[Python-checkins] [3.9] bpo-42123: Run the parser two times and only enable invalid rules on the second run (GH-22111) (GH-23011)

lysnikolaou webhook-mailer at python.org
Tue Oct 27 20:14:19 EDT 2020

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---

https://github.com/python/cpython/commit/24a7c298d47658295673dc04d1b6d59f2b200a7c
commit: 24a7c298d47658295673dc04d1b6d59f2b200a7c
branch: 3.9
author: Lysandros Nikolaou <lisandrosnik at gmail.com>
committer: lysnikolaou <lisandrosnik at gmail.com>
date: 2020年10月28日T02:14:15+02:00
summary:
[3.9] bpo-42123: Run the parser two times and only enable invalid rules on the second run (GH-22111) (GH-23011)
* Implement running the parser a second time for the errors messages
The first parser run is only responsible for detecting whether
there is a `SyntaxError` or not. If there isn't the AST gets returned.
Otherwise, the parser is run a second time with all the `invalid_*`
rules enabled so that all the customized error messages get produced.
(cherry picked from commit bca701403253379409dece03053dbd739c0bd059)
files:
A Misc/NEWS.d/next/Core and Builtins/2020-10-23-02-43-24.bpo-42123.64gJWC.rst
M Grammar/python.gram
M Parser/pegen/parse.c
M Parser/pegen/pegen.c
M Parser/pegen/pegen.h
M Tools/peg_generator/pegen/c_generator.py
diff --git a/Grammar/python.gram b/Grammar/python.gram
index 6c36b6acb5352..b709d3d5c3214 100644
--- a/Grammar/python.gram
+++ b/Grammar/python.gram
@@ -535,7 +535,7 @@ yield_expr[expr_ty]:
 
 arguments[expr_ty] (memo):
 | a=args [','] &')' { a }
- | incorrect_arguments
+ | invalid_arguments
 args[expr_ty]:
 | a=','.(starred_expression | named_expression !'=')+ b=[',' k=kwargs {k}] { _PyPegen_collect_call_seqs(p, a, b, EXTRA) }
 | a=kwargs { _Py_Call(_PyPegen_dummy_name(p),
@@ -620,7 +620,7 @@ t_atom[expr_ty]:
 
 
 # From here on, there are rules for invalid syntax with specialised error messages
-incorrect_arguments:
+invalid_arguments:
 | args ',' '*' { RAISE_SYNTAX_ERROR("iterable argument unpacking follows keyword argument unpacking") }
 | a=expression for_if_clauses ',' [args | expression for_if_clauses] {
 RAISE_SYNTAX_ERROR_KNOWN_LOCATION(a, "Generator expression must be parenthesized") }
diff --git a/Misc/NEWS.d/next/Core and Builtins/2020-10-23-02-43-24.bpo-42123.64gJWC.rst b/Misc/NEWS.d/next/Core and Builtins/2020-10-23-02-43-24.bpo-42123.64gJWC.rst
new file mode 100644
index 0000000000000..6461efd76f0f9
--- /dev/null
+++ b/Misc/NEWS.d/next/Core and Builtins/2020-10-23-02-43-24.bpo-42123.64gJWC.rst	
@@ -0,0 +1,3 @@
+Run the parser two times. On the first run, disable all the rules that only
+generate better error messages to gain performance. If there's a parse
+failure, run the parser a second time with those enabled.
