allow disjoint types in Mapping.get MutableMapping.pop, dict.get, dic…

stdlib/@tests/test_cases/builtins/check_dict.py

@@ -1,7 +1,7 @@
 from __future__ import annotations
 
 import os
-from typing import Any, Dict, Generic, Iterable, Mapping, TypeVar, Union
+from typing import Any, Dict, Generic, Iterable, Literal, Mapping, TypeVar, Union
 from typing_extensions import Self, assert_type
 
 ###################################################################
@@ -74,35 +74,51 @@ def test_iterable_tuple_overload(x: Iterable[tuple[int, str]]) -> dict[int, str]
 assert_type(d_any.get("key"), Union[Any, None])
 assert_type(d_any.get("key", None), Union[Any, None])
 assert_type(d_any.get("key", any_value), Any)
-assert_type(d_any.get("key", str_value), Any)
-assert_type(d_any.get("key", int_value), Any)
+assert_type(d_any.get("key", str_value), Union[Any, str])
+assert_type(d_any.get("key", int_value), Union[Any, int])
 
 assert_type(d_str["key"], str)
 assert_type(d_str.get("key"), Union[str, None])
 assert_type(d_str.get("key", None), Union[str, None])
 # Pyright has str instead of Any here
-assert_type(d_str.get("key", any_value), Any)  # pyright: ignore[reportAssertTypeFailure]
+assert_type(d_str.get("key", any_value), Union[str, Any])
 assert_type(d_str.get("key", str_value), str)
 assert_type(d_str.get("key", int_value), Union[str, int])
 
 # Now with context!
 result: str
 result = d_any["key"]
-result = d_any.get("key")  # type: ignore[assignment]
-result = d_any.get("key", None)  # type: ignore[assignment]
+# FIXME: https://github.com/python/mypy/issues/20576 prevents using ignore[assignment] here
+result = d_any.get("key")  # type: ignore
+# FIXME: https://github.com/python/mypy/issues/20576 prevents using ignore[assignment] here
+result = d_any.get("key", None)  # type: ignore
 result = d_any.get("key", any_value)
 result = d_any.get("key", str_value)
-result = d_any.get("key", int_value)
+# FIXME: https://github.com/python/mypy/issues/20576 prevents using ignore[assignment] here
+result = d_any.get("key", int_value)  # type: ignore
 
 result = d_str["key"]
-result = d_str.get("key")  # type: ignore[assignment]
-result = d_str.get("key", None)  # type: ignore[assignment]
-# Pyright has str | None here, see https://github.com/microsoft/pyright/discussions/9570
-result = d_str.get("key", any_value)  # pyright: ignore[reportAssignmentType]
+# FIXME: https://github.com/python/mypy/issues/20576 prevents using ignore[assignment] here
+result = d_str.get("key")  # type: ignore
+# FIXME: https://github.com/python/mypy/issues/20576 prevents using ignore[assignment] here
+result = d_str.get("key", None)  # type: ignore
+result = d_str.get("key", any_value)
 result = d_str.get("key", str_value)
 result = d_str.get("key", int_value)  # type: ignore[arg-type]
 
 
+def test_get_literal(d: dict[Literal["foo", "bar"], int], dynamic_key: str) -> None:
+    # Note: annotations also allow using keys of a disjoint type (e.g., int),
+    #   linters / type checkers are free to issue warnings in such cases.
+    #   statically, a .get(arg) is superfluous if the intersection of the
+    #   dict key type and the argument type is empty.
+    #   So we only test a case with non-empty intersection here.
+
+    # check that dict wth Literal keys can get/pop a string key.
+    d.get(dynamic_key)
+    d.pop(dynamic_key)
+
+
 # Return values also make things weird
 
 # Pyright doesn't have a version of no-any-return,
@@ -112,7 +128,8 @@ def test_iterable_tuple_overload(x: Iterable[tuple[int, str]]) -> dict[int, str]
 
 
 def test2() -> str:
-    return d_any.get("key")  # type: ignore[return-value]
+    # FIXME: https://github.com/python/mypy/issues/20576 prevents using ignore[return-value] here
+    return d_any.get("key")  # type: ignore
 
 
 # def test3() -> str:
@@ -136,15 +153,18 @@ def test7() -> str:
 
 
 def test8() -> str:
-    return d_str.get("key")  # type: ignore[return-value]
+    # FIXME: https://github.com/python/mypy/issues/20576 prevents using ignore[return-value] here
+    return d_str.get("key")  # type: ignore
 
 
 def test9() -> str:
-    return d_str.get("key", None)  # type: ignore[return-value]
+    # FIXME: https://github.com/python/mypy/issues/20576 prevents using ignore[return-value] here
+    return d_str.get("key", None)  # type: ignore
 
 
 def test10() -> str:
-    return d_str.get("key", any_value)  # type: ignore[no-any-return]
+    # OK, return is Union[str, Any]
+    return d_str.get("key", any_value)
 
 
 def test11() -> str:

stdlib/builtins.pyi

@@ -79,6 +79,7 @@ if sys.version_info >= (3, 14):
     from _typeshed import AnnotateFunc
 
