From 881dbf86e1561203e14366c70bb5782fd48920c4 Mon Sep 17 00:00:00 2001
From: Matt Brown <github@muglug.com>
Date: Mon, 3 May 2021 12:40:14 -0400
Subject: [PATCH] Fix inference for empty arrays

---
 .../Type/Comparator/ArrayTypeComparator.php     | 17 +++++++++++++----
 src/Psalm/Type/Atomic/TKeyedArray.php           | 11 +++++++++++
 2 files changed, 24 insertions(+), 4 deletions(-)

diff --git a/src/Psalm/Internal/Type/Comparator/ArrayTypeComparator.php b/src/Psalm/Internal/Type/Comparator/ArrayTypeComparator.php
index 0f1579c4f..572e2daee 100644
--- a/src/Psalm/Internal/Type/Comparator/ArrayTypeComparator.php
+++ b/src/Psalm/Internal/Type/Comparator/ArrayTypeComparator.php
@@ -33,11 +33,20 @@ class ArrayTypeComparator
     ) : bool {
         $all_types_contain = true;
 
-        $is_empty_array = $input_type_part->getId() === 'array<empty, empty>';
+        $is_empty_array = $input_type_part->equals(
+            new Type\Atomic\TArray([
+                new Type\Union([new Type\Atomic\TEmpty()]),
+                new Type\Union([new Type\Atomic\TEmpty()])
+            ]),
+            false
+        );
+
         if ($is_empty_array
-            && ($container_type_part instanceof Type\Atomic\TArray
-                || $container_type_part instanceof Type\Atomic\TKeyedArray)
-            && !$container_type_part instanceof Type\Atomic\TNonEmptyArray
+            && (($container_type_part instanceof Type\Atomic\TArray
+                    && !$container_type_part instanceof Type\Atomic\TNonEmptyArray)
+                || ($container_type_part instanceof Type\Atomic\TKeyedArray
+                    && !$container_type_part->isNonEmpty())
+            )
         ) {
             return true;
         }
diff --git a/src/Psalm/Type/Atomic/TKeyedArray.php b/src/Psalm/Type/Atomic/TKeyedArray.php
index 2b71e348d..ff49f9ddb 100644
--- a/src/Psalm/Type/Atomic/TKeyedArray.php
+++ b/src/Psalm/Type/Atomic/TKeyedArray.php
@@ -294,6 +294,17 @@ class TKeyedArray extends \Psalm\Type\Atomic
         return $array_type;
     }
 
+    public function isNonEmpty(): bool
+    {
+        foreach ($this->properties as $key => $property) {
+            if (!$property->possibly_undefined) {
+                return true;
+            }
+        }
+
+        return false;
+    }
+
     public function __clone()
     {
         foreach ($this->properties as &$property) {