The haskell-src-exts package
Haskell-Source with Extensions (HSE, haskell-src-exts) is an extension of the standard haskell-src package, and handles most common syntactic extensions to Haskell, including:
Multi-parameter type classes with functional dependencies
Indexed type families (including associated types)
Empty data declarations
and a few more. Apart from these standard extensions, it also handles regular patterns as per the HaRP extension as well as HSX-style embedded XML syntax.
For details on usage, please see the website.
For package maintainers and hackage trustees