Hi everyone!

I am trying to construct a container that holds vectors of different probabilities (but they are all either multi- or univariate). This container is used to store prior distributions of parameter I use in another struct, so one of the fields is a Dict that maps symbols to Vectors of distributions. The following could be used for a concrete type definition:

```
using Distributions
using BenchmarkTools
#3 - Issue for concrete types
typeof( [Normal(), Normal() ] ) #Vector{Normal{Float64}}
typeof( [Gamma(1,2), Normal() ] ) #Vector{Distribution{Univariate, Continuous}}
typeof( [Normal(), Normal() ] ) <: Vector{<:Distribution{Univariate} } #true
typeof( [Gamma(1,2), Normal() ] ) <: Vector{<:Distribution{Univariate} } #true
typeof( [Poisson(1), Normal() ] ) <: Vector{<:Distribution{Univariate} } #true
#all combinations above are subtype of Vector{<:Distribution{Univariate} }
Dict(:μ => [Normal(1,2), Normal(3,4)],
:δ => [Gamma(1,1), Exponential(1)] ) #Dict Symbol -> Array{T,1} where T
#but somehow here no concrete type is assigned
```

So as a first guess I would assign the following container:

```
struct Prior01{A<:VariateForm}
α :: Dict{Symbol, Vector{<:Distribution{A}} }
end
# Concretely typed not working
p01 = Prior01( Dict(:μ => [Normal(1,2), Gamma(3,4)],
:δ => [Gamma(1,1), Gamma(1,1)] ) )
```

For some reasons I do not understand, this is not working - so a non-concretely typed version so far is the best I could do:

```
struct Prior02
α :: Dict{Symbol, <:Vector{C} where {C} }
end
#Working but no concrete type
p02 = Prior02( Dict(:μ => [Gamma(1,2), Gamma(3,4)],
:δ => [Gamma(1,1), Gamma(1,1)] ) )
```

**Question: Does anyone know why I cannot get the concretely typed container working even though the Vectors of Distributions shown above have a common supertype?**

Best regards,