What are the scoping rule for Elixir alias?

The scoping rule says, that the alias A.B.C will have an effect from now on, until the current block gets closed, thats why you can define an alias in a function only.

So there is no directories involved that elixir would look at/in…

So in A.B.C, C refers only to C in that module and nowhere else?

A.B.C is a module name, alias A.B.C creates an alias, making C identical to A.B.C.

From the Programming Phoenix Book

accounts.ex

defmodule Rumbl.Accounts do

    alias Rumbl.Accounts.User

end

Rumbl.Accounts.User is located in .\accounts\user.ex relative to where accounts.ex is. So to me defmodule Rumbl.Accounts appears to have look for Rumbl.Accounts.User beyond its own directory?

Elixir will look up nowhere, as all modules are compiled to flat structure, so in the end, there is no directories, just modules. And alias is only naming alias, it doesn’t do any lookup (aka - you can alias non-existent module as well).

So it looks through all modules?

Module names and file paths are not related in Elixir. All files in the project (in the directories specified to the compiler) are compiled and a module can be in any path there. It is only a convention to have module names matching your directory hierarchy.

No, it does nothing except providing shorter alias for the module name.

There is no looking up of sourcefiles or anything.

There is not even something that forces you to use folders or have files named in a certain way.

The compiler “remembers” all defmodules it has seen so far, and will therefore know which modules exist.

But still alias/2 does not verify if a given module exists that you want to alias. It just makes, that every occurence of User (based from the rumble example) will be expanded to Rumbl.Accounts.User before compiling into byte code.

so its up to compiler to catch if the aliased Rumbl.Accounts.User does not exist?