fix accidental copy + paste breakage

Author: d-v-b

src/zarr/core/dtype/npy/structured.py

@@ -2,7 +2,7 @@
 
 from collections.abc import Sequence
 from dataclasses import dataclass
-from typing import TYPE_CHECKING, Literal, Self, TypeGuard, cast, overload
+from typing import TYPE_CHECKING, ClassVar, Literal, Self, TypeGuard, cast, overload
 
 import numpy as np
 
@@ -103,6 +103,7 @@ class Structured(ZDType[np.dtypes.VoidDType[int], np.void], HasItemSize):
     The Zarr V2 data type specification can be found `here <https://github.com/zarr-developers/zarr-specs/blob/main/docs/v2/v2.0.rst#data-type-encoding>`_.
     """
 
+    _zarr_v3_name: ClassVar[Literal["structured"]] = "structured"
     dtype_cls = np.dtypes.VoidDType  # type: ignore[assignment]
     fields: tuple[tuple[str, ZDType[TBaseDType, TBaseScalar]], ...]
 

src/zarr/core/dtype/npy/time.py

@@ -356,7 +356,7 @@ class TimeDelta64(TimeDTypeBase[np.dtypes.TimeDelta64DType, np.timedelta64], Has
     unit: DateTimeUnit = "generic"
     scale_factor: int = 1
     _zarr_v3_name: ClassVar[Literal["numpy.timedelta64"]] = "numpy.timedelta64"
-    _zarr_v2_names: tuple[Literal[">m8"], Literal["<m8"]] = (">m8", "<m8")
+    _zarr_v2_names: ClassVar[tuple[Literal[">m8"], Literal["<m8"]]] = (">m8", "<m8")
     _numpy_name: ClassVar[Literal["timedelta64"]] = "timedelta64"
 
     @classmethod
@@ -620,7 +620,7 @@ class DateTime64(TimeDTypeBase[np.dtypes.DateTime64DType, np.datetime64], HasEnd
 
     dtype_cls = np.dtypes.DateTime64DType  # type: ignore[assignment]
     _zarr_v3_name: ClassVar[Literal["numpy.datetime64"]] = "numpy.datetime64"
-    _zarr_v2_names: tuple[Literal[">M8"], Literal["<M8"]] = (">M8", "<M8")
+    _zarr_v2_names: ClassVar[tuple[Literal[">M8"], Literal["<M8"]]] = (">M8", "<M8")
     _numpy_name: ClassVar[Literal["datetime64"]] = "datetime64"
     unit: DateTimeUnit = "generic"
     scale_factor: int = 1