swift

4ffe06ed - [SE-0466] Extensions and members thereof can apply default isolation

[SE-0466] Extensions and members thereof can apply default isolation Extensions of nonisolated types can get default isolation from context (e.g., @MainActor) independently. This was previously true for members, but not conformances, and recently regressed for members. Fix the logic to consistently allow such extensions to be default main-actor isolated, which affects both their members and conformances. Fixes rdar://156644976.