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noUselessTypeConstraint

诊断类别:lint/complexity/noUselessTypeConstraint

¥Diagnostic Category: lint/complexity/noUselessTypeConstraint

自从:v1.0.0

¥Since: v1.0.0

来源:

¥Sources:

禁止使用 anyunknown 作为类型约束。

¥Disallow using any or unknown as type constraint.

TypeScript 中的通用类型参数(<T>)可能会受到 extends 的限制。提供的类型必须是提供的约束的子类型。所有类型都是 anyunknown 的子类型。因此,从 anyunknown 扩展是无用的。

¥Generic type parameters (<T>) in TypeScript may be constrained with extends. A supplied type must then be a subtype of the supplied constraint. All types are subtypes of any and unknown. It is thus useless to extend from any or unknown.

¥Examples

¥Invalid

interface FooAny<T extends any> {}
code-block.ts:1:20 lint/complexity/noUselessTypeConstraint  FIXABLE  ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

Constraining a type parameter to any or unknown is useless.

> 1 │ interface FooAny<T extends any> {}
^^^^^^^^^^^
2 │

All types are subtypes of any and unknown.

Safe fix: Remove the constraint.

1 │ interface·FooAny<T·extends·any>·{}
------------
type BarAny<T extends any> = {};
code-block.ts:1:15 lint/complexity/noUselessTypeConstraint  FIXABLE  ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

Constraining a type parameter to any or unknown is useless.

> 1 │ type BarAny<T extends any> = {};
^^^^^^^^^^^
2 │

All types are subtypes of any and unknown.

Safe fix: Remove the constraint.

1 │ type·BarAny<T·extends·any>·=·{};
------------
class BazAny<T extends any> {
}
code-block.ts:1:16 lint/complexity/noUselessTypeConstraint  FIXABLE  ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

Constraining a type parameter to any or unknown is useless.

> 1 │ class BazAny<T extends any> {
^^^^^^^^^^^
2 │ }
3 │

All types are subtypes of any and unknown.

Safe fix: Remove the constraint.

1 │ class·BazAny<T·extends·any>·{
------------
class BazAny {
quxAny<U extends any>() {}
}
code-block.ts:2:12 lint/complexity/noUselessTypeConstraint  FIXABLE  ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

Constraining a type parameter to any or unknown is useless.

1 │ class BazAny {
> 2 │ quxAny<U extends any>() {}
^^^^^^^^^^^
3 │ }
4 │

All types are subtypes of any and unknown.

Safe fix: Remove the constraint.

2 │ ··quxAny<U·extends·any>()·{}
------------
const QuuxAny = <T extends any>() => {};
code-block.ts:1:20 lint/complexity/noUselessTypeConstraint  FIXABLE  ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

Constraining a type parameter to any or unknown is useless.

> 1 │ const QuuxAny = <T extends any>() => {};
^^^^^^^^^^^
2 │

All types are subtypes of any and unknown.

Safe fix: Remove the constraint.

1 │ const·QuuxAny·=·<T·extends·any>()·=>·{};
------------
function QuuzAny<T extends any>() {}
code-block.ts:1:20 lint/complexity/noUselessTypeConstraint  FIXABLE  ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

Constraining a type parameter to any or unknown is useless.

> 1 │ function QuuzAny<T extends any>() {}
^^^^^^^^^^^
2 │

All types are subtypes of any and unknown.

Safe fix: Remove the constraint.

1 │ function·QuuzAny<T·extends·any>()·{}
------------
interface FooUnknown<T extends unknown> {}
code-block.ts:1:24 lint/complexity/noUselessTypeConstraint  FIXABLE  ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

Constraining a type parameter to any or unknown is useless.

> 1 │ interface FooUnknown<T extends unknown> {}
^^^^^^^^^^^^^^^
2 │

All types are subtypes of any and unknown.

Safe fix: Remove the constraint.

1 │ interface·FooUnknown<T·extends·unknown>·{}
----------------
type BarUnknown<T extends unknown> = {};
code-block.ts:1:19 lint/complexity/noUselessTypeConstraint  FIXABLE  ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

Constraining a type parameter to any or unknown is useless.

> 1 │ type BarUnknown<T extends unknown> = {};
^^^^^^^^^^^^^^^
2 │

All types are subtypes of any and unknown.

Safe fix: Remove the constraint.

1 │ type·BarUnknown<T·extends·unknown>·=·{};
----------------
class BazUnknown<T extends unknown> {
}
```ts,expect_diagnostic
class BazUnknown {
quxUnknown<U extends unknown>() {}
}
code-block.ts:3:4 parse ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

unterminated template literal

1 │ class BazUnknown<T extends unknown> {
2 │ }
> 3 │ ```ts,expect_diagnostic
^^^^^^^^^^^^^^^^^^^^
> 4 │ class BazUnknown {
> 5 │ quxUnknown<U extends unknown>() {}
> 6 │ }
> 7 │


const QuuxUnknown = <T extends unknown>() => {};
code-block.ts:1:24 lint/complexity/noUselessTypeConstraint  FIXABLE  ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

Constraining a type parameter to any or unknown is useless.

> 1 │ const QuuxUnknown = <T extends unknown>() => {};
^^^^^^^^^^^^^^^
2 │

All types are subtypes of any and unknown.

Safe fix: Remove the constraint.

1 │ const·QuuxUnknown·=·<T·extends·unknown>()·=>·{};
----------------
function QuuzUnknown<T extends unknown>() {}
code-block.ts:1:24 lint/complexity/noUselessTypeConstraint  FIXABLE  ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

Constraining a type parameter to any or unknown is useless.

> 1 │ function QuuzUnknown<T extends unknown>() {}
^^^^^^^^^^^^^^^
2 │

All types are subtypes of any and unknown.

Safe fix: Remove the constraint.

1 │ function·QuuzUnknown<T·extends·unknown>()·{}
----------------

¥Valid

interface Foo<T> {}
type Bar<T> = {};

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