diff --git a/mercurial/branchmap.py b/mercurial/branchmap.py
--- a/mercurial/branchmap.py
+++ b/mercurial/branchmap.py
@@ -13,47 +13,50 @@ from .node import (
     hex,
     nullrev,
 )
+
+from typing import (
+    Any,
+    Callable,
+    Dict,
+    Iterable,
+    List,
+    Optional,
+    Set,
+    TYPE_CHECKING,
+    Tuple,
+    Union,
+)
+
 from . import (
     encoding,
     error,
     obsolete,
-    pycompat,
     scmutil,
     util,
 )
+
 from .utils import (
     repoviewutil,
     stringutil,
 )
 
-if pycompat.TYPE_CHECKING:
-    from typing import (
-        Any,
-        Callable,
-        Dict,
-        Iterable,
-        List,
-        Optional,
-        Set,
-        Tuple,
-        Union,
-    )
+# keeps pyflakes happy
+assert [
+    Any,
+    Callable,
+    Dict,
+    Iterable,
+    List,
+    Optional,
+    Set,
+    Tuple,
+    Union,
+]
+
+if TYPE_CHECKING:
     from . import localrepo
 
-    assert any(
-        (
-            Any,
-            Callable,
-            Dict,
-            Iterable,
-            List,
-            Optional,
-            Set,
-            Tuple,
-            Union,
-            localrepo,
-        )
-    )
+    assert [localrepo]
 
 subsettable = repoviewutil.subsettable
 
diff --git a/mercurial/cmdutil.py b/mercurial/cmdutil.py
--- a/mercurial/cmdutil.py
+++ b/mercurial/cmdutil.py
@@ -18,6 +18,7 @@ from typing import (
     Dict,
     Iterable,
     Optional,
+    TYPE_CHECKING,
     cast,
 )
 
@@ -71,7 +72,7 @@ from .revlogutils import (
     constants as revlog_constants,
 )
 
-if pycompat.TYPE_CHECKING:
+if TYPE_CHECKING:
     from . import (
         ui as uimod,
     )
diff --git a/mercurial/encoding.py b/mercurial/encoding.py
--- a/mercurial/encoding.py
+++ b/mercurial/encoding.py
@@ -9,8 +9,19 @@
 import locale
 import os
 import re
+import typing
 import unicodedata
 
+from typing import (
+    Any,
+    Callable,
+    List,
+    Text,
+    Type,
+    TypeVar,
+    Union,
+)
+
 from . import (
     error,
     policy,
@@ -19,22 +30,11 @@ from . import (
 
 from .pure import charencode as charencodepure
 
-if pycompat.TYPE_CHECKING:
-    from typing import (
-        Any,
-        Callable,
-        List,
-        Text,
-        Type,
-        TypeVar,
-        Union,
-    )
+# keep pyflakes happy
+for t in (Any, Callable, List, Text, Type, Union):
+    assert t
 
-    # keep pyflakes happy
-    for t in (Any, Callable, List, Text, Type, Union):
-        assert t
-
-    _Tlocalstr = TypeVar('_Tlocalstr', bound='localstr')
+_Tlocalstr = TypeVar('_Tlocalstr', bound='localstr')
 
 charencode = policy.importmod('charencode')
 
@@ -131,7 +131,7 @@ class localstr(bytes):
         s._utf8 = u
         return s
 
-    if pycompat.TYPE_CHECKING:
+    if typing.TYPE_CHECKING:
         # pseudo implementation to help pytype see localstr() constructor
         def __init__(self, u, l):
             # type: (bytes, bytes) -> None
diff --git a/mercurial/error.py b/mercurial/error.py
--- a/mercurial/error.py
+++ b/mercurial/error.py
@@ -14,19 +14,30 @@ imports.
 
 import difflib
 
+from typing import (
+    Any,
+    AnyStr,
+    Iterable,
+    List,
+    Optional,
+    Sequence,
+    Union,
+)
+
 # Do not import anything but pycompat here, please
 from . import pycompat
 
-if pycompat.TYPE_CHECKING:
-    from typing import (
-        Any,
-        AnyStr,
-        Iterable,
-        List,
-        Optional,
-        Sequence,
-        Union,
-    )
+
+# keeps pyflakes happy
+assert [
+    Any,
+    AnyStr,
+    Iterable,
+    List,
+    Optional,
+    Sequence,
+    Union,
+]
 
 
 def _tobytes(exc):
diff --git a/mercurial/i18n.py b/mercurial/i18n.py
--- a/mercurial/i18n.py
+++ b/mercurial/i18n.py
@@ -11,18 +11,22 @@ import locale
 import os
 import sys
 
