New model specification does not allow complex expressions for input arguments, only ::Symbol

[bvdmitri]

E.g. this fails

@model function coin_toss_model(x, n::Int)
    θ ~ Beta(4.0, 8.0)
    for i in 1:n
        x[i] ~ Bernoulli(θ)
    end
end

[bvdmitri]

Another example, which throws a cryptic error message on model creation, but @model macro does not complain

 GraphPPL.@model function coin_toss_model(x, n + a)
    θ ~ Beta(4.0, 8.0)
    for i in 1:n
        x[i] ~ Bernoulli(θ)
    end
end