A ton of features on this list really require an IDE or rich program representation, or _something_ that's not just plain text. For instance using content hashes to refer to functions is only reasonable with IDE tooling support.
But programming language itself is a tool. And, you need one tool to improve the other, that imply your tool (programming language) is not good enough.
IMO, the only reason why java is still in use - superb IDE and tooling, that compensate terrible language design.