diff --git a/src/_pytest/_code/__init__.py b/src/_pytest/_code/__init__.py
index 38019298c..76963c0eb 100644
--- a/src/_pytest/_code/__init__.py
+++ b/src/_pytest/_code/__init__.py
@@ -6,6 +6,7 @@ from .code import Frame
 from .code import getfslineno
 from .code import getrawcode
 from .code import Traceback
+from .code import TracebackEntry
 from .source import compile_ as compile
 from .source import Source
 
@@ -17,6 +18,7 @@ __all__ = [
     "getfslineno",
     "getrawcode",
     "Traceback",
+    "TracebackEntry",
     "compile",
     "Source",
 ]
diff --git a/src/_pytest/_code/code.py b/src/_pytest/_code/code.py
index 65e5aa6d5..e548bceb7 100644
--- a/src/_pytest/_code/code.py
+++ b/src/_pytest/_code/code.py
@@ -213,7 +213,7 @@ class TracebackEntry:
         return source.getstatement(self.lineno)
 
     @property
-    def path(self):
+    def path(self) -> Union[py.path.local, str]:
         """ path to the source code """
         return self.frame.code.path
 
diff --git a/src/_pytest/config/__init__.py b/src/_pytest/config/__init__.py
index b4a5a70ad..717743e79 100644
--- a/src/_pytest/config/__init__.py
+++ b/src/_pytest/config/__init__.py
@@ -1,5 +1,6 @@
 """ command line options, ini-file and conftest.py processing. """
 import argparse
+import collections.abc
 import contextlib
 import copy
 import enum
@@ -15,10 +16,13 @@ from typing import Any
 from typing import Callable
 from typing import Dict
 from typing import IO
+from typing import Iterable
+from typing import Iterator
 from typing import List
 from typing import Optional
 from typing import Sequence
 from typing import Set
+from typing import TextIO
 from typing import Tuple
 from typing import Union
 
@@ -42,6 +46,7 @@ from _pytest.compat import TYPE_CHECKING
 from _pytest.outcomes import fail
 from _pytest.outcomes import Skipped
 from _pytest.pathlib import import_path
+from _pytest.pathlib import ImportMode
 from _pytest.pathlib import Path
 from _pytest.store import Store
 from _pytest.warning_types import PytestConfigWarning
@@ -50,6 +55,7 @@ if TYPE_CHECKING:
     from typing import Type
 
     from _pytest._code.code import _TracebackStyle
+    from _pytest.terminal import TerminalReporter
     from .argparsing import Argument
 
 
@@ -88,18 +94,24 @@ class ExitCode(enum.IntEnum):
 
 
 class ConftestImportFailure(Exception):
-    def __init__(self, path, excinfo):
+    def __init__(
+        self,
+        path: py.path.local,
+        excinfo: Tuple["Type[Exception]", Exception, TracebackType],
+    ) -> None:
         super().__init__(path, excinfo)
         self.path = path
-        self.excinfo = excinfo  # type: Tuple[Type[Exception], Exception, TracebackType]
+        self.excinfo = excinfo
 
-    def __str__(self):
+    def __str__(self) -> str:
         return "{}: {} (from {})".format(
             self.excinfo[0].__name__, self.excinfo[1], self.path
         )
 
 
-def filter_traceback_for_conftest_import_failure(entry) -> bool:
+def filter_traceback_for_conftest_import_failure(
+    entry: _pytest._code.TracebackEntry,
+) -> bool:
     """filters tracebacks entries which point to pytest internals or importlib.
 
     Make a special case for importlib because we use it to import test modules and conftest files
@@ -108,7 +120,10 @@ def filter_traceback_for_conftest_import_failure(entry) -> bool:
     return filter_traceback(entry) and "importlib" not in str(entry.path).split(os.sep)
 
 
-def main(args=None, plugins=None) -> Union[int, ExitCode]:
+def main(
+    args: Optional[List[str]] = None,
+    plugins: Optional[Sequence[Union[str, _PluggyPlugin]]] = None,
+) -> Union[int, ExitCode]:
     """ return exit code, after performing an in-process test run.
 
     :arg args: list of command line arguments.
@@ -177,7 +192,7 @@ class cmdline:  # compatibility namespace
     main = staticmethod(main)
 
 
-def filename_arg(path, optname):
+def filename_arg(path: str, optname: str) -> str:
     """ Argparse type validator for filename arguments.
 