 _T = TypeVar("_T")
+_N = TypeVar("_N", default=None)
 _I = TypeVar("_I", default=int)
 _T_co = TypeVar("_T_co", covariant=True)
 _T_contra = TypeVar("_T_contra", contravariant=True)
@@ -1218,19 +1219,8 @@ class dict(MutableMapping[_KT, _VT]):
     @classmethod
     @overload
     def fromkeys(cls, iterable: Iterable[_T], value: _S, /) -> dict[_T, _S]: ...
-    # Positional-only in dict, but not in MutableMapping
-    @overload  # type: ignore[override]
-    def get(self, key: _KT, default: None = None, /) -> _VT | None: ...
-    @overload
-    def get(self, key: _KT, default: _VT, /) -> _VT: ...
-    @overload
-    def get(self, key: _KT, default: _T, /) -> _VT | _T: ...
-    @overload
-    def pop(self, key: _KT, /) -> _VT: ...
-    @overload
-    def pop(self, key: _KT, default: _VT, /) -> _VT: ...
-    @overload
-    def pop(self, key: _KT, default: _T, /) -> _VT | _T: ...
+    def get(self, key: object, default: _N = None, /) -> _VT | _N: ...
+    def pop(self, key: object, default: _N = None, /) -> _VT | _N: ...
     def __len__(self) -> int: ...
     def __getitem__(self, key: _KT, /) -> _VT: ...
     def __setitem__(self, key: _KT, value: _VT, /) -> None: ...

stdlib/collections/__init__.pyi

@@ -105,12 +105,15 @@ class UserDict(MutableMapping[_KT, _VT]):
     @overload
     def __ior__(self, other: Iterable[tuple[_KT, _VT]]) -> Self: ...
     if sys.version_info >= (3, 12):
+        # UserDict allows key and default as keyword arguments
         @overload
-        def get(self, key: _KT, default: None = None) -> _VT | None: ...
+        def get(self, key: object, default: _T) -> _VT | _T: ...
         @overload
-        def get(self, key: _KT, default: _VT) -> _VT: ...
+        def get(self, key: object, default: None = None) -> _VT | None: ...
         @overload
-        def get(self, key: _KT, default: _T) -> _VT | _T: ...
+        def pop(self, key: object, default: _T) -> _VT | _T: ...
+        @overload  # type: ignore[override]
+        def pop(self, key: object, default: None = None) -> _VT | None: ...
 
 class UserList(MutableSequence[_T]):
     data: list[_T]
@@ -382,11 +385,9 @@ class OrderedDict(dict[_KT, _VT]):
     def setdefault(self, key: _KT, default: _VT) -> _VT: ...
     # Same as dict.pop, but accepts keyword arguments
     @overload
-    def pop(self, key: _KT) -> _VT: ...
-    @overload
-    def pop(self, key: _KT, default: _VT) -> _VT: ...
-    @overload
-    def pop(self, key: _KT, default: _T) -> _VT | _T: ...
+    def pop(self, key: object, default: _T) -> _VT | _T: ...
+    @overload  # type: ignore[override]
+    def pop(self, key: object, default: None = None) -> _VT | None: ...
     def __eq__(self, value: object, /) -> bool: ...
     @overload
     def __or__(self, value: dict[_KT, _VT], /) -> Self: ...

stdlib/importlib/metadata/__init__.pyi

@@ -165,11 +165,9 @@ if sys.version_info >= (3, 10) and sys.version_info < (3, 12):
     class Deprecated(Generic[_KT, _VT]):
         def __getitem__(self, name: _KT) -> _VT: ...
         @overload
-        def get(self, name: _KT, default: None = None) -> _VT | None: ...
+        def get(self, key: object, default: _T) -> _VT | _T: ...
         @overload
-        def get(self, name: _KT, default: _VT) -> _VT: ...
-        @overload
-        def get(self, name: _KT, default: _T) -> _VT | _T: ...
+        def get(self, key: object, default: None = None) -> _VT | None: ...
         def __iter__(self) -> Iterator[_KT]: ...
         def __contains__(self, *args: object) -> bool: ...
         def keys(self) -> dict_keys[_KT, _VT]: ...