diff --git a/a_sync/_bound.py b/a_sync/_bound.py
index 0f908e1c..51b44ddb 100644
--- a/a_sync/_bound.py
+++ b/a_sync/_bound.py
@@ -63,7 +63,7 @@ def __init__(self, coro: Awaitable[T], property: Union[AsyncPropertyDescriptor[T
         self._property = property
     def __repr__(self) -> str:
         return f"<_PropertyGetter for {self._property}._get at {hex(id(self))}>"
-    def __await__(self) -> T:
+    def __await__(self) -> Generator[Any, None, T]:
         return self._coro.__await__()
 
 @overload
diff --git a/a_sync/_typing.py b/a_sync/_typing.py
index 61975886..b7846fbf 100644
--- a/a_sync/_typing.py
+++ b/a_sync/_typing.py
@@ -3,9 +3,10 @@
 from concurrent.futures._base import Executor
 from decimal import Decimal
 from typing import (TYPE_CHECKING, Any, AsyncIterable, AsyncIterator, Awaitable, 
-                    Callable, DefaultDict, Dict, Generic, Iterable, Iterator, 
-                    List, Literal, Optional, Set, Tuple, Type, TypedDict, TypeVar, 
-                    Union, final, overload)
+                    Callable, DefaultDict, Deque, Dict, Generator, Generic,
+                    ItemsView, Iterable, Iterator, KeysView, List, Literal,
+                    Optional, Protocol, Set, Tuple, Type, TypedDict, TypeVar,
+                    Union, ValuesView, final, overload)
 
 from typing_extensions import Concatenate, ParamSpec, Self, Unpack
 
@@ -17,6 +18,8 @@
 V = TypeVar("V")
 P = ParamSpec("P")
 
+Numeric = Union[int, float, Decimal]
+
 MaybeAwaitable = Union[Awaitable[T], T]
 
 Property = Callable[["ASyncABC"], T]
@@ -45,7 +48,7 @@ class ModifierKwargs(TypedDict, total=False):
     cache_type: CacheType
     cache_typed: bool
     ram_cache_maxsize: Optional[int]
-    ram_cache_ttl: Optional[int]
+    ram_cache_ttl: Optional[Numeric]
     runs_per_minute: Optional[int]
     semaphore: SemaphoreSpec
     # sync modifiers
diff --git a/a_sync/abstract.py b/a_sync/abstract.py
index 3f2e3c66..c7566df7 100644
--- a/a_sync/abstract.py
+++ b/a_sync/abstract.py
@@ -68,6 +68,6 @@ def __a_sync_flag_name__(self) -> str:
     def __a_sync_flag_value__(self) -> bool:
         pass
     
-    @abc.abstractclassmethod  # type: ignore [misc]
+    @abc.abstractclassmethod  # type: ignore [arg-type, misc]
     def __a_sync_default_mode__(cls) -> bool:
-        ...
\ No newline at end of file
+        pass
\ No newline at end of file
diff --git a/a_sync/base.py b/a_sync/base.py
index 47636fdd..e3c8c533 100644
--- a/a_sync/base.py
+++ b/a_sync/base.py
@@ -59,7 +59,7 @@ def __a_sync_default_mode__(cls) -> bool:
         return sync
     
     @classmethod
-    def __get_a_sync_flag_name_from_signature(cls) -> Optional[str]:
+    def __get_a_sync_flag_name_from_signature(cls) -> str:
         logger.debug("Searching for flags defined on %s.__init__", cls)
         if cls.__name__ == "ASyncGenericBase":
             logger.debug("There are no flags defined on the base class, this is expected. Skipping.")
@@ -69,7 +69,7 @@ def __get_a_sync_flag_name_from_signature(cls) -> Optional[str]:
         return cls.__parse_flag_name_from_list(parameters)
 
     @classmethod
-    def __get_a_sync_flag_name_from_class_def(cls) -> Optional[str]:
+    def __get_a_sync_flag_name_from_class_def(cls) -> str:
         logger.debug("Searching for flags defined on %s", cls)
         try:
             return cls.__parse_flag_name_from_list(cls.__dict__)
@@ -93,14 +93,14 @@ def __a_sync_flag_default_value_from_signature(cls) -> bool:
         return flag_value
 
