Remove 3-argument {_,}evaluate!!; clean up submodel code

[penelopeysm]

This PR:

• removes the one last usage of evaluate!!(model, varinfo, context) in the DynamicPPL codebase
• removes _evaluate!!(model, varinfo, context) as this method was only being used for submodels

In return, it introduces:

• _evaluate!!(submodel, varinfo, context, left). Yes, yes, I basically moved the implementation from one place to the other; but the whole point is that this was special-case behaviour that was only needed for submodels, so this at least makes it clearer.

It also removes a lot of wrapper code for submodels. For example, we don't have this ReturnedModelWrapper and Sampleable thing any more, instead, there's just Submodel which wraps a model.

I personally don't see the need for more than one layer of indirection for submodels (in terms of the data structure, the only difference between a submodel and a model is that the submodel carries information about whether it should be auto-prefixed). I had mucked around with this before in #815 and I didn't find any real problems with removing the wrappers there (in fact in that PR I went one step further and removed all wrappers, but that would have made it impossible to opt-out of prefixing and that's Bad(TM)).

I didn't add any new tests, but test/submodel.jl already contains quite extensive tests to make sure that everything behaves and it passes these tests so I'm quite happy.

#959 needs to be merged first. Done.

Follow-up from #952

Closes #720 (for good)

[github-actions]

Benchmark Report for Commit aaf0bc6

Computer Information

Julia Version 1.11.5
Commit 760b2e5b739 (2025-04-14 06:53 UTC)
Build Info:
  Official https://julialang.org/ release
Platform Info:
  OS: Linux (x86_64-linux-gnu)
  CPU: 4 × AMD EPYC 7763 64-Core Processor
  WORD_SIZE: 64
  LLVM: libLLVM-16.0.6 (ORCJIT, znver3)
Threads: 1 default, 0 interactive, 1 GC (on 4 virtual cores)

Benchmark Results

|                 Model | Dimension |  AD Backend |      VarInfo Type | Linked | Eval Time / Ref Time | AD Time / Eval Time |
|-----------------------|-----------|-------------|-------------------|--------|----------------------|---------------------|
| Simple assume observe |         1 | forwarddiff |             typed |  false |                  8.7 |                 1.6 |
|           Smorgasbord |       201 | forwarddiff |             typed |  false |                670.9 |                42.5 |
|           Smorgasbord |       201 | forwarddiff | simple_namedtuple |   true |                429.6 |                50.9 |
|           Smorgasbord |       201 | forwarddiff |           untyped |   true |               1008.0 |                35.3 |
|           Smorgasbord |       201 | forwarddiff |       simple_dict |   true |               6377.6 |                25.0 |
|           Smorgasbord |       201 | reversediff |             typed |   true |               1495.3 |                27.5 |
|           Smorgasbord |       201 |    mooncake |             typed |   true |               1025.4 |                 4.3 |
|    Loop univariate 1k |      1000 |    mooncake |             typed |   true |               5851.1 |                 4.0 |
|       Multivariate 1k |      1000 |    mooncake |             typed |   true |               1000.1 |                 9.1 |
|   Loop univariate 10k |     10000 |    mooncake |             typed |   true |              65756.9 |                 3.6 |
|      Multivariate 10k |     10000 |    mooncake |             typed |   true |               8742.1 |                 9.9 |
|               Dynamic |        10 |    mooncake |             typed |   true |                139.7 |                11.9 |
|              Submodel |         1 |    mooncake |             typed |   true |                 13.7 |                 6.0 |
|                   LDA |        12 | reversediff |             typed |   true |               1697.6 |                 2.8 |

[codecov]

Codecov Report

Attention: Patch coverage is 95.65217% with 1 line in your changes missing coverage. Please review.

Project coverage is 82.77%. Comparing base (7f20709) to head (aaf0bc6).
Report is 1 commits behind head on breaking.

Files with missing lines	Patch %	Lines
src/context_implementations.jl	83.33%	1 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##           breaking     #960      +/-   ##
============================================
- Coverage     82.85%   82.77%   -0.09%     
============================================
  Files            38       38              
  Lines          4031     4011      -20     
============================================
- Hits           3340     3320      -20     
  Misses          691      691              

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[github-actions]

DynamicPPL.jl documentation for PR #960 is available at:
https://TuringLang.github.io/DynamicPPL.jl/previews/PR960/

[mhauru]

Seems good to me, just had a few questions to check/inform myself.

[mhauru]

Wasn't this deprecation added just a few weeks ago? Or am I mixing this with something else?

[penelopeysm]

Same as above; but I don't know, I might be open to leaving a helpful error message in (i.e., maybe it shouldn't continue behaving as it does, but it should throw an error message that guides people towards the right answer)? I do know that upstream packages use evaluate!! even though it is internal, pretty sure I've seen it in Pigeons.jl for example, and Turing itself obviously uses evaluate!! quite a lot.

[mhauru]

A manually crafted, more informative error message sounds good to me.

[penelopeysm]

I added an error hint in src/DynamicPPL.jl, so now this happens:

julia> using DynamicPPL, Distributions

julia> @model f() = x ~ Normal()
f (generic function with 2 methods)

julia> m = f(); v = VarInfo(m); c = DefaultContext()
DefaultContext()

julia> DynamicPPL.evaluate!!(m, v, c)
ERROR: MethodError: no method matching evaluate!!(::Model{…}, ::VarInfo{…}, ::DefaultContext)
The function `evaluate!!` exists, but no method is defined for this combination of argument types.

The method `evaluate!!(model, varinfo, new_ctx)` has been removed. Instead, you should store the `new_ctx` in the `model.context` field using `new_model = contextualize(model, new_ctx)`, and then call `evaluate!!(new_model, varinfo)` on the new model. (Note that, if the model already contained a non-default context, you will need to wrap the existing context.)

Closest candidates are:
  evaluate!!(::Model, ::AbstractVarInfo)
   @ DynamicPPL ~/ppl/dppl/src/model.jl:868

Stacktrace:
 [1] top-level scope
   @ REPL[10]:1
Some type information was truncated. Use `show(err)` to see complete types.

[mhauru]

Thanks @penelopeysm! I didn't know about adding error hints, that's neat.