ENH: Add dtype-support to 3 generic/ndarray methods

numpy/__init__.pyi

@@ -1254,20 +1254,9 @@ class _ArrayOrScalarCommon:
     def __deepcopy__(self: _ArraySelf, __memo: Optional[dict] = ...) -> _ArraySelf: ...
     def __eq__(self, other): ...
     def __ne__(self, other): ...
-    def astype(
-        self: _ArraySelf,
-        dtype: DTypeLike,
-        order: _OrderKACF = ...,
-        casting: _Casting = ...,
-        subok: bool = ...,
-        copy: bool = ...,
-    ) -> _ArraySelf: ...
     def copy(self: _ArraySelf, order: _OrderKACF = ...) -> _ArraySelf: ...
     def dump(self, file: str) -> None: ...
     def dumps(self) -> bytes: ...
-    def getfield(
-        self: _ArraySelf, dtype: DTypeLike, offset: int = ...
-    ) -> _ArraySelf: ...
     def tobytes(self, order: _OrderKACF = ...) -> bytes: ...
     # NOTE: `tostring()` is deprecated and therefore excluded
     # def tostring(self, order=...): ...
@@ -1276,14 +1265,6 @@ class _ArrayOrScalarCommon:
     ) -> None: ...
     # generics and 0d arrays return builtin scalars
     def tolist(self) -> Any: ...
-    @overload
-    def view(self, type: Type[_NdArraySubClass]) -> _NdArraySubClass: ...
-    @overload
-    def view(self: _ArraySelf, dtype: DTypeLike = ...) -> _ArraySelf: ...
-    @overload
-    def view(
-        self, dtype: DTypeLike, type: Type[_NdArraySubClass]
-    ) -> _NdArraySubClass: ...
 
     # TODO: Add proper signatures
     def __getitem__(self, key) -> Any: ...
@@ -1665,6 +1646,12 @@ _T_co = TypeVar("_T_co", covariant=True)
 _2Tuple = Tuple[_T, _T]
 _Casting = L["no", "equiv", "safe", "same_kind", "unsafe"]
 
+_DTypeLike = Union[
+    dtype[_ScalarType],
+    Type[_ScalarType],
+    _SupportsDType[dtype[_ScalarType]],
+]
+
 _ArrayUInt_co = NDArray[Union[bool_, unsignedinteger[Any]]]
 _ArrayInt_co = NDArray[Union[bool_, integer[Any]]]
 _ArrayFloat_co = NDArray[Union[bool_, integer[Any], floating[Any]]]
@@ -1914,6 +1901,53 @@ class ndarray(_ArrayOrScalarCommon, Generic[_ShapeType, _DType_co]):
         self, *shape: SupportsIndex, order: _OrderACF = ...
     ) -> ndarray[Any, _DType_co]: ...
 
