Refine 'deprecated' checking for Objective-C classes/methods.

- If a deprecated class refers to another deprecated class, do not warn.
- @implementations of a deprecated class can refer to other deprecated things.

Fixes <rdar://problem/15407366> and <rdar://problem/15466783>.

llvm-svn: 195259
diff --git a/clang/lib/Sema/SemaDecl.cpp b/clang/lib/Sema/SemaDecl.cpp
index 4fe5576..cd64311 100644
--- a/clang/lib/Sema/SemaDecl.cpp
+++ b/clang/lib/Sema/SemaDecl.cpp
@@ -12994,5 +12994,22 @@
 
 AvailabilityResult Sema::getCurContextAvailability() const {
   const Decl *D = cast<Decl>(getCurObjCLexicalContext());
+  // If we are within an Objective-C method, we should consult
+  // both the availability of the method as well as the
+  // enclosing class.  If the class is (say) deprecated,
+  // the entire method is considered deprecated from the
+  // purpose of checking if the current context is deprecated.
+  if (const ObjCMethodDecl *MD = dyn_cast<ObjCMethodDecl>(D)) {
+    AvailabilityResult R = MD->getAvailability();
+    if (R != AR_Available)
+      return R;
+    D = MD->getClassInterface();
+  }
+  // If we are within an Objective-c @implementation, it
+  // gets the same availability context as the @interface.
+  else if (const ObjCImplementationDecl *ID =
+            dyn_cast<ObjCImplementationDecl>(D)) {
+    D = ID->getClassInterface();
+  }
   return D->getAvailability();
 }