Sean Leather wrote:
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.
You could put a link to the module in the
intro-documentation that comes before the export list,
possibly in a sentence saying e.g. "deliberately exports
instances from @module B@" (except I've forgotten Haddock
syntax and might have used it wrong there :-)
It's an interesting use-case though. I wonder if Haddock
should automatically provide links to all instances exported
from the module that are either (1) instances for datatypes
or classes exported by the module, or (2) orphan (i.e. not
defined in the same module as either the class or the
datatype). (It would be too tedious to list *all* exported
instances, but luckily it's not necessary for completeness.)
-Isaac
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