Dead emit dead store warnings when assigning nil to an ObjC object
pointer (for defensive programming).  This matches the behavior with
assigning NULL to a regular pointer.  Fixes <rdar://problem/7631278>.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@96985 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Checker/CheckDeadStores.cpp b/lib/Checker/CheckDeadStores.cpp
index 4a7ca70..31f9390 100644
--- a/lib/Checker/CheckDeadStores.cpp
+++ b/lib/Checker/CheckDeadStores.cpp
@@ -142,7 +142,8 @@
         if (VarDecl *VD = dyn_cast<VarDecl>(DR->getDecl())) {
           // Special case: check for assigning null to a pointer.
           //  This is a common form of defensive programming.
-          if (VD->getType()->isPointerType()) {
+          QualType T = VD->getType();
+          if (T->isPointerType() || T->isObjCObjectPointerType()) {
             if (B->getRHS()->isNullPointerConstant(Ctx,
                                               Expr::NPC_ValueDependentIsNull))
               return;