Improve

Author: VincentLanglet

src/Type/UnionType.php

@@ -22,6 +22,7 @@
 use PHPStan\Type\Generic\GenericClassStringType;
 use PHPStan\Type\Generic\TemplateMixedType;
 use PHPStan\Type\Generic\TemplateType;
+use PHPStan\Type\Generic\TemplateTypeFactory;
 use PHPStan\Type\Generic\TemplateTypeMap;
 use PHPStan\Type\Generic\TemplateTypeVariance;
 use PHPStan\Type\Generic\TemplateUnionType;
@@ -106,7 +107,22 @@ public function filterTypes(callable $filterCb): Type
 			return $this;
 		}
 
-		return TypeCombinator::union(...$newTypes);
+		$result = TypeCombinator::union(...$newTypes);
+		if ($this instanceof BenevolentUnionType) {
+			$result = TypeUtils::toBenevolentUnion($result);
+		}
+		if ($this instanceof TemplateType) {
+			$result = TemplateTypeFactory::create(
+				$this->getScope(),
+				$this->getName(),
+				$result,
+				$this->getVariance(),
+				$this->getStrategy(),
+				$this->getDefault(),
+			);
+		}
+
+		return $result;
 	}
 
 	public function isNormalized(): bool

tests/PHPStan/Rules/Methods/data/bug-11663.php

@@ -26,6 +26,14 @@ public function where(string $test)
 	}
 }
 
+interface A
+{
+	public function doFoo(): static;
+}
+
+interface B
+{
+}
 
 class Test
 {
@@ -38,4 +46,34 @@ public function test($template)
 	{
 		return $template->where('test');
 	}
+
+	/**
+	 * @param __benevolent<BuilderA|BuilderB|false> $template
+	 * @return __benevolent<BuilderA|BuilderB>
+	 */
+	public function test2($template)
+	{
+		return $template->where('test');
+	}
+
+
+	/**
+	 * @template T of A|B
+	 * @param T $ab
+	 * @return T
+	 */
+	function foo(A|B $ab): A|B
+	{
+		return $ab->doFoo();
+	}
+
+	/**
+	 * @template T of __benevolent<A|B>
+	 * @param T $ab
+	 * @return T
+	 */
+	function foo2(A|B $ab): A|B
+	{
+		return $ab->doFoo();
+	}
 }