Update Pick to use new key remapping in mapped types

Search Terms

pick omit key remapping

Suggestion

Update Pick in lib.d.ts to be:

type Pick<T, K extends keyof T> = {
    [P in keyof T as Extract<P, K>]: T[P];
};

It is currently defined as:

type Pick<T, K extends keyof T> = {
    [P in K]: T[P];
};

Use Cases

With this new definition, typescript can statically analyze the keys, which allows interfaces to extends these types.

Examples

interface Base {
    a: number,
    b: string,
    c: boolean,
}

// Errors: "An interface can only extend an object type or intersection of object types with statically known members"
interface PickBase0<K extends keyof Base> extends Pick<Base, K> {
    pickedKeys: K
}

type Pick1<T, K extends keyof T> = { [L in keyof T as Extract<L, K>]: T[L] }

// Works
interface PickBase1<K extends keyof Base> extends Pick1<Base, K> {
    pickedKeys: K
}

Playground Link

Checklist

My suggestion meets these guidelines:

• This wouldn't be a breaking change in existing TypeScript/JavaScript code
• This wouldn't change the runtime behavior of existing JavaScript code
• This could be implemented without emitting different JS based on the types of the expressions
• This isn't a runtime feature (e.g. library functionality, non-ECMAScript syntax with JavaScript output, etc.)
• This feature would agree with the rest of TypeScript's Design Goals.

首先检查 lib.d.ts 中当前的 Pick 定义，并复现涉及 mapped types 和 interface extension 的链接 Playground 示例。将建议的 key-remapping 定义与现有行为进行比较；当示例能够正常工作且不破坏现有的 Pick 行为，并且相关的 TypeScript 检查通过时，即表示完成。