Hello!

This adds failings tests for phpstan/phpstan#12585.

Please note that there's actually two bugs here:

1. Return type

I'm getting errors of the form:

Post::query()->whereHas('user', fn ($q) => $q->where('name', 'test'));
// Anonymous function should return Bug12585\Builder<Bug12585\Model> but returns Bug12585\Builder<Bug12585\User>

despite the parent method having (\Closure(Builder<TRelatedModel>): mixed)|null as the $callback type; and the MethodParameterClosureTypeExtension specifying MixedType as the return type for the replaced closure type.

It seems like the parameter type of the closure phpdoc is being used as the return type...

2. Parameter Type

I am getting errors of the form:

User::query()->whereHas('posts', fn (PostBuilder $q) => $q->where('name', 'test'));
// Parameter #2 $callback of method Bug12585\Builder<Bug12585\User>::whereHas() expects (Closure(Bug12585\Builder<Bug12585\Post>): mixed)|null, 
// Closure(Bug12585\PostBuilder): Bug12585\PostBuilder given.

I think that the MethodParameterClosureTypeExtension is only used to resolve the closure type inside the closure, while the PHPDoc is being used when checking method calls.

Thanks!