Swift 5.10 Concurrency and XCTest

[hborla (Holly Borla)]

@tcldr

Do you know if we should we be filing Feedbacks for APIs which aren't playing nicely with Swift Concurrency at this stage?

Not all of your examples are SDK issues, but yes, you should absolutely file feedback reports if you believe an API is mis-annotated.

@tcldr

/* @MainActor */ // occurs with or without annotation 
struct MyView: View {
  // Cannot form key path to main actor-isolated property 'requestReview'; this is an error in Swift 6
  @Environment(\.requestReview) private var requestReview

I think using a main-actor isolated key-path in a property wrapper initializer should be fine as long as your enclosing view is @MainActor, per SE-0411: Isolated default values. That makes this just a compiler bug.

@tcldr

/* @preconcurrency doesn't help */ import os

It's a compiler bug that the @preconcurrency import doesn't suppress the warning.

@tcldr

Or Foundation:

import Foundation

public final class UnitWarning: Dimension {
  
  public override class func baseUnit() -> UnitWarning { .warnings }
  
  // Static property 'warnings' is not concurrency-safe because it is not either conforming to 'Sendable' or isolated to a global actor; this is an error in Swift 6
  public static let warnings = UnitWarning(
    symbol: "WARN",
    converter: UnitConverterLinear(coefficient: 1)
  )
}

Dimension is has an explicit, unavailable Sendable conformance, which means it's definitely not a thread-safe type, so this is not an issue for Foundation to fix. If you want to use a non-Sendable type as a global/static variable in your code, you will need to isolated it to a global actor for safety to be proven statically, or wrap it in some kind of Sendable container type that protects access to it. If you don't want static data-race safety, you can mark it as nonisolated(unsafe) and take care at each use site to make sure you are synchronizing access to it, e.g. by using a lock or a dispatch queue.