On Feb 3, 2012, at 4:26 PM, Jason Orendorff wrote:
> On 2/3/12 6:13 PM, Allen Wirfs-Brock wrote:
>> But I also have to validly (and hopefully reasonably) specify exactly what
>> happens for the unrealistic use cases. There is a problem with your
>> desugaring in that the evaluation of INIT isn't scoped correctly relative to
>> V.
> Hmmm. I don't see the problem yet. I think it's scoped the way I intended it:
> INIT is evaluated in the enclosing environment; V isn't in scope.
Under the scoping rules TC39 has agreed to, the initializer of a let/const is
always shadowed by the binding it is initializing:
{
let i="outer";
{
let i=i; // throws reference error because I is initialized
}
}
Hence, for consistency, this also should throw in the same way
{
let i="outer";
for (let i=i;;){}
}
You can tweak your desugaring to get this effect by changing the first part of
it it:
{
let V = INIT;
let %tmp = V, %first = true;
while (true) {
>
> Anyway—all this should be easier to express in spec language than via
> desugaring, because in spec language you can give an environment a name. This
> makes it easier to just say what you mean. Whereas if you're using
> desugaring, scopes are *places*, so you have to very carefully say half of
> what you mean while standing in the right place to express the rest.
agreed
>
> -j
>
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