/** @return static */ doesn't work properly with extended abstract class

[melya]

Bug report

PHP Version: 7.4

Somehow /** @return static */ doesn't work properly in provided code snippet with extra abstract class.
However it works in simpler use-case like https://phpstan.org/r/18000821-8803-43f6-b17b-abd1d49c6cce

Code snippet that reproduces the problem

https://phpstan.org/r/771ab3d4-54fb-4552-8c4e-9ac0633e457c

<?php

declare(strict_types=1);

abstract class ClassC
{
    private string $value;
    
    private function __construct(string $value)
    {
        $this->value = $value;
    }
    
    /** @return static */
    public static function fromString(string $value): self
    {
        return new static($value);
    }
}

final class ClassB extends ClassC
{
}

final class ClassA
{
    public function classB(): ClassB
    {
        return ClassB::fromString("any");
    }
}

Expected output

ClassB::fromString("any") should not generate an error "Unsafe usage of new static()."

[ondrejmirtes]

If you run this example locally you get:

And the linked blogpost explains why you see this error and what you should do: https://phpstan.org/blog/solving-phpstan-error-unsafe-usage-of-new-static

[melya]

Agree.
Sorry, I've prepared not a full example of my use-case.
Below is the correct one.

Please, take a look if that is the bug or we should always define return static in such cases ?
https://phpstan.org/r/fc9004dd-20d2-4ecb-a3e2-7cb9b59161f5

<?php

declare(strict_types=1);

interface TheInterface
{
	/** @return static */
	public static function fromString(string $value);
}

abstract class ClassC implements TheInterface
{
    private string $value;
    
    final private function __construct(string $value)
    {
        $this->value = $value;
    }
    
    // HERE: not defined "@return static" annotation leads to an error. 
    final public static function fromString(string $value): self
    {
        return new static($value);
    }
}

final class ClassB extends ClassC
{
}

final class ClassA
{
    public function classB(): ClassB
    {
        return ClassB::fromString("any");
    }
}

[ondrejmirtes]

Yeah, the implicit PHPDoc inheritance should probably work in this case. Until it's fixed, please use the explicit /** @return static */ in ClassC as well.

[mvorisek]

I belive this should be closed - when : self is defined, phpstan error is correct as another class of extending abstract class can be returned

[phpstan-bot]

@melya After the latest commit in dev-master, PHPStan now reports different result with your code snippet:

@@ @@
-No errors
+7: Property ClassB::$value is never read, only written.

Full report

Line	Error
7	Property ClassB::$value is never read, only written.

[phpstan-bot]

@melya After the latest commit in dev-master, PHPStan now reports different result with your code snippet:

@@ @@
+ 7: Property ClassC::$value is never read, only written.
 17: Unsafe usage of new static().

Full report

Line	Error
7	Property ClassC::$value is never read, only written.
17	Unsafe usage of new static().

[phpstan-bot]

@melya After the latest commit in dev-master, PHPStan now reports different result with your code snippet:

@@ @@
+13: Property ClassC::$value is never read, only written.
 34: Method ClassA::classB() should return ClassB but returns ClassC.

Full report

Line	Error
13	Property ClassC::$value is never read, only written.
34	Method ClassA::classB() should return ClassB but returns ClassC.

[phpstan-bot]

@melya After the latest commit in dev-master, PHPStan now reports different result with your code snippet:

@@ @@
-No errors
+7: Property ClassB::$value is never read, only written.

Full report

Line	Error
7	Property ClassB::$value is never read, only written.

[phpstan-bot]

@melya After the latest commit in dev-master, PHPStan now reports different result with your code snippet:

@@ @@
+ 7: Property ClassC::$value is never read, only written.
 17: Unsafe usage of new static().

Full report

Line	Error
7	Property ClassC::$value is never read, only written.
17	Unsafe usage of new static().

[phpstan-bot]

@melya After the latest commit in dev-master, PHPStan now reports different result with your code snippet:

@@ @@
+13: Property ClassC::$value is never read, only written.
 34: Method ClassA::classB() should return ClassB but returns ClassC.

Full report

Line	Error
13	Property ClassC::$value is never read, only written.
34	Method ClassA::classB() should return ClassB but returns ClassC.

[phpstan-bot]

@melya After the latest commit in dev-master, PHPStan now reports different result with your code snippet:

@@ @@
-17: Unsafe usage of new static().
+17: Unsafe usage of new static().
+ 7: Property ClassC::$value is never read, only written.

Full report

Line	Error
17	Unsafe usage of new static().
7	Property ClassC::$value is never read, only written.

[phpstan-bot]

@melya After the latest commit in 1.8.x, PHPStan now reports different result with your code snippet:

@@ @@
+PHP 8.0 (3 errors)
+==========
+
+13: Property ClassC::$value is never read, only written.
+15: Private method ClassC::__construct() cannot be final as it is never overridden by other classes.
+34: Method ClassA::classB() should return ClassB but returns ClassC.
+
+PHP 7.1 – 7.4 (2 errors)
+==========
+
+13: Property ClassC::$value is never read, only written.
 34: Method ClassA::classB() should return ClassB but returns ClassC.

Full report

PHP 8.0 (3 errors)

Line	Error
13	Property ClassC::$value is never read, only written.
15	Private method ClassC::__construct() cannot be final as it is never overridden by other classes.
34	Method ClassA::classB() should return ClassB but returns ClassC.

PHP 7.1 – 7.4 (2 errors)

Line	Error
13	Property ClassC::$value is never read, only written.
34	Method ClassA::classB() should return ClassB but returns ClassC.

[luxemate]

@ondrejmirtes I'm not sure if it's related or should I create another issue, but static type hint also works strange with final classes.

<?php declare(strict_types = 1);

class HelloWorld
{
	/** @return static */
	public function sayHello(): self
	{
		return new self();
	}
}

https://phpstan.org/r/a6e4516b-4a9b-4d60-83d5-6392aad8f8cd Here without final it shows an error Method HelloWorld::sayHello() should return static(HelloWorld) but returns HelloWorld..

https://phpstan.org/r/c3800156-3cbd-4817-83db-4a9b1dcd3d01 But here with final it's all fine, although return types differ and final + static makes little sense.

[ondrejmirtes]

@luxemate Please do not hijack unrelated bug reports with your own issue. Open a discussion instead, thanks.

[luxemate]

@ondrejmirtes No problem. I just thought it is related because it pretty much looks so. :)

[ondrejmirtes]

Fixed: phpstan/phpstan-src#2803

[github-actions]

This thread has been automatically locked since there has not been any recent activity after it was closed. Please open a new issue for related bugs.