Malte UblandClaude Opus 5.5 3328ed2aa7 Lower union member reads the checker narrowed away
Reading a member off a union-typed value is what most pi refusals at
`SC1090` came down to: `credential.type` on `ApiKeyCredential |
OAuthCredential`, `session.role`, `entry.timestamp`, `tool.operations`,
`arms.length`, `renderer.hasOverlayEntries`.

Three read shapes reach the same dispatch and now answer:

- A checker-NARROWED receiver keeps the wider union it stores, because
  lowering erases flow narrowing (`stored?.type` after the earlier arm
  returned, `(entry as { role: string }).role`). The dispatcher now reads
  the member off whichever arm the value holds — an arm that does not
  declare it answers undefined, exactly Node's get — and narrows the
  answer to the checker's type, which traps on an arm the narrowing
  ruled out (types do not lie). This fallback sits after every existing
  lowering, so only refusals gain one.

- A member the arms answer through an ACCESSOR (a getter inherited from
  a shared base class, `renderer.hasOverlayEntries`) has no field slot
  `unionDisc` could read, so the read dispatches on the tag and calls
  each arm's own getter. Data-field unions keep their `unionDisc`
  lowering.

- `.length` on a union of arrays and strings (`Model[] | ModelRef[]`,
  `string[] | Buffer[]`) dispatches on the tag and answers each arm's
  own length.

The member read moves out of `lowerUnionProperty` into
`lowerUnionValueRead`, which both entry points share, and
`missingFieldAsUndefined` threads the narrowed-receiver get semantics
through the keyed read.

Corpus 8520/8521/8522 pin the three shapes differentially.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
2026-10-29 05:38:11 -07:00
2026-10-27 23:21:09 -05:00
2026-10-28 20:50:23 -05:00
2026-10-16 10:33:14 -05:00
2026-10-27 23:21:09 -05:00
2026-10-14 17:27:02 -05:00
2026-10-25 11:26:13 -05:00
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2026-10-27 16:45:14 -05:00
2026-10-25 21:21:26 -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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