Remove code that was breaking things

src/Psalm/Internal/Analyzer/Statements/Block/IfAnalyzer.php

@@ -195,12 +195,6 @@ class IfAnalyzer
             }
         }
 
-        foreach ($if_context->vars_possibly_in_scope as $var_id => $_) {
-            if (!isset($if_context->vars_in_scope[$var_id])) {
-                $mixed_var_ids[] = $var_id;
-            }
-        }
-
         $if_clauses = Algebra::getFormula(
             $stmt->cond,
             $context->self,

tests/ArrayAccessTest.php

@@ -207,6 +207,26 @@ class ArrayAccessTest extends TestCase
                       }
                     }'
             ],
+            'arrayAccessPropertyAssertion' => [
+                '<?php
+                    class A {}
+                    class B extends A {
+                        /** @var array<int, string> */
+                        public $arr = [];
+                    }
+
+                    /** @var array<A> */
+                    $as = [];
+
+                    if (!$as
+                        || !$as[0] instanceof B
+                        || !$as[0]->arr
+                    ) {
+                        return null;
+                    }
+
+                    $b = $as[0]->arr;',
+            ],
         ];
     }