This patch updates the `actor class` spelling to `actor` in almost all
of the tests. There are places where I verify that we sanely handle
`actor` as an attribute though. These include:
- test/decl/class/actor/basic.swift
- test/decl/protocol/special/Actor.swift
- test/SourceKit/CursorInfo/cursor_info_concurrency.swift
- test/attr/attr_objc_async.swift
- test/ModuleInterface/actor_protocol.swift
Currently, we don't have a fix-it to insert 'async', so I've marked those places
as not expecting a fix-it, until someone goes and implements that (rdar://72313654)
NSObject is guaranteed to have no state and no Swift vtable, and is
necessary for Swift classes to implement the NSObject protocol. Allow
it (and only it) as the superclass of an actor class, so that actor
classes can be exposed to Objective-C.
Actor-isolated operations must not be directly accessible from anywhere
that is not already guaranteed to be running within the actor context.
Prevent such operations from being `@objc`, because that would allow
Objective-C code to violate actor isolation.
Allow the declaration of @objc async methods, mapping them to a
completion-handler API in Objective-C. This covers most of the
checking and semantics within the type checker:
* Declaring @objc async methods and checking their parameter/result types
* Determining the default Objective-C selector by adding
completionHandler/WithCompletionHandler as appropriate
* Determining the type of the completion handler parameter
* Inferring @objc from protocol requirements
* Inferring @objc from an overridden method
