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An assignment narrows a binding to the assigned arm, and TypeScript keeps that narrowing across a closure or method that stores another arm. After `if (acc !== null) return acc;` the checker still types the read as the old arm, the return slot rejects the declared `T | null`, and the checked extraction threw on the value the closure stored, where Node returns it. The compiler itself has this shape (lowerDynObjectLiteral), so the native compiler aborted with "a value of another type is not representable in the target union" and closure-nullable-union-return.ts diverged. A slot that accepts the declared type minus null/undefined now reads the stale reference as NonNullable<declared>, like a binding narrowed only by the absence test. Elements and properties of array and object literals are such slots when the literal itself sits in a typed slot (annotated declaration, argument, assignment, return of a function with a declared return type). Untyped literals keep the checked extraction.
scriptc
scriptc compiles TypeScript and JavaScript to native executables and WebAssembly. It uses TypeScript's type information to compile supported code to native instructions. Static builds run without Node.js or a JavaScript engine.
For npm dependencies and any-typed code, enable --dynamic to include the embedded quickjs-ng engine. Dependency JavaScript is included at build time.
scriptc is experimental and supports a subset of JavaScript, TypeScript, and Node.js APIs. See the limitations and Node.js compatibility reference before using it for an existing project.
Installation
Install with Node.js 24 or later and npm:
$ npm install -g scriptc
The installed compiler runs natively on supported macOS, Linux, and Windows hosts. Native compilation and execution do not require Node.js. Standalone compiler archives are also available from GitHub Releases.
Executable builds require a platform linker and SDK/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}`);
Compile and run it in one step:
$ scriptc run hello.ts
hello, world
Or write a standalone executable:
$ scriptc build hello.ts -o hello
$ ./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 which operations compile statically, require dynamic execution, or are unsupported. 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
$ ./server
listening on http://localhost:8080
Use npm packages
Pass --dynamic to embed an npm package's JavaScript in the executable. The result does not 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 --dynamic -o cli
$ ./cli
hello from scriptc
Enabling --dynamic does not add support for unsupported statically typed calls. See npm dependencies for package resolution and the boundary between static and dynamic code.
Documentation
- Quickstart: installation and your first executable.
- 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.