# TSR1003: Async function passed where '…' expects a function returning 'void'; its promise is never handled.

> An async function is passed where a function returning void is expected, so its promise is never handled. Use a loop with await or Promise.all.

## What it means

An `async` function, or any function returning a promise, may not be passed where the parameter's type returns `void`: the callee ignores the returned promise, so rejections are lost. `items.forEach(async ...)` is the common case. It's reported at the function argument.

## Example

```ts
// forEach ignores the promises its callback returns.
async function save(x: string): Promise<void> {
  console.log(x);
}
const items: string[] = ["a", "b"];
items.forEach(async (i) => { await save(i); }); // @expect TSR1003
export {};
```

## How to fix

- Use `for...of` with `await` inside an async function.
- Or map to promises and wait for them: `await Promise.all(items.map(async (i) => save(i)))`.
- Or handle errors inside a non-async callback: `items.forEach((i) => { save(i).catch(report); })`.

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/TSR1003/