     :path: path of filename
@@ -188,7 +203,7 @@ def filename_arg(path, optname):
     return path
 
 
-def directory_arg(path, optname):
+def directory_arg(path: str, optname: str) -> str:
     """Argparse type validator for directory arguments.
 
     :path: path of directory
@@ -239,13 +254,16 @@ builtin_plugins = set(default_plugins)
 builtin_plugins.add("pytester")
 
 
-def get_config(args=None, plugins=None):
+def get_config(
+    args: Optional[List[str]] = None,
+    plugins: Optional[Sequence[Union[str, _PluggyPlugin]]] = None,
+) -> "Config":
     # subsequent calls to main will create a fresh instance
     pluginmanager = PytestPluginManager()
     config = Config(
         pluginmanager,
         invocation_params=Config.InvocationParams(
-            args=args or (), plugins=plugins, dir=Path.cwd()
+            args=args or (), plugins=plugins, dir=Path.cwd(),
         ),
     )
 
@@ -255,10 +273,11 @@ def get_config(args=None, plugins=None):
 
     for spec in default_plugins:
         pluginmanager.import_plugin(spec)
+
     return config
 
 
-def get_plugin_manager():
+def get_plugin_manager() -> "PytestPluginManager":
     """
     Obtain a new instance of the
     :py:class:`_pytest.config.PytestPluginManager`, with default plugins
@@ -271,8 +290,9 @@ def get_plugin_manager():
 
 
 def _prepareconfig(
-    args: Optional[Union[py.path.local, List[str]]] = None, plugins=None
-):
+    args: Optional[Union[py.path.local, List[str]]] = None,
+    plugins: Optional[Sequence[Union[str, _PluggyPlugin]]] = None,
+) -> "Config":
     if args is None:
         args = sys.argv[1:]
     elif isinstance(args, py.path.local):
@@ -290,9 +310,10 @@ def _prepareconfig(
                     pluginmanager.consider_pluginarg(plugin)
                 else:
                     pluginmanager.register(plugin)
-        return pluginmanager.hook.pytest_cmdline_parse(
+        config = pluginmanager.hook.pytest_cmdline_parse(
             pluginmanager=pluginmanager, args=args
         )
+        return config
     except BaseException:
         config._ensure_unconfigure()
         raise
@@ -313,13 +334,11 @@ class PytestPluginManager(PluginManager):
 
         super().__init__("pytest")
         # The objects are module objects, only used generically.
-        self._conftest_plugins = set()  # type: Set[object]
+        self._conftest_plugins = set()  # type: Set[types.ModuleType]
 
-        # state related to local conftest plugins
-        # Maps a py.path.local to a list of module objects.
-        self._dirpath2confmods = {}  # type: Dict[Any, List[object]]
-        # Maps a py.path.local to a module object.
-        self._conftestpath2mod = {}  # type: Dict[Any, object]
+        # State related to local conftest plugins.
+        self._dirpath2confmods = {}  # type: Dict[py.path.local, List[types.ModuleType]]
+        self._conftestpath2mod = {}  # type: Dict[Path, types.ModuleType]
         self._confcutdir = None  # type: Optional[py.path.local]
         self._noconftest = False
         self._duplicatepaths = set()  # type: Set[py.path.local]
@@ -328,7 +347,7 @@ class PytestPluginManager(PluginManager):
         self.register(self)
         if os.environ.get("PYTEST_DEBUG"):
             err = sys.stderr  # type: IO[str]
-            encoding = getattr(err, "encoding", "utf8")
+            encoding = getattr(err, "encoding", "utf8")  # type: str
             try:
                 err = open(
                     os.dup(err.fileno()), mode=err.mode, buffering=1, encoding=encoding,
@@ -343,7 +362,7 @@ class PytestPluginManager(PluginManager):
         # Used to know when we are importing conftests after the pytest_configure stage
         self._configured = False
 
-    def parse_hookimpl_opts(self, plugin, name):
+    def parse_hookimpl_opts(self, plugin: _PluggyPlugin, name: str):
         # pytest hooks are always prefixed with pytest_
         # so we avoid accessing possibly non-readable attributes
         # (see issue #1073)
@@ -372,7 +391,7 @@ class PytestPluginManager(PluginManager):
                 opts.setdefault(name, hasattr(method, name) or name in known_marks)
         return opts
 
