TypeScript/Node.js Parity Gaps

Everything the Perry compiler is missing for absolute parity with Node.js running TypeScript, as of v0.4.56.

Current status: 100% pass rate on 87 parity tests (27 edge-case + 60 existing). The gaps below are features NOT covered by those tests — they either aren't tested or aren't implemented.

Language Features

Generators & Iterators

Feature	Status	Notes
`function*` syntax	Parsed	`Expr::Yield` exists in HIR but no generator object protocol
`yield` / `yield*`	Partial	Expression exists but `.next()` / `.return()` / `.throw()` not callable on result
Generator iterator protocol	Missing	`function*` doesn't produce an object with `.next()`
`Symbol.iterator`	Missing	No custom iterable protocol — `for...of` only works on arrays, strings, Maps, Sets
`Symbol.asyncIterator`	Missing	No async iterable protocol
`async function*`	Missing	Async generators not supported
`for await...of`	Missing	Async iteration not supported

Symbols

Feature	Status	Notes
`Symbol()` constructor	Missing	No runtime Symbol creation
`Symbol.iterator`	Missing	Can't make custom iterables
`Symbol.toPrimitive`	Missing	Can't customize type coercion
`Symbol.hasInstance`	Missing	Can't customize `instanceof`
`Symbol.toStringTag`	Missing	Can't customize `Object.prototype.toString`
`Symbol.species`	Missing	Can't customize derived constructors
Well-known symbols	Missing	None of the `Symbol.*` constants exist

Metaprogramming

Feature	Status	Notes
`Proxy`	Missing	Explicitly skipped — would require trap checks on every property access
`Reflect`	Missing	No reflection API
`eval()`	Missing	Fundamentally hard for AOT compiler — would need bundled interpreter
`new Function('...')`	Missing	Same constraint as eval
`Object.defineProperty()`	Missing	No property descriptor model
`Object.getOwnPropertyDescriptor()`	Missing	No property descriptor model
`Object.getPrototypeOf()`	Missing	No prototype chain at runtime
`Object.setPrototypeOf()`	Missing	No prototype mutation
`Object.create()`	Exists	But limited — no property descriptors argument

Classes (advanced)

Feature	Status	Notes
Private methods `#method()`	Missing	Private fields `#field` work but not methods
Static class blocks `static { ... }`	Missing	Static field initializers work but not blocks
Class decorators (stage 3)	Partial	Basic decorator syntax parsed, limited runtime support
`abstract` classes	Missing	No enforcement — abstract methods not checked

Async (advanced)

Feature	Status	Notes
`for await...of`	Missing
`Promise.allSettled()`	Missing
`Promise.any()`	Missing
`Promise.race()`	Partial	Runtime function exists (v0.4.47) but may have edge cases
Async generators	Missing	`async function*` not supported
Async disposal `await using`	Missing	TC39 stage 3

Error Handling (advanced)

Feature	Status	Notes
`Error.cause`	Missing	`new Error("msg", { cause: err })` not supported
`AggregateError`	Missing	Used by `Promise.any()`
`Error.captureStackTrace`	Missing	V8-specific, not in spec
Custom error `.stack` formatting	Missing	Stack traces are basic

Dynamic Features

Feature	Status	Notes
Dynamic `import()`	Broken	Returns undefined with warning
`with` statement	Missing	Intentional — deprecated in strict mode
Computed property access on unknown types	Partial	Works for known types, falls through for `any`
`arguments` object	Missing	Arrow functions don't have it (correct), regular functions should
Tagged template literals	Missing	tag`string` syntax

Built-in Objects & Methods

Array

Method	Status
`push`, `pop`, `shift`, `unshift`	✓
`slice`, `splice`	✓
`map`, `filter`, `find`, `findIndex`	✓
`forEach`, `some`, `every`	✓
`reduce`, `reduceRight`	✓ reduce only (no reduceRight)
`sort` (with and without comparator)	✓
`reverse`	✓
`flat`, `flatMap`	✓
`fill`	✓
`concat`	✓
`join`	✓
`indexOf`, `lastIndexOf`	✓
`includes`	✓
`isArray`	✓
`from`, `from(iter, mapFn)`	✓
`of`	Missing
`at()`	Missing
`findLast()`	Missing
`findLastIndex()`	Missing
`toReversed()`	Missing
`toSorted()`	Missing
`toSpliced()`	Missing
`with()`	Missing
`copyWithin()`	Missing
`entries()`, `keys()`, `values()`	Missing (as iterators)
`Array.fromAsync()`	Missing
`group()` / `groupToMap()`	Missing

