Fix #13211: Switch statement does not narrow down types based on branch conditions

src/Analyser/NodeScopeResolver.php

@@ -1845,7 +1845,7 @@ private function processStmtNode(
 			}
 
 			if ((!$hasDefaultCase && !$exhaustive) || $finalScope === null) {
-				$finalScope = $scope->mergeWith($finalScope);
+				$finalScope = $scopeForBranches->mergeWith($finalScope);
 			}
 
 			return new InternalStatementResult($finalScope, $hasYield, $alwaysTerminating, $exitPointsForOuterLoop, $throwPoints, $impurePoints);

tests/PHPStan/Analyser/nsrt/bug-13211.php

@@ -0,0 +1,115 @@
+<?php
+
+namespace Bug13211;
+
+use function PHPStan\Testing\assertType;
+
+class Foo
+{
+	public function bar(): void
+	{
+	}
+}
+
+function switchTrueWithExitNarrows(): void
+{
+	$a = random_int(1, 10) > 5 ? new Foo() : null;
+
+	switch (true) {
+		case $a === null:
+			exit;
+	}
+
+	assertType('Bug13211\Foo', $a);
+}
+
+function switchTrueWithReturnNarrows(): void
+{
+	$a = random_int(1, 10) > 5 ? new Foo() : null;
+
+	switch (true) {
+		case $a === null:
+			return;
+	}
+
+	assertType('Bug13211\Foo', $a);
+}
+
+function switchTrueWithThrowNarrows(): void
+{
+	$a = random_int(1, 10) > 5 ? new Foo() : null;
+
+	switch (true) {
+		case $a === null:
+			throw new \Exception();
+	}
+
+	assertType('Bug13211\Foo', $a);
+}
+
+function switchTrueMultipleCases(): void
+{
+	/** @var int|string|null $a */
+	$a = null;
+
+	switch (true) {
+		case $a === null:
+			exit;
+		case is_string($a):
+			exit;
+	}
+
+	assertType('int', $a);
+}
+
+function switchTrueWithInstanceof(): void
+{
+	/** @var Foo|int|null $a */
+	$a = null;
+
+	switch (true) {
+		case $a instanceof Foo:
+			exit;
+	}
+
+	assertType('int|null', $a);
+}
+
+function switchTrueWithBreakDoesNotNarrow(): void
+{
+	$a = random_int(1, 10) > 5 ? new Foo() : null;
+
+	switch (true) {
+		case $a === null:
+			break;
+	}
+
+	assertType('Bug13211\Foo|null', $a);
+}
+
+function switchTrueWithDefaultCase(): void
+{
+	$a = random_int(1, 10) > 5 ? new Foo() : null;
+
+	switch (true) {
+		case $a === null:
+			exit;
+		default:
+			break;
+	}
+
+	assertType('Bug13211\Foo', $a);
+}
+
+function regularSwitchStillWorks(): void
+{
+	/** @var 1|2|3 $a */
+	$a = 1;
+
+	switch ($a) {
+		case 1:
+			exit;
+	}
+
+	assertType('2|3', $a);
+}