From 4da44bb6ff81caeff7a6c186f1befdce20d82316 Mon Sep 17 00:00:00 2001
From: Alex Gubarev <gubarev.alex@gmail.com>
Date: Tue, 14 Jul 2026 16:38:29 +0300
Subject: [PATCH 1/2] Fix Map.from_struct/1 typecheck

---
 lib/elixir/lib/module/types/apply.ex          | 23 ++++++++++++++-----
 .../test/elixir/module/types/map_test.exs     | 12 +++++-----
 2 files changed, 23 insertions(+), 12 deletions(-)

diff --git a/lib/elixir/lib/module/types/apply.ex b/lib/elixir/lib/module/types/apply.ex
index 9dffd1e28f9..42203248d80 100644
--- a/lib/elixir/lib/module/types/apply.ex
+++ b/lib/elixir/lib/module/types/apply.ex
@@ -254,7 +254,7 @@ defmodule Module.Types.Apply do
         {Map, :fetch,
          [{[open_map(), term()], tuple([atom([:ok]), term()]) |> opt_union(atom([:error]))}]},
         {Map, :fetch!, [{[open_map(), term()], term()}]},
-        {Map, :from_struct, [{[open_map()], open_map(__struct__: not_set())}]},
+        {Map, :from_struct, [{[open_map(__struct__: atom())], open_map(__struct__: not_set())}]},
         {Map, :get, [{[open_map(), term()], term()}]},
         {Map, :get, [{[open_map(), term(), term()], term()}]},
         {Map, :get_lazy, [{[open_map(), term(), fun(0)], term()}]},
@@ -1129,11 +1129,22 @@ defmodule Module.Types.Apply do
   @struct_key atom([:__struct__])
   @nil_atom atom([nil])
 
-  defp remote_apply(Map, :from_struct, _info, [map] = args_types, stack) do
-    case map_update(map, @struct_key, not_set(), false, true) do
-      {_value, descr, _errors} -> {:ok, return(descr, args_types, stack)}
-      :badmap -> {:error, badremote(Map, :from_struct, args_types)}
-      {:error, _errors} -> {:ok, map}
+  defp remote_apply(Map, :from_struct, info, [map] = args_types, stack) do
+    case remote_apply(info, args_types, stack) do
+      {:ok, _type} ->
+        case map_update(map, @struct_key, not_set(), false, true) do
+          {_value, descr, _errors} ->
+            {:ok, return(descr, args_types, stack)}
+
+          :badmap ->
+            {:error, badremote(Map, :from_struct, args_types)}
+
+          {:error, _errors} ->
+            {:error, badremote(Map, :from_struct, args_types)}
+        end
+
+      other ->
+        other
     end
   end
 
diff --git a/lib/elixir/test/elixir/module/types/map_test.exs b/lib/elixir/test/elixir/module/types/map_test.exs
index e0cc57c24c9..24b0df12d74 100644
--- a/lib/elixir/test/elixir/module/types/map_test.exs
+++ b/lib/elixir/test/elixir/module/types/map_test.exs
@@ -330,11 +330,8 @@ defmodule Module.Types.MapTest do
 
   describe "Map.from_struct/1" do
     test "checking" do
-      assert typecheck!(Map.from_struct(%{})) ==
-               empty_map()
-
-      assert typecheck!(Map.from_struct(%{key: 123})) ==
-               closed_map(key: integer())
+      assert typecheck!(Map.from_struct(%{__struct__: URI, port: 433})) ==
+               closed_map(port: integer())
 
       assert typecheck!(Map.from_struct(%URI{})) ==
                closed_map(
@@ -359,12 +356,15 @@ defmodule Module.Types.MapTest do
                  _ = Map.from_struct(x)
                  x
                )
-             ) == dynamic(open_map())
+             ) == dynamic(open_map(__struct__: atom()))
     end
 
     test "errors" do
       assert typeerror!([x = []], Map.from_struct(x)) =~
                "incompatible types given to Map.from_struct/1"
+
+      assert typeerror!(Map.from_struct(%{})) =~
+               "incompatible types given to Map.from_struct/1"
     end
   end
 

From d61719bf8e824892ca1cbccab5c21bf5ff571f1a Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Jos=C3=A9=20Valim?= <jose.valim@gmail.com>
Date: Tue, 14 Jul 2026 16:38:31 +0200
Subject: [PATCH 2/2] Apply suggestion from @josevalim

---
 lib/elixir/lib/module/types/apply.ex | 5 +----
 1 file changed, 1 insertion(+), 4 deletions(-)

diff --git a/lib/elixir/lib/module/types/apply.ex b/lib/elixir/lib/module/types/apply.ex
index 42203248d80..c6a18b93cf3 100644
--- a/lib/elixir/lib/module/types/apply.ex
+++ b/lib/elixir/lib/module/types/apply.ex
@@ -1136,10 +1136,7 @@ defmodule Module.Types.Apply do
           {_value, descr, _errors} ->
             {:ok, return(descr, args_types, stack)}
 
-          :badmap ->
-            {:error, badremote(Map, :from_struct, args_types)}
-
-          {:error, _errors} ->
+          _ ->
             {:error, badremote(Map, :from_struct, args_types)}
         end