I have a workaround, but I'm not 100% sure I understand why the Shape properties are nonisolated so I'm not sure if this actually safe or not. struct SimpleShape: Shape { var width: Double nonisolated var animatableData: Double { get { MainActor.assumeIsolated { width } } set { MainActor.assumeIsolated { width = newValue } } } func path(in rect: CGRect) -> Path { return Path() } }

While I have not confirmed it as a solution yet, this post appears to cover the issue: https://developer.apple.com/forums/thread/662688

I ran into the same issue after wiping my machine. My two private packages became inaccessible within Xcode, but were otherwise perfectly reachable in other circumstances. I was able to find a workaround. I had to do two things to get it working. First, I changed from using an internal hostname to an IP address. It seems that whatever mismatch is happening is tied to the host name used. This might not be an easy change for you, depending on your configuration. But, it's at least a clue. With this change, I was re-prompted by Xcode for authentication information and was able to point it to my ssh key. However, that wasn't quite enough. I'd also begun using a new ssh key, with the ed25519 algorithm. This is recommended by GitHub, but apparently isn't supported by Xcode's internal git machinery. So, I created a new RSA key pair just for Xcode. With a supported key and a new hostname, I was able to successfully fetch my private packages. I also verified that this *only* occurs with Xcode 12. Xcode 11 seems to have no problems with my original project and hostnames.