Sema: When diagnosing required explicit availability, skip members of extensions that have been declared explicitly unavailable. The existing logic only checked for an unavailable attr in the direct attributes of the decl.

Resolves rdar://85429703

Author: tshortli

lib/Sema/TypeCheckAvailability.cpp

@@ -3924,11 +3924,14 @@ static bool declNeedsExplicitAvailability(const Decl *decl) {
       decl->isImplicit())
     return false;
 
+  // Skip unavailable decls.
+  if (AvailableAttr::isUnavailable(decl))
+    return false;
+
   // Warn on decls without an introduction version.
   auto &ctx = decl->getASTContext();
   auto safeRangeUnderApprox = AvailabilityInference::availableRange(decl, ctx);
-  return !safeRangeUnderApprox.getOSVersion().hasLowerEndpoint() &&
-         !decl->getAttrs().isUnavailable(ctx);
+  return !safeRangeUnderApprox.getOSVersion().hasLowerEndpoint();
 }
 
 void swift::checkExplicitAvailability(Decl *decl) {

test/attr/require_explicit_availability.swift

@@ -7,6 +7,11 @@ public struct S { // expected-warning {{public declarations should have an avail
   public func method() { }
 }
 
+@available(macOS, unavailable)
+public struct UnavailableStruct {
+  public func okMethod() { }
+}
+
 public func foo() { bar() } // expected-warning {{public declarations should have an availability attribute when building with -require-explicit-availability}} {{1-1=@available(macOS 10.10, *)\n}}
 
 @usableFromInline
@@ -41,10 +46,25 @@ public func +(lhs: S, rhs: S) -> S { } // expected-warning {{public declarations
 
 public enum E { } // expected-warning {{public declarations should have an availability attribute when building with -require-explicit-availability}} {{1-1=@available(macOS 10.10, *)\n}}
 
+@available(macOS, unavailable)
+public enum UnavailableEnum {
+  case caseOk
+}
+
 public class C { } // expected-warning {{public declarations should have an availability attribute when building with -require-explicit-availability}} {{1-1=@available(macOS 10.10, *)\n}}
 
+@available(macOS, unavailable)
+public class UnavailableClass {
+  public func okMethod() { }
+}
+
 public protocol P { } // expected-warning {{public declarations should have an availability attribute when building with -require-explicit-availability}} {{1-1=@available(macOS 10.10, *)\n}}
 
+@available(macOS, unavailable)
+public protocol UnavailableProto {
+  func requirementOk()
+}
+
 private protocol PrivateProto { }
 
 extension S { // expected-warning {{public declarations should have an availability attribute when building with -require-explicit-availability}} {{1-1=@available(macOS 10.10, *)\n}}
@@ -56,11 +76,19 @@ extension S {
   public func okWhenTheExtensionHasAttribute() { }
 }
 
+@available(macOS, unavailable)
+extension S {
+  public func okWhenTheExtensionIsUnavailable() { }
+}
+
 extension S {
   internal func dontWarnWithoutPublicMembers() { }
   private func dontWarnWithoutPublicMembers1() { }
 }
 
+// An empty extension should be ok.
+extension S { }
+
 extension S : P { // expected-warning {{public declarations should have an availability attribute when building with -require-explicit-availability}} {{1-1=@available(macOS 10.10, *)\n}}
 }
 
@@ -96,6 +124,9 @@ public var publicVar = S() // expected-warning {{public declarations should have
 @available(macOS 10.10, *)
 public var publicVarOk = S()
 
+@available(macOS, unavailable)
+public var unavailablePublicVarOk = S()
+
 public var (a, b) = (S(), S()) // expected-warning {{public declarations should have an availability attribute when building with -require-explicit-availability}} {{1-1=@available(macOS 10.10, *)\n}}
 
 @available(macOS 10.10, *)
@@ -112,6 +143,11 @@ public var implicitGetOk: S {
   return S()
 }
 
+@available(macOS, unavailable)
+public var unavailableImplicitGetOk: S {
+  return S()
+}
+
 public var computed: S { // expected-warning {{public declarations should have an availability attribute when building with -require-explicit-availability}} {{1-1=@available(macOS 10.10, *)\n}}
   get { return S() }
   set { }