diff --git a/Parser/pegen/parse.c b/Parser/pegen/parse.c
index 2eb9e03d52819..48a2443474684 100644
--- a/Parser/pegen/parse.c
+++ b/Parser/pegen/parse.c
@@ -218,7 +218,7 @@ static KeywordToken *reserved_keywords[] = {
 #define t_primary_type 1140 // Left-recursive
 #define t_lookahead_type 1141
 #define t_atom_type 1142
-#define incorrect_arguments_type 1143
+#define invalid_arguments_type 1143
 #define invalid_kwarg_type 1144
 #define invalid_named_expression_type 1145
 #define invalid_assignment_type 1146
@@ -537,7 +537,7 @@ static expr_ty target_rule(Parser *p);
 static expr_ty t_primary_rule(Parser *p);
 static void *t_lookahead_rule(Parser *p);
 static expr_ty t_atom_rule(Parser *p);
-static void *incorrect_arguments_rule(Parser *p);
+static void *invalid_arguments_rule(Parser *p);
 static void *invalid_kwarg_rule(Parser *p);
 static void *invalid_named_expression_rule(Parser *p);
 static void *invalid_assignment_rule(Parser *p);
@@ -2219,7 +2219,7 @@ assignment_rule(Parser *p)
 return NULL;
 }
 }
- { // invalid_assignment
+ if (p->call_invalid_rules) { // invalid_assignment
 if (p->error_indicator) {
 D(p->level--);
 return NULL;
@@ -2892,7 +2892,7 @@ del_stmt_rule(Parser *p)
 D(fprintf(stderr, "%*c%s del_stmt[%d-%d]: %s failed!\n", p->level, ' ',
 p->error_indicator ? "ERROR!" : "-", _mark, p->mark, "'del' del_targets &(';' | NEWLINE)"));
 }
- { // invalid_del_stmt
+ if (p->call_invalid_rules) { // invalid_del_stmt
 if (p->error_indicator) {
 D(p->level--);
 return NULL;
@@ -3243,7 +3243,7 @@ import_from_targets_rule(Parser *p)
 D(fprintf(stderr, "%*c%s import_from_targets[%d-%d]: %s failed!\n", p->level, ' ',
 p->error_indicator ? "ERROR!" : "-", _mark, p->mark, "'*'"));
 }
- { // invalid_import_from_targets
+ if (p->call_invalid_rules) { // invalid_import_from_targets
 if (p->error_indicator) {
 D(p->level--);
 return NULL;
@@ -4036,7 +4036,7 @@ for_stmt_rule(Parser *p)
 return NULL;
 }
 }
- { // invalid_for_target
+ if (p->call_invalid_rules) { // invalid_for_target
 if (p->error_indicator) {
 D(p->level--);
 return NULL;
@@ -4337,7 +4337,7 @@ with_item_rule(Parser *p)
 D(fprintf(stderr, "%*c%s with_item[%d-%d]: %s failed!\n", p->level, ' ',
 p->error_indicator ? "ERROR!" : "-", _mark, p->mark, "expression 'as' star_target &(',' | ')' | ':')"));
 }
- { // invalid_with_item
+ if (p->call_invalid_rules) { // invalid_with_item
 if (p->error_indicator) {
 D(p->level--);
 return NULL;
@@ -5072,7 +5072,7 @@ func_type_comment_rule(Parser *p)
 D(fprintf(stderr, "%*c%s func_type_comment[%d-%d]: %s failed!\n", p->level, ' ',
 p->error_indicator ? "ERROR!" : "-", _mark, p->mark, "NEWLINE TYPE_COMMENT &(NEWLINE INDENT)"));
 }
- { // invalid_double_type_comments
+ if (p->call_invalid_rules) { // invalid_double_type_comments
 if (p->error_indicator) {
 D(p->level--);
 return NULL;
@@ -5127,7 +5127,7 @@ params_rule(Parser *p)
 }
 arguments_ty _res = NULL;
 int _mark = p->mark;
- { // invalid_parameters
