Haddock/Development ideas

There would be a number of benefits if GHC's parser were extended to understand the Haddock documentation markup and then Haddock changed to use the GHC API:

• Haddock would get full support for GHC's various syntactic extensions.
• Haddock would understand {#- LINE -#} pragmas which would allow it to generate links to the original source code.
• Haddock would get much better error messages.
• Haddock could infer types for functions with no explicit type signature.
• GHCi and IDEs like hIDE and Visual Haskell would be able to display API documentation in more convenient ways like in this Haste screenshot:

• Haddock could accept module parameters with space after "-- #" ("-- #hide" is accepted nowadays, but "-- # hide" not)
• It would be good to have a recursive flag that would operate on all the .hs and .lhs files under a single directory.

• It would be nice if haddock is able to parse more user defined operators like (#).

• Haddock should emit the documentation about instances. For example, it's important to document that the Data.Map instance of Foldable only folds over the values and not the keys.