unleash confusion map (quantumlib#5717)

Revert "Guard confusion_map usage (quantumlib#5534)"

Assume measure() methods of SimulationState subclasses accept the
`confusion_map` argument.  Remove temporary workaround for methods
not taking `confusion_map`.

Also disable pylint check on missing argument which is required
in the base class but unknown to subclasses actually called.

This reverts commit 25388af.

cirq-core/cirq/ops/measurement_gate.py

@@ -306,19 +306,7 @@ def _act_on_(self, sim_state: 'cirq.SimulationStateBase', qubits: Sequence['cirq
 
         if not isinstance(sim_state, SimulationState):
             return NotImplemented
-        try:
-            sim_state.measure(
-                qubits, self.key, self.full_invert_mask(), confusion_map=self.confusion_map
-            )
-        except TypeError as e:
-            # Ensure that the error was due to confusion_map.
-            if not any("unexpected keyword argument 'confusion_map'" in arg for arg in e.args):
-                raise
-            _compat._warn_or_error(
-                "Starting in v0.16, SimulationState subclasses will be required to accept "
-                "a 'confusion_map' argument. See SimulationState.measure for details."
-            )
-            sim_state.measure(qubits, self.key, self.full_invert_mask())
+        sim_state.measure(qubits, self.key, self.full_invert_mask(), self.confusion_map)
         return True
 
 

cirq-core/cirq/ops/measurement_gate_test.py

@@ -12,12 +12,11 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-from typing import Any, Dict, Optional, Sequence, Tuple, Union, cast
+from typing import cast
 import numpy as np
 import pytest
 
 import cirq
-from cirq.type_workarounds import NotImplementedType
 
 
 @pytest.mark.parametrize(
@@ -504,57 +503,3 @@ def test_act_on_qutrit():
     )
     cirq.act_on(m, args)
     assert args.log_of_measurement_results == {'out': [0, 0]}
-
-
-def test_act_on_no_confusion_map_deprecated():
-    class OldSimState(cirq.StateVectorSimulationState):
-        def __init__(self, *args, **kwargs):
-            super().__init__(*args, **kwargs)
-            self.measured = False
-
-        def _act_on_fallback_(
-            self, action: Any, qubits: Sequence['cirq.Qid'], allow_decompose: bool = True
-        ) -> Union[bool, NotImplementedType]:
-            return NotImplemented  # coverage: ignore
-
-        def measure(  # type: ignore
-            self, qubits: Sequence['cirq.Qid'], key: str, invert_mask: Sequence[bool]
-        ):
-            self.measured = True
-
-    qubits = cirq.LineQubit.range(2)
-    old_state = OldSimState(qubits=qubits)
-    m = cirq.measure(*qubits, key='test')
-    with cirq.testing.assert_deprecated('confusion_map', deadline='v0.16'):
-        cirq.act_on(m, old_state)
-    assert old_state.measured
-
-
-def test_act_on_no_confusion_map_scope_limited():
-    error_msg = "error from deeper in measure"
-
-    class ErrorProneSimState(cirq.StateVectorSimulationState):
-        def __init__(self, *args, **kwargs):
-            super().__init__(*args, **kwargs)
-            self.measured = False
-
-        def _act_on_fallback_(
-            self, action: Any, qubits: Sequence['cirq.Qid'], allow_decompose: bool = True
-        ) -> Union[bool, NotImplementedType]:
-            return NotImplemented  # coverage: ignore
-
-        def measure(
-            self,
-            qubits: Sequence['cirq.Qid'],
-            key: str,
-            invert_mask: Sequence[bool],
-            confusion_map: Optional[Dict[Tuple[int, ...], np.ndarray]] = None,
-        ):
-            raise TypeError(error_msg)
-
-    # Verify that the check doesn't prevent other errors from being raised
-    qubits = cirq.LineQubit.range(2)
-    sv_state = ErrorProneSimState(qubits=qubits)
-    m = cirq.measure(*qubits, key='test')
-    with pytest.raises(TypeError, match=error_msg):
-        cirq.act_on(m, sv_state)

cirq-core/cirq/sim/simulation_state.py

@@ -82,7 +82,7 @@ def measure(
         qubits: Sequence['cirq.Qid'],
         key: str,
         invert_mask: Sequence[bool],
-        confusion_map: Optional[Dict[Tuple[int, ...], np.ndarray]] = None,
+        confusion_map: Dict[Tuple[int, ...], np.ndarray],
     ):
         """Measures the qubits and records to `log_of_measurement_results`.
 
@@ -100,8 +100,7 @@ def measure(
             ValueError: If a measurement key has already been logged to a key.
         """
         bits = self._perform_measurement(qubits)
-        if confusion_map is not None:
-            confused = self._confuse_result(bits, qubits, confusion_map)
+        confused = self._confuse_result(bits, qubits, confusion_map)
         corrected = [bit ^ (bit < 2 and mask) for bit, mask in zip(confused, invert_mask)]
         self._classical_data.record_measurement(
             value.MeasurementKey.parse_serialized(key), corrected, qubits
@@ -184,10 +183,15 @@ def with_qubits(self: TSelf, qubits) -> TSelf:
         Args:
             qubits: The qubits to be added to the state space.
 
-        Regurns:
+        Returns:
             A new subclass object containing the extended state space.
         """
+        # TODO(#5721): Fix inconsistent usage of the `state` argument in the
+        # SimulationState base (required) and in its derived classes (unknown
+        # in StateVectorSimulationState), then remove the pylint filter below.
+        # pylint: disable=missing-kwoa
         new_space = type(self)(qubits=qubits)  # type: ignore
+        # pylint: enable=missing-kwoa
         return self.kronecker_product(new_space)
 
     def factor(