Implicit static->dynamic arr and modifying

[Nick Sabalausky via Digitalmars-d-learn]

Is this kinds stuff a sane thing to do, or does it just work by accident?:

void modify(ubyte[] dynamicArr)
{
    dynamicArr[$-1] = 5;
}

void main()
{
    ubyte[4] staticArr = [1,1,1,1];
    modify(staticArr);
    assert(staticArr == [1,1,1,5]);
}