Clojure uses its metadata (attached to values, though, not declaration) to put documentation strings there.
That's quite doable with D:
@(doc("This function does.... "))
auto foo()
{ ... }
I'm also interested in tagging data:
@(Sorted!(withThisFun)) someRange ...
@(Ranged(0.0, 1.0)) someRange ...
or:
@Validated SQLQuery query;
