Perform all side-effect in order in in/2

Author: josevalim

lib/elixir/lib/enum.ex

@@ -2023,11 +2023,16 @@ defmodule Enum do
   operators work by using this function.
   """
   @spec member?(t, element) :: boolean
-  def member?(enumerable, element) when is_list(enumerable) do
+  def member?(enumerable, element) do
+    __in__(element, enumerable)
+  end
+
+  @doc false
+  def __in__(element, enumerable) when is_list(enumerable) do
     :lists.member(element, enumerable)
   end
 
-  def member?(enumerable, element) do
+  def __in__(element, enumerable) do
     case Enumerable.member?(enumerable, element) do
       {:ok, element} when is_boolean(element) ->
         element

lib/elixir/lib/kernel.ex

@@ -4723,7 +4723,7 @@ defmodule Kernel do
             in_var(in_body?, left, &in_range(&1, expand.(first), expand.(last), expand.(step)))
 
           _ when in_body? ->
-            quote(do: Elixir.Enum.member?(unquote(right), unquote(left)))
+            quote(do: Elixir.Enum.__in__(unquote(left), unquote(right)))
 
           _ ->
             raise_on_invalid_args_in_2(right)

lib/elixir/test/elixir/kernel_test.exs

@@ -321,8 +321,6 @@ defmodule KernelTest do
   defp struct_or_map?(arg, name) when is_struct(arg, name) or is_map(arg), do: true
   defp struct_or_map?(_arg, _name), do: false
 
-  defp not_atom(), do: "not atom"
-
   test "is_struct/2" do
     assert delegate_is_struct(%{}, Macro.Env) == false
     assert delegate_is_struct([], Macro.Env) == false
@@ -336,7 +334,7 @@ defmodule KernelTest do
     assert guarded_is_struct(%{}, Macro.Env) == false
 
     assert_raise ArgumentError, "argument error", fn ->
-      is_struct(%{}, not_atom())
+      is_struct(%{}, Process.get(:unused, "not atom"))
     end
   end
 
@@ -417,7 +415,7 @@ defmodule KernelTest do
     assert guarded_is_exception(%{}, RuntimeError) == false
 
     assert_raise ArgumentError, "argument error", fn ->
-      delegate_is_exception(%{}, not_atom())
+      delegate_is_exception(%{}, Process.get(:unused, "not atom"))
     end
   end
 
@@ -594,7 +592,7 @@ defmodule KernelTest do
       assert map_dot(%{field: true})
     end
 
-    test "performs all side-effects" do
+    test "performs all side-effects in order" do
       assert 1 in [1, send(self(), 2)]
       assert_received 2
 
@@ -603,9 +601,17 @@ defmodule KernelTest do
 
       assert 2 in [1 | send(self(), [2])]
       assert_received [2]
+
+      send(self(), :first) in send(self(), [:first, :second, :third])
+      assert Process.info(self(), :messages) == {:messages, [:first, [:first, :second, :third]]}
+      assert_received :first
+      assert_received [:first, :second, :third]
+
+      send(self(), 0) in send(self(), -2)..send(self(), 2)//send(self(), 1)
+      assert Process.info(self(), :messages) == {:messages, [0, -2, 2, 1]}
     end
 
-    test "has proper evaluation order" do
+    test "preserves variable semantics" do
       a = 1
       assert 1 in [a = 2, a]
       # silence unused var warning