Help with circular type/inner constructor

General Usage
8

Ah, sorry, your constructor for the parametric type needs to be TDatumVal{T}() where T = ....

Here’s a more similar example:

mutable struct Foo{T}
    x::Union{Nothing, T}
    Foo{T}() where T = new(nothing)
end

Foo() = Foo{Bar}()

mutable struct Bar
    x::Foo{Bar}
end

f = Foo()
f.x = Bar(f)

I’m not sure how you’re constructing your type, but you’ll have to make sure you either explicitly create it with TDatumVal{TDatum}() or create a new method (like in my example above) that fills in the type parameter for you.