Extend the actor isolation checking rules to account for global
actors. For example, a function annotated with a given global actor
can invoke synchronous methods from the same global actor, but not
from a different global actor or a particular actor instance.
Similarly, a method of an (instance) actor that is annotated with a
global actor attribute is not part of the (instance) actor and,
therefore, cannot operate on its actor-isolated state.
Global actor types can be used as attributes on various kinds of
declarations to indicate that those declarations are part of the
isolated state of that global actor. Allow such annotation and perform
basic correctness checks.
The globalActor attribute indicates that a particular type describes a
global actor. Global actors allow the notion of actor state isolation
to be spread across various declarations throughout a program, rather
than being centered around a single actor class. There are useful
primarily for existing notions such as "main thread" or subsystems
accessed through global/singleton state.
Actor classes never have non-actor superclasses, so we can ensure that
all actor classes have a common vtable prefix for the
`enqueue(partialTask:)` operation. This allows us to treat all actor
classes uniformly, without having to go through the Actor witness
table every time.
Introduce a new Actor protocol, which is a class-bound protocol with only
one requirement:
func enqueue(partialTask: PartialAsyncTask)
All actor classes implicitly conform to this protocol, and will synthesize
a (currently empty) definition of `enqueue(partialTask:)` unless a suitable
one is provided explicitly.
This method had a messy contract:
- Setting the diags parameter to nullptr inhibited caching
- The initExpr out parameter could only used if no result
had yet been cached
Let's instead use the request evaluator here.
Infer @asyncHandler on a protocol methods that follow the delegate
convention of reporting that something happened via a "did" method, so
long as they also meet the constraints for an @asyncHandler method in
Swift. This enables inference of @asyncHandler for witnesses of these
methods.
We'll need this to get the right 'selfDC' when name lookup
finds a 'self' declaration in a capture list, eg
class C {
func bar() {}
func foo() {
_ = { [self] in bar() }
}
}
To avoid ambiguity, ImportResolution and a few other things used the term “decl path” instead of “access path”. Switch back to the correct terminology now that the compiler is becoming more consistent about it.
Allow an 'async' function to overload a non-'async' one, e.g.,
func performOperation(_: String) throws -> String { ... }
func performOperation(_: String) async throws -> String { ... }
Extend the scoring system in the type checker to penalize cases where
code in an asynchronous context (e.g., an `async` function or closure)
references an asychronous declaration or vice-versa, so that
asynchronous code prefers the 'async' functions and synchronous code
prefers the non-'async' functions. This allows the above overloading
to be a legitimate approach to introducing asynchronous functionality
to existing (blocking) APIs and letting code migrate over.
Refactor TypeCheckFunctionBodyRequest to return
the type-checked body, and remove
`typeCheckAbstractFunctionBody` in favor of
a method on AbstractFunctionDecl. In addition,
start returning an ErrorExpr body instead of
a partially type-checked body if type-checking
fails.
Generalize `ClassDecl::getEmittedMembers()` to operate on an
`IterableDeclContext`, so that it can be for other nominal types,
extensions, etc. Rename to `getSemanticMembers()` to indicate that
these are all of the members that are semantically part of that
context.
Clean up the implementation slightly so it only forces type checking
for the conformances within that particular context (using
`getLocalConformances()`) and doesn't need to list out each of the
protocols it cares about.
When a given Objective-C method has a completion handler parameter
with an appropriate signature, import that Objective-C method as
async. For example, consider the following CloudKit API:
- (void)fetchShareParticipantWithUserRecordID:(CKRecordID
*)userRecordID
completionHandler:(void (^)(CKShareParticipant * _Nullable shareParticipant, NSError * _Nullable error))completionHandler;
With the experimental concurrency model, this would import as:
func fetchShareParticipant(withUserRecordID userRecordID: CKRecord.ID) async throws -> CKShare.Participant?
The compiler will be responsible for turning the caller's continuation
into a block to pass along to the completion handler. When the error
parameter of the completion handler is non-null, the async call
will result in that error being thrown. Otherwise, the other arguments
passed to that completion handler will be returned as the result of
the async call.
async versions of methods are imported alongside their
completion-handler versions, to maintain source compatibility with
existing code that provides a completion handler.
Note that this only covers the Clang importer portion of this task.