+ if (p->call_invalid_rules) { // invalid_parameters
 if (p->error_indicator) {
 D(p->level--);
 return NULL;
@@ -5602,7 +5602,7 @@ star_etc_rule(Parser *p)
 D(fprintf(stderr, "%*c%s star_etc[%d-%d]: %s failed!\n", p->level, ' ',
 p->error_indicator ? "ERROR!" : "-", _mark, p->mark, "kwds"));
 }
- { // invalid_star_etc
+ if (p->call_invalid_rules) { // invalid_star_etc
 if (p->error_indicator) {
 D(p->level--);
 return NULL;
@@ -6305,7 +6305,7 @@ block_rule(Parser *p)
 D(fprintf(stderr, "%*c%s block[%d-%d]: %s failed!\n", p->level, ' ',
 p->error_indicator ? "ERROR!" : "-", _mark, p->mark, "simple_stmt"));
 }
- { // invalid_block
+ if (p->call_invalid_rules) { // invalid_block
 if (p->error_indicator) {
 D(p->level--);
 return NULL;
@@ -6799,7 +6799,7 @@ named_expression_rule(Parser *p)
 D(fprintf(stderr, "%*c%s named_expression[%d-%d]: %s failed!\n", p->level, ' ',
 p->error_indicator ? "ERROR!" : "-", _mark, p->mark, "expression !':='"));
 }
- { // invalid_named_expression
+ if (p->call_invalid_rules) { // invalid_named_expression
 if (p->error_indicator) {
 D(p->level--);
 return NULL;
@@ -7193,7 +7193,7 @@ lambda_params_rule(Parser *p)
 }
 arguments_ty _res = NULL;
 int _mark = p->mark;
- { // invalid_lambda_parameters
+ if (p->call_invalid_rules) { // invalid_lambda_parameters
 if (p->error_indicator) {
 D(p->level--);
 return NULL;
@@ -7670,7 +7670,7 @@ lambda_star_etc_rule(Parser *p)
 D(fprintf(stderr, "%*c%s lambda_star_etc[%d-%d]: %s failed!\n", p->level, ' ',
 p->error_indicator ? "ERROR!" : "-", _mark, p->mark, "lambda_kwds"));
 }
- { // invalid_lambda_star_etc
+ if (p->call_invalid_rules) { // invalid_lambda_star_etc
 if (p->error_indicator) {
 D(p->level--);
 return NULL;
@@ -10330,7 +10330,7 @@ primary_raw(Parser *p)
 UNUSED(_start_lineno); // Only used by EXTRA macro
 int _start_col_offset = p->tokens[_mark]->col_offset;
 UNUSED(_start_col_offset); // Only used by EXTRA macro
- { // invalid_primary
+ if (p->call_invalid_rules) { // invalid_primary
 if (p->error_indicator) {
 D(p->level--);
 return NULL;
@@ -11209,7 +11209,7 @@ listcomp_rule(Parser *p)
 return NULL;
 }
 }
- { // invalid_comprehension
+ if (p->call_invalid_rules) { // invalid_comprehension
 if (p->error_indicator) {
 D(p->level--);
 return NULL;
@@ -11340,7 +11340,7 @@ group_rule(Parser *p)
 D(fprintf(stderr, "%*c%s group[%d-%d]: %s failed!\n", p->level, ' ',
 p->error_indicator ? "ERROR!" : "-", _mark, p->mark, "'(' (yield_expr | named_expression) ')'"));
 }
- { // invalid_group
+ if (p->call_invalid_rules) { // invalid_group
 if (p->error_indicator) {
 D(p->level--);
 return NULL;
@@ -11434,7 +11434,7 @@ genexp_rule(Parser *p)
 return NULL;
 }
 }
- { // invalid_comprehension
+ if (p->call_invalid_rules) { // invalid_comprehension
 if (p->error_indicator) {
 D(p->level--);
 return NULL;
@@ -11593,7 +11593,7 @@ setcomp_rule(Parser *p)
 return NULL;
 }
 }
- { // invalid_comprehension
+ if (p->call_invalid_rules) { // invalid_comprehension
