It is not possible to instantiate an empty array in the model macro

[bvdmitri]

Consider the following

@model function huh()
    a = []
end

This might be useful to populate some intermediate values for later usage inside the model, but this currently fails with

LoadError: BoundsError: attempt to access 0-element Vector{Any} at index [1]
in expression starting at In[23]:1

Stacktrace:
  [1] throw_boundserror(A::Vector{Any}, I::Tuple{Int64})
    @ Base ./essentials.jl:14
  [2] getindex
    @ ./essentials.jl:916 [inlined]
  [3] (::GraphPPL.var"#123#124")(x::Expr)
    @ GraphPPL ~/.julia/dev/GraphPPL.jl/src/model_macro.jl:268
  [4] guarded_walk
    @ ~/.julia/dev/GraphPPL.jl/src/model_macro.jl:14 [inlined]
  [5] (::GraphPPL.var"#105#106"{GraphPPL.guarded_walk{GraphPPL.var"#123#124"}, GraphPPL.var"#115#116"{typeof(GraphPPL.convert_to_kwargs_expression)}})(x::Expr)
    @ GraphPPL ~/.julia/dev/GraphPPL.jl/src/model_macro.jl:14
  [6] iterate
    @ ./generator.jl:48 [inlined]
  [7] collect_to!(dest::Vector{Symbol}, itr::Base.Generator{Vector{Any}, GraphPPL.var"#105#106"{GraphPPL.guarded_walk{GraphPPL.var"#123#124"}, GraphPPL.var"#115#116"{typeof(GraphPPL.convert_to_kwargs_expression)}}}, offs::Int64, st::Int64)
    @ Base ./array.jl:849
  [8] collect_to_with_first!(dest::Vector{Symbol}, v1::Symbol, itr::Base.Generator{Vector{Any}, GraphPPL.var"#105#106"{GraphPPL.guarded_walk{GraphPPL.var"#123#124"}, GraphPPL.var"#115#116"{typeof(GraphPPL.convert_to_kwargs_expression)}}}, st::Int64)

This works fine

@model function huhhhh()
    a = Any[]
end