stop <- function(..., call. = FALSE, domain = NULL){
  base::stop(..., call. = call., domain = domain);
}

> stop(simpleError("foo"))
Error: foo
In addition: Warning message:
 In base::stop(..., call. = call., domain = domain) :
 additional arguments ignored in stop()

if (length(args) == 1L && inherits(args[[1L]], "condition")) {
    ....
    if (nargs() > 1L) # give the warning

stop(simpleError('achtung!'))
# Error: achtung!
stop(simpleError('achtung!'), call.=F) # gives the warning
# Error: achtung!
# In addition: Warning message:
# In stop(simpleError("achtung!"), call. = F) :
#   additional arguments ignored in stop()
stop(simpleError('achtung!', call=call('f')))
# Error in f() : achtung!