[GHC] #15497: Coercion Quantification

[GHC]

#15497: Coercion Quantification
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        Reporter:  ningning          |                Owner:  (none)
            Type:  task              |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Compiler          |              Version:
      Resolution:                    |             Keywords:  TypeInType
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):  Phab:D5054
       Wiki Page:                    |
  https://ghc.haskell.org/trac/ghc/wiki/DependentHaskell/Phase2|
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Comment (by ningning):

 I have looked through TcSimplify and 14584, but I am unsure I have
 understood fully the details. The logic seems delicate there. I know the
 motivation is

 {{{
 forall x[2].
    [W] co1: alpaha[1] ~ ty |> co2
    [W] co2: k1 ~ *
 }}}

 where we have the scope problem cause `co2` could mention `x` and `co1`
 depends on `co2`.

 What's the goal after we have coercion quantifications comparing to the
 current strategy??

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15497#comment:7>
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