What's with empty arrays and generics in Swift?

Question

Ran across an interesting bug earlier today when working with generics in Swift. I figured out a solution, but I'm wondering if anyone can answer why the compiler does not catch something like this. Let me start with a block of code.

func doSomething<T>(with array: [T]) {
    type(of: array)     // Optional<Array<Int>>
    array is [Int]      // true 🙌
    array is [String]   // true 🤔
}

var arrayOfInts: [Int] = []
doSomething(with: arrayOfInts)

See line 4. Why the heck is that true? Am I missing something? Shouldn't the compiler be smart enough to figure out this isn't an array of Strings? This ultimately led to a bug where a value was set incorrectly due to the empty array assumed to be of the wrong type.

As far as a solution, I went with something along the lines of:

if type(of: array).Element.self == Model.self

Answer 1

Actually it has nothing to do with the generic. Any empty array answers the is question with true if the type is an array:

[Int]() is [String] // true
[1] is [String] // false

It does seem odd; file a bug.