diff --git a/hgext/purge.py b/hgext/purge.py
--- a/hgext/purge.py
+++ b/hgext/purge.py
@@ -36,4 +36,7 @@ the default, unless the extension is ena
 # extensions which SHIP WITH MERCURIAL. Non-mainline extensions should
 # be specifying the version(s) of Mercurial they are tested with, or
 # leave the attribute unspecified.
+
+from __future__ import annotations
+
 testedwith = b'ships-with-hg-core'
diff --git a/mercurial/__main__.py b/mercurial/__main__.py
--- a/mercurial/__main__.py
+++ b/mercurial/__main__.py
@@ -1,3 +1,6 @@
+from __future__ import annotations
+
+
 def run():
     from . import demandimport
 
diff --git a/mercurial/admin/chainsaw.py b/mercurial/admin/chainsaw.py
--- a/mercurial/admin/chainsaw.py
+++ b/mercurial/admin/chainsaw.py
@@ -19,6 +19,8 @@ It is recommended to run these commands 
 variable (see :hg:`help scripting`).
 """
 
+from __future__ import annotations
+
 import shutil
 
 from ..i18n import _
diff --git a/mercurial/admin/verify.py b/mercurial/admin/verify.py
--- a/mercurial/admin/verify.py
+++ b/mercurial/admin/verify.py
@@ -5,6 +5,8 @@
 # This software may be used and distributed according to the terms of the
 # GNU General Public License version 2 or any later version.
 
+from __future__ import annotations
+
 import collections
 import copy
 import functools
diff --git a/mercurial/admin_commands.py b/mercurial/admin_commands.py
--- a/mercurial/admin_commands.py
+++ b/mercurial/admin_commands.py
@@ -5,6 +5,8 @@
 # This software may be used and distributed according to the terms of the
 # GNU General Public License version 2 or any later version.
 
+from __future__ import annotations
+
 from .i18n import _
 from .admin import chainsaw, verify
 from . import error, registrar, transaction
diff --git a/mercurial/bundlecaches.py b/mercurial/bundlecaches.py
--- a/mercurial/bundlecaches.py
+++ b/mercurial/bundlecaches.py
@@ -3,6 +3,8 @@
 # This software may be used and distributed according to the terms of the
 # GNU General Public License version 2 or any later version.
 
+from __future__ import annotations
+
 import collections
 import typing
 
diff --git a/mercurial/revlogutils/concurrency_checker.py b/mercurial/revlogutils/concurrency_checker.py
--- a/mercurial/revlogutils/concurrency_checker.py
+++ b/mercurial/revlogutils/concurrency_checker.py
@@ -1,3 +1,5 @@
+from __future__ import annotations
+
 from ..i18n import _
 from .. import error
 
diff --git a/mercurial/revlogutils/debug.py b/mercurial/revlogutils/debug.py
--- a/mercurial/revlogutils/debug.py
+++ b/mercurial/revlogutils/debug.py
@@ -6,6 +6,8 @@
 # This software may be used and distributed according to the terms of the
 # GNU General Public License version 2 or any later version.
 
+from __future__ import annotations
+
 import collections
 import string
 
diff --git a/mercurial/revlogutils/randomaccessfile.py b/mercurial/revlogutils/randomaccessfile.py
--- a/mercurial/revlogutils/randomaccessfile.py
+++ b/mercurial/revlogutils/randomaccessfile.py
@@ -3,6 +3,8 @@
 # This software may be used and distributed according to the terms of the
 # GNU General Public License version 2 or any later version.
 
+from __future__ import annotations
+
 import contextlib
 
 from ..i18n import _
diff --git a/mercurial/revlogutils/rewrite.py b/mercurial/revlogutils/rewrite.py
--- a/mercurial/revlogutils/rewrite.py
+++ b/mercurial/revlogutils/rewrite.py
@@ -7,6 +7,8 @@
 # This software may be used and distributed according to the terms of the
 # GNU General Public License version 2 or any later version.
 
+from __future__ import annotations
+
 import binascii
 import contextlib
 import os
diff --git a/mercurial/stabletailgraph/stabletailsort.py b/mercurial/stabletailgraph/stabletailsort.py
--- a/mercurial/stabletailgraph/stabletailsort.py
+++ b/mercurial/stabletailgraph/stabletailsort.py
@@ -19,6 +19,8 @@ This module and implementation are exper
 optimised to operate on large production graphs.
 """
 
+from __future__ import annotations
+
 import itertools
 from ..node import nullrev
 from .. import ancestor
diff --git a/mercurial/typelib.py b/mercurial/typelib.py
--- a/mercurial/typelib.py
+++ b/mercurial/typelib.py
@@ -5,6 +5,8 @@
 # This software may be used and distributed according to the terms of the
 # GNU General Public License version 2 or any later version.
 
+from __future__ import annotations
+
 import typing
 
 from typing import (
diff --git a/mercurial/upgrade_utils/auto_upgrade.py b/mercurial/upgrade_utils/auto_upgrade.py
--- a/mercurial/upgrade_utils/auto_upgrade.py
+++ b/mercurial/upgrade_utils/auto_upgrade.py
@@ -4,6 +4,9 @@
 #
 # This software may be used and distributed according to the terms of the
 # GNU General Public License version 2 or any later version.
+
+from __future__ import annotations
+
 from ..i18n import _
 
 from .. import (
diff --git a/mercurial/utils/memorytop.py b/mercurial/utils/memorytop.py
--- a/mercurial/utils/memorytop.py
+++ b/mercurial/utils/memorytop.py
@@ -5,6 +5,8 @@
 # memorytop in strategic places to show the current memory use by allocation
 # site.
 
+from __future__ import annotations
+
 import gc
 import tracemalloc
 
diff --git a/mercurial/utils/urlutil.py b/mercurial/utils/urlutil.py
--- a/mercurial/utils/urlutil.py
+++ b/mercurial/utils/urlutil.py
@@ -4,6 +4,9 @@
 #
 # This software may be used and distributed according to the terms of the
 # GNU General Public License version 2 or any later version.
+
+from __future__ import annotations
+
 import os
 import re as remod
 import socket