-    def parse_hookspec_opts(self, module_or_class, name):
+    def parse_hookspec_opts(self, module_or_class, name: str):
         opts = super().parse_hookspec_opts(module_or_class, name)
         if opts is None:
             method = getattr(module_or_class, name)
@@ -389,7 +408,9 @@ class PytestPluginManager(PluginManager):
                 }
         return opts
 
-    def register(self, plugin: _PluggyPlugin, name: Optional[str] = None):
+    def register(
+        self, plugin: _PluggyPlugin, name: Optional[str] = None
+    ) -> Optional[str]:
         if name in _pytest.deprecated.DEPRECATED_EXTERNAL_PLUGINS:
             warnings.warn(
                 PytestConfigWarning(
@@ -399,8 +420,8 @@ class PytestPluginManager(PluginManager):
                     )
                 )
             )
-            return
-        ret = super().register(plugin, name)
+            return None
+        ret = super().register(plugin, name)  # type: Optional[str]
         if ret:
             self.hook.pytest_plugin_registered.call_historic(
                 kwargs=dict(plugin=plugin, manager=self)
@@ -410,11 +431,12 @@ class PytestPluginManager(PluginManager):
                 self.consider_module(plugin)
         return ret
 
-    def getplugin(self, name):
+    def getplugin(self, name: str):
         # support deprecated naming because plugins (xdist e.g.) use it
-        return self.get_plugin(name)
+        plugin = self.get_plugin(name)  # type: Optional[_PluggyPlugin]
+        return plugin
 
-    def hasplugin(self, name):
+    def hasplugin(self, name: str) -> bool:
         """Return True if the plugin with the given name is registered."""
         return bool(self.get_plugin(name))
 
@@ -436,7 +458,7 @@ class PytestPluginManager(PluginManager):
     #
     # internal API for local conftest plugin handling
     #
-    def _set_initial_conftests(self, namespace):
+    def _set_initial_conftests(self, namespace: argparse.Namespace) -> None:
         """ load initial conftest files given a preparsed "namespace".
             As conftest files may add their own command line options
             which have arguments ('--my-opt somepath') we might get some
@@ -454,8 +476,8 @@ class PytestPluginManager(PluginManager):
         self._using_pyargs = namespace.pyargs
         testpaths = namespace.file_or_dir
         foundanchor = False
-        for path in testpaths:
-            path = str(path)
+        for testpath in testpaths:
+            path = str(testpath)
             # remove node-id syntax
             i = path.find("::")
             if i != -1:
@@ -467,7 +489,9 @@ class PytestPluginManager(PluginManager):
         if not foundanchor:
             self._try_load_conftest(current, namespace.importmode)
 
-    def _try_load_conftest(self, anchor, importmode):
+    def _try_load_conftest(
+        self, anchor: py.path.local, importmode: Union[str, ImportMode]
+    ) -> None:
         self._getconftestmodules(anchor, importmode)
         # let's also consider test* subdirs
         if anchor.check(dir=1):
@@ -476,7 +500,9 @@ class PytestPluginManager(PluginManager):
                     self._getconftestmodules(x, importmode)
 
     @lru_cache(maxsize=128)
-    def _getconftestmodules(self, path, importmode):
+    def _getconftestmodules(
+        self, path: py.path.local, importmode: Union[str, ImportMode],
+    ) -> List[types.ModuleType]:
         if self._noconftest:
             return []
 
@@ -499,7 +525,9 @@ class PytestPluginManager(PluginManager):
         self._dirpath2confmods[directory] = clist
         return clist
 
-    def _rget_with_confmod(self, name, path, importmode):
+    def _rget_with_confmod(
+        self, name: str, path: py.path.local, importmode: Union[str, ImportMode],
+    ) -> Tuple[types.ModuleType, Any]:
         modules = self._getconftestmodules(path, importmode)
         for mod in reversed(modules):
             try:
@@ -508,7 +536,9 @@ class PytestPluginManager(PluginManager):
                 continue
         raise KeyError(name)
 
-    def _importconftest(self, conftestpath, importmode):
+    def _importconftest(
+        self, conftestpath: py.path.local, importmode: Union[str, ImportMode],
+    ) -> types.ModuleType:
         # Use a resolved Path object as key to avoid loading the same conftest twice
         # with build systems that create build directories containing
         # symlinks to actual files.
@@ -526,7 +556,9 @@ class PytestPluginManager(PluginManager):
         try:
             mod = import_path(conftestpath, mode=importmode)
         except Exception as e:
-            raise ConftestImportFailure(conftestpath, sys.exc_info()) from e
+            assert e.__traceback__ is not None
+            exc_info = (type(e), e, e.__traceback__)
+            raise ConftestImportFailure(conftestpath, exc_info) from e
 
         self._check_non_top_pytest_plugins(mod, conftestpath)
 
