[Rd] match.call enhancements in 3.2.2

[brodie gaslam]

I was thrilled to see this in the change log:
> match.call() gains an envir argument for specifying the environment from which to retrieve the ... in the call, if any; this environment was wrong (or at least undesirable) when the definition argument was a function.
This was an issue I ran into a few years ago.  I ended up writing my own version that allows specification of the environment, but being able to rely on the built in R version seems much better.  That said, one issue remains as far as I can tell: if the `...` values are expressions they are substituted by `..1`, `..2`, etc.  For example:
> fun0 <- function(...) {
>   fun_gpar <- function(b, ...) {
>     fun_par <- function(a)
>       match.call(fun_gpar, sys.call(sys.parent()), envir=parent.frame(2L))
>     fun_par()
>   }
>   fun_gpar(...)
> }
> fun0(999, 2 + 2, 3 * pi(), 4)

Returns:
> fun_gpar(b = 999, ..2, ..3, 4)
Instead of:

> fun_gpar(b = 999, 2 + 2, 3 * pi(), 4)
This is better than what used to happen before we had access to the `envir` parameter:

> fun_gpar(b = ..1, ..2, 4)
The dot substitution happens in `subDots` in `main/src/unique.c at 1228` (in 3.2.2 sources available as of today in CRAN).  Here is a snippet from that function:
>    for(a = dots, b = rval, i = 1; i <= len; a = CDR(a), b = CDR(b), i++) {
>        SET_TAG(b, TAG(a));
>        t = CAR(a);
>        while (TYPEOF(t) == PROMSXP)
>            t = PREXPR(t);
>        if( isSymbol(t) || isLanguage(t) )
>            SETCAR(b, installDDVAL(i));   // <-- HERE
>        else
>            SETCAR(b, t);
>    }

The `installDDVAL(i)` generates the `..X` symbols.  I'm sure there is a very good reason why this is done, but then it does lead to the issues above.
Am I just doing something wrong?
My workaround (https://github.com/brodieG/matchcall) addresses both the `..X` issue as well as the environment issue, but I'd prefer to deprecate it in favor of a base R solution if possible.
B.

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