MAINT: changed np.generic arguments to positional-only (#16583)

Closes https://github.com/numpy/numpy/issues/16577.

Make the arguments of `np.generic` constructors positional-only.

Also fix the constructor of`np.bytes_`: encoding is only
supported when supplied a string. The opposite holds for
`np.str_`.

3 files changed, 41 insertions, 23 deletions

diff --git a/numpy/__init__.pyi b/numpy/__init__.pyi
index 4aab0bbfa..f9218391e 100644
--- a/numpy/__init__.pyi
+++ b/numpy/__init__.pyi
@@ -387,18 +387,18 @@ class _real_generic(generic):  # type: ignore
 class number(generic): ...  # type: ignore
 
 class bool_(_real_generic):
-    def __init__(self, value: object = ...) -> None: ...
+    def __init__(self, __value: object = ...) -> None: ...
 
 class object_(generic):
-    def __init__(self, value: object = ...) -> None: ...
+    def __init__(self, __value: object = ...) -> None: ...
 
 class datetime64:
     @overload
     def __init__(
-        self, _data: Union[datetime64, str, dt.datetime] = ..., _format: str = ...
+        self, __value: Union[datetime64, str, dt.datetime] = ..., __format: str = ...
     ) -> None: ...
     @overload
-    def __init__(self, _data: int, _format: str) -> None: ...
+    def __init__(self, __value: int, __format: str) -> None: ...
     def __add__(self, other: Union[timedelta64, int]) -> datetime64: ...
     def __sub__(self, other: Union[timedelta64, datetime64, int]) -> timedelta64: ...
 
@@ -406,19 +406,19 @@ class integer(number, _real_generic): ...  # type: ignore
 class signedinteger(integer): ...  # type: ignore
 
 class int8(signedinteger):
-    def __init__(self, value: SupportsInt = ...) -> None: ...
+    def __init__(self, __value: SupportsInt = ...) -> None: ...
 
 class int16(signedinteger):
-    def __init__(self, value: SupportsInt = ...) -> None: ...
+    def __init__(self, __value: SupportsInt = ...) -> None: ...
 
 class int32(signedinteger):
-    def __init__(self, value: SupportsInt = ...) -> None: ...
+    def __init__(self, __value: SupportsInt = ...) -> None: ...
 
 class int64(signedinteger):
-    def __init__(self, value: SupportsInt = ...) -> None: ...
+    def __init__(self, __value: SupportsInt = ...) -> None: ...
 
 class timedelta64(signedinteger):
-    def __init__(self, _data: Any = ..., _format: str = ...) -> None: ...
+    def __init__(self, __value: Any = ..., __format: str = ...) -> None: ...
     @overload
     def __add__(self, other: Union[timedelta64, int]) -> timedelta64: ...
     @overload
@@ -438,34 +438,34 @@ class timedelta64(signedinteger):
 class unsignedinteger(integer): ...  # type: ignore
 
 class uint8(unsignedinteger):
-    def __init__(self, value: SupportsInt = ...) -> None: ...
+    def __init__(self, __value: SupportsInt = ...) -> None: ...
 
 class uint16(unsignedinteger):
-    def __init__(self, value: SupportsInt = ...) -> None: ...
+    def __init__(self, __value: SupportsInt = ...) -> None: ...
 
 class uint32(unsignedinteger):
-    def __init__(self, value: SupportsInt = ...) -> None: ...
+    def __init__(self, __value: SupportsInt = ...) -> None: ...
 
 class uint64(unsignedinteger):
-    def __init__(self, value: SupportsInt = ...) -> None: ...
+    def __init__(self, __value: SupportsInt = ...) -> None: ...
 
 class inexact(number): ...  # type: ignore
 class floating(inexact, _real_generic): ...  # type: ignore
 
 class float16(floating):
-    def __init__(self, value: SupportsFloat = ...) -> None: ...
+    def __init__(self, __value: SupportsFloat = ...) -> None: ...
 
