Fix sealed class-string match exhaustiveness for generic sealed hierarchies

- GenericObjectType::changeSubtractedType() now delegates to parent's sealed
  type logic, returning NeverType when all allowed subtypes are subtracted
- This fixes match expressions on $foo::class reporting "unhandled values"
  for generic @phpstan-sealed class hierarchies
- New regression test in tests/PHPStan/Rules/Comparison/data/bug-14412.php

Closes phpstan/phpstan#14412

Author: phpstan-bot

phpstan-baseline.neon

@@ -1134,7 +1134,7 @@ parameters:
 		-
 			rawMessage: 'Doing instanceof PHPStan\Type\ObjectType is error-prone and deprecated. Use Type::isObject() or Type::getObjectClassNames() instead.'
 			identifier: phpstanApi.instanceofType
-			count: 1
+			count: 2
 			path: src/Type/Generic/GenericObjectType.php
 
 		-

src/Type/Generic/GenericObjectType.php

@@ -405,6 +405,14 @@ protected function recreate(string $className, array $types, ?Type $subtractedTy
 
 	public function changeSubtractedType(?Type $subtractedType): Type
 	{
+		$result = parent::changeSubtractedType($subtractedType);
+
+		// Parent handles sealed type exhaustiveness (returning NeverType when all
+		// allowed subtypes are subtracted, or a single remaining subtype).
+		if (!$result instanceof ObjectType || $result->getClassName() !== $this->getClassName()) {
+			return $result;
+		}
+
 		return new self($this->getClassName(), $this->types, $subtractedType, null, $this->variances);
 	}
 

tests/PHPStan/Rules/Comparison/MatchExpressionRuleTest.php

@@ -453,6 +453,12 @@ public function testBug12241(): void
 		$this->analyse([__DIR__ . '/data/bug-12241.php'], []);
 	}
 
+	#[RequiresPhp('>= 8.0')]
+	public function testBug14412(): void
+	{
+		$this->analyse([__DIR__ . '/data/bug-14412.php'], []);
+	}
+
 	#[RequiresPhp('>= 8.0')]
 	public function testBug13029(): void
 	{

tests/PHPStan/Rules/Comparison/data/bug-14412.php

@@ -0,0 +1,57 @@
+<?php // lint >= 8.0
+
+declare(strict_types = 1);
+
+namespace Bug14412;
+
+/**
+ * @template-covariant T
+ * @phpstan-sealed BarCov|BazCov
+ */
+abstract class FooCov {}
+
+/**
+ * @template-covariant T
+ * @extends FooCov<T>
+ */
+final class BarCov extends FooCov {}
+
+/**
+ * @template-covariant T
+ * @extends FooCov<T>
+ */
+final class BazCov extends FooCov {}
+
+/** @param FooCov<string> $foo */
+function testTemplateCovariant(FooCov $foo): string {
+	return match ($foo::class) {
+		BarCov::class => 'bar',
+		BazCov::class => 'baz',
+	};
+}
+
+/**
+ * @template T
+ * @phpstan-sealed BarInv|BazInv
+ */
+abstract class FooInv {}
+
+/**
+ * @template T
+ * @extends FooInv<T>
+ */
+final class BarInv extends FooInv {}
+
+/**
+ * @template T
+ * @extends FooInv<T>
+ */
+final class BazInv extends FooInv {}
+
+/** @param FooInv<covariant string> $foo */
+function testCovariantParam(FooInv $foo): string {
+	return match ($foo::class) {
+		BarInv::class => 'bar',
+		BazInv::class => 'baz',
+	};
+}