TypeScript

TypeScript transpile-only is Stable (G36). The contract is docs/TYPESCRIPT_CONTRACT.md.

What runs

• Entry files ending in .ts, .tsx, .mts, .cts, or .jsx.
• Files loaded with CommonJS require that use those extensions.
• amber eval snippets that look like TypeScript or JSX.

// app.ts
type Status = "ok" | "error";

function report(status: Status): string {
  return `status=${status}`;
}

console.log(report("ok"));

amber run app.ts

How it works

Amber uses oxc to strip types and emit JavaScript, then runs it on V8.

• using declarations and Stage 3 decorators are lowered to ES2022.
• TSX emits classic React.createElement calls.
• When a source map is active, stack traces point at .ts lines.
• A parse or transform error fails the run. Amber does not guess.

What it does not do

This is not tsc. These are permanent non-goals for this surface:

• Type checking. A file with type errors still runs.
• tsconfig.json programs, path aliases, and project references.
• The automatic JSX runtime and emitDecoratorMetadata.

Run tsc --noEmit in CI if you need type errors to fail the build.

Type definitions for Amber APIs

amber types prints type definitions for Amber built-ins. That command is not classified in the scope page yet, so treat its output as Experimental.