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?)

On 25/05/2018 9:21 PM, cc wrote:
> 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?)
> 

Yes, because templates are not virtual.