bpo-44368: Ensure we don't raise incorrect custom syntax errors with soft keywords (GH-26630)

(cherry picked from commit 457ce60fc70f1c9290023f46fb82b6a490dff32e)

Co-authored-by: Pablo Galindo <Pablogsal@gmail.com>

2 files changed, 20 insertions, 1 deletions

diff --git a/Lib/test/test_exceptions.py b/Lib/test/test_exceptions.py
index b242c082f8..9cb5466a67 100644
--- a/Lib/test/test_exceptions.py
+++ b/Lib/test/test_exceptions.py
@@ -215,6 +215,7 @@ class ExceptionTests(unittest.TestCase):
         check('[\nfile\nfor str(file)\nin\n[]\n]', 3, 5)
         check('[file for\n str(file) in []]', 2, 2)
         check("ages = {'Alice'=22, 'Bob'=23}", 1, 16)
+        check('match ...:\n    case {**rest, "key": value}:\n        ...', 2, 19)
 
         # Errors thrown by compile.c
         check('class foo:return 1', 1, 11)
diff --git a/Lib/test/test_syntax.py b/Lib/test/test_syntax.py
index 5d3ce4cd9f..72e4ab15c8 100644
--- a/Lib/test/test_syntax.py
+++ b/Lib/test/test_syntax.py
@@ -267,7 +267,7 @@ Traceback (most recent call last):
 SyntaxError: invalid syntax. Perhaps you forgot a comma?
 
 # Make sure soft keywords constructs don't raise specialized
-# errors regarding missing commas
+# errors regarding missing commas or other spezialiced errors
 
 >>> match x:
 ...     y = 3
@@ -280,6 +280,24 @@ SyntaxError: invalid syntax
 Traceback (most recent call last):
 SyntaxError: invalid syntax
 
+>>> match x:
+...     case $:
+...        ...
+Traceback (most recent call last):
+SyntaxError: invalid syntax
+
+>>> match ...:
+...     case {**rest, "key": value}:
+...        ...
+Traceback (most recent call last):
+SyntaxError: invalid syntax
+
+>>> match ...:
+...     case {**_}:
+...        ...
+Traceback (most recent call last):
+SyntaxError: invalid syntax
+
 From compiler_complex_args():
 
 >>> def f(None=1):