class RuboCop::Cop::Style::EmptyLiteral

would be a literal, like an empty array, hash or string.
This cop checks for the use of a method, the result of which

def autocorrect(node) 

def autocorrect(node)
  name = case node
         when ARRAY_NODE
           '[]'
         when HASH_NODE
           # `some_method {}` is not same as `some_method Hash.new`
           # because the braces are interpreted as a block, so we avoid
           # the correction. Parentheses around the arguments would
           # solve the problem, but we let the user add those manually.
           return if first_arg_in_method_call_without_parentheses?(node)
           '{}'
         when STR_NODE
           if enforce_double_quotes?
             '""'
           else
             "''"
           end
         end
  ->(corrector) { corrector.replace(node.source_range, name) }
end

def enforce_double_quotes? 

def enforce_double_quotes?
  string_literals_config['EnforcedStyle'] == 'double_quotes'
end

def first_arg_in_method_call_without_parentheses?(node) 

def first_arg_in_method_call_without_parentheses?(node)
  return false unless node.parent && node.parent.send_type?
  _receiver, _method_name, *args = *node.parent
  node.object_id == args.first.object_id && !parentheses?(node.parent)
end

def on_send(node) 

def on_send(node)
  case node
  when ARRAY_NODE
    add_offense(node, :expression, ARR_MSG)
  when HASH_NODE
    # If Hash.new takes a block, it can't be changed to {}.
    return if node.parent && node.parent.block_type?
    add_offense(node, :expression, HASH_MSG)
  when STR_NODE
    add_offense(node, :expression, STR_MSG)
  end
end

def string_literals_config 

def string_literals_config
  config.for_cop('Style/StringLiterals')
end