String

Method	Status
`charAt`, `charCodeAt`	✓
`slice`, `substring`, `substr`	✓
`trim`, `trimStart`, `trimEnd`	✓
`toLowerCase`, `toUpperCase`	✓
`replace`, `replaceAll`	✓
`split` (string and regex)	✓
`match`, `matchAll`	✓
`search`	✓
`indexOf`, `lastIndexOf`	✓
`includes`, `startsWith`, `endsWith`	✓
`padStart`, `padEnd`	✓
`repeat`	✓
`fromCharCode`	✓
`at()`	Missing
`normalize()`	Listed but may not work
`localeCompare()`	Missing (needs Intl)
`toLocaleLowerCase()` / `toLocaleUpperCase()`	Missing (needs Intl)
`codePointAt()`	Missing
`fromCodePoint()`	Missing
`raw()`	Missing
`isWellFormed()` / `toWellFormed()`	Missing

Object

Method	Status
`keys()`, `values()`, `entries()`	✓
`assign()`	✓
`create()`	✓ (basic)
`freeze()`, `seal()`, `preventExtensions()`	No-ops (accepted but don't enforce)
`fromEntries()`	Missing
`is()`	Missing
`hasOwn()`	Missing
`defineProperty()` / `defineProperties()`	Missing
`getOwnPropertyDescriptor()` / `getOwnPropertyDescriptors()`	Missing
`getOwnPropertyNames()` / `getOwnPropertySymbols()`	Missing
`getPrototypeOf()` / `setPrototypeOf()`	Missing
`isFrozen()` / `isSealed()` / `isExtensible()`	Missing

Map & Set

Method	Status
`new Map()`, `new Map(entries)`	✓
`get`, `set`, `has`, `delete`, `clear`	✓
`size`	✓
`forEach`	✓
`keys()`, `values()`, `entries()`	✓ (return arrays, not iterators)
`new Set()`, `new Set(array)`	✓
`add`, `has`, `delete`, `clear`	✓
`size`	✓
`forEach`	✓
`values()`	✓ (returns array)
`intersection()`, `union()`, `difference()`	Missing (ES2025)
`isSubsetOf()`, `isSupersetOf()`, `isDisjointFrom()`	Missing (ES2025)
`symmetricDifference()`	Missing (ES2025)
WeakMap	Falls back to Map (no weak references)
WeakSet	Falls back to Set (no weak references)

RegExp

Feature	Status
Literal patterns `/abc/flags`	✓
`.test()`	✓
`.match()` with groups	✓
`.match()` with global flag	✓
`.matchAll()`	✓
`.split(regex)`	✓
`.search(regex)`	✓
`.replace(regex, string)`	✓
`.exec()`	Missing (use `.match()` instead)
`lastIndex` property	Missing
Named capture groups `(?<name>...)`	Missing
Lookbehind assertions `(?<=...)`	Depends on Rust regex crate
Unicode property escapes `\p{...}`	Depends on Rust regex crate
`d` flag (indices)	Missing
`v` flag (unicodeSets)	Missing

Number & Math

Feature	Status
All Math methods (floor, ceil, round, abs, sqrt, pow, etc.)	✓
`Math.trunc`, `Math.sign`	✓
`Math.random()`	✓
`Math.clz32()`	Missing
`Math.fround()`	Missing
`Math.cbrt()`	Missing
`Math.expm1()` / `Math.log1p()`	Missing
`Math.hypot()`	Missing
`Number.MAX_SAFE_INTEGER` etc.	✓
`Number.isNaN`, `isFinite`, `isInteger`, `isSafeInteger`	✓
`parseInt`, `parseFloat`	✓
`toFixed`, `toString(radix)`	✓
`toPrecision()`	Missing
`toExponential()`	Missing
Numeric separators `1_000_000`	✓ (handled by SWC parser)

Date

Feature	Status
`new Date()`, `Date.now()`	✓
`getFullYear/Month/Date/Hours/Minutes/Seconds/Milliseconds`	✓
`toISOString()`	✓
`getTime()`	✓
`setFullYear/Month/Date/Hours/Minutes/Seconds`	Missing
`toLocaleDateString()` / `toLocaleTimeString()`	Missing (needs Intl)
`toDateString()` / `toTimeString()`	Missing
`getTimezoneOffset()`	Missing
`toJSON()`	Missing
`Date.parse()`	Missing
`Date.UTC()`	Missing

