return when desugaring to closures

[Eric Suen]

>> The parser is required to backtrack until it either finds an
>> expansion of the grammar that doesn't generate a syntax error or
>> until it discovers that they all do.  You can choose to make
>> additional syntax errors as per chapter 16, but that does not
>> relieve you of the backtracking requirement.
>
> You're right that a bottom up parser will have a reduce-reduce
> conflict. For a top-down parser, it's not an issue.
>

Are you sure about that, because you using hand written top-down parser,
Is it confirmed by a top-down parser generator like ANTLR?

I think top-down parser has no issue to parse following code:

function() {
}();

but this is not a valid statement because:

ExpressionStatement ::= [lookahead ! {{, function}] Expression ;

This kind question I asked long time ago, but no one answed,

https://mail.mozilla.org/pipermail/es-discuss/2008-July/006640.html

and now seems write a bottom up JS parser is mission impossible.

Regards,

Eric Suen