Restrictions and reserved syntax

Nola adds little and reserves a little more. This page is the complete list of what a .tsi file refuses today, and why.

Reserved words

• ask and with are reserved words in .tsi. ask stays legal as a member or property name (obj.ask); using it as a plain identifier is NOLA1003.
• infer is contextual: a keyword only directly before function at statement or export position. T extends infer U in a conditional type is untouched.
• __nola and any identifier starting with __nola are reserved. __nola.ask(…), __nola.intents.ExtractIntent(…) and friends are what the compiler emits — not an API you call.

// not-checked — WRONG: emitted code, not a user-facing API
export infer function read(.doc: string) {
  const wrong = await __nola.ask(__nola.intents.ExtractIntent({ instruction: "the value" }), __frame);
  return wrong;
}

// read.tsi — RIGHT
export infer function read(.doc: string) {
  const v = ask ..`the value`<string>;
  return v;
}

Syntax that is reserved for a later version

The grammar is shaped to accept these; today each one is a clear error rather than a silent misparse.

You write	What happens
async infer function f(…)	parse error — an infer function is never async in source; await is already legal in its body
export default infer function f(…)	does not parse — export by name and import the name
infer on a method, arrow function or function expression	NOLA1004 — top-level function declarations only
fn(..) — the bare derive-all call	NOLA1004
const .x = … — a contextual binding inside a body	NOLA1014
. on a destructuring pattern or a defaulted parameter	NOLA1011 — use a plain identifier parameter
the removed function name`()` form	NOLA1007 — declare it with infer function

Further language features are deferred and parse as reserved today: abstract functions, type and interface intents, ask if / ask for / ask while / ask switch, and class methods. They are listed here so you recognise the error; nothing on this site documents them as available.

Runtimes

• Node ≥ 22 runs .tsi. The loader is Node’s module-hooks API, which Bun and Deno do not run — bun --bun, bun src/main.ts and deno run fail with NOLA3015. Any package manager is fine (bun install, bun run start, pnpm start, yarn start — the nola bin is a Node script); only the runtime must be Node. Built output runs anywhere Node does.
• Server-only in v0. A client bundle that imports .tsi fails the build with NOLA4001; executing an ask in a browser is NOLA3013. Move the import behind a server boundary (SSR entry, route handler, server action).

Not restrictions

Things people assume are forbidden and are not:

• await inside an infer function — legal, for any ordinary promise.
• Constructing an extractor at module level — legal and inert; only ask is position-restricted.
• Several contextual parameters on one function — legal; they compose into one block.
• Calling one infer function from another with ask otherFn(…) — legal; that is how you compose them.

Next: nola.config.ts