From 240e3d800418388e79ea7c7836d33177ed6d2e54 Mon Sep 17 00:00:00 2001
From: Max Muoto <maxmuoto@gmail.com>
Date: Sat, 20 Jul 2024 15:37:30 -0500
Subject: [PATCH] Correct `MappingProxyType` for 3.8+ (#12369)

Co-authored-by: Shantanu <12621235+hauntsaninja@users.noreply.github.com>
---
 stdlib/@tests/stubtest_allowlists/py313.txt |  4 +++-
 stdlib/@tests/test_cases/check_types.py     | 14 ++++++++++++++
 stdlib/types.pyi                            |  4 ++++
 3 files changed, 21 insertions(+), 1 deletion(-)

diff --git a/stdlib/@tests/stubtest_allowlists/py313.txt b/stdlib/@tests/stubtest_allowlists/py313.txt
index 7d6b8870f..73b0b35fa 100644
--- a/stdlib/@tests/stubtest_allowlists/py313.txt
+++ b/stdlib/@tests/stubtest_allowlists/py313.txt
@@ -50,7 +50,6 @@ tkinter.Misc.tk_busy_hold
 tkinter.Misc.tk_busy_status
 tkinter.Text.count
 tkinter.Wm.wm_attributes
-types.MappingProxyType.get
 
 # ======================================
 # Pre-existing errors from Python <=3.12
@@ -199,3 +198,6 @@ codecs.namereplace_errors
 codecs.replace_errors
 codecs.strict_errors
 codecs.xmlcharrefreplace_errors
+
+# To match `dict`, we lie about the runtime, but use overloads to match the correct behavior
+types.MappingProxyType.get
diff --git a/stdlib/@tests/test_cases/check_types.py b/stdlib/@tests/test_cases/check_types.py
index 3654ca864..7dcf31923 100644
--- a/stdlib/@tests/test_cases/check_types.py
+++ b/stdlib/@tests/test_cases/check_types.py
@@ -1,6 +1,8 @@
 import sys
 import types
 from collections import UserDict
+from typing import Union
+from typing_extensions import assert_type
 
 # test `types.SimpleNamespace`
 
@@ -25,3 +27,15 @@ types.SimpleNamespace({1: 2})  # type: ignore
 types.SimpleNamespace([[1, 2]])  # type: ignore
 types.SimpleNamespace(UserDict({1: 2}))  # type: ignore
 types.SimpleNamespace([[[], 2]])  # type: ignore
+
+# test: `types.MappingProxyType`
+mp = types.MappingProxyType({1: 2, 3: 4})
+mp.get("x")  # type: ignore
+item = mp.get(1)
+assert_type(item, Union[int, None])
+item_2 = mp.get(2, 0)
+assert_type(item_2, int)
+item_3 = mp.get(3, "default")
+assert_type(item_3, Union[int, str])
+# Default isn't accepted as a keyword argument.
+mp.get(4, default="default")  # type: ignore
diff --git a/stdlib/types.pyi b/stdlib/types.pyi
index a569b55ef..1e3eacd9f 100644
--- a/stdlib/types.pyi
+++ b/stdlib/types.pyi
@@ -304,6 +304,10 @@ class MappingProxyType(Mapping[_KT, _VT_co]):
     def keys(self) -> KeysView[_KT]: ...
     def values(self) -> ValuesView[_VT_co]: ...
     def items(self) -> ItemsView[_KT, _VT_co]: ...
+    @overload
+    def get(self, key: _KT, /) -> _VT_co | None: ...  # type: ignore[override]
+    @overload
+    def get(self, key: _KT, default: _VT_co | _T2, /) -> _VT_co | _T2: ...  # type: ignore[override]
     if sys.version_info >= (3, 9):
         def __class_getitem__(cls, item: Any, /) -> GenericAlias: ...
         def __reversed__(self) -> Iterator[_KT]: ...