     @classmethod
-    def __get_a_sync_flag_value_from_class_def(cls, flag: str) -> Optional[bool]:
+    def __get_a_sync_flag_value_from_class_def(cls, flag: str) -> bool:
         for spec in [cls, *cls.__bases__]:
-            flag_value = spec.__dict__.get(flag)
-            if flag_value is not None:
-                return flag_value
+            if flag in spec.__dict__:
+                return spec.__dict__[flag]
+        raise exceptions.FlagNotDefined(cls, flag)
 
     @classmethod
-    def __parse_flag_name_from_list(cls, items: Dict[str, Any]) -> Optional[str]:
+    def __parse_flag_name_from_list(cls, items: Dict[str, Any]) -> str:
         present_flags = [flag for flag in _flags.VIABLE_FLAGS if flag in items]
         if len(present_flags) == 0:
             logger.debug("There are too many flags defined on %s", cls)
diff --git a/a_sync/exceptions.py b/a_sync/exceptions.py
index 9ad1277a..172f8801 100644
--- a/a_sync/exceptions.py
+++ b/a_sync/exceptions.py
@@ -1,5 +1,5 @@
 
-from typing import Any, Set
+from typing import Any, Optional, Set, Type
 
 
 class ASyncFlagException(ValueError):
@@ -31,7 +31,7 @@ def __init__(self, target, present_flags):
         super().__init__(err)
 
 class InvalidFlag(ASyncFlagException):
-    def __init__(self, flag: str):
+    def __init__(self, flag: Optional[str]):
         err = f"'flag' must be one of: {self.viable_flags}. You passed {flag}."
         err += "\nThis code should not be reached and likely indicates an issue with a custom subclass definition."
         super().__init__(err)
@@ -40,6 +40,9 @@ class InvalidFlagValue(ASyncFlagException):
     def __init__(self, flag: str, flag_value: Any):
         super().__init__(f"'{flag}' should be boolean. You passed {flag_value}.")
 
+class FlagNotDefined(ASyncFlagException):
+    def __init__(self, obj: Type, flag: str):
+        super().__init__(f"{obj} flag {flag} is not defined.")
 
 
 class ImproperFunctionType(ValueError):
diff --git a/a_sync/future.py b/a_sync/future.py
index 35e70595..1225a87e 100644
--- a/a_sync/future.py
+++ b/a_sync/future.py
@@ -23,7 +23,7 @@ def _materialize(meta: "ASyncFuture[T]") -> T:
     except RuntimeError as e:
         raise RuntimeError(f"{meta} result is not set and the event loop is running, you will need to await it first") from e
 
-Numeric = Union[int, float, Decimal, "ASyncFuture[int]", "ASyncFuture[float]", "ASyncFuture[Decimal]"]
+MetaNumeric = Union[Numeric, "ASyncFuture[int]", "ASyncFuture[float]", "ASyncFuture[Decimal]"]
 
 class ASyncFuture(concurrent.futures.Future, Awaitable[T]):
     __slots__ = "__awaitable__", "__dependencies", "__dependants", "__task"
@@ -120,7 +120,7 @@ def __add__(self: "ASyncFuture[Decimal]", other: Awaitable[Decimal]) -> "ASyncFu
     def __add__(self: "ASyncFuture[Decimal]", other: Awaitable[int]) -> "ASyncFuture[Decimal]":...
     @overload
     def __add__(self: "ASyncFuture[int]", other: Awaitable[Decimal]) -> "ASyncFuture[Decimal]":...
-    def __add__(self, other: Numeric) -> "ASyncFuture":
+    def __add__(self, other: MetaNumeric) -> "ASyncFuture":
         return ASyncFuture(self.__add(other), dependencies=self.__list_dependencies(other))
     @overload
     def __sub__(self: "ASyncFuture[int]", other: int) -> "ASyncFuture[int]":...
@@ -150,7 +150,7 @@ def __sub__(self: "ASyncFuture[Decimal]", other: Awaitable[Decimal]) -> "ASyncFu
     def __sub__(self: "ASyncFuture[Decimal]", other: Awaitable[int]) -> "ASyncFuture[Decimal]":...
     @overload
     def __sub__(self: "ASyncFuture[int]", other: Awaitable[Decimal]) -> "ASyncFuture[Decimal]":...
-    def __sub__(self, other: Numeric) -> "ASyncFuture":
+    def __sub__(self, other: MetaNumeric) -> "ASyncFuture":
         return ASyncFuture(self.__sub(other), dependencies=self.__list_dependencies(other))
     def __mul__(self, other) -> "ASyncFuture":
         return ASyncFuture(self.__mul(other), dependencies=self.__list_dependencies(other))
diff --git a/a_sync/modifiers/manager.py b/a_sync/modifiers/manager.py
index 0dd8e3f8..97f9ec3f 100644
--- a/a_sync/modifiers/manager.py
+++ b/a_sync/modifiers/manager.py
@@ -18,7 +18,7 @@ class ModifierManager(Dict[str, Any]):
     # sync modifiers
     executor: Executor
 
