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]);
}