toString OutputWriter method not calling derived class

[cc]

When defining a toString(W)(ref W writer) function on a base 
class and derived class, only the version on the base class is 
called when formatting into a string.  Is this intended behavior?

import std.format;
import std.range.primitives;
class Foo {
	string test() {
		return "Foo?";
	}
	void toString(W)(ref W writer) if (isOutputRange!(W, char)) {
		put(writer, "<FOO>");
	}
}
class Bar : Foo {
	override string test() {
		return "Bar?";
	}
	void toString(W)(ref W writer) if (isOutputRange!(W, char)) {
		put(writer, "<BAR>");
	}
}
Foo[] list = [new Foo(), new Bar()];
foreach(i, item; list) {
	writefln("%d: %s (%s)", i, item, item.test());
}


Result:
0: <FOO> (Foo?)
1: <FOO> (Bar?)