From 2092cf3045ad535c658fcc475a7f19fb6221a8a3 Mon Sep 17 00:00:00 2001
From: Mathias Hertlein <mathias@mh.cx>
Date: Mon, 30 Mar 2026 21:43:11 +0200
Subject: [PATCH] fix(type-system): generic sealed class-string match
 exhaustiveness

GenericClassStringType::tryRemove() passed the GenericObjectType directly to
TypeCombinator::remove(), but GenericObjectType::isSuperTypeOf(plain ObjectType)
returns Maybe rather than Yes, so the removal was silently skipped. Strips the
generic parameters before delegating to TypeCombinator::remove() so the existing
sealed subtraction logic in ObjectType::changeSubtractedType() can handle it.
---
 src/Type/Generic/GenericClassStringType.php   |  7 ++-
 .../Comparison/MatchExpressionRuleTest.php    |  6 +++
 .../match-generic-sealed-class-string.php     | 45 +++++++++++++++++++
 3 files changed, 56 insertions(+), 2 deletions(-)
 create mode 100644 tests/PHPStan/Rules/Comparison/data/match-generic-sealed-class-string.php

diff --git a/src/Type/Generic/GenericClassStringType.php b/src/Type/Generic/GenericClassStringType.php
index 3123e533d5..d54a7695bc 100644
--- a/src/Type/Generic/GenericClassStringType.php
+++ b/src/Type/Generic/GenericClassStringType.php
@@ -18,6 +18,7 @@
 use PHPStan\Type\ObjectWithoutClassType;
 use PHPStan\Type\StaticType;
 use PHPStan\Type\StringType;
+use PHPStan\Type\SubtractableType;
 use PHPStan\Type\Type;
 use PHPStan\Type\TypeCombinator;
 use PHPStan\Type\UnionType;
@@ -222,12 +223,14 @@ public function tryRemove(Type $typeToRemove): ?Type
 
 					if ($classReflection->getAllowedSubTypes() !== null) {
 						$objectTypeToRemove = new ObjectType($typeToRemove->getValue());
-						$remainingType = TypeCombinator::remove($generic, $objectTypeToRemove);
+						$baseType = new ObjectType($genericObjectClassNames[0],
+							$generic instanceof SubtractableType ? $generic->getSubtractedType() : null);
+						$remainingType = TypeCombinator::remove($baseType, $objectTypeToRemove);
 						if ($remainingType instanceof NeverType) {
 							return new NeverType();
 						}
 
-						if (!$remainingType->equals($generic)) {
+						if (!$remainingType->equals($baseType)) {
 							return new self($remainingType);
 						}
 					}
diff --git a/tests/PHPStan/Rules/Comparison/MatchExpressionRuleTest.php b/tests/PHPStan/Rules/Comparison/MatchExpressionRuleTest.php
index 85b8364a32..1921574431 100644
--- a/tests/PHPStan/Rules/Comparison/MatchExpressionRuleTest.php
+++ b/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 testGenericSealedClassStringMatch(): void
+	{
+		$this->analyse([__DIR__ . '/data/match-generic-sealed-class-string.php'], []);
+	}
+
 	#[RequiresPhp('>= 8.0')]
 	public function testBug13029(): void
 	{
diff --git a/tests/PHPStan/Rules/Comparison/data/match-generic-sealed-class-string.php b/tests/PHPStan/Rules/Comparison/data/match-generic-sealed-class-string.php
new file mode 100644
index 0000000000..3cd65975ce
--- /dev/null
+++ b/tests/PHPStan/Rules/Comparison/data/match-generic-sealed-class-string.php
@@ -0,0 +1,45 @@
+<?php // lint >= 8.0
+
+declare(strict_types = 1);
+
+namespace MatchGenericSealedClassString;
+
+/**
+ * @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',
+	};
+}