[ESS-bugs] C-u C-c C-c does not make it visible

[Martin Maechler]

"Of course", I still have  ess-eval-visibly-p  set to nil.

But occasionally (e.g. when teaching !) I may want visibility
temporarily, and I use  the prefix (C-u) to turn it on.

However, with ess-tracebug turned on (the default now),
this fails,
even though the docu clearly claims that it should work :

> C-c C-c runs the command ess-eval-region-or-function-or-paragraph-and-step,
> which is an interactive compiled Lisp function in `ess-inf.el'.
> 
> It is bound to C-c C-c, <menu-bar> <ESS> <Eval region | func | para & step>,
> <menu-bar> <ESS> <ESS Eval> <Eval region | func | para & step>.
> 
> (ess-eval-region-or-function-or-paragraph-and-step VIS)
> 
> Send the current region if mark is active, if not, send
> function if M-x point is inside one, otherwise the current
> paragraph. After evaluation step to the next code line or to the
> end of region if region was active.
> 
>  Prefix arg VIS toggles visibility of ess-code as for
> `ess-eval-region'.