Error Identifier: return.internalTrait

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;

// Defined in a third-party package:
// /** @internal */
// trait InternalTrait {}

use ThirdParty\InternalTrait;

function createObject(): InternalTrait
{
    // ...
}

Why is it reported? #

The return type of the function or method references a trait that is marked as @internal. Internal symbols are not meant to be used outside the package or namespace that defines them. Referencing an internal trait in a return type exposes an internal implementation detail in a public API, creating a dependency on something that may change without notice.

How to fix it #

Replace the internal trait with a public interface or class in the return type:

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

-use ThirdParty\InternalTrait;
+use ThirdParty\PublicInterface;

-function createObject(): InternalTrait
+function createObject(): PublicInterface
 {
     // ...
 }

If the trait is internal to the same package, the error will not be reported. The @internal restriction only applies to cross-package usage.

How to ignore this error #

You can use the identifier return.internalTrait to ignore this error using a comment:

// @phpstan-ignore return.internalTrait
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: return.internalTrait

Rules that report this error #

PHPStan\Rules\InternalTag\RestrictedInternalClassNameUsageExtension [1]

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