> Meeting these constraints typically involves creative use of parser generators like Bison or requires the developer to create a parser from scratch - Which unfortunately many modern languages like Rust itself have had to end up doing

This seems like a very useful project for people writing IDEs, but I'm not sure the convenience features are enough to offset the simplicity and flexibility of writing your on parser.

I'll praise the day something similar becomes a part of the Rust language itself.

Or of Zig, or whatever systems language. Come to think of it, Zig could be the better language to take advantage of this.