From c50972b1585b046192418d2735ddf0d84aae8f0a Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=B6ren=20W=C3=BCnsch?= <soeren.wrede@parshipgroup.com>
Date: Tue, 1 Sep 2026 11:27:54 +0200
Subject: [PATCH] [Php85] Skip nested compound assignment in
 ArrayFirstLastRector

$array[array_key_last($array)][0] += 1 was rewritten to
array_last($array)[0] += 1. That reads the last element into a temporary and
writes to the copy, so the assignment is lost. PHP reports nothing, which makes
the change silent.

IS_ASSIGN_OP_VAR was only set on the outermost node of the assignment target,
so the rule saw the inner dim fetch as an ordinary read. Marking the whole
chain reflects what happens: $array[$key][0] += 1 writes to $array[$key] too.

The plain assignment form was already skipped through PHPStan's
Scope::isInExpressionAssign(); a fixture now covers it so that stays true.
---
 .../Fixture/skip_as_nested_assign.php.inc     | 13 +++++++++++++
 .../Fixture/skip_as_nested_assign_op.php.inc  | 13 +++++++++++++
 .../NodeVisitor/AssignedToNodeVisitor.php     | 19 ++++++++++++++++++-
 3 files changed, 44 insertions(+), 1 deletion(-)
 create mode 100644 rules-tests/Php85/Rector/ArrayDimFetch/ArrayFirstLastRector/Fixture/skip_as_nested_assign.php.inc
 create mode 100644 rules-tests/Php85/Rector/ArrayDimFetch/ArrayFirstLastRector/Fixture/skip_as_nested_assign_op.php.inc

diff --git a/rules-tests/Php85/Rector/ArrayDimFetch/ArrayFirstLastRector/Fixture/skip_as_nested_assign.php.inc b/rules-tests/Php85/Rector/ArrayDimFetch/ArrayFirstLastRector/Fixture/skip_as_nested_assign.php.inc
new file mode 100644
index 00000000000..2c5efa8170a
--- /dev/null
+++ b/rules-tests/Php85/Rector/ArrayDimFetch/ArrayFirstLastRector/Fixture/skip_as_nested_assign.php.inc
@@ -0,0 +1,13 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Rector\Tests\Php85\Rector\ArrayDimFetch\ArrayFirstLastRector\Fixture;
+
+final class SkipAsNestedAssign
+{
+    public function run(array $result, $lastInsertedId)
+    {
+        $result[\array_key_last($result)]['id'] = $lastInsertedId;
+    }
+}
diff --git a/rules-tests/Php85/Rector/ArrayDimFetch/ArrayFirstLastRector/Fixture/skip_as_nested_assign_op.php.inc b/rules-tests/Php85/Rector/ArrayDimFetch/ArrayFirstLastRector/Fixture/skip_as_nested_assign_op.php.inc
new file mode 100644
index 00000000000..cd272c7ce13
--- /dev/null
+++ b/rules-tests/Php85/Rector/ArrayDimFetch/ArrayFirstLastRector/Fixture/skip_as_nested_assign_op.php.inc
@@ -0,0 +1,13 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Rector\Tests\Php85\Rector\ArrayDimFetch\ArrayFirstLastRector\Fixture;
+
+final class SkipAsNestedAssignOp
+{
+    public function run(array $result, $lastInsertedId)
+    {
+        $result[\array_key_last($result)][0] += $lastInsertedId;
+    }
+}
diff --git a/src/PhpParser/NodeVisitor/AssignedToNodeVisitor.php b/src/PhpParser/NodeVisitor/AssignedToNodeVisitor.php
index 45347398457..55cd002673c 100644
--- a/src/PhpParser/NodeVisitor/AssignedToNodeVisitor.php
+++ b/src/PhpParser/NodeVisitor/AssignedToNodeVisitor.php
@@ -6,6 +6,8 @@
 
 use PhpParser\Node;
 use PhpParser\Node\ArrayItem;
+use PhpParser\Node\Expr;
+use PhpParser\Node\Expr\ArrayDimFetch;
 use PhpParser\Node\Expr\Assign;
 use PhpParser\Node\Expr\AssignOp;
 use PhpParser\Node\Expr\AssignRef;
@@ -22,7 +24,7 @@ final class AssignedToNodeVisitor extends NodeVisitorAbstract implements Decorat
     public function enterNode(Node $node): ?Node
     {
         if ($node instanceof AssignOp) {
-            $node->var->setAttribute(AttributeKey::IS_ASSIGN_OP_VAR, true);
+            $this->markAssignOpVar($node->var);
             return null;
         }
 
@@ -54,4 +56,19 @@ public function enterNode(Node $node): ?Node
 
         return null;
     }
+
+    /**
+     * Marks the whole dim fetch chain, not just the outermost node: $array[$key][0] += 1 writes
+     * to $array[$key] as well, so a rule that rewrites the inner fetch would change a write
+     * into a read of a temporary value.
+     */
+    private function markAssignOpVar(Expr $expr): void
+    {
+        $expr->setAttribute(AttributeKey::IS_ASSIGN_OP_VAR, true);
+
+        while ($expr instanceof ArrayDimFetch) {
+            $expr = $expr->var;
+            $expr->setAttribute(AttributeKey::IS_ASSIGN_OP_VAR, true);
+        }
+    }
 }