@@ -542,7 +574,9 @@ class PytestPluginManager(PluginManager):
         self.consider_conftest(mod)
         return mod
 
-    def _check_non_top_pytest_plugins(self, mod, conftestpath):
+    def _check_non_top_pytest_plugins(
+        self, mod: types.ModuleType, conftestpath: py.path.local,
+    ) -> None:
         if (
             hasattr(mod, "pytest_plugins")
             and self._configured
@@ -564,7 +598,9 @@ class PytestPluginManager(PluginManager):
     #
     #
 
-    def consider_preparse(self, args, *, exclude_only: bool = False) -> None:
+    def consider_preparse(
+        self, args: Sequence[str], *, exclude_only: bool = False
+    ) -> None:
         i = 0
         n = len(args)
         while i < n:
@@ -585,7 +621,7 @@ class PytestPluginManager(PluginManager):
                     continue
                 self.consider_pluginarg(parg)
 
-    def consider_pluginarg(self, arg) -> None:
+    def consider_pluginarg(self, arg: str) -> None:
         if arg.startswith("no:"):
             name = arg[3:]
             if name in essential_plugins:
@@ -610,7 +646,7 @@ class PytestPluginManager(PluginManager):
                     del self._name2plugin["pytest_" + name]
             self.import_plugin(arg, consider_entry_points=True)
 
-    def consider_conftest(self, conftestmodule) -> None:
+    def consider_conftest(self, conftestmodule: types.ModuleType) -> None:
         self.register(conftestmodule, name=conftestmodule.__file__)
 
     def consider_env(self) -> None:
@@ -619,7 +655,9 @@ class PytestPluginManager(PluginManager):
     def consider_module(self, mod: types.ModuleType) -> None:
         self._import_plugin_specs(getattr(mod, "pytest_plugins", []))
 
-    def _import_plugin_specs(self, spec):
+    def _import_plugin_specs(
+        self, spec: Union[None, types.ModuleType, str, Sequence[str]]
+    ) -> None:
         plugins = _get_plugin_specs_as_list(spec)
         for import_spec in plugins:
             self.import_plugin(import_spec)
@@ -636,7 +674,6 @@ class PytestPluginManager(PluginManager):
         assert isinstance(modname, str), (
             "module name as text required, got %r" % modname
         )
-        modname = str(modname)
         if self.is_blocked(modname) or self.get_plugin(modname) is not None:
             return
 
@@ -668,27 +705,29 @@ class PytestPluginManager(PluginManager):
             self.register(mod, modname)
 
 
-def _get_plugin_specs_as_list(specs):
-    """
-    Parses a list of "plugin specs" and returns a list of plugin names.
-
-    Plugin specs can be given as a list of strings separated by "," or already as a list/tuple in
-    which case it is returned as a list. Specs can also be `None` in which case an
-    empty list is returned.
-    """
-    if specs is not None and not isinstance(specs, types.ModuleType):
-        if isinstance(specs, str):
-            specs = specs.split(",") if specs else []
-        if not isinstance(specs, (list, tuple)):
-            raise UsageError(
-                "Plugin specs must be a ','-separated string or a "
-                "list/tuple of strings for plugin names. Given: %r" % specs
-            )
+def _get_plugin_specs_as_list(
+    specs: Union[None, types.ModuleType, str, Sequence[str]]
+) -> List[str]:
+    """Parse a plugins specification into a list of plugin names."""
+    # None means empty.
+    if specs is None:
+        return []
+    # Workaround for #3899 - a submodule which happens to be called "pytest_plugins".
+    if isinstance(specs, types.ModuleType):
+        return []
+    # Comma-separated list.
+    if isinstance(specs, str):
+        return specs.split(",") if specs else []
+    # Direct specification.
+    if isinstance(specs, collections.abc.Sequence):
         return list(specs)
-    return []
+    raise UsageError(
+        "Plugins may be specified as a sequence or a ','-separated string of plugin names. Got: %r"
+        % specs
+    )
 
 
-def _ensure_removed_sysmodule(modname):
+def _ensure_removed_sysmodule(modname: str) -> None:
     try:
         del sys.modules[modname]
     except KeyError:
@@ -703,7 +742,7 @@ class Notset:
 notset = Notset()
 
