Add availability gating for async function and actor type definitions.

Implements rdar://80098709.

Author: DougGregor

include/swift/AST/DiagnosticsSema.def

@@ -5254,6 +5254,10 @@ ERROR(availability_opaque_types_only_version_newer, none,
       "'some' return types are only available in %0 %1 or newer",
       (StringRef, llvm::VersionTuple))
 
+ERROR(availability_concurrency_only_version_newer, none,
+      "concurrency is only available in %0 %1 or newer",
+      (StringRef, llvm::VersionTuple))
+
 NOTE(availability_guard_with_version_check, none,
      "add 'if #available' version check", ())
 

lib/Sema/TypeCheckAvailability.cpp

@@ -1616,6 +1616,48 @@ void TypeChecker::diagnosePotentialOpaqueTypeUnavailability(
   fixAvailability(ReferenceRange, ReferenceDC, RequiredRange, Context);
 }
 
+static void diagnosePotentialConcurrencyUnavailability(
+    SourceRange ReferenceRange, const DeclContext *ReferenceDC,
+    const UnavailabilityReason &Reason) {
+  ASTContext &Context = ReferenceDC->getASTContext();
+
+  auto RequiredRange = Reason.getRequiredOSVersionRange();
+  {
+    auto Err =
+      Context.Diags.diagnose(
+          ReferenceRange.Start,
+          diag::availability_concurrency_only_version_newer,
+          prettyPlatformString(targetPlatform(Context.LangOpts)),
+          Reason.getRequiredOSVersionRange().getLowerEndpoint());
+
+    // Direct a fixit to the error if an existing guard is nearly-correct
+    if (fixAvailabilityByNarrowingNearbyVersionCheck(ReferenceRange,
+                                                     ReferenceDC,
+                                                     RequiredRange, Context, Err))
+      return;
+  }
+  fixAvailability(ReferenceRange, ReferenceDC, RequiredRange, Context);
+}
+
+
+void TypeChecker::checkConcurrencyAvailability(SourceRange ReferenceRange,
+                                               const DeclContext *ReferenceDC) {
+  // Check the availability of concurrency runtime support.
+  ASTContext &ctx = ReferenceDC->getASTContext();
+  if (ctx.LangOpts.DisableAvailabilityChecking)
+    return;
+  
+  auto runningOS =
+    TypeChecker::overApproximateAvailabilityAtLocation(
+      ReferenceRange.Start, ReferenceDC);
+  auto availability = ctx.getConcurrencyAvailability();
+  if (!runningOS.isContainedIn(availability)) {
+    diagnosePotentialConcurrencyUnavailability(
+      ReferenceRange, ReferenceDC,
+      UnavailabilityReason::requiresVersionRange(availability.getOSVersion()));
+  }
+}
+
 void TypeChecker::diagnosePotentialUnavailability(
     const ValueDecl *D, SourceRange ReferenceRange,
     const DeclContext *ReferenceDC,

lib/Sema/TypeCheckDeclPrimary.cpp

@@ -2315,6 +2315,9 @@ class DeclChecker : public DeclVisitor<DeclChecker> {
 
     TypeChecker::checkDeclAttributes(CD);
 
+    if (CD->isActor())
+      TypeChecker::checkConcurrencyAvailability(CD->getLoc(), CD);
+
     for (Decl *Member : CD->getABIMembers())
       visit(Member);
 
@@ -2609,6 +2612,9 @@ class DeclChecker : public DeclVisitor<DeclChecker> {
 
     checkImplementationOnlyOverride(FD);
 
+    if (FD->getAsyncLoc().isValid())
+      TypeChecker::checkConcurrencyAvailability(FD->getAsyncLoc(), FD);
+    
     if (requiresDefinition(FD) && !FD->hasBody()) {
       // Complain if we should have a body.
       FD->diagnose(diag::func_decl_without_brace);
@@ -2859,6 +2865,9 @@ class DeclChecker : public DeclVisitor<DeclChecker> {
     TypeChecker::checkDeclAttributes(CD);
     TypeChecker::checkParameterList(CD->getParameters(), CD);
 
+    if (CD->getAsyncLoc().isValid())
+      TypeChecker::checkConcurrencyAvailability(CD->getAsyncLoc(), CD);
+
     // Check whether this initializer overrides an initializer in its
     // superclass.
     if (!checkOverrides(CD)) {

lib/Sema/TypeChecker.h

@@ -1017,6 +1017,9 @@ diagnosePotentialOpaqueTypeUnavailability(SourceRange ReferenceRange,
                                           const DeclContext *ReferenceDC,
                                           const UnavailabilityReason &Reason);
 
