如何将属性和模板文字变量限制为相同的值？

Question

展示我想要的东西要比给这篇文章打个标题容易得多：

type Foo = "bar" | "baz";

interface Consistency {
    foo: Foo;
    fooTemplate: `${Foo} in a template`;
}

// I want this to compile (and it does)
const valid1: Consistency = {
    foo: "bar",
    fooTemplate: "bar in a template",
}

const valid2: Consistency = {
    foo: "baz",
    fooTemplate: "baz in a template",
}

// I DON'T want this to compile (and it does)
const invalid1: Consistency = {
    foo: "bar",
    fooTemplate: "baz in a template",
}

const invalid2: Consistency = {
    foo: "baz",
    fooTemplate: "bar in a template",
}

我尝试将Consistency更改为You can play with this example here.

interface Consistency {
    foo: Foo;
    fooTemplate: `${foo} in a template`; //lowercase foo
}

但这并不能编译。在无效的情况下有可能出现编译器错误吗？

Answer 1

您可以使用映射类型并直接将其解包，以获得所有有效子类型的联合类型：

type Consistency  = {
    [K in Foo]: {
        foo: K;
        fooTemplate: `${K} in a template`;
    }
}[Foo]