From 1474340cf21cf687f09ecb733a86ab5ac3e1a0bb Mon Sep 17 00:00:00 2001
From: Bruce Weirdan <weirdan@gmail.com>
Date: Sun, 20 Aug 2023 23:39:21 +0200
Subject: [PATCH] Fix crash on array access to undefined class

---
 .../Expression/Fetch/ArrayFetchAnalyzer.php   |  4 +++-
 tests/ArrayAccessTest.php                     | 21 +++++++++++++++++++
 2 files changed, 24 insertions(+), 1 deletion(-)

diff --git a/src/Psalm/Internal/Analyzer/Statements/Expression/Fetch/ArrayFetchAnalyzer.php b/src/Psalm/Internal/Analyzer/Statements/Expression/Fetch/ArrayFetchAnalyzer.php
index 5e30eb5029c..9c6d85d7639 100644
--- a/src/Psalm/Internal/Analyzer/Statements/Expression/Fetch/ArrayFetchAnalyzer.php
+++ b/src/Psalm/Internal/Analyzer/Statements/Expression/Fetch/ArrayFetchAnalyzer.php
@@ -1737,8 +1737,10 @@ private static function handleArrayAccessOnNamedObject(
         ?Union &$array_access_type,
         bool &$has_array_access
     ): void {
+        $codebase = $statements_analyzer->getCodebase();
         if (strtolower($type->value) === 'simplexmlelement'
-            || $statements_analyzer->getCodebase()->classExtendsOrImplements($type->value, 'SimpleXMLElement')
+            || ($codebase->classExists($type->value)
+                && $codebase->classExtendsOrImplements($type->value, 'SimpleXMLElement'))
         ) {
             $call_array_access_type = new Union([new TNull(), new TNamedObject('SimpleXMLElement')]);
         } elseif (strtolower($type->value) === 'domnodelist' && $stmt->dim) {
diff --git a/tests/ArrayAccessTest.php b/tests/ArrayAccessTest.php
index d216ca7393a..2302b2661b6 100644
--- a/tests/ArrayAccessTest.php
+++ b/tests/ArrayAccessTest.php
@@ -1199,6 +1199,27 @@ function f($p): int {
                 ',
                 'assertions' => ['$a===' => "array{1: 'b'}"],
             ],
+            'noCrashOnUnknownClassArrayAccess' => [
+                'code' => <<<'PHP'
+                <?php
+
+                namespace Psalmtest\Psalmtest;
+
+                use SomeMissingClass;
+
+                class Test
+                {
+                    public function f(): void {
+                        /** @var SomeMissingClass */
+                        $result = null;
+
+                        if ($result['errors'] === true) {}
+                    }
+                }
+                PHP,
+                'assertions' => [],
+                'ignored_issues' => ['UndefinedDocblockClass'],
+            ],
         ];
     }