class RuboCop::Cop::Layout::SpaceBeforeBlockBraces

def on_block(node)
  return if node.keywords?
  left_brace = node.loc.begin
  space_plus_brace = range_with_surrounding_space(left_brace)
  used_style =
    space_plus_brace.source.start_with?('{') ? :no_space : :space
  case used_style
  when style  then correct_style_detected
  when :space then space_detected(left_brace, space_plus_brace)
  else             space_missing(left_brace)
  end
end