Handle recursive vars in map values (#10498)

Author: josevalim

lib/elixir/lib/module/types/unify.ex

@@ -166,8 +166,11 @@ defmodule Module.Types.Unify do
           end
 
         case unify_result do
-          {:ok, var_type, context} ->
-            context = refine_var(var, var_type, stack, context)
+          {:ok, {:var, ^var}, context} ->
+            {:ok, {:var, var}, context}
+
+          {:ok, res_type, context} ->
+            context = refine_var(var, res_type, stack, context)
             {:ok, {:var, var}, context}
 
           {:error, reason} ->

lib/elixir/test/elixir/module/types/types_test.exs

@@ -13,23 +13,21 @@ defmodule Module.Types.TypesTest do
     expr = TypeHelper.expand_expr(patterns, guards, body, __CALLER__)
 
     quote do
-      unquote(Macro.escape(expr))
-      |> Module.Types.TypesTest.__expr__()
-      |> to_warning()
+      Module.Types.TypesTest.__expr__(unquote(Macro.escape(expr)))
     end
   end
 
   def __expr__({patterns, guards, body}) do
     with {:ok, _types, context} <-
            Pattern.of_head(patterns, guards, TypeHelper.new_stack(), TypeHelper.new_context()),
-         {:ok, type, context} <- Expr.of_expr(body, TypeHelper.new_stack(), context) do
+         {:ok, _type, context} <- Expr.of_expr(body, TypeHelper.new_stack(), context) do
       case context.warnings do
-        [warning] -> {:warning, warning}
-        _ -> flunk("expexted error, got: #{inspect(Types.lift_type(type, context))}")
+        [warning] -> to_message(:warning, warning)
+        _ -> :none
       end
     else
       {:error, {type, reason, context}} ->
-        {:error, {type, reason, context}}
+        to_message(:error, {type, reason, context})
     end
   end
 
@@ -51,13 +49,13 @@ defmodule Module.Types.TypesTest do
     min
   end
 
-  defp to_warning({:warning, {module, warning, _location}}) do
+  defp to_message(:warning, {module, warning, _location}) do
     warning
     |> module.format_warning()
     |> IO.iodata_to_binary()
   end
 
-  defp to_warning({:error, {type, reason, context}}) do
+  defp to_message(:error, {type, reason, context}) do
     {Module.Types, error, _location} = Module.Types.error_to_warning(type, reason, context)
 
     error
@@ -472,4 +470,20 @@ defmodule Module.Types.TypesTest do
              """
     end
   end
+
+  describe "regressions" do
+    test "recursive map fields" do
+      assert warning(
+               [queried],
+               with(
+                 true <- is_nil(queried.foo.bar),
+                 _ = queried.foo
+               ) do
+                 %{foo: %{other_id: _other_id} = foo} = queried
+                 %{other_id: id} = foo
+                 %{id: id}
+               end
+             ) == :none
+    end
+  end
 end

lib/elixir/test/elixir/module/types/unify_test.exs

@@ -350,11 +350,22 @@ defmodule Module.Types.UnifyTest do
       assert {{:var, 2}, var_context} = new_var({:baz, [version: 2], nil}, var_context)
 
       assert {:ok, {:var, _}, context} = unify({:var, 0}, {:var, 1}, var_context)
-      assert {:ok, {:var, _}, _context} = unify({:var, 1}, {:var, 0}, context)
+      assert {:ok, {:var, _}, context} = unify({:var, 1}, {:var, 0}, context)
+      assert context.types[0] == {:var, 1}
+      assert context.types[1] == {:var, 0}
+
+      assert {:ok, {:var, _}, context} = unify({:var, 0}, :tuple, var_context)
+      assert {:ok, {:var, _}, context} = unify({:var, 1}, {:var, 0}, context)
+      assert {:ok, {:var, _}, context} = unify({:var, 0}, {:var, 1}, context)
+      assert context.types[0] == {:var, 1}
+      assert context.types[1] == :tuple
 
       assert {:ok, {:var, _}, context} = unify({:var, 0}, {:var, 1}, var_context)
       assert {:ok, {:var, _}, context} = unify({:var, 1}, {:var, 2}, context)
       assert {:ok, {:var, _}, _context} = unify({:var, 2}, {:var, 0}, context)
+      assert context.types[0] == :unbound
+      assert context.types[1] == {:var, 0}
+      assert context.types[2] == {:var, 1}
 
       assert {:ok, {:var, _}, context} = unify({:var, 0}, {:var, 1}, var_context)