Unused import warning on re-export

[Iavor Diatchki]

Actually, I just tried to make an example of this, and GHC does not seem to
export `f`, just as the report says.  So I'd say GHC is behaving correctly,
both with the exports and the warning.



On Fri, May 12, 2017 at 10:39 AM, Iavor Diatchki <iavor.diatchki at gmail.com>
wrote:

> Hello,
>
> actually, the bug here is that `f` is exported, as omitting the export
> list is not equivalent to writing `module A` in the export list.
>
> This is explicitly stated in Section 5.2 of the Haskell report:
>
>  "If the export list is omitted, all values, types and classes defined in
> the module are exported, but not those that are imported."
>
> -Iavor
>
>
>
>
>
>
>
>
>
> On Thu, May 11, 2017 at 1:23 PM, Simon Peyton Jones via
> Glasgow-haskell-users <glasgow-haskell-users at haskell.org> wrote:
>
>> | Is there a reason GHC considers this case an unused import? It seems
>> that
>> | the use of the import is explicitly stated right within the import
>> | itself. Should I submit a ticket for this?
>>
>> Hmm.  I think you are saying that
>>
>>   module A where
>>     import B as A(f)
>>     g = True
>>
>> that is equivalent to
>>    module A( module A ) where ...
>>
>> which exports all things "x" in scope as "A.x".  So it'll export both f
>> and g.
>>
>> But GHC will report f as unused, but not g. And that's inconsistent.
>> Fair point.  Yes, file a ticket.  Better still, offer a patch :-).
>>
>> Simon
>>
>> | -----Original Message-----
>> | From: Glasgow-haskell-users [mailto:glasgow-haskell-users-
>> | bounces at haskell.org] On Behalf Of Yitzchak Gale
>> | Sent: 10 May 2017 13:56
>> | To: GHC users <glasgow-haskell-users at haskell.org>
>> | Subject: Unused import warning on re-export
>> |
>> | I have a module A with no export list, and a function f which from the
>> | API point of view should part of the export list of A. But f must be
>> | defined in module B, not module A, due an import cycle. I added this
>> line
>> | in module A to re-export f from A:
>> |
>> | import B as A (f)
>> |
>> | This resulted in an unused import warning. That is a problem for us - we
>> | keep our large code base clean of warnings as a policy.
>> |
>> | Is there a reason GHC considers this case an unused import? It seems
>> that
>> | the use of the import is explicitly stated right within the import
>> | itself. Should I submit a ticket for this?
>> |
>> | Thanks,
>> | Yitz
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