# TSR1301: '…' can throw '…', which is not in its '@throws' tags. Catch it or add a '@throws' tag for it.

> A function with '@throws' tags can throw something its tags don't list. Catch it, or add a '@throws' tag for it.

## What it means

In sound mode throwing is part of a function's signature. A function with `@throws {T}` JSDoc tags must not let anything escape that isn't assignable to the union of the tagged types. It's reported at the `throw`, or at the call it escapes from.

## Example

```ts
// The function throws a type its tag doesn't list.
class NotFound extends Error {
  readonly code = "NOT_FOUND";
}
class Timeout extends Error {
  readonly code = "TIMEOUT";
}
/** @throws {NotFound} */
function find(id: string): string {
  if (id === "slow") throw new Timeout("slow"); // @expect TSR1301
  if (id === "") throw new NotFound("missing");
  return id;
}
export const v: string = find("a");
```

## How to fix

- Catch the exception inside the function.
- Or add a tag for it: `/** @throws {NotFound | Timeout} */`.
- For bugs that should never happen, use `panic(message)` from `@ts-r.dev/guard`, which is unchecked.

Sound mode is defined in [design record 0007](https://github.com/Webb-Ventures/typescript-rust/blob/main/docs/design/0007-sound-mode.md) (accepted 2026-10-15).

Source: https://ts-r.dev/errors/TSR1301/