-    def __init__(self, **modifiers: ModifierKwargs) -> None:
+    def __init__(self, **modifiers: Unpack[ModifierKwargs]) -> None:
         for key in modifiers.keys():
             if key not in valid_modifiers:
                 raise ValueError(f"'{key}' is not a supported modifier.")
@@ -70,13 +70,13 @@ def sync_modifier_wrap(*args: P.args, **kwargs: P.kwargs) -> T:
         return sync_modifier_wrap
     
     # Dictionary api
-    def items(self) -> List[Tuple[str, Any]]:
+    def items(self) -> ItemsView[str, Any]:
         return self._modifiers.items()
-    def keys(self) -> List[str]:
+    def keys(self) -> KeysView[str]:
         return self._modifiers.keys()
-    def values(self) -> List[Any]:
+    def values(self) -> ValuesView[Any]:
         return self._modifiers.values()
-    def __contains__(self, key: str) -> bool:
+    def __contains__(self, key: str) -> bool:  # type: ignore [override]
         return key in self._modifiers
     def __iter__(self) -> Iterator[str]:
         return self._modifiers.__iter__()
diff --git a/a_sync/primitives/executor.py b/a_sync/primitives/executor.py
index c6c1c32f..daaa2f9f 100644
--- a/a_sync/primitives/executor.py
+++ b/a_sync/primitives/executor.py
@@ -20,6 +20,8 @@
 
 TEN_MINUTES = 60 * 10
 
+Initializer = Callable[..., object]
+
 class _AsyncExecutorMixin(cf.Executor, _DebugDaemonMixin):
     _max_workers: int
     _workers: str
@@ -31,7 +33,7 @@ async def run(self, fn: Callable[P, T], *args: P.args, **kwargs: P.kwargs) -> T:
         Oh, and you can also use kwargs!
         """
         return fn(*args, **kwargs) if self.sync_mode else await self.submit(fn, *args, **kwargs)
-    def submit(self, fn: Callable[P, T], *args: P.args, **kwargs: P.kwargs) -> "asyncio.Future[T]":
+    def submit(self, fn: Callable[P, T], *args: P.args, **kwargs: P.kwargs) -> "asyncio.Future[T]":  # type: ignore [override]
         """Submits a job to the executor and returns an `asyncio.Future` that can be awaited for the result without blocking."""
         if self.sync_mode:
             fut = asyncio.ensure_future(self._exec_sync(fn, *args, **kwargs))
@@ -49,7 +51,7 @@ def sync_mode(self) -> bool:
         return self._max_workers == 0
     @property
     def worker_count_current(self) -> int:
-        len(getattr(self, f"_{self._workers}"))
+        return len(getattr(self, f"_{self._workers}"))
     async def _exec_sync(self, fn: Callable[P, T], *args: P.args, **kwargs: P.kwargs) -> T:
         """Just wraps a fn and its args into an awaitable."""
         return fn(*args, **kwargs)
@@ -68,7 +70,7 @@ def __init__(
         self, 
         max_workers: Optional[int] = None, 
         mp_context: Optional[multiprocessing.context.BaseContext] = None, 
-        initializer: Callable[..., object] = None,
+        initializer: Optional[Initializer] = None,
         initargs: Tuple[Any, ...] = (),
     ) -> None:
         if max_workers == 0:
@@ -85,7 +87,7 @@ def __init__(
         self, 
         max_workers: Optional[int] = None, 
         thread_name_prefix: str = '', 
-        initializer: Callable[..., object] = None,
+        initializer: Optional[Initializer] = None,
         initargs: Tuple[Any, ...] = (),
     ) -> None:
         if max_workers == 0:
diff --git a/a_sync/primitives/locks/event.py b/a_sync/primitives/locks/event.py
index 01b74719..557b4f9a 100644
--- a/a_sync/primitives/locks/event.py
+++ b/a_sync/primitives/locks/event.py
@@ -1,13 +1,17 @@
 
