Backwards compatibility with what? Rust has always has had enum also for this exact case, to avoid encoding sentinels as strings or pointers.

you literally sound insane. its like an assembly fanboy saying C isn't any better because you could write inline asm, and therefore whatever bugs C prevents, well, it doesn't prevent them at all.

people like you are holding back software and security by decades.

im quite positive the only rust programmer who would do this is a C programmer who doesn't understand rust