[nxtrafalgar]

>I work on a C codebase that does this

And more power to you. Note the beginning of the parent comment, however:

> Just because you 'can' write such an array implementation doesn't mean you will

So yes, even if the codebase you work on does have these 'mythical', hard-to-achieve properties, that doesn't mean that most or even many C codebases will.

Good engineering entails observing what problems actually occur and working to fix those. Memory safety issues do commonly occur in C codebases. Regardless of whether the fix in C is simple or even trivial, programmers aren't doing it. So, Rust has some value because it forces the programmer to produce code that is largely free from this type of issue.

Enforcing norms like 'be more disciplined when writing C' or 'stop using external libraries' is much harder than simply using a different language.