Merge pull request swiftlang#39446 from DougGregor/back-deploy-concurrency-cleanups-5.5

Back-deploymed concurrency availability fixes

Author: DougGregor

lib/AST/Availability.cpp

@@ -259,7 +259,7 @@ AvailabilityContext ASTContext::getSwift50Availability() {
     return AvailabilityContext(
                             VersionRange::allGTE(llvm::VersionTuple(12,2)));
   } else if (target.isWatchOS()) {
-    if (target.getArch() == llvm::Triple::ArchType::x86_64)
+    if (target.isArch64Bit())
       return AvailabilityContext::alwaysAvailable();
 
     return AvailabilityContext(
@@ -297,6 +297,9 @@ AvailabilityContext ASTContext::getSwift51Availability() {
     return AvailabilityContext(
                             VersionRange::allGTE(llvm::VersionTuple(13,0,0)));
   } else if (target.isWatchOS()) {
+    if (target.isArch64Bit())
+      return AvailabilityContext::alwaysAvailable();
+
     return AvailabilityContext(
                             VersionRange::allGTE(llvm::VersionTuple(6,0,0)));
   } else {

lib/Basic/Platform.cpp

@@ -417,14 +417,20 @@ swift::getSwiftRuntimeCompatibilityVersionForTarget(
       }
     }
   } else if (Triple.isWatchOS()) {
+    auto floorFor64bits = [&Triple](llvm::VersionTuple v) {
+      if (!Triple.isArch64Bit()) return v;
+      // 64-bit watchOS was introduced with Swift 5.3
+      return MAX(v, llvm::VersionTuple(5, 3));
+    };
+
     Triple.getWatchOSVersion(Major, Minor, Micro);
     if (Major <= 5) {
-      return llvm::VersionTuple(5, 0);
+      return floorFor64bits(llvm::VersionTuple(5, 0));
     } else if (Major <= 6) {
       if (Minor <= 1) {
-        return llvm::VersionTuple(5, 1);
+        return floorFor64bits(llvm::VersionTuple(5, 1));
       } else {
-        return llvm::VersionTuple(5, 2);
+        return floorFor64bits(llvm::VersionTuple(5, 2));
       }
     }
   }

lib/Sema/DerivedConformanceActor.cpp

@@ -153,11 +153,14 @@ static ValueDecl *deriveActor_unownedExecutor(DerivedConformance &derived) {
   if (property->getFormalAccess() == AccessLevel::Open)
     property->overwriteAccess(AccessLevel::Public);
 
-  // Clone any @available attributes from UnownedSerialExecutor.
-  // Really, though, the whole actor probably needs to be marked as
-  // unavailable.
-  for (auto attr: executorDecl->getAttrs().getAttributes<AvailableAttr>())
-    property->getAttrs().add(attr->clone(ctx, /*implicit*/true));
+  // Infer availability.
+  SmallVector<const Decl *, 2> asAvailableAs;
+  asAvailableAs.push_back(executorDecl);
+  if (auto enclosingDecl = property->getInnermostDeclWithAvailability())
+    asAvailableAs.push_back(enclosingDecl);
+
+  AvailabilityInference::applyInferredAvailableAttrs(
+      property, asAvailableAs, ctx);
 
   auto getter =
     derived.addGetterToReadOnlyDerivedProperty(property, executorType);

test/Concurrency/concurrency_availability.swift

@@ -11,3 +11,11 @@ actor A { }  // expected-error{{concurrency is only available in}}
 // Allow this without any availability for Historical Reasons.
 public func swift_deletedAsyncMethodError() async {
 }
+
+// Ensure that our synthesis of the actor's unownedExecutor does not cause
+// availability errors.
+@available(macOS 12.0, *)
+struct S {
+  actor A {
+  }
+}