Getting parent's parametric types parameter

General Usage
3

The point is that somewhere in the code, there is a function like this:

useint(foo::AbstractFoo{Integer}) = factorial(foo.field1)

or any other function, which necessarily needs an Integer as field1. As I have a lot of Foos, I would like to make sure that I do not make some sort of ‘typo’ and create

struct OneMoreFoo <: AbstractFoo{Integer}
  field1::Float64
end

by mistake. Therefore I am looking for a coding pattern, which disallows this.

While your solution does solve the issue, SomeFoo is actually a parametric type, while I would like to have it parameter-less.

Maybe the cleanest solution is to create a macro, which does this for me.