From bea2795be2c08dde3830f987830414f3f12bc1eb Mon Sep 17 00:00:00 2001
From: Shantanu <12621235+hauntsaninja@users.noreply.github.com>
Date: Thu, 29 Feb 2024 03:09:09 -0800
Subject: [PATCH] gh-115881: Document feature_version limitations (#115980)

---
 Doc/library/ast.rst | 15 +++++++++------
 1 file changed, 9 insertions(+), 6 deletions(-)

diff --git a/Doc/library/ast.rst b/Doc/library/ast.rst
index d629393f023c8a..5ed6eb63c0fb62 100644
--- a/Doc/library/ast.rst
+++ b/Doc/library/ast.rst
@@ -2183,12 +2183,15 @@ and classes for traversing abstract syntax trees:
    modified to correspond to :pep:`484` "signature type comments",
    e.g. ``(str, int) -> List[str]``.
 
-   Also, setting ``feature_version`` to a tuple ``(major, minor)``
-   will attempt to parse using that Python version's grammar.
-   Currently ``major`` must equal to ``3``.  For example, setting
-   ``feature_version=(3, 4)`` will allow the use of ``async`` and
-   ``await`` as variable names.  The lowest supported version is
-   ``(3, 7)``; the highest is ``sys.version_info[0:2]``.
+   Setting ``feature_version`` to a tuple ``(major, minor)`` will result in
+   a "best-effort" attempt to parse using that Python version's grammar.
+   For example, setting ``feature_version=(3, 9)`` will attempt to disallow
+   parsing of :keyword:`match` statements.
+   Currently ``major`` must equal to ``3``. The lowest supported version is
+   ``(3, 7)`` (and this may increase in future Python versions);
+   the highest is ``sys.version_info[0:2]``. "Best-effort" attempt means there
+   is no guarantee that the parse (or success of the parse) is the same as
+   when run on the Python version corresponding to ``feature_version``.
 
    If source contains a null character ('\0'), :exc:`ValueError` is raised.