code: func setIndexKind(fs *fieldSpec, fieldType reflect.Type) error {
  	switch {
  	case typeIsNumeric(fieldType):
  		fs.indexKind = numericIndex
  	case typeIsString(fieldType):
  		fs.indexKind = stringIndex
  	case typeIsBool(fieldType):
  		fs.indexKind = booleanIndex
  	default:
  		return fmt.Errorf("zoom: Requested index on unsupported type %s", fieldType.String())
  	}
  	return nil
  }
docs: // setIndexKind sets the indexKind field of fs based on fieldType.