Narrow the proposal down to only support re-entrant actors.
Narrow the proposal down to only support re-entrant actors.

Capture several potential non-reentrant designs in the Alternatives Considered as possible future extensions.

apple/swift-evolution,apple/swift-evolution,natecook1000/swift-evolution,natecook1000/swift-evolution,abertelrud/swift-evolution,abertelrud/swift-evolution