Argument-Dependent Return-Type Variance

Listing 1

static VALUE Record_subscript(VALUE self, VALUE index)
{
  VALUE ret;
  switch(rb_type(index))
  {
    case    T_STRING:
      ret = Record_subscript_string(self, StringValuePtr(index), 1);
      break;
    case    T_FIXNUM:
      ret = Record_subscript_fixnum(self, FIX2INT(index), 1);
      break;
    default:
      rb_raise(rb_eTypeError, "field index / name must be integer or string");
      break;
  }
  return ret;
}

static VALUE Record_subscript_string(VALUE self, char const *index, int bThrowOnFail)
{
  ORJRecord const *record = Record_get_record_(self);
  ORJFieldA const *field  = ORJ_Record_FindFieldByNameA(record, index,
      NULL);

  if(NULL == field)
  {
    if(bThrowOnFail)
    {
      rb_raise(cFieldNameError, 
          "record does not contain field named: %s", index);
    }
    return Qnil;
  }
  else
  {
    return rb_str_from_ORJStringA(&field->value);
  }
}

static VALUE Record_subscript_fixnum(VALUE self, int index, int bThrowOnFail)
{
  ORJRecord const *record = Record_get_record_(self);
  size_t          cFields = ORJ_Record_GetNumFieldsA(record);

  if( 0 <= index &&
      index < cFields)
  {
    VALUE   __database__  = rb_iv_get(self, "@__database__");
    return Field_create_(__database__, self, &record->fields[index]);
  }
  else
  {
    if(bThrowOnFail)
    {
      rb_raise(rb_eIndexError, "record does not contain field at index: %d", index);
    }
    return Qnil;
  }
}