[GHC] #15220: ScopedTypeVariables binds a non-existent variable

[GHC]

#15220: ScopedTypeVariables binds a non-existent variable
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        Reporter:  goldfire          |                Owner:  (none)
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:  8.8.1
       Component:  Compiler          |              Version:  8.5
      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 simonpj):

 Hmm.  What should happen to an unbound `TyVarTv` unification variable
 then?

 The presenting problem was with the old `SigTv`, when a scoped type
 variable could only be bound to a variable.  But we've changed that now -
 they are `TauTv`s.  I'm unsure about exactly how the remaining uses of
 `TyVarTv` work and whether this issue will arise at all. I suspect that it
 will not.

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15220#comment:11>
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