swift 新建泛型数组的问题

[arbipher]

问题来自官方网站的 例子

页面上方提供 Playground 的下载。我的问题是页面上的一个练习，在页面最下方

Modify the anyCommonElements(_:_:) function to make a function that returns an array of the elements that any two sequences have in common.

我尝试新建泛型数组的方法是

var result  = [T.Generator.Element]()

会报编译错误： invalid use of '()' to call a value of non-function type '[T.Generator.Element.Type]'

stackoverflow 上搜到了这个问题的 解答。我写在下面代码的注释里。

func commonElements <T: SequenceType, U: SequenceType where T.Generator.Element: Equatable, T.Generator.Element == U.Generator.Element> (lhs: T, _ rhs: U) -> Bool {

//  以下三行，前两行是 stackoverflow 提供的方法，单独都 work 。第三行是我的方法，会报错。
//  var result = Array<T.Generator.Element>()
//  var result: [T.Generator.Element] = []
    var result  = [T.Generator.Element]()

    for lhsItem in lhs {
        for rhsItem in rhs {
            if lhsItem == rhsItem {
                result.append(lhsItem)
            }
        }
    }
    return false
}

commonElements([1, 2, 3], [2, 3])  // result is [2, 3]

在另一份官方页面里提到

Array Type Shorthand Syntax

The type of a Swift array is written in full as Array<Element>, where Element is the type of values the array is allowed to store. You can also write the type of an array in shorthand form as [Element]. Although the two forms are functionally identical, the shorthand form is preferred and is used throughout this guide when referring to the type of an array.

这里提到 Array<Element>和[Element]是等价的。那么 Array<T.Generator.Element>和[T.Generator.Element]也应该是等价的。

为什么我的语句会报错呢？不知道问题出在哪里。