Support @phpstan-require-extends and calls of methods of this class

[momala454]

Feature description or problem with existing feature
@phpstan-require-extends on a trait force the trait to be used on a specific class.
When I call a method of that specific class on the trait, intelephense does not know the references.
Phpstan even know the references to this method even without @phpstan-require-extends

/** @phpstan-require-extends HelloWorld */
trait Hello
{
    public function world(): void
    {
        $a = $this->hi(); // $a is mixed instead of int, "hi" is unknown to intelephense
    }
}

class HelloWorld
{
    use Hello;

// here 0 references instead of 1
    public function hi(): int
    {
        return 1;
    }
}

Describe the solution you'd like
It could be cool for intelephense to know the references to the calls of "hi". It could use @phpstan-require-extends if that help to find it

[bmewburn]

I think it can be improved without the annotation by looking up the trait usages. Though I'd rather have calls like this show an error with a quick fix to declare a property or an abstract method on the trait itself.

[momala454]

The code does not require à Quick fix as is, it will not générate an error when executed

[ili101]

Note that adding mixin enables intellisense/autocompletion on "HelloWorld" content inside "Hello"

/**
 * @mixin HelloWorld
 */

But adding phpstan-require-extends does not

/**
 * @phpstan-require-extends HelloWorld
 */

So Intelephense probably just needs to treat phpstan-require-extends the same as mixin.
A workaround is to add mixin in addition to phpstan-require-extends.