[Webkit-unassigned] [Bug 163208] [ES6]. Implement Annex B.3.3 function hoisting rules for eval

bugzilla-daemon at webkit.org bugzilla-daemon at webkit.org
Thu Apr 6 10:17:06 PDT 2017


https://bugs.webkit.org/show_bug.cgi?id=163208

--- Comment #66 from Caitlin Potter (:caitp) <caitp at igalia.com> ---
(In reply to GSkachkov from comment #65)
> (In reply to Caitlin Potter (:caitp) from comment #63)
> > (In reply to Saam Barati from comment #46)
> > > If you run this program in Chrome Canary, you can see V8's behavior here
> > > w.r.t the specification. It looks like the eval does indeed perform `has` on
> > > the thing inside the with scope.
> > > 
> > > ```
> > > function foo() {
> > >     let p2 = new Proxy({}, {
> > >         has(t, p) {
> > >             console.log(p)
> > >             return Reflect.has(t, p);
> > >         }
> > >     });
> > >     with (p2) {
> > >         eval("Reflect.has(p2, 'bar'); { function baz() { };  }");
> > >     }
> > > }
> > > foo();
> > > ```
> > > 
> > > I'm not sure if V8 is correct here, but we should verify the correct
> > > behavior and try to get that landed. V8 will have the following output:
> > > 
> > > ```
> > > eval
> > > Reflect
> > > p2
> > > bar
> > > baz
> > > ```
> > 
> > I believe this is correct, per
> > https://tc39.github.io/ecma262/#sec-object-environment-records-hasbinding-n
> > and
> > https://tc39.github.io/ecma262/#sec-object-environment-records-
> > getbindingvalue-n-s
> 
> Hmm, I stil think that it should not be printed 'baz', because according to
> the p.B.3.3.3.1.d.ii.4.b('If thisEnvRec is not an object Environment Record,
> then') we don't invoke hasBinding, and just go to outer env recode
> https://tc39.github.io/ecma262/#sec-web-compat-evaldeclarationinstantiation

As I said on IRC, I wasn't commenting on the hoisting of baz, because the behaviour of block scoping of functions and annex B changes to that are somewhat hard to follow.

It looks like you're right about that HasProperty() not occurring from step 5, but it may occur further down in the algorithm, from `Let fobj be ! benvRec.GetBindingValue(F, false).`, as I believe in this instance, benv still refers to the with block.

I could be wrong about this, Adam Klein is much more knowledgable about the block-scoping of functions than I am.

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