Error Identifier: interface.extendsInternalTrait

Every error reported by PHPStan has an error identifier. Here’s a list of all error identifiers. In PHPStan Pro you can see the error identifier next to each error and filter errors by their identifiers.

Code example #

<?php declare(strict_types = 1);

namespace App;

use Some\Internal\HelperTrait;

interface MyInterface extends HelperTrait // ERROR: Interface MyInterface extends internal trait HelperTrait.
{
}

Why is it reported? #

The interface declaration attempts to extend a trait that is marked as @internal. This is problematic for two reasons: first, interfaces cannot extend traits in PHP (this is a language-level error), and second, the trait is internal to its package and not meant to be referenced outside of it. Internal types may change without notice in future versions.

How to fix it #

Interfaces can only extend other interfaces. Replace the trait reference with the correct interface:

 <?php declare(strict_types = 1);
 
 namespace App;

-use Some\Internal\HelperTrait;
+use Some\PublicInterface;

-interface MyInterface extends HelperTrait
+interface MyInterface extends PublicInterface
 {
 }

If you need the functionality provided by the trait, define the methods directly in the interface and have implementing classes use the trait separately.

How to ignore this error #

You can use the identifier interface.extendsInternalTrait to ignore this error using a comment:

// @phpstan-ignore interface.extendsInternalTrait
codeThatProducesTheError();

You can also use only the identifier key to ignore all errors of the same type in your configuration file in the ignoreErrors parameter:

parameters:
	ignoreErrors:
		-
			identifier: interface.extendsInternalTrait

Rules that report this error #

PHPStan\Rules\InternalTag\RestrictedInternalClassNameUsageExtension [1]

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