From e822ec7541398c8f3895d11520120071fd31536a Mon Sep 17 00:00:00 2001
From: Brown <github@muglug.com>
Date: Wed, 9 Oct 2019 12:49:31 -0400
Subject: [PATCH] Unsetting list elements should turn to an array

---
 src/Psalm/Internal/Analyzer/StatementsAnalyzer.php |  7 +++++++
 tests/ArrayAccessTest.php                          | 13 +++++++++++++
 2 files changed, 20 insertions(+)

diff --git a/src/Psalm/Internal/Analyzer/StatementsAnalyzer.php b/src/Psalm/Internal/Analyzer/StatementsAnalyzer.php
index 4522b5bec..0591bf653 100644
--- a/src/Psalm/Internal/Analyzer/StatementsAnalyzer.php
+++ b/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
+                                ])
+                            );
                         }
                     }
 
diff --git a/tests/ArrayAccessTest.php b/tests/ArrayAccessTest.php
index db15f41b7..433d3ea0b 100644
--- a/tests/ArrayAccessTest.php
+++ b/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',
+            ],
         ];
     }
 }