Fix type signature of act_on implementations (#4867)

These are only ever called via reflection, but still the type should be as per this PR. @95-martin-orion

cirq-core/cirq/circuits/circuit_operation.py

@@ -265,7 +265,7 @@ def mapped_op(self, deep: bool = False) -> 'cirq.CircuitOperation':
     def _decompose_(self) -> Iterator['cirq.Operation']:
         return self.mapped_circuit(deep=False).all_operations()
 
-    def _act_on_(self, args: 'cirq.ActOnArgs') -> bool:
+    def _act_on_(self, args: 'cirq.OperationTarget') -> bool:
         for op in self._decompose_():
             protocols.act_on(op, args)
         return True

cirq-core/cirq/ops/classically_controlled_operation.py

@@ -175,7 +175,7 @@ def _json_dict_(self) -> Dict[str, Any]:
             'sub_operation': self._sub_operation,
         }
 
-    def _act_on_(self, args: 'cirq.ActOnArgs') -> bool:
+    def _act_on_(self, args: 'cirq.OperationTarget') -> bool:
         if all(c.resolve(args.log_of_measurement_results) for c in self._conditions):
             protocols.act_on(self._sub_operation, args)
         return True

cirq-core/cirq/ops/gate_operation.py

@@ -260,7 +260,7 @@ def _measurement_key_objs_(self) -> Optional[AbstractSet['cirq.MeasurementKey']]
             return getter()
         return NotImplemented
 
-    def _act_on_(self, args: 'cirq.ActOnArgs'):
+    def _act_on_(self, args: 'cirq.OperationTarget'):
         getter = getattr(self.gate, '_act_on_', None)
         if getter is not None:
             return getter(args, self.qubits)

cirq-core/cirq/ops/identity.py

@@ -61,7 +61,7 @@ def __init__(
         if len(self._qid_shape) != num_qubits:
             raise ValueError('len(qid_shape) != num_qubits')
 
-    def _act_on_(self, args: 'cirq.ActOnArgs', qubits: Sequence['cirq.Qid']):
+    def _act_on_(self, args: 'cirq.OperationTarget', qubits: Sequence['cirq.Qid']):
         return True
 
     def _qid_shape_(self) -> Tuple[int, ...]:

cirq-core/cirq/ops/raw_types.py

@@ -776,7 +776,7 @@ def _is_parameterized_(self) -> bool:
             protocols.is_parameterized(tag) for tag in self.tags
         )
 
-    def _act_on_(self, args: 'cirq.ActOnArgs') -> bool:
+    def _act_on_(self, args: 'cirq.OperationTarget') -> bool:
         sub = getattr(self.sub_operation, "_act_on_", None)
         if sub is not None:
             return sub(args)

cirq-core/cirq/protocols/act_on_protocol.py

@@ -28,7 +28,7 @@ class SupportsActOn(Protocol):
     """An object that explicitly specifies how to act on simulator states."""
 
     @doc_private
-    def _act_on_(self, args: 'cirq.ActOnArgs') -> Union[NotImplementedType, bool]:
+    def _act_on_(self, args: 'cirq.OperationTarget') -> Union[NotImplementedType, bool]:
         """Applies an action to the given argument, if it is a supported type.
 
         For example, unitary operations can implement an `_act_on_` method that
@@ -60,7 +60,7 @@ class SupportsActOnQubits(Protocol):
     @doc_private
     def _act_on_(
         self,
-        args: 'cirq.ActOnArgs',
+        args: 'cirq.OperationTarget',
         qubits: Sequence['cirq.Qid'],
     ) -> Union[NotImplementedType, bool]:
         """Applies an action to the given argument, if it is a supported type.

cirq-core/cirq/testing/consistent_act_on_test.py

@@ -24,7 +24,7 @@ class GoodGate(cirq.SingleQubitGate):
     def _unitary_(self):
         return np.array([[0, 1], [1, 0]])
 
-    def _act_on_(self, args: 'cirq.ActOnArgs', qubits: Sequence['cirq.Qid']):
+    def _act_on_(self, args: 'cirq.OperationTarget', qubits: Sequence['cirq.Qid']):
         if isinstance(args, cirq.ActOnCliffordTableauArgs):
             tableau = args.tableau
             q = args.qubit_map[qubits[0]]
@@ -37,7 +37,7 @@ class BadGate(cirq.SingleQubitGate):
     def _unitary_(self):
         return np.array([[0, 1j], [1, 0]])
 
-    def _act_on_(self, args: 'cirq.ActOnArgs', qubits: Sequence['cirq.Qid']):
+    def _act_on_(self, args: 'cirq.OperationTarget', qubits: Sequence['cirq.Qid']):
         if isinstance(args, cirq.ActOnCliffordTableauArgs):
             tableau = args.tableau
             q = args.qubit_map[qubits[0]]