Background

Let’s say I have a TypedStruct that has some common fields:

typedstruct do
    @typedoc "A product."

    field(:item_id, String.t())
    field(:name, String.t())
    field(:brand, String.t())
  end

This is a product and because products can go on sale, I have another TypedStruct:

typedstruct do
    @typedoc "A sale."

    field(:item_id, String.t())
    field(:name, String.t())
    field(:brand, String.t())
    field(:price, number)
    field(:discount, boolean)
  end

Issue

Now, you are probably seeing there is some duplication here. Since a sale is a product with extra info, some of the fields are replicated.

A first attempt at a solution could be something like this:

typedstruct do
    @typedoc "A sale."

    field(:product, Product.t())
    field(:price, number)
    field(:discount, boolean)
  end

However, my use case does not allow for this. I must have a struct with exactly the same fields as Product.t() and a few extra. I cannot simply smash a product field into my sales struct.

Question

• Is there a way to compose types using TypedStruct (or normal structs?)
• If not, what do you think would be the solution with the least amount of copy/pasting for this issue?