+void checkConcurrencyAvailability(SourceRange ReferenceRange,
+                                  const DeclContext *ReferenceDC);
+
 /// Emits a diagnostic for a reference to a storage accessor that is
 /// potentially unavailable.
 void diagnosePotentialAccessorUnavailability(

stdlib/private/StdlibUnittest/CMakeLists.txt

@@ -49,6 +49,8 @@ add_swift_target_library(swiftStdlibUnittest ${SWIFT_STDLIB_LIBRARY_BUILD_TYPES}
   SWIFT_MODULE_DEPENDS_HAIKU Glibc _Concurrency
   SWIFT_MODULE_DEPENDS_WINDOWS CRT WinSDK _Concurrency
   SWIFT_COMPILE_FLAGS ${swift_stdlib_unittest_compile_flags} ${SWIFT_STANDARD_LIBRARY_SWIFT_FLAGS}
+    -Xfrontend -define-availability
+    -Xfrontend \"SwiftStdlib 5.5:macOS 12.0, iOS 15.0, watchOS 8.0, tvOS 15.0\"
   INSTALL_IN_COMPONENT stdlib-experimental
   DARWIN_INSTALL_NAME_DIR "${SWIFT_DARWIN_STDLIB_PRIVATE_INSTALL_NAME_DIR}"
   LINK_LIBRARIES ${swift_stdlib_unittest_link_libraries})

stdlib/private/StdlibUnittest/StdlibUnittest.swift

@@ -876,6 +876,7 @@ func _childProcess() {
 }
 
 #if SWIFT_ENABLE_EXPERIMENTAL_CONCURRENCY
+@available(SwiftStdlib 5.5, *)
 @inline(never)
 func _childProcessAsync() async {
   _installTrapInterceptor()
@@ -1370,6 +1371,7 @@ class _ParentProcess {
   }
 
 #if SWIFT_ENABLE_EXPERIMENTAL_CONCURRENCY
+  @available(SwiftStdlib 5.5, *)
   internal func runOneTestAsync(
     fullTestName: String,
     testSuite: TestSuite,
@@ -1536,6 +1538,7 @@ class _ParentProcess {
   }
 
 #if SWIFT_ENABLE_EXPERIMENTAL_CONCURRENCY
+  @available(SwiftStdlib 5.5, *)
   func runAsync() async {
     if let filter = _filter {
       print("StdlibUnittest: using filter: \(filter)")
@@ -1720,6 +1723,7 @@ public func runAllTests() {
 }
 
 #if SWIFT_ENABLE_EXPERIMENTAL_CONCURRENCY
+@available(SwiftStdlib 5.5, *)
 public func runAllTestsAsync() async {
   if PersistentState.runNoTestsWasCalled {
     print("runAllTests() called after runNoTests(). Aborting.")
@@ -1907,6 +1911,7 @@ public final class TestSuite {
   }
 
 #if SWIFT_ENABLE_EXPERIMENTAL_CONCURRENCY
+  @available(SwiftStdlib 5.5, *)
   func _runTestAsync(name testName: String, parameter: Int?) async {
     PersistentState.ranSomething = true
     for r in _allResettables {

stdlib/public/Concurrency/Errors.swift

@@ -13,6 +13,7 @@
 import Swift
 @_implementationOnly import _SwiftConcurrencyShims
 
+@available(SwiftStdlib 5.5, *)
 @_silgen_name("swift_deletedAsyncMethodError")
 public func swift_deletedAsyncMethodError() async {
     fatalError("Fatal error: Call of deleted method")

test/Concurrency/concurrency_availability.swift

@@ -0,0 +1,9 @@
+// RUN: %target-swift-frontend -parse-stdlib -target x86_64-apple-macosx10.15 -typecheck -verify %s
+// RUN: %target-swift-frontend -parse-stdlib -target x86_64-apple-macosx12 -typecheck %s
+// REQUIRES: OS=macosx
+
+func f() async { } // expected-error{{concurrency is only available in}}
+// expected-note@-1{{add @available}}
+
+actor A { }  // expected-error{{concurrency is only available in}}
+// expected-note@-1{{add @available}}