Fix intersection with substracted

Author: VincentLanglet

src/Type/TypeCombinator.php

@@ -544,6 +544,11 @@ private static function unionWithSubtractedType(
 			$subtractedType = $type->getSubtractedType() === null
 				? $subtractedType
 				: self::union($type->getSubtractedType(), $subtractedType);
+
+			$subtractedType = self::intersect(
+				$type->getTypeWithoutSubtractedType(),
+				$subtractedType,
+			);
 			if ($subtractedType instanceof NeverType) {
 				$subtractedType = null;
 			}

tests/PHPStan/Type/TypeCombinatorTest.php

@@ -4127,6 +4127,22 @@ public static function dataIntersect(): iterable
 				IntersectionType::class,
 				'lowercase-string&uppercase-string',
 			],
+			[
+				[
+					new ObjectType(DateTime::class),
+					new MixedType(subtractedType: new NullType()),
+				],
+				ObjectType::class,
+				'DateTime',
+			],
+			[
+				[
+					new ObjectWithoutClassType(),
+					new MixedType(subtractedType: new NullType()),
+				],
+				ObjectWithoutClassType::class,
+				'object',
+			],
 		];
 
 		if (PHP_VERSION_ID < 80100) {