[refactoring] update ast structure of "Unset" node

pkg/ast/node.go

@@ -783,7 +783,12 @@ func (n *StmtTry) Accept(v NodeVisitor) {
 // StmtUnset node
 type StmtUnset struct {
 	Node
-	Vars []Vertex
+	UnsetTkn            *token.Token
+	OpenParenthesisTkn  *token.Token
+	Vars                []Vertex
+	SeparatorTkns       []*token.Token
+	CloseParenthesisTkn *token.Token
+	SemiColonTkn        *token.Token
 }
 
 func (n *StmtUnset) Accept(v NodeVisitor) {

pkg/ast/visitor/filter_tokens.go

@@ -204,3 +204,12 @@ func (v *FilterTokens) StmtEcho(n *ast.StmtEcho) {
 func (v *FilterTokens) StmtInlineHtml(n *ast.StmtInlineHtml) {
 	n.InlineHtmlTkn = nil
 }
+
+func (v *FilterTokens) StmtUnset(n *ast.StmtUnset) {
+	n.UnsetTkn = nil
+	n.OpenParenthesisTkn = nil
+	n.SeparatorTkns = nil
+	n.CloseParenthesisTkn = nil
+	n.SemiColonTkn = nil
+	n.SemiColonTkn = nil
+}