From fd95547ac4962cfa3d0d1ff707a8de26ce148511 Mon Sep 17 00:00:00 2001
From: Festus Ayobami Owumi <festusowumi@gmail.com>
Date: Wed, 13 Nov 2024 09:01:18 +0100
Subject: [PATCH] Replace type_workarounds.NotImplementedType with
 types.NotImplementedType (#6790)

- Replaced type_workarounds.NotImplementedType with types.NotImplementedType,
  removing the need for the type_workarounds module.

- This change simplifies the codebase by relying on standard types,
  allowing us to delete the now-redundant type_workarounds.py file.

Fixes #6775
---
 cirq-core/cirq/__init__.py                    |  1 -
 cirq-core/cirq/circuits/circuit.py            |  2 +-
 cirq-core/cirq/circuits/frozen_circuit.py     |  2 +-
 cirq-core/cirq/circuits/moment.py             |  3 ++-
 .../cirq/contrib/acquaintance/permutation.py  |  2 +-
 .../paulistring/clifford_target_gateset.py    |  3 ++-
 cirq-core/cirq/ops/clifford_gate.py           |  6 ++---
 cirq-core/cirq/ops/common_gates.py            |  4 +---
 cirq-core/cirq/ops/controlled_gate.py         |  4 ++--
 cirq-core/cirq/ops/controlled_gate_test.py    |  2 +-
 cirq-core/cirq/ops/controlled_operation.py    |  2 +-
 .../cirq/ops/controlled_operation_test.py     |  2 +-
 cirq-core/cirq/ops/dense_pauli_string.py      |  2 +-
 cirq-core/cirq/ops/eigen_gate.py              |  2 +-
 cirq-core/cirq/ops/gate_operation.py          |  2 +-
 cirq-core/cirq/ops/global_phase_op.py         |  2 +-
 cirq-core/cirq/ops/identity.py                |  2 +-
 cirq-core/cirq/ops/parallel_gate.py           |  3 +--
 cirq-core/cirq/ops/pauli_gates.py             |  2 +-
 cirq-core/cirq/ops/pauli_string.py            |  2 +-
 cirq-core/cirq/ops/phased_x_gate.py           |  6 +++--
 cirq-core/cirq/ops/raw_types.py               |  4 ++--
 cirq-core/cirq/protocols/act_on_protocol.py   |  2 +-
 .../cirq/protocols/apply_channel_protocol.py  |  2 +-
 .../cirq/protocols/apply_mixture_protocol.py  |  3 +--
 .../cirq/protocols/apply_unitary_protocol.py  |  2 +-
 cirq-core/cirq/protocols/commutes_protocol.py |  2 +-
 .../cirq/protocols/control_key_protocol.py    |  2 +-
 .../cirq/protocols/decompose_protocol.py      |  2 +-
 .../cirq/protocols/json_serialization.py      |  2 +-
 cirq-core/cirq/protocols/kraus_protocol.py    |  4 +---
 .../protocols/measurement_key_protocol.py     |  2 +-
 cirq-core/cirq/protocols/mixture_protocol.py  |  3 ++-
 cirq-core/cirq/protocols/qasm.py              |  2 +-
 .../cirq/protocols/qid_shape_protocol.py      |  2 +-
 cirq-core/cirq/protocols/unitary_protocol.py  |  2 +-
 .../clifford/stabilizer_simulation_state.py   |  2 +-
 cirq-core/cirq/sim/simulation_state_base.py   |  2 +-
 .../cirq/testing/consistent_protocols_test.py |  2 +-
 cirq-core/cirq/type_workarounds.py            | 23 -------------------
 40 files changed, 48 insertions(+), 73 deletions(-)
 delete mode 100644 cirq-core/cirq/type_workarounds.py

diff --git a/cirq-core/cirq/__init__.py b/cirq-core/cirq/__init__.py
index 15a014d16f1..9293a7e7bfc 100644
--- a/cirq-core/cirq/__init__.py
+++ b/cirq-core/cirq/__init__.py
@@ -26,7 +26,6 @@
     # Low level
     _version,
     _doc,
-    type_workarounds,
 )
 
 with _import.delay_import('cirq.protocols'):
diff --git a/cirq-core/cirq/circuits/circuit.py b/cirq-core/cirq/circuits/circuit.py
index 24de6a0a5d4..3e0f10f8c6a 100644
--- a/cirq-core/cirq/circuits/circuit.py
+++ b/cirq-core/cirq/circuits/circuit.py
@@ -25,6 +25,7 @@
 import itertools
 import math
 from collections import defaultdict
+from types import NotImplementedType
 from typing import (
     AbstractSet,
     Any,
@@ -62,7 +63,6 @@
 from cirq.circuits.qasm_output import QasmOutput
 from cirq.circuits.text_diagram_drawer import TextDiagramDrawer
 from cirq.protocols import circuit_diagram_info_protocol
-from cirq.type_workarounds import NotImplementedType
 
