fix some comments

src/graph/util/ExpressionUtils.h

@@ -167,7 +167,6 @@ class ExpressionUtils {
 
   static bool checkExprDepth(const Expression* expr);
 
- private:
   static constexpr int32_t kMaxDepth = 512;
 };
 

src/parser/parser.yy

@@ -558,7 +558,9 @@ expression
     : expression_internal {
         if(!graph::ExpressionUtils::checkExprDepth($1)){
             delete $1;
-            throw nebula::GraphParser::syntax_error(@1, "The above expression's depth exceeds the maximum depth:512!");
+            std::ostringstream errStr;
+            errStr << "The above expression's depth exceeds the maximum depth:" << graph::ExpressionUtils::kMaxDepth;
+            throw nebula::GraphParser::syntax_error(@1, errStr.str());
         }
         $$ = $1;
     }

tests/tck/features/expression/Depth.feature

@@ -75,7 +75,7 @@ Feature: Check Expression Depth
       1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 +
       1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 AS result
       """
-    Then a SyntaxError should be raised at runtime: The above expression's depth exceeds the maximum depth!
+    Then a SyntaxError should be raised at runtime: The above expression's depth exceeds the maximum depth
     When executing query:
       """
       YIELD 1 IS NULL IS NULL IS NULL IS NULL IS NULL IS NULL IS NULL IS NULL IS NULL IS NULL IS NULL IS
@@ -156,4 +156,4 @@ Feature: Check Expression Depth
       NULL IS NULL IS NULL IS NULL IS NULL IS NULL IS NULL IS NULL IS NULL IS NULL IS NULL IS NULL IS
       NULL IS NULL IS NULL IS NULL IS NULL IS NULL IS NULL IS NULL IS NULL IS NULL IS NULL AS result
       """
-    Then a SyntaxError should be raised at runtime: The above expression's depth exceeds the maximum depth!
+    Then a SyntaxError should be raised at runtime: The above expression's depth exceeds the maximum depth