[feature] Get the type from a variable

Feature
A similar feature in typescript

const foo: number = 1
type Foo = typeof foo  // type Foo = number

function bar(x: string): void {

}

type Bar = typeof bar // type Bar = (x: string) => void

Pitch
The expected way in future python.
Possible implementation: implement __class_getitem__ for type :

foo: int = 1
Foo = type[foo]  # equivalent to Foo = int

def bar(x: string) -> None :
    ...
Bar = type[bar]  # equivalent to Bar = Callable[[str], None]

没有指定任何仓库文件或测试，因此请先查看 TypeScript 的 typeof-types 参考资料以及此 issue 中的讨论。明确在提议的 type[...] 语法下变量和函数的预期行为；当类型语义和兼容性要求达成了足以进行实现和测试的共识时，即可视为完成。