diff --git a/src/_pytest/config/__init__.py b/src/_pytest/config/__init__.py
index 45aa4d9a824..8232a606538 100644
--- a/src/_pytest/config/__init__.py
+++ b/src/_pytest/config/__init__.py
@@ -282,7 +282,7 @@ class PytestPluginManager(PluginManager):
     * ``conftest.py`` loading during start-up;
     """
 
-    def __init__(self):
+    def __init__(self) -> None:
         import _pytest.assertion
 
         super().__init__("pytest")
@@ -362,7 +362,7 @@ def parse_hookspec_opts(self, module_or_class, name):
                 }
         return opts
 
-    def register(self, plugin, name=None):
+    def register(self, plugin: _PluggyPlugin, name: Optional[str] = None):
         if name in _pytest.deprecated.DEPRECATED_EXTERNAL_PLUGINS:
             warnings.warn(
                 PytestConfigWarning(
@@ -522,7 +522,7 @@ def _importconftest(self, conftestpath):
     #
     #
 
-    def consider_preparse(self, args, *, exclude_only=False):
+    def consider_preparse(self, args, *, exclude_only: bool = False) -> None:
         i = 0
         n = len(args)
         while i < n:
@@ -543,7 +543,7 @@ def consider_preparse(self, args, *, exclude_only=False):
                     continue
                 self.consider_pluginarg(parg)
 
-    def consider_pluginarg(self, arg):
+    def consider_pluginarg(self, arg) -> None:
         if arg.startswith("no:"):
             name = arg[3:]
             if name in essential_plugins:
@@ -568,13 +568,13 @@ def consider_pluginarg(self, arg):
                     del self._name2plugin["pytest_" + name]
             self.import_plugin(arg, consider_entry_points=True)
 
-    def consider_conftest(self, conftestmodule):
+    def consider_conftest(self, conftestmodule) -> None:
         self.register(conftestmodule, name=conftestmodule.__file__)
 
-    def consider_env(self):
+    def consider_env(self) -> None:
         self._import_plugin_specs(os.environ.get("PYTEST_PLUGINS"))
 
-    def consider_module(self, mod):
+    def consider_module(self, mod: types.ModuleType) -> None:
         self._import_plugin_specs(getattr(mod, "pytest_plugins", []))
 
     def _import_plugin_specs(self, spec):
@@ -582,7 +582,7 @@ def _import_plugin_specs(self, spec):
         for import_spec in plugins:
             self.import_plugin(import_spec)
 
-    def import_plugin(self, modname, consider_entry_points=False):
+    def import_plugin(self, modname: str, consider_entry_points: bool = False) -> None:
         """
         Imports a plugin with ``modname``. If ``consider_entry_points`` is True, entry point
         names are also considered to find a plugin.
@@ -766,7 +766,12 @@ class InvocationParams:
         plugins = attr.ib()
         dir = attr.ib(type=Path)
 
-    def __init__(self, pluginmanager, *, invocation_params=None) -> None:
+    def __init__(
+        self,
+        pluginmanager: PytestPluginManager,
+        *,
+        invocation_params: Optional[InvocationParams] = None
+    ) -> None:
         from .argparsing import Parser, FILE_OR_DIR
 
         if invocation_params is None:
@@ -800,19 +805,19 @@ def invocation_dir(self):
         """Backward compatibility"""
         return py.path.local(str(self.invocation_params.dir))
 
-    def add_cleanup(self, func):
+    def add_cleanup(self, func) -> None:
         """ Add a function to be called when the config object gets out of
         use (usually coninciding with pytest_unconfigure)."""
         self._cleanup.append(func)
 
-    def _do_configure(self):
+    def _do_configure(self) -> None:
         assert not self._configured
         self._configured = True
         with warnings.catch_warnings():
             warnings.simplefilter("default")
             self.hook.pytest_configure.call_historic(kwargs=dict(config=self))
 