 if (p->error_indicator) {
 D(p->level--);
 return NULL;
@@ -11745,7 +11745,7 @@ dictcomp_rule(Parser *p)
 D(fprintf(stderr, "%*c%s dictcomp[%d-%d]: %s failed!\n", p->level, ' ',
 p->error_indicator ? "ERROR!" : "-", _mark, p->mark, "'{' kvpair for_if_clauses '}'"));
 }
- { // invalid_dict_comprehension
+ if (p->call_invalid_rules) { // invalid_dict_comprehension
 if (p->error_indicator) {
 D(p->level--);
 return NULL;
@@ -12064,7 +12064,7 @@ for_if_clause_rule(Parser *p)
 return NULL;
 }
 }
- { // invalid_for_target
+ if (p->call_invalid_rules) { // invalid_for_target
 if (p->error_indicator) {
 D(p->level--);
 return NULL;
@@ -12190,7 +12190,7 @@ yield_expr_rule(Parser *p)
 return _res;
 }
 
-// arguments: args ','? &')' | incorrect_arguments
+// arguments: args ','? &')' | invalid_arguments
 static expr_ty
 arguments_rule(Parser *p)
 {
@@ -12235,24 +12235,24 @@ arguments_rule(Parser *p)
 D(fprintf(stderr, "%*c%s arguments[%d-%d]: %s failed!\n", p->level, ' ',
 p->error_indicator ? "ERROR!" : "-", _mark, p->mark, "args ','? &')'"));
 }
- { // incorrect_arguments
+ if (p->call_invalid_rules) { // invalid_arguments
 if (p->error_indicator) {
 D(p->level--);
 return NULL;
 }
- D(fprintf(stderr, "%*c> arguments[%d-%d]: %s\n", p->level, ' ', _mark, p->mark, "incorrect_arguments"));
- void *incorrect_arguments_var;
+ D(fprintf(stderr, "%*c> arguments[%d-%d]: %s\n", p->level, ' ', _mark, p->mark, "invalid_arguments"));
+ void *invalid_arguments_var;
 if (
- (incorrect_arguments_var = incorrect_arguments_rule(p)) // incorrect_arguments
+ (invalid_arguments_var = invalid_arguments_rule(p)) // invalid_arguments
 )
 {
- D(fprintf(stderr, "%*c+ arguments[%d-%d]: %s succeeded!\n", p->level, ' ', _mark, p->mark, "incorrect_arguments"));
- _res = incorrect_arguments_var;
+ D(fprintf(stderr, "%*c+ arguments[%d-%d]: %s succeeded!\n", p->level, ' ', _mark, p->mark, "invalid_arguments"));
+ _res = invalid_arguments_var;
 goto done;
 }
 p->mark = _mark;
 D(fprintf(stderr, "%*c%s arguments[%d-%d]: %s failed!\n", p->level, ' ',
- p->error_indicator ? "ERROR!" : "-", _mark, p->mark, "incorrect_arguments"));
+ p->error_indicator ? "ERROR!" : "-", _mark, p->mark, "invalid_arguments"));
 }
 _res = NULL;
 done:
@@ -12589,7 +12589,7 @@ kwarg_or_starred_rule(Parser *p)
 D(fprintf(stderr, "%*c%s kwarg_or_starred[%d-%d]: %s failed!\n", p->level, ' ',
 p->error_indicator ? "ERROR!" : "-", _mark, p->mark, "starred_expression"));
 }
- { // invalid_kwarg
+ if (p->call_invalid_rules) { // invalid_kwarg
 if (p->error_indicator) {
 D(p->level--);
 return NULL;
@@ -12709,7 +12709,7 @@ kwarg_or_double_starred_rule(Parser *p)
 D(fprintf(stderr, "%*c%s kwarg_or_double_starred[%d-%d]: %s failed!\n", p->level, ' ',
 p->error_indicator ? "ERROR!" : "-", _mark, p->mark, "'**' expression"));
 }
- { // invalid_kwarg
+ if (p->call_invalid_rules) { // invalid_kwarg
 if (p->error_indicator) {
 D(p->level--);
 return NULL;
@@ -14421,14 +14421,14 @@ t_atom_rule(Parser *p)
