MAINT: Fix issue 77: Don't allow initializing generic #80

This pull request addresses the issues raised in
#77: constructors were
previously available for ``np.generic`` and a number of its
subclasses, many of which could not actually be instantiated.

Author: Bas van Beek

Diff for: numpy-stubs/__init__.pyi

@@ -1,6 +1,7 @@
 import builtins
 import sys
 import datetime as dt
+from abc import abstractmethod, ABCMeta
 
 from numpy.core._internal import _ctypes
 from numpy.typing import ArrayLike, DtypeLike, _Shape, _ShapeLike
@@ -359,22 +360,33 @@ class ndarray(_ArrayOrScalarCommon, Iterable, Sized, Container):
     def __contains__(self, key) -> bool: ...
     def __index__(self) -> int: ...
 
+# NOTE: while `np.generic` is not technically an instance of `ABCMeta`,
+# the `@abstractmethod` decorator is herein used to (forcefully) deny
+# the creation of `np.generic` instances.
+# The `# type: ignore` comments are necessary to silence mypy errors regarding
+# the missing `ABCMeta` metaclass.
+
+# See https://github.com/numpy/numpy-stubs/pull/80 for more details.
+
 class generic(_ArrayOrScalarCommon):
-    def __init__(self, value: Any = ...) -> None: ...
+    @abstractmethod
+    def __init__(self, *args: Any, **kwargs: Any) -> None: ...
     @property
     def base(self) -> None: ...
 
-class _real_generic(generic):
+class _real_generic(generic):  # type: ignore
     @property
     def real(self: _ArraySelf) -> _ArraySelf: ...
     @property
     def imag(self: _ArraySelf) -> _ArraySelf: ...
 
-class number(generic):
-    def __init__(self, value: Union[SupportsInt, SupportsFloat] = ...) -> None: ...
+class number(generic): ...  # type: ignore
+
+class bool_(_real_generic):
+    def __init__(self, value: object = ...) -> None: ...
 
-class bool_(_real_generic): ...
-class object_(generic): ...
+class object_(generic):
+    def __init__(self, value: object = ...) -> None: ...
 
 class datetime64:
     @overload
@@ -386,8 +398,8 @@ class datetime64:
     def __add__(self, other: Union[timedelta64, int]) -> datetime64: ...
     def __sub__(self, other: Union[timedelta64, datetime64, int]) -> timedelta64: ...
 
-class integer(number, _real_generic): ...
-class signedinteger(integer): ...
+class integer(number, _real_generic): ...  # type: ignore
+class signedinteger(integer): ...  # type: ignore
 
 class int8(signedinteger):
     def __init__(self, value: SupportsInt = ...) -> None: ...
@@ -419,7 +431,7 @@ class timedelta64(signedinteger):
     def __truediv__(self, other: float) -> timedelta64: ...
     def __mod__(self, other: timedelta64) -> timedelta64: ...
 
-class unsignedinteger(integer): ...
+class unsignedinteger(integer): ...  # type: ignore
 
 class uint8(unsignedinteger):
     def __init__(self, value: SupportsInt = ...) -> None: ...
@@ -433,34 +445,60 @@ class uint32(unsignedinteger):
 class uint64(unsignedinteger):
     def __init__(self, value: SupportsInt = ...) -> None: ...
 
-class inexact(number): ...
-class floating(inexact, _real_generic): ...
-class float16(floating): ...
-class float32(floating): ...
-class float64(floating): ...
+class inexact(number): ...  # type: ignore
+class floating(inexact, _real_generic): ...  # type: ignore
 
-class complexfloating(inexact):
-    def __init__(
-        self, value: Union[SupportsInt, SupportsFloat, SupportsComplex, complex] = ...
-    ) -> None: ...
+class float16(floating):
+    def __init__(self, value: SupportsFloat = ...) -> None: ...
+
+class float32(floating):
+    def __init__(self, value: SupportsFloat = ...) -> None: ...
+
+class float64(floating):
+    def __init__(self, value: SupportsFloat = ...) -> None: ...
+
+class complexfloating(inexact): ...  # type: ignore
 
 class complex64(complexfloating):
+    def __init__(
+        self, value: Union[SupportsInt, SupportsFloat, SupportsComplex] = ...
+    ) -> None: ...
     @property
     def real(self) -> float32: ...
     @property
     def imag(self) -> float32: ...
 
 class complex128(complexfloating):
+    def __init__(
+        self, value: Union[SupportsInt, SupportsFloat, SupportsComplex] = ...
+    ) -> None: ...
     @property
     def real(self) -> float64: ...
     @property
     def imag(self) -> float64: ...
 
