Error Identifier: parameterByRef.nestedUnusedType

← Back to parameterByRef.*

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);

class Foo
{
	/**
	 * @param array<int|string> &$items
	 */
	public function process(array &$items): void
	{
		$items = [1, 2, 3];
	}
}

Why is it reported? #

The declared type of a by-reference parameter is wider than necessary in a nested part. PHPStan analyzed all code paths and determined that a narrower type would be more precise, because some union members in the nested type are never actually assigned to the parameter.

In the example above, the parameter type declares array<int|string>, but the function only ever assigns int values. The string part of the nested union is unused and the type could be narrowed to array<int>.

How to fix it #

Narrow the parameter type to match what the function actually assigns:

 class Foo
 {
 	/**
-	 * @param array<int|string> &$items
+	 * @param array<int> &$items
 	 */
 	public function process(array &$items): void
 	{
 		$items = [1, 2, 3];
 	}
 }

How to ignore this error #

You can use the identifier parameterByRef.nestedUnusedType to ignore this error using a comment:

// @phpstan-ignore parameterByRef.nestedUnusedType
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: parameterByRef.nestedUnusedType

Rules that report this error #

• PHPStan\Rules\TooWideTypehints\TooWideArrowFunctionReturnTypehintRule [1]
• PHPStan\Rules\TooWideTypehints\TooWideClosureReturnTypehintRule [1]
• PHPStan\Rules\TooWideTypehints\TooWideFunctionParameterOutTypeRule [1]
• PHPStan\Rules\TooWideTypehints\TooWideFunctionReturnTypehintRule [1]
• PHPStan\Rules\TooWideTypehints\TooWideMethodParameterOutTypeRule [1]
• PHPStan\Rules\TooWideTypehints\TooWideMethodReturnTypehintRule [1]
• PHPStan\Rules\TooWideTypehints\TooWidePropertyTypeRule [1]