Normative: Generically forbid 402 method extensions in Forbidden Extensions

[rkirsling]

Forbidden Extensions has a list of methods which are specified in ECMA-402 instead, but a few are missing; this PR rectifies that.

[ljharb]

Given that these are actually forbidden, this seems like a normative change to me, not an editorial one (altho not one I suspect needs consensus).

[rkirsling]

My understanding is that the normative part is in each of the respective sections (e.g. BigInt.prototype.toLocaleString), while this bullet point is just being helpful by collecting the full list in one spot.

[ljharb]

Touché

[bakkot]

Hm, I'd lean towards considering this normative. BigInt.prototype.toLocaleString says

An ECMAScript implementation that includes the ECMA-402 Internationalization API must implement the BigInt.prototype.toLocaleString method as specified in the ECMA-402 specification. If an ECMAScript implementation does not include the ECMA-402 API the following specification of the toLocaleString method is used.

which reads to me as a less strict requirement than the "The behaviour of the following methods must not be extended except as specified in ECMA-402:" requirement which appears in Forbidden Extensions.

[michaelficarra]

If we ask for consensus for this, the consensus we get should be for fast-tracking all 402 methods into 262 forbidden extensions, without requiring further approval from the committee.

[rkirsling]

Here's an attempt at a generic phrasing.