Why isn't this seen as problem by default?
The error is a run time error, not a compile time error. The code is perfectly valid, it just does something stupid. The very simple case that you show could certainly be detected, but many cases that would be only slightly more complicated would be difficult to detect:
void evil() {
if (somethingThatTurnsOutToAlwaysBeTrue)
evil();
}
In order to determine whether that's a problem, the compiler has to try to figure out whether the condition will always be true or not. In the general case, I don't think this is any more computable than determining whether the program will eventually stop (i.e. it's provably not computable).
