On Nov 10, 2011, at 11:07 PM, Dmitry Soshnikov wrote:
> Brendan and Dave mention explicit semicolon. Yes, it's seems so by the
> grammar (though, have to check more precisely), but it can be acceptable
> price.
No, it is a runtime incompatibility that shifts meaning, without errors.
switch (x) { case 1: (function (){return 42}); break; default: (function
(){return 99}); }
(a[i].b()).c(d)
The switch is now the callee expression in a call taking one actual parameter,
a[i].b().
The same can happen with leading [, unary +/-, and / as regexp delimiter -- any
lexeme that can both start a statement and continue an expression.
> P.S:
>
> Regarding Dave's `do { .. }` -- we may omit `do` and just evaluate the block.
>
> let a = {
> print('doing stuff');
> 100;
> };
>
> It's of course seems ambiguous with an object initialiser (at first glance),
> but it's only at first glance. Obviously there is a code inside to evaluate.
I worked on this, based on ideas from Breton Slivka and Doug Crockford. Please
see
http://wiki.ecmascript.org/doku.php?id=strawman:arrow_function_syntax
and
https://mail.mozilla.org/pipermail/es-discuss/2011-June/015568.html
This is not going to fly in a grammar that we validate using LR(1) parsing.
Block-lambdas require {|| at least to defer evaluation until invocation,
whereas any block-expression would be immediately evaluated. This could be a
point of confusion.
Altogether, this says Dave's 'do' proposal is better because EIBTI.
/be
>
> Cheers,
> Dmitry.
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