-    def _ensure_unconfigure(self):
+    def _ensure_unconfigure(self) -> None:
         if self._configured:
             self._configured = False
             self.hook.pytest_unconfigure(config=self)
diff --git a/src/_pytest/mark/__init__.py b/src/_pytest/mark/__init__.py
index f493bd839f1..0779ed14bd3 100644
--- a/src/_pytest/mark/__init__.py
+++ b/src/_pytest/mark/__init__.py
@@ -8,6 +8,7 @@
 from .structures import MarkDecorator
 from .structures import MarkGenerator
 from .structures import ParameterSet
+from _pytest.config import Config
 from _pytest.config import hookimpl
 from _pytest.config import UsageError
 
@@ -94,7 +95,7 @@ def pytest_cmdline_main(config):
         return 0
 
 
-def deselect_by_keyword(items, config):
+def deselect_by_keyword(items, config: Config) -> None:
     keywordexpr = config.option.keyword.lstrip()
     if not keywordexpr:
         return
@@ -121,7 +122,7 @@ def deselect_by_keyword(items, config):
         items[:] = remaining
 
 
-def deselect_by_mark(items, config):
+def deselect_by_mark(items, config: Config) -> None:
     matchexpr = config.option.markexpr
     if not matchexpr:
         return
@@ -139,7 +140,7 @@ def deselect_by_mark(items, config):
         items[:] = remaining
 
 
-def pytest_collection_modifyitems(items, config):
+def pytest_collection_modifyitems(items, config: Config) -> None:
     deselect_by_keyword(items, config)
     deselect_by_mark(items, config)
 
diff --git a/src/_pytest/mark/structures.py b/src/_pytest/mark/structures.py
index 1ab22b7c758..fec1f9c5902 100644
--- a/src/_pytest/mark/structures.py
+++ b/src/_pytest/mark/structures.py
@@ -152,7 +152,7 @@ class Mark:
     #: resolved/generated ids with parametrize Marks
     _param_ids_generated = attr.ib(type=Optional[List[str]], default=None, repr=False)
 
-    def _has_param_ids(self):
+    def _has_param_ids(self) -> bool:
         return "ids" in self.kwargs or len(self.args) >= 4
 
     def combined_with(self, other: "Mark") -> "Mark":
@@ -215,10 +215,10 @@ def test_function():
 
     """
 
-    mark = attr.ib(validator=attr.validators.instance_of(Mark))
+    mark = attr.ib(type=Mark, validator=attr.validators.instance_of(Mark))
 
     @property
-    def name(self):
+    def name(self) -> str:
         """alias for mark.name"""
         return self.mark.name
 
@@ -233,13 +233,13 @@ def kwargs(self):
         return self.mark.kwargs
 
     @property
-    def markname(self):
+    def markname(self) -> str:
         return self.name  # for backward-compat (2.4.1 had this attr)
 
-    def __repr__(self):
+    def __repr__(self) -> str:
         return "<MarkDecorator {!r}>".format(self.mark)
 
-    def with_args(self, *args, **kwargs):
+    def with_args(self, *args, **kwargs) -> "MarkDecorator":
         """ return a MarkDecorator with extra arguments added
 
         unlike call this can be used even if the sole argument is a callable/class
@@ -262,7 +262,7 @@ def __call__(self, *args, **kwargs):
         return self.with_args(*args, **kwargs)
 
 
-def get_unpacked_marks(obj):
+def get_unpacked_marks(obj) -> List[Mark]:
     """
     obtain the unpacked marks that are stored on an object
     """
@@ -288,7 +288,7 @@ def normalize_mark_list(mark_list: Iterable[Union[Mark, MarkDecorator]]) -> List
     return [x for x in extracted if isinstance(x, Mark)]
 
 
-def store_mark(obj, mark):
+def store_mark(obj, mark: Mark) -> None:
     """store a Mark on an object
     this is used to implement the Mark declarations/decorators correctly
     """
@@ -387,8 +387,8 @@ def _seen(self):
             seen.update(self.parent.keywords)
         return seen
 
-    def __len__(self):
+    def __len__(self) -> int:
         return len(self._seen())
 
-    def __repr__(self):
+    def __repr__(self) -> str:
         return "<NodeKeywords for node {}>".format(self.node)
diff --git a/src/_pytest/nodes.py b/src/_pytest/nodes.py
index 81a25ddd5c2..a57503b4676 100644
--- a/src/_pytest/nodes.py
+++ b/src/_pytest/nodes.py
@@ -2,6 +2,7 @@
 import warnings
 from functools import lru_cache
 from typing import Any
+from typing import Callable
 from typing import Dict
 from typing import List
 from typing import Optional
@@ -292,7 +293,7 @@ def listextrakeywords(self):
     def listnames(self):
         return [x.name for x in self.listchain()]
 
-    def addfinalizer(self, fin):
+    def addfinalizer(self, fin: Callable[[], object]) -> None:
         """ register a function to be called when this node is finalized.
 
