From dca758da83e2394c000f58b117f62a77116536d1 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Maximilian=20Kr=C3=B6g?= <maxi_kroeg@web.de>
Date: Sun, 10 Nov 2024 18:18:09 +0100
Subject: [PATCH] Fix array_reverse type for  etc.

---
 .../ArrayReverseReturnTypeProvider.php        | 50 +++++++++++++++----
 1 file changed, 40 insertions(+), 10 deletions(-)

diff --git a/src/Psalm/Internal/Provider/ReturnTypeProvider/ArrayReverseReturnTypeProvider.php b/src/Psalm/Internal/Provider/ReturnTypeProvider/ArrayReverseReturnTypeProvider.php
index 8d20cd11b57..0bbbfbe00f9 100644
--- a/src/Psalm/Internal/Provider/ReturnTypeProvider/ArrayReverseReturnTypeProvider.php
+++ b/src/Psalm/Internal/Provider/ReturnTypeProvider/ArrayReverseReturnTypeProvider.php
@@ -3,6 +3,7 @@
 namespace Psalm\Internal\Provider\ReturnTypeProvider;
 
 use Psalm\Internal\Analyzer\StatementsAnalyzer;
+use Psalm\Internal\Type\TypeCombiner;
 use Psalm\Plugin\EventHandler\Event\FunctionReturnTypeProviderEvent;
 use Psalm\Plugin\EventHandler\FunctionReturnTypeProviderInterface;
 use Psalm\Type;
@@ -11,6 +12,8 @@
 use Psalm\Type\Union;
 
 use function array_reverse;
+use function array_values;
+use function count;
 
 /**
  * @internal
@@ -57,17 +60,44 @@ public static function getFunctionReturnType(FunctionReturnTypeProviderEvent $ev
         if ($first_arg_array->is_list) {
             $second_arg = $call_args[1]->value ?? null;
 
-            if (!$second_arg
-                || (($second_arg_type = $statements_source->node_data->getType($second_arg))
-                    && $second_arg_type->isFalse()
-                )
-            ) {
-                return $first_arg_array->fallback_params
-                    ? ($first_arg_array->isNonEmpty()
+            $preserve_keys =
+                $second_arg &&
+                !(($second_arg_type = $statements_source->node_data->getType($second_arg)) &&
+                $second_arg_type->isFalse());
+            if (!$preserve_keys) {
+                if ($first_arg_array->fallback_params) {
+                    return $first_arg_array->isNonEmpty()
                         ? Type::getNonEmptyList($first_arg_array->getGenericValueType())
-                        : Type::getList($first_arg_array->getGenericValueType())
-                    )
-                    : new Union([$first_arg_array->setProperties(array_reverse($first_arg_array->properties))]);
+                        : Type::getList($first_arg_array->getGenericValueType());
+                }
+
+                $reversed_array_items = [];
+                $num_undefined = 0;
+                $i = 0;
+                foreach (array_reverse($first_arg_array->properties) as $array_item_type) {
+                    $reversed_array_items[] = $array_item_type;
+                    /** @var int<0,max> $j */
+                    $j = $i - $num_undefined;
+                    for (; $j < $i; ++$j) {
+                        $reversed_array_items[$j] = TypeCombiner::combine([
+                            ...array_values($reversed_array_items[$j]->getAtomicTypes()),
+                            ...array_values($array_item_type->getAtomicTypes()),
+                        ]);
+                    }
+                    if ($array_item_type->possibly_undefined) {
+                        ++$num_undefined;
+                    }
+                    ++$i;
+                }
+
+                $max_len = count($reversed_array_items);
+                /** @var int<0,max> $i */
+                $i = $max_len - $num_undefined;
+                for (; $i < $max_len; ++$i) {
+                    $reversed_array_items[$i] = $reversed_array_items[$i]->setPossiblyUndefined(true);
+                }
+
+                return new Union([$first_arg_array->setProperties($reversed_array_items)]);
             }
 
             return new Union([new TKeyedArray(