class Parser::Builders::Default

def op_assign(lhs, op_t, rhs) 

def op_assign(lhs, op_t, rhs)
  case lhs.type
  when :gvasgn, :ivasgn, :lvasgn, :cvasgn, :casgn, :send, :csend, :index
    operator   = value(op_t)[0..-1].to_sym
    source_map = lhs.loc.
                    with_operator(loc(op_t)).
                    with_expression(join_exprs(lhs, rhs))
    if lhs.type  == :index
      lhs = lhs.updated(:indexasgn)
    end
    case operator
    when :'&&'
      n(:and_asgn, [ lhs, rhs ], source_map)
    when :'||'
      n(:or_asgn, [ lhs, rhs ], source_map)
    else
      n(:op_asgn, [ lhs, operator, rhs ], source_map)
    end
  when :back_ref, :nth_ref
    diagnostic :error, :backref_assignment, nil, lhs.loc.expression
  end
end