Isolation checking for calls had two separate implementation places:
one that looked at the declaration being called (for member
declarations) and one that worked on the actual call expression. Unify
on the latter implementation, which is more general and has access to
the specific call arguments. Improve diagnostics here somewher so we
don't regress in that area.
This refactoring shouldn't change the actual semantics, but it makes
upcoming semantic changes easier.
Reimplement the final client of ActorIsolationRestriction, conformance
isolation checking, to base it on the new "actor reference" logic.
Centralize the diagnostics emission so we have a single place where we
emit the primary diagnostic (which is heavily customized based on
actor isolation/distributed/etc.) and any relevant notes to make
adjustments to the witness and/or requirement, e.g., adding
'distributed', 'async', 'throws', etc. Improve the diagnostics
slightly by providing Fix-Its when suggesting that we add "async"
and/or "throws".
With the last client of ActorIsolationRestriction gone, remove it
entirely.
Start collapsing the several implementations of actor isolation checking
into a single place that determines what it means to reference a declaration
from a given context, potentially supplying an instance for an actor. This
is partly cleanup, and partly staging for the implementation of the
Sendable restrictions introduced in SE-0338. The result of this check
falls into one of three categories:
* Reference occurs within the same concurrency domain (actor/task)
* Reference leaves an actor context to a nonisolated context (SE-0338)
* Reference enters the context of the actor, which might require a
combination of implicit async, implicit throws, and a "distributed" check.
Throughout this change I've sought to maintain the existing semantics,
even where I believe they are incorrect. The changes to the test cases
are not semantic changes, but reflect the unification of some
diagnostic paths that changed the diagnostic text but not when or how
those diagnostics are produced. Additionally, SE-0338 has not yet been
implemented, although this refactoring makes it easier to implement
SE-0338.
Use this new actor isolation checking scheme to implement the most
common actor-isolation check, which occurs when accessing a member of
an instance.
This effectively reverts 6823744779
The blanket removal of isolation in default-value expressions had
unintented consequences for important workflows. It's still
a problem that needs to be addressed, but we need to be more precise
about the problematic situations.
This patch delays the removal of redundant isolation for inferred
global-actor isolation to Swift 6 too, since we only warn about it
changing in Swift 5. Otherwise, only isolation that is a byproduct
of inference no longer needs an await, which will probably confuse
people.
This change is with respect to SE-327, which argues that the
non-static stored properties of ordinary structs do not need
global-actor isolation.
If a struct is a property-wrapper, then global-actor isolation
still applies to the `wrappedValue`, even if it's a stored property.
This is needed in order to support the propagation of global-actor
isolation through the wrapper, even when the programmer has opted
to use a stored property instead of a computed one for the
`wrappedValue`. Since this propagation is a useful pattern, I think
this exception is reasonable.
In Swift 5 mode, I only warned about the global-actor attribute
becoming unnecessary in the future, yet I was still returning
None for the global-actor attribute checking request. This led
to the attribute remaining unidentified, but also not removed.
During module serialization, this problem was manifesting as
emitting a typeless attribute, which when deserialized would
trigger a segfault.
As part of SE-327, global-actor isolation applied to
the instance-stored properties of a value type do
not require any isolation, since there is no way to
create a race on access to that storage.
https://github.com/apple/swift-evolution/blob/main/proposals/0327-actor-initializers.md#removing-redundant-isolation
This change turns global-actor annotations on such
properties into an error in Swift 6+, and a warning
in Swift 5 and earlier.
In addition, inference for global-actor isolation
no longer applies global-actor isolation to such
properties. Since this latter change only results
in warnings in existing Swift 5 code, about a now
superflous 'await', this change will happen in
Swift 5+.
Fixes rdar://87568381
Introduce the `@preconcurrency` attribute name for `@_predatesConcurrency`,
which has been the favored name in the pitch thread so far. Retain the
old name for now to help smooth migration.
It's possible to create an impossible set of constraints for
instance-member stored properties of a type. For example:
@MainActor func getStatus() -> Int { /* ... */ }
@PIDActor func genPID() -> ProcessID { /* ... */ }
class Process {
@MainActor var status: Int = getStatus()
@PIDActor var pid: ProcessID = genPID()
init() {} // Problem: what is the isolation of this init?
