[GHC] #11071: "Not in scope" errors should be more informative for qualified names.

[GHC]

#11071: "Not in scope" errors should be more informative for qualified names.
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        Reporter:  mojojojo          |                Owner:  nomeata
            Type:  feature request   |               Status:  patch
        Priority:  normal            |            Milestone:  8.0.1
       Component:  Compiler          |              Version:  7.10.2
      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:D1462
       Wiki Page:                    |
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Comment (by thomie):

 Looking at the code, it doesn't seem too difficult to also improve the
 error message for cases (3) and (4) (from comment:5) when using
 //unqualified// imports.

 For example:
 {{{
 import Data.Map
 import Data.List hiding (transpose)

 f = transpose
 }}}

 This could show the same message as when `f = Data.List.transpose`:
 `"Perhaps you want to remove ‘transpose’ from the explicit hiding list in
 the import of ‘Data.List’"`, because only `Data.List` exports `transpose`;
 `Data.Map` doesn't.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11071#comment:10>
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