- stop storing the parent task in the TaskGroup at the .swift level
- make sure that swift_taskGroup_isCancelled is implied by the parent
task being cancelled
- make the TaskGroup structs frozen
- make the withTaskGroup functions inlinable
- remove swift_taskGroup_create
- teach IRGen to allocate memory for the task group
- don't deallocate the task group in swift_taskGroup_destroy
To achieve the allocation change, introduce paired create/destroy builtins.
Furthermore, remove the _swiftRetain and _swiftRelease functions and
several calls to them. Replace them with uses of the appropriate builtins.
I should probably change the builtins to return retained, since they're
working with a managed type, but I'll do that in a separate commit.
When generating a module interface, emit `#if` around any declarations
that are tied to specific, named language features. This allows module
interfaces to be processed by older Swift compilers that do not
support these newer features, such as async/await or actors.
The amount of effort required to correctly handle a new kind of
feature varies somewhat drastically based on the feature itself. The
"simple" case is where a particular declaration can only exist if a
feature is available. For example, and `async` declaration is fairly
easy to handle; a `@_marker` protocol's conformances are not.
Fixes rdar://73326633.
Introduce some basic support for defining specific language features
that can be checked by name, e.g.,
#if $AsyncAwait
// use the feature
#endif
For backward compatibility with older compilers, to actually prevent
the parser from parsing, one will have to do a Swift compiler version
check, even though the version number doesn't matter. For example:
#if compiler(>=5.3) && $AsyncAwait
// use the feature
#endif
