asyncio.timeout(0) and asyncio.timeout(-1) cancellation is delayed

graingert

Bug report

I expect this to raise a TimeoutError:

async def amain():
    async with asyncio.timeout(-11):
        await asyncio.sleep(0)

asyncio.run(amain())

Instead I have to add an extra asyncio.sleep(0) to get a TimeoutError

async def amain():
    async with asyncio.timeout(-11):
        await asyncio.sleep(0)  # does not raise CancelledError
        await asyncio.sleep(0)  # raises CancelledError

asyncio.run(amain())

Your environment

CPython versions tested on:
Operating system and architecture: