Unsetting list elements should turn to an array

src/Psalm/Internal/Analyzer/StatementsAnalyzer.php

@@ -1270,6 +1270,13 @@ class StatementsAnalyzer extends SourceAnalyzer implements StatementsSource
                             $root_type->addType(
                                 new Type\Atomic\TMixed()
                             );
+                        } elseif ($atomic_root_type instanceof Type\Atomic\TList) {
+                            $root_type->addType(
+                                new Type\Atomic\TArray([
+                                    Type::getInt(),
+                                    $atomic_root_type->type_param
+                                ])
+                            );
                         }
                     }
 

tests/ArrayAccessTest.php

@@ -953,6 +953,19 @@ class ArrayAccessTest extends TestCase
                     $array[$a] = "b";',
                 'error_message' => 'UndefinedGlobalVariable',
             ],
+            'unsetListElementShouldChangeToArray' => [
+                '<?php
+                    /**
+                     * @param list<string> $arr
+                     * @return list<string>
+                     */
+                    function takesList(array $arr) : array {
+                        unset($arr[0]);
+
+                        return $arr;
+                    }',
+                'error_message' => 'LessSpecificReturnStatement',
+            ],
         ];
     }
 }