diff --git a/argcomplete/_check_console_script.py b/argcomplete/_check_console_script.py
index d2dc46a2..af522509 100644
--- a/argcomplete/_check_console_script.py
+++ b/argcomplete/_check_console_script.py
@@ -17,12 +17,12 @@
 try:
     from importlib.metadata import entry_points as importlib_entry_points
 except ImportError:
-    from importlib_metadata import entry_points as importlib_entry_points  # type:ignore
+    from importlib_metadata import entry_points as importlib_entry_points  # type: ignore[import,no-redef]
 
 from ._check_module import ArgcompleteMarkerNotFound, find
 
 
-def main():
+def main() -> None:
     # Argument is the full path to the console script.
     script_path = sys.argv[1]
 
diff --git a/argcomplete/_check_module.py b/argcomplete/_check_module.py
index 4958f026..7ec4c04c 100644
--- a/argcomplete/_check_module.py
+++ b/argcomplete/_check_module.py
@@ -11,7 +11,7 @@
 import tokenize
 
 try:
-    from importlib.util import find_spec  # type:ignore
+    from importlib.util import find_spec  # type: ignore
 except ImportError:
     import typing as t
     from collections import namedtuple
@@ -19,7 +19,7 @@
 
     ModuleSpec = namedtuple("ModuleSpec", ["origin", "has_location", "submodule_search_locations"])
 
-    def find_spec(  # type:ignore
+    def find_spec(  # type: ignore[misc]
         name: str,
         package: t.Optional[str] = None,
     ) -> t.Optional[ModuleSpec]:
@@ -62,7 +62,7 @@ def find(name, return_package=False):
         return path + ".py"
 
 
-def main():
+def main() -> None:
     try:
         name = sys.argv[1]
     except IndexError:
diff --git a/argcomplete/completers.py b/argcomplete/completers.py
index d89cdbfb..44714137 100644
--- a/argcomplete/completers.py
+++ b/argcomplete/completers.py
@@ -4,9 +4,11 @@
 import argparse
 import os
 import subprocess
+from collections.abc import Iterable
+from typing import Any, Callable, List, Union
 
 
-def _call(*args, **kwargs):
+def _call(*args, **kwargs) -> List[str]:
     # TODO: replace "universal_newlines" with "text" once 3.6 support is dropped
     kwargs["universal_newlines"] = True
     try:
@@ -22,20 +24,20 @@ class BaseCompleter:
 
     def __call__(
         self, *, prefix: str, action: argparse.Action, parser: argparse.ArgumentParser, parsed_args: argparse.Namespace
-    ):
+    ) -> Iterable[str]:
         raise NotImplementedError("This method should be implemented by a subclass.")
 
 
 class ChoicesCompleter(BaseCompleter):
-    def __init__(self, choices):
+    def __init__(self, choices: Iterable[Any]):
         self.choices = choices
 
-    def _convert(self, choice):
+    def _convert(self, choice: Any) -> str:
         if not isinstance(choice, str):
-            choice = str(choice)
+            return str(choice)
         return choice
 
-    def __call__(self, **kwargs):
+    def __call__(self, **kwargs) -> Iterable[str]:
         return (self._convert(c) for c in self.choices)
 
 
@@ -47,15 +49,15 @@ class FilesCompleter(BaseCompleter):
     File completer class, optionally takes a list of allowed extensions
     """
 
-    def __init__(self, allowednames=(), directories=True):
+    def __init__(self, allowednames: Union[str, Iterable[str]] = (), directories: bool = True):
         # Fix if someone passes in a string instead of a list
-        if isinstance(allowednames, (str, bytes)):
+        if isinstance(allowednames, str):
             allowednames = [allowednames]
 
         self.allowednames = [x.lstrip("*").lstrip(".") for x in allowednames]
         self.directories = directories
 
-    def __call__(self, prefix, **kwargs):
+    def __call__(self, *, prefix: str, **kwargs) -> Iterable[str]:
         completion = []
         if self.allowednames:
             if self.directories:
@@ -74,17 +76,16 @@ def __call__(self, prefix, **kwargs):
 
 
 class _FilteredFilesCompleter(BaseCompleter):
-    def __init__(self, predicate):
+    def __init__(self, predicate: Callable[[str], bool]):
         """
         Create the completer
 
