libghc6-src-exts-dev 1.3.0-1 (amd64 binary) in ubuntu lucid

 haskell-src-exts (HSX, haskell-source with extensions) 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
  * GADTs
  * Implicit parameters (ghc and hugs style)
  * Template Haskell