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Error Identifier: throws.notCovariantWithImplicitVoid

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 ParentClass
{
	public function process(): void
	{
	}
}

class ChildClass extends ParentClass
{
	/**
	 * @throws \RuntimeException
	 */
	public function process(): void
	{
		throw new \RuntimeException('Error.');
	}
}

Why is it reported? #

A child method declares a @throws type, but the parent method does not have a @throws PHPDoc tag. When the exceptions.implicitThrows config parameter is set to false, a missing @throws tag is treated the same as @throws void, meaning the method promises not to throw any exceptions. A child method that declares exceptions in its @throws tag violates this contract.

This rule enforces that @throws types follow the same covariance rules as other type declarations: a child method cannot throw more exception types than its parent allows.

How to fix it #

Remove the @throws tag from the child method if the parent does not allow throwing exceptions:

 <?php declare(strict_types = 1);
 
 class ChildClass extends ParentClass
 {
-	/**
-	 * @throws \RuntimeException
-	 */
 	public function process(): void
 	{
-		throw new \RuntimeException('Error.');
 	}
 }

Or add a @throws tag to the parent method to explicitly allow exceptions:

 <?php declare(strict_types = 1);
 
 class ParentClass
 {
+	/**
+	 * @throws \RuntimeException
+	 */
 	public function process(): void
 	{
 	}
 }

How to ignore this error #

You can use the identifier throws.notCovariantWithImplicitVoid to ignore this error using a comment:

// @phpstan-ignore throws.notCovariantWithImplicitVoid
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: throws.notCovariantWithImplicitVoid

Rules that report this error #

• PHPStan\Rules\Exceptions\MethodThrowTypeCovarianceRule [1]

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