[R] Modern Symbolic debugger for R programmes?

[Worik R]

I think I am whistling in the wind, but is there a modern symbolic
debugger for R programmes?

I am working through some  one else's code, thousands of lines, that
has the occasional bug in it, and a lot in my understanding of it.

I cannot make setBreakpoint or findLineNum  work.  I get "No source
refs found.".  I am starting to loose my mind!

A debugger where I could set breakpoints with a little more
granularity than the function level and a little more accessible than
the trace function.  What I ideally want is GDB for R.

Does that exist?

cheers
Worik