[RFC] Distinguishing tilde methods for passing variable names to both variants

[phipsgabler]

Currently, there are essentially two methods of tilde (resp. dot_tilde) -- one for assume, one for observe. These are only distinguished by the assume variant being passed the VarName (and indices).

Can we just have different functions for them, like tilde_observe and tilde_assume, with both taking the VarName? The motivation is that I want to use IRTracker for dependency analysis, for which having the name would really be a nice (i.e., necessary) thing.

The name of an observed variable would just be ignored in all existing implementations, but who knows, maybe it can become useful. I think both methods could actually fall back to tilde for transition. Do any other packages besides Turing itself use them at all?

BTW: what exactly is the reason that assume/observe are not directly produced from the model macro?

[phipsgabler]

Of course I'll also implement this if the answer is yes!

[phipsgabler]

I have made a branch that implements this in a backwards-compatible way, if you wan't to take a look: master...phipsgabler:phg/split_tilde.