Index: lib/Sema/SemaDeclAttr.cpp
===================================================================
--- lib/Sema/SemaDeclAttr.cpp
+++ lib/Sema/SemaDeclAttr.cpp
@@ -7513,6 +7513,15 @@
 
   bool TraverseLambdaExpr(LambdaExpr *E) { return true; }
 
+  bool TraverseCaseStmt(CaseStmt *CS) {
+    // for 'case X:' statements, don't bother looking at the 'X'; it can't lead
+    // to any useful diagnostics.
+    for (Stmt *Child : llvm::drop_begin(CS->children(), 1))
+      if (!Base::TraverseStmt(Child))
+        return false;
+    return true;
+  }
+
   bool VisitObjCPropertyRefExpr(ObjCPropertyRefExpr *PRE) {
     if (PRE->isClassReceiver())
       DiagnoseDeclAvailability(PRE->getClassReceiver(), PRE->getReceiverLocation());
Index: test/SemaObjC/unguarded-availability.m
===================================================================
--- test/SemaObjC/unguarded-availability.m
+++ test/SemaObjC/unguarded-availability.m
@@ -287,3 +287,22 @@
 @interface BaseClass (CategoryWithNewProtocolRequirement) <NewProtocol>
 
 @end
+
+typedef enum {
+  AK_Dodo __attribute__((availability(macos, deprecated=10.3))), // expected-note 2 {{marked deprecated here}}
+  AK_Cat __attribute__((availability(macos, introduced=10.4))),
+  AK_CyborgCat __attribute__((availability(macos, introduced=10.12))), // expected-note {{marked partial here}}
+} Animals;
+
+void switchAnimals(Animals a) {
+  switch (a) {
+  case AK_Dodo: break; // expected-warning{{'AK_Dodo' is deprecated}}
+  case AK_Cat: break;
+  case AK_Cat|AK_CyborgCat: break; // expected-warning{{case value not in enum}}
+  case AK_CyborgCat: break; // no warn
+  }
+
+  (void)AK_Dodo; // expected-warning{{'AK_Dodo' is deprecated}}
+  (void)AK_Cat; // no warning
+  (void)AK_CyborgCat; // expected-warning{{'AK_CyborgCat' is only available on macOS 10.12 or newer}} expected-note {{@available}}
+}