Unmarshaling empty matrix results in ERROR: MethodError: no method matching

[szafna]

Hi
it looks there is an corner case not supported with unmarshal.
It happens where an empty Matrix is unmarshaled. A JSON matrix value [] is parsed to Any[]. Next, the unmarshaling of the form
Unmarshal.unmarshal(Matrix{Int32}, Any[]) returns Any[]. Note that: typeof(Any[]) returns Vector{Any}. However, constructor for Matrix expects the type Matrix{Any}

MWE demonstrates this:

struct test
    id::Int32
    cs::Array{Int32,2} 
end

julia> d1=test(3, reshape([],0,0))
test(3, Matrix{Int32}(undef, 0, 0))

julia> d2=JSON.json(d1)
"{\"id\":3,\"cs\":[]}"

julia> d3=JSON.parse(d2)
Dict{String, Any} with 2 entries:
  "cs" => Any[]
  "id" => 3

julia> d4=Unmarshal.unmarshal(test,d3,true)
test AbstractDict
\--> id <: Int32
\--> cs <: Matrix{Int32}
        Array{Int32, 2}
ERROR: MethodError: no method matching Matrix{Int32}(::Vector{Any})
Closest candidates are:
  Array{T, N}(::AbstractArray{S, N}) where {T, N, S} at C:\Programs\Julia-1.7.0\share\julia\base\array.jl:563
  Matrix{T}(::LinearAlgebra.UpperTriangular) where T at C:\Programs\Julia-1.7.0\share\julia\stdlib\v1.7\LinearAlgebra\src\triangular.jl:177
  Matrix{T}(::LinearAlgebra.UpperHessenberg) where T at C:\Programs\Julia-1.7.0\share\julia\stdlib\v1.7\LinearAlgebra\src\hessenberg.jl:68
  ...

I'd be glad if this could be fixed.

Simon