JSON

Feature	Status
`JSON.parse()`	✓
`JSON.stringify()`	✓
`JSON.stringify(value, replacer)`	Missing (replacer function)
`JSON.stringify(value, null, space)`	Missing (pretty-print)
`JSON.parse(text, reviver)`	Missing (reviver function)

Promise

Feature	Status
`new Promise(executor)`	✓
`.then()`, `.catch()`, `.finally()`	✓
`Promise.resolve()`, `Promise.reject()`	✓
`Promise.all()`	✓
`Promise.race()`	Partial (v0.4.47)
`Promise.allSettled()`	Missing
`Promise.any()`	Missing
`Promise.withResolvers()`	Missing
`await`	✓

Global APIs

Timers

API	Status
`setTimeout(fn, ms)`	✓
`setInterval(fn, ms)`	✓
`clearTimeout(id)`	Missing
`clearInterval(id)`	Missing
`setImmediate(fn)`	Missing
`clearImmediate(id)`	Missing

Console

Method	Status
`console.log()`	✓ (with spread)
`console.error()`	✓
`console.warn()`	✓
`console.table()`	Missing
`console.dir()`	Missing
`console.time()` / `timeEnd()` / `timeLog()`	Missing
`console.group()` / `groupEnd()`	Missing
`console.trace()`	Missing
`console.assert()`	Missing
`console.count()` / `countReset()`	Missing
`console.clear()`	Missing

Encoding

API	Status
`TextEncoder`	Missing
`TextDecoder`	Missing
`atob()`	Missing
`btoa()`	Missing
`encodeURIComponent()`	✓
`decodeURIComponent()`	✓
`encodeURI()` / `decodeURI()`	Missing

Other Globals

API	Status
`structuredClone()`	Missing
`queueMicrotask()`	Missing
`AbortController` / `AbortSignal`	Missing
`performance.now()`	Missing
`URL` / `URLSearchParams`	✓
`WeakRef`	Missing
`FinalizationRegistry`	Missing
`Intl` (entire namespace)	Missing

Node.js Standard Library

fs (File System)

Function	Status
`readFileSync(path)`	✓ (returns Buffer)
`readFileSync(path, encoding)`	✓ (returns string)
`writeFileSync(path, data)`	✓
`appendFileSync(path, data)`	✓
`existsSync(path)`	✓
`mkdirSync(path)`	✓
`unlinkSync(path)`	✓
`rmSync(path, { recursive })`	✓
`statSync()` / `lstatSync()`	Missing
`readdirSync()`	Missing
`renameSync()`	Missing
`copyFileSync()`	Missing
`chmodSync()` / `chownSync()`	Missing
`watchFile()` / `watch()`	Missing
`createReadStream()` / `createWriteStream()`	Missing (needs streams)
All async variants (`readFile`, `writeFile`, etc.)	Missing
`fs/promises`	Missing

path

Function	Status
`join()`	✓
`dirname()`	✓
`basename()`	✓
`extname()`	✓
`resolve()`	✓
`isAbsolute()`	✓
`relative()`	Missing
`parse()`	Missing
`format()`	Missing
`normalize()`	Missing
`sep` / `delimiter`	Missing
`posix` / `win32`	Missing

crypto

Function	Status
`randomBytes(n)`	✓
`randomUUID()`	✓
`createHash('sha256')` (via helper)	✓ (as `sha256()` / `md5()`)
`createHash()` (general)	Missing
`createHmac()`	Missing
`createCipheriv()` / `createDecipheriv()`	Missing
`pbkdf2()` / `pbkdf2Sync()`	Missing
`scrypt()` / `scryptSync()`	Missing
`sign()` / `verify()`	Missing
`generateKeyPairSync()`	Missing
`subtle` (SubtleCrypto)	Missing
`getRandomValues()`	Missing

process

Feature	Status
`process.exit(code)`	✓
`process.env`	✓ (static and dynamic access)
`process.argv`	✓
`process.cwd()`	✓
`process.uptime()`	✓
`process.memoryUsage()`	✓
`process.platform`	✓
`process.arch`	✓
`process.pid`	Missing
`process.ppid`	Missing
`process.stdin` / `stdout` / `stderr`	Missing (as streams)
`process.on('exit', fn)`	Missing
`process.on('uncaughtException', fn)`	Missing
`process.nextTick()`	Missing
`process.hrtime()` / `process.hrtime.bigint()`	Missing
`process.version`	Missing
`process.versions`	Missing
`process.kill()`	Missing
`process.chdir()`	Missing

