(Imported from Trac #388, reported by jcpetruzza on 2008-11-01)
Let's say you are working on a new version of a library; you add a new internal (i.e. non-exposed) module but you forget to update the package description. You locally test your changes, everything works fine so you install it. Now, since the new module is not listed in other-modules it will not be included in the final library. Therefore, when you try to use it you get rather cryptic linker errors. It can take a while until you realize where the problem is coming from.
The proposal is to look, during build, for compiled modules under the dist directory that are not included in the final library and warn the user about their presence.
(Imported comment by @dcoutts on 2008-11-01)
For anyone who wants to try implementing it, watch out for old stale .hi files in the dist directory. Perhaps comparing timestamps or something will be enough.
Duplicate of #1746.