Chris Tate d99fc851e6 Type untyped JavaScript Maps, Sets and arrays from their uses
In a JavaScript file, `const m = new Map()`, `new Set()` and `[]` type as
Map<any, any>, Set<any> and any[], so every use lowered to the
checked-dynamic collection operations: boxed keys and values, generic
method dispatch, and dynamic arithmetic on what they returned.

js-collection-types.ts proves types for such bindings from their uses.
A `const` qualifies when every reference is a direct use of the
collection:
- for a Map: get/has/delete/clear, size, and set as a statement;
- for a Set: has/delete/clear, size, and add as a statement;
- for an array: push/pop/shift/at/includes/indexOf/join and length.

The value then never leaves the binding. Its key, value or element type
is the one primitive (string, number or boolean) of every expression the
program writes. That is found by a fixed point that types `m.get(k) ?? d`,
arithmetic, comparisons and constants defined from them, and it requires
lookups of the same type. Any other reference (passing, returning,
storing, exporting, iterating, inspecting, an optional call), a direct
`eval` in the file, or any doubt keeps the binding untyped.

A proven binding answers the lowerer's typeOf with a carrier type
declared in scriptc-overrides.d.ts, which only the lowering program
includes. `new Map()` and `new Set()` adopt it, so the binding lowers as
the typed Map<K, V>, Set<K> or T[], as a JSDoc @type would make it.

7985 covers the typed cases and every refusal.
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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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GitHub Trending: vercel-labs/scriptc
Readme Apache-2.0
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