 if TYPE_CHECKING:
     import cirq
diff --git a/cirq-core/cirq/circuits/frozen_circuit.py b/cirq-core/cirq/circuits/frozen_circuit.py
index 0781213d954..15bf107d900 100644
--- a/cirq-core/cirq/circuits/frozen_circuit.py
+++ b/cirq-core/cirq/circuits/frozen_circuit.py
@@ -13,6 +13,7 @@
 # limitations under the License.
 """An immutable version of the Circuit data structure."""
 from functools import cached_property
+from types import NotImplementedType
 from typing import (
     AbstractSet,
     FrozenSet,
@@ -30,7 +31,6 @@
 from cirq import protocols, _compat
 from cirq.circuits import AbstractCircuit, Alignment, Circuit
 from cirq.circuits.insert_strategy import InsertStrategy
-from cirq.type_workarounds import NotImplementedType
 
 if TYPE_CHECKING:
     import cirq
diff --git a/cirq-core/cirq/circuits/moment.py b/cirq-core/cirq/circuits/moment.py
index 923adfbd0de..b64957eeb1e 100644
--- a/cirq-core/cirq/circuits/moment.py
+++ b/cirq-core/cirq/circuits/moment.py
@@ -15,6 +15,7 @@
 """A simplified time-slice of operations within a sequenced circuit."""
 
 import itertools
+from types import NotImplementedType
 from typing import (
     AbstractSet,
     Any,
@@ -33,6 +34,7 @@
     TYPE_CHECKING,
     Union,
 )
+
 from typing_extensions import Self
 
 import numpy as np
@@ -41,7 +43,6 @@
 from cirq._import import LazyLoader
 from cirq.ops import raw_types, op_tree
 from cirq.protocols import circuit_diagram_info_protocol
-from cirq.type_workarounds import NotImplementedType
 
 if TYPE_CHECKING:
     import cirq
diff --git a/cirq-core/cirq/contrib/acquaintance/permutation.py b/cirq-core/cirq/contrib/acquaintance/permutation.py
index cae68eee1ef..383b3731690 100644
--- a/cirq-core/cirq/contrib/acquaintance/permutation.py
+++ b/cirq-core/cirq/contrib/acquaintance/permutation.py
@@ -13,6 +13,7 @@
 # limitations under the License.
 
 import abc
+from types import NotImplementedType
 from typing import (
     Any,
     cast,
@@ -28,7 +29,6 @@
 )
 
 from cirq import circuits, ops, protocols, transformers, value
-from cirq.type_workarounds import NotImplementedType
 
 if TYPE_CHECKING:
     import cirq
diff --git a/cirq-core/cirq/contrib/paulistring/clifford_target_gateset.py b/cirq-core/cirq/contrib/paulistring/clifford_target_gateset.py
index ae555a0bc07..1b20f91d70c 100644
--- a/cirq-core/cirq/contrib/paulistring/clifford_target_gateset.py
+++ b/cirq-core/cirq/contrib/paulistring/clifford_target_gateset.py
@@ -12,12 +12,13 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
+from types import NotImplementedType
 from typing import List, Union, Type, cast, TYPE_CHECKING
 from enum import Enum
+
 import numpy as np
 
 from cirq import ops, transformers, protocols, linalg
-from cirq.type_workarounds import NotImplementedType
 
 if TYPE_CHECKING:
     import cirq
diff --git a/cirq-core/cirq/ops/clifford_gate.py b/cirq-core/cirq/ops/clifford_gate.py
index 82ce7ebe42e..972c7a1b4c1 100644
--- a/cirq-core/cirq/ops/clifford_gate.py
+++ b/cirq-core/cirq/ops/clifford_gate.py
@@ -12,10 +12,11 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-from typing import Any, Dict, List, Optional, Sequence, Tuple, TYPE_CHECKING, Union
-
 import functools
 from dataclasses import dataclass
+from types import NotImplementedType
+from typing import Any, Dict, List, Optional, Sequence, Tuple, TYPE_CHECKING, Union
+
 import numpy as np
 
 from cirq import protocols, value, linalg, qis
@@ -23,7 +24,6 @@
 from cirq._compat import cached_method
 from cirq.ops import common_gates, named_qubit, raw_types, pauli_gates, phased_x_z_gate
 from cirq.ops.pauli_gates import Pauli
-from cirq.type_workarounds import NotImplementedType
 
 if TYPE_CHECKING:
     import cirq
diff --git a/cirq-core/cirq/ops/common_gates.py b/cirq-core/cirq/ops/common_gates.py
index af259c6d19b..fea2ac9996f 100644
--- a/cirq-core/cirq/ops/common_gates.py
+++ b/cirq-core/cirq/ops/common_gates.py
@@ -25,6 +25,7 @@
 raised to a power (i.e. cirq.H**0.5). See the definition in EigenGate.
 """
 
