- [X] [[ https://wiki.php.net/rfc/void_return_type | `Void` typehint ]]
- [X] [[ https://wiki.php.net/rfc/iterable | `Iterable` typehint ]] [ D6644 ]
- [X] [[ https://wiki.php.net/rfc/iterable | Add `is_iterable()` internal function ]]
- [X] [[ https://wiki.php.net/rfc/nullable_types | Nullable typehints ]] [ D6342 ]
- [X] [[ https://wiki.php.net/rfc/negative-string-offsets | Negative string offsets ]]
- [ ] [[ https://wiki.php.net/rfc/list_keys | Allow specifying keys in `list()` ]]
- [ ] [[ https://wiki.php.net/rfc/short_list_syntax | Short `list()` syntax ]]
- [X] [[ https://wiki.php.net/rfc/closurefromcallable | Closure from callable function ]]
NOTE: Firstly implement closures object extension [ T6817 ]
- [ ] [[ https://wiki.php.net/rfc/class_const_visibility | Support Class Constant Visibility ]]
- [ ] [[ https://wiki.php.net/rfc/multiple-catch | Catching Multiple Exception Types ]]