Partial matching list elements in R 4.0

{x <- list(Abc=list(Pqr="Old Abc$Pqr")); x$Ab$Pqr <- "New Ab$Pqr" ; x}

Hello,


I'm testing some code in R 4.0, and I'm having an issue with the following"

# -------------
rm(list=ls())
graphics.off()
#load("/tmp/post.RData")
var = list();
# If I uncomment this it fixes things:
# var$options = list(mi   = list(),
#                    misc = list())
#
var$options$misc$abc = "123"
var$options$mi$something    = 13
#------------

This is a stripped down example but it exhibits the issue I"m having.
Basically when I create the list element var$options$mi the contents of
var$options$misc move over to var$options$mi. And what was in
var$options$misc become NULL:

So now var$options looks like:

var$options
$misc
$misc$abc
NULL

$mi
$mi$abc
[1] "123"
$mi$something
[1] 13

This worked (still works) in R 3.5.1. I understand partial matching, but is
this normal lists moving over to elements like this? I can uncomment the
text mentioned in the example and it seems to fix it, but I'm wondering if
this is a bug or just my poor programming coming back to bite me.

I've included my sessionInfo() at the bottom.

Thanks
John
:wq


sessionInfo()

R version 4.0.0 (2020-04-24)

Platform: x86_64-apple-darwin17.0 (64-bit)

Running under: macOS Mojave 10.14.5


Matrix products: default

BLAS:
/Library/Frameworks/R.framework/Versions/4.0/Resources/lib/libRblas.dylib

LAPACK:
/Library/Frameworks/R.framework/Versions/4.0/Resources/lib/libRlapack.dylib


locale:

[1] en_US.UTF-8/en_US.UTF-8/en_US.UTF-8/C/en_US.UTF-8/en_US.UTF-8


attached base packages:

[1] stats     graphics  grDevices utils     datasets  methods   base


other attached packages:

[1] gdata_2.18.0  ggplot2_3.3.0 deSolve_1.28


loaded via a namespace (and not attached):

 [1] Rcpp_1.0.4.6     gtools_3.8.2     withr_2.2.0      assertthat_0.2.1

 [5] dplyr_0.8.5      digest_0.6.25    crayon_1.3.4     grid_4.0.0

 [9] R6_2.4.1         lifecycle_0.2.0  gtable_0.3.0     magrittr_1.5

[13] scales_1.1.1     pillar_1.4.4     rlang_0.4.6      vctrs_0.3.0

[17] ellipsis_0.3.1   glue_1.4.1       purrr_0.3.4      munsell_0.5.0

[21] compiler_4.0.0   pkgconfig_2.0.3  colorspace_1.4-1 tidyselect_1.1.0

[25] tibble_3.0.1

        [[alternative HTML version deleted]]