 
-def _iter_rewritable_modules(package_files):
+def _iter_rewritable_modules(package_files: Iterable[str]) -> Iterator[str]:
     """
     Given an iterable of file names in a source distribution, return the "names" that should
     be marked for assertion rewrite (for example the package "pytest_mock/__init__.py" should
@@ -766,6 +805,10 @@ def _iter_rewritable_modules(package_files):
             yield from _iter_rewritable_modules(new_package_files)
 
 
+def _args_converter(args: Iterable[str]) -> Tuple[str, ...]:
+    return tuple(args)
+
+
 class Config:
     """
     Access to configuration values, pluginmanager and plugin hooks.
@@ -793,9 +836,9 @@ class Config:
             Plugins accessing ``InvocationParams`` must be aware of that.
         """
 
-        args = attr.ib(converter=tuple)
+        args = attr.ib(type=Tuple[str, ...], converter=_args_converter)
         """tuple of command-line arguments as passed to ``pytest.main()``."""
-        plugins = attr.ib()
+        plugins = attr.ib(type=Optional[Sequence[Union[str, _PluggyPlugin]]])
         """list of extra plugins, might be `None`."""
         dir = attr.ib(type=Path)
         """directory where ``pytest.main()`` was invoked from."""
@@ -855,7 +898,7 @@ class Config:
         """Backward compatibility"""
         return py.path.local(str(self.invocation_params.dir))
 
-    def add_cleanup(self, func) -> None:
+    def add_cleanup(self, func: Callable[[], None]) -> None:
         """ Add a function to be called when the config object gets out of
         use (usually coninciding with pytest_unconfigure)."""
         self._cleanup.append(func)
@@ -876,12 +919,15 @@ class Config:
             fin = self._cleanup.pop()
             fin()
 
-    def get_terminal_writer(self):
-        return self.pluginmanager.get_plugin("terminalreporter")._tw
+    def get_terminal_writer(self) -> TerminalWriter:
+        terminalreporter = self.pluginmanager.get_plugin(
+            "terminalreporter"
+        )  # type: TerminalReporter
+        return terminalreporter._tw
 
     def pytest_cmdline_parse(
         self, pluginmanager: PytestPluginManager, args: List[str]
-    ) -> object:
+    ) -> "Config":
         try:
             self.parse(args)
         except UsageError:
@@ -923,7 +969,7 @@ class Config:
                 sys.stderr.write("INTERNALERROR> %s\n" % line)
                 sys.stderr.flush()
 
-    def cwd_relative_nodeid(self, nodeid):
+    def cwd_relative_nodeid(self, nodeid: str) -> str:
         # nodeid's are relative to the rootpath, compute relative to cwd
         if self.invocation_dir != self.rootdir:
             fullpath = self.rootdir.join(nodeid)
@@ -931,7 +977,7 @@ class Config:
         return nodeid
 
     @classmethod
-    def fromdictargs(cls, option_dict, args):
+    def fromdictargs(cls, option_dict, args) -> "Config":
         """ constructor usable for subprocesses. """
         config = get_config(args)
         config.option.__dict__.update(option_dict)
@@ -949,7 +995,7 @@ class Config:
                 setattr(self.option, opt.dest, opt.default)
 
     @hookimpl(trylast=True)
-    def pytest_load_initial_conftests(self, early_config):
+    def pytest_load_initial_conftests(self, early_config: "Config") -> None:
         self.pluginmanager._set_initial_conftests(early_config.known_args_namespace)
 
     def _initini(self, args: Sequence[str]) -> None:
@@ -1078,7 +1124,7 @@ class Config:
                 raise
         self._validate_keys()
 
-    def _checkversion(self):
+    def _checkversion(self) -> None:
         import pytest
 
         minver = self.inicfg.get("minversion", None)
@@ -1167,7 +1213,7 @@ class Config:
         except PrintHelp:
             pass
 
-    def addinivalue_line(self, name, line):
+    def addinivalue_line(self, name: str, line: str) -> None:
         """ add a line to an ini-file option. The option must have been
         declared but might not yet be set in which case the line becomes the
         the first line in its value. """
@@ -1186,7 +1232,7 @@ class Config:
             self._inicache[name] = val = self._getini(name)
             return val
 
