diff --git a/scrapy/commands/__init__.py b/scrapy/commands/__init__.py
index 9baee3a48..2aa569cdd 100644
--- a/scrapy/commands/__init__.py
+++ b/scrapy/commands/__init__.py
@@ -4,7 +4,7 @@ Base class for Scrapy commands
 import argparse
 import os
 from pathlib import Path
-from typing import Any, Dict, Optional
+from typing import Any, Dict, List, Optional
 
 from twisted.python import failure
 
@@ -116,7 +116,7 @@ class ScrapyCommand:
         if opts.pdb:
             failure.startDebugMode()
 
-    def run(self, args, opts):
+    def run(self, args: List[str], opts: argparse.Namespace) -> None:
         """
         Entry point for running commands
         """
diff --git a/scrapy/commands/fetch.py b/scrapy/commands/fetch.py
index 1359e445f..cdb7ad4ae 100644
--- a/scrapy/commands/fetch.py
+++ b/scrapy/commands/fetch.py
@@ -1,7 +1,10 @@
 import sys
+from argparse import Namespace
+from typing import List, Type
 
 from w3lib.url import is_url
 
+from scrapy import Spider
 from scrapy.commands import ScrapyCommand
 from scrapy.exceptions import UsageError
 from scrapy.http import Request
@@ -57,7 +60,7 @@ class Command(ScrapyCommand):
     def _print_bytes(self, bytes_):
         sys.stdout.buffer.write(bytes_ + b"\n")
 
-    def run(self, args, opts):
+    def run(self, args: List[str], opts: Namespace) -> None:
         if len(args) != 1 or not is_url(args[0]):
             raise UsageError()
         request = Request(
@@ -73,7 +76,8 @@ class Command(ScrapyCommand):
         else:
             request.meta["handle_httpstatus_all"] = True
 
-        spidercls = DefaultSpider
+        spidercls: Type[Spider] = DefaultSpider
+        assert self.crawler_process
         spider_loader = self.crawler_process.spider_loader
         if opts.spider:
             spidercls = spider_loader.load(opts.spider)
diff --git a/scrapy/commands/shell.py b/scrapy/commands/shell.py
index 63c23d04c..0a5e61f7a 100644
--- a/scrapy/commands/shell.py
+++ b/scrapy/commands/shell.py
@@ -3,8 +3,11 @@ Scrapy Shell
 
 See documentation in docs/topics/shell.rst
 """
+from argparse import Namespace
 from threading import Thread
+from typing import List, Type
 
+from scrapy import Spider
 from scrapy.commands import ScrapyCommand
 from scrapy.http import Request
 from scrapy.shell import Shell
@@ -54,15 +57,16 @@ class Command(ScrapyCommand):
         """
         pass
 
-    def run(self, args, opts):
+    def run(self, args: List[str], opts: Namespace) -> None:
         url = args[0] if args else None
         if url:
             # first argument may be a local file
             url = guess_scheme(url)
 
+        assert self.crawler_process
         spider_loader = self.crawler_process.spider_loader
 
-        spidercls = DefaultSpider
+        spidercls: Type[Spider] = DefaultSpider
         if opts.spider:
             spidercls = spider_loader.load(opts.spider)
         elif url:
diff --git a/scrapy/http/response/text.py b/scrapy/http/response/text.py
index f228e11c1..7fc54b5d3 100644
--- a/scrapy/http/response/text.py
+++ b/scrapy/http/response/text.py
@@ -4,10 +4,11 @@ discovering (through HTTP headers) to base Response class.
 
 See documentation in docs/topics/request-response.rst
 """
+from __future__ import annotations
 
 import json
 from contextlib import suppress
-from typing import Generator, Optional, Tuple
+from typing import TYPE_CHECKING, Any, Generator, Optional, Tuple
 from urllib.parse import urljoin
 
 import parsel
@@ -25,6 +26,9 @@ from scrapy.http.response import Response
 from scrapy.utils.python import memoizemethod_noargs, to_unicode
 from scrapy.utils.response import get_base_url
 
+if TYPE_CHECKING:
+    from scrapy.selector import Selector
+
 _NONE = object()
 
 
@@ -34,11 +38,11 @@ class TextResponse(Response):
 
     attributes: Tuple[str, ...] = Response.attributes + ("encoding",)
 
