FR: julia style self-naming args

[t-kalinowski]

Julia has a really neat syntax for self naming of args, where

fn(a, b; c, d) 

is the same as

fn(a, b, c=c, d=d)

rlang already has support for self-naming args in rlang::dots_list() and rlang::list2(). It would be great if R users could opt into the self naming args semantics to avoid spelling out some argument names twice.

I'm not sure what syntax would be concise, convenient, readable, and make it past the R parser.
Maybe something like:

fn(a, b, .=., c, d)
fn(a, b, .~., c, d)
fn(a, b, ~..., c, d)

Edit:

I suppose an approximation is possible today with:

named <- function(...) dots_list(.named = TRUE, ...) 
fn(a, b, !!!named(c, d))