pureMethod.void

Code example

<?php declare(strict_types = 1);

class Foo
{
	/** @phpstan-pure */
	public function doNothing(): void
	{
	}
}

Why is it reported?

A method marked as @phpstan-pure must not have side effects and must return a meaningful value. A pure method that returns void serves no purpose -- since it has no side effects and produces no return value, calling it has no observable effect. This is almost certainly a mistake: either the method should not be marked as pure, or it should return a value.

The exception is constructors, which are allowed to be pure and return void because their purpose is to initialize an object.

How to fix it

If the method performs side effects, remove the @phpstan-pure annotation:

 class Foo
 {
-	/** @phpstan-pure */
 	public function doSomething(): void
 	{
 		file_put_contents('/tmp/log.txt', 'done');
 	}
 }

If the method truly is pure, it should return a value:

 class Foo
 {
 	/** @phpstan-pure */
-	public function compute(): void
+	public function compute(): int
 	{
+		return 42;
 	}
 }