HHH-18384 Changes after PR comments

Author: cigaly

hibernate-core/src/main/java/org/hibernate/boot/model/internal/EntityBinder.java

@@ -633,7 +633,8 @@ private static PropertyData getUniqueIdPropertyFromBaseClass(
 				inferredData.getPropertyType(),
 				propertyAccessor
 		);
-		addElementsOfClass( baseClassElements, propContainer, context, 0 );
+		final int idPropertyCount = addElementsOfClass( baseClassElements, propContainer, context, 0 );
+		assert idPropertyCount == 1;
 		//Id properties are on top and there is only one
 		return baseClassElements.get( 0 );
 	}

hibernate-core/src/main/java/org/hibernate/boot/model/internal/PropertyBinder.java

@@ -585,8 +585,8 @@ private void validateOptimisticLock(boolean excluded) {
 	 * @param propertyContainer Metadata about a class and its properties
 	 * @param idPropertyCounter number of id properties already present in list of {@link PropertyData} instances
 	 *
-	 * @return total number of id properties found after iterating the elements of
-	 * {@code annotatedClass} using the determined access strategy
+	 * @return total number of id properties found after iterating the elements of {@code annotatedClass}
+	 * using the determined access strategy (starting from the provided {@code idPropertyCounter})
 	 */
 	static int addElementsOfClass(
 			List<PropertyData> elements,
@@ -602,7 +602,8 @@ private static int addProperty(
 			PropertyContainer propertyContainer,
 			MemberDetails property,
 			List<PropertyData> inFlightPropertyDataList,
-			MetadataBuildingContext context, int idPropertyCounter) {
+			MetadataBuildingContext context,
+			int idPropertyCounter) {
 		// see if inFlightPropertyDataList already contains a PropertyData for this name,
 		// and if so, skip it...
 		for ( PropertyData propertyData : inFlightPropertyDataList ) {