Merge pull request #59857 from tshortli/incorrect-override-cannot-be-less-available

Sema: Allow explicitly available overrides to be as available as their context

Author: tshortli

lib/Sema/TypeCheckDeclOverride.cpp

@@ -1714,7 +1714,15 @@ static bool isAvailabilitySafeForOverride(ValueDecl *override,
   AvailabilityContext baseInfo =
     AvailabilityInference::availableRange(base, ctx);
 
-  return baseInfo.isContainedIn(overrideInfo);
+  if (baseInfo.isContainedIn(overrideInfo))
+    return true;
+
+  // Allow overrides that are not as available as the base decl as long as the
+  // override is as available as its context.
+  auto overrideTypeAvailability = AvailabilityInference::inferForType(
+      override->getDeclContext()->getSelfTypeInContext());
+  
+  return overrideTypeAvailability.isContainedIn(overrideInfo);
 }
 
 /// Returns true if a diagnostic about an accessor being less available

test/Sema/availability_versions.swift

@@ -839,6 +839,26 @@ class SubWithLimitedMemberAvailability : SuperWithAlwaysAvailableMembers {
   }
 }
 
+@available(OSX, introduced: 10.51)
+class SubWithLimitedAvailablility : SuperWithAlwaysAvailableMembers {
+  override func shouldAlwaysBeAvailableMethod() {}
+  
+  override var shouldAlwaysBeAvailableProperty: Int {
+    get { return 10 }
+    set(newVal) {}
+  }
+  
+  override var setterShouldAlwaysBeAvailableProperty: Int {
+    get { return 9 }
+    set(newVal) {}
+  }
+
+  override var getterShouldAlwaysBeAvailableProperty: Int {
+    get { return 9 }
+    set(newVal) {}
+  }
+}
+
 class SuperWithLimitedMemberAvailability {
   @available(OSX, introduced: 10.51)
   func someMethod() {
@@ -879,6 +899,44 @@ class SubWithLargerMemberAvailability : SuperWithLimitedMemberAvailability {
   }
 }
 
+@available(OSX, introduced: 10.51)
+class SubWithLimitedAvailability : SuperWithLimitedMemberAvailability {
+  override func someMethod() {
+    super.someMethod()
+  }
+  
+  override var someProperty: Int {
+    get { super.someProperty }
+    set(newVal) { super.someProperty = newVal }
+  }
+}
+
+@available(OSX, introduced: 10.52)
+class SubWithMoreLimitedAvailability : SuperWithLimitedMemberAvailability {
+  override func someMethod() {
+    super.someMethod()
+  }
+  
+  override var someProperty: Int {
+    get { super.someProperty }
+    set(newVal) { super.someProperty = newVal }
+  }
+}
+
+@available(OSX, introduced: 10.52)
+class SubWithMoreLimitedAvailabilityAndRedundantMemberAvailability : SuperWithLimitedMemberAvailability {
+  @available(OSX, introduced: 10.52)
+  override func someMethod() {
+    super.someMethod()
+  }
+  
+  @available(OSX, introduced: 10.52)
+  override var someProperty: Int {
+    get { super.someProperty }
+    set(newVal) { super.someProperty = newVal }
+  }
+}
+
 @available(OSX, unavailable)
 class UnavailableSubWithLargerMemberAvailability : SuperWithLimitedMemberAvailability {
   override func someMethod() {