-    def _getini(self, name: str) -> Any:
+    def _getini(self, name: str):
         try:
             description, type, default = self._parser._inidict[name]
         except KeyError as e:
@@ -1231,12 +1277,14 @@ class Config:
             else:
                 return value
         elif type == "bool":
-            return bool(_strtobool(str(value).strip()))
+            return _strtobool(str(value).strip())
         else:
             assert type is None
             return value
 
-    def _getconftest_pathlist(self, name, path):
+    def _getconftest_pathlist(
+        self, name: str, path: py.path.local
+    ) -> Optional[List[py.path.local]]:
         try:
             mod, relroots = self.pluginmanager._rget_with_confmod(
                 name, path, self.getoption("importmode")
@@ -1244,7 +1292,7 @@ class Config:
         except KeyError:
             return None
         modpath = py.path.local(mod.__file__).dirpath()
-        values = []
+        values = []  # type: List[py.path.local]
         for relroot in relroots:
             if not isinstance(relroot, py.path.local):
                 relroot = relroot.replace("/", py.path.local.sep)
@@ -1295,16 +1343,16 @@ class Config:
                 pytest.skip("no {!r} option found".format(name))
             raise ValueError("no option named {!r}".format(name)) from e
 
-    def getvalue(self, name, path=None):
+    def getvalue(self, name: str, path=None):
         """ (deprecated, use getoption()) """
         return self.getoption(name)
 
-    def getvalueorskip(self, name, path=None):
+    def getvalueorskip(self, name: str, path=None):
         """ (deprecated, use getoption(skip=True)) """
         return self.getoption(name, skip=True)
 
 
-def _assertion_supported():
+def _assertion_supported() -> bool:
     try:
         assert False
     except AssertionError:
@@ -1313,7 +1361,7 @@ def _assertion_supported():
         return False
 
 
-def _warn_about_missing_assertion(mode):
+def _warn_about_missing_assertion(mode) -> None:
     if not _assertion_supported():
         if mode == "plain":
             sys.stderr.write(
@@ -1331,12 +1379,14 @@ def _warn_about_missing_assertion(mode):
             )
 
 
-def create_terminal_writer(config: Config, *args, **kwargs) -> TerminalWriter:
+def create_terminal_writer(
+    config: Config, file: Optional[TextIO] = None
+) -> TerminalWriter:
     """Create a TerminalWriter instance configured according to the options
     in the config object. Every code which requires a TerminalWriter object
     and has access to a config object should use this function.
     """
-    tw = TerminalWriter(*args, **kwargs)
+    tw = TerminalWriter(file=file)
     if config.option.color == "yes":
         tw.hasmarkup = True
     if config.option.color == "no":
@@ -1344,8 +1394,8 @@ def create_terminal_writer(config: Config, *args, **kwargs) -> TerminalWriter:
     return tw
 
 
-def _strtobool(val):
-    """Convert a string representation of truth to true (1) or false (0).
+def _strtobool(val: str) -> bool:
+    """Convert a string representation of truth to True or False.
 
     True values are 'y', 'yes', 't', 'true', 'on', and '1'; false values
     are 'n', 'no', 'f', 'false', 'off', and '0'.  Raises ValueError if
@@ -1355,8 +1405,8 @@ def _strtobool(val):
     """
     val = val.lower()
     if val in ("y", "yes", "t", "true", "on", "1"):
-        return 1
+        return True
     elif val in ("n", "no", "f", "false", "off", "0"):
-        return 0
+        return False
     else:
         raise ValueError("invalid truth value {!r}".format(val))
diff --git a/src/_pytest/helpconfig.py b/src/_pytest/helpconfig.py
index 06e0954cf..24952852b 100644
--- a/src/_pytest/helpconfig.py
+++ b/src/_pytest/helpconfig.py
@@ -96,7 +96,7 @@ def pytest_addoption(parser: Parser) -> None:
 @pytest.hookimpl(hookwrapper=True)
 def pytest_cmdline_parse():
     outcome = yield
-    config = outcome.get_result()
+    config = outcome.get_result()  # type: Config
     if config.option.debug:
         path = os.path.abspath("pytestdebug.log")
         debugfile = open(path, "w")
@@ -124,7 +124,7 @@ def pytest_cmdline_parse():
         config.add_cleanup(unset_tracing)
 
 
-def showversion(config):
+def showversion(config: Config) -> None:
     if config.option.version > 1:
         sys.stderr.write(
             "This is pytest version {}, imported from {}\n".format(
@@ -224,7 +224,7 @@ def showhelp(config: Config) -> None:
 conftest_options = [("pytest_plugins", "list of plugin names to load")]
 
