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@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@haskell.org] On Behalf Of Yitzchak Gale
| Sent: 10 May 2017 13:56
| To: GHC users <glasgow-haskell-users@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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