Xianda Sun

@torfjelde @yebai @devmotion does this PR make sense? If this is desirable, then I'll extend tests in https://github.com/TuringLang/DynamicPPL.jl/blob/master/test/sampler.jl.

@torfjelde is my understanding of SimpleVarInfo with NamedTuple correct at https://github.com/TuringLang/DynamicPPL.jl/pull/606#issuecomment-2111867290?

> we need to make it possible to use the NamedTuple version I agree. Other than performance, I thought SimpleVarInfo is also less error-prone for AD (correct me if wrong),...

Let me look into it and see if I can make NamedTuple variant of SimpleVarInfo work, or at least a clear TODOs

Sounds good. I started this as a quick and dirty prototype, it definitely needs more work, until we can justify complicating the interface.

@yebai @devmotion @cpfiffer

I am for adding a `condition` interface, should we upstream this from `AbstractPPL`?

Okay, now `condition` and `decondition` are moved to AbstractMCMC from AbstractPPL. Do we want [`fix`](https://github.com/TuringLang/DynamicPPL.jl/blob/dfdc155b191764db53e96a3e52c9a8d0f46e09ac/src/model.jl#L475) here?

@devmotion @yebai @torfjelde @mhauru a penny for your thoughts?

I removed `condition` (and `decondition`) and use the `public` keyword for the new interface functions. The latter will technically change the interface, so I bumped the minor version. I also...