The test from #1548 casts JSON.parse to Partial<Envelope> into a
block-local const, which continues as its parsed value since #1561, as
in Node. The path messages are now pinned with the cast passed to a
typed parameter, which is checked at the cast, and the block-local form
is pinned against Node.
`JSON.parse(text) as T`, `const x: T = anyValue` and `await res.json()
as T` threw `TypeError: expected X at $.path, got Y` when the value did
not fit `T`. Node never checks an assertion and continues with the value
it has, so the build-container listener rejected an order Node accepts
and a JWT with a string `exp` became a 500.
A failed cast now keeps its value when it initializes a `const`/`let`
binding declared in a function or block and only the code after the cast
reads the binding. That code (the statements after the cast in each
enclosing statement list, up to the declaration) lowers twice: the
static copy, unchanged, runs while the value fits; a dynamic copy, in
which the binding and everything derived from it is typed `any`, runs
after a failure, so missing members read undefined, wrong-typed members
keep their values, extra members stay visible in source order, and
objects keep their identity. The cast sets the flag that selects the
copy: the fused JSON.parse helper's slow path and the plain check call
scr_dyn_check_recover, which takes back the TypeError and parks the
value for checkedCast.fallbackTaken/fallbackTake.
A failed value that flows into a typed slot outside the region is
checked there, as any `any` value is: it continues when it fits and
throws at that use when it does not. A statement of the dynamic copy
with no `any` lowering becomes a runtime fence that throws only when a
failed value reaches it. Module-level bindings, regions with hoisted
declarations or super() calls, union targets and targets holding class instances, and
--tier=static-only (and library mode) keep the throwing cast.
`a?.b.c` on an `any` value now short-circuits only on `a`, so `.c`
throws when `a.b` is undefined, as in Node.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
A checked cast such as `JSON.parse(text) as Partial<T>` makes every member
an `X | undefined` union. When a present object failed X, the error named
only the union's own path ("expected object | undefined at $.order, got
object"), not the missing or mistyped member inside it.
When no arm of a union matches and the value is the one container kind
exactly one arm can take (an object for the union's only record arm, an
array for its only array arm, beside unit and scalar arms), the failure
block now runs that arm's builder, which throws at the deepest failing
path with its reason ("expected string at $.order.owner.id, got
number"). Other values keep the union's message.
Only the failure block of union dynCheck builders changes; the matching
path is untouched.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
superCallStmt asserted the class base before checking for a callable
base. A class that extends an ordinary function constructor has no base
class info, so the assertion held null. Node ignores the unused value;
the native compiler throws the TypeError of a non-null assertion that
held null, and failed to compile programs with such classes (for example
the Effect stream fixtures). The base is now read after that case
returns.
`const parsed: { score: number }[] = JSON.parse(doc)` printed a different
checksum from Node: the checked conversion (and the schema-directed
JSON.parse fast path) stored only the declared fields of each object in
its native record, so JSON.stringify(parsed) silently dropped `id`,
`name` and `active`, and every other reflective surface agreed.
A closed record converted from an ordinary object now keeps the source's
own properties beside it when the object has undeclared keys or holds the
declared ones out of declaration order. The runtime keeps a per-thread
table from the native record to a view of the source's own keys
(placeholders for declared keys, which the record still owns), released
through the native dispose hook when the record is freed:
- the checked record builder notes its source (scr_record_source_note);
- the schema parser parses undeclared members into the view instead of
declining, so typed parses keep their one-pass fast path;
- typed JSON.stringify writes such records in source key order, declared
fields through a generated per-shape field writer and the others through
the dyn writer;
- record capsules adopt the view and refresh it in place, so untyped reads
and writes see and persist undeclared properties;
- util.inspect and Object.keys/values/entries answer through the live view
(values/entries check the extra values into their static result type and
throw the checked-conversion TypeError when one does not fit).
Copies made by object spread, Object.assign, rest destructuring or
conversion to another record type still hold only the declared fields;
the limitations page documents this.
`checksum += parsed[i].score` (a number local plus an `any` value) failed
with SC1043 "comparing non-number, non-string values" in TypeScript, while
the expanded `checksum = checksum + parsed[i].score` compiled: the
compound lowering only routed checked-dynamic operands through the
runtime operators in JavaScript files.
Locals, record fields and array elements now lower `op=` with an untyped
right operand (or an untyped local target) exactly like `x = x op rhs`:
dyn.add / dyn.arithmetic / dyn.bitwise, then the checked conversion into
the target's declared type. Numeric operators keep Node's ToNumber
semantics; a `+=` that produces a string for a `number` target throws the
same catchable TypeError as the expanded assignment and leaves the target
unchanged (pinned in tests/harness/dyncheck.test.ts).
Remaining SC1043 refusals for arithmetic, unary, update and compound
operators now name the operator and operand types instead of the
comparison wording.
The retired-engine-763 diagnostics fixture compiles now and matches Node,
so it moves to the corpus as 5343.
Seventeen Order inputs whose shape disagrees with the target (wrong leaf
kinds at the top level, in nested records, record arrays and string
arrays; null for object and number; missing fields; object vs array at a
field and at the root; duplicate keys; truncated JSON; 1e400 and a lone
surrogate; extra nested members; reordered keys) plus an Item[] root.
