I have a function that takes as parameters a method name as a string and the object that contains that method. I can easily check that the class of the object contains the method name. But I also want to make sure that it is callable and the return type is of a certain type. How can I do that?

type expected = {
    a: string;
}

function handle<T>(method: keyof T, handler : T ) {
    const f = handler[method];
    return f(); // this does not compile
}


class Handler {
    foo() {
        return 'bar';
    }
    baz() {
        return { a : 'bar'}
    }
}

handle('foo', new Handler()); // compile error - not the expected return type
handle('baz', new Handler()); // should compile