From 0f01212d4bb6408d37bd33ff5cd665dbc00c9e0a Mon Sep 17 00:00:00 2001
From: Apoorv Darshan <ad13dtu@gmail.com>
Date: Thu, 9 Jul 2026 19:32:09 +0530
Subject: [PATCH] Treat named expression call arguments as positional

parso raised a false 'SyntaxError: positional argument follows keyword
argument' for valid calls such as f(a := 1, b). A named expression
argument (name := value) was misclassified as a keyword argument because
_ArglistRule treated every non-*/** argument as a keyword, so it set
kw_only and flagged any following positional argument.

Detect the ':=' operator and treat such arguments as positional. They no
longer set kw_only, and they now correctly raise when they themselves
follow a keyword argument or keyword-argument unpacking, matching CPython.

Fixes #212.
---
 AUTHORS.txt                |  1 +
 CHANGELOG.rst              |  3 +++
 parso/python/errors.py     | 12 ++++++++++++
 test/failing_examples.py   |  2 ++
 test/test_python_errors.py |  6 ++++++
 5 files changed, 24 insertions(+)

diff --git a/AUTHORS.txt b/AUTHORS.txt
index 9737530..9853dff 100644
--- a/AUTHORS.txt
+++ b/AUTHORS.txt
@@ -53,6 +53,7 @@ Simon Ruggier (@sruggier)
 Tim Gates (@timgates42) <tim.gates@iress.com>
 Batuhan Taskaya (@isidentical) <isidentical@gmail.com>
 Jocelyn Boullier (@Kazy) <jocelyn@boullier.bzh>
+Apoorv Darshan (@apoorvdarshan) <ad13dtu@gmail.com>
 
 
 Note: (@user) means a github user name.
diff --git a/CHANGELOG.rst b/CHANGELOG.rst
index a4811fb..811e095 100644
--- a/CHANGELOG.rst
+++ b/CHANGELOG.rst
@@ -6,6 +6,9 @@ Changelog
 Unreleased
 ++++++++++
 
+- Fix a false ``SyntaxError`` for named expressions used as positional
+  arguments in a call, e.g. ``f(a := 1, b)``
+
 0.8.7 (2026-05-02)
 ++++++++++++++++++
 
diff --git a/parso/python/errors.py b/parso/python/errors.py
index 09c5047..79945b2 100644
--- a/parso/python/errors.py
+++ b/parso/python/errors.py
@@ -933,6 +933,18 @@ def is_issue(self, node):
                             self.add_issue(argument, message=message)
                     else:
                         kw_unpacking_only = True
+                elif argument.children[1] == ':=':
+                    # f(a := 1) is a named expression, i.e. a positional
+                    # argument, not a keyword argument.
+                    if kw_unpacking_only:
+                        # f(**x, a := 1)
+                        message = "positional argument follows " \
+                                  "keyword argument unpacking"
+                        self.add_issue(argument, message=message)
+                    elif kw_only:
+                        # f(x=2, a := 1)
+                        message = "positional argument follows keyword argument"
+                        self.add_issue(argument, message=message)
                 else:  # Is a keyword argument.
                     kw_only = True
                     if first.type == 'name':
diff --git a/test/failing_examples.py b/test/failing_examples.py
index a555fde..1e1e745 100644
--- a/test/failing_examples.py
+++ b/test/failing_examples.py
@@ -49,6 +49,8 @@ def build_nested(code, depth, base='def f():\n'):
     'f(x=1, x=2)',
     'f(**x, y)',
     'f(x=2, y)',
+    'f(x=2, a := 1)',
+    'f(**x, a := 1)',
     'f(**x, *y)',
     'f(**x, y=3, z)',
     # augassign
diff --git a/test/test_python_errors.py b/test/test_python_errors.py
index 0c89016..11ec97a 100644
--- a/test/test_python_errors.py
+++ b/test/test_python_errors.py
@@ -362,6 +362,12 @@ def test_valid_fstrings(code):
         'a[(b:=0)]',
         'a[(b:=0, c:=0)]',
         'a[(b:=0):1:2]',
+        'f(a := 1, b)',
+        'f(a := 1, b=2)',
+        'f(a := 1, *b)',
+        'f(a := 1, **b)',
+        'f(b, a := 1)',
+        'f(*b, a := 1)',
     ]
 )
 def test_valid_namedexpr(code):