+from types import NotImplementedType
 from typing import (
     Any,
     cast,
@@ -46,9 +47,6 @@
 from cirq._compat import proper_repr
 from cirq._doc import document
 from cirq.ops import controlled_gate, eigen_gate, gate_features, raw_types, control_values as cv
-
-from cirq.type_workarounds import NotImplementedType
-
 from cirq.ops.swap_gates import ISWAP, SWAP, ISwapPowGate, SwapPowGate
 from cirq.ops.measurement_gate import MeasurementGate
 
diff --git a/cirq-core/cirq/ops/controlled_gate.py b/cirq-core/cirq/ops/controlled_gate.py
index 641b52fb9ff..292c13dc3d2 100644
--- a/cirq-core/cirq/ops/controlled_gate.py
+++ b/cirq-core/cirq/ops/controlled_gate.py
@@ -12,6 +12,7 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
+from types import NotImplementedType
 from typing import (
     AbstractSet,
     Any,
@@ -35,7 +36,6 @@
     matrix_gates,
     control_values as cv,
 )
-from cirq.type_workarounds import NotImplementedType
 
 if TYPE_CHECKING:
     import cirq
@@ -255,7 +255,7 @@ def _unitary_(self) -> Union[np.ndarray, NotImplementedType]:
     def _has_mixture_(self) -> bool:
         return protocols.has_mixture(self.sub_gate)
 
-    def _mixture_(self) -> Union[np.ndarray, NotImplementedType]:
+    def _mixture_(self) -> Union[Sequence[tuple[float, np.ndarray]], NotImplementedType]:
         qubits = line_qubit.LineQid.for_gate(self)
         op = self.sub_gate.on(*qubits[self.num_controls() :])
         c_op = cop.ControlledOperation(qubits[: self.num_controls()], op, self.control_values)
diff --git a/cirq-core/cirq/ops/controlled_gate_test.py b/cirq-core/cirq/ops/controlled_gate_test.py
index b9e09c5a6e1..555c04bb850 100644
--- a/cirq-core/cirq/ops/controlled_gate_test.py
+++ b/cirq-core/cirq/ops/controlled_gate_test.py
@@ -12,6 +12,7 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
+from types import NotImplementedType
 from typing import Union, Tuple, cast
 
 import numpy as np
@@ -19,7 +20,6 @@
 import sympy
 
 import cirq
-from cirq.type_workarounds import NotImplementedType
 
 
 class GateUsingWorkspaceForApplyUnitary(cirq.testing.SingleQubitGate):
diff --git a/cirq-core/cirq/ops/controlled_operation.py b/cirq-core/cirq/ops/controlled_operation.py
index 85c61cb298d..dbcd3026327 100644
--- a/cirq-core/cirq/ops/controlled_operation.py
+++ b/cirq-core/cirq/ops/controlled_operation.py
@@ -12,6 +12,7 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
+from types import NotImplementedType
 from typing import (
     AbstractSet,
     Any,
@@ -38,7 +39,6 @@
     raw_types,
     control_values as cv,
 )
-from cirq.type_workarounds import NotImplementedType
 
 if TYPE_CHECKING:
     import cirq
diff --git a/cirq-core/cirq/ops/controlled_operation_test.py b/cirq-core/cirq/ops/controlled_operation_test.py
index 1f1cb3a2531..dc6f2a7ece4 100644
--- a/cirq-core/cirq/ops/controlled_operation_test.py
+++ b/cirq-core/cirq/ops/controlled_operation_test.py
@@ -14,6 +14,7 @@
 
 import itertools
 import re
+from types import NotImplementedType
 from typing import cast, Tuple, Union
 
 import numpy as np
@@ -22,7 +23,6 @@
 
 import cirq
 from cirq import protocols
-from cirq.type_workarounds import NotImplementedType
 
 
 class GateUsingWorkspaceForApplyUnitary(cirq.testing.SingleQubitGate):
diff --git a/cirq-core/cirq/ops/dense_pauli_string.py b/cirq-core/cirq/ops/dense_pauli_string.py
index 9893b64f706..f5f07953f78 100644
--- a/cirq-core/cirq/ops/dense_pauli_string.py
+++ b/cirq-core/cirq/ops/dense_pauli_string.py
@@ -14,6 +14,7 @@
 
