weld/subsystem/src/main/java/org/jboss/as/weld/WeldModuleResourceLoader.java
@Override
    public Class<?> classForName(String name) {
        try {
            if (classes.containsKey(name)) {
                return classes.get(name);
            }
            final Class<?> clazz = module.getClassLoader().loadClass(name);
            classes.put(name, clazz);
            return clazz;
        } catch (ClassNotFoundException | LinkageError e) {
            throw new ResourceLoadingException(e);
        }
    }
@Override
    public Class<?> classForName(String name) {
        try {
            if (classes.containsKey(name)) {
                return classes.get(name);
            }
            final Class<?> clazz = module.getClassLoader().loadClass(name);
            classes.put(name, clazz);
            return clazz;
        } catch (ClassNotFoundException | LinkageError e) {
            throw new ResourceLoadingException(e);
        }
    }
If the class name is found in additionalClasses then return it.

Otherwise the class will be loaded from the module ClassLoader