[3.10] bpo-46707: Avoid potential exponential backtracking in some syntax errors (GH-31241). (GH-31242)
(cherry picked from commit b71dc71905ab674ccaa4a56230d17a28f61c325c)
Co-authored-by: Pablo Galindo Salgado <Pablogsal@gmail.com>
diff --git a/Grammar/python.gram b/Grammar/python.gram
index f730658..69c20bd 100644
--- a/Grammar/python.gram
+++ b/Grammar/python.gram
@@ -863,13 +863,15 @@
RAISE_SYNTAX_ERROR_KNOWN_RANGE(a, b, "invalid syntax. Perhaps you forgot a comma?") }
| a=disjunction 'if' b=disjunction !('else'|':') { RAISE_SYNTAX_ERROR_KNOWN_RANGE(a, b, "expected 'else' after 'if' expression") }
+invalid_left_assignment_prefixes(memo): list|tuple|genexp|'True'|'None'|'False'
+
invalid_named_expression:
| a=expression ':=' expression {
RAISE_SYNTAX_ERROR_KNOWN_LOCATION(
a, "cannot use assignment expressions with %s", _PyPegen_get_expr_name(a)) }
| a=NAME '=' b=bitwise_or !('='|':=') {
p->in_raw_rule ? NULL : RAISE_SYNTAX_ERROR_KNOWN_RANGE(a, b, "invalid syntax. Maybe you meant '==' or ':=' instead of '='?") }
- | !(list|tuple|genexp|'True'|'None'|'False') a=bitwise_or b='=' bitwise_or !('='|':=') {
+ | !invalid_left_assignment_prefixes a=bitwise_or b='=' bitwise_or !('='|':=') {
p->in_raw_rule ? NULL : RAISE_SYNTAX_ERROR_KNOWN_LOCATION(a, "cannot assign to %s here. Maybe you meant '==' instead of '='?",
_PyPegen_get_expr_name(a)) }