core: migrate code to benefit from 3.9 stuff

for now keeping ruff on 3.8 target version, need to sort out modules as well

my/core/cachew.py

@@ -1,4 +1,8 @@
-from .internal import assert_subpackage; assert_subpackage(__name__)
+from __future__ import annotations
+
+from .internal import assert_subpackage
+
+assert_subpackage(__name__)
 
 import logging
 import sys
@@ -9,8 +13,6 @@ from typing import (
     TYPE_CHECKING,
     Any,
     Callable,
-    Optional,
-    Type,
     TypeVar,
     Union,
     cast,
@@ -59,12 +61,12 @@ def _appdirs_cache_dir() -> Path:
 _CACHE_DIR_NONE_HACK = Path('/tmp/hpi/cachew_none_hack')
 
 
-def cache_dir(suffix: Optional[PathIsh] = None) -> Path:
+def cache_dir(suffix: PathIsh | None = None) -> Path:
     from . import core_config as CC
 
     cdir_ = CC.config.get_cache_dir()
 
-    sp: Optional[Path] = None
+    sp: Path | None = None
     if suffix is not None:
         sp = Path(suffix)
         # guess if you do need absolute, better path it directly instead of as suffix?
@@ -143,21 +145,19 @@ if TYPE_CHECKING:
     # we need two versions due to @doublewrap
     # this is when we just annotate as @cachew without any args
     @overload  # type: ignore[no-overload-impl]
-    def mcachew(fun: F) -> F:
-        ...
+    def mcachew(fun: F) -> F: ...
 
     @overload
     def mcachew(
-        cache_path: Optional[PathProvider] = ...,
+        cache_path: PathProvider | None = ...,
         *,
         force_file: bool = ...,
-        cls: Optional[Type] = ...,
+        cls: type | None = ...,
         depends_on: HashFunction = ...,
-        logger: Optional[logging.Logger] = ...,
+        logger: logging.Logger | None = ...,
         chunk_by: int = ...,
-        synthetic_key: Optional[str] = ...,
-    ) -> Callable[[F], F]:
-        ...
+        synthetic_key: str | None = ...,
+    ) -> Callable[[F], F]: ...
 
 else:
     mcachew = _mcachew_impl