[refactoring] update ast structure of "Argument" and "ArgumentList" nodes

pkg/ast/node.go

@@ -90,7 +90,10 @@ func (n *Identifier) Accept(v NodeVisitor) {
 // ArgumentList node
 type ArgumentList struct {
 	Node
-	Arguments []Vertex
+	OpenParenthesisTkn  *token.Token
+	Arguments           []Vertex
+	SeparatorTkns       []*token.Token
+	CloseParenthesisTkn *token.Token
 }
 
 func (n *ArgumentList) Accept(v NodeVisitor) {
@@ -100,9 +103,9 @@ func (n *ArgumentList) Accept(v NodeVisitor) {
 // Argument node
 type Argument struct {
 	Node
-	Variadic    bool
-	IsReference bool
-	Expr        Vertex
+	VariadicTkn  *token.Token
+	AmpersandTkn *token.Token
+	Expr         Vertex
 }
 
 func (n *Argument) Accept(v NodeVisitor) {

pkg/ast/visitor/dump.go

@@ -240,16 +240,6 @@ func (v *Dump) Argument(n *ast.Argument) {
 	v.printIndentIfNotSingle(v.indent - 1)
 	v.print("&ast.Argument{\n")
 	v.printNode(n.GetNode())
-
-	if n.Variadic {
-		v.printIndent(v.indent)
-		v.print("Variadic: true,\n")
-	}
-
-	if n.IsReference {
-		v.printIndent(v.indent)
-		v.print("IsReference: true,\n")
-	}
 }
 
 func (v *Dump) StmtBreak(n *ast.StmtBreak) {