v0.68.0

v0.68.0

Lockstep release of @loopdive/js2 and the js2wasm proxy: 0.67.0 → 0.68.0.

A conformance release, focused on the standalone (pure-Wasm, no JS host) lane's
own-property and descriptor model. All numbers below are measured against the
standalone test262 lane with denominators, and every fix carries a kill-switch
receipt — a fix is credited only when the same corpus is measured with the
change removed.

Conformance

Two independent lanes, never summed — they measure different targets:

Lane	v0.67.0	v0.68.0	Change
JS-host (gc target, host imports allowed)	29,856 / 43,099 (69.3 %)	30,982 / 43,505 (71.2 %)	+1,126 passes, +1.9 pp
Standalone (--no-host-imports, pure Wasm)	not published	27,339 / 43,505 (62.8 %)	—

Two caveats on those numbers, because they change what the delta means:

• The corpus grew between releases (43,099 → 43,505 tests, +406). The
  +1,126 host passes are therefore against a larger denominator, not a fixed
  one — the percentage-point change is the sounder of the two figures.
• No standalone delta is given because there is nothing honest to compare
  against. The committed standalone summary
  (benchmarks/results/test262-standalone-current.json) did not exist at
  v0.67.0, so a change figure would have to be sourced from a different
  artifact measured under different conditions. From v0.69.0 onward both lanes
  will have a like-for-like predecessor.

Most of this release's work targets the standalone lane; the host lane
moves largely as a side effect.

Features

• typeof on reified builtin constructors (#4120). A builtin captured into
  a value (const C = Array) reported "object", because the standalone
  carrier is a plain $Object singleton while the typeof natives classify by
  closure-wrapper shape. Now carried on two internal-slot bits, so callable and
  constructible are distinguished (isNaN is callable but not constructible)
  and Math/JSON/Reflect correctly stay "object".
  +16 files, 0 regressions across a 66-file control set.
• Object.prototype.toString in standalone (#4119 arm 1). A runtime
  §20.1.3.6 classifier replaces a blanket refusal. The 76 target rows go
  0/76 → 75/76; the refusal bucket goes 76 → 0, with 0 regressions across an
  82-row sweep. Receivers the classifier cannot yet tag correctly — $Proxy
  (which subtypes $Object, so a revoked proxy must still throw), primitive
  wrapper objects, and a few exotics — keep the loud refusal rather than
  falling through to a default [object Object].
• Own-property visibility over the unified store (#4010 S3). hasOwnProperty,
  in, getOwnPropertyDescriptor and Object.keys now see properties held in
  the carrier bag. +4 files, 0 regressions, validated against the complete
  729-file at-risk stratum (built-ins/**/{name,length}.js), not a sample.
• Deletability on class instances (#4098 stage 1). delete o[k] is now real
  on a user-declared class instance, via a per-instance tombstone store. This is
  substrate: it flips no test262 files on its own (the property-descriptor
  verifier is all-or-nothing and needs the remaining stages), and shipping it
  alone is deliberate — the alternative partial reproduces a known 684-file
  regression.

Fixes

• Object.create silently dropped every accessor descriptor (#4061). Its
  static expansion set the accessor flag but never compiled the getter, so
  Object.create({}, {p: {get: () => 9}}).p evaluated to 0 — a wrong answer
  with no error, on the legal path. Accessor-bearing descriptors now route to
  the dynamic applier.
• Descriptor-argument validation per §8.10.5 (#4061). Object.create and
  Object.defineProperties now reject non-object descriptors, non-callable
  get/set, and data+accessor conflicts. 16/17 target files, 0 regressions
  across a 182-file sweep.
• Non-writable builtin properties were silently writable into the closure
  bag (#4010). A write to a builtin's non-writable name/length was
  deposited invisibly, which made configurable: true assertions fail across
  roughly 700 files whenever own-property queries widened. Fixed at the source
  (§10.1.9 OrdinarySet is a no-op over a non-writable own data property)
  rather than at the query.

Other

• Pre-commit fast lane. The full pre-commit chain exceeded tooling timeouts,
  which drove wholesale --no-verify and disarmed the cheap format/lint gate
  along with it. SKIP_SLOW_PRECOMMIT=1 now skips only the slow checks; the
  formatter always runs. CI is unchanged.
• Issues filed with reduced repros and measurement-backed acceptance criteria:
  #4143, #4146, #4147, #4148, #4151.

Known gaps

• Object.prototype.toString on Date/Error/RegExp/class instances,
  $Proxy, and Symbol/BigInt wrappers still refuses loudly (#4119 arm 2 and
  successors). A refusal is deliberate here: a wrong tag would be worse.
• Array.prototype methods other than slice/toString still refuse when used
  as values (#4119, #3571).
• Class instance fields remain invisible to getOwnPropertyDescriptor and
  Object.keys (#4098 stages 2–4); only deletability landed in this release.