-import asyncio, sys
-from functools import cached_property
-from typing import Optional
+import asyncio
+import sys
 
+from a_sync._typing import *
 from a_sync.primitives._debug import _DebugDaemonMixin
 
 
 class Event(asyncio.Event, _DebugDaemonMixin):
     """asyncio.Event but with some additional debug logging to help detect deadlocks."""
+    _value: bool
+    _loop: asyncio.AbstractEventLoop
+    _waiters: Deque["asyncio.Future[None]"]
+    
     def __init__(self, name: str = "", debug_daemon_interval: int = 300, *, loop: Optional[asyncio.AbstractEventLoop] = None):
         if sys.version_info >= (3, 10):
             super().__init__()
@@ -22,7 +26,7 @@ def __repr__(self) -> str:
         if self._waiters:
             status += f', waiters:{len(self._waiters)}'
         return f"<{self.__class__.__module__}.{self.__class__.__name__} {label} at {hex(id(self))} [{status}]>"
-    async def wait(self) -> bool:
+    async def wait(self) -> Literal[True]:
         if self.is_set():
             return True
         self._ensure_debug_daemon()
diff --git a/a_sync/primitives/locks/prio_semaphore.py b/a_sync/primitives/locks/prio_semaphore.py
index cb0f5626..b9fdbfa2 100644
--- a/a_sync/primitives/locks/prio_semaphore.py
+++ b/a_sync/primitives/locks/prio_semaphore.py
@@ -4,14 +4,12 @@
 import logging
 from collections import deque
 from functools import cached_property
-from typing import (Deque, Dict, Generic, List, Literal, Optional, Protocol,
-                    Type, TypeVar)
 
+from a_sync._typing import *
 from a_sync.primitives.locks.semaphore import Semaphore
 
 logger = logging.getLogger(__name__)
 
-T = TypeVar('T', covariant=True)
 
 class Priority(Protocol):
     def __lt__(self, other) -> bool:
@@ -41,7 +39,7 @@ def __init__(self, value: int = 1, *, name: Optional[str] = None) -> None:
         super().__init__(value, name=name)
         self._waiters = []
         # NOTE: This should (hopefully) be temporary
-        self._potential_lost_waiters = []
+        self._potential_lost_waiters: List["asyncio.Future[None]"] = []
 
     def __repr__(self) -> str:
         return f"<{self.__class__.__name__} name={self.name} capacity={self._capacity} value={self._value} waiters={self._count_waiters()}>"
@@ -188,10 +186,10 @@ async def acquire(self) -> Literal[True]:
     def release(self) -> None:
         self._parent.release()
     
-class _PrioritySemaphoreContextManager(_AbstractPrioritySemaphoreContextManager[int]):
+class _PrioritySemaphoreContextManager(_AbstractPrioritySemaphoreContextManager[Numeric]):
     _priority_name = "priority"
 
-class PrioritySemaphore(_AbstractPrioritySemaphore[int, _PrioritySemaphoreContextManager]):  # type: ignore [type-var]
+class PrioritySemaphore(_AbstractPrioritySemaphore[Numeric, _PrioritySemaphoreContextManager]):  # type: ignore [type-var]
     _context_manager_class = _PrioritySemaphoreContextManager
     _top_priority = -1
     """
diff --git a/a_sync/primitives/locks/semaphore.py b/a_sync/primitives/locks/semaphore.py
index 3a3cca76..f22ea4fb 100644
--- a/a_sync/primitives/locks/semaphore.py
+++ b/a_sync/primitives/locks/semaphore.py
@@ -16,7 +16,7 @@ def __init__(self, value: int, name=None, **kwargs) -> None:
         """
         super().__init__(value, **kwargs)
         self.name = name or self.__origin__ if hasattr(self, '__origin__') else None
-        self._decorated = set()
+        self._decorated: Set[str] = set()
     
     # Dank new functionality
     def __call__(self, fn: Callable[P, T]) -> Callable[P, T]:
@@ -31,7 +31,7 @@ def __repr__(self) -> str:
     def __len__(self) -> int:
         return len(self._waiters) if self._waiters else 0
     
