[GHC] #9191: Semi-exported names

[GHC]

#9191: Semi-exported names
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        Reporter:  dfeuer            |            Owner:
            Type:  feature request   |           Status:  new
        Priority:  low               |        Milestone:
       Component:  Compiler          |          Version:  7.8.2
      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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Description changed by dfeuer:

Old description:

> It's generally inadvisable to add exports to a well-known module because
> they may clash with existing code using the module and importing it in
> its entirety. As a work-around, I propose allowing a module to export a
> name that will only be visible in a module that lists it explicitly.
> Something approximately like
>
> module Foo (a, b, explicit c)
>
> simply
>
> import Foo
>
> would not bring c into scope, but
>
> import Foo (c)
>
> would bring in c (and nothing else). To get everything, we could use
> something like
>
> import Foo revealing (c)
>
> and to be a bit picky,
>
> import Foo hiding (a) revealing (c).

New description:

 It's generally inadvisable to add exports to a well-known module because
 they may clash with existing code using the module and importing it in its
 entirety. As a work-around, I propose allowing a module to export a name
 that will only be visible in a module that lists it explicitly. If we had

 module Foo (a, b, hidden c)

 then simply

 import Foo

 would not bring c into scope, but

 import Foo (c)

 would bring in c (and nothing else). To get everything, we could use
 something like

 import Foo revealing (c)

 and to be a bit picky,

 import Foo hiding (a) revealing (c).

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9191#comment:2>
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