[GHC] #12124: Ambiguous type variable: it's a red herring!

[GHC]

#12124: Ambiguous type variable: it's a red herring!
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        Reporter:  drb226            |                Owner:
            Type:  bug               |               Status:  closed
        Priority:  normal            |            Milestone:  8.0.2
       Component:  Compiler          |              Version:  8.0.1
      Resolution:  fixed             |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |            Test Case:
                                     |  typecheck/should_fail/T12124
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by Simon Peyton Jones <simonpj@…>):

 In [changeset:"2fdf21bf26386ac5558ed5b95105bcf78e31f093/ghc" 2fdf21b/ghc]:
 {{{
 #!CommitTicketReference repository="ghc"
 revision="2fdf21bf26386ac5558ed5b95105bcf78e31f093"
 Further improve error handling in TcRn monad

 This patch builds on the one for Trac #12124, by dealing properly
 with out-of-scope "hole" errors.

 This fixes Trac #12529. The hard error coming from visible type
 application
 is still there, but the out-of-scope error is no longer suppressed.

 (Arguably the VTA message should be suppressed somehow, but that's a
 battle for another day.)
 }}}

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12124#comment:7>
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