class RuboCop::AST::NodePattern::Compiler::SequenceSubcompiler

def use_index_from_end

returns truthy iff `@cur_index` switched to relative from end mode (i.e. < 0) 
def use_index_from_end
  return if @cur_index == :seq_head || @remaining_arity.begin != @remaining_arity.max
  @cur_index = -@remaining_arity.begin - DELTA
end