Index: cfe/trunk/include/clang/AST/Expr.h
===================================================================
--- cfe/trunk/include/clang/AST/Expr.h
+++ cfe/trunk/include/clang/AST/Expr.h
@@ -2212,11 +2212,11 @@
   /// getArg - Return the specified argument.
   Expr *getArg(unsigned Arg) {
     assert(Arg < NumArgs && "Arg access out of range!");
-    return cast<Expr>(SubExprs[Arg+getNumPreArgs()+PREARGS_START]);
+    return cast_or_null<Expr>(SubExprs[Arg + getNumPreArgs() + PREARGS_START]);
   }
   const Expr *getArg(unsigned Arg) const {
     assert(Arg < NumArgs && "Arg access out of range!");
-    return cast<Expr>(SubExprs[Arg+getNumPreArgs()+PREARGS_START]);
+    return cast_or_null<Expr>(SubExprs[Arg + getNumPreArgs() + PREARGS_START]);
   }
 
   /// setArg - Set the specified argument.
Index: cfe/trunk/lib/AST/Expr.cpp
===================================================================
--- cfe/trunk/lib/AST/Expr.cpp
+++ cfe/trunk/lib/AST/Expr.cpp
@@ -1252,7 +1252,7 @@
     return cast<CXXOperatorCallExpr>(this)->getLocStart();
 
   SourceLocation begin = getCallee()->getLocStart();
-  if (begin.isInvalid() && getNumArgs() > 0)
+  if (begin.isInvalid() && getNumArgs() > 0 && getArg(0))
     begin = getArg(0)->getLocStart();
   return begin;
 }
@@ -1261,7 +1261,7 @@
     return cast<CXXOperatorCallExpr>(this)->getLocEnd();
 
   SourceLocation end = getRParenLoc();
-  if (end.isInvalid() && getNumArgs() > 0)
+  if (end.isInvalid() && getNumArgs() > 0 && getArg(getNumArgs() - 1))
     end = getArg(getNumArgs() - 1)->getLocEnd();
   return end;
 }