Open Radar

 
Summary:
Working with Swift, I defined the following method on a class:

    func drawRandomCard() -> Card? {
        var randomCard: Card? = nil

        if cards.count > 0 {
            let index = Int(arc4random()) % cards.count
            let randomCard = cards[index]
            cards.removeAtIndex(index)
        }
        return randomCard
    }

This code has a bug: inside the "if" statement, I use "let" to define a new variable named "randomCard", which shadows the previous declaration above; as a result, it always returns nil. 

Much better and more helpful would be if the compiler warned me about assigning a variable and then not using it inside the "if" block

Steps to Reproduce:
Compile the code above

Expected Results:
Xcode/llvm to warn about assigning an unused variable

Actual Results:
Code compiles with no warnings

Version:
Xcode Version 6.0 (6A215l)