tag(s) with functionalities from `body<-`, `formals<-` and `trace`

[moodymudskipper]

trace is not a proper function operator but it has interesting features, we should not use trace though, but it could be named tracing and use body<- borrowing the arguments from trace.

to modify formals we can either have a different function integrate it in, then we need to decide if the name tracing is general enough :

• why it would not be : tracing is not about editing formals, if I just want to edit formals, using a function named tracing is awkward
• why it would be : you rarely would want to edit formals without editing the body, so the formal editing feature is just a handy addon

We can probably go on with tracing, with parameters :

• tracer : as in trace
• at : as in trace
• exit : as in trace
• formals : NULL by default (use alist() orlist()` to assign empty formals),
• body : NULL by default, (use quote() to assaign empty body), either a body replacement or a function/formula to apply on the existing body, for example I might want to substitute all list calls by rlang::list2 calls to support quasi quotation etc...

for this last example we'd need to see how we do it, maybe we need a helper function tu substitute stuff while keeping a simple syntax.

[moodymudskipper]

Better to be able to add or remove formals like in tag or tag_adverb

[moodymudskipper]

tracing is done, formals functionalities will be handled by the modifying_args family