test(const): 添加类常量默认值测试用例

- 添加了类常量默认值从 self::CV 获取的测试用例
- 测试静态方法和实例方法中使用类常量作为参数默认值
- 验证了函数调用时传入不同参数的输出结果
- 修复了类常量默认值非字符串类型时的导出问题
- 确保默认值能正确转换为字符串格式进行显示

src/gen_stub.php

@@ -4930,6 +4930,9 @@ function parseFunctionLike(
 
             if ($param->default instanceof Expr\ClassConstFetch && $param->default->class->toLowerString() === "self") {
                 $defaultValue = getTranslator()->getClassConstValue($func, $name->className->name, $param->default->name->name);
+                if (!is_string($defaultValue)) {
+                    $defaultValue = var_export($defaultValue, true);
+                }
             } else {
                 $defaultValue = $param->default ? $prettyPrinter->prettyPrintExpr($param->default) : null;
             }

tests/aot/const/004.phpt

@@ -0,0 +1,33 @@
+--TEST--
+class const default value from self::CV
+--FILE--
+<?php
+class Test
+{
+    const CV = 1;
+
+    public static function aaa(int $v = self::CV): void
+    {
+        var_dump($v);
+    }
+
+    public function bbb(int $v = self::CV): void
+    {
+        var_dump($v);
+    }
+}
+
+function main(): void
+{
+    Test::aaa();
+    Test::aaa(999);
+    $t = new Test();
+    $t->bbb();
+    $t->bbb(888);
+}
+?>
+--EXPECT--
+int(1)
+int(999)
+int(1)
+int(888)