Missing visibility check for private abstract trait methods

Description

The following code:

<?php

trait T {
    public abstract function test();
}

class P {
    private function test() {}
}

class C extends P {
    use T;
}

This passes without errors. There's an intentional BC layer that skips visibility checks for abstract trait methods (see Zend/tests/traits/abstract_method_4.phpt). However, this should not include private parent methods, because the trait cannot call those. The whole BC layer is questionable today, so it might be better to remove it entirely.

PHP Version

All supported branches

Operating System

No response

复现该示例并阅读 Zend/tests/traits/abstract_method_4.phpt，该文件记录了抽象 trait 方法现有的 BC 行为。跟踪针对私有父类方法的可见性检查路径，然后添加或调整回归测试，使预期行为明确，并使相关的受支持分支通过。