Sep 29, 2025 · Sep 29, 2025 · Sep 29, 2025
diff --git a/mypyc/irbuild/builder.py b/mypyc/irbuild/builder.py
        assert False, "Unsupported lvalue: %r" % lvalue

    def read(
        self, target: Value | AssignmentTarget, line: int = -1, can_borrow: bool = False
        self,
        target: Value | AssignmentTarget,
        line: int = -1,
        *,
        can_borrow: bool = False,
        allow_error_value: bool = False,
    ) -> Value:
        if isinstance(target, Value):
            return target
        if isinstance(target, AssignmentTargetAttr):
            if isinstance(target.obj.type, RInstance) and target.obj.type.class_ir.is_ext_class:
                borrow = can_borrow and target.can_borrow
                return self.add(GetAttr(target.obj, target.attr, line, borrow=borrow))
                return self.add(
                    GetAttr(
                        target.obj,
                        target.attr,
                        line,
                        borrow=borrow,
                        allow_error_value=allow_error_value,
                    )
                )
            else:
                return self.py_get_attr(target.obj, target.attr, line)

diff --git a/mypyc/irbuild/statement.py b/mypyc/irbuild/statement.py
    # Check if we have a return value
    if ret_reg:
        return_block, check_old_exc = BasicBlock(), BasicBlock()
        builder.add(Branch(builder.read(ret_reg), check_old_exc, return_block, Branch.IS_ERROR))
        builder.add(
            Branch(
                builder.read(ret_reg, allow_error_value=True),
                check_old_exc,
                return_block,
                Branch.IS_ERROR,
            )
        )

        builder.activate_block(return_block)
        builder.nonlocal_control[-1].gen_return(builder, builder.read(ret_reg), -1)
diff --git a/mypyc/test-data/fixtures/testutil.py b/mypyc/test-data/fixtures/testutil.py
 def assertRaises(typ: type, msg: str = '') -> Iterator[None]:
    try:
        yield
    exceptException as e:
    exceptBaseException as e:
        assert type(e) is typ, f"{e!r} is not a {typ.__name__}"
        assert msg in str(e), f'Message "{e}" does not match "{msg}"'
    else:
diff --git a/mypyc/test-data/run-async.test b/mypyc/test-data/run-async.test

 [file asyncio/__init__.pyi]
 def run(x: object) -> object: ...

 [case testRunAsyncCancelFinallySpecialCase]
 import asyncio

 from testutil import assertRaises

 # Greatly simplified from asyncio.Condition
 class Condition:
    async def acquire(self) -> None: pass

    async def wait(self) -> bool:
         l = asyncio.get_running_loop()
         fut = l.create_future()
         a = []
         try:
             try:
                 a.append(fut)
                 try:
                     await fut
                     return True
                 finally:
                     a.pop()
             finally:
                err = None
                while True:
                    try:
                        await self.acquire()
                        break
                    except asyncio.CancelledError as e:
                        err = e

                if err is not None:
                    try:
                        raise err
                    finally:
                        err = None
         except BaseException:
             raise

 async def do_cancel() -> None:
    cond = Condition()
    wait = asyncio.create_task(cond.wait())
    asyncio.get_running_loop().call_soon(wait.cancel)
    with assertRaises(asyncio.CancelledError):
        await wait

 def test_cancel_special_case() -> None:
    asyncio.run(do_cancel())

 [file asyncio/__init__.pyi]
 from typing import Any

 class CancelledError(Exception): ...

 def run(x: object) -> object: ...
 def get_running_loop() -> Any: ...
 def create_task(x: object) -> Any: ...
Original file line number	Diff line number	Diff line change
Expand Up		@@ -700,7 +700,12 @@ def get_assignment_target(
		assert False, "Unsupported lvalue: %r" % lvalue

		def read(
		self, target: Value \| AssignmentTarget, line: int = -1, can_borrow: bool = False
		self,
		target: Value \| AssignmentTarget,
		line: int = -1,
		*,
		can_borrow: bool = False,
		allow_error_value: bool = False,
		) -> Value:
		if isinstance(target, Value):
		return target
Expand All		@@ -716,7 +721,15 @@ def read(
		if isinstance(target, AssignmentTargetAttr):
		if isinstance(target.obj.type, RInstance) and target.obj.type.class_ir.is_ext_class:
		borrow = can_borrow and target.can_borrow
		return self.add(GetAttr(target.obj, target.attr, line, borrow=borrow))
		return self.add(
		GetAttr(
		target.obj,
		target.attr,
		line,
		borrow=borrow,
		allow_error_value=allow_error_value,
		)
		)
		else:
		return self.py_get_attr(target.obj, target.attr, line)

Expand Down
Original file line number	Diff line number	Diff line change
Expand Up		@@ -829,7 +829,14 @@ def transform_try_finally_stmt_async(
		# Check if we have a return value
		if ret_reg:
		return_block, check_old_exc = BasicBlock(), BasicBlock()
		builder.add(Branch(builder.read(ret_reg), check_old_exc, return_block, Branch.IS_ERROR))
		builder.add(
		Branch(
		builder.read(ret_reg, allow_error_value=True),
		check_old_exc,
		return_block,
		Branch.IS_ERROR,
		)
		)

		builder.activate_block(return_block)
		builder.nonlocal_control[-1].gen_return(builder, builder.read(ret_reg), -1)
Expand Down
Original file line number	Diff line number	Diff line change
Expand Up		@@ -44,7 +44,7 @@
		def assertRaises(typ: type, msg: str = '') -> Iterator[None]:
		try:
		yield
		exceptException as e:
		exceptBaseException as e:
		assert type(e) is typ, f"{e!r} is not a {typ.__name__}"
		assert msg in str(e), f'Message "{e}" does not match "{msg}"'
		else:
Expand Down
Original file line number	Diff line number	Diff line change
Expand Up		@@ -1234,3 +1234,60 @@ def test_callable_arg_same_name_as_helper() -> None:

		[file asyncio/__init__.pyi]
		def run(x: object) -> object: ...

		[case testRunAsyncCancelFinallySpecialCase]
		import asyncio

		from testutil import assertRaises

		# Greatly simplified from asyncio.Condition
		class Condition:
		async def acquire(self) -> None: pass

		async def wait(self) -> bool:
		l = asyncio.get_running_loop()
		fut = l.create_future()
		a = []
		try:
		try:
		a.append(fut)
		try:
		await fut
		return True
		finally:
		a.pop()
		finally:
		err = None
		while True:
		try:
		await self.acquire()
		break
		except asyncio.CancelledError as e:
		err = e

		if err is not None:
		try:
		raise err
		finally:
		err = None
		except BaseException:
		raise

		async def do_cancel() -> None:
		cond = Condition()
		wait = asyncio.create_task(cond.wait())
		asyncio.get_running_loop().call_soon(wait.cancel)
		with assertRaises(asyncio.CancelledError):
		await wait

		def test_cancel_special_case() -> None:
		asyncio.run(do_cancel())

		[file asyncio/__init__.pyi]
		from typing import Any

		class CancelledError(Exception): ...

		def run(x: object) -> object: ...
		def get_running_loop() -> Any: ...
		def create_task(x: object) -> Any: ...