From ef4afd72bca50a0aff61599d3e433c9ee64287ac Mon Sep 17 00:00:00 2001
From: Matt Brown <github@muglug.com>
Date: Wed, 13 Jan 2021 18:10:59 -0500
Subject: [PATCH] Unset should change array with keyed offsets

---
 src/Psalm/Internal/Analyzer/Statements/UnsetAnalyzer.php | 4 +++-
 src/Psalm/Type/Atomic/TKeyedArray.php                    | 4 ++--
 tests/TypeReconciliation/RedundantConditionTest.php      | 8 ++++++++
 3 files changed, 13 insertions(+), 3 deletions(-)

diff --git a/src/Psalm/Internal/Analyzer/Statements/UnsetAnalyzer.php b/src/Psalm/Internal/Analyzer/Statements/UnsetAnalyzer.php
index 7ecd878eb..d414bfe90 100644
--- a/src/Psalm/Internal/Analyzer/Statements/UnsetAnalyzer.php
+++ b/src/Psalm/Internal/Analyzer/Statements/UnsetAnalyzer.php
@@ -81,8 +81,10 @@ class UnsetAnalyzer
                                 $atomic_root_type->sealed = false;
 
                                 $root_type->addType(
-                                    $atomic_root_type->getGenericArrayType()
+                                    $atomic_root_type->getGenericArrayType(false)
                                 );
+
+                                $atomic_root_type->is_list = false;
                             }
                         } elseif ($atomic_root_type instanceof Type\Atomic\TNonEmptyArray) {
                             $root_type->addType(
diff --git a/src/Psalm/Type/Atomic/TKeyedArray.php b/src/Psalm/Type/Atomic/TKeyedArray.php
index 9424d4aab..88a40285f 100644
--- a/src/Psalm/Type/Atomic/TKeyedArray.php
+++ b/src/Psalm/Type/Atomic/TKeyedArray.php
@@ -246,7 +246,7 @@ class TKeyedArray extends \Psalm\Type\Atomic
         return $value_type;
     }
 
-    public function getGenericArrayType(): TArray
+    public function getGenericArrayType(bool $allow_non_empty = true): TArray
     {
         $key_types = [];
         $value_type = null;
@@ -285,7 +285,7 @@ class TKeyedArray extends \Psalm\Type\Atomic
 
         $value_type->possibly_undefined = false;
 
-        if ($this->previous_value_type || $has_defined_keys) {
+        if ($allow_non_empty && ($this->previous_value_type || $has_defined_keys)) {
             $array_type = new TNonEmptyArray([$key_type, $value_type]);
         } else {
             $array_type = new TArray([$key_type, $value_type]);
diff --git a/tests/TypeReconciliation/RedundantConditionTest.php b/tests/TypeReconciliation/RedundantConditionTest.php
index f1de64ba5..01f5120b7 100644
--- a/tests/TypeReconciliation/RedundantConditionTest.php
+++ b/tests/TypeReconciliation/RedundantConditionTest.php
@@ -797,6 +797,14 @@ class RedundantConditionTest extends \Psalm\Tests\TestCase
                         return (int) (hexdec($x) + 1);
                     }',
             ],
+            'unsetArrayWithKnownOffset' => [
+                '<?php
+                    function bar(string $f) : void {
+                        $filter = rand(0, 1) ? explode(",", $f) : [$f];
+                        unset($filter[rand(0, 1)]);
+                        if ($filter) {}
+                    }'
+            ],
         ];
     }