Warn if direct accessing synthesized ivar backing the property in

nonofragile-abi2. Fixes //rdar://8673791

llvm-svn: 119543

clang/include/clang/Basic/DiagnosticSemaKinds.td

@@ -2698,6 +2698,9 @@ def note_condition_assign_to_comparison : Note<
 def note_condition_assign_silence : Note<
   "place parentheses around the assignment to silence this warning">;
 
+def warn_synthesized_ivar_access : Warning<
+  "direct access of synthesized ivar by using property access %0">,
+  InGroup<NonfragileAbi2>, DefaultIgnore;
 def warn_ivar_variable_conflict : Warning<
   "when default property synthesis is on, "
   "%0 lookup will access property ivar instead of global variable">, 

clang/lib/Sema/SemaExpr.cpp

@@ -1446,9 +1446,15 @@ ExprResult Sema::ActOnIdExpression(Scope *S,
       if (Ex) return Owned(Ex);
       // Synthesize ivars lazily
       if (getLangOptions().ObjCNonFragileABI2) {
-        if (SynthesizeProvisionalIvar(*this, R, II, NameLoc))
+        if (SynthesizeProvisionalIvar(*this, R, II, NameLoc)) {
+          if (const ObjCPropertyDecl *Property = 
+                canSynthesizeProvisionalIvar(II)) {
+            Diag(NameLoc, diag::warn_synthesized_ivar_access) << II;
+            Diag(Property->getLocation(), diag::note_property_declare);
+          }
           return ActOnIdExpression(S, SS, Id, HasTrailingLParen,
                                    isAddressOfOperand);
+        }
       }
       // for further use, this must be set to false if in class method.
       IvarLookupFollowUp = getCurMethodDecl()->isInstanceMethod();

clang/test/SemaObjC/direct-synthesized-ivar-access.m

@@ -0,0 +1,14 @@
+// RUN: %clang_cc1 -Wnonfragile-abi2 -fsyntax-only -fobjc-nonfragile-abi2 -verify %s
+// rdar://8673791
+
+@interface I {
+}
+
+@property int IVAR; // expected-note {{property declared here}}
+- (int) OK;
+@end
+
+@implementation I
+- (int) Meth { return IVAR; } // expected-warning {{direct access of synthesized ivar by using property access 'IVAR'}}
+- (int) OK { return self.IVAR; }
+@end