code completion and factory pattern in eclipse pdt
Short answer, this is not possible in the way you want it.
As you've already rightfully pointed out in another comment you should use @var manually to achieve code completion goodness, because it's impossible for the editor to understand the concept of programming patterns by itself
Although theoretically possible, manually authoring rules for type inference just seems backwards imho (let alone the required changes to the Docblock notation itself).
The only IDE that supports this is PHPStorm (via a .phpstorm.meta.php file).
I filed a feature request asking to support this.You can vote for it at https://bugs.eclipse.org/bugs/show_bug.cgi?id=463110
i use eclipse and pdt from almost 3+ years,but dont have perfect answer for your question
i think Zend Studio 9 can solve your problem,for code completion it is far more better than pdt.