What's the purpose of an asterisk (*) in ES6 generator functions

Question

Can someone explain to me: why are generator functions in ES6 marked by asterisk symbol?

For example, instead of:

Answer 1

Empty generators (with no body) are not disallowed; so should unStarredFunc() follow generator semantics or not?

For compatibility reasons:

function yield(x) { return x };

function a() { 
    yield (4+1);
};

this is syntactically correct but calling .next() would result in an error whereas adding an asterisk to explicitly define a generator would cause .next().value === 5

detect that someGenerator contains yield operator at parse time

Some constructs cannot be resolved at parse time:

function someGenerator(i) { 
    if (glob) 
        return 4; 
    else 
        yield* anotherGen(i);
}

And of course its simpler to see immediately from the function* definition that its a generator without needing to dig into its source to look for yields.