Ensure aliases defined in macros do not leak

Author: José Valim

lib/elixir/src/elixir_dispatch.erl

@@ -218,15 +218,29 @@ translate_expansion(Meta, Receiver, Tree, S) ->
   New  = S#elixir_scope.macro_counter + 1,
 
   try
-    elixir_translator:translate_each(
+    { TE, TS } = elixir_translator:translate_each(
       elixir_quote:linify_with_context_counter(Line, { Receiver, New }, Tree),
       S#elixir_scope{macro_counter=New}
-    )
+    ),
+    { TE,
+      TS#elixir_scope{
+        macro_macros=S#elixir_scope.macro_macros,
+        macro_aliases=merge_aliases(TS, S),
+        macro_functions=S#elixir_scope.macro_functions
+      } }
   catch
     Kind:Reason ->
       erlang:raise(Kind, Reason, prune_stacktrace(mfa(Line, S), erlang:get_stacktrace(), nil))
   end.
 
+%% We only keep aliases from module definitions.
+%% All others are discarded straight-away.
+merge_aliases(#elixir_scope{context_modules=Context, macro_aliases=New},
+              #elixir_scope{macro_aliases=Old}) ->
+  ContextAliases = [{ N, O } || { N, O } <- New, lists:member(O, Context)],
+  lists:foldl(fun({ N, O }, Acc) -> orddict:store(N, O, Acc) end,
+              ContextAliases, Old).
+
 mfa(Line, #elixir_scope{module=nil} = S) ->
   { elixir_compiler, '__FILE__', 2, location(Line, S) };
 

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

@@ -93,3 +93,40 @@ defmodule Kernel.AliasMacroNestingTest do
     assert Parent.Child.b.message == "ok"
   end
 end
+
+# Test case extracted from using records with aliases
+# and @before_compile. We are basically testing that
+# macro aliases are not leaking from the macro.
+
+defmodule Macro.AliasTest.Definer do
+  defmacro __using__(_options) do
+    quote do
+      @before_compile unquote(__MODULE__)
+    end
+  end
+
+  defmacro __before_compile__(_env) do
+    quote do
+      defrecord Record, [foo: :bar]
+    end
+  end
+end
+
+defmodule Macro.AliasTest.Aliaser do
+  defmacro __using__(_options) do
+    quote do
+      alias Some.Record
+    end
+  end
+end
+
+defmodule Macro.AliasTest.User do
+  use ExUnit.Case, async: true
+
+  use Macro.AliasTest.Definer
+  use Macro.AliasTest.Aliaser
+
+  test "has a record defined from after compile" do
+    assert is_tuple Macro.AliasTest.User.Record.new
+  end
+end