Let Expr::HasSideEffects() return false for NULL, bool literals, this, and nullptr.

Fixes PR13413, -Wunused-private-field now warns on unused fields initialized to NULL.



git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@160541 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/AST/ExprConstant.cpp b/lib/AST/ExprConstant.cpp
index f88206c..cbcd5e8 100644
--- a/lib/AST/ExprConstant.cpp
+++ b/lib/AST/ExprConstant.cpp
@@ -2340,6 +2340,12 @@
     return Visit(E->getSubExpr());
   }
   bool VisitUnaryOperator(const UnaryOperator *E) { return Visit(E->getSubExpr()); }
+  bool VisitGNUNullExpr(const GNUNullExpr *E) { return false; }
+  bool VisitCXXBoolLiteralExpr(const CXXBoolLiteralExpr *E) { return false; }
+  bool VisitCXXThisExpr(const CXXThisExpr *E) { return false; }
+  bool VisitCXXNullPtrLiteralExpr(const CXXNullPtrLiteralExpr *E) {
+    return false;
+  }
     
   // Has side effects if any element does.
   bool VisitInitListExpr(const InitListExpr *E) {