Not quite NFC because apparently the representation bleeds into what's
accepted in some situations where we're supposed to be warning about
conflicts and then making an arbitrary choice. But what we're doing
is nonsense, so we definitely need to break behavior here.
This is setting up for isolated(any) and isolated(caller). I tried
to keep that out of the patch as much as possible, though.
When an actual instance of a distributed actor is on the local node, it is
has the capabilities of `Actor`. This isn't expressible directly in the type
system, because not all `DistributedActor`s are `Actor`s, nor is the
opposite true.
Instead, provide an API `DistributedActor.asLocalActor` that can only
be executed when the distributed actor is known to be local (because
this API is not itself `distributed`), and produces an existential
`any Actor` referencing that actor. The resulting existential value
carries with it a special witness table that adapts any type
conforming to the DistributedActor protocol into a type that conforms
to the Actor protocol. It is "as if" one had written something like this:
extension DistributedActor: Actor { }
which, of course, is not permitted in the language. Nonetheless, we
lovingly craft such a witness table:
* The "type" being extended is represented as an extension context,
rather than as a type context. This hasn't been done before, all Swift
runtimes support it uniformly.
* A special witness is provided in the Distributed library to implement
the `Actor.unownedExecutor` operation. This witness back-deploys to the
Swift version were distributed actors were introduced (5.7). On Swift
5.9 runtimes (and newer), it will use
`DistributedActor.unownedExecutor` to support custom executors.
* The conformance of `Self: DistributedActor` is represented as a
conditional requirement, which gets satisfied by the witness table
that makes the type a `DistributedActor`. This makes the special
witness work.
* The witness table is *not* visible via any of the normal runtime
lookup tables, because doing so would allow any
`DistributedActor`-conforming type to conform to `Actor`, which would
break the safety model.
* The witness table is emitted on demand in any client that needs it.
In back-deployment configurations, there may be several witness tables
for the same concrete distributed actor conforming to `Actor`.
However, this duplication can only be observed under fairly extreme
circumstances (where one is opening the returned existential and
instantiating generic types with the distributed actor type as an
`Actor`, then performing dynamic type equivalence checks), and will
not be present with a new Swift runtime.
All of these tricks together mean that we need no runtime changes, and
`asLocalActor` back-deploys as far as distributed actors, allowing it's
use in `#isolation` and the async for...in loop.
`@GlobalActor(unsafe)` and `@preconcurrency @GlobalActor` mean the same
thing, but there were two different representations in the actor isolation
checker. Standardize on the preconcurrency representation.
Most clients only want to set one of the two
parameters, split it into `setPattern` and
`setInitContext` (the latter of which now
handles calling `setBinding`).
Switch from promising a DeclContext to a
PatternBindingInitializer.
This has a couple of benefits:
- It eliminates a few places where we were force
`cast`'ing to PatternBindingInitializer.
- It improves the clarity of what's being stored,
it's not whatever the parent context of the
initializer is, it's specifically the
PatternBindingInitializer context if it exists.
Introduce a new expression macro that produces an value of type
`(any AnyActor)?` that describes the current actor isolation. This
isolation will be `nil` in non-isolated code, and refer to either the
actor instance of shared global actor in other cases.
This is currently behind the experimental feature flag
OptionalIsolatedParameters.
Obsolete the `-enable-swift3-objc-inference` option and related options by
removing support for inferring `@objc` attributes using Swift 3 rules.
Automated migration from Swift 3 has not been supported by the compiler for
many years.
I am doing this in preparation for adding options to SILParameterInfo/
SILResultInfo that state that a parameter/result is transferring. Even though I
could have just introduced a new bit here, I instead streamlined the interface
of SILParameterInfo/SILResultInfo to use an OptionSet instead of individual bits
to make it easier to add new flags here. The reason why it is easier is that
along API (e.x.: function argument) boundaries one does not have to marshal each
field or pass each field. Instead one can just pass the whole OptionSet as an
opaque thing. Using this I was able to change serialization/deserialization of
SILParameterInfo/SILResultInfo so that one does not need to update them if one
adds new fields!
The reason why I am doing this for both SILParameterInfo/SILResultInfo in the
same commit is because they share code in the demangler that I did not want to
have to duplicate in an intervening commit. By changing them both at the same
type, I didn't have to change anything without an actual need to.
I am doing this in a separate commit from adding transferring support so I can
validate correctness using the tests for the options already supported
(currently only differentiability).
rdar://119329771
This layout allows adding pre-specializations for trivial types that have a different size, but the same stride. This is especially useful for collections, where the stride is the important factor.
The spelling kind was only ever set to
`StaticSpellingKind::None`, and the static location
was never used for anything (and should be queried
on the storage anyway). This doesn't affect the
computation of `isStatic` since `IsStaticRequest`
already takes the static-ness from the storage for
accessors.
A client shouldn't know about the underlying type of an opaque type
unless it can see the body of the naming decl. Attempting to read it can
lead to accessing a hidden dependency and a compiler crash.
This was protected by a check specific to function decls but var decls
and subscripts were not handled. To support them we have to move this
logic to the writer side where we have access to the full
AbstractStorageDecl and write in the swifmodule whether the underlying
type should be visible outside of the module.
rdar://117607906
The Attr.h is shared with SwiftCompilerSources through C++ interop and
C++ interop somehow crashes with libc++'s std::optional. So use legacy
llvm::Optional for now.
Serialization depended on a longstanding bug in NeedsNewVTableEntryRequest: For a member of a non-class, it always returned `true`, not `false`. It turns out this was because serialization was conflating the concepts of vtable entries and witness table entries, so it needed NeedsNewVTableEntryRequest to return true for members of protocols. Untangle this logic so that NeedsNewVTableEntryRequest can be given the logical behavior.
