code: private void enterBinop(String name,
                              Type left, Type right, Type res,
                              int opcode) {
          predefClass.members().enter(
              new OperatorSymbol(
                  makeOperatorName(name),
                  new MethodType(List.of(left, right), res,
                                 List.<Type>nil(), methodClass),
                  opcode,
                  predefClass));
      }
docs: Enter a binary operation into symbol table.
  @param name     The name of the operator.
  @param left     The type of the left operand.
  @param right    The type of the left operand.
  @param res      The operation's result type.
  @param opcode   The operation's bytecode instruction.