-Warc-repeated-use-of-weak: fix a use-of-uninitialized and add a test case.

Fix-up for r165718, should get the buildbots back online.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@165723 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Sema/ScopeInfo.cpp b/lib/Sema/ScopeInfo.cpp
index c1d6629..4d29a34 100644
--- a/lib/Sema/ScopeInfo.cpp
+++ b/lib/Sema/ScopeInfo.cpp
@@ -159,7 +159,7 @@
     Uses = WeakObjectUses.find(WeakObjectProfileTy(IvarE));
   else if (const DeclRefExpr *DRE = dyn_cast<DeclRefExpr>(E))
     Uses = WeakObjectUses.find(WeakObjectProfileTy(DRE));
-  else if (const ObjCMessageExpr *MsgE = dyn_cast<ObjCMessageExpr>(MsgE)) {
+  else if (const ObjCMessageExpr *MsgE = dyn_cast<ObjCMessageExpr>(E)) {
     Uses = WeakObjectUses.end();
     if (const ObjCMethodDecl *MD = MsgE->getMethodDecl()) {
       if (const ObjCPropertyDecl *Prop = MD->findPropertyDecl()) {