struct_defaults.ex

defmodule StructDefaults do
  defmacro __using__(opts) do
    name = case opts[:name] do
      nil -> __CALLER__.module |> Module.split() |> List.last()
      b when is_binary(b) -> b
    end
    mod = __CALLER__.module

    quote location: :keep do
      require StructDefaults

      defdelegate([
          fetch(t, k),
          get_and_update(t, k, l)
        ], to: Map)

      defimpl String.Chars, for: unquote(mod) do
        def to_string(u) do
          #TODO: replace with something smarter
          inspect(u)
        end
      end

      defimpl Inspect, for: unquote(mod) do
        import Inspect.Algebra

        def inspect(user, opts) do
          concat ["#", unquote(name), "<", to_doc(Map.from_struct(user) |> Enum.to_list(), opts), ">"]
        end
      end
    end
  end
end

usage_example.ex

defmodule SomeStruct
  defstruct [:a, :b, :c]
  use StructDefaults, name: "SomeOtherNameForSomeStruct"
end