On 2009, @forkandwait asked this and there was no straightforward answer. One year later, @David B asked it again and the situation was no different.
So now, six years later, with R version 3, I'm asking this very basic question again:
Is there any way to get error messages with line numbers in R?
If there's still no straightforward way to do this, I want to know what strategies you use to debug your script.