Open Radar

 
Summary:
Swift runtime crashes when casting optional type to non-optional type.

Error:
fatal error: can't reinterpretCast values of different sizes

Code:

import UIKit
import XCTest

class User {
    var dict: [String:String]?
}

class SwiftReinterpretCastCrashTests: XCTestCase {
    
    override func setUp() {
        super.setUp()
        // Put setup code here. This method is called before the invocation of each test method in the class.
    }
    
    override func tearDown() {
        // Put teardown code here. This method is called after the invocation of each test method in the class.
        super.tearDown()
    }
    
    func testCrash() {
        var user = User()
        user.dict = ["email":"john.doe@somewhere.com"]
        // Next line crashes with: fatal error: can't reinterpretCast values of different sizes
        let a = user.dict as [String: String]
    }
    
}

Steps to Reproduce:
Build and run tests.

Expected Results:
Swift runtime should downcast optional  [String: String]? to [String: String]

Actual Results:
Fatal error received causing crash:

fatal error: can't reinterpretCast values of different sizes

Version:
Yosemite Developer Preview 3, Xcode 6 beta 3