The doc states that bringToFront() returns the number of elements brought to the front, but it actually returns the number of swaps done:
--------------------
import std.algorithm, std.stdio;
void main()
{
    auto r = [4, 5, 6, 7, 0, 1, 2, 3];
    foreach (k; 0 .. r.length)
        writeln(bringToFront(r, r[k .. $]));
}
--------------------
% dmd -run test.d
0
7
6
7
4
7
6
7
--------------------

The output should be "0 7 6 5 4 3 2 1".