         A predicate accepts as its only argument a candidate path and either
         accepts it or rejects it.
         """
-        assert predicate, "Expected a callable predicate"
         self.predicate = predicate
 
-    def __call__(self, prefix, **kwargs):
+    def __call__(self, *, prefix: str, **kwargs) -> Iterable[str]:
         """
         Provide completions on prefix
         """
@@ -105,7 +106,7 @@ def __call__(self, prefix, **kwargs):
 
 
 class DirectoriesCompleter(_FilteredFilesCompleter):
-    def __init__(self):
+    def __init__(self) -> None:
         _FilteredFilesCompleter.__init__(self, predicate=os.path.isdir)
 
 
@@ -114,10 +115,10 @@ class SuppressCompleter(BaseCompleter):
     A completer used to suppress the completion of specific arguments
     """
 
-    def __init__(self):
+    def __init__(self) -> None:
         pass
 
-    def suppress(self):
+    def suppress(self) -> bool:
         """
         Decide if the completion should be suppressed
         """
diff --git a/argcomplete/finders.py b/argcomplete/finders.py
index 77d98910..552b4a9c 100644
--- a/argcomplete/finders.py
+++ b/argcomplete/finders.py
@@ -7,10 +7,10 @@
 import os
 import sys
 from collections.abc import Mapping
-from typing import Callable, Dict, List, Optional, Sequence, Union
+from typing import Any, Callable, Dict, List, Optional, Sequence, Union
 
 from . import io as _io
-from .completers import ChoicesCompleter, FilesCompleter, SuppressCompleter
+from .completers import BaseCompleter, ChoicesCompleter, FilesCompleter, SuppressCompleter
 from .io import debug, mute_stderr
 from .lexers import split_line
 from .packages._argparse import IntrospectiveArgumentParser, action_is_greedy, action_is_open, action_is_satisfied
@@ -26,7 +26,7 @@
 }
 
 
-def default_validator(completion, prefix):
+def default_validator(completion: str, prefix: str) -> bool:
     return completion.startswith(prefix)
 
 
@@ -40,12 +40,12 @@ class CompletionFinder(object):
     def __init__(
         self,
         argument_parser=None,
-        always_complete_options=True,
-        exclude=None,
-        validator=None,
-        print_suppressed=False,
-        default_completer=FilesCompleter(),
-        append_space=None,
+        always_complete_options: Union[bool, str] = True,
+        exclude: Optional[Sequence[str]] = None,
+        validator: Optional[Callable[[str, str], bool]] = None,
+        print_suppressed: bool = False,
+        default_completer: BaseCompleter = FilesCompleter(),
+        append_space: Optional[bool] = None,
     ):
         self._parser = argument_parser
         self.always_complete_options = always_complete_options
@@ -65,14 +65,14 @@ def __call__(
         self,
         argument_parser: argparse.ArgumentParser,
         always_complete_options: Union[bool, str] = True,
-        exit_method: Callable = os._exit,
+        exit_method: Callable[[int], Any] = os._exit,
         output_stream=None,
         exclude: Optional[Sequence[str]] = None,
-        validator: Optional[Callable] = None,
+        validator: Optional[Callable[[str, str], bool]] = None,
         print_suppressed: bool = False,
         append_space: Optional[bool] = None,
-        default_completer=FilesCompleter(),
-    ):
+        default_completer: BaseCompleter = FilesCompleter(),
+    ) -> None:
         """
         :param argument_parser: The argument parser to autocomplete on
         :param always_complete_options:
@@ -103,7 +103,7 @@ def __call__(
         added to argcomplete.safe_actions, if their values are wanted in the ``parsed_args`` completer argument, or
         their execution is otherwise desirable.
         """
-        self.__init__(  # type: ignore
+        self.__init__(  # type: ignore[misc]
             argument_parser,
             always_complete_options=always_complete_options,
             exclude=exclude,
@@ -242,7 +242,7 @@ def patch(parser):
                     continue
 
