typescript 类型 'never' : how to use for object fields?

Question

我正在尝试获取 this example像this一样工作:

interface Foo {
    a: number;
    b: string;
    c: boolean;
}

type Explode<T> = keyof T extends infer K
    ? K extends unknown
    ? { [I in keyof T]: I extends K ? T[I] : never }
    : never
    : never;


type Test = Explode<Foo>;

const test: Test = {a: 1};

这给了我以下错误:

Type '{ a: number; }' is not assignable to type '{ a: number; b: never; c: never; } | { a: never; b: string; c: never; } | { a: never; b: never; c: boolean; }'.
  Type '{ a: number; }' is missing the following properties from type '{ a: number; b: never; c: never; }': b, c

如何实例化类型为 Test 的对象而不会出现错误？我想要一个可以包含字段 a 或 b 或 c 的类型(或者是一个空的 {}) .

Answer 1

我找到了解决方案。我需要像这样使 Foo 的字段可选:

已编辑以包含@apokryfos 的建议

interface Foo {
    a: number;
    b: string;
    c: boolean;
}

现在我可以:

interface Foo {
    a: number;
    b: string;
    c: boolean;
}

type AtMostOneOf<T> = keyof T extends infer K
    ? K extends unknown
    ? { [I in keyof T]+?: I extends K ? T[I] : never }
    : never
    : never;


type Test = AtMostOneOf<Foo>;

const test: Test = {a: 1}; // allowed
const test1: Test = {b: 'asd'}; // allowed
const test2: Test = {a: 1, b: 'asd'}; // not allowed
const test3: Test = {} // allowed

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