[GHC] #16116: Explicit foralls in associated type family equations are oblivious to class-bound variables

[GHC]

#16116: Explicit foralls in associated type family equations are oblivious to
class-bound variables
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        Reporter:  RyanGlScott       |                Owner:  (none)
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Compiler          |              Version:  8.7
      Resolution:                    |             Keywords:
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):

 We should reject egregious examples like
 {{{
 instance C [a] where
   type F Int = b
 }}}
 I hope we do -- and I hope we have a test that checks whether we do.

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/16116#comment:5>
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