# TS8037: Type satisfaction expressions can only be used in TypeScript files.

> A `satisfies` expression appears in a JavaScript file. Remove it, or use JSDoc `@satisfies`.

## What it means

`expr satisfies Type` is TypeScript syntax and can't appear in a `.js` file.

ts-r's parser reports this code when it reads `.js` files with tsc's rules for TypeScript syntax in JavaScript. `ts-r-check` doesn't report it yet: today it parses `.js` files with the plain JavaScript grammar and reports a syntax error at the same place instead.

## Example

```js
const config = { port: 3000 } satisfies Config;
```

## How to fix

- Remove `satisfies Type`; JSDoc's `/** @satisfies {Config} */` keeps the check.
- Rename the file to `.ts` if it's meant to be TypeScript.

Source: https://ts-r.dev/errors/TS8037/