We need to check the feature availability of _unavailableFromAsync
before it gets picked up in the swift interface file. This updates the
compiler to provide the necessary wrappings for that check.
and make `@_unsafeInheritExecutor` a suppressible feature.
Some language features are required in order to parse a
declaration correctly, but some can safely be ignored.
For the latter, we'd like the module interface to simply
contain the declaration twice, once with the feature and
once without. Some basic support for that was already
added for the SpecializeAttributeWithAvailability feature,
but it didn't interact correctly with required features
that might be checked in the same `#if` clause (it simply
introduced an `#else`), and it wasn't really set up to
allow multiple features to be handled this way. There
were also a few other places that weren't updated to
handle this, presumably because they never coincided
with a `@_specialize` attribute.
Introduce the concept of a suppressible feature, which
is anything that the ASTPrinter can modify the current
PrintOptions in order to suppress. Restructure the
printing of compatibility checks so that we can print
the body multiple times with different settings.
Print required feature checks in an outer `#if...#endif`,
then perform a separate `#if...#else...#endif` within
if we have suppressible features. If there are multiple
suppressible features, check for the most recent first,
on the assumption that it will imply the rest; then
perform subsequent checks with an `#elsif` clause.
This should be a far more solid foundation on which to
build compatibility checks in the future.
`@_unsafeInheritExecutor` needs to be suppressible
because it's been added to some rather important
existing APIs. Simply suppressing the entire decl will
effectively block old tools from using a new SDK to
build many existing projects (if they've adopted
`async`). Dropping the attribute changes the semantics
of these functions, but only if the compiler features
the SE-0338 scheduling change; this is a very narrow
window of main-branch development builds of the tools,
none of which were officially released.
The patch introduces a new setting instead of changing existing settings
because the generated interfaces in the IDE have slightly different
requirements; the extended type there is unconditionally not printed
qualified (even if it is ambiguous). This is likely because the
ambiguity heuristic is very weak; it doesn't even do name lookup.
Simplifying that logic would be nice, but then we'd need to update
a bunch of IDE/print* tests and end up with more more visual clutter
in the IDE.
Introducing the new setting means we can change the behavior for
swiftinterface files without affecting the behavior for IDE interfaces.
Fixes rdar://79093752.
- Introduce an UnownedSerialExecutor type into the concurrency library.
- Create a SerialExecutor protocol which allows an executor type to
change how it executes jobs.
- Add an unownedExecutor requirement to the Actor protocol.
- Change the ABI for ExecutorRef so that it stores a SerialExecutor
witness table pointer in the implementation field. This effectively
makes ExecutorRef an `unowned(unsafe) SerialExecutor`, except that
default actors are represented without a witness table pointer (just
a bit-pattern).
- Synthesize the unownedExecutor method for default actors (i.e. actors
that don't provide an unownedExecutor property).
- Make synthesized unownedExecutor properties `final`, and give them
a semantics attribute specifying that they're for default actors.
- Split `Builtin.buildSerialExecutorRef` into a few more precise
builtins. We're not using the main-actor one yet, though.
Pitch thread:
https://forums.swift.org/t/support-custom-executors-in-swift-concurrency/44425
Add a feature for this new attribute, and make sure we use the feature
guard for functions that use it, e.g., the new `async`.
Finishes rdar://76927008.
Extend the checks for marker protocols and rethrows protocols to ensure
that we #if out more code that relies on them in module interface
generation. This makes the _Concurrency module parseable by much older
compilers.
Fixes rdar://75291705.
Thanks to a great idea from Slava, simplify the printing of marker
protocols in Swift interfaces while maintaining backward compatibility.
For compilers that cannot handle marker protocols, print a typealias
to `Any` instead, which is a good stand-in for just about everything.
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.
