[Python-checkins] [3.14] gh-133516: Raise `ValueError` when constants `True`, `False` or `None` are used as an identifier after NFKC normalization (GH-133523) (#133596)

[pablogsal]

https://github.com/python/cpython/commit/54c3aa1597ef3b7a967a27a5ea8577cefeb59769
commit: 54c3aa1597ef3b7a967a27a5ea8577cefeb59769
branch: 3.14
author: Miss Islington (bot) <31488909+miss-isling...@users.noreply.github.com>
committer: pablogsal <pablog...@gmail.com>
date: 2025-05-07T22:26:06Z
summary:

[3.14] gh-133516: Raise `ValueError` when constants `True`, `False` or `None` 
are used as an identifier after NFKC normalization (GH-133523) (#133596)

files:
A 
Misc/NEWS.d/next/Core_and_Builtins/2025-05-06-15-01-41.gh-issue-133516.RqWVf2.rst
M Lib/test/test_ast/test_ast.py
M Parser/pegen.c

diff --git a/Lib/test/test_ast/test_ast.py b/Lib/test/test_ast/test_ast.py
index 09cf3186e05cc1..02628868db008c 100644
--- a/Lib/test/test_ast/test_ast.py
+++ b/Lib/test/test_ast/test_ast.py
@@ -821,6 +821,17 @@ def test_constant_as_name(self):
             with self.assertRaisesRegex(ValueError, f"identifier field can't 
represent '{constant}' constant"):
                 compile(expr, "<test>", "eval")
 
+    def test_constant_as_unicode_name(self):
+        constants = [
+            ("True", b"Tru\xe1\xb5\x89"),
+            ("False", b"Fal\xc5\xbfe"),
+            ("None", b"N\xc2\xbane"),
+        ]
+        for constant in constants:
+            with self.assertRaisesRegex(ValueError,
+                f"identifier field can't represent '{constant[0]}' constant"):
+                ast.parse(constant[1], mode="eval")
+
     def test_precedence_enum(self):
         class _Precedence(enum.IntEnum):
             """Precedence table that originated from python grammar."""
diff --git 
a/Misc/NEWS.d/next/Core_and_Builtins/2025-05-06-15-01-41.gh-issue-133516.RqWVf2.rst
 
b/Misc/NEWS.d/next/Core_and_Builtins/2025-05-06-15-01-41.gh-issue-133516.RqWVf2.rst
new file mode 100644
index 00000000000000..b93ba11f93252b
--- /dev/null
+++ 
b/Misc/NEWS.d/next/Core_and_Builtins/2025-05-06-15-01-41.gh-issue-133516.RqWVf2.rst
@@ -0,0 +1,2 @@
+Raise :exc:`ValueError` when constants ``True``, ``False`` or ``None`` are
+used as an identifier after NFKC normalization.
diff --git a/Parser/pegen.c b/Parser/pegen.c
index 3efeba78450d1a..81aad47010181c 100644
--- a/Parser/pegen.c
+++ b/Parser/pegen.c
@@ -549,6 +549,21 @@ _PyPegen_new_identifier(Parser *p, const char *n)
         }
         id = id2;
     }
+    static const char * const forbidden[] = {
+        "None",
+        "True",
+        "False",
+        NULL
+    };
+    for (int i = 0; forbidden[i] != NULL; i++) {
+        if (_PyUnicode_EqualToASCIIString(id, forbidden[i])) {
+            PyErr_Format(PyExc_ValueError,
+                         "identifier field can't represent '%s' constant",
+                         forbidden[i]);
+            Py_DECREF(id);
+            goto error;
+        }
+    }
     PyInterpreterState *interp = _PyInterpreterState_GET();
     _PyUnicode_InternImmortal(interp, &id);
     if (_PyArena_AddPyObject(p->arena, id) < 0)

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