std.sumtype?

[drug]

I think that `kind` vs `handler` is more like old-school vs modern 
style. They are equal in general. Modern compilers are good in 
optimization. I chose TaggedAlgebraic for my projects about 7 years ago 
and don't remember the exact reason I was need for kind feature. In 
general I agree to Steven. I can add to his post that kind lets you do:
```D
	switch(kind)
	{
	case Kind.foo0..case Kind.foo5:
		doSomething1;
		break;
	case Kind.bar:
	case Kind.baz:
	case Kind.foobar:
		doSomething2;
		break;
	default:
		doDefaultThings;
	}
```
using handlers:
```D
	someType.match!(
		(Foo0 foo) => doSomething1,
		(Foo1 foo) => doSomething1,
		(Foo2 foo) => doSomething1,
		(Foo3 foo) => doSomething1,
		(Foo4 foo) => doSomething1,
		(Bar  bar) => doSomething2,
		(Baz  baz) => doSomething2,
		(FooBar fb) => doSomething2,
		(_) => doDefaultThings;
	);
```
These examples are verbose equally but the first version contains less 
boilerplate.

I believe both approaches are good. They complement each other.