`methods` do not load when using package notation :: object

Question

`methods` do not load when using package notation :: object

I am having trouble executing functions that rely on package methods when running through Rscript. I already know that the methods are not connected via Rscript, but it must be loaded (and used) by dependent packages and accessible through their package namespaces, at least I thought so ...

R script example (executed via Rscript):

#!/usr/bin/Rscript

sessionInfo()

tryCatch({
    str(lubridate::days(30))
}, error = function(e) {
    print(e)
})

sessionInfo()

tryCatch({
    str(lubridate::days(30))
}, error = function(e) {
    print(e)
})

library(methods)
str(lubridate::days(30))
sessionInfo()

The result, with my comments and questions mixed below ...

First, here's the launch sessionInfo():

# sessionInfo()

R version 3.2.2 (2015-08-14)
Platform: x86_64-redhat-linux-gnu (64-bit)
Running under: Amazon Linux AMI 2015.09

locale:
 [1] LC_CTYPE=en_US.UTF-8       LC_NUMERIC=C
 [3] LC_TIME=en_US.UTF-8        LC_COLLATE=en_US.UTF-8
 [5] LC_MONETARY=en_US.UTF-8    LC_MESSAGES=en_US.UTF-8
 [7] LC_PAPER=en_US.UTF-8       LC_NAME=C
 [9] LC_ADDRESS=C               LC_TELEPHONE=C
[11] LC_MEASUREMENT=en_US.UTF-8 LC_IDENTIFICATION=C

attached base packages:
[1] stats     graphics  grDevices utils     datasets  base

As expected with Rscript, the package methods are neither connected nor loaded.

, , , lubridate::days(30) , lubridate "" , lubridate DESCRIPTION. :

# tryCatch({
#     str(lubridate::days(30))
# }, error = function(e) {
#     print(e)
# })

<simpleError in .setupMethodsTables(fdef, initialize = TRUE): trying to get slot "group" from an object of a basic class ("NULL") with no slots>

, , , , sessionInfo():

# sessionInfo()  

R version 3.2.2 (2015-08-14)
Platform: x86_64-redhat-linux-gnu (64-bit)
Running under: Amazon Linux AMI 2015.09

locale:
 [1] LC_CTYPE=en_US.UTF-8       LC_NUMERIC=C
 [3] LC_TIME=en_US.UTF-8        LC_COLLATE=en_US.UTF-8
 [5] LC_MONETARY=en_US.UTF-8    LC_MESSAGES=en_US.UTF-8
 [7] LC_PAPER=en_US.UTF-8       LC_NAME=C
 [9] LC_ADDRESS=C               LC_TELEPHONE=C
[11] LC_MEASUREMENT=en_US.UTF-8 LC_IDENTIFICATION=C

attached base packages:
[1] stats     graphics  grDevices utils     datasets  base

loaded via a namespace (and not attached):
[1] magrittr_1.5         tools_3.2.2          lubridate_1.5.6.9000
[4] stringi_1.0-1        methods_3.2.2        stringr_1.0.0

( ), lubridate::days(30):

# tryCatch({
#     str(lubridate::days(30))
# }, error = function(e) {
#     print(e)
# })

<simpleError in .setupMethodsTables(fdef, initialize = TRUE): trying to get slot "group" from an object of a basic class ("NULL") with no slots>

.

, lubridate::days(30):

# library(methods)
# str(lubridate::days(30))

Formal class 'Period' [package "lubridate"] with 6 slots
  ..@ .Data : num 0
  ..@ year  : num 0
  ..@ month : num 0
  ..@ day   : num 30
  ..@ hour  : num 0
  ..@ minute: num 0

! , ?:

# sessionInfo()

R version 3.2.2 (2015-08-14)
Platform: x86_64-redhat-linux-gnu (64-bit)
Running under: Amazon Linux AMI 2015.09

locale:
 [1] LC_CTYPE=en_US.UTF-8       LC_NUMERIC=C
 [3] LC_TIME=en_US.UTF-8        LC_COLLATE=en_US.UTF-8
 [5] LC_MONETARY=en_US.UTF-8    LC_MESSAGES=en_US.UTF-8
 [7] LC_PAPER=en_US.UTF-8       LC_NAME=C
 [9] LC_ADDRESS=C               LC_TELEPHONE=C
[11] LC_MEASUREMENT=en_US.UTF-8 LC_IDENTIFICATION=C

attached base packages:
[1] methods   stats     graphics  grDevices utils     datasets  base

loaded via a namespace (and not attached):
[1] magrittr_1.5         tools_3.2.2          lubridate_1.5.6.9000
[4] stringi_1.0-1        stringr_1.0.0