+from typing import (
+    Callable,
+    List,
+)
+
 from .utils import resourceutil
 from . import (
     encoding,
     pycompat,
 )
 
-if pycompat.TYPE_CHECKING:
-    from typing import (
-        Callable,
-        List,
-    )
-
+# keeps pyflakes happy
+assert [
+    Callable,
+    List,
+]
 
 # modelled after templater.templatepath:
 if getattr(sys, 'frozen', None) is not None:
diff --git a/mercurial/logcmdutil.py b/mercurial/logcmdutil.py
--- a/mercurial/logcmdutil.py
+++ b/mercurial/logcmdutil.py
@@ -10,6 +10,15 @@ import itertools
 import os
 import posixpath
 
+from typing import (
+    Any,
+    Callable,
+    Dict,
+    Optional,
+    Sequence,
+    Tuple,
+)
+
 from .i18n import _
 from .node import wdirrev
 
@@ -39,19 +48,19 @@ from .utils import (
     stringutil,
 )
 
+# keeps pyflakes happy
+assert [
+    Any,
+    Callable,
+    Dict,
+    Optional,
+    Sequence,
+    Tuple,
+]
 
-if pycompat.TYPE_CHECKING:
-    from typing import (
-        Any,
-        Callable,
-        Dict,
-        Optional,
-        Sequence,
-        Tuple,
-    )
-
-    for t in (Any, Callable, Dict, Optional, Tuple):
-        assert t
+# keep pyflakes happy
+for t in (Any, Callable, Dict, Optional, Tuple):
+    assert t
 
 
 def getlimit(opts):
diff --git a/mercurial/mail.py b/mercurial/mail.py
--- a/mercurial/mail.py
+++ b/mercurial/mail.py
@@ -18,6 +18,13 @@ import smtplib
 import socket
 import time
 
+from typing import (
+    Any,
+    List,
+    Tuple,
+    Union,
+)
+
 from .i18n import _
 from .pycompat import (
     open,
@@ -35,11 +42,14 @@ from .utils import (
     urlutil,
 )
 
-if pycompat.TYPE_CHECKING:
-    from typing import Any, List, Tuple, Union
 
-    # keep pyflakes happy
-    assert all((Any, List, Tuple, Union))
+# keep pyflakes happy
+assert [
+    Any,
+    List,
+    Tuple,
+    Union,
+]
 
 
 class STARTTLS(smtplib.SMTP):
diff --git a/mercurial/pathutil.py b/mercurial/pathutil.py
--- a/mercurial/pathutil.py
+++ b/mercurial/pathutil.py
@@ -23,6 +23,14 @@ from . import (
 rustdirs = policy.importrust('dirstate', 'Dirs')
 parsers = policy.importmod('parsers')
 
+# keeps pyflakes happy
+assert [
+    Any,
+    Callable,
+    Iterator,
+    Optional,
+]
+
 
 def _lowerclean(s):
     # type: (bytes) -> bytes
diff --git a/mercurial/phases.py b/mercurial/phases.py
--- a/mercurial/phases.py
+++ b/mercurial/phases.py
@@ -102,6 +102,18 @@ Note: old client behave as a publishing 
 
 
 import struct
+import typing
+
+from typing import (
+    Any,
+    Callable,
+    Dict,
+    Iterable,
+    List,
+    Optional,
+    Set,
+    Tuple,
+)
 
 from .i18n import _
 from .node import (
@@ -120,23 +132,29 @@ from . import (
     util,
 )
 
-if pycompat.TYPE_CHECKING:
-    from typing import (
-        Any,
-        Callable,
-        Dict,
-        Iterable,
-        List,
-        Optional,
-        Set,
-        Tuple,
-    )
+# keeps pyflakes happy
+assert [
+    Any,
+    Callable,
+    Dict,
+    Iterable,
+    List,
+    Optional,
+    Set,
+    Tuple,
+]
+
+Phaseroots = Dict[int, Set[bytes]]
+
+if typing.TYPE_CHECKING:
     from . import (
         localrepo,
         ui as uimod,
     )
 
