[GHC] #9109: Improve error messages around "untouchable" type variables

[GHC]

#9109: Improve error messages around "untouchable" type variables
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              Reporter:  goldfire    |            Owner:
                  Type:  bug         |           Status:  new
              Priority:  normal      |        Milestone:  7.10.1
             Component:  Compiler    |          Version:  7.8.2
            Resolution:              |         Keywords:
      Operating System:              |     Architecture:  Unknown/Multiple
  Unknown/Multiple                   |       Difficulty:  Unknown
       Type of failure:              |       Blocked By:
  None/Unknown                       |  Related Tickets:
             Test Case:              |
              Blocking:              |
Differential Revisions:              |
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Comment (by Richard Eisenberg <eir@…>):

 In [changeset:"cb41e08e4ce687356d1345ad6a1aa3555e505a59/ghc"]:
 {{{
 #!CommitTicketReference repository="ghc"
 revision="cb41e08e4ce687356d1345ad6a1aa3555e505a59"
 Test #9109 in typecheck/should_fail/T9109
 }}}

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9109#comment:6>
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