Handle Kernel.in/2 in type system instead of using rewrite rules, closes #15130

Author: josevalim

lib/elixir/lib/kernel.ex

@@ -4711,8 +4711,6 @@ defmodule Kernel do
         end
 
       [head | tail] = list ->
-        # We only expand lists in the body if they are relatively
-        # short and it is made only of literal expressions.
         case in_body? do
           false -> in_list(left, head, tail, expand, list)
           true -> quote(do: :lists.member(unquote(left), unquote(right)))

lib/elixir/lib/module/types/apply.ex

@@ -2021,6 +2021,10 @@ defmodule Module.Types.Apply do
 
   alias Inspect.Algebra, as: IA
 
+  defp type_comparison_to_string(:lists, :member, left, right) do
+    type_comparison_to_string(Kernel, :in, left, right)
+  end
+
   defp type_comparison_to_string(mod, fun, left, right) do
     {_, fun, _, _} = :elixir_rewrite.erl_to_ex(mod, fun, [left, right])
 

lib/elixir/lib/module/types/helpers.ex

@@ -329,6 +329,13 @@ defmodule Module.Types.Helpers do
             end
         end
 
+      {{:., _, [:lists, :member]}, meta, [expr, [_ | _] = args]} = call ->
+        if Enum.any?(args, &match?({:|, _, [_, _]}, &1)) do
+          call
+        else
+          {:in, meta, [expr, args]}
+        end
+
       {{:., _, [Elixir.String.Chars, :to_string]}, meta, [arg]} ->
         {:to_string, meta, [arg]}
 

lib/elixir/src/elixir_rewrite.erl

@@ -109,7 +109,6 @@ inline(Mod, Fun, Arity) -> inner_inline(ex_to_erl, Mod, Fun, Arity).
 ?inline(?kernel, floor, 1, erlang, floor);
 ?inline(?kernel, 'function_exported?', 3, erlang, function_exported);
 ?inline(?kernel, hd, 1, erlang, hd);
-?inline(?kernel, in, 2, lists, member);
 ?inline(?kernel, is_atom, 1, erlang, is_atom);
 ?inline(?kernel, is_binary, 1, erlang, is_binary);
 ?inline(?kernel, is_bitstring, 1, erlang, is_bitstring);

lib/elixir/test/elixir/kernel/guard_test.exs

@@ -483,6 +483,14 @@ defmodule Kernel.GuardTest do
              """
     end
 
+    defguard in_list(a) when Kernel.in(a, [:test])
+
+    test "expands remote functions" do
+      assert expand_defguard_to_string(:in_list, [:not_test], :guard) == """
+             :erlang.\"=:=\"(:not_test, :test)
+             """
+    end
+
     defp expand_defguard_to_string(fun, args, context) do
       {{:., [], [__MODULE__, fun]}, [], args}
       |> Macro.expand(%{__ENV__ | context: context})