# uvloop/loop.pyx ~line 2060
waiter = self._new_future()
tr = TCPTransport.new(self, protocol, None, waiter, context)
try:
    tr._open(sock.fileno())      # libuv takes over the fd
    tr._init_protocol()          # _transports[fd] = tr
    await waiter                 # ← cancellation point
except BaseException:
    tr._close()                  # libuv closes fd, but sock doesn't know
    raise

tr._attach_fileobj(sock)         # only reached on success — calls sock.detach() later via _close()

import asyncio
import socket
import uvloop

async def test(loop):
    srv = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
    srv.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
    srv.bind(("127.0.0.1", 0))
    srv.listen(1)
    addr = srv.getsockname()

    client = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
    client.setblocking(False)
    try:
        client.connect(addr)
    except BlockingIOError:
        pass
    await asyncio.sleep(0.01)

    task = asyncio.ensure_future(loop.create_connection(asyncio.Protocol, sock=client))
    await asyncio.sleep(0)
    task.cancel()
    try:
        await task
    except asyncio.CancelledError:
        pass

    print(f"uvloop:  sock.fileno() = {client.fileno()}")  # NOT -1 → bug
    srv.close()
    try:
        client.close()
    except OSError:
        pass

# uvloop — socket NOT detached
uvloop.install()
loop = asyncio.new_event_loop()
loop.run_until_complete(test(loop))
loop.close()

# standard asyncio — socket properly detached
asyncio.set_event_loop_policy(None)
loop = asyncio.new_event_loop()
loop.run_until_complete(test(loop))
loop.close()

uvloop:  sock.fileno() = 13    ← should be -1
asyncio: sock.fileno() = -1    ← correct

RuntimeError: File descriptor 1768 is used by transport <TCPTransport closed=False reading=True 0x...>

except BaseException:
    tr._close()
    if sock is not None:
        sock.detach()
    raise