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# prefer-type-error

[Added in v0.9.3](https://github.com/web-infra-dev/rslint/releases/tag/v0.9.3)
## Configuration

| Preset                              | Configured Value |
| ----------------------------------- | ---------------- |
| ✅ unicornPlugin.configs.recommended | `"error"`        |


```ts title=rslint.config.ts
import { defineConfig, unicornPlugin } from '@rslint/core';

export default defineConfig([
  unicornPlugin.configs.recommended,
  {
    rules: {
      'unicorn/prefer-type-error': 'error',
    },
  },
]);
```

## Rule Details

Require `TypeError` instead of the generic `Error` when an `if` condition is exclusively checking a value's type and the branch contains only that throw.

The rule recognizes `typeof`, non-error `instanceof` checks, the global `isNaN()` and `isFinite()` functions, and common `.isType()`-style helpers used by JavaScript libraries. Existence checks such as `typeof window !== 'undefined'` are not treated as type checks.

Examples of **incorrect** code:

```javascript
if (Array.isArray(value)) {
  throw new Error('Expected a non-array value.');
}
```

Examples of **correct** code:

```javascript
if (Array.isArray(value)) {
  throw new TypeError('Expected a non-array value.');
}
```

## Options

This rule has no options. It is enabled at `error` severity in `unicornPlugin.configs.recommended`.

## Differences from upstream

Rslint resolves built-in names before offering the rewrite. A locally shadowed `Error` is not reported, and bare `isNaN` or `isFinite` calls are recognized only when they resolve to the environment globals. If `TypeError` is unavailable or locally shadowed, the diagnostic is still reported but the autofix is withheld rather than rewriting to a different binding.

These checks avoid binding-changing autofixes while preserving the upstream behavior for normal global built-ins.

## Original Documentation

- [eslint-plugin-unicorn: prefer-type-error](https://github.com/sindresorhus/eslint-plugin-unicorn/blob/v75.0.0/docs/rules/prefer-type-error.md)
- [Source code](https://github.com/sindresorhus/eslint-plugin-unicorn/blob/v75.0.0/rules/prefer-type-error.js)