RE: Standard Library Haddock-Interfaces?

Consider this:

module M (Monoid(..)) where { import Control.Monad.Monoid; }

I'd like Haddock to show documentation for Monoid in module M (for instance).

Unfortunately this isn't possible. Haddock can produce documentation with hyperlinks to entities in another package, but it cannot include full documentation for entities which are re-expored from a different package. This would require essentially keeping a copy of the entire documentation for the package in the interface file.

Are there standard Haddock-interfaces for the standard libraries?

A GHC distribution comes with Haddock interfaces for all the packages that it ships with. Cheers, Simon