如何在TypeScript中将元组与泛型一起使用

我正在try 编写一个类型安全的映射对象.我只想定义一次键/值对.

我在以下方面取得了成功:

const myPropTuple = [
    [0, "cat"],
    [1, "dog"],
    [2, "bird"]
] as const;

type TMyPropKey = TInnerTupple<typeof myPropTuple>[0];
type TMyPropValue = TInnerTupple<typeof myPropTuple>[1];

function getMyProp(val: number) {
    type TKey = TInnerTupple<typeof myPropTuple>[0];

    const mapA2 = new Map(myPropTuple);
    if(!mapA2.has(val as TKey)) throw new RangeError("unexpected value");
    return mapA2.get(val as TKey);
}

// helper library (not to be inlined)
type TTupleType<T extends Iterable<any>> = T extends ReadonlyArray<infer R> ? R :never;
type TInnerTupple<I extends Iterable<any>> = TTupleType<I>;

// Tests
console.assert(getMyProp(1) === "dog");
//console.assert(getMyProp(1) === "turle");    // throws compiler error

const a: TMyPropValue = "cat";
//const b: TMyPropValue = "eagle";    // throws compiler error

但我希望使该函数成为泛型，并仍然维护类型安全:

我们的目标是能够写作

const myPropTuple = [
    [0, "cat"],
    [1, "dog"],
    [2, "bird"]
] as const;

console.assert(getGenericProp(myPropTuple, 1) === "dog");

const yourPropTuple = [
    [0, "fish"],
    [1, "towel"],
    [2, "whale"]
] as const;

console.assert(getGenericProp(yourPropTuple, 0) === "fish");

并使以下代码无法编译

console.assert(getGenericProp(myPropTuple, 1) === "turle");    // throws compiler error

type TYourPropValue = TInnerTupple<typeof yourPropTuple>[1];
const y: TYourPropValue = "dog";    // throws compiler error

addendum个

@jcalz建议了另一个解决方案，它的基本优点是简单，所以我在这里重复一下，稍微扩展一下:

const animalProps = {
    0: "cat",
    1: "dog",
    2: "bird"
  } as const;

function getGenericProp2<T extends object>(props: T, val: keyof T): T[keyof T] {
    const found = props[val];
    if(found === undefined) throw new RangeError("unexpected value");
    return found;
}
type TValues = ValueOf<typeof animalProps>;
type TKeys = keyof typeof animalProps;