-    def __init__(self, *args, **kwargs):
+    def __init__(self, *args: Any, **kwargs: Any):
         self._encoding = kwargs.pop("encoding", None)
-        self._cached_benc = None
+        self._cached_benc: Optional[str] = None
         self._cached_ubody: Optional[str] = None
-        self._cached_selector = None
+        self._cached_selector: Optional[Selector] = None
         super().__init__(*args, **kwargs)
 
     def _set_url(self, url):
diff --git a/scrapy/spiderloader.py b/scrapy/spiderloader.py
index 13d6f9f87..f6bb93ddc 100644
--- a/scrapy/spiderloader.py
+++ b/scrapy/spiderloader.py
@@ -27,7 +27,7 @@ class SpiderLoader:
         self._found: DefaultDict[str, List[Tuple[str, str]]] = defaultdict(list)
         self._load_all_spiders()
 
-    def _check_name_duplicates(self):
+    def _check_name_duplicates(self) -> None:
         dupes = []
         for name, locations in self._found.items():
             dupes.extend(
diff --git a/scrapy/utils/ossignal.py b/scrapy/utils/ossignal.py
index f835a2221..2334ea792 100644
--- a/scrapy/utils/ossignal.py
+++ b/scrapy/utils/ossignal.py
@@ -1,7 +1,13 @@
 import signal
-from typing import Callable
+from types import FrameType
+from typing import Any, Callable, Dict, Optional, Union
 
-signal_names = {}
+# copy of _HANDLER from typeshed/stdlib/signal.pyi
+SignalHandlerT = Union[
+    Callable[[int, Optional[FrameType]], Any], int, signal.Handlers, None
+]
+
+signal_names: Dict[int, str] = {}
 for signame in dir(signal):
     if signame.startswith("SIG") and not signame.startswith("SIG_"):
         signum = getattr(signal, signame)
@@ -9,7 +15,9 @@ for signame in dir(signal):
             signal_names[signum] = signame
 
 
-def install_shutdown_handlers(function: Callable, override_sigint: bool = True) -> None:
+def install_shutdown_handlers(
+    function: SignalHandlerT, override_sigint: bool = True
+) -> None:
     """Install the given function as a signal handler for all common shutdown
     signals (such as SIGINT, SIGTERM, etc). If override_sigint is ``False`` the
     SIGINT handler won't be install if there is already a handler in place
diff --git a/scrapy/utils/spider.py b/scrapy/utils/spider.py
index 3228eda49..704df8657 100644
--- a/scrapy/utils/spider.py
+++ b/scrapy/utils/spider.py
@@ -2,16 +2,19 @@ from __future__ import annotations
 
 import inspect
 import logging
-from types import ModuleType
+from types import CoroutineType, ModuleType
 from typing import (
     TYPE_CHECKING,
     Any,
-    AsyncIterable,
+    AsyncGenerator,
     Generator,
     Iterable,
+    Literal,
     Optional,
     Type,
+    TypeVar,
     Union,
+    overload,
 )
 
 from twisted.internet.defer import Deferred
@@ -26,8 +29,26 @@ if TYPE_CHECKING:
 
 logger = logging.getLogger(__name__)
 
+_T = TypeVar("_T")
 
-def iterate_spider_output(result: Any) -> Union[Iterable, AsyncIterable, Deferred]:
+
+# https://stackoverflow.com/questions/60222982
+@overload
+def iterate_spider_output(result: AsyncGenerator) -> AsyncGenerator:  # type: ignore[misc]
+    ...
+
+
+@overload
+def iterate_spider_output(result: CoroutineType) -> Deferred:
+    ...
+
+
+@overload
+def iterate_spider_output(result: _T) -> Iterable:
+    ...
+
+
+def iterate_spider_output(result: Any) -> Union[Iterable, AsyncGenerator, Deferred]:
     if inspect.isasyncgen(result):
         return result
     if inspect.iscoroutine(result):
@@ -55,6 +76,39 @@ def iter_spider_classes(module: ModuleType) -> Generator[Type[Spider], Any, None
             yield obj
 
 
+@overload
+def spidercls_for_request(
+    spider_loader: SpiderLoader,
+    request: Request,
+    default_spidercls: Type[Spider],
+    log_none: bool = ...,
+    log_multiple: bool = ...,
+) -> Type[Spider]:
+    ...
+
+
+@overload
+def spidercls_for_request(
+    spider_loader: SpiderLoader,
+    request: Request,
+    default_spidercls: Literal[None],
+    log_none: bool = ...,
+    log_multiple: bool = ...,
+) -> Optional[Type[Spider]]:
+    ...
+
+
+@overload
+def spidercls_for_request(
+    spider_loader: SpiderLoader,
+    request: Request,
+    *,
+    log_none: bool = ...,
+    log_multiple: bool = ...,
+) -> Optional[Type[Spider]]:
+    ...
+
+
 def spidercls_for_request(
     spider_loader: SpiderLoader,
     request: Request,