                 # TODO: accomplish this with super
-                class IntrospectAction(action.__class__):  # type: ignore
+                class IntrospectAction(action.__class__):  # type: ignore[name-defined]
                     def __call__(self, parser, namespace, values, option_string=None):
                         debug("Action stub called on", self)
                         debug("\targs:", parser, namespace, values, option_string)
@@ -400,7 +400,7 @@ def _complete_active_option(self, parser, next_positional, cword_prefix, parsed_
                 else:
                     debug("Completer is not callable, trying the readline completer protocol instead")
                     for i in range(9999):
-                        next_completion = completer.complete(cword_prefix, i)  # type: ignore
+                        next_completion = completer.complete(cword_prefix, i)
                         if next_completion is None:
                             break
                         if self.validator(next_completion, cword_prefix):
diff --git a/argcomplete/io.py b/argcomplete/io.py
index df2c4f20..f3d76b3d 100644
--- a/argcomplete/io.py
+++ b/argcomplete/io.py
@@ -7,7 +7,7 @@
 debug_stream = sys.stderr
 
 
-def debug(*args):
+def debug(*args) -> None:
     if _DEBUG:
         print(file=debug_stream, *args)
 
@@ -33,7 +33,7 @@ def mute_stderr():
         sys.stderr = stderr
 
 
-def warn(*args):
+def warn(*args) -> None:
     """
     Prints **args** to standard error when running completions. This will interrupt the user's command line interaction;
     use it to indicate an error condition that is preventing your completer from working.
diff --git a/argcomplete/lexers.py b/argcomplete/lexers.py
index 72c378b5..8cd5c984 100644
--- a/argcomplete/lexers.py
+++ b/argcomplete/lexers.py
@@ -1,22 +1,25 @@
 import os
+from typing import List, Optional, Tuple
 
 from .exceptions import ArgcompleteException
 from .io import debug
 from .packages import _shlex
 
 
-def split_line(line, point=None):
-    if point is None:
-        point = len(line)
+_SplitResult = Tuple[str, str, str, List[str], Optional[int]]
+
+
+def split_line(line: str, point: Optional[int] = None) -> _SplitResult:
+    point_ = len(line) if point is None else point
     line = line[:point]
     lexer = _shlex.shlex(line, posix=True)
     lexer.whitespace_split = True
     lexer.wordbreaks = os.environ.get("_ARGCOMPLETE_COMP_WORDBREAKS", "")
     words = []
 
-    def split_word(word):
+    def split_word(word: str) -> _SplitResult:
         # TODO: make this less ugly
-        point_in_word = len(word) + point - lexer.instream.tell()
+        point_in_word = len(word) + point_ - lexer.instream.tell()
         if isinstance(lexer.state, (str, bytes)) and lexer.state in lexer.whitespace:
             point_in_word += 1
         if point_in_word > len(word):
diff --git a/argcomplete/shell_integration.py b/argcomplete/shell_integration.py
index 6d1ba245..9ee22d3c 100644
--- a/argcomplete/shell_integration.py
+++ b/argcomplete/shell_integration.py
@@ -4,7 +4,9 @@
 # files with source copies of this package and derivative works is **REQUIRED** as specified by the Apache License.
 # See https://github.com/kislyuk/argcomplete for more info.
 
+from collections.abc import Iterable
 from shlex import quote
+from typing import Optional
 
 bashcode = r"""
 # Run something, muting output or redirecting it to the debug stream
@@ -118,16 +120,22 @@
 shell_codes = {"bash": bashcode, "tcsh": tcshcode, "fish": fishcode, "powershell": powershell_code}
 
 
-def shellcode(executables, use_defaults=True, shell="bash", complete_arguments=None, argcomplete_script=None):
+def shellcode(
+    executables: Iterable[str],
+    use_defaults: bool = True,
+    shell: str = "bash",
+    complete_arguments: Optional[Iterable[str]] = None,
+    argcomplete_script: Optional[str] = None,
+) -> str:
     """
     Provide the shell code required to register a python executable for use with the argcomplete module.
 
-    :param list(str) executables: Executables to be completed (when invoked exactly with this name)
+    :param Iterable(str) executables: Executables to be completed (when invoked exactly with this name)
     :param bool use_defaults: Whether to fallback to readline's default completion when no matches are generated
         (affects bash only)
     :param str shell: Name of the shell to output code for
     :param complete_arguments: Arguments to call complete with (affects bash only)
-    :type complete_arguments: list(str) or None
+    :type complete_arguments: Iterable(str) or None
     :param argcomplete_script: Script to call complete with, if not the executable to complete.
         If supplied, will be used to complete *all* passed executables.
     :type argcomplete_script: str or None