 import abc
 import numbers
+from types import NotImplementedType
 from typing import (
     AbstractSet,
     Any,
@@ -38,7 +39,6 @@
 from cirq import protocols, linalg, value
 from cirq._compat import proper_repr
 from cirq.ops import raw_types, identity, pauli_gates, global_phase_op, pauli_string
-from cirq.type_workarounds import NotImplementedType
 
 if TYPE_CHECKING:
     import cirq
diff --git a/cirq-core/cirq/ops/eigen_gate.py b/cirq-core/cirq/ops/eigen_gate.py
index f11637b4fd6..b9ffbed9702 100644
--- a/cirq-core/cirq/ops/eigen_gate.py
+++ b/cirq-core/cirq/ops/eigen_gate.py
@@ -15,6 +15,7 @@
 import fractions
 import math
 import numbers
+from types import NotImplementedType
 from typing import (
     AbstractSet,
     Any,
@@ -35,7 +36,6 @@
 from cirq import value, protocols
 from cirq.linalg import tolerance
 from cirq.ops import raw_types
-from cirq.type_workarounds import NotImplementedType
 
 if TYPE_CHECKING:
     import cirq
diff --git a/cirq-core/cirq/ops/gate_operation.py b/cirq-core/cirq/ops/gate_operation.py
index db5be010923..0101111a4cc 100644
--- a/cirq-core/cirq/ops/gate_operation.py
+++ b/cirq-core/cirq/ops/gate_operation.py
@@ -16,6 +16,7 @@
 
 import re
 import warnings
+from types import NotImplementedType
 from typing import (
     AbstractSet,
     Any,
@@ -38,7 +39,6 @@
 
 from cirq import ops, protocols, value
 from cirq.ops import raw_types, gate_features, control_values as cv
-from cirq.type_workarounds import NotImplementedType
 
 if TYPE_CHECKING:
     import cirq
diff --git a/cirq-core/cirq/ops/global_phase_op.py b/cirq-core/cirq/ops/global_phase_op.py
index 6a64a634aa6..5348c5632e3 100644
--- a/cirq-core/cirq/ops/global_phase_op.py
+++ b/cirq-core/cirq/ops/global_phase_op.py
@@ -13,6 +13,7 @@
 # limitations under the License.
 """A no-qubit global phase operation."""
 
+from types import NotImplementedType
 from typing import AbstractSet, Any, cast, Dict, Sequence, Tuple, Union, Optional, Collection
 
 import numpy as np
@@ -21,7 +22,6 @@
 import cirq
 from cirq import value, protocols
 from cirq.ops import raw_types, controlled_gate, control_values as cv
-from cirq.type_workarounds import NotImplementedType
 
 
 @value.value_equality(approximate=True)
diff --git a/cirq-core/cirq/ops/identity.py b/cirq-core/cirq/ops/identity.py
index 361e70c4ea7..46de3bea8fd 100644
--- a/cirq-core/cirq/ops/identity.py
+++ b/cirq-core/cirq/ops/identity.py
@@ -13,6 +13,7 @@
 # limitations under the License.
 """IdentityGate."""
 
+from types import NotImplementedType
 from typing import Any, Dict, Optional, Tuple, TYPE_CHECKING, Sequence, Union
 
 import numpy as np
@@ -20,7 +21,6 @@
 
 from cirq import protocols, value
 from cirq._doc import document
-from cirq.type_workarounds import NotImplementedType
 from cirq.ops import raw_types
 
 if TYPE_CHECKING:
diff --git a/cirq-core/cirq/ops/parallel_gate.py b/cirq-core/cirq/ops/parallel_gate.py
index 9fefa56289d..584d76d43ff 100644
--- a/cirq-core/cirq/ops/parallel_gate.py
+++ b/cirq-core/cirq/ops/parallel_gate.py
@@ -12,14 +12,13 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-
+from types import NotImplementedType
 from typing import AbstractSet, Union, Any, Optional, Tuple, TYPE_CHECKING, Dict
 
 import numpy as np
 
 from cirq import protocols, value
 from cirq.ops import raw_types
-from cirq.type_workarounds import NotImplementedType
 
 if TYPE_CHECKING:
     import cirq
diff --git a/cirq-core/cirq/ops/pauli_gates.py b/cirq-core/cirq/ops/pauli_gates.py
index a2132a6a4bb..e09e5ede009 100644
--- a/cirq-core/cirq/ops/pauli_gates.py
+++ b/cirq-core/cirq/ops/pauli_gates.py
@@ -12,12 +12,12 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 import abc
+from types import NotImplementedType
 from typing import Any, cast, Tuple, TYPE_CHECKING, Union, Dict
 
 from cirq._doc import document
 from cirq._import import LazyLoader
 from cirq.ops import common_gates, raw_types, identity
-from cirq.type_workarounds import NotImplementedType
 
