Add a changelog

Author: penelopeysm

HISTORY.md

@@ -32,9 +32,14 @@ You should not need to use these directly, please use `AbstractPPL.condition` an
 
 Removed the method `returned(::Model, values, keys)`; please use `returned(::Model, ::AbstractDict{<:VarName})` instead.
 
+The unexported functions `supports_varname_indexing(chain)`, `getindex_varname(chain)`, and `varnames(chain)` have been removed.
+
 The method `DynamicPPL.init` (for implementing `AbstractInitStrategy`) now has a different signature: it must return a tuple of the generated value, plus a transform function that maps it back to unlinked space.
 This is a generalisation of the previous behaviour, where `init` would always return an unlinked value (in effect forcing the transform to be the identity function).
 
+The family of functions `returned(model, chain)`, along with the same signatures of `pointwise_logdensities`, `logjoint`, `loglikelihood`, and `logprior`, have been changed such that if the chain does not contain all variables in the model, an error is thrown.
+Previously the behaviour would have been to sample missing variables.
+
 ## 0.38.9
 
 Remove warning when using Enzyme as the AD backend.