<?php
#[\Attribute(\Attribute::TARGET_PROPERTY)]
class Hello {
    public function __construct(
        public ?Closure $world = null,
    ) {
    }
}

class Foo {
    /**
     * @var string
     */
    #[Hello(static function() {
        return null;
    })]
    public $bar;
}

$reflectionProperty = new ReflectionProperty(Foo::class, 'bar');

var_dump($reflectionProperty->getDocComment());