[refactoring] update ast structure of "Return" node

pkg/ast/node.go

@@ -618,7 +618,9 @@ func (n *StmtPropertyList) Accept(v NodeVisitor) {
 // StmtReturn node
 type StmtReturn struct {
 	Node
-	Expr Vertex
+	ReturnTkn    *token.Token
+	Expr         Vertex
+	SemiColonTkn *token.Token
 }
 
 func (n *StmtReturn) Accept(v NodeVisitor) {

pkg/ast/visitor/filter_tokens.go

@@ -173,3 +173,8 @@ func (v *FilterTokens) StmtContinue(n *ast.StmtContinue) {
 	n.ContinueTkn = nil
 	n.SemiColonTkn = nil
 }
+
+func (v *FilterTokens) StmtReturn(n *ast.StmtReturn) {
+	n.ReturnTkn = nil
+	n.SemiColonTkn = nil
+}