-    Phaseroots = Dict[int, Set[bytes]]
+    # keeps pyflakes happy
+    assert [uimod]
+
     Phasedefaults = List[
         Callable[[localrepo.localrepository, Phaseroots], Phaseroots]
     ]
diff --git a/mercurial/posix.py b/mercurial/posix.py
--- a/mercurial/posix.py
+++ b/mercurial/posix.py
@@ -70,13 +70,6 @@ rename = os.rename
 removedirs = os.removedirs
 
 if typing.TYPE_CHECKING:
-    # Replace the various overloads that come along with aliasing stdlib methods
-    # with the narrow definition that we care about in the type checking phase
-    # only.  This ensures that both Windows and POSIX see only the definition
-    # that is actually available.
-    #
-    # Note that if we check pycompat.TYPE_CHECKING here, it is always False, and
-    # the methods aren't replaced.
 
     def normpath(path: bytes) -> bytes:
         raise NotImplementedError
diff --git a/mercurial/scmposix.py b/mercurial/scmposix.py
--- a/mercurial/scmposix.py
+++ b/mercurial/scmposix.py
@@ -3,6 +3,7 @@ import errno
 import fcntl
 import os
 import sys
+import typing
 
 from typing import (
     List,
@@ -15,7 +16,7 @@ from . import (
     util,
 )
 
-if pycompat.TYPE_CHECKING:
+if typing.TYPE_CHECKING:
     from . import ui as uimod
 
 # BSD 'more' escapes ANSI color sequences by default. This can be disabled by
diff --git a/mercurial/scmwindows.py b/mercurial/scmwindows.py
--- a/mercurial/scmwindows.py
+++ b/mercurial/scmwindows.py
@@ -3,6 +3,7 @@ import winreg  # pytype: disable=import-
 
 from typing import (
     List,
+    TYPE_CHECKING,
     Tuple,
 )
 
@@ -13,7 +14,7 @@ from . import (
     win32,
 )
 
-if pycompat.TYPE_CHECKING:
+if TYPE_CHECKING:
     from . import ui as uimod
 
 # MS-DOS 'more' is the only pager available by default on Windows.
diff --git a/mercurial/state.py b/mercurial/state.py
--- a/mercurial/state.py
+++ b/mercurial/state.py
@@ -20,23 +20,22 @@ the data.
 
 import contextlib
 
+from typing import (
+    Any,
+    Dict,
+)
+
 from .i18n import _
 
 from . import (
     error,
-    pycompat,
     util,
 )
 from .utils import cborutil
 
-if pycompat.TYPE_CHECKING:
-    from typing import (
-        Any,
-        Dict,
-    )
-
-    for t in (Any, Dict):
-        assert t
+# keeps pyflakes happy
+for t in (Any, Dict):
+    assert t
 
 
 class cmdstate:
diff --git a/mercurial/subrepoutil.py b/mercurial/subrepoutil.py
--- a/mercurial/subrepoutil.py
+++ b/mercurial/subrepoutil.py
@@ -9,6 +9,16 @@
 import os
 import posixpath
 import re
+import typing
+
+from typing import (
+    Any,
+    Dict,
+    List,
+    Optional,
+    Set,
+    Tuple,
+)
 
 from .i18n import _
 from . import (
@@ -17,7 +27,6 @@ from . import (
     filemerge,
     pathutil,
     phases,
-    pycompat,
     util,
 )
 from .utils import (
@@ -25,17 +34,19 @@ from .utils import (
     urlutil,
 )
 
+# keeps pyflakes happy
+assert [
+    Any,
+    Dict,
+    List,
+    Optional,
+    Set,
+    Tuple,
+]
+
 nullstate = (b'', b'', b'empty')
 
-if pycompat.TYPE_CHECKING:
-    from typing import (
-        Any,
-        Dict,
-        List,
-        Optional,
-        Set,
-        Tuple,
-    )
+if typing.TYPE_CHECKING:
     from . import (
         context,
         localrepo,
@@ -45,7 +56,17 @@ if pycompat.TYPE_CHECKING:
         ui as uimod,
     )
 
-    Substate = Dict[bytes, Tuple[bytes, bytes, bytes]]
+    # keeps pyflakes happy
+    assert [
+        context,
+        localrepo,
+        matchmod,
+        scmutil,
+        subrepo,
+        uimod,
+    ]
+
+Substate = Dict[bytes, Tuple[bytes, bytes, bytes]]
 
 
 def state(ctx, ui):
diff --git a/mercurial/ui.py b/mercurial/ui.py
--- a/mercurial/ui.py
+++ b/mercurial/ui.py
@@ -18,6 +18,7 @@ import socket
 import subprocess
 import sys
 import traceback
+import typing
 
 from typing import (
     Any,
@@ -1766,7 +1767,7 @@ class ui:
 
         return line
 
-    if pycompat.TYPE_CHECKING:
+    if typing.TYPE_CHECKING:
 
