[GHC] #8959: GHCi should honour UnicodeSyntax

[GHC]

#8959: GHCi should honour UnicodeSyntax
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        Reporter:  Fuuzetsu    |            Owner:
            Type:  bug         |           Status:  closed
        Priority:  low         |        Milestone:  7.10.1
       Component:  Compiler    |          Version:  7.6.3
      Resolution:  fixed       |         Keywords:
Operating System:              |     Architecture:  Unknown/Multiple
  Unknown/Multiple             |       Difficulty:  Easy (less than 1 hour)
 Type of failure:              |       Blocked By:
  None/Unknown                 |  Related Tickets:
       Test Case:              |
        Blocking:              |
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Comment (by nomeata):

 Sigh: #3217 is not all there is to fix.

 Independent of GHCi we seem to want error messages from modules with
 `UnicodeSyntax` printed with that syntax. So we need to instrument `SDoc`
 in error messages with the settings from where the setting originated.

 The `dynflags` passed in `SDocContext` does not work for this, as they are
 the dynflags in scope when the error is printed, i.e. outside the module
 scope.

 There is precedence: The `PrintUnqualified` field of `ErrMsg` and later of
 `PprUser` transports information about how to pretty print stuff from the
 location of error to when its `SDoc` is rendered. I added a `Bool` there
 to indicate whether `UnicodeSyntax` should be used and it seems to work,
 but I’m not satisfied with this design.

 Stored the change in the `wip/T8959` branch, see
 [changeset:4a4e684f4/ghc].

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8959#comment:11>
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