Add distribution wrappers from Turing

Author: phipsgabler

src/DynamicPPL.jl

@@ -90,6 +90,7 @@ include("selector.jl")
 include("model.jl")
 include("sampler.jl")
 include("varname.jl")
+include("distribution_wrappers.jl")
 include("contexts.jl")
 include("varinfo.jl")
 include("compiler.jl")

src/distribution_wrappers.jl

@@ -0,0 +1,38 @@
+import Distributions: 
+
+"""
+A named distribution that carries the name of the random variable with it.
+"""
+struct NamedDist{
+    variate, 
+    support, 
+    Td <: Distribution{variate, support}, 
+    Tn
+} <: Distribution{variate, support}
+    dist::Td
+    name::Tn
+end
+
+
+struct NoDist{
+    variate, 
+    support, 
+    Td <: Distribution{variate, support}
+} <: Distribution{variate, support}
+    dist::Td
+end
+NoDist(dist::NamedDist) = NamedDist(NoDist(dist.dist), dist.name)
+
+Distributions.rand(d::NoDist) = rand(d.dist)
+Distributions.logpdf(d::NoDist{<:Univariate}, ::Real) = 0
+Distributions.logpdf(d::NoDist{<:Multivariate}, ::AbstractVector{<:Real}) = 0
+function Distributions.logpdf(d::NoDist{<:Multivariate}, x::AbstractMatrix{<:Real})
+    return zeros(Int, size(x, 2))
+end
+Distributions.logpdf(d::NoDist{<:Matrixvariate}, ::AbstractMatrix{<:Real}) = 0
+Bijectors.logpdf_with_trans(d::NoDist{<:Univariate}, ::Real) = 0
+Bijectors.logpdf_with_trans(d::NoDist{<:Multivariate}, ::AbstractVector{<:Real}) = 0
+function Bijectors.logpdf_with_trans(d::NoDist{<:Multivariate}, x::AbstractMatrix{<:Real})
+    return zeros(Int, size(x, 2))
+end
+Bijectors.logpdf_with_trans(d::NoDist{<:Matrixvariate}, ::AbstractMatrix{<:Real}) = 0