[Accepted with modifications] SE-0414: Region-based isolation

The second review of SE-0414: Region-based isolation ran from January 30th through February 6th. The Language Steering Group has decided that the proposal is accepted with modifications.

The second review was fairly light, and was mainly comprised of questions about the base proposal. One reviewer surfaced an additional data-race safety hole with assumeIsolated not covered by the revision that allows passing a non-Sendable value isolated to the actor over an isolation boundary. This hole can be closed by requiring that the type parameter of assumeIsolated, which is used as the closure result type and the overall function result type, conform to Sendable. Because this change had sufficient discussion in the review thread, the Language Steering Group is comfortable accepting that modification without further review.

Thank you to everyone who participated in the pitch and proposal reviews; your contributions help make Swift a better language.

Holly Borla
Review Manager