gh-109120: Fix handle of incorrect star expressions

Grammar/python.gram

@@ -1013,6 +1013,7 @@ kwargs[asdl_seq*]:
 starred_expression[expr_ty]:
     | invalid_starred_expression
     | '*' a=expression { _PyAST_Starred(a, Load, EXTRA) }
+    | '*' { RAISE_SYNTAX_ERROR("Invalid star expression") }
 
 kwarg_or_starred[KeywordOrStarred*]:
     | invalid_kwarg
@@ -1133,8 +1134,8 @@ func_type_comment[Token*]:
 
 # From here on, there are rules for invalid syntax with specialised error messages
 invalid_arguments:
-    | ((','.(starred_expression | ( assignment_expression | expression !':=') !'=')+ ',' kwargs) | kwargs) ',' b='*' {
-        RAISE_SYNTAX_ERROR_KNOWN_LOCATION(b, "iterable argument unpacking follows keyword argument unpacking") }
+    | ((','.(starred_expression | ( assignment_expression | expression !':=') !'=')+ ',' kwargs) | kwargs) a=',' ','.(starred_expression !'=')+ {
+        RAISE_SYNTAX_ERROR_STARTING_FROM(a, "iterable argument unpacking follows keyword argument unpacking") }
     | a=expression b=for_if_clauses ',' [args | expression for_if_clauses] {
         RAISE_SYNTAX_ERROR_KNOWN_RANGE(a, _PyPegen_get_last_comprehension_item(PyPegen_last_item(b, comprehension_ty)), "Generator expression must be parenthesized") }
     | a=NAME b='=' expression for_if_clauses {
@@ -1396,6 +1397,7 @@ invalid_kvpair:
     | expression a=':' &('}'|',') {RAISE_SYNTAX_ERROR_KNOWN_LOCATION(a, "expression expected after dictionary key and ':'") }
 invalid_starred_expression:
     | a='*' expression '=' b=expression { RAISE_SYNTAX_ERROR_KNOWN_RANGE(a, b, "cannot assign to iterable argument unpacking") }
+
 invalid_replacement_field:
     | '{' a='=' { RAISE_SYNTAX_ERROR_KNOWN_LOCATION(a, "f-string: valid expression required before '='") }
     | '{' a='!' { RAISE_SYNTAX_ERROR_KNOWN_LOCATION(a, "f-string: valid expression required before '!'") }

Lib/test/test_syntax.py

@@ -1911,22 +1911,22 @@
     >>> A[*(1:2)]
     Traceback (most recent call last):
         ...
-    SyntaxError: invalid syntax
+    SyntaxError: Invalid star expression
     >>> A[*(1:2)] = 1
     Traceback (most recent call last):
         ...
-    SyntaxError: invalid syntax
+    SyntaxError: Invalid star expression
     >>> del A[*(1:2)]
     Traceback (most recent call last):
         ...
-    SyntaxError: invalid syntax
+    SyntaxError: Invalid star expression
 
 A[*:] and A[:*]
 
     >>> A[*:]
     Traceback (most recent call last):
         ...
-    SyntaxError: invalid syntax
+    SyntaxError: Invalid star expression
     >>> A[:*]
     Traceback (most recent call last):
         ...
@@ -1937,7 +1937,7 @@
     >>> A[*]
     Traceback (most recent call last):
         ...
-    SyntaxError: invalid syntax
+    SyntaxError: Invalid star expression
 
 A[**]
 
@@ -2081,11 +2081,23 @@ def f(x: *b)
 
     >>> f(**x, *)
     Traceback (most recent call last):
-    SyntaxError: iterable argument unpacking follows keyword argument unpacking
+    SyntaxError: Invalid star expression
 
     >>> f(x, *:)
     Traceback (most recent call last):
-    SyntaxError: invalid syntax
+    SyntaxError: Invalid star expression
+
+    >>> f(x, *)
+    Traceback (most recent call last):
+    SyntaxError: Invalid star expression
+
+    >>> f(x = 5, *)
+    Traceback (most recent call last):
+    SyntaxError: Invalid star expression
+
+    >>> f(x = 5, *:)
+    Traceback (most recent call last):
+    SyntaxError: Invalid star expression
 """
 
 import re

Misc/NEWS.d/next/Core and Builtins/2024-04-02-06-16-49.gh-issue-109120.X485oN.rst

@@ -0,0 +1,2 @@
+Added handle of incorrect star expressions, e.g ``f(3, *)``. Patch by
+Grigoryev Semyon