Malte UblandClaude Opus 5.5 e12db2974f Verify checker-proven narrowings at run time
unionNarrow, downcast and caughtNarrow extracted a payload as the arm,
class or caught kind TypeScript's narrowing proved, with no runtime
check. A wrong proof read the payload as another type. Each extraction
now verifies its proof once: the union tag (for a two-arm union, that
the value does not hold the other arm, which LLVM folds under either
dominating test), the target's vtable preorder intervals (shared with
instanceof), or the caught kind or class (shared with caughtTest). A
mismatch calls scr_trap with an internal-error message from a cold
block. A correct program never reaches it: narrowings the frontend
cannot prove already lower to checked extraction, which throws the
catchable TypeError, and analyses treat these expressions as
non-throwing, so a failing guard aborts instead of unwinding.

The guards found a stale narrowing the stability analysis missed: a
binding initialized or assigned from a narrowed read whose narrowing a
callback invalidated inherits that narrowing (`const held: Expr =
current`). main segfaults on that program where Node throws a
TypeError. NarrowingStability now treats such bindings like captured
mutable ones, so their narrowed reads use checked extraction.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
2026-10-18 07:31:42 -07:00
2026-10-16 10:33:14 -05:00
2026-10-14 17:27:02 -05:00
2026-10-17 13:47:41 -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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