access an element with empty name

Serguei Sokol writes:

Hi,
I came across a case where I cannot access a list element by its empty name.
Minimal example can be constructed as

 ??? x=list("A", 1)
 ??? names(x)=c("a", "")
 ??? x[["a"]]
 ??? #[1]? "A"
 ??? x[[""]]
 ??? #NULL
 ??? x$`a`
 ??? #[1]? "A"
 ??? x$``
 ??? # Error: attempt to use zero-length variable name
 ??? # but we can still access the second element by its index
 ??? x[[2]]
 ??? #[1] 1

To my mind, it should be perfectly legal to access an element by an 
empty name as we can have for example
 ??? match("", names(x))
 ??? #[1] 2
Hence a traditional question: is it a bug or feature?

Best,
Serguei.

sessionInfo()

R version 3.5.0 (2018-04-23)
Platform: x86_64-pc-linux-gnu (64-bit)
Running under: Mageia 6

Matrix products: default
BLAS/LAPACK: /home/opt/OpenBLAS/lib/libopenblas_sandybridge-r0.3.0.dev.so

locale:
[1] C

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

loaded via a namespace (and not attached):
[1] compiler_3.5.0

Serguei Sokol writes:

Hi,
I came across a case where I cannot access a list element by its empty name.
Minimal example can be constructed as
  ??? x=list("A", 1)
  ??? names(x)=c("a", "")
  ??? x[["a"]]
  ??? #[1]? "A"
  ??? x[[""]]
  ??? #NULL
  ??? x$`a`
  ??? #[1]? "A"
  ??? x$``
  ??? # Error: attempt to use zero-length variable name
  ??? # but we can still access the second element by its index
  ??? x[[2]]
  ??? #[1] 1
To my mind, it should be perfectly legal to access an element by an
empty name as we can have for example
  ??? match("", names(x))
  ??? #[1] 2
Hence a traditional question: is it a bug or feature?

A feature according to the docs: ? Extract says

     Neither empty (?""?) nor ?NA? indices match any names, not even
     empty nor missing names.