pegen: further improve del error messages

Outputs specialised error messages for more cases, better caret
placement

Author: hauntsaninja

Grammar/python.gram

@@ -122,9 +122,7 @@ yield_stmt[stmt_ty]: y=yield_expr { _Py_Expr(y, EXTRA) }
 
 assert_stmt[stmt_ty]: 'assert' a=expression b=[',' z=expression { z }] { _Py_Assert(a, b, EXTRA) }
 
-del_stmt[stmt_ty]:
-    | 'del' a=del_targets { _Py_Delete(a, EXTRA) }
-    | invalid_delete
+del_stmt[stmt_ty]: 'del' a=del_targets { _Py_Delete(a, EXTRA) }
 
 import_stmt[stmt_ty]: import_name | import_from
 import_name[stmt_ty]: 'import' a=dotted_as_names { _Py_Import(a, EXTRA) }
@@ -589,6 +587,7 @@ del_target[expr_ty] (memo):
     | a=t_primary '.' b=NAME !t_lookahead { _Py_Attribute(a, b->v.Name.id, Del, EXTRA) }
     | a=t_primary '[' b=slices ']' !t_lookahead { _Py_Subscript(a, b, Del, EXTRA) }
     | del_t_atom
+    | invalid_del_target
 del_t_atom[expr_ty]:
     | a=NAME !t_lookahead { _PyPegen_set_expr_context(p, a, Del) }
     | '(' a=del_target ')' { _PyPegen_set_expr_context(p, a, Del) }
@@ -651,6 +650,6 @@ invalid_lambda_star_etc:
 invalid_double_type_comments:
     | TYPE_COMMENT NEWLINE TYPE_COMMENT NEWLINE INDENT {
         RAISE_SYNTAX_ERROR("Cannot have two type comments on def") }
-invalid_delete:
-    | 'del' a=star_expressions {
-        RAISE_SYNTAX_ERROR_NO_COL_OFFSET("cannot delete %s", _PyPegen_get_expr_name(a)) }
+invalid_del_target:
+    | a=star_expression {
+        RAISE_SYNTAX_ERROR("cannot delete %s", _PyPegen_get_expr_name(a)) }

Lib/test/test_syntax.py

@@ -681,6 +681,7 @@ def test_assign_del(self):
         self._check_error("del f()", "delete")
         self._check_error("del 1", "delete")
         self._check_error("del *x", "delete")
+        self._check_error("del x, f()", "delete")
 
     def test_global_param_err_first(self):
         source = """if 1: