Check all arguments for unparenthesized generator expressions

Previously only the first argument on the argument list checked
against the generator expressions, now all argumnets are controlled.

parso/python/errors.py

@@ -779,12 +779,6 @@ class _ArglistRule(SyntaxRule):
             return "Generator expression must be parenthesized"
 
     def is_issue(self, node):
-        first_arg = node.children[0]
-        if first_arg.type == 'argument' \
-                and first_arg.children[1].type in _COMP_FOR_TYPES:
-            # e.g. foo(x for x in [], b)
-            return len(node.children) >= 2
-        else:
         arg_set = set()
         kw_only = False
         kw_unpacking_only = False
@@ -806,6 +800,9 @@ class _ArglistRule(SyntaxRule):
 
             if argument.type == 'argument':
                 first = argument.children[0]
+                if argument.children[1].type in _COMP_FOR_TYPES and len(node.children) >= 2:
+                    # a(a, b for b in c)
+                    return True
                 if first in ('*', '**'):
                     if first == '*':
                         if kw_unpacking_only:

test/test_python_errors.py

@@ -375,3 +375,15 @@ def test_repeated_kwarg():
         _get_error_list("f(q=1, q=2)", version="3.9")[0].message
         == "SyntaxError: keyword argument repeated: q"
     )
+
+
+@pytest.mark.parametrize(
+    'source', [
+        'a(a for a in b,)'
+        'a(a for a in b, a)',
+        'a(a, a for a in b)',
+        'a(a, b, a for a in b, c, d)',
+    ]
+)
+def test_unparenthesized_genexp(source):
+    assert _get_error_list(source)