Repository: FriendsOfPHP/PHP-CS-Fixer (php)

Issue:
`return_assignment` can break functions that return by reference
## Bug report

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When using the [`return_assignment`](https://github.com/FriendsOfPHP/PHP-CS-Fixer/blob/master/doc/rules/return_notation/return_assignment.rst) rule, it has an adverse effect if the function [returns by reference](https://www.php.net/manual/en/language.references.return.php).

Functions that return by reference must return a variable, but the `return_assignment` rule can rewrite function bodies that PHP throws an exception on.

This rule should avoid functions that return by reference.

```
vendor/bin/php-cs-fixer -V
PHP CS Fixer 3.8.0 BerSzcz against war! by Fabien Potencier and Dariusz Ruminski.
PHP runtime: 8.1.5
```

### Code snippet that reproduces the problem

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  also provide the expected output, the actual output and/or the error that
  occurred, if any.

  Please use markdown syntax for each code snippet, e.g.:

  ```php
  <?php
  $var = 'foo';
  ```
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```php

class Example
{
    protected $myData;

    public function fallback()
    {
        return 'fallback';
    }

    public function &example($name)
    {
        if ($name == 'data') {
            $this->myData = 'something';

            return $this->myData;
        }

        $value = $this->fallback();

        return $value;
    }
}
```

With `return_assignment` enabled, the code gets condensed to:

```php

class Example
{
    protected $myData;

    public function fallback()
    {
        return 'fallback';
    }

    public function &example($name)
    {
        if ($name == 'data') {
            $this->myData = 'something';

            return $this->myData;
        }

        return $this->fallback();
    }
}
```

But that's problematic, because PHP complains:
> Only variable references should be returned by reference

Pull request description:
bug: Prevent breaking functions returning by reference
Fixes #6482.

Patch:
diff --git a/src/Fixer/ReturnNotation/ReturnAssignmentFixer.php b/src/Fixer/ReturnNotation/ReturnAssignmentFixer.php
index b4a673b01..844606e3d 100644
--- a/src/Fixer/ReturnNotation/ReturnAssignmentFixer.php
+++ b/src/Fixer/ReturnNotation/ReturnAssignmentFixer.php
@@ -73,6 +73,11 @@ protected function applyFix(\SplFileInfo $file, Tokens $tokens): void
                 continue;
             }
 
+            $next = $tokens->getNextMeaningfulToken($index);
+            if ($tokens[$next]->isGivenKind(CT::T_RETURN_REF)) {
+                continue;
+            }
+
             $functionOpenIndex = $tokens->getNextTokenOfKind($index, ['{', ';']);
             if ($tokens[$functionOpenIndex]->equals(';')) { // abstract function
                 $index = $functionOpenIndex - 1;


Test patch:
diff --git a/tests/Fixer/ReturnNotation/ReturnAssignmentFixerTest.php b/tests/Fixer/ReturnNotation/ReturnAssignmentFixerTest.php
index ad9e9e4cc..315dc251b 100644
--- a/tests/Fixer/ReturnNotation/ReturnAssignmentFixerTest.php
+++ b/tests/Fixer/ReturnNotation/ReturnAssignmentFixerTest.php
@@ -785,6 +785,22 @@ public function __destruct()
 var_dump($a); // $a = 2 here _╯°□°╯︵┻━┻
 ',
             ],
+            'variable returned by reference in function' => [
+                '<?php
+                function &foo() {
+                    $var = 1;
+                    return $var;
+                }',
+            ],
+            'variable returned by reference in method' => [
+                '<?php
+                class Foo {
+                    public function &bar() {
+                        $var = 1;
+                        return $var;
+                    }
+                }',
+            ],
         ];
     }