for-loops and declaration-like init expressions

[Allen Wirfs-Brock]

Over and beyond the breaking change WRT function, I really don’t see the value in such a restriction.  There are many pointless or nonsensial things that can be written as expressions.  In general, we  don’t complicate the language to make such things illegal. 

Allen


On Jun 5, 2014, at 7:58 AM, Andreas Rossberg <rossberg at google.com> wrote:

> C-style for-loops allow declarations as init statements, but only some
> of them. Yet, the others (function and class) are actually
> syntactically legal in that position as well, because they are simply
> parsed as expressions. Consider:
> 
>  let x = 0
>  for (let x = 1; ;) x  // 1
>  for (const x = 1; ;) x  // 1
>  for (function x(){}; ;) x  // 0
>  for (class x(){}; ;) x  // 0
> 
> I think these latter two examples violate the principle of least
> surprise. I wonder if it wouldn't be cleaner to rule them out, by
> imposing the same lookahead restrictions on for-loop init expressions
> as there are for expression statements.
> 
> The one caveat is that for function, that would actually be a breaking
> change, but is it likely to be a real world one?
> 
> What do you think?
> 
> /Andreas
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