code: func (h Hostname) ForDisplay() string {
  	given := string(h)
  	var portPortion string
  	if colonPos := strings.Index(given, ":"); colonPos != -1 {
  		given, portPortion = given[:colonPos], given[colonPos:]
  	}
  	// We don't normalize the port portion here because we assume it's
  	// already been normalized on the way in.
  
  	result, err := idna.Lookup.ToUnicode(given)
  	if err != nil {
  		// Should never happen, since type Hostname indicates that a string
  		// passed through our validation rules.
  		panic(fmt.Errorf("ForDisplay called on invalid Hostname: %s", err))
  	}
  	return result + portPortion
  }
docs: // ForDisplay returns a version of the receiver that is appropriate for display
  // in the UI. This includes converting any punycode labels to their
  // corresponding Unicode characters.
  //
  // A round-trip through ForComparison and this ForDisplay method does not
  // guarantee the same result as calling this package's top-level ForDisplay
  // function, since a round-trip through the Hostname type implies stricter
  // handling than we do when doing basic display-only processing.