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Merged
merged 2 commits into from
Sep 2, 2025
Merged

Add await to empty context hack #19777

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5adf014
Fix wrong test
sterliakov Sep 1, 2025
75863a4
Specialize to `await call()` only
sterliakov Sep 2, 2025
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7 changes: 6 additions & 1 deletion mypy/checker.py
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Original file line number Diff line number Diff line change
Expand Up @@ -80,6 +80,7 @@
AssertStmt,
AssignmentExpr,
AssignmentStmt,
AwaitExpr,
Block,
BreakStmt,
BytesExpr,
Expand Down Expand Up @@ -4924,7 +4925,11 @@ def check_return_stmt(self, s: ReturnStmt) -> None:
allow_none_func_call = is_lambda or declared_none_return or declared_any_return

# Return with a value.
if isinstance(s.expr, (CallExpr, ListExpr, TupleExpr, DictExpr, SetExpr, OpExpr)):
if (
isinstance(s.expr, (CallExpr, ListExpr, TupleExpr, DictExpr, SetExpr, OpExpr))
or isinstance(s.expr, AwaitExpr)
and isinstance(s.expr.expr, CallExpr)
):
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What about using isinstance(s.expr, AwaitExpr) and isinstance(s.expr.expr, CallExpr)? This will save us some pointless busy-work for cases like return await some_name.

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Hm, yes, makes sense. I doubt that await not_a_call accounts for some significant portion of await expressions, but this shouldn't harm.

# For expressions that (strongly) depend on type context (i.e. those that
# are handled like a function call), we allow fallback to empty type context
# in case of errors, this improves user experience in some cases,
Expand Down
2 changes: 2 additions & 0 deletions test-data/unit/check-inference-context.test
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Expand Up @@ -1582,3 +1582,5 @@ async def inner(c: Cls[T]) -> Optional[T]:

async def outer(c: Cls[T]) -> Optional[T]:
return await inner(c)
[builtins fixtures/async_await.pyi]
[typing fixtures/typing-async.pyi]
45 changes: 26 additions & 19 deletions test-data/unit/fixtures/typing-async.pyi
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Expand Up @@ -28,7 +28,9 @@ Self = 0

T = TypeVar('T')
T_co = TypeVar('T_co', covariant=True)
R_co = TypeVar('R_co', covariant=True)
T_contra = TypeVar('T_contra', contravariant=True)
S_contra = TypeVar('S_contra', contravariant=True)
U = TypeVar('U')
V = TypeVar('V')
S = TypeVar('S')
Expand All @@ -49,9 +51,9 @@ class Iterator(Iterable[T_co], Protocol):
@abstractmethod
def __next__(self) -> T_co: pass

class Generator(Iterator[T], Generic[T, U, V]):
class Generator(Iterator[T_co], Generic[T_co, S_contra, R_co]):
@abstractmethod
def send(self, value: U) -> T: pass
def send(self, value: S_contra) -> T_co: pass

@abstractmethod
def throw(self, typ: Any, val: Any=None, tb: Any=None) -> None: pass
Expand All @@ -60,49 +62,54 @@ class Generator(Iterator[T], Generic[T, U, V]):
def close(self) -> None: pass

@abstractmethod
def __iter__(self) -> 'Generator[T, U, V]': pass
def __iter__(self) -> 'Generator[T_co, S_contra, R_co]': pass

class AsyncGenerator(AsyncIterator[T], Generic[T, U]):
class AsyncGenerator(AsyncIterator[T_co], Generic[T_co, S_contra]):
@abstractmethod
def __anext__(self) -> Awaitable[T]: pass
def __anext__(self) -> Awaitable[T_co]: pass

@abstractmethod
def asend(self, value: U) -> Awaitable[T]: pass
def asend(self, value: S_contra) -> Awaitable[T_co]: pass

@abstractmethod
def athrow(self, typ: Any, val: Any=None, tb: Any=None) -> Awaitable[T]: pass
def athrow(self, typ: Any, val: Any=None, tb: Any=None) -> Awaitable[T_co]: pass

@abstractmethod
def aclose(self) -> Awaitable[T]: pass
def aclose(self) -> Awaitable[T_co]: pass

@abstractmethod
def __aiter__(self) -> 'AsyncGenerator[T, U]': pass
def __aiter__(self) -> 'AsyncGenerator[T_co, S_contra]': pass

class Awaitable(Protocol[T]):
class Awaitable(Protocol[T_co]):
@abstractmethod
def __await__(self) -> Generator[Any, Any, T]: pass
def __await__(self) -> Generator[Any, Any, T_co]: pass

class AwaitableGenerator(Generator[T, U, V], Awaitable[V], Generic[T, U, V, S], metaclass=ABCMeta):
class AwaitableGenerator(
Awaitable[R_co],
Generator[T_co, S_contra, R_co],
Generic[T_co, S_contra, R_co, S],
metaclass=ABCMeta
):
pass

class Coroutine(Awaitable[V], Generic[T, U, V]):
class Coroutine(Awaitable[R_co], Generic[T_co, S_contra, R_co]):
@abstractmethod
def send(self, value: U) -> T: pass
def send(self, value: S_contra) -> T_co: pass

@abstractmethod
def throw(self, typ: Any, val: Any=None, tb: Any=None) -> None: pass

@abstractmethod
def close(self) -> None: pass

class AsyncIterable(Protocol[T]):
class AsyncIterable(Protocol[T_co]):
@abstractmethod
def __aiter__(self) -> 'AsyncIterator[T]': pass
def __aiter__(self) -> 'AsyncIterator[T_co]': pass

class AsyncIterator(AsyncIterable[T], Protocol):
def __aiter__(self) -> 'AsyncIterator[T]': return self
class AsyncIterator(AsyncIterable[T_co], Protocol):
def __aiter__(self) -> 'AsyncIterator[T_co]': return self
@abstractmethod
def __anext__(self) -> Awaitable[T]: pass
def __anext__(self) -> Awaitable[T_co]: pass

class Sequence(Iterable[T_co], Container[T_co]):
@abstractmethod
Expand Down
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