Crashed!!

This crashes R (sometimes):

    1 
    2 f = function(
    3     a = {x <- y <- z <- w <- t <- u <- 7}
    4 ) environment()
    5 
    6 for (i in 1:1000) {
    7     try(as.list(f()), silent=T)
    8 }
    9 
   10 

The problem is the same as I described in the last post