editorial: Get/Set 'lastIndex' on RegExp object cannot trigger user-code

[aapoalas]

Purely an editorial change, this implies no change in the implementation: The Get and Set calls on "lastIndex" property of a builtin RegExp object cannot trigger user-code, as the property is installed as an unconfigurable own data property of the object with a set value: the property cannot be turned into an accessor property, and the value cannot be unset to make the Get/Set operations enter the prototype chain.

The Get call on "lastIndex" is thus fully infallible: it will always find a valid property value and can never throw any errors.
The Set call on "lastIndex" can still throw errors, as the property can be made unwritable in which case trying to change its value will throw an error.

This appears most importantly in the RegExpBuiltinExec function but also in RegExpInitialize.

[michaelficarra]

Your reasoning seems correct to me.