+    @overload
+    def astype(
+        self,
+        dtype: _DTypeLike[_ScalarType],
+        order: _OrderKACF = ...,
+        casting: _Casting = ...,
+        subok: bool = ...,
+        copy: bool = ...,
+    ) -> NDArray[_ScalarType]: ...
+    @overload
+    def astype(
+        self,
+        dtype: DTypeLike,
+        order: _OrderKACF = ...,
+        casting: _Casting = ...,
+        subok: bool = ...,
+        copy: bool = ...,
+    ) -> NDArray[Any]: ...
+
+    @overload
+    def view(self: _ArraySelf) -> _ArraySelf: ...
+    @overload
+    def view(self, type: Type[_NdArraySubClass]) -> _NdArraySubClass: ...
+    @overload
+    def view(self, dtype: _DTypeLike[_ScalarType]) -> NDArray[_ScalarType]: ...
+    @overload
+    def view(self, dtype: DTypeLike) -> NDArray[Any]: ...
+    @overload
+    def view(
+        self,
+        dtype: DTypeLike,
+        type: Type[_NdArraySubClass],
+    ) -> _NdArraySubClass: ...
+
+    @overload
+    def getfield(
+        self,
+        dtype: _DTypeLike[_ScalarType],
+        offset: SupportsIndex = ...
+    ) -> NDArray[_ScalarType]: ...
+    @overload
+    def getfield(
+        self,
+        dtype: DTypeLike,
+        offset: SupportsIndex = ...
+    ) -> NDArray[Any]: ...
+
     # Dispatch to the underlying `generic` via protocols
     def __int__(
         self: ndarray[Any, dtype[SupportsInt]],  # type: ignore[type-var]
@@ -2886,6 +2920,59 @@ class generic(_ArrayOrScalarCommon):
     def byteswap(self: _ScalarType, inplace: L[False] = ...) -> _ScalarType: ...
     @property
     def flat(self: _ScalarType) -> flatiter[ndarray[Any, dtype[_ScalarType]]]: ...
+
+    @overload
+    def astype(
+        self,
+        dtype: _DTypeLike[_ScalarType],
+        order: _OrderKACF = ...,
+        casting: _Casting = ...,
+        subok: bool = ...,
+        copy: bool = ...,
+    ) -> _ScalarType: ...
+    @overload
+    def astype(
+        self,
+        dtype: DTypeLike,
+        order: _OrderKACF = ...,
+        casting: _Casting = ...,
+        subok: bool = ...,
+        copy: bool = ...,
+    ) -> Any: ...
+
+    # NOTE: `view` will perform a 0D->scalar cast,
+    # thus the array `type` is irrelevant to the output type
+    @overload
+    def view(
+        self: _ScalarType,
+        type: Type[ndarray[Any, Any]] = ...,
+    ) -> _ScalarType: ...
+    @overload
+    def view(
+        self,
+        dtype: _DTypeLike[_ScalarType],
+        type: Type[ndarray[Any, Any]] = ...,
+    ) -> _ScalarType: ...
+    @overload
+    def view(
+        self,
+        dtype: DTypeLike,
+        type: Type[ndarray[Any, Any]] = ...,
+    ) -> Any: ...
+
+    @overload
+    def getfield(
+        self,
+        dtype: _DTypeLike[_ScalarType],
+        offset: SupportsIndex = ...
+    ) -> _ScalarType: ...
+    @overload
+    def getfield(
+        self,
+        dtype: DTypeLike,
+        offset: SupportsIndex = ...
+    ) -> Any: ...
+
     def item(
         self,
         __args: Union[L[0], Tuple[()], Tuple[L[0]]] = ...,

numpy/typing/tests/data/reveal/ndarray_conversion.py

@@ -1,12 +1,13 @@
 import numpy as np
+import numpy.typing as npt
 
-nd = np.array([[1, 2], [3, 4]])
+nd: npt.NDArray[np.int_] = np.array([[1, 2], [3, 4]])
 
 # item
-reveal_type(nd.item())  # E: Any
-reveal_type(nd.item(1))  # E: Any
-reveal_type(nd.item(0, 1))  # E: Any
-reveal_type(nd.item((0, 1)))  # E: Any
+reveal_type(nd.item())  # E: int
+reveal_type(nd.item(1))  # E: int
+reveal_type(nd.item(0, 1))  # E: int
+reveal_type(nd.item((0, 1)))  # E: int
 
 # tolist
 reveal_type(nd.tolist())  # E: Any
@@ -19,36 +20,32 @@
 # dumps is pretty simple
 
 # astype
-reveal_type(nd.astype("float"))  # E: numpy.ndarray
-reveal_type(nd.astype(float))  # E: numpy.ndarray
-reveal_type(nd.astype(float, "K"))  # E: numpy.ndarray
-reveal_type(nd.astype(float, "K", "unsafe"))  # E: numpy.ndarray
-reveal_type(nd.astype(float, "K", "unsafe", True))  # E: numpy.ndarray
-reveal_type(nd.astype(float, "K", "unsafe", True, True))  # E: numpy.ndarray
+reveal_type(nd.astype("float"))  # E: numpy.ndarray[Any, numpy.dtype[Any]]
+reveal_type(nd.astype(float))  # E: numpy.ndarray[Any, numpy.dtype[Any]]
+reveal_type(nd.astype(np.float64))  # E: numpy.ndarray[Any, numpy.dtype[{float64}]]
+reveal_type(nd.astype(np.float64, "K"))  # E: numpy.ndarray[Any, numpy.dtype[{float64}]]
+reveal_type(nd.astype(np.float64, "K", "unsafe"))  # E: numpy.ndarray[Any, numpy.dtype[{float64}]]
+reveal_type(nd.astype(np.float64, "K", "unsafe", True))  # E: numpy.ndarray[Any, numpy.dtype[{float64}]]
+reveal_type(nd.astype(np.float64, "K", "unsafe", True, True))  # E: numpy.ndarray[Any, numpy.dtype[{float64}]]
 
