What does indexing into an object with the proposed slice notation do

[benderTheCrime]

Example:

// Create an "arguments"-like object here, but any Object will do.
const obj = {
    1: 'foo',
    2: 'bar',
};

const bar = obj[:2];

Should this be considered a syntax error?

[ljharb]

It doesn't have a length, so its length would ToLength to 0, so bar should be [] - just like Array.prototype.slice.call(obj, 0, 2) would produce.