[GHC] #14887: Explicitly quantifying a kind variable causes a telescope to fail to kind-check

[GHC]

#14887: Explicitly quantifying a kind variable causes a telescope to fail to kind-
check
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        Reporter:  RyanGlScott       |                Owner:  goldfire
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:  8.8.1
       Component:  Compiler (Type    |              Version:  8.2.2
  checker)                           |
      Resolution:                    |             Keywords:  TypeInType
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 goldfire):

 I think the best way to get good error messages here is to bring both
 implicit and explicit variables into scope all at once, and then have
 `setImplicationStatus` report errors involving both explicit and implicit
 variables. See `Note [Keeping scoped variables in order: Explicit]` in
 !TcHsType for the general idea; here, I'm proposing this plan to cover
 implicit variables, too.

 One wrinkle: datatypes go via a different mechanism, in `kcLHsQTyVars` and
 friends. Question: could we unify these mechanisms?

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14887#comment:12>
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