is.environment, as.environment, and NULL

A question, and a remark.

Question, would we want to keep as.environment(NULL) to give the base
package, so that code like ls(envir = NULL) will still work?

Interesting.  Was it ever documented to?

Remark, we once discussed making package environments (in particular for
base) read-only.  One way of doing this is via setting attributes, but
we cannot do this on NULL.  Not that I think this is the way to do it,
though ...

NULL is just shorthand: there is a proper R object for base:

.GlobalEnv

<environment: R_GlobalEnv>

is.null(.GlobalEnv)

[1] FALSE

It was news to me that NULL for .GlobalEnv worked at R level.

Brian