The expected lines are the output of the checked-route-only build
(perf/harness); the fast path must decline or agree on every one.
- Enforce oxlint and oxfmt for owned JavaScript and TypeScript with independent CI checks.
- Preserve compiler import boundaries and protected fixtures while cleaning up lint findings.
- Standardize source formatting and validate import, fixture, and embedded-source protections.
* Expand static compilation for common Effect 4 patterns
* Run every Effect 4 fixture slice in CI
* Preserve existing corpus behavior across Effect 4 lowering
* Preserve Effect platform callbacks and native stream state
* Record new corpus baselines and retain child stdin refusals
* Retire the obsolete stateful regex diagnostic
* Preserve promise reference count layout for cycle collection
* Expand static Effect support across common APIs
* Preserve compiler parity across expanded Effect patterns
* Fix compiler regressions exposed by Effect coverage
* Bound shared type conversion traversal
* Clarify conversion contracts and tidy fixtures
* Run every Effect fixture in CI shards
* Preserve inferred array assignments in concurrent Effect programs
* Record inferred array fixture compiler ordering
- Remove C emission, debugging options, and automatic backend fallback.
- Complete LLVM lowering and native bootstrap coverage across supported targets.
- Link executables and libraries with precompiled C runtime packs, including iOS and Android.
- Add Agent connection accounting and HTTP/socket compatibility surfaces
- Support dynamic Buffer at and slice access
- Pin behavior with differential corpus coverage
- 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.
- The iteration pack's JSVAL arm is ARMED (scr_dyn_iter_pack, scr_dyn_arr_push_spread, scr_dyn_pack_push_spread_iter route through the new iter_drain ops row): the ENGINE's iterator protocol drains into a fresh DOM array — engine arrays, generators, Maps, Sets, and Symbol.iterator implementations step exactly as Node runs them, elements wrapping back scalar-normalized.
- for-of over checked-dynamic values LOWERS now (both backends): the source packs once through dyn.iterPack and a hidden index loop binds each element as a dyn value (new dyn.arrLen/dyn.arrAt accessors) — an eager snapshot, the matchAll stance. Pattern heads, pre-declared and var heads, and labeled break/continue all ride the desugar. Non-iterables throw V8's for-of CallPrinter spellings, threaded into the engine-side guard.
- The validated exit gains the jsval-element-array arm (scr_jsval_exit_jsval_arr, both backends): an 'any' value exits into 'any[]'- and 'any[] | undefined'-declared slots Array.isArray-gated, elements BY REFERENCE (identity crosses, the spine is a snapshot) — the withPlugins loadPlugins(plugins) boundary, the driver frontier's first named poison.
- Corpus 2604 and npm case jsval-iterate (package-minted Set/Map/generator/Symbol.iterator) are byte-identical to Node under both backends; dyncheck's jsval-iterate pin flips from the retired island fence to the armed answers; SAN clean over the drain/wrap/exit churn.
- Unions carrying an object/unknown-flavored arm beside dyn-subsumable siblings map to dyn wholesale; typeof and isArray narrowing dispatch natively
- Class instances, Maps, Sets, functions, promises, and regexes stay excluded so typed semantics never degrade; the component fence names the blocking sibling
- A dyn element makes the whole array the DOM value; element reads and writes ride the routed machinery
# Conflicts:
# tests/harness/dyncheck.test.ts
- Keyed reads and writes, dynCall, and method dispatch on engine-held values route through the engine, which runs its own prototypes JS-exact
- One generic host shim carries boxed dyn functions into engine calls over the uniform thunk signature
- Nullish coalescing and optional chains unfence for every dyn value, engine-held or not
- Mixed island-vs-DOM deepStrictEqual comparisons loud-fence instead of minting a fabricated failure
- The formatter driver's support slice runs past its flatMap wall
- mapType: a union with an 'object'/'unknown'/'{}'-flavored (dyn) arm beside only dyn-subsumable siblings — scalars, units, dynFrom-convertible records/arrays — maps to DYN wholesale; class/Map/Set/func/promise/regex arms keep their typed homes, and the SC2009 classifier now names the sibling that cannot ride the collapse instead of blaming the dyn arm.
- A dyn ELEMENT makes the whole array the DOM value (unknown[], object[], the plugins-slot (string | object)[]): the DOM array literal builds from TS annotations, .length on collapsed-array receivers is a DOM keyed read, element writes ride dyn.keySet (ARR index set/extend with undefined-hole padding), and for-of over dyn gets a pointed operation fence instead of the stale component story.
- Appendix-A repro 4 stops SC2009-fencing: an island plugins array wraps at the collapsed slot (dynFromJsval) and the element read reaches the loud keyed-read ladder until the routing lane arms it (dyncheck pin jsval-collapsed-union-slot).
- Corpus 2584/2585 differential both backends (guard ladder, option tables, unknown[] first-class; SAN clean); json-dyn snapshot repinned where the unknown[] declaration fence retires; conformance movers verified locally: discriminateObjectTypesOnly, unknownPropertiesAreAssignableToObjectUnion, unknownLikeUnionObjectFlagsNotPropagated.
- SEMANTICS 398 documents the collapse rule, the exact subsumable-arm domain, and the width/identity consequences (deep-copy entry, full-width JSON, per-site fences for non-subsumable values).
- 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
Chris Tate