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

[GHC]

#15220: ScopedTypeVariables binds a non-existent variable
-------------------------------------+-------------------------------------
        Reporter:  goldfire          |                Owner:  (none)
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:  8.6.1
       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:                    |
-------------------------------------+-------------------------------------

Comment (by simonpj):

 > But I still think it would be very strange if zonkTcTypeToType ever
 zonked a SigTv to Any.

 I don't understand the question. In the example, `b` will not stand for a
 `SigTv` any more -- it'll stand for a `TauTv`, which can get unified with
 anything.

 I suppose we'll have to look at any remaining uses of `SigTv`.

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15220#comment:4>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler