From 3be1399587553842e593e7109590f85ca93d401e Mon Sep 17 00:00:00 2001
From: Aaron Tinio <aptinio@gmail.com>
Date: Thu, 12 Mar 2026 13:12:21 +0800
Subject: [PATCH] Skip (is_atom(name) or :fail) in is_struct/2 and
 is_exception/2 guard expansion when name is a compile-time atom

---
 lib/elixir/lib/exception.ex                   |  9 ++++
 lib/elixir/lib/kernel.ex                      | 42 +++++++++++++------
 .../test/elixir/module/types/pattern_test.exs |  4 ++
 3 files changed, 43 insertions(+), 12 deletions(-)

diff --git a/lib/elixir/lib/exception.ex b/lib/elixir/lib/exception.ex
index 3d2fdc60b40..51ba620fa4b 100644
--- a/lib/elixir/lib/exception.ex
+++ b/lib/elixir/lib/exception.ex
@@ -313,6 +313,15 @@ defmodule Exception do
        ),
        do: map_node?(node_1) and map_key_node?(node_2) and struct_validation_node?(node_3)
 
+  defp struct_macro?(
+         {:and, _,
+          [
+            {:and, _, [%{node: node_1 = {_, _, [arg]}}, %{node: node_2 = {_, _, [arg, _]}}]},
+            %{node: node_3 = {_, _, [{_, _, [_, arg]}, _]}}
+          ]}
+       ),
+       do: map_node?(node_1) and map_key_node?(node_2) and struct_validation_node?(node_3)
+
   defp struct_macro?(
          {:and, _,
           [
diff --git a/lib/elixir/lib/kernel.ex b/lib/elixir/lib/kernel.ex
index 4ae542edc87..4530dcc6df7 100644
--- a/lib/elixir/lib/kernel.ex
+++ b/lib/elixir/lib/kernel.ex
@@ -2681,11 +2681,19 @@ defmodule Kernel do
         invalid_match!(:is_struct)
 
       :guard ->
-        quote do
-          is_map(unquote(term)) and
-            (is_atom(unquote(name)) or :fail) and
-            :erlang.is_map_key(:__struct__, unquote(term)) and
-            :erlang.map_get(:__struct__, unquote(term)) == unquote(name)
+        if is_atom(name) or is_atom(Macro.expand(name, __CALLER__)) do
+          quote do
+            is_map(unquote(term)) and
+              :erlang.is_map_key(:__struct__, unquote(term)) and
+              :erlang.map_get(:__struct__, unquote(term)) == unquote(name)
+          end
+        else
+          quote do
+            is_map(unquote(term)) and
+              (is_atom(unquote(name)) or :fail) and
+              :erlang.is_map_key(:__struct__, unquote(term)) and
+              :erlang.map_get(:__struct__, unquote(term)) == unquote(name)
+          end
         end
     end
   end
@@ -2805,13 +2813,23 @@ defmodule Kernel do
         invalid_match!(:is_exception)
 
       :guard ->
-        quote do
-          is_map(unquote(term)) and
-            (is_atom(unquote(name)) or :fail) and
-            :erlang.is_map_key(:__struct__, unquote(term)) and
-            :erlang.map_get(:__struct__, unquote(term)) == unquote(name) and
-            :erlang.is_map_key(:__exception__, unquote(term)) and
-            :erlang.map_get(:__exception__, unquote(term)) == true
+        if is_atom(name) or is_atom(Macro.expand(name, __CALLER__)) do
+          quote do
+            is_map(unquote(term)) and
+              :erlang.is_map_key(:__struct__, unquote(term)) and
+              :erlang.map_get(:__struct__, unquote(term)) == unquote(name) and
+              :erlang.is_map_key(:__exception__, unquote(term)) and
+              :erlang.map_get(:__exception__, unquote(term)) == true
+          end
+        else
+          quote do
+            is_map(unquote(term)) and
+              (is_atom(unquote(name)) or :fail) and
+              :erlang.is_map_key(:__struct__, unquote(term)) and
+              :erlang.map_get(:__struct__, unquote(term)) == unquote(name) and
+              :erlang.is_map_key(:__exception__, unquote(term)) and
+              :erlang.map_get(:__exception__, unquote(term)) == true
+          end
         end
     end
   end
diff --git a/lib/elixir/test/elixir/module/types/pattern_test.exs b/lib/elixir/test/elixir/module/types/pattern_test.exs
index e5b39f41b98..90944ad85c4 100644
--- a/lib/elixir/test/elixir/module/types/pattern_test.exs
+++ b/lib/elixir/test/elixir/module/types/pattern_test.exs
@@ -647,6 +647,10 @@ defmodule Module.Types.PatternTest do
       assert typecheck!([x], is_struct(x, URI), x) == dynamic(open_map(__struct__: atom([URI])))
     end
 
+    test "not is_struct/2" do
+      assert typecheck!([x], not is_struct(x, URI), x)
+    end
+
     test "is_binary/1" do
       assert typecheck!([x], is_binary(x), x) == dynamic(binary())
       assert typecheck!([x], not is_binary(x), x) == dynamic(negation(binary()))