[CodeQuality] Skip inner function referenced as string callable in InnerFunctionToPrivateMethodRector

rules-tests/CodeQuality/Rector/Class_/InnerFunctionToPrivateMethodRector/Fixture/skip_string_callable.php.inc

@@ -0,0 +1,22 @@
+<?php
+
+namespace Rector\Tests\CodeQuality\Rector\Class_\InnerFunctionToPrivateMethodRector\Fixture;
+
+class SkipStringCallable
+{
+    public static function getOptions()
+    {
+        function sortByOrder(array $a, array $b): int
+        {
+            return strcmp((string) $a['label'], (string) $b['label']);
+        }
+
+        $options = [
+            ['value' => 'b', 'label' => 'Bravo'],
+            ['value' => 'a', 'label' => 'Alpha'],
+        ];
+
+        usort($options, 'sortByOrder');
+        return $options;
+    }
+}

rules/CodeQuality/Rector/Class_/InnerFunctionToPrivateMethodRector.php

@@ -11,6 +11,7 @@
 use PhpParser\Node\Expr\StaticCall;
 use PhpParser\Node\Expr\Variable;
 use PhpParser\Node\Name;
+use PhpParser\Node\Scalar\String_;
 use PhpParser\Node\Stmt\Class_;
 use PhpParser\Node\Stmt\ClassMethod;
 use PhpParser\Node\Stmt\Function_;
@@ -133,6 +134,11 @@ private function extractInnerFunctions(ClassMethod $classMethod, array &$existin
                 continue;
             }
 
+            // avoid breaking string callables, e.g. usort($items, 'functionName')
+            if ($this->isReferencedAsStringCallable($classMethod, $functionName)) {
+                continue;
+            }
+
             $existingMethodNames[] = $functionName;
             $innerFunctions[] = $stmt;
             unset($classMethod->stmts[$key]);
@@ -145,6 +151,24 @@ private function extractInnerFunctions(ClassMethod $classMethod, array &$existin
         return $innerFunctions;
     }
 
+    private function isReferencedAsStringCallable(ClassMethod $classMethod, string $functionName): bool
+    {
+        $isReferenced = false;
+
+        $this->traverseNodesWithCallable($classMethod->stmts ?? [], function (Node $node) use (
+            $functionName,
+            &$isReferenced
+        ): null {
+            if ($node instanceof String_ && $node->value === $functionName) {
+                $isReferenced = true;
+            }
+
+            return null;
+        });
+
+        return $isReferenced;
+    }
+
     private function createPrivateMethod(Function_ $innerFunction, bool $isStatic): ClassMethod
     {
         $flags = Modifiers::PRIVATE;