[GHC] #16110: Explicit foralls in associated type family defaults are completely ignored?

[GHC]

#16110: Explicit foralls in associated type family defaults are completely ignored?
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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 accepts       |  Unknown/Multiple
  invalid program                    |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by goldfire):

 You can say the last example in comment:3, but you both raise a good
 question. Do we need these at all? While the variables in the default
 equation can alpha-vary from other places (I forget why we decided to
 allow that), they must be bare variables, of the right kinds. So we really
 know their kinds from the type family declaration. There is no need to be
 able to write their kinds in the default equation.

 So perhaps the best way forward is just to remove the featurette.

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/16110#comment:4>
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