Inconsistency in `product_distribution` argument

[dmetivie]

Following the discussion on discourse, it seems that the product_distribution does different things based on the argument being a vector or not. Does it call the old Product interface.

Which of the following is the correct way to define a product? The first option returns the most satisfying and detailed type.

# v0.25.65 and above
julia> typeof(product_distribution([Gamma(),Normal()]...))
Distributions.ProductDistribution{1, 0, Tuple{Gamma{Float64}, Normal{Float64}}, Continuous, Float64}

julia> typeof(product_distribution([Gamma(),Normal()]))
Product{Continuous, Distribution{Univariate, Continuous}, Vector{Distribution{Univariate, Continuous}}}
# -> use the old (depreacated) Product interface?

The doc suggests an array should be used (hence the second option, where type is not fully returned).

[devmotion]

Yes, this is expected. ProductDistribution is relatively new and an internal thing, users are supposed to only use product_distribution, analogously to truncated etc. Changing product_distribution(::Vector{<:UnivariateDistribution}) from returning a Product to a ProductDistribution would have been breaking, so only previously unsupported arguments return a ProductDistribution until a new breaking release of Distributions is made (which I don't expect anytime in the near future).

[dmetivie]

Thanks for the clarification!