From a02cb474f9c097c83cd444a47e9fb5f99b4aaf45 Mon Sep 17 00:00:00 2001
From: Ethan Furman <ethan@stoneleaf.us>
Date: Wed, 21 Apr 2021 10:20:44 -0700
Subject: bpo-38659: [Enum] add _simple_enum decorator (GH-25497)

add:

* `_simple_enum` decorator to transform a normal class into an enum
* `_test_simple_enum` function to compare
* `_old_convert_` to enable checking `_convert_` generated enums

`_simple_enum` takes a normal class and converts it into an enum:

    @simple_enum(Enum)
    class Color:
        RED = 1
        GREEN = 2
        BLUE = 3

`_old_convert_` works much like` _convert_` does, using the original logic:

    # in a test file
    import socket, enum
    CheckedAddressFamily = enum._old_convert_(
            enum.IntEnum, 'AddressFamily', 'socket',
            lambda C: C.isupper() and C.startswith('AF_'),
            source=_socket,
            )

`_test_simple_enum` takes a traditional enum and a simple enum and
compares the two:

    # in the REPL or the same module as Color
    class CheckedColor(Enum):
        RED = 1
        GREEN = 2
        BLUE = 3

    _test_simple_enum(CheckedColor, Color)

    _test_simple_enum(CheckedAddressFamily, socket.AddressFamily)

Any important differences will raise a TypeError
---
 Lib/ast.py | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

(limited to 'Lib/ast.py')

diff --git a/Lib/ast.py b/Lib/ast.py
index e46ab43d5c..703f68ace6 100644
--- a/Lib/ast.py
+++ b/Lib/ast.py
@@ -27,7 +27,7 @@
 import sys
 from _ast import *
 from contextlib import contextmanager, nullcontext
-from enum import IntEnum, auto
+from enum import IntEnum, auto, _simple_enum
 
 
 def parse(source, filename='<unknown>', mode='exec', *,
@@ -636,7 +636,8 @@ class Param(expr_context):
 # We unparse those infinities to INFSTR.
 _INFSTR = "1e" + repr(sys.float_info.max_10_exp + 1)
 
-class _Precedence(IntEnum):
+@_simple_enum(IntEnum)
+class _Precedence:
     """Precedence table that originated from python grammar."""
 
     TUPLE = auto()
-- 
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