Ensure defoverridable is not order dependant, closes #2615

Author: José Valim

lib/elixir/lib/module/locals_tracker.ex

@@ -259,10 +259,9 @@ defmodule Module.LocalsTracker do
   end
 
   def handle_call({:yank, local}, _from, {d, _} = state) do
-    in_vertices  = :digraph.in_neighbours(d, local)
     out_vertices = :digraph.out_neighbours(d, local)
-    :digraph.del_vertex(d, local)
-    {:reply, {in_vertices, out_vertices}, state}
+    :digraph.del_edges(d, :digraph.out_edges(d, local))
+    {:reply, {[], out_vertices}, state}
   end
 
   def handle_call(:digraph, _from, {d, _} = state) do
@@ -300,9 +299,7 @@ defmodule Module.LocalsTracker do
     {:noreply, state}
   end
 
-  def handle_cast({:reattach, kind, tuple, {in_neigh, out_neigh}}, {d, _} = state) do
-    handle_add_definition(d, kind, tuple)
-
+  def handle_cast({:reattach, _kind, tuple, {in_neigh, out_neigh}}, {d, _} = state) do
     for from <- in_neigh do
       :digraph.add_vertex(d, from)
       replace_edge!(d, from, tuple)

lib/elixir/test/elixir/kernel/overridable_test.exs

@@ -96,6 +96,27 @@ defmodule Kernel.Overridable do
 end
 
 defmodule Kernel.OverridableTest do
+  defmodule OverridableOrder do
+    def not_private(str) do
+      process_url(str)
+    end
+
+    defp process_url(_str) do
+      :first
+    end
+
+    # There was a bug where the order in which we removed
+    # overridable expressions lead to errors. This module
+    # aims to guarantee removing process_url/1 before we
+    # remove the function that depends on it does not cause
+    # errors. If it compiles, it works!
+    defoverridable [process_url: 1, not_private: 1]
+
+    defp process_url(_str) do
+      :second
+    end
+  end
+
   require Kernel.Overridable, as: Overridable
   use ExUnit.Case, async: true