 
 if TYPE_CHECKING:
diff --git a/cirq-core/cirq/ops/pauli_string.py b/cirq-core/cirq/ops/pauli_string.py
index 1978b6ba031..f8ad21015e6 100644
--- a/cirq-core/cirq/ops/pauli_string.py
+++ b/cirq-core/cirq/ops/pauli_string.py
@@ -14,6 +14,7 @@
 import cmath
 import math
 import numbers
+from types import NotImplementedType
 from typing import (
     Any,
     cast,
@@ -56,7 +57,6 @@
     pauli_interaction_gate,
     raw_types,
 )
-from cirq.type_workarounds import NotImplementedType
 
 if TYPE_CHECKING:
     import cirq
diff --git a/cirq-core/cirq/ops/phased_x_gate.py b/cirq-core/cirq/ops/phased_x_gate.py
index 26548a64b47..4a1b6069268 100644
--- a/cirq-core/cirq/ops/phased_x_gate.py
+++ b/cirq-core/cirq/ops/phased_x_gate.py
@@ -12,10 +12,13 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 """An `XPowGate` conjugated by `ZPowGate`s."""
+
+from types import NotImplementedType
 from typing import AbstractSet, Any, cast, Dict, Optional, Sequence, Tuple, Union
 
 import math
 import numbers
+
 import numpy as np
 import sympy
 
@@ -23,7 +26,6 @@
 from cirq import value, protocols
 from cirq._compat import proper_repr
 from cirq.ops import common_gates, raw_types
-from cirq.type_workarounds import NotImplementedType
 
 
 @value.value_equality(manual_cls=True, approximate=True)
@@ -130,7 +132,7 @@ def _trace_distance_bound_(self) -> Optional[float]:
     def _has_unitary_(self):
         return not self._is_parameterized_()
 
-    def _unitary_(self) -> Union[np.ndarray, NotImplementedType]:
+    def _unitary_(self) -> Optional[Union[np.ndarray, NotImplementedType]]:
         """See `cirq.SupportsUnitary`."""
         if self._is_parameterized_():
             return None
diff --git a/cirq-core/cirq/ops/raw_types.py b/cirq-core/cirq/ops/raw_types.py
index 5c67151a826..696868fe780 100644
--- a/cirq-core/cirq/ops/raw_types.py
+++ b/cirq-core/cirq/ops/raw_types.py
@@ -16,6 +16,7 @@
 
 import abc
 import functools
+from types import NotImplementedType
 from typing import (
     cast,
     AbstractSet,
@@ -42,7 +43,6 @@
 from cirq import protocols, value
 from cirq._import import LazyLoader
 from cirq._compat import __cirq_debug__, _method_cache_name, cached_method
-from cirq.type_workarounds import NotImplementedType
 from cirq.ops import control_values as cv
 
 # Lazy imports to break circular dependencies.
@@ -879,7 +879,7 @@ def _mixture_(self) -> Sequence[Tuple[float, Any]]:
     def _has_kraus_(self) -> bool:
         return protocols.has_kraus(self.sub_operation)
 
-    def _kraus_(self) -> Union[Tuple[np.ndarray], NotImplementedType]:
+    def _kraus_(self) -> Union[Tuple[np.ndarray, ...], NotImplementedType]:
         return protocols.kraus(self.sub_operation, NotImplemented)
 
     @cached_method
diff --git a/cirq-core/cirq/protocols/act_on_protocol.py b/cirq-core/cirq/protocols/act_on_protocol.py
index 8ac4875c01c..87fedb38038 100644
--- a/cirq-core/cirq/protocols/act_on_protocol.py
+++ b/cirq-core/cirq/protocols/act_on_protocol.py
@@ -12,13 +12,13 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
+from types import NotImplementedType
 from typing import Any, Optional, Sequence, TYPE_CHECKING, Union
 
 from typing_extensions import Protocol
 
 from cirq import ops
 from cirq._doc import doc_private
-from cirq.type_workarounds import NotImplementedType
 
 if TYPE_CHECKING:
     import cirq
diff --git a/cirq-core/cirq/protocols/apply_channel_protocol.py b/cirq-core/cirq/protocols/apply_channel_protocol.py
index a6c8f283718..75c4b5e8b5f 100644
--- a/cirq-core/cirq/protocols/apply_channel_protocol.py
+++ b/cirq-core/cirq/protocols/apply_channel_protocol.py
@@ -14,6 +14,7 @@
 
 """A protocol for implementing high performance channel evolutions."""
 
