Tested in dmd 1.006 on Linux, the two toString definitions conflicts when they are in main, not when they are out of the main function.

import std.stdio;
int main(char[][] args)
{
	enum Foo { A , B };
	enum Foo2 { C , D };

	char[] toString(Foo x)
	{
		return "1";
	}
	char[] toString(Foo2 x)
	{
		return "2";
	}

    Foo s = Foo.A;
    writefln("s is %s, with name %s\n", s, toString(s));

    Foo2 o = Foo2.C;
    writefln("o is %s, with name %s\n", o, toString(o));
    return 0;
}