https://github.com/Bolpat/DIPs/blob/a872d3b5602a45d1767d5acb962ba24becaa26ce/DIPs/DIP-2NNN-QFS.md
Abstract
The goal of this proposal is that every type construction expressible by D’s type system also has a representation as a sequence of D tokens. The type constructs that lack this are function pointer and delegate types that return by reference and/or have a non-trivial linkage.