New SignatureSections extension

Originally proposed by Lennart Augustsson

See also SignatureSections

Preliminary specification

Have

• (:: type )

be syntax sugar for

• (\x -> x :: type )

This new syntax extension is enabled via a new SignatureSections (or maybe TypeSignatureSections) language pragma, e.g.

{-# LANGUAGE SignatureSections #-}

Typing judgement:

_________________________
 G ⊢ (:: ty) :: ty -> ty