child_process

Function	Status
`execSync()`	✓
`spawnSync()`	✓
`spawn()`	✓ (basic)
`exec()`	✓ (basic)
Full stdio piping	Missing
`.on('data')` event pattern	Missing
`.stdin.write()`	Missing
`fork()`	Missing

os

Function	Status
`platform()`, `arch()`, `hostname()`	✓
`homedir()`, `tmpdir()`	✓
`totalmem()`, `freemem()`	✓
`uptime()`, `type()`, `release()`	✓
`cpus()`	✓
`networkInterfaces()`	✓
`userInfo()`	✓
`EOL`	✓
`endianness()`	Missing
`loadavg()`	Missing

http / https

Feature	Status
`fetch()` global	✓ (basic GET/POST)
`Response.json()` / `.text()` / `.arrayBuffer()`	Missing
`Response.headers`	Missing
`Response.status` / `.statusText` / `.ok`	Missing
`Headers` class	Missing
`Request` class	Missing
`FormData`	Missing
`http.createServer()`	Missing (use Fastify integration instead)
`http.request()` / `http.get()`	Missing

stream

Feature	Status
`Readable`	Missing
`Writable`	Missing
`Transform`	Missing
`Duplex`	Missing
`pipeline()`	Missing
`finished()`	Missing
Async iteration on streams	Missing

events

Feature	Status
`EventEmitter` class	✓ (basic)
`.on()` / `.emit()`	✓
`.once()`	Missing
`.off()` / `.removeListener()`	Missing
`.removeAllListeners()`	Missing
`.listenerCount()`	Missing
`.prependListener()`	Missing
`events.once()` (static)	Missing

buffer

Feature	Status
`Buffer.from(string, encoding)`	✓
`Buffer.alloc(size)`	✓
`Buffer.concat()`	✓
`Buffer.isBuffer()`	✓
`.toString(encoding)`	✓
`.length`	✓
`.slice()` / `.subarray()`	✓
`.copy()`	✓
`.fill()`	✓
`.equals()`	✓
Indexed `buf[i]` get/set	✓
`.readUInt8/16/32()` etc.	Missing
`.writeUInt8/16/32()` etc.	Missing
`.readBigInt64()` etc.	Missing
`.compare()`	Missing
`.swap16/32/64()`	Missing
`.indexOf()` / `.includes()`	Missing

Modules not implemented at all

Module	Notes
`util`	`promisify`, `inspect`, `types`, `format`
`assert`	Testing assertions
`zlib`	Compression
`dns`	DNS resolution
`tls`	TLS/SSL
`cluster`	Multi-process
`worker_threads`	Worker threads (Perry has its own `perry/thread`)
`readline`	Interactive input
`querystring`	URL query parsing (use `URLSearchParams` instead)
`timers/promises`	Timer promises
`perf_hooks`	Performance measurement
`async_hooks`	Partial (AsyncLocalStorage exists)
`diagnostics_channel`	Diagnostics
`inspector`	V8 inspector
`vm`	Virtual machine contexts
`string_decoder`	String decoding
`punycode`	Unicode encoding
`domain`	Error domains (deprecated)
`v8`	V8 engine API
`trace_events`	Tracing

Architecture Constraints

These are features that are fundamentally difficult for an AOT native compiler:

eval() / new Function() — requires a runtime interpreter. Perry has QuickJS fallback but it's opt-in.
Proxy/Reflect — every property access would need a trap check. Devastating for performance.
Full Symbol.iterator protocol — requires all for...of loops to go through a .next() call chain instead of direct indexed access.
Dynamic import() — requires lazy compilation or pre-bundling. Perry resolves all imports at compile time.
with statement — deprecated in strict mode, would break all scope resolution optimizations.
Full prototype chain — Perry uses flat field arrays, not prototype chains. Object.getPrototypeOf() etc. are impossible without restructuring object layout.
Full Intl — requires ICU data (~27MB) or system ICU linkage.
SharedArrayBuffer/Atomics — Perry uses deep-copy semantics across threads. Shared mutable memory would require a different threading model.

Summary Statistics

Category	Implemented	Missing	Coverage
Core language syntax	48/52	4	92%
Built-in object methods	~120/180	~60	67%
Node.js std lib functions	~65/200+	~135+	~30%
Global APIs	~15/30	~15	50%
Overall language parity			~85%
Overall Node.js API parity			~35%

The language itself is nearly complete. The gap is primarily in the Node.js standard library, the Intl namespace, advanced async patterns (generators, async iterators), and metaprogramming (Symbol, Proxy, Reflect).

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