Represent array holes independently from element storage with an optional runtime presence bitmap. Preserve hole state through length changes, deletion, slicing, concatenation, sorting, copying methods, iteration, serialization, and reference-counted cleanup while retaining packed-array fast paths.
Extend frontend lowering and IR validation for sparse literals, Array length construction, property-presence checks, delete, length assignment, and sparse appends. Add dense-array analysis so proven packed reads can use dedicated unchecked-presence runtime entry points in both native backends.
Add differential corpus coverage, runtime lifecycle tests, IR analysis tests, and compile fences for JavaScript fill loops that cannot prove complete initialization. Update affected binary-size expectations and align structuredClone transfer diagnostics with Node wording.
- The written-binding decline yields when the declared type has no mapping or the write's RHS roots at an ambient-undefined name
- A class extending a collection-poisoned base flushes the base's diagnostics eagerly: the heritage evaluates at module init, so deferring the compiler's own fence manufactured a silent wrong output
- trapDeclRootOf's written-binding decline now requires a mappable declared type: ordinary storage only buys anything when it compiles — an unmappable recursive call shape traded the compiling no-storage trap for a guaranteed SC2009 on a value that never exists
- bindingEverWritten skips statement-position writes whose RHS chain roots at an ambient-undefined name: that statement IS the RHS root's throw (lowerExprStatement's first claim) and never touches the target's storage, so it cannot justify the decline
- A poisoned base a top-level class extends flushes its deferred diagnostics eagerly (collectClassShape): the heritage evaluates at module init and the base's fence is the compiler's own — Node defines the base fine — so the deferred trap compiled a binary that refused at startup where Node runs; leaf and derived-only poisoned classes keep the JS deferral
- Fixtures: corpus 2632 (unmappable written trap binding) and 2633 (ambient-rooted rewrite), diagnostics js-extends-poisoned-base (the eager report names the base's real blocker), errors.test pins for both deferral edges that must NOT report eagerly; order-parity baselines recorded for the new entries
- The ratified rename rider (world-unification §7 lane 5): "DOM" collided with the browser DOM and, post-lane-1, the structure is no longer a document tree. Comments and doc prose now say "the checked-dynamic tree" for the noun and "dyn" adjectivally; runtime symbol names (scr_dyn_*), the error.domClone libCall, and the real web DOMException family are unchanged.
- The few user-facing strings carrying the nickname move with it (the structuredClone cyclic message, the dc subscriber/publish fences, two emitter ICE texts); diagnostics snapshots regenerated (96 pass). One private compiler constant (DOM_PROTO_METHOD_NAMES -> DYN_PROTO_METHOD_NAMES) rides along.
- Mechanical sweep, 142 files, comments/prose only — no behavior change.
- corpus 2578 (TS) and 2579 (JS, the JSDoc @param {object} repro shape) pin typeof/truthiness/String()/===, scalar normalization, representation-free narrowing, and the identity round trip against Node on both backends
- npm case jsval-into-dyn drives the prettier-plugins shape over a real package surface (the new plugstub fixture package: any-declared exports carrying engine functions)
- dyncheck jsval-* tests pin every loud fence (keyed read/write, member calls, 'in', destructuring, JSON.stringify, structuredClone, Object.keys, deepStrictEqual, inspect) plus the RC-clean catch-and-continue unwind under the SAN lane
- the errors.test.ts SC1101 pin flips to the now Node-exact behavior (the retired "one unbridgeable mix": the wrapped argument compiles and the unbound-this read throws Node's own TypeError); ts7 order-parity baselines record the three new fixtures
- Array patterns over checker-typed string sources split once through %str.chars (code points, astral characters whole) and ride the array machinery — declarations, assignments, for-of heads in both declaration and expression position, and parameters; object patterns bind the wrapper's one own data property, length, with renames and dead defaults. Static builds claim exactly what staticStringPattern vets; every other string form keeps the engine gate, and --dynamic keeps the engine route wholesale.
- Object patterns over stdlib globals in JavaScript files bind MEMBER identity tokens (const { subtle } = globalThis.crypto, const { Console } = console — 27 of the node suite's 28 SC1031 first-blockers), so programs run past the destructure and each use meets its own per-site fence; globalThis members are provenance-vetted, bind the member global's own token, and register the stdlibGlobalAliasDecl twin, so surfaced members (Math) keep their receiver-keyed lowerings.
- Members of SURFACED globals (Math.max, process.env, console.log) fence eagerly by member and global name instead of degrading detached uses to quiet token reads, and IR-string sources the checker does not type as strings fence naming the checker's type, never the token's carrier.
- Corpus 2556-2558 pin the string forms and the token identity/truthiness/alias agreements under the Node oracle, byte-identical through both backends; errors.test.ts pins the surfaced-global fence and the lazy per-site token failure.
- order-parity baselines re-recorded additively: the new entries plus the 2510-2555 fixtures that landed without one.
- island ('any') arguments at intrinsic/libCall/callValue slots take the validated exit (dynCheck's stance); non-exit-safe slots fence with the slot named, and the boundary pass backstops every jsOp/dynCall/dynInvoke argument so world-mixing sites can never ICE
- a checker-'any' receiver/callee that LOWERED checked-dynamic dispatches to the DOM machinery: ambient-this reads are dynKeyGet, rest-args map/forEach ride the runtime dispatch, dyn callees take dynCall
- Object.entries/values push unit-armed (null | undefined) fields as the null literal; new Set(seed) exits an island-handle seed as a validated copy
- fence-bodied functions emit even when their ABI names an unregistered class, and a run()-end sweep rewrites leftover unregistered-class type slots to the inert f64 placeholder — the clang invalid-C escape closes with the ICE
- RegExp[] compiles (REF elements, both backends; map callbacks returning other unrepresentable kinds meet a named fence), and the C emitter appends program-sized line arrays by loop, not spread (500k-line TUs overflowed the stack)
Jimmy Miller