PHPStorm plugin for custom autocomplete (Updated)

Hi.
I'm trying to develop PHPStrom plugin for Scalar Objects PHP extension (https://github.com/nikic/scalar_objects) so i'd be able to do something like

<?php
class StringHandler {
    public function length() {return strlen($this);}
    public function replace($search, $replace) {return str_replace($search, $replace, $this);}
}

register_primitive_type_handler('string', 'StringHandler');

$string = "test string";

and get autocompletion for

echo $string->replace("test ", "")->length(); //6

I guess i need to check variable type and load all public methods from registered for this type handler (handler could be set manually in plugin settings e.g.) to autcompletion list, but i have no idea about even what to begin with due to lack of information about developing Intellij plugins and very few examples.

Any help would be appreciated.

--UPD--

Ok, i found something interestring.
If you name a class just as one of PHP scalar types, autocomplete works great for variables of this type:

Unforunately, it's impossible to create class named "array", so it's the main problem i have to solve - how to make PHPStorm look up variants for autocomplete in custom class at least for array type variables.

Message was edited by: Dmitry Avdonkin