Refactor source/destination code of signal and operation

b_asic/signal.py

@@ -33,6 +33,10 @@ class Signal(AbstractGraphComponent):
     name : Name, default: ""
         The signal name.
 
+    .. note:: If a Signal is provided as *source* or *destination*, the
+              connected port is used. Hence, if the argument signal is later
+              changed, it will not affect the current Signal.
+
     See also
     ========
     set_source, set_destination
@@ -43,8 +47,10 @@ class Signal(AbstractGraphComponent):
 
     def __init__(
         self,
-        source: Optional[Union["OutputPort", "Operation"]] = None,
-        destination: Optional[Union["InputPort", "Operation"]] = None,
+        source: Optional[Union["OutputPort", "Signal", "Operation"]] = None,
+        destination: Optional[
+            Union["InputPort", "Signal", "Operation"]
+        ] = None,
         bits: Optional[int] = None,
         name: Name = Name(""),
     ):