         This method can only be called when this node is active
diff --git a/src/_pytest/runner.py b/src/_pytest/runner.py
index e10e4d8bdf0..325c6d9dcaf 100644
--- a/src/_pytest/runner.py
+++ b/src/_pytest/runner.py
@@ -289,9 +289,9 @@ class SetupState:
 
     def __init__(self):
         self.stack = []  # type: List[Node]
-        self._finalizers = {}  # type: Dict[Node, List[Callable[[], None]]]
+        self._finalizers = {}  # type: Dict[Node, List[Callable[[], object]]]
 
-    def addfinalizer(self, finalizer, colitem):
+    def addfinalizer(self, finalizer: Callable[[], object], colitem) -> None:
         """ attach a finalizer to the given colitem. """
         assert colitem and not isinstance(colitem, tuple)
         assert callable(finalizer)
@@ -302,7 +302,7 @@ def _pop_and_teardown(self):
         colitem = self.stack.pop()
         self._teardown_with_finalization(colitem)
 
-    def _callfinalizers(self, colitem):
+    def _callfinalizers(self, colitem) -> None:
         finalizers = self._finalizers.pop(colitem, None)
         exc = None
         while finalizers:
@@ -319,24 +319,24 @@ def _callfinalizers(self, colitem):
             assert val is not None
             raise val.with_traceback(tb)
 
-    def _teardown_with_finalization(self, colitem):
+    def _teardown_with_finalization(self, colitem) -> None:
         self._callfinalizers(colitem)
         colitem.teardown()
         for colitem in self._finalizers:
             assert colitem in self.stack
 
-    def teardown_all(self):
+    def teardown_all(self) -> None:
         while self.stack:
             self._pop_and_teardown()
         for key in list(self._finalizers):
             self._teardown_with_finalization(key)
         assert not self._finalizers
 
-    def teardown_exact(self, item, nextitem):
+    def teardown_exact(self, item, nextitem) -> None:
         needed_collectors = nextitem and nextitem.listchain() or []
         self._teardown_towards(needed_collectors)
 
-    def _teardown_towards(self, needed_collectors):
+    def _teardown_towards(self, needed_collectors) -> None:
         exc = None
         while self.stack:
             if self.stack == needed_collectors[: len(self.stack)]:
@@ -353,7 +353,7 @@ def _teardown_towards(self, needed_collectors):
             assert val is not None
             raise val.with_traceback(tb)
 
-    def prepare(self, colitem):
+    def prepare(self, colitem) -> None:
         """ setup objects along the collector chain to the test-method
             and teardown previously setup objects."""
         needed_collectors = colitem.listchain()
@@ -362,14 +362,14 @@ def prepare(self, colitem):
         # check if the last collection node has raised an error
         for col in self.stack:
             if hasattr(col, "_prepare_exc"):
-                _, val, tb = col._prepare_exc
+                _, val, tb = col._prepare_exc  # type: ignore[attr-defined] # noqa: F821
                 raise val.with_traceback(tb)
         for col in needed_collectors[len(self.stack) :]:
             self.stack.append(col)
             try:
                 col.setup()
             except TEST_OUTCOME:
-                col._prepare_exc = sys.exc_info()
+                col._prepare_exc = sys.exc_info()  # type: ignore[attr-defined] # noqa: F821
                 raise
 
 
diff --git a/src/_pytest/warnings.py b/src/_pytest/warnings.py
index 18e4def2116..ae82ed79f91 100644
--- a/src/_pytest/warnings.py
+++ b/src/_pytest/warnings.py
@@ -7,7 +7,7 @@
 from _pytest.main import Session
 
 
-def _setoption(wmod, arg):
+def _setoption(wmod, arg) -> None:
     """
     Copy of the warning._setoption function but does not escape arguments.
     """