[php-src] Issue #19178: Callable not considered contravariant with Closure

Issue: https://github.com/php/php-src/issues/19178 Author: Crell ### Description The following code: ```php <?php class Test { public private(set) \Closure $action { set (callable $value) { if (!$value instanceof \Closure) { $value = $value(...); } $this->action = $value; } } } ``` Resulted in this output: ``` Fatal error: Type of parameter $value of hook Test::$action::set must be compatible with property type ``` But I expected this output instead: ``` I expected no error. ``` As far as I am aware, callable includes \Closure. You can pass a Closure to a callable. So I would expect this to work. However, it gets rejected. Specifying set(\Closure|callable) { ... } is a workaround. It seems like either the variance detection is buggy or the definition of callable is wonkier than I thought. ### PHP Version ```plain PHP 8.4.8 (cli) (built: Jun 9 2025 13:49:53) (NTS) Copyright (c) The PHP Group Zend Engine v4.4.8, Copyright (c) Zend Technologies with Zend OPcache v8.4.8, Copyright (c), by Zend Technologies with Xdebug v3.4.0, Copyright (c) 2002-2024, by Derick Rethans (Though 3v4l confirms this error on all 8.4 releases.) ``` ### Operating System _No response_