How to disable warning for "export item 'module ...' exports nothing"?

Sean Leather leather at
Thu Aug 14 14:00:25 EDT 2008

> I have a module A that re-exports module B, and module B contains only
>> class
>> instances. Since I'm using -Wall, I get this warning about module B
>> exporting nothing. Is there a way to disable this particular warning,
>> since
>> it is unnecessary in this case? No mailing list messages or GHC
>> documentation has told me what to do.
> Well, the warning is right that you don't need to re-export module B:
> instances are implicitly exported.  So you could just remove the export of
> "module B", unless there's a reason to export it (such as, you might add
> some exported functions or data types to it later)

Hmm, the disappointing result of removing module B from the export list is
that now it doesn't show up in the Haddock-generated documentation for
module A. Not that there was anything specific in B to document, because
it's only instances. But I do want the user to know that importing A also
imports B. Sigh... I suppose there's CPP if I really want it.

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