+from types import NotImplementedType
 from typing import Any, Iterable, Optional, Sequence, TypeVar, Tuple, Union
 
 import numpy as np
@@ -24,7 +25,6 @@
 from cirq.protocols.apply_unitary_protocol import apply_unitary, ApplyUnitaryArgs
 from cirq.protocols.kraus_protocol import kraus
 from cirq.protocols import qid_shape_protocol
-from cirq.type_workarounds import NotImplementedType
 
 # This is a special indicator value used by the apply_channel method
 # to determine whether or not the caller provided a 'default' argument. It must
diff --git a/cirq-core/cirq/protocols/apply_mixture_protocol.py b/cirq-core/cirq/protocols/apply_mixture_protocol.py
index 121fc1b6dfd..5ff9414f5dd 100644
--- a/cirq-core/cirq/protocols/apply_mixture_protocol.py
+++ b/cirq-core/cirq/protocols/apply_mixture_protocol.py
@@ -14,6 +14,7 @@
 
 """A protocol for implementing high performance mixture evolutions."""
 
+from types import NotImplementedType
 from typing import Any, cast, Iterable, Optional, Tuple, TypeVar, Union
 
 import numpy as np
@@ -22,10 +23,8 @@
 from cirq import linalg
 from cirq._doc import doc_private
 from cirq.protocols.apply_unitary_protocol import apply_unitary, ApplyUnitaryArgs
-
 from cirq.protocols.mixture_protocol import mixture
 from cirq.protocols import qid_shape_protocol
-from cirq.type_workarounds import NotImplementedType
 
 # This is a special indicator value used by the apply_mixture method
 # to determine whether or not the caller provided a 'default' argument. It must
diff --git a/cirq-core/cirq/protocols/apply_unitary_protocol.py b/cirq-core/cirq/protocols/apply_unitary_protocol.py
index 9cdbb96aa07..4decd6207bc 100644
--- a/cirq-core/cirq/protocols/apply_unitary_protocol.py
+++ b/cirq-core/cirq/protocols/apply_unitary_protocol.py
@@ -15,6 +15,7 @@
 """A protocol for implementing high performance unitary left-multiplies."""
 
 import warnings
+from types import NotImplementedType
 from typing import Any, cast, Iterable, Optional, Sequence, Tuple, TYPE_CHECKING, TypeVar, Union
 
 import numpy as np
@@ -24,7 +25,6 @@
 from cirq._doc import doc_private
 from cirq.protocols import qid_shape_protocol
 from cirq.protocols.decompose_protocol import _try_decompose_into_operations_and_qubits
-from cirq.type_workarounds import NotImplementedType
 
 if TYPE_CHECKING:
     import cirq
diff --git a/cirq-core/cirq/protocols/commutes_protocol.py b/cirq-core/cirq/protocols/commutes_protocol.py
index 41d97764930..003a9e895ed 100644
--- a/cirq-core/cirq/protocols/commutes_protocol.py
+++ b/cirq-core/cirq/protocols/commutes_protocol.py
@@ -13,6 +13,7 @@
 # limitations under the License.
 """Protocol for determining commutativity."""
 
+from types import NotImplementedType
 from typing import Any, overload, TypeVar, Union
 
 import numpy as np
@@ -20,7 +21,6 @@
 
 from cirq import linalg
 from cirq._doc import doc_private
-from cirq.type_workarounds import NotImplementedType
 
 # This is a special indicator value used by the unitary method to determine
 # whether or not the caller provided a 'default' argument.
diff --git a/cirq-core/cirq/protocols/control_key_protocol.py b/cirq-core/cirq/protocols/control_key_protocol.py
index d8c8a0ea589..5b3b90f80e7 100644
--- a/cirq-core/cirq/protocols/control_key_protocol.py
+++ b/cirq-core/cirq/protocols/control_key_protocol.py
@@ -13,13 +13,13 @@
 # limitations under the License.
 """Protocol for object that have control keys."""
 
+from types import NotImplementedType
 from typing import Any, FrozenSet, TYPE_CHECKING, Union
 
 from typing_extensions import Protocol
 
 from cirq._doc import doc_private
 from cirq.protocols import measurement_key_protocol
-from cirq.type_workarounds import NotImplementedType
 
 if TYPE_CHECKING:
     import cirq
diff --git a/cirq-core/cirq/protocols/decompose_protocol.py b/cirq-core/cirq/protocols/decompose_protocol.py
index c920a630830..99633e295be 100644
--- a/cirq-core/cirq/protocols/decompose_protocol.py
+++ b/cirq-core/cirq/protocols/decompose_protocol.py
@@ -15,6 +15,7 @@
 import dataclasses
 import inspect
 from collections import defaultdict
+from types import NotImplementedType
 from typing import (
     TYPE_CHECKING,
     Any,
@@ -37,7 +38,6 @@
 from cirq import devices, ops
 from cirq._doc import doc_private
 from cirq.protocols import qid_shape_protocol
-from cirq.type_workarounds import NotImplementedType
 
 if TYPE_CHECKING:
     import cirq
diff --git a/cirq-core/cirq/protocols/json_serialization.py b/cirq-core/cirq/protocols/json_serialization.py
index 070b4818ba0..92315403f51 100644
--- a/cirq-core/cirq/protocols/json_serialization.py
+++ b/cirq-core/cirq/protocols/json_serialization.py
@@ -17,6 +17,7 @@
 import json
 import numbers
 import pathlib
+from types import NotImplementedType
 from typing import (
     Any,
     Callable,
@@ -39,7 +40,6 @@
 from typing_extensions import Protocol
 
 from cirq._doc import doc_private
-from cirq.type_workarounds import NotImplementedType
 
