Fix `.receive()` re-assignment, drop `.clone()`

tractor/_streaming.py

@@ -51,10 +51,13 @@ class ReceiveMsgStream(trio.abc.ReceiveChannel):
         self,
         ctx: 'Context',  # typing: ignore # noqa
         rx_chan: trio.MemoryReceiveChannel,
+        shield: bool = False,
+        _broadcaster: Optional[BroadcastReceiver] = None,
+
     ) -> None:
         self._ctx = ctx
         self._rx_chan = rx_chan
-        self._broadcaster: Optional[BroadcastReceiver] = None
+        self._broadcaster = _broadcaster
 
         # flag to denote end of stream
         self._eoc: bool = False
@@ -234,16 +237,6 @@ class ReceiveMsgStream(trio.abc.ReceiveChannel):
         # still need to consume msgs that are "in transit" from the far
         # end (eg. for ``Context.result()``).
 
-    def clone(self):
-        """Clone this receive channel allowing for multi-task
-        consumption from the same channel.
-
-        """
-        return type(self)(
-            self._ctx,
-            self._rx_chan.clone(),
-        )
-
     @asynccontextmanager
     async def subscribe(
         self,
@@ -266,9 +259,12 @@ class ReceiveMsgStream(trio.abc.ReceiveChannel):
         # allocated ``BroadcastReceiver`` before calling this method for
         # the first time.
         if self._broadcaster is None:
-            self._broadcaster = broadcast_receiver(
+
+            bcast = self._broadcaster = broadcast_receiver(
                 self,
+                # use memory channel size by default
                 self._rx_chan._state.max_buffer_size,  # type: ignore
+               receive_afunc=self.receive,
             )
 
             # NOTE: we override the original stream instance's receive
@@ -276,15 +272,11 @@ class ReceiveMsgStream(trio.abc.ReceiveChannel):
             # such that new subscribers will be copied received values
             # and this stream doesn't have to expect it's original
             # consumer(s) to get a new broadcast rx handle.
-            self.receive = self._broadcaster.receive  # type: ignore
+            self.receive = bcast.receive  # type: ignore
             # seems there's no graceful way to type this with ``mypy``?
             # https://github.com/python/mypy/issues/708
 
         async with self._broadcaster.subscribe() as bstream:
-            # a ``MsgStream`` clone is allocated for the
-            # broadcaster to track this entry's subscription
-            stream_clone = bstream._rx
-            assert stream_clone is not self
             yield bstream