code: func (m *Map) Diff(
  	info *terraform.InstanceInfo,
  	s *terraform.InstanceState,
  	c *terraform.ResourceConfig,
  	meta interface{}) (*terraform.InstanceDiff, error) {
  	r, ok := m.Mapping[info.Type]
  	if !ok {
  		return nil, fmt.Errorf("Unknown resource type: %s", info.Type)
  	}
  
  	return r.Diff(s, c, meta)
  }
docs: // Diff performs a diff on the proper resource type.