Malte Ubl 2fa733b106 Append to string array elements and o.f = o.f + x fields in place
"Append to strings in place for fields, concat chains and character
codes" made `obj.f += s` linear by handing the field's reference to a
local before the concat. Two neighbouring forms still copied the whole
string on every append, so their loops stayed quadratic:

- `parts[i] += s` on a `string[]`: the old element reached the concat
  through a retained snapshot (the hidden %compoundOld local) while the
  slot still held it. 1.6M appends spread over four slots took 11 s.
- `o.f = o.f + s` written out: the field read retains a snapshot and
  the field keeps its reference until the store.

A statement `a[i] += rhs` on a `string[]` now lowers to
`a[i] = (hole ? "undefined" : a[i]) + rhs` with the array and index saved
first (evaluation order unchanged). The backend recognizes that store and
the direct `recv.f = recv.f + suffix` on a plain string class or record
field. After the snapshot and suffix are evaluated and the store guard
ran, a field unlinks and releases its current value; an array slot in
the hole-free prefix that still holds the snapshot is swapped for the
immortal empty string and released. The concat then appends in place
when nothing else holds the string, and the result is stored as before.
Both paths unlink only when the snapshot is frame-owned (or immortal).

Aliases, interned literals, throwing suffixes, suffixes that read or
replace the field or element, rebound receivers and indices, holes,
appends past the end and appends that grow the array keep their
semantics (tests/corpus/string-field-append.ts, which also pins the
field `+=` forms).
2026-10-16 07:00:37 -07:00
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2026-10-16 01:29:54 -05:00
2026-07-22 18:08:04 -05:00
2026-07-22 18:08:04 -05:00

scriptc

Vercel Labs Experiment npm version: scriptc License: Apache-2.0 npm downloads per month: scriptc

scriptc compiles TypeScript and JavaScript to native executables and WebAssembly. It uses the types checked by the TypeScript compiler to generate machine code, and the output runs without Node.js installed. npm packages your program imports compile along with it. Code scriptc can't compile is reported at build time with a diagnostic and, where available, a rewrite hint.

scriptc is experimental and supports a subset of JavaScript, TypeScript, and Node.js APIs. Run scriptc coverage on an existing program to see how much of it compiles, and see the limitations and Node.js compatibility reference for details.

Installation

Install with Node.js 24 or later and npm:

$ npm install -g scriptc

The installed compiler runs natively on macOS, Linux, and Windows. Node.js is needed only to install it and to run WASI modules with scriptc run. Standalone compiler archives are also available from GitHub Releases.

Building executables requires a linker and the platform SDK or sysroot. See the quickstart for prerequisites and platform support for host requirements, cross-compilation, and WebAssembly.

Build a program

Create hello.ts:

const who = process.argv.length > 2 ? process.argv[2] : "world";
console.log(`hello, ${who}`);

scriptc run compiles the file and runs the result:

$ scriptc run hello.ts
hello, world

scriptc build writes an executable:

$ scriptc build hello.ts -o hello >/dev/null
$ ./hello scriptc
hello, scriptc

These examples use POSIX shell syntax. On Windows, build hello.exe and run it with .\hello.exe.

Use scriptc coverage hello.ts to check what compiles before you build. See coverage reports for details.

Use Node APIs

Supported Node APIs compile to the native runtime. For example, server.ts:

import { createServer } from "node:http";

const server = createServer((req, res) => {
  res.setHeader("content-type", "application/json");
  res.end(JSON.stringify({ path: req.url }));
});

server.listen(8080, () => {
  console.log("listening on http://localhost:8080");
});
$ scriptc build server.ts -o server >/dev/null
$ ./server
listening on http://localhost:8080

Use npm packages

npm packages compile into the executable with your code, so it doesn't read node_modules at runtime.

Create cli.ts:

import pc from "picocolors";

console.log(pc.green("hello from scriptc"));
$ npm install picocolors
$ scriptc build cli.ts -o cli >/dev/null
$ ./cli
hello from scriptc

Package support is partial. See npm dependencies for which packages compile and how to check them.

Documentation

Contributing

See CONTRIBUTING.md for source setup, testing, native artifact builds, and docs development.

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Readme Apache-2.0
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