :: RuntimeRep) :: TYPE r

 foo :: T r
 foo = foo
 }}}
 It'd be good to add a note to `TcValidity` to show this example of how the
 test does something useful.

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/16391#comment:3>
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