@typescript-eslint/eslint-plugin/docs/rules/no-unnecessary-type-constraint.mdx

TypeScript plugin for ESLint

---
description: 'Disallow unnecessary constraints on generic types.'
---

import Tabs from '@theme/Tabs';
import TabItem from '@theme/TabItem';

> 🛑 This file is source code, not the primary documentation location! 🛑
>
> See **https://typescript-eslint.io/rules/no-unnecessary-type-constraint** for documentation.

Generic type parameters (`<T>`) in TypeScript may be "constrained" with an [`extends` keyword](https://www.typescriptlang.org/docs/handbook/generics.html#generic-constraints).
When no `extends` is provided, type parameters default a constraint to `unknown`.
It is therefore redundant to `extend` from `any` or `unknown`.

## Examples

<Tabs>
<TabItem value="❌ Incorrect">

```ts
interface FooAny<T extends any> {}

interface FooUnknown<T extends unknown> {}

type BarAny<T extends any> = {};

type BarUnknown<T extends unknown> = {};

class BazAny<T extends any> {
  quxAny<U extends any>() {}
}

const QuuxAny = <T extends any>() => {};

function QuuzAny<T extends any>() {}
```

</TabItem>
<TabItem value="✅ Correct">

```ts
interface Foo<T> {}

type Bar<T> = {};

class Baz<T> {
  qux<U>() {}
}

const Quux = <T>() => {};

function Quuz<T>() {}
```

</TabItem>
</Tabs>

## When Not To Use It

If you don't care about the specific styles of your type constraints, or never use them in the first place, then you will not need this rule.