Comment by hgoel

I think it's about if there's a possibility of it being zero. Of course there's no way to tell at compile time that a value will definitely be zero.

So, in pseudocode

int div(int a, int b): return a / b;

Would probably be a compile time error, but

int div(int a, int b): return b == 0 ? ERR : (a /b);

Would not, or at least that's what I'd expect.