Fix some issues with __round__ (#2907)

In python 3, add an overload for there being no digits argument
and make it return int.

In python 2, __round__ doesn't exist and SupportsRound doesn't exist
in the typing module. Use SupportsFloat for python 2 round().

Remove decimal's __round__ overload that takes None, since it doesn't exist

stdlib/2/__builtin__.pyi

@@ -5,7 +5,7 @@ from typing import (
     TypeVar, Iterator, Iterable, NoReturn, overload, Container,
     Sequence, MutableSequence, Mapping, MutableMapping, Tuple, List, Any, Dict, Callable, Generic,
     Set, AbstractSet, FrozenSet, MutableSet, Sized, Reversible, SupportsInt, SupportsFloat, SupportsAbs,
-    SupportsComplex, SupportsRound, IO, BinaryIO, Union,
+    SupportsComplex, IO, BinaryIO, Union,
     ItemsView, KeysView, ValuesView, ByteString, Optional, AnyStr, Type, Text,
     Protocol,
 )
@@ -15,7 +15,7 @@ from types import TracebackType, CodeType
 import sys
 
 if sys.version_info >= (3,):
-    from typing import SupportsBytes
+    from typing import SupportsBytes, SupportsRound
 
 _T = TypeVar('_T')
 _T_co = TypeVar('_T_co', covariant=True)
@@ -1370,9 +1370,9 @@ else:
     @overload
     def round(number: float, ndigits: int) -> float: ...
     @overload
-    def round(number: SupportsRound[_T]) -> _T: ...
+    def round(number: SupportsFloat) -> float: ...
     @overload
-    def round(number: SupportsRound[_T], ndigits: int) -> _T: ...
+    def round(number: SupportsFloat, ndigits: int) -> float: ...
 def setattr(object: Any, name: Text, value: Any) -> None: ...
 if sys.version_info >= (3,):
     def sorted(iterable: Iterable[_T], *,

stdlib/2/typing.pyi

@@ -86,11 +86,6 @@ class SupportsAbs(Protocol[_T_co]):
     @abstractmethod
     def __abs__(self) -> _T_co: ...
 
-@runtime
-class SupportsRound(Protocol[_T_co]):
-    @abstractmethod
-    def __round__(self, ndigits: int = ...) -> _T_co: ...
-
 @runtime
 class Reversible(Protocol[_T_co]):
     @abstractmethod

stdlib/2and3/builtins.pyi

@@ -5,7 +5,7 @@ from typing import (
     TypeVar, Iterator, Iterable, NoReturn, overload, Container,
     Sequence, MutableSequence, Mapping, MutableMapping, Tuple, List, Any, Dict, Callable, Generic,
     Set, AbstractSet, FrozenSet, MutableSet, Sized, Reversible, SupportsInt, SupportsFloat, SupportsAbs,
-    SupportsComplex, SupportsRound, IO, BinaryIO, Union,
+    SupportsComplex, IO, BinaryIO, Union,
     ItemsView, KeysView, ValuesView, ByteString, Optional, AnyStr, Type, Text,
     Protocol,
 )
@@ -15,7 +15,7 @@ from types import TracebackType, CodeType
 import sys
 
 if sys.version_info >= (3,):
-    from typing import SupportsBytes
+    from typing import SupportsBytes, SupportsRound
 
 _T = TypeVar('_T')
 _T_co = TypeVar('_T_co', covariant=True)
@@ -1370,9 +1370,9 @@ else:
     @overload
     def round(number: float, ndigits: int) -> float: ...
     @overload
-    def round(number: SupportsRound[_T]) -> _T: ...
+    def round(number: SupportsFloat) -> float: ...
     @overload
-    def round(number: SupportsRound[_T], ndigits: int) -> _T: ...
+    def round(number: SupportsFloat, ndigits: int) -> float: ...
 def setattr(object: Any, name: Text, value: Any) -> None: ...
 if sys.version_info >= (3,):
     def sorted(iterable: Iterable[_T], *,

stdlib/2and3/decimal.pyi

@@ -124,8 +124,6 @@ class Decimal(object):
         @overload
         def __round__(self) -> int: ...
         @overload
-        def __round__(self, ndigits: None) -> int: ...
-        @overload
         def __round__(self, ndigits: int) -> Decimal: ...
         def __floor__(self) -> int: ...
         def __ceil__(self) -> int: ...

stdlib/3/typing.pyi

@@ -95,8 +95,12 @@ class SupportsAbs(Protocol[_T_co]):
 
 @runtime
 class SupportsRound(Protocol[_T_co]):
+    @overload
     @abstractmethod
-    def __round__(self, ndigits: int = ...) -> _T_co: ...
+    def __round__(self) -> int: ...
+    @overload
+    @abstractmethod
+    def __round__(self, ndigits: int) -> _T_co: ...
 
 @runtime
 class Reversible(Protocol[_T_co]):