 
-def getpluginversioninfo(config):
+def getpluginversioninfo(config: Config) -> List[str]:
     lines = []
     plugininfo = config.pluginmanager.list_plugin_distinfo()
     if plugininfo:
diff --git a/src/_pytest/hookspec.py b/src/_pytest/hookspec.py
index eba6f5ba9..c05b60791 100644
--- a/src/_pytest/hookspec.py
+++ b/src/_pytest/hookspec.py
@@ -143,7 +143,7 @@ def pytest_configure(config: "Config") -> None:
 @hookspec(firstresult=True)
 def pytest_cmdline_parse(
     pluginmanager: "PytestPluginManager", args: List[str]
-) -> Optional[object]:
+) -> Optional["Config"]:
     """return initialized config object, parsing the specified args.
 
     Stops at first non-None result, see :ref:`firstresult`
diff --git a/src/_pytest/logging.py b/src/_pytest/logging.py
index a06dc1ab5..57aa14f27 100644
--- a/src/_pytest/logging.py
+++ b/src/_pytest/logging.py
@@ -141,9 +141,14 @@ class PercentStyleMultiline(logging.PercentStyle):
 
         if auto_indent_option is None:
             return 0
-        elif type(auto_indent_option) is int:
+        elif isinstance(auto_indent_option, bool):
+            if auto_indent_option:
+                return -1
+            else:
+                return 0
+        elif isinstance(auto_indent_option, int):
             return int(auto_indent_option)
-        elif type(auto_indent_option) is str:
+        elif isinstance(auto_indent_option, str):
             try:
                 return int(auto_indent_option)
             except ValueError:
@@ -153,9 +158,6 @@ class PercentStyleMultiline(logging.PercentStyle):
                     return -1
             except ValueError:
                 return 0
-        elif type(auto_indent_option) is bool:
-            if auto_indent_option:
-                return -1
 
         return 0
 
diff --git a/src/_pytest/pathlib.py b/src/_pytest/pathlib.py
index 66ae9a51d..dd7443f07 100644
--- a/src/_pytest/pathlib.py
+++ b/src/_pytest/pathlib.py
@@ -466,7 +466,7 @@ def import_path(
     """
     mode = ImportMode(mode)
 
-    path = Path(p)
+    path = Path(str(p))
 
     if not path.exists():
         raise ImportError(path)
diff --git a/src/_pytest/pytester.py b/src/_pytest/pytester.py
index cf3dbd201..fd4c10577 100644
--- a/src/_pytest/pytester.py
+++ b/src/_pytest/pytester.py
@@ -1054,7 +1054,7 @@ class Testdir:
             args.append("--basetemp=%s" % self.tmpdir.dirpath("basetemp"))
         return args
 
-    def parseconfig(self, *args: Union[str, py.path.local]) -> Config:
+    def parseconfig(self, *args) -> Config:
         """Return a new pytest Config instance from given commandline args.
 
         This invokes the pytest bootstrapping code in _pytest.config to create
@@ -1070,14 +1070,14 @@ class Testdir:
 
         import _pytest.config
 
-        config = _pytest.config._prepareconfig(args, self.plugins)  # type: Config
+        config = _pytest.config._prepareconfig(args, self.plugins)  # type: ignore[arg-type]
         # we don't know what the test will do with this half-setup config
         # object and thus we make sure it gets unconfigured properly in any
         # case (otherwise capturing could still be active, for example)
         self.request.addfinalizer(config._ensure_unconfigure)
         return config
 
-    def parseconfigure(self, *args):
+    def parseconfigure(self, *args) -> Config:
         """Return a new pytest configured Config instance.
 
         This returns a new :py:class:`_pytest.config.Config` instance like
@@ -1318,7 +1318,7 @@ class Testdir:
         Returns a :py:class:`RunResult`.
         """
         __tracebackhide__ = True
-        p = make_numbered_dir(root=Path(self.tmpdir), prefix="runpytest-")
+        p = make_numbered_dir(root=Path(str(self.tmpdir)), prefix="runpytest-")
         args = ("--basetemp=%s" % p,) + args
         plugins = [x for x in self.plugins if isinstance(x, str)]
         if plugins:
diff --git a/src/_pytest/tmpdir.py b/src/_pytest/tmpdir.py
index 199c7c937..f6d1799ad 100644
--- a/src/_pytest/tmpdir.py
+++ b/src/_pytest/tmpdir.py
@@ -13,6 +13,7 @@ from .pathlib import LOCK_TIMEOUT
 from .pathlib import make_numbered_dir
 from .pathlib import make_numbered_dir_with_cleanup
 from .pathlib import Path
+from _pytest.config import Config
 from _pytest.fixtures import FixtureRequest
 from _pytest.monkeypatch import MonkeyPatch
 
@@ -135,7 +136,7 @@ def get_user() -> Optional[str]:
         return None
 
 
-def pytest_configure(config) -> None:
+def pytest_configure(config: Config) -> None:
     """Create a TempdirFactory and attach it to the config object.
 
