Can defined a nested module called Elixir, closes #858

Author: José Valim

lib/elixir/src/elixir_macros.erl

@@ -321,7 +321,7 @@ rewrite_case_clauses(Clauses) ->
 expand_module(Raw, Module, #elixir_scope{module=Nesting}) when is_atom(Raw); Nesting == nil ->
   Module;
 
-expand_module({ '__aliases__', _, _ } = Alias, Module, S) ->
+expand_module({ '__aliases__', _, List } = Alias, Module, S) when List /= ['Elixir'] ->
   case elixir_aliases:expand(Alias, S#elixir_scope.aliases, S#elixir_scope.macro_aliases) of
     Atom when is_atom(Atom) ->
       Module;

lib/elixir/test/elixir/kernel/alias_test.exs

@@ -26,6 +26,14 @@ defmodule Kernel.AliasTest do
     alias List, as: Nested
     assert Nested.flatten([[13]]) == [13]
   end
+
+  defmodule Elixir do
+    def sample, do: 1
+  end
+
+  test :nested_elixir_alias do
+    assert Kernel.AliasTest.Elixir.sample == 1
+  end
 end
 
 defmodule Kernel.AliasNestingGenerator do