Editorial: Add BigInt to the list of reference base value types and the language types intro text

[bathos]

Similar to #1769 — BigInt was absent from the list of types that the base value component of a Reference could be.

Note that it is already included and handled as a possible base value in the HasPrimitiveBase abstract op.

I was unsure if there was any particular logic to the ordering of types, so I just slotted it in the ‘most alphabetic’ seeming part of the list. Alternatively, the sentence could be reworded to avoid listing them all if it’s felt that this is becoming an update hazard, e.g.

The base value component is either an Environment Record or a language type other than Null.

Or, if it’s desired to draw additional attention to undefined’s distinct significance here:

The base value component is either an Environment Record or a language type other than Null (but including undefined).

(ref #1515)

[claudepache]

Alternatively, this could be reworded to avoid listing them all, e.g.

The base value component is either an Environment Record or a language type other than Null.

undefined plays a special role which could have better been modelled as empty. IMO, a better rewording would be:

The base value component is either undefined, or an ECMAScript language type other than Undefined and Null, or an Environment Record.

EDIT: I meant, of course:

The base value component is either undefined, or an ECMAScript language value other than undefined and null, or an Environment Record.

[claudepache]

BTW, another place where BigInt is still missing, is in the list of types found in the introductory paragraph of Section 6.1 ECMAScript language type.

[bathos]

Thanks @claudepache, I’ve added the missing one you mentioned. For now I’ve left the full enumeration in the base value list to err on the side of minimal change, but will update it if it turns out there’s general agreement that a briefer version would be better.

[ljharb]

Let's keep this fix focused, and leave larger refactors to a followup PR.

[bakkot]

It is also missing from the first step of CreateListFromArrayLike. I've checked the rest of the spec and found no other omissions.

[caiolima]

Thank you very much for this PR!