module Haml::AttributeParser

def shift_key!(tokens)
  while !tokens.empty? && IGNORED_TYPES.include?(tokens.first[TYPE])
    tokens.shift # ignore spaces
  end
  _, type, first_text = tokens.shift
  case type
  when :on_label # `key:`
    first_text.tr(':', '')
  when :on_symbeg # `:key =>`, `:'key' =>` or `:"key" =>`
    key = tokens.shift[TEXT]
    if first_text != ':' # `:'key'` or `:"key"`
      expect_string_end!(tokens.shift)
    end
    shift_hash_rocket!(tokens)
    key
  when :on_tstring_beg # `"key":`, `'key':` or `"key" =>`
    key = tokens.shift[TEXT]
    next_token = tokens.shift
    if next_token[TYPE] != :on_label_end # on_label_end is `":` or `':`, so `"key" =>`
      expect_string_end!(next_token)
      shift_hash_rocket!(tokens)
    end
    key
  else
    raise UnexpectedKeyError.new("unexpected token is given!: #{first_text} (#{type})")
  end
end