Strict Concurrency warning false positive: MainActor isolated KeyPath

[tcldr]

Description

When declaring a property wrapper on a MainActor isolated type that takes a MainActor isolated KeyPath, the 5.10 compiler flags a concurrency warning: 'Cannot form key path to main actor-isolated property 'requestReview'; this is an error in Swift 6'

Reproduction

import StoreKit

@MainActor
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

  var body: some View {
    Text("Cannot form key path to main actor-isolated property")
  }
}

Expected behavior

No warning.

Environment

swift-driver version: 1.90.11.1 Apple Swift version 5.10 (swiftlang-5.10.0.13 clang-1500.3.9.4)
Target: arm64-apple-macosx14.0

Additional information

First flagged here: https://forums.swift.org/t/swift-5-10-concurrency-and-xctest/69929/11

[wmorgue]

Xcode 16 still has this 🐞
swift-driver version: 1.109.2 Apple Swift version 6.0 (swiftlang-6.0.0.3.300 clang-1600.0.20.10)
Target: arm64-apple-macosx14.0

[NachoSoto]

Filed as #74636 too

[NachoSoto]

Filed 4 months ago and still unfixed in Swift 6. Meaning you can't use this environment variable while compiling with Swift 6.

[radude89]

Are there any workarounds available?

[hborla]

Sorry I missed this - if that happens again, please feel free to add the concurrency label yourself, after which it'll get added to my queue of concurrency issues to montior/triage/fix.

[hborla]

@xedin I think isolated key paths need to understand isolated default values. This code is valid because var requestReview, and thus its initial value, are isolated to the main actor.

[hborla]

Are there any workarounds available?

You should be able to work around this by initializing the property wrapper in a @MainActor-isolated initializer, like this

import SwiftUI
import StoreKit

@MainActor
struct MyView: View {
  @Environment private var requestReview: RequestReviewAction

  init() {
    self._requestReview = Environment(\.requestReview)
  }

  var body: some View { ... }
}

[NachoSoto]

@hborla I appreciate that, but as an external contributor I'm not allowed to add labels to issues I file unfortunately.

[hborla]

@hborla I appreciate that, but as an external contributor I'm not allowed to add labels to issues I file unfortunately.

That is annoying! I didn't realize that. It's fine to tag me and I can triage the issue directly. I'm also looking to put a process in place to fill the gaps in issue triage, as I know this isn't the first time an issue has been missed.