From 6035080b3feda1dfe2ea999ad880b4b80f337d0c Mon Sep 17 00:00:00 2001
From: Pablo Galindo <pablogsal@gmail.com>
Date: Wed, 30 Dec 2020 21:22:43 +0000
Subject: [PATCH] bpo-40631: Improve error message when deleting single starred
 element

---
 Grammar/python.gram     |  2 ++
 Lib/test/test_syntax.py |  5 ++++-
 Parser/parser.c         | 32 +++++++++++++++++++++++++++++++-
 3 files changed, 37 insertions(+), 2 deletions(-)

diff --git a/Grammar/python.gram b/Grammar/python.gram
index 05ddce520fbae1e..59243696f2562af 100644
--- a/Grammar/python.gram
+++ b/Grammar/python.gram
@@ -724,6 +724,8 @@ invalid_for_target:
         RAISE_SYNTAX_ERROR_INVALID_TARGET(FOR_TARGETS, a) }
 
 invalid_group:
+    | '(' a=star_expression ')' {
+        RAISE_SYNTAX_ERROR_INVALID_TARGET(DEL_TARGETS, a) }
     | '(' a=starred_expression ')' {
         RAISE_SYNTAX_ERROR_KNOWN_LOCATION(a, "can't use starred expression here") }
 invalid_import_from_targets:
diff --git a/Lib/test/test_syntax.py b/Lib/test/test_syntax.py
index c8d191df4cc495c..8988b816f5643bf 100644
--- a/Lib/test/test_syntax.py
+++ b/Lib/test/test_syntax.py
@@ -789,6 +789,7 @@ def _check_error(self, code, errtext,
         try:
             compile(code, filename, mode)
         except SyntaxError as err:
+            print(err)
             if subclass and not isinstance(err, subclass):
                 self.fail("SyntaxError is not a %s" % subclass.__name__)
             mo = re.search(errtext, str(err))
@@ -821,7 +822,9 @@ def test_assign_del(self):
         self._check_error("del (1, 2)", "delete literal")
         self._check_error("del None", "delete None")
         self._check_error("del *x", "delete starred")
-        self._check_error("del (*x)", "use starred expression")
+        self._check_error("del (*x)", "delete starred")
+        self._check_error("del (*x, *y)", "delete starred")
+        self._check_error("del (x, *y)", "delete starred")
         self._check_error("del (*x,)", "delete starred")
         self._check_error("del [*x,]", "delete starred")
         self._check_error("del f()", "delete function call")
diff --git a/Parser/parser.c b/Parser/parser.c
index f7794e715b918f0..9e3f91def750bb1 100644
--- a/Parser/parser.c
+++ b/Parser/parser.c
@@ -15777,7 +15777,7 @@ invalid_for_target_rule(Parser *p)
     return _res;
 }
 
-// invalid_group: '(' starred_expression ')'
+// invalid_group: '(' star_expression ')' | '(' starred_expression ')'
 static void *
 invalid_group_rule(Parser *p)
 {
@@ -15788,6 +15788,36 @@ invalid_group_rule(Parser *p)
     }
     void * _res = NULL;
     int _mark = p->mark;
+    { // '(' star_expression ')'
+        if (p->error_indicator) {
+            D(p->level--);
+            return NULL;
+        }
+        D(fprintf(stderr, "%*c> invalid_group[%d-%d]: %s\n", p->level, ' ', _mark, p->mark, "'(' star_expression ')'"));
+        Token * _literal;
+        Token * _literal_1;
+        expr_ty a;
+        if (
+            (_literal = _PyPegen_expect_token(p, 7))  // token='('
+            &&
+            (a = star_expression_rule(p))  // star_expression
+            &&
+            (_literal_1 = _PyPegen_expect_token(p, 8))  // token=')'
+        )
+        {
+            D(fprintf(stderr, "%*c+ invalid_group[%d-%d]: %s succeeded!\n", p->level, ' ', _mark, p->mark, "'(' star_expression ')'"));
+            _res = RAISE_SYNTAX_ERROR_INVALID_TARGET ( DEL_TARGETS , a );
+            if (_res == NULL && PyErr_Occurred()) {
+                p->error_indicator = 1;
+                D(p->level--);
+                return NULL;
+            }
+            goto done;
+        }
+        p->mark = _mark;
+        D(fprintf(stderr, "%*c%s invalid_group[%d-%d]: %s failed!\n", p->level, ' ',
+                  p->error_indicator ? "ERROR!" : "-", _mark, p->mark, "'(' star_expression ')'"));
+    }
     { // '(' starred_expression ')'
         if (p->error_indicator) {
             D(p->level--);