`{ ...u, k: v }` where `u` is a union of records (`{ ...msg, content }` in
a message-mapping switch, `{ ...command, id } as Cmd`, `{ ...base, entries }
as A | B`) is typed by TypeScript as one spread per arm of `u`, but the
frontend mapped the literal to the union and refused with SC2003 ("a spread
merge over union-typed sources"). The only union-source spreads that lowered
were shared-field overrides and the single-record-arm present test.
lowerDistributedUnionSpread builds the literal the way the checker types it.
The source evaluates once into a hidden local; a tag dispatch builds the
running arm's literal with that arm as the spread source, at the destination
arm the discriminant's last writer picks, else the source arm itself, else
the one arm whose keys are exactly the keys the literal writes. Every key a
contributor may write must be a field of the destination, so a genuine merge
(`{ ...http, ...patch }` where the patch can carry a stdio-only key) keeps
the refusal instead of silently dropping keys. A stored source the checker
narrowed converts through the checked re-tag first, so an excluded arm throws
the catchable TypeError.
Cost: the function runs only where lowerObjectLiteral would have refused;
the new `exact` parameter defaults to false and the new
`spreadArmOverrides` map is empty outside the dispatch, so every existing
literal lowers to the same IR.
`fix/records-literals` changes the same field-desugar capture (it adds a
`checkedSpreadSource` block around it). This commit deliberately keeps the
per-arm source as the expression `(lowerer.spreadArmOverrides.get(srcNode)
?? lowerer.lowerExpr(srcNode))` inside that capture, so the merge keeps
records-literals' `let srcLowered` plus its checkedSource block and applies
the override inside the same expression, as the design specifies.
Pi sites: execution.ts:431, agent-session.ts:3795, runner.ts:1048,
model-resolver.ts:216, sdk.ts:324, session-manager.ts:538, rpc-client.ts:577.
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.