Update the currently buggy and incorrect tilde overloads in mh.jl (#…

…2360)

src/mcmc/mh.jl

@@ -442,42 +442,45 @@ end
 ####
 #### Compiler interface, i.e. tilde operators.
 ####
-function DynamicPPL.assume(rng, spl::Sampler{<:MH}, dist::Distribution, vn::VarName, vi)
+function DynamicPPL.assume(
+    rng::Random.AbstractRNG, spl::Sampler{<:MH}, dist::Distribution, vn::VarName, vi
+)
+    # Just defer to `SampleFromPrior`.
+    retval = DynamicPPL.assume(rng, SampleFromPrior(), dist, vn, vi)
+    # Update the Gibbs IDs because they might have been assigned in the `SampleFromPrior` call.
     DynamicPPL.updategid!(vi, vn, spl)
-    r = vi[vn]
-    return r, logpdf_with_trans(dist, r, istrans(vi, vn)), vi
+    # Return.
+    return retval
 end
 
 function DynamicPPL.dot_assume(
     rng,
     spl::Sampler{<:MH},
     dist::MultivariateDistribution,
-    vn::VarName,
+    vns::AbstractVector{<:VarName},
     var::AbstractMatrix,
-    vi,
+    vi::AbstractVarInfo,
 )
-    @assert dim(dist) == size(var, 1)
-    getvn = i -> VarName(vn, vn.indexing * "[:,$i]")
-    vns = getvn.(1:size(var, 2))
-    DynamicPPL.updategid!.(Ref(vi), vns, Ref(spl))
-    r = vi[vns]
-    var .= r
-    return var, sum(logpdf_with_trans(dist, r, istrans(vi, vns[1]))), vi
+    # Just defer to `SampleFromPrior`.
+    retval = DynamicPPL.dot_assume(rng, SampleFromPrior(), dist, vns[1], var, vi)
+    # Update the Gibbs IDs because they might have been assigned in the `SampleFromPrior` call.
+    DynamicPPL.updategid!.((vi,), vns, (spl,))
+    # Return.
+    return retval
 end
 function DynamicPPL.dot_assume(
     rng,
     spl::Sampler{<:MH},
     dists::Union{Distribution,AbstractArray{<:Distribution}},
-    vn::VarName,
+    vns::AbstractArray{<:VarName},
     var::AbstractArray,
-    vi,
+    vi::AbstractVarInfo,
 )
-    getvn = ind -> VarName(vn, vn.indexing * "[" * join(Tuple(ind), ",") * "]")
-    vns = getvn.(CartesianIndices(var))
-    DynamicPPL.updategid!.(Ref(vi), vns, Ref(spl))
-    r = reshape(vi[vec(vns)], size(var))
-    var .= r
-    return var, sum(logpdf_with_trans.(dists, r, istrans(vi, vns[1]))), vi
+    # Just defer to `SampleFromPrior`.
+    retval = DynamicPPL.dot_assume(rng, SampleFromPrior(), dists, vns, var, vi)
+    # Update the Gibbs IDs because they might have been assigned in the `SampleFromPrior` call.
+    DynamicPPL.updategid!.((vi,), vns, (spl,))
+    return retval
 end
 
 function DynamicPPL.observe(spl::Sampler{<:MH}, d::Distribution, value, vi)