objective-c arc: Issue warning under -Wreceiver-is-weak

if receiver is a 'weak' property, by type or by attribute.
// rdar://10225276


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@155159 91177308-0d34-0410-b5e6-96231b3b80d8

include/clang/Basic/DiagnosticSemaKinds.td

@@ -660,7 +660,8 @@ def warn_arc_perform_selector_leaks : Warning<
 def err_gc_weak_property_strong_type : Error<
   "weak attribute declared on a __strong type property in GC mode">;
 def warn_receiver_is_weak : Warning <
-  "weak receiver may be unpredictably null in ARC mode">,
+  "weak %select{receiver|property|implicit property}0 may be "
+  "unpredictably null in ARC mode">,
   InGroup<DiagGroup<"receiver-is-weak">>, DefaultIgnore;
 
 def error_synthesized_ivar_yet_not_supported : Error<

include/clang/Sema/Sema.h

@@ -5901,6 +5901,9 @@ public:
                                            bool IsInstance);
 
   bool inferObjCARCLifetime(ValueDecl *decl);
+  
+  void DiagnoseARCUseOfWeakReceiver(NamedDecl *PDecl,
+                                    QualType T, SourceLocation Loc);
 
   ExprResult
   HandleExprPropertyRefExpr(const ObjCObjectPointerType *OPT,

lib/Sema/SemaExprObjC.cpp

@@ -1323,6 +1323,32 @@ ObjCMethodDecl *Sema::LookupMethodInQualifiedType(Selector Sel,
   return 0;
 }
 
+void 
+Sema::DiagnoseARCUseOfWeakReceiver(NamedDecl *PDecl,
+                                   QualType T, SourceLocation Loc) {
+  if (!getLangOpts().ObjCAutoRefCount)
+    return;
+  
+  if (T.getObjCLifetime() == Qualifiers::OCL_Weak) {
+    Diag(Loc, diag::warn_receiver_is_weak) 
+      << (!PDecl ? 0 : (isa<ObjCPropertyDecl>(PDecl) ? 1 : 2));
+    if (PDecl) {
+      if (isa<ObjCPropertyDecl>(PDecl))
+        Diag(PDecl->getLocation(), diag::note_property_declare);
+      else
+        Diag(PDecl->getLocation(), diag::note_method_declared_at) << PDecl;
+    }
+    return;
+  }
+  
+  if (PDecl)
+    if (ObjCPropertyDecl *Prop = dyn_cast<ObjCPropertyDecl>(PDecl))
+      if (Prop->getPropertyAttributes() & ObjCPropertyDecl::OBJC_PR_weak) {
+        Diag(Loc, diag::warn_receiver_is_weak) << 1;
+        Diag(Prop->getLocation(), diag::note_property_declare);
+      }
+}
+
 /// HandleExprPropertyRefExpr - Handle foo.bar where foo is a pointer to an
 /// objective C interface.  This is a property reference expression.
 ExprResult Sema::
@@ -1354,7 +1380,6 @@ HandleExprPropertyRefExpr(const ObjCObjectPointerType *OPT,
     // Check whether we can reference this property.
     if (DiagnoseUseOfDecl(PD, MemberLoc))
       return ExprError();
-             
     if (Super)
       return Owned(new (Context) ObjCPropertyRefExpr(PD, Context.PseudoObjectTy,
                                                      VK_LValue, OK_ObjCProperty,
@@ -1372,7 +1397,7 @@ HandleExprPropertyRefExpr(const ObjCObjectPointerType *OPT,
       // Check whether we can reference this property.
       if (DiagnoseUseOfDecl(PD, MemberLoc))
         return ExprError();
-      
+
       if (Super)
         return Owned(new (Context) ObjCPropertyRefExpr(PD,
                                                        Context.PseudoObjectTy,
@@ -2379,10 +2404,10 @@ ExprResult Sema::BuildInstanceMessage(Expr *Receiver,
   }
 
   if (getLangOpts().ObjCAutoRefCount) {
-    if (Receiver &&
+    if (Receiver)
-        (Receiver->IgnoreParenImpCasts()->getType().getObjCLifetime() 
+      DiagnoseARCUseOfWeakReceiver(0 /* PDecl */,
-          == Qualifiers::OCL_Weak))
+                                   Receiver->IgnoreParenImpCasts()->getType(),
-      Diag(Receiver->getLocStart(), diag::warn_receiver_is_weak);
+                                   Receiver->getLocStart());
     
     // In ARC, annotate delegate init calls.
     if (Result->getMethodFamily() == OMF_init &&

lib/Sema/SemaPseudoObject.cpp

@@ -478,6 +478,8 @@ bool ObjCPropertyOpBuilder::findGetter() {
   if (RefExpr->isImplicitProperty()) {
     if ((Getter = RefExpr->getImplicitPropertyGetter())) {
       GetterSelector = Getter->getSelector();
+      S.DiagnoseARCUseOfWeakReceiver(Getter, Getter->getResultType(),
+                                     RefExpr->getLocation());
       return true;
     }
     else {
@@ -497,6 +499,8 @@ bool ObjCPropertyOpBuilder::findGetter() {
   }
 
   ObjCPropertyDecl *prop = RefExpr->getExplicitProperty();
+  S.DiagnoseARCUseOfWeakReceiver(prop, prop->getType(),
+                                 RefExpr->getLocation());
   Getter = LookupMethodInReceiverType(S, prop->getGetterName(), RefExpr);
   return (Getter != 0);
 }

test/SemaObjC/weak-receiver-warn.m

@@ -17,3 +17,34 @@ void test0(Test0 *x) {
   [weakx setBlock: ^{ [x actNow]; }]; // expected-warning {{weak receiver may be unpredictably null in ARC mode}}
   weakx.block = ^{ [x actNow]; };
 }
+
+@interface Test
+{
+  __weak Test* weak_prop;
+}
+- (void) Meth;
+@property  __weak Test* weak_prop; // expected-note 2 {{property declared here}}
+@property (weak, atomic) id weak_atomic_prop; // expected-note 2 {{property declared here}}
+- (__weak id) P; // expected-note 2 {{method 'P' declared here}}
+@end
+
+@implementation Test
+- (void) Meth {
+    if (self.weak_prop) { // expected-warning {{weak property may be unpredictably null in ARC mode}}
+      self.weak_prop = 0;
+    }
+    if (self.weak_atomic_prop) { // expected-warning {{weak property may be unpredictably null in ARC mode}}
+      self.weak_atomic_prop = 0;
+    }
+    [self.weak_prop Meth]; // expected-warning {{weak property may be unpredictably null in ARC mode}}
+    id pi = self.P; // expected-warning {{weak implicit property may be unpredictably null in ARC mode}}
+
+    [self.weak_atomic_prop Meth];  // expected-warning {{weak property may be unpredictably null in ARC mode}}
+
+    [self.P Meth];		   // expected-warning {{weak implicit property may be unpredictably null in ARC mode}}
+}
+
+- (__weak id) P { return 0; }
+@dynamic weak_prop, weak_atomic_prop;
+@end
+