fix NamedArray.imag and NamedArray.real typing info

xarray/namedarray/core.py

@@ -27,6 +27,8 @@
     _DType_co,
     _ScalarType_co,
     _ShapeType_co,
+    _SupportsImag,
+    _SupportsReal,
 )
 from xarray.namedarray.utils import _default, is_duck_dask_array, to_0d_object_array
 
@@ -513,26 +515,30 @@ def data(self, data: duckarray[Any, _DType_co]) -> None:
         self._data = data
 
     @property
-    def imag(self) -> Self:
+    def imag(
+        self: NamedArray[_ShapeType, np.dtype[_SupportsImag[_ScalarType]]],  # type: ignore[type-var]
+    ) -> NamedArray[_ShapeType, np.dtype[_ScalarType]]:
         """
         The imaginary part of the array.
 
         See Also
         --------
         numpy.ndarray.imag
         """
-        return self._replace(data=self.data.imag)  # type: ignore
+        return self._new(data=self.data.imag)
 
     @property
-    def real(self) -> Self:
+    def real(
+        self: NamedArray[_ShapeType, np.dtype[_SupportsReal[_ScalarType]]],  # type: ignore[type-var]
+    ) -> NamedArray[_ShapeType, np.dtype[_ScalarType]]:
         """
         The real part of the array.
 
         See Also
         --------
         numpy.ndarray.real
         """
-        return self._replace(data=self.data.real)  # type: ignore
+        return self._new(data=self.data.real)
 
     def __dask_tokenize__(self) -> Hashable:
         # Use v.data, instead of v._data, in order to cope with the wrappers

xarray/tests/test_namedarray.py

@@ -168,13 +168,25 @@ def test_data(random_inputs: np.ndarray[Any, Any]) -> None:
 
 
 def test_real_and_imag() -> None:
-    named_array: NamedArray[Any, Any]
-    named_array = NamedArray(["x"], np.arange(3) - 1j * np.arange(3))
-    expected_real = np.arange(3)
-    assert np.array_equal(named_array.real.data, expected_real)
+    expected_real: np.ndarray[Any, np.dtype[np.float64]]
+    expected_real = np.arange(3, dtype=np.float64)
+
+    expected_imag: np.ndarray[Any, np.dtype[np.float64]]
+    expected_imag = -np.arange(3, dtype=np.float64)
+
+    arr: np.ndarray[Any, np.dtype[np.complex128]]
+    arr = expected_real + 1j * expected_imag
+
+    named_array: NamedArray[Any, np.dtype[np.complex128]]
+    named_array = NamedArray(["x"], arr)
+
+    actual_real: np.ndarray[Any, np.dtype[np.float64]] = named_array.real.data
+    assert np.array_equal(actual_real, expected_real)
+    assert actual_real.dtype == expected_real.dtype
 
-    expected_imag = -np.arange(3)
-    assert np.array_equal(named_array.imag.data, expected_imag)
+    actual_imag: np.ndarray[Any, np.dtype[np.float64]] = named_array.imag.data
+    assert np.array_equal(actual_imag, expected_imag)
+    assert actual_imag.dtype == expected_imag.dtype
 
 
 # Additional tests as per your original class-based code