为什么打字稿不能正确推断条件的泛型类型？

Question

这是我的问题：

export type ForEachList<T> =
    T extends Element ? (NodeListOf<T> | HTMLCollectionOf<T>) :
    T extends CSSRule ? CSSRuleList :
    T extends Attr ? NamedNodeMap :
    T extends Node ? (Node[] | NodeList) :
    T[];

export function forEach<T>(array: ForEachList<T>,
                        forEachFn: (value: T, index: number, arr: ForEachList<T>, done: () => void) => boolean | void,
                        thisArg?: any): void { 
    for (let i = 0; i < array.length; i++) {
        const foo = array[i];
        forEachFn.call(thisArg, foo, i, array, () => { /* empty on purpose */ });
//                              ^^^ error here
    }
}

Argument of type 'Node | CSSRule | T' is not assignable to parameter of type 'T'.
  'T' could be instantiated with an arbitrary type which could be unrelated to 'Node | CSSRule | T'.
    Type 'Node' is not assignable to type 'T'.
      'T' could be instantiated with an arbitrary type which could be unrelated to 'Node'.(2345

游乐场链接

打字稿显示它foo的类型为T | CSSRule | Node。但是，forForEachList的类型只允许单个类型的列表，而不是联合。如果我删除 CSSRule、Attr 和 Node 的条件，它就可以正常工作。为什么这里foo不是类型T？