Objective-C: Produce precise diagnostic when

'isa' ivar is accessed provided it is the first
ivar. Fixit hint will follow in another patch.
This is continuation of // rdar://13503456


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@178313 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 36 insertions, 2 deletions

diff --git a/lib/Sema/SemaExpr.cpp b/lib/Sema/SemaExpr.cpp
index 238d833c38..c6882908c2 100644
--- a/lib/Sema/SemaExpr.cpp
+++ b/lib/Sema/SemaExpr.cpp
@@ -450,6 +450,34 @@ static void CheckForNullPointerDereference(Sema &S, Expr *E) {
   }
 }
 
+static void DiagnoseDirectIsaAccess(Sema &S, const ObjCIvarRefExpr *OIRE,
+                                    bool IsAssign) {
+  const ObjCIvarDecl *IV = OIRE->getDecl();
+  if (!IV)
+    return;
+  
+  DeclarationName MemberName = IV->getDeclName();
+  IdentifierInfo *Member = MemberName.getAsIdentifierInfo();
+  if (!Member || !Member->isStr("isa"))
+    return;
+  
+  const Expr *Base = OIRE->getBase();
+  QualType BaseType = Base->getType();
+  if (OIRE->isArrow())
+    BaseType = BaseType->getPointeeType();
+  if (const ObjCObjectType *OTy = BaseType->getAs<ObjCObjectType>())
+    if (ObjCInterfaceDecl *IDecl = OTy->getInterface()) {
+      ObjCInterfaceDecl *ClassDeclared = 0;
+      ObjCIvarDecl *IV = IDecl->lookupInstanceVariable(Member, ClassDeclared);
+      if (!ClassDeclared->getSuperClass()
+          && (*ClassDeclared->ivar_begin()) == IV) {
+        S.Diag(OIRE->getLocation(), IsAssign ? diag::warn_objc_isa_assign
+                                             : diag::warn_objc_isa_use);
+        S.Diag(IV->getLocation(), diag::note_ivar_decl);
+      }
+    }
+}
+
 ExprResult Sema::DefaultLvalueConversion(Expr *E) {
   // Handle any placeholder expressions which made it here.
   if (E->getType()->isPlaceholderType()) {
@@ -503,7 +531,10 @@ ExprResult Sema::DefaultLvalueConversion(Expr *E) {
     else
       Diag(E->getExprLoc(), diag::warn_objc_isa_use);
   }
-
+  else if (const ObjCIvarRefExpr *OIRE =
+            dyn_cast<ObjCIvarRefExpr>(E->IgnoreParenCasts()))
+    DiagnoseDirectIsaAccess(*this, OIRE, false);
+  
   // C++ [conv.lval]p1:
   //   [...] If T is a non-class type, the type of the prvalue is the
   //   cv-unqualified version of T. Otherwise, the type of the
@@ -8561,7 +8592,10 @@ ExprResult Sema::CreateBuiltinBinOp(SourceLocation OpLoc,
     else
       Diag(LHS.get()->getExprLoc(), diag::warn_objc_isa_assign);
   }
-
+  else if (const ObjCIvarRefExpr *OIRE =
+           dyn_cast<ObjCIvarRefExpr>(LHS.get()->IgnoreParenCasts()))
+    DiagnoseDirectIsaAccess(*this, OIRE, true);
+  
   if (CompResultTy.isNull())
     return Owned(new (Context) BinaryOperator(LHS.take(), RHS.take(), Opc,
                                               ResultTy, VK, OK, OpLoc,