php8.1: added readonly modifier (#6)

pkg/visitor/printer/printer.go

@@ -147,7 +147,7 @@ func (p *printer) Nullable(n *ast.Nullable) {
 
 func (p *printer) Parameter(n *ast.Parameter) {
 	p.printList(n.AttrGroups)
-	p.printNode(n.Visibility)
+	p.printList(n.Modifiers)
 	p.printNode(n.Type)
 	p.printToken(n.AmpersandTkn, nil)
 	p.printToken(n.VariadicTkn, nil)

pkg/visitor/printer/printer_php8_1_test.go

@@ -0,0 +1,25 @@
+package printer_test
+
+import (
+	"testing"
+
+	"github.com/VKCOM/php-parser/internal/tester"
+)
+
+func TestParseAndPrintReadonlyModifierPHP81(t *testing.T) {
+	tester.NewParserPrintTestSuite(t).UsePHP8().Run(`<?php
+class Foo {
+	readonly string $a;
+	private readonly string $a;
+	private string $a;
+	private readonly $a = 100;
+
+	public function __construct(
+		readonly string $a,
+		private readonly string $a,
+		private string $a,
+		private readonly $a = 100,
+	) {}
+}
+`)
+}