We can, yes, but we also can forget to code any such condition as well, which is all too common. And for e.g. C the lack of an explicitly supplied by the progra

We can, yes, but we also can forget to code any such condition as well, which is all too common. And for e.g. C the lack of an explicitly supplied by the programmer runtime-check is exactly equivalent to the programmer explicitly stating and pledging that such runtime-check is entirely unnecessary, and even it's trivial to statically check at compile time that this pledge is in fact false, no diagnostics is required.