[Rd] Maybe a bug in warning() for condition objects?

[dhinds at sonic.net]

I'm using R-2.3.1 but the code in question is the same in the
01-Oct-2006 snapshot for release 2.4.0.  I'd like to evaluate an
expression, catching errors and handling them as warnings.  My first
attempt:

  x <- tryCatch(lm(xyzzy), error=warning)

didn't work; the error is still treated as an error, not a warning.
So I thought, hmmm, the condition is still classed as an "error", how
about if I change that:

  as.warning <- function(e) warning(simpleWarning(e$message,e$call))
  x <- tryCatch(lm(xyzzy), error=as.warning)

Still no luck.  But this works:

  as.warning <- function(e) .signalSimpleWarning(e$message,e$call)
  x <- tryCatch(lm(xyzzy), error=as.warning)

I think the problem here is that warning() contains the code:

        withRestarts({
            .Internal(.signalCondition(cond, message, call))
            .Internal(.dfltStop(message, call))
        }, muffleWarning = function() NULL)

i.e., the default action is .dfltStop(), not .dfltWarn().  Is this
intentional?  It seems to make more sense to me for the default action
for conditions passed to warning() to be .dfltWarn(), but I may well
be misunderstanding something.

-- David Hinds