Error Identifier: staticMethod.alreadyNarrowedType

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 TypeChecker
{
	/**
	 * @phpstan-assert int $value
	 */
	public static function assertInt(mixed $value): void
	{
	}
}

function doFoo(int $value): void
{
	TypeChecker::assertInt($value);
}

Why is it reported? #

A static method call that performs a type check (such as an assertion) will always evaluate to true because the argument is already known to be of the asserted type. The check is redundant – the type has already been narrowed before the call.

This indicates either unnecessary code, or a logic error where a different variable was intended.

How to fix it #

Remove the redundant type check if the type is already guaranteed:

 function doFoo(int $value): void
 {
-	TypeChecker::assertInt($value);
 	// $value is already int
 }

Or check a different variable that actually needs the assertion:

-function doFoo(int $value): void
+function doFoo(mixed $value): void
 {
 	TypeChecker::assertInt($value);
 }

If the static method call is the last condition in a series of conditions, and the tip Remove remaining cases below this one and this error will disappear too. is shown, consider restructuring the conditional logic.

How to ignore this error #

You can use the identifier staticMethod.alreadyNarrowedType to ignore this error using a comment:

// @phpstan-ignore staticMethod.alreadyNarrowedType
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: staticMethod.alreadyNarrowedType

Rules that report this error #

PHPStan\Rules\Comparison\ImpossibleCheckTypeStaticMethodCallRule [1]

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