instanceof.deprecatedTrait

Code example

<?php declare(strict_types = 1);

/** @deprecated Use NewHelperInterface instead */
trait OldHelperTrait
{
	public function help(): void {}
}

function doFoo(object $obj): void
{
	if ($obj instanceof OldHelperTrait) { // ERROR: Instanceof references deprecated trait OldHelperTrait.
		// ...
	}
}

Why is it reported?

This error is reported by phpstan/phpstan-deprecation-rules.

The instanceof check references a trait that has been marked with the @deprecated PHPDoc tag. Deprecated traits are scheduled for removal or replacement, and any usage -- including in instanceof checks -- should be migrated to the recommended alternative. Additionally, instanceof checks against traits always evaluate to false at runtime because PHP does not support trait-based type checks.

How to fix it

Replace the deprecated trait with the recommended replacement type in the instanceof check:

 <?php declare(strict_types = 1);

 function doFoo(object $obj): void
 {
-	if ($obj instanceof OldHelperTrait) {
+	if ($obj instanceof NewHelperInterface) {
 		// ...
 	}
 }