 ObjectFactory = Union[Type, Callable[..., Any]]
 
diff --git a/cirq-core/cirq/protocols/kraus_protocol.py b/cirq-core/cirq/protocols/kraus_protocol.py
index bc661e5633d..695ebd2e75e 100644
--- a/cirq-core/cirq/protocols/kraus_protocol.py
+++ b/cirq-core/cirq/protocols/kraus_protocol.py
@@ -14,6 +14,7 @@
 
 """Protocol and methods for obtaining Kraus representation of quantum channels."""
 
+from types import NotImplementedType
 from typing import Any, Sequence, Tuple, TypeVar, Union
 import warnings
 
@@ -25,9 +26,6 @@
 from cirq.protocols.mixture_protocol import has_mixture
 
 
-from cirq.type_workarounds import NotImplementedType
-
-
 # This is a special indicator value used by the channel method to determine
 # whether or not the caller provided a 'default' argument. It must be of type
 # Sequence[np.ndarray] to ensure the method has the correct type signature in
diff --git a/cirq-core/cirq/protocols/measurement_key_protocol.py b/cirq-core/cirq/protocols/measurement_key_protocol.py
index 07b44d784a4..44cc2f93fd9 100644
--- a/cirq-core/cirq/protocols/measurement_key_protocol.py
+++ b/cirq-core/cirq/protocols/measurement_key_protocol.py
@@ -13,13 +13,13 @@
 # limitations under the License.
 """Protocol for object that have measurement keys."""
 
+from types import NotImplementedType
 from typing import Any, FrozenSet, Mapping, Optional, Tuple, TYPE_CHECKING, Union
 
 from typing_extensions import Protocol
 
 from cirq import value
 from cirq._doc import doc_private
-from cirq.type_workarounds import NotImplementedType
 
 if TYPE_CHECKING:
     import cirq
diff --git a/cirq-core/cirq/protocols/mixture_protocol.py b/cirq-core/cirq/protocols/mixture_protocol.py
index 5b3b79ae93e..fa70af631a2 100644
--- a/cirq-core/cirq/protocols/mixture_protocol.py
+++ b/cirq-core/cirq/protocols/mixture_protocol.py
@@ -13,6 +13,8 @@
 # limitations under the License.
 
 """Protocol for objects that are mixtures (probabilistic combinations)."""
+
+from types import NotImplementedType
 from typing import Any, Sequence, Tuple, Union
 
 import numpy as np
@@ -21,7 +23,6 @@
 from cirq._doc import doc_private
 from cirq.protocols.decompose_protocol import _try_decompose_into_operations_and_qubits
 from cirq.protocols.has_unitary_protocol import has_unitary
-from cirq.type_workarounds import NotImplementedType
 
 # This is a special indicator value used by the inverse method to determine
 # whether or not the caller provided a 'default' argument.
diff --git a/cirq-core/cirq/protocols/qasm.py b/cirq-core/cirq/protocols/qasm.py
index 9988df79b94..1700461f210 100644
--- a/cirq-core/cirq/protocols/qasm.py
+++ b/cirq-core/cirq/protocols/qasm.py
@@ -13,13 +13,13 @@
 # limitations under the License.
 
 import string
+from types import NotImplementedType
 from typing import TYPE_CHECKING, Union, Any, Tuple, TypeVar, Optional, Dict, Iterable
 
 from typing_extensions import Protocol
 
 from cirq import ops
 from cirq._doc import doc_private
-from cirq.type_workarounds import NotImplementedType
 
 if TYPE_CHECKING:
     import cirq
diff --git a/cirq-core/cirq/protocols/qid_shape_protocol.py b/cirq-core/cirq/protocols/qid_shape_protocol.py
index 8f2e1f8c331..7e98d8a716a 100644
--- a/cirq-core/cirq/protocols/qid_shape_protocol.py
+++ b/cirq-core/cirq/protocols/qid_shape_protocol.py
@@ -12,13 +12,13 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
+from types import NotImplementedType
 from typing import Any, Sequence, Tuple, TypeVar, Union
 
 from typing_extensions import Protocol
 
 from cirq import ops
 from cirq._doc import document, doc_private
-from cirq.type_workarounds import NotImplementedType
 
