Sema: Only diagnose explicit unavailable Clang enum elements

lib/Sema/TypeCheckPattern.cpp

@@ -39,8 +39,15 @@ using namespace swift;
 static EnumElementDecl *
 extractEnumElement(DeclContext *DC, SourceLoc UseLoc,
                    const VarDecl *constant) {
-  diagnoseDeclAvailability(constant, UseLoc, nullptr,
-                           ExportContext::forFunctionBody(DC, UseLoc));
+  auto &ctx = DC->getASTContext();
+  auto availabilityContext = TypeChecker::availabilityAtLocation(UseLoc, DC);
+  if (auto unmetRequirement =
+          checkDeclarationAvailability(constant, DC, availabilityContext)) {
+    // Only diagnose explicit unavailability.
+    if (!unmetRequirement->getRequiredNewerAvailabilityRange(ctx))
+      diagnoseDeclAvailability(constant, UseLoc, nullptr,
+                               ExportContext::forFunctionBody(DC, UseLoc));
+  }
 
   const FuncDecl *getter = constant->getAccessor(AccessorKind::Get);
   if (!getter)

test/ClangImporter/availability_macosx.swift

@@ -4,6 +4,7 @@
 
 // REQUIRES: OS=macosx
 
+import AppKit
 import Foundation
 import AvailabilityExtras
 
@@ -14,3 +15,35 @@ func test_unavailable_because_deprecated() {
 func test_swift_unavailable_wins() {
   unavailableWithOS() // expected-error {{'unavailableWithOS()' is unavailable in Swift}}
 }
+
+func bezierPathElementToInteger(_ e: NSBezierPathElement) -> Int {
+  switch e {
+  case .moveTo: return 1
+  case .lineTo: return 2
+  case .curveTo: return 3 // no error
+  case .cubicCurveTo: return 3
+  case .closePath: return 4
+  case .quadraticCurveTo: return 5
+  @unknown default: return -1
+  }
+}
+
+func integerToBezierPathElement(_ i: Int) -> NSBezierPathElement {
+  // expected-note@-1 2 {{add @available attribute to enclosing global function}}
+  switch i {
+  case 1:
+    return .moveTo
+  case 2:
+    return .lineTo
+  case 3:
+    return .curveTo // expected-error {{'curveTo' is only available in}}
+    // expected-note@-1 {{add 'if #available' version check}}
+  case 4:
+    return .closePath
+  case 5:
+    return .quadraticCurveTo // expected-error {{'quadraticCurveTo' is only available in}}
+    // expected-note@-1 {{add 'if #available' version check}}
+  default:
+    fatalError()
+  }
+}

test/Inputs/clang-importer-sdk/usr/include/AppKit.h

@@ -306,3 +306,12 @@ typedef NSPoint *NSPointPointer;
 @interface NSDocument (URL)
 @property (copy,nonnull) NSURL *URL;
 @end
+
+typedef NS_ENUM(NSUInteger, NSBezierPathElement) {
+    NSBezierPathElementMoveTo,
+    NSBezierPathElementLineTo,
+    NSBezierPathElementCubicCurveTo __attribute__((availability(macosx,introduced=52))),
+    NSBezierPathElementClosePath,
+    NSBezierPathElementQuadraticCurveTo __attribute__((availability(macosx,introduced=52))),
+    NSBezierPathElementCurveTo __attribute__((availability(macosx,introduced=51,deprecated=52,message="Use NSBezierPathElementCubicCurveTo"))) = NSBezierPathElementCubicCurveTo,
+};