Merge pull request #37233 from slavapestov/unavailable-conformance-fix

Sema: Allow unavailable conformances to be referenced from unavailable contexts

Author: slavapestov

lib/Sema/TypeCheckAvailability.cpp

@@ -1737,7 +1737,8 @@ static bool isInsideCompatibleUnavailableDeclaration(
   // but allow the use of types.
   PlatformKind platform = attr->Platform;
   if (platform == PlatformKind::none &&
-      !isa<TypeDecl>(D)) {
+      !isa<TypeDecl>(D) &&
+      !isa<ExtensionDecl>(D)) {
     return false;
   }
 

test/Sema/conformance_availability.swift

@@ -16,7 +16,7 @@ public struct HasUnavailableConformance1 {}
 
 @available(*, unavailable)
 extension HasUnavailableConformance1 : Horse {}
-// expected-note@-1 7{{conformance of 'HasUnavailableConformance1' to 'Horse' has been explicitly marked unavailable here}}
+// expected-note@-1 4{{conformance of 'HasUnavailableConformance1' to 'Horse' has been explicitly marked unavailable here}}
 
 func passUnavailableConformance1(x: HasUnavailableConformance1) {
   takesHorse(x) // expected-error {{conformance of 'HasUnavailableConformance1' to 'Horse' is unavailable}}
@@ -26,9 +26,9 @@ func passUnavailableConformance1(x: HasUnavailableConformance1) {
 
 @available(*, unavailable)
 func passUnavailableConformance1a(x: HasUnavailableConformance1) {
-  takesHorse(x) // expected-error {{conformance of 'HasUnavailableConformance1' to 'Horse' is unavailable}}
-  x.giddyUp() // expected-error {{conformance of 'HasUnavailableConformance1' to 'Horse' is unavailable}}
-  _ = UsesHorse<HasUnavailableConformance1>.self // expected-error {{conformance of 'HasUnavailableConformance1' to 'Horse' is unavailable}}
+  takesHorse(x)
+  x.giddyUp()
+  _ = UsesHorse<HasUnavailableConformance1>.self
 }
 
 // Platform unavailability
@@ -351,3 +351,15 @@ extension Car {
 @available(macOS 100, *)
 extension ClownCar : Vehicle {}
 // expected-error@-1 {{protocol 'Vehicle' requires 'move()' to be available in macOS 100 and newer}}
+
+// rdar://problem/75430966 - Allow using unavailable conformances from unavailable contexts.
+@available(*, unavailable)
+public enum UnavailableEnum {
+  case horse
+}
+
+@available(*, unavailable)
+extension UnavailableEnum : Swift.Equatable {}
+
+@available(*, unavailable)
+extension UnavailableEnum : Swift.Hashable {}