泛型，用于评估参数是否为“泛型类的实例”

Question

我想在函数中确定参数是否属于某个类。这是不可行的想法：

function assertClass<CLASS>(v: any, theClass: CLASS, message: string): v is typeof theClass{

    let is = v instanceof CLASS ;   // err 'CLASS' only refers to a type, but is being used as a value here
    return assert(is, message);
}

我想做什么：

let animal: Cat | Dog;
animal= somethingThatCanReturnCatOrDog();
assertClass<Cat>(animal, 'should be a Cat');

我用typeof尝试了几种组合，但是更加困惑了！