Add support for downgrading return type null

[RikudouSage]

Feature Request

PHP 8.2 allows null to be used as a standalone return type.

Diff

Use case 1, without parent:

<?php

class WithoutParent
{
+    /**
+     * @return null
+     */
-    public function getSomething(): null
+    public function getSomething(): mixed
    {
    }
}

Use case 2, with a parent:

<?php

class ParentClass
{
    public function getSomeString(): ?string
    {
    }
}

class ChildClass extends ParentClass
{
+    /**
+     * @return null
+     */
-    public function getSomeString(): null
+    public function getSomeString(): ?string
    {
    }
}

[TomasVotruba]

Hi, thanks for proposal. We actually don't support docblock-based types since Rector 0.15 https://getrector.com/blog/new-in-rector-015-complete-safe-and-known-type-declarations as it lead to false positive and breaking code in the past.

We infer return/param/property type declarations from the code itself instead as the only safe way.

Use the TYPE_DECLARATIONS set instead 👍

[RikudouSage]

How does that help? This is a downgrade rector that downgrades unsupported features from php 8.2. Meaning if someone imports the downgrade set, it should downgrade everything it can to supported syntax.

[TomasVotruba]

Ah, I confused the change other way around, my bad.

That would be great addition. Could you open up PR?

[TomasVotruba]

@samsonasik Could you add this rule to the PHP 8.2 set?

[samsonasik]

I will try

[samsonasik]

I created PR:

• [Downgradephp82] Add DowngradeStandaloneNullTrueFalseReturnTypeRector rector-downgrade-php#208

for it.