From a3e5320835f34bcc534b407f036878afcc0bc735 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Dani=C3=ABl=20van=20Noord?=
 <13665637+DanielNoord@users.noreply.github.com>
Date: Thu, 15 Sep 2022 11:09:04 +0200
Subject: [PATCH] Use ``WeakKeyDictionary`` in ``decorators.cached``

---
 ChangeLog             | 3 +++
 astroid/decorators.py | 5 ++++-
 2 files changed, 7 insertions(+), 1 deletion(-)

diff --git a/ChangeLog b/ChangeLog
index 142a9a7e0b..4c4ceb9c56 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -17,7 +17,10 @@ What's New in astroid 2.12.10?
 ==============================
 Release date: TBA
 
+* ``decorators.cached`` now uses a ``WeakKeyDictionary`` to allow the garbave collector
+  to remove entries when possible.
 
+  Refs #1780
 
 What's New in astroid 2.12.9?
 =============================
diff --git a/astroid/decorators.py b/astroid/decorators.py
index c4f44dcd27..0a0ac48672 100644
--- a/astroid/decorators.py
+++ b/astroid/decorators.py
@@ -10,6 +10,7 @@
 import inspect
 import sys
 import warnings
+import weakref
 from collections.abc import Callable
 from typing import TypeVar
 
@@ -32,8 +33,10 @@
 def cached(func, instance, args, kwargs):
     """Simple decorator to cache result of method calls without args."""
     cache = getattr(instance, "__cache", None)
+    # Use a WeakKeyDictionary to allow the garbage collector to remove entries
+    # that only exist in the cache.
     if cache is None:
-        instance.__cache = cache = {}
+        instance.__cache = cache = weakref.WeakKeyDictionary()
     try:
         return cache[func]
     except KeyError: