WIP: Mapping.{get,pop} can return default type (#223)

* Mapping.{get,pop} can return default type

* Mapping values are covariant

Author: tharvik

stdlib/2.7/__builtin__.pyi

@@ -8,7 +8,7 @@ from typing import (
     Sequence, Mapping, Tuple, List, Any, Dict, Callable, Generic, Set,
     AbstractSet, Sized, Reversible, SupportsInt, SupportsFloat, SupportsAbs,
     SupportsRound, IO, BinaryIO, Union, AnyStr, MutableSequence, MutableMapping,
-    MutableSet
+    MutableSet, Optional,
 )
 from abc import abstractmethod, ABCMeta
 
@@ -534,8 +534,14 @@ class dict(MutableMapping[_KT, _VT], Generic[_KT, _VT]):
     def has_key(self, k: _KT) -> bool: ...
     def clear(self) -> None: ...
     def copy(self) -> Dict[_KT, _VT]: ...
-    def get(self, k: _KT, default: _VT = None) -> _VT: ...
-    def pop(self, k: _KT, default: _VT = ...) -> _VT: ...
+    @overload
+    def get(self, k: _KT) -> Optional[_VT]: ...
+    @overload
+    def get(self, k: _KT, default: _T) -> Union[_VT, _T]: ...
+    @overload
+    def pop(self, k: _KT) -> _VT: ...
+    @overload
+    def pop(self, k: _KT, default: _T) -> Union[_VT, _T]: ...
     def popitem(self) -> Tuple[_KT, _VT]: ...
     def setdefault(self, k: _KT, default: _VT = ...) -> _VT: ...
     @overload

stdlib/2.7/typing.pyi

@@ -157,17 +157,20 @@ class MutableSet(AbstractSet[_T], Generic[_T]):
     def __ixor__(self, s: AbstractSet[_S]) -> MutableSet[Union[_T, _S]]: ...
     def __isub__(self, s: AbstractSet[Any]) -> MutableSet[_T]: ...
 
-class Mapping(Sized, Iterable[_KT], Container[_KT], Generic[_KT, _VT]):
+class Mapping(Sized, Iterable[_KT], Container[_KT], Generic[_KT, _VT_co]):
     @abstractmethod
-    def __getitem__(self, k: _KT) -> _VT: ...
+    def __getitem__(self, k: _KT) -> _VT_co: ...
     # Mixin methods
-    def get(self, k: _KT, default: _VT = ...) -> _VT: ...
+    @overload
+    def get(self, k: _KT) -> Optional[_VT_co]: ...
+    @overload
+    def get(self, k: _KT, default: _T) -> Union[_VT_co, _T]: ...
     def keys(self) -> list[_KT]: ...
-    def values(self) -> list[_VT]: ...
-    def items(self) -> list[Tuple[_KT, _VT]]: ...
+    def values(self) -> list[_VT_co]: ...
+    def items(self) -> list[Tuple[_KT, _VT_co]]: ...
     def iterkeys(self) -> Iterator[_KT]: ...
-    def itervalues(self) -> Iterator[_VT]: ...
-    def iteritems(self) -> Iterator[Tuple[_KT, _VT]]: ...
+    def itervalues(self) -> Iterator[_VT_co]: ...
+    def iteritems(self) -> Iterator[Tuple[_KT, _VT_co]]: ...
     def __contains__(self, o: object) -> bool: ...
 
 class MutableMapping(Mapping[_KT, _VT], Generic[_KT, _VT]):
@@ -177,7 +180,10 @@ class MutableMapping(Mapping[_KT, _VT], Generic[_KT, _VT]):
     def __delitem__(self, v: _KT) -> None: ...
 