 class float32(floating):
-    def __init__(self, value: SupportsFloat = ...) -> None: ...
+    def __init__(self, __value: SupportsFloat = ...) -> None: ...
 
 class float64(floating):
-    def __init__(self, value: SupportsFloat = ...) -> None: ...
+    def __init__(self, __value: SupportsFloat = ...) -> None: ...
 
 class complexfloating(inexact): ...  # type: ignore
 
 class complex64(complexfloating):
     def __init__(
-        self, value: Union[SupportsInt, SupportsFloat, SupportsComplex] = ...
+        self, __value: Union[SupportsInt, SupportsFloat, SupportsComplex] = ...
     ) -> None: ...
     @property
     def real(self) -> float32: ...
@@ -474,7 +474,7 @@ class complex64(complexfloating):
 
 class complex128(complexfloating):
     def __init__(
-        self, value: Union[SupportsInt, SupportsFloat, SupportsComplex] = ...
+        self, __value: Union[SupportsInt, SupportsFloat, SupportsComplex] = ...
     ) -> None: ...
     @property
     def real(self) -> float64: ...
@@ -484,24 +484,24 @@ class complex128(complexfloating):
 class flexible(_real_generic): ...  # type: ignore
 
 class void(flexible):
-    def __init__(self, value: Union[int, integer, bool_, bytes, bytes_]): ...
+    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: ...
+    def __init__(self, __value: object = ...) -> None: ...
     @overload
     def __init__(
-        self, value: object, encoding: str = ..., errors: str = ...
+        self, __value: Union[str, str_], encoding: str = ..., errors: str = ...
     ) -> None: ...
 
 class str_(character):
     @overload
-    def __init__(self, value: object = ...) -> None: ...
+    def __init__(self, __value: object = ...) -> None: ...
     @overload
     def __init__(
-        self, value: object, encoding: str = ..., errors: str = ...
+        self, __value: Union[bytes, bytes_], encoding: str = ..., errors: str = ...
     ) -> None: ...
 
 # TODO(alan): Platform dependent types
diff --git a/numpy/tests/typing/fail/scalars.py b/numpy/tests/typing/fail/scalars.py
index 0dfc55124..5d7221895 100644
--- a/numpy/tests/typing/fail/scalars.py
+++ b/numpy/tests/typing/fail/scalars.py
@@ -65,3 +65,17 @@ 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
+
+np.float64(value=0.0)  # E: Unexpected keyword argument
+np.int64(value=0)  # E: Unexpected keyword argument
+np.uint64(value=0)  # E: Unexpected keyword argument
+np.complex128(value=0.0j)  # E: Unexpected keyword argument
+np.str_(value='bob')  # E: No overload variant
+np.bytes_(value=b'test')  # E: No overload variant
+np.void(value=b'test')  # E: Unexpected keyword argument
+np.bool_(value=True)  # E: Unexpected keyword argument
+np.datetime64(value="2019")  # E: No overload variant
+np.timedelta64(value=0)  # E: Unexpected keyword argument
+
+np.bytes_(b"hello", encoding='utf-8')  # E: No overload variant
+np.str_("hello", encoding='utf-8')  # E: No overload variant
diff --git a/numpy/tests/typing/pass/scalars.py b/numpy/tests/typing/pass/scalars.py
index bd055673b..7de182626 100644
--- a/numpy/tests/typing/pass/scalars.py
+++ b/numpy/tests/typing/pass/scalars.py
@@ -34,7 +34,11 @@ np.float32(16)
 np.float64(3.0)
 
 np.bytes_(b"hello")
+np.bytes_("hello", 'utf-8')
+np.bytes_("hello", encoding='utf-8')
 np.str_("hello")
+np.str_(b"hello", 'utf-8')
+np.str_(b"hello", encoding='utf-8')
 
 # Protocols
 float(np.int8(4))