-    def decorate(self, fn: Callable[P, T]) -> Callable[P, T]:
+    def decorate(self, fn: CoroFn[P, T]) -> CoroFn[P, T]:
         if not asyncio.iscoroutinefunction(fn):
             raise TypeError(f"{fn} must be a coroutine function")
         @functools.wraps(fn)
@@ -41,7 +41,7 @@ async def semaphore_wrapper(*args: P.args, **kwargs: P.kwargs) -> T:
         self._decorated.add(f"{fn.__module__}.{fn.__name__}")
         return semaphore_wrapper
     
-    async def acquire(self) -> bool:
+    async def acquire(self) -> Literal[True]:
         if self._value <= 0:
             self._ensure_debug_daemon()
         return await super().acquire()
diff --git a/a_sync/task.py b/a_sync/task.py
index 502c1fce..90f283f9 100644
--- a/a_sync/task.py
+++ b/a_sync/task.py
@@ -19,7 +19,7 @@ def create_task(coro: Awaitable[T], *, name: Optional[str] = None, skip_gc_until
         __persist(task)
     return task
 
-class TaskMapping(DefaultDict[K, "asyncio.Task[_V]"]):
+class TaskMapping(DefaultDict[K, "asyncio.Task[V]"]):
     def __init__(self, coro_fn: Callable[Concatenate[K, P], Awaitable[V]] = None, *, name: str = '', **coro_fn_kwargs: P.kwargs) -> None:
         self._coro_fn = coro_fn
         self._coro_fn_kwargs = coro_fn_kwargs
@@ -38,7 +38,7 @@ def __getitem__(self, item: K) -> "asyncio.Task[V]":
             return task
     async def map(self, *iterables: AnyIterable[K], pop: bool = True, yields: Literal['keys', 'both'] = 'both') -> AsyncIterator[Tuple[K, V]]:
         assert not self, "must be empty"
-        async for key in as_yielded(*[__yield_keys(iterable) for iterable in iterables]):
+        async for key in as_yielded(*[__yield_keys(iterable) for iterable in iterables]):  # type: ignore [attr-defined]
             self[key]  # ensure task is running
             async for key, value in self.yield_completed(pop=pop):
                 yield __yield(key, value, yields)
@@ -47,7 +47,9 @@ async def map(self, *iterables: AnyIterable[K], pop: bool = True, yields: Litera
     async def yield_completed(self, pop: bool = True) -> AsyncIterator[Tuple[K, V]]:
         for k, task in dict(self).items():
             if task.done():
-                yield k, await self.pop(k) if pop else task
+                if pop:
+                    task = self.pop(k)
+                yield k, await task
 
 
 __persisted_tasks: Set["asyncio.Task[Any]"] = set()
diff --git a/a_sync/utils/iterators.py b/a_sync/utils/iterators.py
index a94abeb0..778f9148 100644
--- a/a_sync/utils/iterators.py
+++ b/a_sync/utils/iterators.py
@@ -1,7 +1,7 @@
 
 import asyncio
 import logging
-from asyncio.futures import _chain_future
+from asyncio.futures import _chain_future  # type: ignore [attr-defined]
 from typing import AsyncIterator, Optional, TypeVar, Union, overload
 
 from a_sync.primitives.queue import Queue
@@ -58,8 +58,8 @@ async def as_yielded(*iterators: AsyncIterator[T]) -> AsyncIterator[T]:  # type:
     queue = Queue()
     task = asyncio.create_task(exhaust_iterators(iterators, queue=queue))
     def done_callback(t: asyncio.Task) -> None:
-        if t.exception() and not next_fut.done(): 
-            next_fut.set_exception(t.exception())
+        if (e := t.exception()) and not next_fut.done(): 
+            next_fut.set_exception(e)
         
     task.add_done_callback(done_callback)
     while not task.done():
diff --git a/a_sync/utils/map.py b/a_sync/utils/map.py
index e13e1f00..0e7e613b 100644
--- a/a_sync/utils/map.py
+++ b/a_sync/utils/map.py
@@ -1,6 +1,4 @@
 
-from typing import Awaitable, Callable, Literal, Tuple, Union, overload
-
 from a_sync._typing import *
 from a_sync.iter import ASyncIterator