From dc957c7d74108c32debc5c582fbbf60d6de12a41 Mon Sep 17 00:00:00 2001
From: Jelle Zijlstra <jelle.zijlstra@gmail.com>
Date: Wed, 17 May 2023 06:05:42 -0700
Subject: [PATCH] gh-104572: Improve error messages for invalid constructs in
 PEP 695 contexts (#104573)

---
 Lib/test/test_syntax.py                       | 62 +++++++++++++++++++
 ...-05-16-19-17-48.gh-issue-104572.eBZQYS.rst |  2 +
 Python/symtable.c                             |  8 +--
 3 files changed, 68 insertions(+), 4 deletions(-)
 create mode 100644 Misc/NEWS.d/next/Core and Builtins/2023-05-16-19-17-48.gh-issue-104572.eBZQYS.rst

diff --git a/Lib/test/test_syntax.py b/Lib/test/test_syntax.py
index f959bbb44007026..477879db2fd493a 100644
--- a/Lib/test/test_syntax.py
+++ b/Lib/test/test_syntax.py
@@ -1877,6 +1877,68 @@ def f(x: *b)
         ^^^^^^^^^^^
    SyntaxError: bytes can only contain ASCII literal characters
 
+Invalid expressions in type scopes:
+
+   >>> type A[T: (x:=3)] = int
+   Traceback (most recent call last):
+      ...
+   SyntaxError: named expression cannot be used within a TypeVar bound
+
+   >>> type A[T: (yield 3)] = int
+   Traceback (most recent call last):
+      ...
+   SyntaxError: yield expression cannot be used within a TypeVar bound
+
+   >>> type A[T: (await 3)] = int
+   Traceback (most recent call last):
+      ...
+   SyntaxError: await expression cannot be used within a TypeVar bound
+
+   >>> type A[T: (yield from [])] = int
+   Traceback (most recent call last):
+      ...
+   SyntaxError: yield expression cannot be used within a TypeVar bound
+
+   >>> type A = (x := 3)
+   Traceback (most recent call last):
+      ...
+   SyntaxError: named expression cannot be used within a type alias
+
+   >>> type A = (yield 3)
+   Traceback (most recent call last):
+      ...
+   SyntaxError: yield expression cannot be used within a type alias
+
+   >>> type A = (await 3)
+   Traceback (most recent call last):
+      ...
+   SyntaxError: await expression cannot be used within a type alias
+
+   >>> type A = (yield from [])
+   Traceback (most recent call last):
+      ...
+   SyntaxError: yield expression cannot be used within a type alias
+
+   >>> class A[T]((x := 3)): ...
+   Traceback (most recent call last):
+      ...
+   SyntaxError: named expression cannot be used within the definition of a generic
+
+   >>> class A[T]((yield 3)): ...
+   Traceback (most recent call last):
+      ...
+   SyntaxError: yield expression cannot be used within the definition of a generic
+
+   >>> class A[T]((await 3)): ...
+   Traceback (most recent call last):
+      ...
+   SyntaxError: await expression cannot be used within the definition of a generic
+
+   >>> class A[T]((yield from [])): ...
+   Traceback (most recent call last):
+      ...
+   SyntaxError: yield expression cannot be used within the definition of a generic
+
 """
 
 import re
diff --git a/Misc/NEWS.d/next/Core and Builtins/2023-05-16-19-17-48.gh-issue-104572.eBZQYS.rst b/Misc/NEWS.d/next/Core and Builtins/2023-05-16-19-17-48.gh-issue-104572.eBZQYS.rst
new file mode 100644
index 000000000000000..25bad8aa6e3e6f9
--- /dev/null
+++ b/Misc/NEWS.d/next/Core and Builtins/2023-05-16-19-17-48.gh-issue-104572.eBZQYS.rst	
@@ -0,0 +1,2 @@
+Improve syntax error message for invalid constructs in :pep:`695` contexts
+and in annotations when ``from __future__ import annotations`` is active.
diff --git a/Python/symtable.c b/Python/symtable.c
index 3451f6c7bffb6d0..f896f7cbe3382b8 100644
--- a/Python/symtable.c
+++ b/Python/symtable.c
@@ -45,16 +45,16 @@
 "assignment expression cannot be used in a comprehension iterable expression"
 
 #define ANNOTATION_NOT_ALLOWED \
-"'%s' can not be used within an annotation"
+"%s cannot be used within an annotation"
 
 #define TYPEVAR_BOUND_NOT_ALLOWED \
-"'%s' can not be used within a TypeVar bound"
+"%s cannot be used within a TypeVar bound"
 
 #define TYPEALIAS_NOT_ALLOWED \
-"'%s' can not be used within a type alias"
+"%s cannot be used within a type alias"
 
 #define TYPEPARAM_NOT_ALLOWED \
-"'%s' can not be used within the definition of a generic"
+"%s cannot be used within the definition of a generic"
 
 #define DUPLICATE_TYPE_PARAM \
 "duplicate type parameter '%U'"