 # This is a special indicator value used by the methods to determine whether or
 # not the caller provided a 'default' argument. It must be of type
diff --git a/cirq-core/cirq/protocols/unitary_protocol.py b/cirq-core/cirq/protocols/unitary_protocol.py
index 38de4043dbc..b197a918058 100644
--- a/cirq-core/cirq/protocols/unitary_protocol.py
+++ b/cirq-core/cirq/protocols/unitary_protocol.py
@@ -12,6 +12,7 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
+from types import NotImplementedType
 from typing import Any, TypeVar, Union, Optional
 
 import numpy as np
@@ -21,7 +22,6 @@
 from cirq.protocols import qid_shape_protocol
 from cirq.protocols.apply_unitary_protocol import ApplyUnitaryArgs, apply_unitaries
 from cirq.protocols.decompose_protocol import _try_decompose_into_operations_and_qubits
-from cirq.type_workarounds import NotImplementedType
 
 # This is a special indicator value used by the unitary method to determine
 # whether or not the caller provided a 'default' argument. It must be of type
diff --git a/cirq-core/cirq/sim/clifford/stabilizer_simulation_state.py b/cirq-core/cirq/sim/clifford/stabilizer_simulation_state.py
index bad4bca02c0..5707c9dc566 100644
--- a/cirq-core/cirq/sim/clifford/stabilizer_simulation_state.py
+++ b/cirq-core/cirq/sim/clifford/stabilizer_simulation_state.py
@@ -13,6 +13,7 @@
 # limitations under the License.
 
 import abc
+from types import NotImplementedType
 from typing import Any, cast, Generic, Optional, Sequence, TYPE_CHECKING, TypeVar, Union
 
 import numpy as np
@@ -23,7 +24,6 @@
 from cirq.ops.clifford_gate import SingleQubitCliffordGate
 from cirq.protocols import has_unitary, num_qubits, unitary
 from cirq.sim.simulation_state import SimulationState
-from cirq.type_workarounds import NotImplementedType
 
 if TYPE_CHECKING:
     import cirq
diff --git a/cirq-core/cirq/sim/simulation_state_base.py b/cirq-core/cirq/sim/simulation_state_base.py
index 684813f07d5..8cf9d0a85c5 100644
--- a/cirq-core/cirq/sim/simulation_state_base.py
+++ b/cirq-core/cirq/sim/simulation_state_base.py
@@ -13,6 +13,7 @@
 # limitations under the License.
 """An interface for quantum states as targets for operations."""
 import abc
+from types import NotImplementedType
 from typing import (
     Any,
     Dict,
@@ -32,7 +33,6 @@
 import numpy as np
 
 from cirq import protocols, value
-from cirq.type_workarounds import NotImplementedType
 
 if TYPE_CHECKING:
     import cirq
diff --git a/cirq-core/cirq/testing/consistent_protocols_test.py b/cirq-core/cirq/testing/consistent_protocols_test.py
index 2b1c4572967..330c498a2f5 100644
--- a/cirq-core/cirq/testing/consistent_protocols_test.py
+++ b/cirq-core/cirq/testing/consistent_protocols_test.py
@@ -12,6 +12,7 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
+from types import NotImplementedType
 from typing import AbstractSet, Sequence, Union, List, Tuple
 
 import pytest
@@ -21,7 +22,6 @@
 
 import cirq
 from cirq._compat import proper_repr
-from cirq.type_workarounds import NotImplementedType
 import cirq.testing.consistent_controlled_gate_op_test as controlled_gate_op_test
 
 
diff --git a/cirq-core/cirq/type_workarounds.py b/cirq-core/cirq/type_workarounds.py
deleted file mode 100644
index 6d903f65925..00000000000
--- a/cirq-core/cirq/type_workarounds.py
+++ /dev/null
@@ -1,23 +0,0 @@
-# Copyright 2018 The Cirq Developers
-#
-# Licensed under the Apache License, Version 2.0 (the "License");
-# you may not use this file except in compliance with the License.
-# You may obtain a copy of the License at
-#
-#     https://www.apache.org/licenses/LICENSE-2.0
-#
-# Unless required by applicable law or agreed to in writing, software
-# distributed under the License is distributed on an "AS IS" BASIS,
-# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-# See the License for the specific language governing permissions and
-# limitations under the License.
-
-"""Workarounds for deficiencies in python's typing system."""
-
-from typing import Any
-
-# At the moment there's no reliable way to say 'NotImplementedType'.
-# - type(NotImplemented) causes mypy to error.
-# - Just NotImplemented causes runtime errors (it's not a type).
-# - The string "NotImplemented" causes runtime errors (in some python versions).
-NotImplementedType = Any