in return type class with __invoke method is not a callable

Description

The following code:

<?php
interface I {
    public function test(): callable;
}
class Invokable {
    public function __invoke() {}
}
var_dump(is_callable(new Invokable()));
class C implements I {
    public function test(): Invokable {}
}

Resulted in this output:

bool(true)

Fatal error: Declaration of C::test(): Invokable must be compatible with I::test(): callable in /in/PfBWX on line 10

Process exited with code 255.

Methods should be able to restrict callable return types from interfaces and parent classes to more specific types that unconditionally fall within the callable type. Any class or interface that contains an __invoke method should be considered a callable type an be allowed as a more specific subtype of callable in subclasses. Also \Closure should be allowed as well.

PHP Version

8.4.5

Operating System

No response

首先运行 issue 中的 PHP reproducer，并检查返回类型兼容性如何处理 callable 类型和类类型。当带有 __invoke 的类和 Closure 可以作为 callable 声明的更窄返回类型被接受，并且兼容性测试覆盖报告的案例时，该 issue 即完成。