Error Identifier: selfOut.unresolvableType

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);

/**
 * @template T
 */
class Collection
{
	/**
	 * @phpstan-self-out self<int&string>
	 */
	public function filterIntegers(): void
	{
	}
}

Why is it reported? #

The @phpstan-self-out PHPDoc tag contains a type that cannot be resolved. This typically happens when the type includes an impossible intersection (such as int&string, which no value can ever satisfy), references an undefined class, or uses invalid type syntax.

The @phpstan-self-out tag is used to narrow the type of $this after a method call. If the type is unresolvable, PHPStan cannot determine the resulting type of the object.

In the example above, self<int&string> contains the impossible intersection int&string, making the entire type unresolvable.

How to fix it #

Use a valid, resolvable type in the @phpstan-self-out tag:

 /**
- * @phpstan-self-out self<int&string>
+ * @phpstan-self-out self<int>
  */
 public function filterIntegers(): void
 {
 }

How to ignore this error #

You can use the identifier selfOut.unresolvableType to ignore this error using a comment:

// @phpstan-ignore selfOut.unresolvableType
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: selfOut.unresolvableType

Rules that report this error #

PHPStan\Rules\PhpDoc\IncompatibleSelfOutTypeRule [1]

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