SE-0423 (second review): Dynamic actor isolation enforcement from non-strict-concurrency contexts

Hi Swift community,

The second review of SE-0423: Dynamic actor isolation enforcement from non-strict-concurrency contexts begins now and runs through 19th April, 2023.

The original proposal has been amended by the proposal author in response to feedback during the first review. The changes from the first review are:

  • Insertion of dynamic checks at direct calls to synchronous actor-isolated functions imported from Swift 6 libraries.
  • Addition of a flag to disable all dynamic actor isolation checking.

A diff of the proposal can be found here.

Reviews are an important part of the Swift evolution process. All review feedback should be either on this forum thread or, if you would like to keep your feedback private, directly to the review manager. When emailing the review manager directly, please keep the proposal link at the top of the message.

What goes into a review?

The goal of the review process is to improve the proposal under review through constructive criticism and, eventually, determine the direction of Swift. When writing your review, here are some questions you might want to answer in your review:

  • What is your evaluation of the proposal?
  • Is the problem being addressed significant enough to warrant a change to Swift?
  • Does this proposal fit well with the feel and direction of Swift?
  • If you have used other languages or libraries with a similar feature, how do you feel that this proposal compares to those?
  • How much effort did you put into your review? A glance, a quick reading, or an in-depth study?

More information about the Swift evolution process is available at

Thank you,

Ben Cohen
Review Manager


Review Conclusion

The proposal has been accepted.

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