code: func (p *Provider) Diff(
  	info *terraform.InstanceInfo,
  	s *terraform.InstanceState,
  	c *terraform.ResourceConfig) (*terraform.InstanceDiff, error) {
  	r, ok := p.ResourcesMap[info.Type]
  	if !ok {
  		return nil, fmt.Errorf("unknown resource type: %s", info.Type)
  	}
  
  	return r.Diff(s, c, p.meta)
  }
docs: // Diff implementation of terraform.ResourceProvider interface.