REGRESSION: class extends native builtin (ArrayBuffer/Map/Promise/TypedArray/…) broke — 23 subclass-builtins cases (#5613) #5657

Severity: HIGH (class extends native builtin)

The 2026-06-25 full re-sweep (main @ 9a3d2469d, perry 0.5.1206, node v26.3.0) raised overall parity to 94.1%, but 23 class extends <native builtin> cases newly broke vs the prior sweep — every subclass-builtins test under both language/statements/class and language/expressions/class:

subclass-ArrayBuffer.js       TypeError: ArrayBuffer is not a function
subclass-DataView.js          TypeError: DataView is not a function
subclass-Function.js          TypeError: Function is not a function
subclass-Promise.js           TypeError: Promise is not a function
subclass-RegExp.js            TypeError: RegExp is not a function
subclass-Map.js               TypeError: Constructor Map requires 'new'
subclass-Set.js               TypeError: Constructor Set requires 'new'
subclass-WeakMap.js           TypeError: Constructor WeakMap requires 'new'
subclass-WeakSet.js           TypeError: Constructor WeakSet requires 'new'
subclass-BigInt64Array.js     TypeError: Constructor %TypedArray% requires 'new'
subclass-BigUint64Array.js    TypeError: Constructor %TypedArray% requires 'new'

(× both statements/class and expressions/class) plus built-ins/ArrayBuffer/isView/arg-is-dataview-subclass-instance.js.

Root

Window points squarely at #5613 (6de00e8f5) — "class extending a function base must run the parent constructor (preserve derived identity)". That path now treats a native builtin base (ArrayBuffer, Map, Promise, %TypedArray%, …) as a plain callable function base and tries to invoke it as the parent constructor, but native builtins reject being called without new / aren't resolved as a callable in that path → X is not a function / Constructor requires 'new'. extends of a native builtin must route to the builtin's construct path, not the run-parent-as-function path.

This inflates the #5592 class-tail count (240 → 257); the true class tail is lower.

Smaller co-regressions from the same batch (3)

• annexB/language/eval-code/direct/func-switch-case-eval-func-no-skip-param.js + func-switch-dflt-… — binding is not initialized (likely fix: #5594 — Annex B.3.3.3 global eval function-declaration binding #5636 B.3.3 over-reach on switch-param eval).
• built-ins/RegExp/unicode_restricted_quantifiable_assertion.js — RegExp("(?=.)*","u") must throw SyntaxError under /u (regression from fix(regex): accept JS quantified lookaround like (?=x)? (V8 no-op semantics) #5629 quantified-lookaround acceptance).

Measure

scripts/test262_subset.py --root /root/test262 --dir language/statements/class language/expressions/class built-ins/ArrayBuffer --jobs 6

on the internal Linux sweep host.