[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:  patch
        Priority:  normal            |            Milestone:
       Component:  Compiler          |              Version:  7.8.3
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):  Phab:D1919
       Wiki Page:                    |
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Comment (by Ben Gamari <ben@…>):

 In [changeset:"5fc06b97b320e98febaa925085dac03e5b01fc5a/ghc" 5fc06b9/ghc]:
 {{{
 #!CommitTicketReference repository="ghc"
 revision="5fc06b97b320e98febaa925085dac03e5b01fc5a"
 Suggest candidate instances in error message

 See Trac #9611. In "No instance..." error message we suggest instances
 for other types with the same occ name. It is usefull e.g. when we have
 two different versions of the same package installed.

 Test Plan: typecheck/should_fail/tcfail224

 Reviewers: austin, bgamari

 Reviewed By: bgamari

 Subscribers: thomie

 Differential Revision: https://phabricator.haskell.org/D1919

 GHC Trac Issues: #9611
 }}}

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9611#comment:5>
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