OP says you can't really avoid it in Rust either, but argues that because there's not a separate check it's more robust. I agree w/ you though that it's not a strong argument, and that you can do the same thing in C++; it's a confusing/arguably incorrect point IMO.

More broadly, this is kind of a bad example. Handling files is surprisingly difficult and that's really where the dragons lie here. IME the dragons exist for both Rust and C++, because they're platform problems rather than stdlib/language problems.

NB: the correct thing to do here for POSIX platforms is to call fstat, which is true regardless of systems language.