-class flexible(_real_generic): ...
-class void(flexible): ...
-class character(_real_generic): ...
-class bytes_(character): ...
-class str_(character): ...
+class flexible(_real_generic): ...  # type: ignore
+
+class void(flexible):
+    def __init__(self, value: Union[int, integer, bool_, bytes, bytes_]): ...
+
+class character(_real_generic): ...  # type: ignore
+
+class bytes_(character):
+    @overload
+    def __init__(self, value: object = ...) -> None: ...
+    @overload
+    def __init__(
+        self, value: object, encoding: str = ..., errors: str = ...
+    ) -> None: ...
+
+class str_(character):
+    @overload
+    def __init__(self, value: object = ...) -> None: ...
+    @overload
+    def __init__(
+        self, value: object, encoding: str = ..., errors: str = ...
+    ) -> None: ...
 
 # TODO(alan): Platform dependent types
 # longcomplex, longdouble, longfloat

Diff for: tests/fail/scalars.py

@@ -52,3 +52,16 @@ def __float__(self):
 np.uint16(A())  # E: incompatible type
 np.uint32(A())  # E: incompatible type
 np.uint64(A())  # E: incompatible type
+
+np.void("test")  # E: incompatible type
+
+np.generic(1)  # E: Cannot instantiate abstract class
+np.number(1)  # E: Cannot instantiate abstract class
+np.integer(1)  # E: Cannot instantiate abstract class
+np.signedinteger(1)  # E: Cannot instantiate abstract class
+np.unsignedinteger(1)  # E: Cannot instantiate abstract class
+np.inexact(1)  # E: Cannot instantiate abstract class
+np.floating(1)  # E: Cannot instantiate abstract class
+np.complexfloating(1)  # E: Cannot instantiate abstract class
+np.character("test")  # E: Cannot instantiate abstract class
+np.flexible(b"test")  # E: Cannot instantiate abstract class

Diff for: tests/pass/ndarray_conversion.py

@@ -1,3 +1,4 @@
+import os
 import tempfile
 
 import numpy as np
@@ -28,15 +29,16 @@
 nd.tobytes(None)
 
 # tofile
-with tempfile.NamedTemporaryFile(suffix=".txt") as tmp:
-    nd.tofile(tmp.name)
-    nd.tofile(tmp.name, "")
-    nd.tofile(tmp.name, sep="")
+if os.name != "nt":
+    with tempfile.NamedTemporaryFile(suffix=".txt") as tmp:
+        nd.tofile(tmp.name)
+        nd.tofile(tmp.name, "")
+        nd.tofile(tmp.name, sep="")
 
-    nd.tofile(tmp.name, "", "%s")
-    nd.tofile(tmp.name, format="%s")
+        nd.tofile(tmp.name, "", "%s")
+        nd.tofile(tmp.name, format="%s")
 
-    nd.tofile(tmp)
+        nd.tofile(tmp)
 
 # dump is pretty simple
 # dumps is pretty simple

Diff for: tests/pass/scalars.py

@@ -19,6 +19,8 @@ def __float__(self):
 
 np.complex64(3j)
 np.complex64(C())
+np.complex128(3j)
+np.complex128(C())
 
 np.int8(4)
 np.int16(3.4)
@@ -77,3 +79,10 @@ def __float__(self):
 td_64 / 1.0
 td_64 / td_64
 td_64 % td_64
+
+np.void(1)
+np.void(np.int64(1))
+np.void(True)
+np.void(np.bool_(True))
+np.void(b"test")
+np.void(np.bytes_("test"))