 return _res;
 }
 
-// incorrect_arguments:
+// invalid_arguments:
 // | args ',' '*'
 // | expression for_if_clauses ',' [args | expression for_if_clauses]
 // | args for_if_clauses
 // | args ',' expression for_if_clauses
 // | args ',' args
 static void *
-incorrect_arguments_rule(Parser *p)
+invalid_arguments_rule(Parser *p)
 {
 D(p->level++);
 if (p->error_indicator) {
@@ -14442,7 +14442,7 @@ incorrect_arguments_rule(Parser *p)
 D(p->level--);
 return NULL;
 }
- D(fprintf(stderr, "%*c> incorrect_arguments[%d-%d]: %s\n", p->level, ' ', _mark, p->mark, "args ',' '*'"));
+ D(fprintf(stderr, "%*c> invalid_arguments[%d-%d]: %s\n", p->level, ' ', _mark, p->mark, "args ',' '*'"));
 Token * _literal;
 Token * _literal_1;
 expr_ty args_var;
@@ -14454,7 +14454,7 @@ incorrect_arguments_rule(Parser *p)
 (_literal_1 = _PyPegen_expect_token(p, 16)) // token='*'
 )
 {
- D(fprintf(stderr, "%*c+ incorrect_arguments[%d-%d]: %s succeeded!\n", p->level, ' ', _mark, p->mark, "args ',' '*'"));
+ D(fprintf(stderr, "%*c+ invalid_arguments[%d-%d]: %s succeeded!\n", p->level, ' ', _mark, p->mark, "args ',' '*'"));
 _res = RAISE_SYNTAX_ERROR ( "iterable argument unpacking follows keyword argument unpacking" );
 if (_res == NULL && PyErr_Occurred()) {
 p->error_indicator = 1;
@@ -14464,7 +14464,7 @@ incorrect_arguments_rule(Parser *p)
 goto done;
 }
 p->mark = _mark;
- D(fprintf(stderr, "%*c%s incorrect_arguments[%d-%d]: %s failed!\n", p->level, ' ',
+ D(fprintf(stderr, "%*c%s invalid_arguments[%d-%d]: %s failed!\n", p->level, ' ',
 p->error_indicator ? "ERROR!" : "-", _mark, p->mark, "args ',' '*'"));
 }
 { // expression for_if_clauses ',' [args | expression for_if_clauses]
@@ -14472,7 +14472,7 @@ incorrect_arguments_rule(Parser *p)
 D(p->level--);
 return NULL;
 }
- D(fprintf(stderr, "%*c> incorrect_arguments[%d-%d]: %s\n", p->level, ' ', _mark, p->mark, "expression for_if_clauses ',' [args | expression for_if_clauses]"));
+ D(fprintf(stderr, "%*c> invalid_arguments[%d-%d]: %s\n", p->level, ' ', _mark, p->mark, "expression for_if_clauses ',' [args | expression for_if_clauses]"));
 Token * _literal;
 void *_opt_var;
 UNUSED(_opt_var); // Silence compiler warnings
@@ -14488,7 +14488,7 @@ incorrect_arguments_rule(Parser *p)
 (_opt_var = _tmp_127_rule(p), 1) // [args | expression for_if_clauses]
 )
 {
- D(fprintf(stderr, "%*c+ incorrect_arguments[%d-%d]: %s succeeded!\n", p->level, ' ', _mark, p->mark, "expression for_if_clauses ',' [args | expression for_if_clauses]"));
+ D(fprintf(stderr, "%*c+ invalid_arguments[%d-%d]: %s succeeded!\n", p->level, ' ', _mark, p->mark, "expression for_if_clauses ',' [args | expression for_if_clauses]"));
 _res = RAISE_SYNTAX_ERROR_KNOWN_LOCATION ( a , "Generator expression must be parenthesized" );
 if (_res == NULL && PyErr_Occurred()) {
 p->error_indicator = 1;
@@ -14498,7 +14498,7 @@ incorrect_arguments_rule(Parser *p)
 goto done;
 }
 p->mark = _mark;
