[Merged by Bors] - Fixed fallback for observe

[torfjelde]

In the recent breaking release we mistakenly removed the call to observe(::AbstractSampler, right left, vi) as a fallback for DefaultContext, leading to certain sampler breaking in Turing (TuringLang/Turing.jl#1636).

This PR adds back a proper fallback, making overloads such as https://github.com/TuringLang/Turing.jl/blob/tor%2Fdppl-update/src/inference/AdvancedSMC.jl#L353-L356 work as before 0.11.

[devmotion]

Seems fine as long as there is a fallback without samplers and you don't have to implement these methods if not needed. Seems this is the case with the additional observe fallback 👍

Another question, is tilde_observe and observe consistent with dot_tilde_observe and dot_observe?

[torfjelde]

I just tested it locally, and things are working now 👍

Seems fine as long as there is a fallback without samplers and you don't have to implement these methods if not needed. Seems this is the case with the additional observe fallback +1

Exactly, so this PR doesn't do anything other than allow samplers to specify certain observe behavior.

Another question, is tilde_observe and observe consistent with dot_tilde_observe and dot_observe?

And yes it is. I had already done this for dot_observe, but had messed it up for observe. But I just simplified the generic impl of dot_observe a bit now while I was at it.

[torfjelde]

bors r+

[bors]

Pull request successfully merged into master.

Build succeeded:

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• test (1.3, macOS-latest, x64, 1)
• test (1.3, macOS-latest, x64, 2)
• test (1.3, ubuntu-latest, x64, 1)
• test (1.3, ubuntu-latest, x64, 2)
• test (1.3, ubuntu-latest, x86, 1)
• test (1.3, ubuntu-latest, x86, 2)
• test (1.3, windows-latest, x64, 1)
• test (1.3, windows-latest, x64, 2)
• test (1, macOS-latest, x64, 1)
• test (1, macOS-latest, x64, 2)
• test (1, ubuntu-latest, x64, 1)
• test (1, ubuntu-latest, x64, 2)
• test (1, ubuntu-latest, x86, 1)
• test (1, ubuntu-latest, x86, 2)
• test (1, windows-latest, x64, 1)
• test (1, windows-latest, x64, 2)
• Turing.jl