Bizarre. Thanks, Stephen.

@swift-ci create

Thanks for the simple and short test case. Worked (crashed) on the first try here.

Comment by Leandro Barbosa (JIRA)

Just to add that I found this post while searching for my own weird issue and it wasn't related to type(of). Any kind of access to the type will cause it. This is a simplified version of what I was trying to do:

import Foundation

protocol Proto {
}

typealias CodableProtoObject = NSObject & Codable & Proto

class Foo: CodableProtoObject {
}

class Bar: CodableProtoObject { 
}

var codableTypes: [CodableProtoObject.Type] = []
print("we're fine until here...")
codableTypes = [Foo.self, Bar.self]
print("we'll never get here")

I tried not using the alias and using the types directly but got the same outcome.

Removing Codable or Proto from the typealias is enough to avoid the error.

Environment: MacOS 10.13.6 (17G65), XCode 9.4.1 (9F2000)

Comment by Leandro Barbosa (JIRA)

The issue disappears if I restrict the protocol to the classes/protocol in question which is a valid workaround for my use case.

This example works:

import Foundation

protocol Proto: NSObject & Codable {
}

typealias CodableProtoObject = NSObject & Codable & Proto

class Foo: CodableProtoObject {
    
}
class Bar: CodableProtoObject {
    
}
var codableTypes: [CodableProtoObject.Type] = []
print("this is ok...")
codableTypes = [Foo.self, Bar.self]
print("this is fine too!")

Pull request for the fix: #21119 Turned out to be a really simple incorrect cast. Just a bit hard to track down due to cause and effect being fairly far removed from each other.

Comment by Stephen (JIRA)

I can confirm that in Xcode Version 10.2 (10E125) and Swift version 5.0 (swiftlang-1001.0.69.3 clang-1001.0.47) that the bug has been fixed and the code now performs correctly.

Comment by Stephen (JIRA)

Issue resolved in Swift version 5.0 (swiftlang-1001.0.69.3 clang-1001.0.47)

Great, thanks for confirming!

Comment by Stephen (JIRA)

No problem 🙂

Closing the issue since the fix has been confirmed.