ES6 feature: Meta property

[ariya]

Syntax:

NewTarget : new . target

Spec:

https://people.mozilla.org/~jorendorff/es6-draft.html#sec-meta-properties

Relevant AST interfaces (from https://github.com/estree/estree):

interface MetaProperty <: Expression {
    type: "MetaProperty";
    meta: Identifier;
    property: Identifier;
}

[ariya]

There is a problem. The lengthy discussion estree/estree#32 reached the consensus to go with the generic MetaProperty node. In the mean time, according to https://bugzilla.mozilla.org/show_bug.cgi?id=1141865, Mozilla SpiderMonkey is going with NewTargetExpression. See the code at https://hg.mozilla.org/mozilla-central/file/tip/js/src/jsast.tbl.

@jorendorff Is this decision final? Shall I file a Bugzilla issue? Please advise.

[jorendorff]

No, the decision was out of pure expedience. We don't want to keep it. It's a matter of someone finding time to fix it. See https://bugzilla.mozilla.org/show_bug.cgi?id=1168992 .

[jorendorff]

Eric Faust reminded me that one reason we've held off fixing it is that our internal parse tree doesn't contain location information for each individual part of the new.target. Some of that has been fixed as we implemented super().

[ariya]

@jorendorff Thank you for the prompt response and excellent explanation! In mean time, we will go ahead and implement it as MetaProperty.