[GHC] #16315: Pattern synonym implicit existential quantification

[GHC]

#16315: Pattern synonym implicit existential quantification
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        Reporter:  int-index         |                Owner:  (none)
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Compiler          |              Version:  8.6.3
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by goldfire):

 You have a red herring in your soup.

 The following snippet is also accepted:

 {{{#!hs
 pattern P :: forall. () => forall k (a :: k). Proxy a -> T
 pattern P x = MkT (x :: Proxy (b :: j))
 }}}

 There's no scoping going on here, just the fact that these type variables
 are unconstrained.

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/16315#comment:7>
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