[GHC] #8278: Improve error message when the same type is imported from two different library versions

[GHC]

#8278: Improve error message when the same type is imported from two different
library versions
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        Reporter:  Yuras             |            Owner:
            Type:  feature request   |           Status:  new
        Priority:  normal            |        Milestone:
       Component:  Compiler          |          Version:  7.6.3
      Resolution:                    |         Keywords:
Operating System:  Unknown/Multiple  |     Architecture:  Unknown/Multiple
 Type of failure:  None/Unknown      |       Difficulty:  Unknown
       Test Case:                    |       Blocked By:
        Blocking:                    |  Related Tickets:
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Comment (by Simon Peyton Jones <simonpj@…>):

 In [changeset:"2403fa102559e81d665838a62b2a5de3229a9783/ghc"]:
 {{{
 #!CommitTicketReference repository="ghc"
 revision="2403fa102559e81d665838a62b2a5de3229a9783"
 Improve printing of errors when the tycons look the same

 See Trac #8278.  Example new message:

     Couldn't match expected type ‛T8278a.Maybe’
                 with actual type ‛Maybe a0’
     NB: ‛T8278a.Maybe’ is defined in ‛T8278a’
         ‛Maybe’ is defined in ‛Data.Maybe’ in package ‛base’
     In the first argument of ‛f’, namely ‛Nothing’

 The "NB" is the new bit
 }}}

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8278#comment:3>
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