[GHC] #9611: Suggest the cause of "No instance" errors involving multiple versions of a package

[GHC]

#9611: Suggest the cause of "No instance" errors involving multiple versions of a
package
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        Reporter:  rwbarton          |                Owner:  Yuras
            Type:  feature request   |               Status:  merge
        Priority:  normal            |            Milestone:  8.0.1
       Component:  Compiler          |              Version:  7.8.3
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
 Type of failure:  Incorrect         |  Unknown/Multiple
  warning at compile-time            |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):  Phab:D1919
       Wiki Page:                    |
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Comment (by Simon Peyton Jones <simonpj@…>):

 In [changeset:"4c6e95e4f92516a925fd2a1bce0c0f8b5b9cbd17/ghc"
 4c6e95e4/ghc]:
 {{{
 #!CommitTicketReference repository="ghc"
 revision="4c6e95e4f92516a925fd2a1bce0c0f8b5b9cbd17"
 Small refactor and comments

 Related to the fix to Trac #9611
 }}}

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9611#comment:7>
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