     This is to comply with existing plugins which expect the handler to be
diff --git a/testing/acceptance_test.py b/testing/acceptance_test.py
index d8f7a501a..66c2bf0bf 100644
--- a/testing/acceptance_test.py
+++ b/testing/acceptance_test.py
@@ -585,11 +585,11 @@ class TestInvocationVariants:
         # Type ignored because `py.test` is not and will not be typed.
         assert pytest.main == py.test.cmdline.main  # type: ignore[attr-defined]
 
-    def test_invoke_with_invalid_type(self):
+    def test_invoke_with_invalid_type(self) -> None:
         with pytest.raises(
             TypeError, match="expected to be a list of strings, got: '-h'"
         ):
-            pytest.main("-h")
+            pytest.main("-h")  # type: ignore[arg-type]
 
     def test_invoke_with_path(self, tmpdir, capsys):
         retcode = pytest.main(tmpdir)
diff --git a/testing/code/test_excinfo.py b/testing/code/test_excinfo.py
index 0ff00bcaa..75c937612 100644
--- a/testing/code/test_excinfo.py
+++ b/testing/code/test_excinfo.py
@@ -372,7 +372,7 @@ def test_excinfo_no_python_sourcecode(tmpdir):
     for item in excinfo.traceback:
         print(item)  # XXX: for some reason jinja.Template.render is printed in full
         item.source  # shouldn't fail
-        if item.path.basename == "test.txt":
+        if isinstance(item.path, py.path.local) and item.path.basename == "test.txt":
             assert str(item.source) == "{{ h()}}:"
 
 
diff --git a/testing/test_config.py b/testing/test_config.py
index 4e64a6928..bc0da93a5 100644
--- a/testing/test_config.py
+++ b/testing/test_config.py
@@ -11,6 +11,7 @@ import py.path
 import _pytest._code
 import pytest
 from _pytest.compat import importlib_metadata
+from _pytest.config import _get_plugin_specs_as_list
 from _pytest.config import _iter_rewritable_modules
 from _pytest.config import Config
 from _pytest.config import ConftestImportFailure
@@ -1115,21 +1116,17 @@ def test_load_initial_conftest_last_ordering(_config_for_test):
     assert [x.function.__module__ for x in values] == expected
 
 
-def test_get_plugin_specs_as_list():
-    from _pytest.config import _get_plugin_specs_as_list
-
-    def exp_match(val):
+def test_get_plugin_specs_as_list() -> None:
+    def exp_match(val: object) -> str:
         return (
-            "Plugin specs must be a ','-separated string"
-            " or a list/tuple of strings for plugin names. Given: {}".format(
-                re.escape(repr(val))
-            )
+            "Plugins may be specified as a sequence or a ','-separated string of plugin names. Got: %s"
+            % re.escape(repr(val))
         )
 
     with pytest.raises(pytest.UsageError, match=exp_match({"foo"})):
-        _get_plugin_specs_as_list({"foo"})
+        _get_plugin_specs_as_list({"foo"})  # type: ignore[arg-type]
     with pytest.raises(pytest.UsageError, match=exp_match({})):
-        _get_plugin_specs_as_list(dict())
+        _get_plugin_specs_as_list(dict())  # type: ignore[arg-type]
 
     assert _get_plugin_specs_as_list(None) == []
     assert _get_plugin_specs_as_list("") == []
@@ -1778,5 +1775,7 @@ def test_conftest_import_error_repr(tmpdir):
     ):
         try:
             raise RuntimeError("some error")
-        except Exception as e:
-            raise ConftestImportFailure(path, sys.exc_info()) from e
+        except Exception as exc:
+            assert exc.__traceback__ is not None
+            exc_info = (type(exc), exc, exc.__traceback__)
+            raise ConftestImportFailure(path, exc_info) from exc