Aliases for defmodule also works for raw atoms

Author: José Valim

lib/elixir/src/elixir_aliases.erl

@@ -1,5 +1,5 @@
 -module(elixir_aliases).
--export([first/1, last/1, concat/1, safe_concat/1, lookup/2,
+-export([nesting/2, last/1, concat/1, safe_concat/1, lookup/2,
   format_error/1, ensure_loaded/3, expand/2]).
 -include("elixir.hrl").
 -compile({parse_transform, elixir_transform}).
@@ -39,17 +39,6 @@ ensure_loaded(Line, Ref, S) ->
       elixir_errors:form_error(Line, S#elixir_scope.file, ?MODULE, { Kind, Ref })
   end.
 
-%% Receives an atom and returns the first alias.
-
-first(Atom) ->
-  First = first(atom_to_list(Atom), []),
-  list_to_atom("Elixir-" ++ First).
-
-first("Elixir-" ++ Rest, []) -> first(Rest, []);
-first([$-|_], Acc) -> lists:reverse(Acc);
-first([H|T], Acc) -> first(T, [H|Acc]);
-first([], Acc) -> lists:reverse(Acc).
-
 %% Receives an atom and returns the last alias.
 
 last(Atom) ->
@@ -60,6 +49,25 @@ last([$-|_], Acc) -> Acc;
 last([H|T], Acc) -> last(T, [H|Acc]);
 last([], Acc) -> Acc.
 
+%% Returns the nesting between two aliases.
+
+nesting(nil, _Full) -> false;
+
+nesting(Prefix, Full) ->
+  PrefixList = list_nesting(Prefix),
+  FullList   = list_nesting(Full),
+
+  (PrefixList /= []) andalso
+    (PrefixList /= FullList) andalso
+    lists:prefix(PrefixList, FullList) andalso
+    binary_to_atom(<<"Elixir-", (hd(FullList -- PrefixList))/binary>>, utf8).
+
+list_nesting(Atom) ->
+  case binary:split(atom_to_binary(Atom, utf8), <<$->>, [global]) of
+    [<<"Elixir">>|T] -> T;
+    _ -> []
+  end.
+
 %% Receives a list of atoms representing modules
 %% and concatenate them.
 

lib/elixir/src/elixir_macros.erl

@@ -196,19 +196,16 @@ translate({defmodule, Meta, [Ref, KV]}, S) ->
 
   { FRef, FS } = case TRef of
     { atom, _, Module } ->
-      NewModule = module_ref(Ref, Module, S#elixir_scope.module),
-
-      RS = case Module == NewModule of
-        true  -> S;
-        false ->
-          element(2, translate_each({
-            alias, Meta, [NewModule, [{as, elixir_aliases:first(Module)}]]
-          }, S))
+      FullModule = module_ref(Ref, Module, S#elixir_scope.module),
+
+      RS = case elixir_aliases:nesting(S#elixir_scope.module, FullModule) of
+        false -> S;
+        Alias -> element(2, translate_each({ alias, Meta, [FullModule, [{ as, Alias }]] }, S))
       end,
 
       {
-        { atom, Meta, NewModule },
-        RS#elixir_scope{scheduled=[NewModule|S#elixir_scope.scheduled]}
+        { atom, Meta, FullModule },
+        RS#elixir_scope{scheduled=[FullModule|S#elixir_scope.scheduled]}
       };
     _ ->
       { TRef, S }

lib/elixir/test/elixir/module_test.exs

@@ -114,6 +114,14 @@ defmodule ModuleTest do
     assert OverridableWithBeforeCompile.constant == 1
   end
 
+  test :alias_with_raw_atom do
+    defmodule :"Elixir-ModuleTest-RawModule" do
+      def hello, do: :world
+    end
+
+    assert RawModule.hello == :world
+  end
+
   defmacro __before_compile__(_) do
     quote do
       def constant, do: 1