cannot throw error in generator

cannot throw error in generator.debug.txt

works if generator is not calling another function ?

example from http://davidwalsh.name/es6-generators-dive
similar example at https://gist.github.com/deepak/9a7337d7a641f8af9c8b

does_not_work.js

function *foo() {
    try {
        var x = yield getThree();
        console.log( "x: " + x ); // may never get here!
    }
    catch (err) {
        console.log(err.toString());
    }
}

function getThree() {
  it.next(3); 
}

var it = foo();
var res = it.next();
console.log(res);

it.throw("Oops!");

// output
// Error: Generator is already running
// {"done":true}

works.js

var it = foo();

function* foo() {
    try {
        var x = yield 3;
        console.log( "x: " + x ); // may never get here!
    }
    catch (err) {
        console.log( "Error: " + err );
    }
}

var res = it.next();
console.log(res);

it.throw("Oops!");

// output
// {"value":3,"done":false}
// Error: Oops!

similar to https://gist.github.com/deepak/9a7337d7a641f8af9c8b