         @overload
         def prompt(self, msg: bytes, default: bytes) -> bytes:
@@ -1782,7 +1783,7 @@ class ui:
         """
         return self._prompt(msg, default=default)
 
-    if pycompat.TYPE_CHECKING:
+    if typing.TYPE_CHECKING:
 
         @overload
         def _prompt(
diff --git a/mercurial/upgrade_utils/actions.py b/mercurial/upgrade_utils/actions.py
--- a/mercurial/upgrade_utils/actions.py
+++ b/mercurial/upgrade_utils/actions.py
@@ -7,11 +7,15 @@
 
 import random
 
+from typing import (
+    List,
+    Type,
+)
+
 from ..i18n import _
 from .. import (
     error,
     localrepo,
-    pycompat,
     requirements,
     revlog,
     util,
@@ -19,12 +23,11 @@ from .. import (
 
 from ..utils import compression
 
-if pycompat.TYPE_CHECKING:
-    from typing import (
-        List,
-        Type,
-    )
-
+# keeps pyflakes happy
+assert [
+    List,
+    Type,
+]
 
 # list of requirements that request a clone of all revlog if added/removed
 RECLONES_REQUIREMENTS = {
diff --git a/mercurial/util.py b/mercurial/util.py
--- a/mercurial/util.py
+++ b/mercurial/util.py
@@ -34,6 +34,14 @@ import time
 import traceback
 import warnings
 
+from typing import (
+    Iterable,
+    Iterator,
+    List,
+    Optional,
+    Tuple,
+)
+
 from .node import hex
 from .thirdparty import attr
 from .pycompat import (
@@ -55,14 +63,14 @@ from .utils import (
     stringutil,
 )
 
-if pycompat.TYPE_CHECKING:
-    from typing import (
-        Iterable,
-        Iterator,
-        List,
-        Optional,
-        Tuple,
-    )
+# keeps pyflakes happy
+assert [
+    Iterable,
+    Iterator,
+    List,
+    Optional,
+    Tuple,
+]
 
 
 base85 = policy.importmod('base85')
diff --git a/mercurial/utils/dateutil.py b/mercurial/utils/dateutil.py
--- a/mercurial/utils/dateutil.py
+++ b/mercurial/utils/dateutil.py
@@ -10,6 +10,15 @@ import calendar
 import datetime
 import time
 
+from typing import (
+    Callable,
+    Dict,
+    Iterable,
+    Optional,
+    Tuple,
+    Union,
+)
+
 from ..i18n import _
 from .. import (
     encoding,
@@ -17,17 +26,17 @@ from .. import (
     pycompat,
 )
 
-if pycompat.TYPE_CHECKING:
-    from typing import (
-        Callable,
-        Dict,
-        Iterable,
-        Optional,
-        Tuple,
-        Union,
-    )
+# keeps pyflakes happy
+assert [
+    Callable,
+    Dict,
+    Iterable,
+    Optional,
+    Tuple,
+    Union,
+]
 
-    hgdate = Tuple[float, int]  # (unixtime, offset)
+hgdate = Tuple[float, int]  # (unixtime, offset)
 
 # used by parsedate
 defaultdateformats = (
diff --git a/mercurial/utils/urlutil.py b/mercurial/utils/urlutil.py
--- a/mercurial/utils/urlutil.py
+++ b/mercurial/utils/urlutil.py
@@ -8,6 +8,10 @@ import os
 import re as remod
 import socket
 
+from typing import (
+    Union,
+)
+
 from ..i18n import _
 from .. import (
     encoding,
@@ -24,11 +28,8 @@ from ..revlogutils import (
     constants as revlog_constants,
 )
 
-
-if pycompat.TYPE_CHECKING:
-    from typing import (
-        Union,
-    )
+# keeps pyflakes happy
+assert [Union]
 
 urlreq = urllibcompat.urlreq
 
diff --git a/mercurial/windows.py b/mercurial/windows.py
--- a/mercurial/windows.py
+++ b/mercurial/windows.py
@@ -61,13 +61,7 @@ testpid = win32.testpid
 unlink = win32.unlink
 
 if typing.TYPE_CHECKING:
-    # Replace the various overloads that come along with aliasing stdlib methods
-    # with the narrow definition that we care about in the type checking phase
-    # only.  This ensures that both Windows and POSIX see only the definition
-    # that is actually available.
-    #
-    # Note that if we check pycompat.TYPE_CHECKING here, it is always False, and
-    # the methods aren't replaced.
+
     def split(p: bytes) -> Tuple[bytes, bytes]:
         raise NotImplementedError