Typescript 类似断言的类型保护

这是否可以在没有限制的情况下限制类型if通过函数调用never返回例如undefined like assert在打字稿中？

示例代码：

interface Foo { bar(): void }
function getFoo(): Foo | undefined { }

function test() {
    const foo = someService.getFoo();
    assert(foo);
    if (!foo) { // now mandatory because without this foo may be still undefined even if assert protects us from this
        return;
    }
    foo.bar(); // , here foo may be undefined
}

我希望能够写assert这样我就可以跳过以下内容if (!foo)条款并有foo类型仅限于普通Foo.

这在打字稿中可能吗？

我尝试过添加重载never对于抛出的类型：

function assertGuard(v: undefined | null | '' | 0 | false): never;
function assertGuard(v: any): void; // i'm not sure which one is  captured by TS typesystem here

function assertGuard<T>(v: T | undefined) {
    if (v === undefined || v === null || v === '' || v === 0 || v === false) {
         throw new AssertionError({message: 'foo'})
    }
}

这个可以编译，但是调用assertGuard(foo)不认识到这一点undefined它会返回never所以不限制foo to Foo.

我找到了可能的解决方法，但我认为经典assert更清洁的方法：

function assertResultDefined<T>(v: T|undefined): T | never {
    if (v === undefined) {
        throw new Error('foo');
    }
    return v;
}
function die(): never { throw new Error('value expected)}

const foo = assertResultDefined(getFoo()) // foo is Foo, undefined is erased
const foo = getFoo() || die();
    // undefined is erased from foo
    / CONS: doesn't play well with types that interpolate to `false` like 0, ''

Typescript 3.7 添加了控制流分析中的断言 https://github.com/microsoft/TypeScript/pull/32695.

An asserts返回类型谓词指示函数仅在断言成立时返回，否则抛出异常

不再需要消费者方面的黑客攻击。

interface Foo { bar(): void }
declare function getFoo(): Foo | undefined;

function assert(value: unknown): asserts value {
    if (value === undefined) {
        throw new Error('value must be defined');
    }
}

function test() {
    const foo = getFoo();
    // foo is Foo | undefined here
    assert(foo);
    // foo narrowed to Foo
    foo.bar();
}

另外，可以断言提供的参数是必需的类型：

declare function assertIsArrayOfStrings(obj: unknown): asserts obj is string[];

function foo(x: unknown) {
    assertIsArrayOfStrings(x);
    return x[0].length;  // x has type string[] here
}

操场 https://www.typescriptlang.org/play/index.html#code/CYUwxgNghgTiAEAzArgOzAFwJYHtXygGdCQYMBJQgQRhigE8B5RAZQxi1QHNCAKHAEYArAFzw0Aa1Q4A7qgCUYoiTKF4gofCxrC7TlwDaAXQDcAKDMp02PEhw5eADzGTpc+fADeZ+L4LFSCmpaBmY2Dm4+R3lzP3g4DGQYfEcDAAYjADoIEG4MAAsTXwB6YvhHeHyieAx6AAcEXQjDI0rSEDMAXyA