# TS2391: Function implementation is missing or not immediately following the declaration.

> A function overload signature has no implementation, or something else sits between the overloads and the body. Add the body directly after them.

## What it means

Outside declaration files and `declare` blocks, a function or method signature without a body
is an overload, and the implementation must come immediately after the last overload. A missing
body, or another statement in between, is reported on the signature.

## Example

```ts
export function parse(text: string): number;
```

## How to fix

- Add the body to the function, or add an implementation right after the overloads.
- Move any statement that sits between the overloads and the implementation.
- If the function exists elsewhere at runtime, declare it with `declare function`.

Source: https://ts-r.dev/errors/TS2391/