[DeadCode] Skip used by use by ref closure on assign on RemoveUnusedVariableAssignRector (#7398)

Author: samsonasik

rules-tests/DeadCode/Rector/Assign/RemoveUnusedVariableAssignRector/Fixture/skip_used_by_use_by_ref_closure.php.inc

@@ -0,0 +1,16 @@
+<?php
+
+namespace Rector\Tests\DeadCode\Rector\Assign\RemoveUnusedVariableAssignRector\Fixture;
+
+function skipUsedByUseByRefClosure(Throwable $signalingException)
+{
+    $prevErrorHandler = set_error_handler(function ($type, $msg, $file, $line, $context = []) use (&$prevErrorHandler, $signalingException) {
+        if ($file === __FILE__) {
+            throw $signalingException;
+        }
+
+        return $prevErrorHandler !== null ? $prevErrorHandler($type, $msg, $file, $line, $context) : false;
+    });
+}
+
+?>

rules/DeadCode/Rector/Assign/RemoveUnusedVariableAssignRector.php

@@ -9,13 +9,16 @@
 use PhpParser\Node\Expr\Assign;
 use PhpParser\Node\Expr\AssignRef;
 use PhpParser\Node\Expr\Cast;
+use PhpParser\Node\Expr\Closure;
 use PhpParser\Node\Expr\FuncCall;
 use PhpParser\Node\Expr\Include_;
 use PhpParser\Node\Expr\Variable;
 use PhpParser\Node\Stmt;
+use PhpParser\Node\Stmt\Class_;
 use PhpParser\Node\Stmt\ClassMethod;
 use PhpParser\Node\Stmt\Expression;
 use PhpParser\Node\Stmt\Function_;
+use PhpParser\NodeVisitor;
 use Rector\DeadCode\SideEffect\SideEffectNodeDetector;
 use Rector\NodeAnalyzer\VariableAnalyzer;
 use Rector\NodeManipulator\StmtsManipulator;
@@ -180,6 +183,31 @@ private function resolvedAssignedVariablesByStmtPosition(array $stmts): array
                 continue;
             }
 
+            $this->traverseNodesWithCallable(
+                $stmt->expr->expr,
+                function (Node $subNode) use (&$refVariableNames) {
+                    if ($subNode instanceof Class_ || $subNode instanceof Function_) {
+                        return NodeVisitor::DONT_TRAVERSE_CURRENT_AND_CHILDREN;
+                    }
+
+                    if (! $subNode instanceof Closure) {
+                        return null;
+                    }
+
+                    foreach ($subNode->uses as $closureUse) {
+                        if (! $closureUse->var instanceof Variable) {
+                            continue;
+                        }
+
+                        if (! $closureUse->byRef) {
+                            continue;
+                        }
+
+                        $refVariableNames[] = (string) $this->getName($closureUse->var);
+                    }
+                }
+            );
+
             $assign = $stmt->expr;
             if (! $assign->var instanceof Variable) {
                 continue;