Inside outer(), a yield* delegates to inner(), and inner() ends with a return statement. What is the value bound to `r`?
function* inner() {
yield 'a';
return 'RET';
}
function* outer() {
const r = yield* inner();
yield r;
}
const it = outer();
it.next(); // { value: 'a', done: false }
it.next(); // { value: ?, done: false }