Implement values as complement to annotations

[thekid]

See xp-framework/rfc#336, values are key/value pairs that can be attached to types and type members. They serve as a complement to PHP 8 attributes which do not support arbitrary expressions in their argument lists.

Example

use unittest\{Assert, Test, Values};

class ListOfTest {

  #$values: [[new ListOf()], [ListOf::$EMPTY]]
  #[Test, Values(using: '$values')]
  public function size_of_empty($list) {
    Assert::equals(0, $list->size());
  }
}

Note: Accessing values needs to be implemented by libraries, no automatic coupling of the Values attributes and the $values value is done!

[thekid]

Decided against this in favor of eval named argument