Merge pull request #6594 from orklah/falsable-returns

Falsable returns

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));
     }
 

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,
             ]
         ];
     }