[GHC] #15954: LiberalTypeSynonyms unsaturation check doesn't kick in

[GHC]

#15954: LiberalTypeSynonyms unsaturation check doesn't kick in
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        Reporter:  RyanGlScott       |                Owner:  (none)
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:  8.6.3
       Component:  Compiler (Type    |              Version:  8.6.2
  checker)                           |
      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 RyanGlScott):

 Here is another example which doesn't require `ImpredicativeTypes`,
 `PolyKinds`, or visible dependent quantification:

 {{{#!hs
 {-# LANGUAGE KindSignatures #-}
 {-# LANGUAGE RankNTypes #-}
 module Bug where

 import Data.Kind

 type A a = Int
 type B (a :: Type -> Type) = forall x. x -> x
 type C = B A
 }}}

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15954#comment:1>
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