Fix/issue 3601

src/Analyser/NodeScopeResolver.php

@@ -2383,6 +2383,8 @@ static function (?Type $offsetType, Type $valueType) use (&$arrayType): void {
 				$hasYield = $hasYield || $result->hasYield();
 				$throwPoints = array_merge($throwPoints, $result->getThrowPoints());
 				$nonNullabilityResults[] = $nonNullabilityResult;
+			}
+			foreach (array_reverse($expr->vars) as $var) {
 				$scope = $this->lookForUnsetAllowedUndefinedExpressions($scope, $var);
 			}
 			foreach (array_reverse($nonNullabilityResults) as $nonNullabilityResult) {

tests/PHPStan/Rules/Variables/DefinedVariableRuleTest.php

@@ -862,4 +862,13 @@ public function testBug6112(): void
 		$this->analyse([__DIR__ . '/data/bug-6112.php'], []);
 	}
 
+	public function testBug3601(): void
+	{
+		$this->cliArgumentsVariablesRegistered = true;
+		$this->polluteScopeWithLoopInitialAssignments = true;
+		$this->checkMaybeUndefinedVariables = true;
+		$this->polluteScopeWithAlwaysIterableForeach = true;
+		$this->analyse([__DIR__ . '/data/bug-3601.php'], []);
+	}
+
 }

tests/PHPStan/Rules/Variables/data/bug-3601.php

@@ -0,0 +1,15 @@
+<?php declare(strict_types = 1);
+
+namespace Bug3601;
+
+if (rand(0, 1)) {
+	$a = 'b';
+}
+
+if (rand(0, 1)) {
+	$c = ['b' => 'everything is fine'];
+}
+
+if (isset($a, $c, $c[$a])) {
+	echo $c[$a];
+}