fix off-by-one error



git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@41392 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/AST/Expr.cpp b/AST/Expr.cpp
index e71fcfa..d5fd241 100644
--- a/AST/Expr.cpp
+++ b/AST/Expr.cpp
@@ -231,6 +231,8 @@
   }
   case BinaryOperatorClass:
     return cast<BinaryOperator>(this)->isAssignmentOp();
+  case CompoundAssignOperator:
+    return true;
 
   case MemberExprClass:
   case ArraySubscriptExprClass: