code: func URL(url string) {
  	switch def := dslengine.CurrentDefinition().(type) {
  	case *design.ContactDefinition:
  		def.URL = url
  	case *design.LicenseDefinition:
  		def.URL = url
  	case *design.DocsDefinition:
  		def.URL = url
  	default:
  		dslengine.IncompatibleDSL()
  	}
  }
docs: // URL can be used in: Contact, License, Docs
  //
  // URL sets the contact, license, or Docs URL.