Swift: heterogenous generic items in an array

gistfile1.txt

struct Box<T> {
	let value: T
}

// This works:
let boxes1 = [Box(value: 42), Box(value: "hi")]

// This works:
let boxes2 = [Box(value: 42), Box(value: "hi")] as [Box<Any>]

// This doesn't work: "'Int' is not identical to 'String'"
let boxes3 = [Box<Int>(value: 42), Box<String>(value: "hi")]

// This doesn't work: "'String' is not identical to 'Any'"
let boxes4 = [Box<Int>(value: 42), Box<String>(value: "hi")] as [Box<Any>]