Unused import warning on re-export

[Iavor Diatchki]

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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