While the `B` object inherited most of `A`, they don't have the same size, so you can't store them in the same array/seq.
What you might want to do, is to use `ref object`, which is a pointer so they
can be placed on the same array/ref
type
A = ref object of RootRef
x: int
B = ref object of A
y: int
X = object
values: seq[A]
var myX = X(values: @[])
myX.values.add B(x:0, y:5)
Run
