Malte UblandClaude Opus 5.5
ea23feeb21
`void | Promise<A> | Promise<void> | Decision` (the agent-loop `finishTurn` hook, codemode's remote client) had no representation: a union arm's index is its runtime tag and a promise arm's tag IS the `instanceof Promise` test, so a second promise arm had no tag. The union was refused (SC2009) and every use site inherited the blocker. JavaScript cannot tell the arms apart: `instanceof Promise` answers true for both and `await` settles to either payload. The union therefore maps to one promise arm `Promise<A | undefined>`: payloads join like union arms (`void` becomes the undefined unit, an already-union payload flattens, identical payloads dedupe, a checked-dynamic payload absorbs the arms the dynamic representation holds faithfully). A payload with no union arm home (a RegExp payload, a promise-of-a-promise) keeps the whole union fenced, and the refusal now says why. A `Promise<A>` value flowing into the merged arm converts with the existing checked promise-payload widening (promisePayloadWidens / promiseWiden): the promise keeps its identity and its settlement turn, and the settled payload is checked against the payload slot. Cost: the merge only runs for a union that already has two promise arms, which is refused today. Every other union interns the same arms in the same order, so a fully typed program without such a union compiles to identical IR. Corpus 8414-promise-union-arms pins identity through the union slot, `instanceof Promise` narrowing, `await`, `.then`, the void arm, the rejection path and a non-promise data arm. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
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
- Introduction: what scriptc is and what you can build.
- Quickstart: installation and your first executable.
- Coverage reports: check whether an existing program compiles.
- Platform support: cross-compilation and WebAssembly.
- CLI reference: commands, options, and output formats.
- Native program objects: use compiler output in external builds.
- Native FFI: call C ABI functions from compiled programs.
- WebAssembly modules: build and embed WASI modules.
- Examples: programs and integration examples in this repository.
Contributing
See CONTRIBUTING.md for source setup, testing, native artifact builds, and docs development.