}
We cannot satisfy the isolation of the initilizing expressions,
which demand that genStatus and genPID are run with isolation
from a non-async designated initializer, which is not possible.
This patch changes the isolation for those initializer expressions
for instance members, saying that the isolation is unspecified.
fixes rdar://84225474
The first attempt to do this was in
https://github.com/apple/swift/pull/40652
But, I implemented that as a hard source break, since the isolation
was changed in a way that an error diagnostic would be emitted.
This commit reimplements the change more gently, as a warning for
Swift 5 users.
@IBAction calls are always delivered in the main thread, so reflect that
by inferring `@MainActor(unsafe)` for such methods whenever no other
actor isolation is provided.
Implements rdar://84474640.
Extend the diagnostics for `Sendable` conformances to always diagnose
missing `Sendable` conformances for nominal types that are within the
same module. The intuition here is that if the type is in the same
module, it can be updated and evaluated at the same time as code
requiring the `Sendable` conformance is introduced.
Another part of rdar://78269348.
Treat actors as being semantically `final` throughout the type checker.
This allows, for example, a non-`required` initializer to satisfy a
protocol requirement.
We're leaving the ABI open for actor inheritance should we need it.
Addresses rdar://78269551.
Rework the checking of actor member access to rely on "isolated" parameters
(and captures thereof) to determine whether one can synchronously access
an actor or not. This allows synchronous access via an "isolated" parameter
as a general notion, which subsumes the declaration-based "self" access.
Simplify the checking of and diagnostic reporting for actor member
access by collapsing a number of redundant diagnostics down into a
single, parameterized diagnostic with a single point of emission. This
normalizes the logic a bit.
The notion of "actor-isolated" currently exists at the declaration level.
For functions, it is going to be captured in the function type itself,
where 'self' is declared to be 'isolated'. Model isolation both
ways: the 'self' of a method that is isolated to an actor instance
will be 'isolated' as well.
We are still using declaration-based checking of actor isolation.
However, by mirroring this information we can move more incrementally
over to doing checking based on 'isolated' parameters.
Actor inheritance was removed in the second revision of SE-0306. Remove
the ability to inherit actors.
Note that this doesn't fully eliminate all vestigates of inheritance
from actors. There are simplifications that need to be performed
still, e.g., there's no need to distinguish
designated/convenience/required initializers. That will follow.
This new attribute can be used on parameters of `@Sendable async` type
to indicate that the closures arguments passed to such parameters
should inherit the actor context where they are formed, which is not
the normal behavior for `@Sendable` closures.
Another part of rdar://76927008.
Check actor isolation of calls to functions with global-actor-qualified
type. This closes a pre-existing loophole where a value of
global-actor-qualified function type could be called from any context.
Paired with this, references to global-actor-qualified function
declarations will get global-actor-qualified function type whenever
they are referenced within an experience, i.e., whenever we form a
value of that type. Such references can occur anywhere (one does not
need to be on the actor), and carrying the global actor along with the
function type ensures that they can only be called from the right
actor. For example:
@MainActor func onlyOnMainActor() { ... }
func callIt(_ fn: @MainActor () -> Void) {
fn() // error: not on the main actor, so cannot synchronously call
// this wasn't previously diagnosed
}
func passIt() {
callIt(onlyOnMainActor) // okay to pass the function
// used to be an error
}
While here, fix up some broken substitution logic for
global-actor-qualified function types and "override" actor isolation.
ASTScope only cares about attributes when lookup can be done inside of the
attribute, which isn't the case for implicit attributes because they're
typically built fully type-checked. This also avoids a crash when an
implicit attribute does not have a source range.
If a protocol is stated to be part of a global actor, infer that a type
that conforms to a protocol in its original definition is also part of
that global actor.
Addresses rdar://75992299.
Closures often end up being implicitly actor-isolated. Allow them to opt
out with `@actorIndependent`, as as other declarations can opt out of
actor isolation.
The presence of an unsafe global-actor attribute on something we can
infer from (e.g., a witnessed protocol requirement or overridden
declaration) was preventing propagation of actor-isolation attributes
from outer scopes. Only take "positive" results from such places.
