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[Concurrency] Don't allow erasing global actor isolation when the function value crosses an isolation boundary. #72607

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Merged
merged 1 commit into from
Mar 27, 2024
Merged

[Concurrency] Don't allow erasing global actor isolation when the function value crosses an isolation boundary. #72607

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11 changes: 9 additions & 2 deletions lib/Sema/TypeCheckConcurrency.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -1917,7 +1917,7 @@ bool swift::isAsyncDecl(ConcreteDeclRef declRef) {
/// \param ty a function type where \c globalActor was removed from it.
/// \return true if it is safe to drop the global-actor qualifier.
static bool safeToDropGlobalActor(
DeclContext *dc, Type globalActor, Type ty) {
DeclContext *dc, Type globalActor, Type ty, ApplyExpr *call) {
auto funcTy = ty->getAs<AnyFunctionType>();
if (!funcTy)
return false;
Expand All @@ -1942,6 +1942,12 @@ static bool safeToDropGlobalActor(
if (funcTy->isAsync())
return true;

// If the argument is passed over an isolation boundary, it's not
// safe to erase actor isolation, because the callee can call the
// function synchronously from outside the isolation domain.
if (call && call->getIsolationCrossing())
return false;

// fundamentally cannot be sendable if we want to drop isolation info
if (funcTy->isSendable())
return false;
Expand Down Expand Up @@ -2364,7 +2370,8 @@ namespace {
return;

auto dc = const_cast<DeclContext*>(getDeclContext());
if (!safeToDropGlobalActor(dc, fromActor, toType)) {
if (!safeToDropGlobalActor(dc, fromActor, toType,
getImmediateApply())) {
// otherwise, it's not a safe cast.
dc->getASTContext()
.Diags
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11 changes: 11 additions & 0 deletions test/Concurrency/actor_isolation.swift
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Original file line number Diff line number Diff line change
Expand Up @@ -468,6 +468,8 @@ actor Crystal {
await asyncGlobalActorFunc()
}

func crossIsolationBoundary(_ closure: () -> Void) async {}

@available(SwiftStdlib 5.1, *)
func testGlobalActorClosures() {
let _: Int = acceptAsyncClosure { @SomeGlobalActor in
Expand All @@ -480,6 +482,15 @@ func testGlobalActorClosures() {
}

acceptConcurrentClosure { @SomeGlobalActor in 5 } // expected-warning {{converting function value of type '@SomeGlobalActor @Sendable () -> Int' to '@Sendable () -> Int' loses global actor 'SomeGlobalActor'}}

@MainActor func test() async {
let closure = { @MainActor @Sendable in
MainActor.assertIsolated()
}

await crossIsolationBoundary(closure)
// expected-warning@-1 {{converting function value of type '@MainActor @Sendable () -> ()' to '() -> Void' loses global actor 'MainActor'; this is an error in the Swift 6 language mode}}
}
}

@available(SwiftStdlib 5.1, *)
Expand Down