generics.existingClass

Code example

<?php declare(strict_types = 1);

class Item
{
}

/**
 * @template Item
 */
class Collection
{
}

Why is it reported?

A @template tag uses a name that conflicts with an existing class. In the example above, the template type parameter is named Item, but a class with the same name already exists. This creates ambiguity because PHPStan cannot distinguish between the template type parameter and the class when the name is used in type annotations.

How to fix it

Rename the template type parameter to a name that does not conflict with any existing class:

 <?php declare(strict_types = 1);

 /**
- * @template Item
+ * @template TItem
  */
 class Collection
 {
 }

A common convention is to prefix template type names with T to avoid conflicts with existing classes.