56 lines
1.2 KiB
Plaintext
56 lines
1.2 KiB
Plaintext
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---
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description: 'Disallow unnecessary constraints on generic types.'
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---
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> 🛑 This file is source code, not the primary documentation location! 🛑
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>
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> See **https://typescript-eslint.io/rules/no-unnecessary-type-constraint** for documentation.
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Generic type parameters (`<T>`) in TypeScript may be "constrained" with an [`extends` keyword](https://www.typescriptlang.org/docs/handbook/generics.html#generic-constraints).
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When no `extends` is provided, type parameters default a constraint to `unknown`.
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It is therefore redundant to `extend` from `any` or `unknown`.
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## Examples
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<!--tabs-->
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### ❌ Incorrect
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```ts
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interface FooAny<T extends any> {}
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interface FooUnknown<T extends unknown> {}
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type BarAny<T extends any> = {};
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type BarUnknown<T extends unknown> = {};
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class BazAny<T extends any> {
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quxAny<U extends any>() {}
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}
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const QuuxAny = <T extends any>() => {};
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function QuuzAny<T extends any>() {}
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```
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### ✅ Correct
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```ts
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interface Foo<T> {}
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type Bar<T> = {};
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class Baz<T> {
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qux<U> { }
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}
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const Quux = <T>() => {};
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function Quuz<T>() {}
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```
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## When Not To Use It
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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.
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