From 77c70c0ad2062e823abb0b5120af45a0cac085fc Mon Sep 17 00:00:00 2001
From: orklah <ronan_morin@hotmail.com>
Date: Tue, 5 Oct 2021 16:09:43 +0200
Subject: [PATCH 1/2] allow |false in unions as long as it's not alone and not
 with null

---
 src/Psalm/Type/Union.php | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/src/Psalm/Type/Union.php b/src/Psalm/Type/Union.php
index a5ee23888..83df11bcd 100644
--- a/src/Psalm/Type/Union.php
+++ b/src/Psalm/Type/Union.php
@@ -497,6 +497,14 @@ class Union implements TypeNode
             $nullable = true;
         }
 
+        $falsable = false;
+
+        if (isset($types['false']) && count($types) > 1) {
+            unset($types['false']);
+
+            $falsable = true;
+        }
+
         $php_types = [];
 
         foreach ($types as $atomic_type) {
@@ -515,6 +523,10 @@ class Union implements TypeNode
             $php_types[] = $php_type;
         }
 
+        if ($falsable) {
+            return ($nullable ? '?' : '') . implode('|', array_unique($php_types)) . '|false';
+        }
+
         return ($nullable ? '?' : '') . implode('|', array_unique($php_types));
     }
 

From ecb541ea51ca43f27385a205ad6488ee48eac83c Mon Sep 17 00:00:00 2001
From: orklah <ronan_morin@hotmail.com>
Date: Tue, 5 Oct 2021 16:11:10 +0200
Subject: [PATCH 2/2] add test

---
 .../ReturnTypeManipulationTest.php             | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)

diff --git a/tests/FileManipulation/ReturnTypeManipulationTest.php b/tests/FileManipulation/ReturnTypeManipulationTest.php
index 5eafcffbe..3760cfae6 100644
--- a/tests/FileManipulation/ReturnTypeManipulationTest.php
+++ b/tests/FileManipulation/ReturnTypeManipulationTest.php
@@ -713,6 +713,24 @@ class ReturnTypeManipulationTest extends FileManipulationTestCase
                 ['MissingReturnType'],
                 false,
                 true,
+            ],
+            'OrFalseInReturn' => [
+                '<?php
+                    function a() {
+                        /** @var false|array $a */
+                        $a = false;
+                        return $a;
+                    }',
+                '<?php
+                    function a(): array|false {
+                        /** @var false|array $a */
+                        $a = false;
+                        return $a;
+                    }',
+                '8.0',
+                ['MissingReturnType'],
+                false,
+                true,
             ]
         ];
     }