Add protection for leaky assertions

src/Psalm/Internal/Type/AssertionReconciler.php

@@ -1316,6 +1316,10 @@ class AssertionReconciler extends \Psalm\Type\Reconciler
                     $code_location,
                     $suppressed_issues
                 );
+
+                if (!$did_remove_type) {
+                    $failed_reconciliation = 1;
+                }
             }
         }
 

src/Psalm/Type/Reconciler.php

@@ -283,6 +283,8 @@ class Reconciler
                     $code_location,
                     $suppressed_issues
                 );
+            } elseif (!$has_negation) {
+                $changed_var_ids[] = $key;
             }
 
             if ($failed_reconciliation === 2) {

tests/TypeReconciliationTest.php

@@ -1406,7 +1406,18 @@ class TypeReconciliationTest extends TestCase
                     $x = null;
                     assert($x instanceof Traversable);
                     takesTraversable($x);',
-            ]
+            ],
+            'dontReconcileArrayOffset' => [
+                '<?php
+                    /** @psalm-suppress TypeDoesNotContainType */
+                    function foo(array $a) : void {
+                        if (!is_array($a)) {
+                            return;
+                        }
+
+                        if ($a[0] === 5) {}
+                    }'
+            ],
         ];
     }