I agree this behavior is confusing; I also think it would be more intuitive to alias the current module into itself. I can’t explain exactly why, it’s just less surprising for some reason.

With that said, obviously there is no changing this now, so it is what it is.

Structs are just maps with an extra __struct__ key set to the module name. Functions are imported into the scope, but structs are not. You can only alias the module name.

Note however that defining a nested module aliases that module within the parent, so you can do this:

defmodule A do
  defmodule B do
    defstruct [:foo, :bar]
  end
  def foo(%B{}), do: true
end

Even though the actual name of B is A.B. Which only makes it more confusing tbh.

Yes, but it’s even more fundamental than that. The struct “name” is a module name. Even if you were not creating a struct, but in any module you cannot refer to the current module by the leaf part of its name. For example, if you were writing any function within module Foo.Bar you cannot use Bar by itself. You’d have the same 3 options I mentioned.

Just to put what @gregvaughn another way (which is what helped me) is that Elixir doesn’t technically have submodules. The . is a bit of an illusion and is only meaningful for constructs like alias, otherwise it’s just like any other character in a module name. Foo and Foo.Bar have absolutely no relation as far as the VM is concerned.