 # byteswap
-reveal_type(nd.byteswap())  # E: numpy.ndarray
-reveal_type(nd.byteswap(True))  # E: numpy.ndarray
+reveal_type(nd.byteswap())  # E: numpy.ndarray[Any, numpy.dtype[{int_}]]
+reveal_type(nd.byteswap(True))  # E: numpy.ndarray[Any, numpy.dtype[{int_}]]
 
 # copy
-reveal_type(nd.copy())  # E: numpy.ndarray
-reveal_type(nd.copy("C"))  # E: numpy.ndarray
+reveal_type(nd.copy())  # E: numpy.ndarray[Any, numpy.dtype[{int_}]]
+reveal_type(nd.copy("C"))  # E: numpy.ndarray[Any, numpy.dtype[{int_}]]
 
-# view
-class SubArray(np.ndarray):
-    pass
-
-
-reveal_type(nd.view())  # E: numpy.ndarray
-reveal_type(nd.view(np.int64))  # E: numpy.ndarray
-# replace `Any` with `numpy.matrix` when `matrix` will be added to stubs
-reveal_type(nd.view(np.int64, np.matrix))  # E: Any
-reveal_type(nd.view(np.int64, SubArray))  # E: SubArray
+reveal_type(nd.view())  # E: numpy.ndarray[Any, numpy.dtype[{int_}]]
+reveal_type(nd.view(np.float64))  # E: numpy.ndarray[Any, numpy.dtype[{float64}]]
+reveal_type(nd.view(float))  # E: numpy.ndarray[Any, numpy.dtype[Any]]
+reveal_type(nd.view(np.float64, np.matrix))  # E: numpy.matrix[Any, Any]
 
 # getfield
-reveal_type(nd.getfield("float"))  # E: numpy.ndarray
-reveal_type(nd.getfield(float))  # E: numpy.ndarray
-reveal_type(nd.getfield(float, 8))  # E: numpy.ndarray
+reveal_type(nd.getfield("float"))  # E: numpy.ndarray[Any, numpy.dtype[Any]]
+reveal_type(nd.getfield(float))  # E: numpy.ndarray[Any, numpy.dtype[Any]]
+reveal_type(nd.getfield(np.float64))  # E: numpy.ndarray[Any, numpy.dtype[{float64}]]
+reveal_type(nd.getfield(np.float64, 8))  # E: numpy.ndarray[Any, numpy.dtype[{float64}]]
 
 # setflags does not return a value
 # fill does not return a value

numpy/typing/tests/data/reveal/scalars.py

@@ -144,3 +144,15 @@
 if sys.version_info >= (3, 9):
     reveal_type(f8.__ceil__())  # E: int
     reveal_type(f8.__floor__())  # E: int
+
+reveal_type(i8.astype(float))  # E: Any
+reveal_type(i8.astype(np.float64))  # E: {float64}
+
+reveal_type(i8.view())  # E: {int64}
+reveal_type(i8.view(np.float64))  # E: {float64}
+reveal_type(i8.view(float))  # E: Any
+reveal_type(i8.view(np.float64, np.ndarray))  # E: {float64}
+
+reveal_type(i8.getfield(float))  # E: Any
+reveal_type(i8.getfield(np.float64))  # E: {float64}
+reveal_type(i8.getfield(np.float64, 8))  # E: {float64}