[GHC] #13881: Inexplicable error message when using out-of-scope type variable in pattern type signature

[GHC]

#13881: Inexplicable error message when using out-of-scope type variable in pattern
type signature
-------------------------------------+-------------------------------------
        Reporter:  RyanGlScott       |                Owner:  (none)
            Type:  bug               |               Status:  merge
        Priority:  normal            |            Milestone:
       Component:  Compiler (Type    |              Version:  8.0.1
  checker)                           |
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  Poor/confusing    |            Test Case:
  error message                      |  typecheck/should_compile/T13881
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
-------------------------------------+-------------------------------------
Changes (by simonpj):

 * status:  new => merge
 * testcase:   => typecheck/should_compile/T13881


Comment:

 Great diagnosis, as ever.  All fixed.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13881#comment:3>
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