     def clear(self) -> None: ...
-    def pop(self, k: _KT, default: _VT = ...) -> _VT: ...
+    @overload
+    def pop(self, k: _KT) -> _VT: ...
+    @overload
+    def pop(self, k: _KT, default: _T) -> Union[_VT, _T]: ...
     def popitem(self) -> Tuple[_KT, _VT]: ...
     def setdefault(self, k: _KT, default: _VT = ...) -> _VT: ...
     @overload

stdlib/3/builtins.pyi

@@ -4,7 +4,7 @@ from typing import (
     TypeVar, Iterator, Iterable, overload,
     Sequence, MutableSequence, Mapping, MutableMapping, Tuple, List, Any, Dict, Callable, Generic,
     Set, AbstractSet, MutableSet, Sized, Reversible, SupportsInt, SupportsFloat, SupportsBytes,
-    SupportsAbs, SupportsRound, IO, Union, ItemsView, KeysView, ValuesView, ByteString
+    SupportsAbs, SupportsRound, IO, Union, ItemsView, KeysView, ValuesView, ByteString, Optional,
 )
 from abc import abstractmethod, ABCMeta
 
@@ -507,8 +507,14 @@ class dict(MutableMapping[_KT, _VT], Generic[_KT, _VT]):
     def __init__(self, iterable: Iterable[Tuple[_KT, _VT]], **kwargs: _VT) -> None: ...
     def clear(self) -> None: ...
     def copy(self) -> Dict[_KT, _VT]: ...
-    def get(self, k: _KT, default: _VT = None) -> _VT: ...
-    def pop(self, k: _KT, default: _VT = None) -> _VT: ...
+    @overload
+    def get(self, k: _KT) -> Optional[_VT]: ...
+    @overload
+    def get(self, k: _KT, default: _T) -> Union[_VT, _T]: ...
+    @overload
+    def pop(self, k: _KT) -> _VT: ...
+    @overload
+    def pop(self, k: _KT, default: _T) -> Union[_VT, _T]: ...
     def popitem(self) -> Tuple[_KT, _VT]: ...
     def setdefault(self, k: _KT, default: _VT = None) -> _VT: ...
     @overload

stdlib/3/typing.pyi

@@ -215,16 +215,19 @@ class ValuesView(MappingView, Iterable[_VT_co], Generic[_VT_co]):
 
 # TODO: ContextManager (only if contextlib.AbstractContextManager exists)
 
-class Mapping(Iterable[_KT], Container[_KT], Sized, Generic[_KT, _VT]):
+class Mapping(Iterable[_KT], Container[_KT], Sized, Generic[_KT, _VT_co]):
     # TODO: Value type should be covariant, but currently we can't give a good signature for
     #   get if this is the case.
     @abstractmethod
-    def __getitem__(self, k: _KT) -> _VT: ...
+    def __getitem__(self, k: _KT) -> _VT_co: ...
     # Mixin methods
-    def get(self, k: _KT, default: _VT = ...) -> _VT: ...
-    def items(self) -> AbstractSet[Tuple[_KT, _VT]]: ...
+    @overload
+    def get(self, k: _KT) -> Optional[_VT_co]: ...
+    @overload
+    def get(self, k: _KT, default: _T) -> Union[_VT_co, _T]: ...
+    def items(self) -> AbstractSet[Tuple[_KT, _VT_co]]: ...
     def keys(self) -> AbstractSet[_KT]: ...
-    def values(self) -> ValuesView[_VT]: ...
+    def values(self) -> ValuesView[_VT_co]: ...
     def __contains__(self, o: object) -> bool: ...
 
 class MutableMapping(Mapping[_KT, _VT], Generic[_KT, _VT]):
@@ -234,7 +237,10 @@ class MutableMapping(Mapping[_KT, _VT], Generic[_KT, _VT]):
     def __delitem__(self, v: _KT) -> None: ...
 
     def clear(self) -> None: ...
-    def pop(self, k: _KT, default: _VT = ...) -> _VT: ...
+    @overload
+    def pop(self, k: _KT) -> _VT: ...
+    @overload
+    def pop(self, k: _KT, default: _T) -> Union[_VT, _T]: ...
     def popitem(self) -> Tuple[_KT, _VT]: ...
     def setdefault(self, k: _KT, default: _VT = ...) -> _VT: ...
     # 'update' used to take a Union, but using overloading is better.