From 75d1f79a3d76fbef35bb89e5b0f5f1662b72293d Mon Sep 17 00:00:00 2001
From: Matt Brown <github@muglug.com>
Date: Sun, 17 Jan 2021 12:22:29 -0500
Subject: [PATCH] Fix #5017 - handle combining literal and non-empty strings

---
 src/Psalm/Internal/Type/TypeCombiner.php | 22 ++++++++++++++++++++++
 tests/TypeCombinationTest.php            | 14 ++++++++++++++
 2 files changed, 36 insertions(+)

diff --git a/src/Psalm/Internal/Type/TypeCombiner.php b/src/Psalm/Internal/Type/TypeCombiner.php
index 48da6f5c8..151824d0c 100644
--- a/src/Psalm/Internal/Type/TypeCombiner.php
+++ b/src/Psalm/Internal/Type/TypeCombiner.php
@@ -931,6 +931,11 @@ class TypeCombiner
                             && \strtolower($type->value) === $type->value
                         ) {
                             // do nothing
+                        } elseif (isset($combination->value_types['string'])
+                            && $combination->value_types['string'] instanceof Type\Atomic\TNonEmptyString
+                            && $type->value
+                        ) {
+                            // do nothing
                         } else {
                             $combination->value_types['string'] = new TString();
                         }
@@ -974,6 +979,23 @@ class TypeCombiner
                                 $combination->value_types['string'] = $type;
                             }
 
+                            $combination->strings = null;
+                        } elseif ($type instanceof Type\Atomic\TNonEmptyString) {
+                            $has_empty_string = false;
+
+                            foreach ($combination->strings as $string_type) {
+                                if (!$string_type->value) {
+                                    $has_empty_string = true;
+                                    break;
+                                }
+                            }
+
+                            if ($has_empty_string) {
+                                $combination->value_types['string'] = new TString();
+                            } else {
+                                $combination->value_types['string'] = $type;
+                            }
+
                             $combination->strings = null;
                         } else {
                             $has_non_literal_class_string = false;
diff --git a/tests/TypeCombinationTest.php b/tests/TypeCombinationTest.php
index a5a30ce0b..5f97c45a0 100644
--- a/tests/TypeCombinationTest.php
+++ b/tests/TypeCombinationTest.php
@@ -644,6 +644,20 @@ class TypeCombinationTest extends TestCase
                     'array{0?:int}',
                 ]
             ],
+            'combinNonEmptyStringAndLiteral' => [
+                'non-empty-string',
+                [
+                    'non-empty-string',
+                    '"foo"',
+                ]
+            ],
+            'combinLiteralAndNonEmptyString' => [
+                'non-empty-string',
+                [
+                    '"foo"',
+                    'non-empty-string'
+                ]
+            ],
         ];
     }