- D(fprintf(stderr, "%*c%s incorrect_arguments[%d-%d]: %s failed!\n", p->level, ' ',
+ D(fprintf(stderr, "%*c%s invalid_arguments[%d-%d]: %s failed!\n", p->level, ' ',
 p->error_indicator ? "ERROR!" : "-", _mark, p->mark, "expression for_if_clauses ',' [args | expression for_if_clauses]"));
 }
 { // args for_if_clauses
@@ -14506,7 +14506,7 @@ incorrect_arguments_rule(Parser *p)
 D(p->level--);
 return NULL;
 }
- D(fprintf(stderr, "%*c> incorrect_arguments[%d-%d]: %s\n", p->level, ' ', _mark, p->mark, "args for_if_clauses"));
+ D(fprintf(stderr, "%*c> invalid_arguments[%d-%d]: %s\n", p->level, ' ', _mark, p->mark, "args for_if_clauses"));
 expr_ty a;
 asdl_seq* for_if_clauses_var;
 if (
@@ -14515,7 +14515,7 @@ incorrect_arguments_rule(Parser *p)
 (for_if_clauses_var = for_if_clauses_rule(p)) // for_if_clauses
 )
 {
- D(fprintf(stderr, "%*c+ incorrect_arguments[%d-%d]: %s succeeded!\n", p->level, ' ', _mark, p->mark, "args for_if_clauses"));
+ D(fprintf(stderr, "%*c+ invalid_arguments[%d-%d]: %s succeeded!\n", p->level, ' ', _mark, p->mark, "args for_if_clauses"));
 _res = _PyPegen_nonparen_genexp_in_call ( p , a );
 if (_res == NULL && PyErr_Occurred()) {
 p->error_indicator = 1;
@@ -14525,7 +14525,7 @@ incorrect_arguments_rule(Parser *p)
 goto done;
 }
 p->mark = _mark;
- D(fprintf(stderr, "%*c%s incorrect_arguments[%d-%d]: %s failed!\n", p->level, ' ',
+ D(fprintf(stderr, "%*c%s invalid_arguments[%d-%d]: %s failed!\n", p->level, ' ',
 p->error_indicator ? "ERROR!" : "-", _mark, p->mark, "args for_if_clauses"));
 }
 { // args ',' expression for_if_clauses
@@ -14533,7 +14533,7 @@ incorrect_arguments_rule(Parser *p)
 D(p->level--);
 return NULL;
 }
- D(fprintf(stderr, "%*c> incorrect_arguments[%d-%d]: %s\n", p->level, ' ', _mark, p->mark, "args ',' expression for_if_clauses"));
+ D(fprintf(stderr, "%*c> invalid_arguments[%d-%d]: %s\n", p->level, ' ', _mark, p->mark, "args ',' expression for_if_clauses"));
 Token * _literal;
 expr_ty a;
 expr_ty args_var;
@@ -14548,7 +14548,7 @@ incorrect_arguments_rule(Parser *p)
 (for_if_clauses_var = for_if_clauses_rule(p)) // for_if_clauses
 )
 {
- D(fprintf(stderr, "%*c+ incorrect_arguments[%d-%d]: %s succeeded!\n", p->level, ' ', _mark, p->mark, "args ',' expression for_if_clauses"));
+ D(fprintf(stderr, "%*c+ invalid_arguments[%d-%d]: %s succeeded!\n", p->level, ' ', _mark, p->mark, "args ',' expression for_if_clauses"));
 _res = RAISE_SYNTAX_ERROR_KNOWN_LOCATION ( a , "Generator expression must be parenthesized" );
 if (_res == NULL && PyErr_Occurred()) {
 p->error_indicator = 1;
@@ -14558,7 +14558,7 @@ incorrect_arguments_rule(Parser *p)
 goto done;
 }
 p->mark = _mark;
- D(fprintf(stderr, "%*c%s incorrect_arguments[%d-%d]: %s failed!\n", p->level, ' ',
+ D(fprintf(stderr, "%*c%s invalid_arguments[%d-%d]: %s failed!\n", p->level, ' ',
 p->error_indicator ? "ERROR!" : "-", _mark, p->mark, "args ',' expression for_if_clauses"));
 }
 { // args ',' args
@@ -14566,7 +14566,7 @@ incorrect_arguments_rule(Parser *p)
 D(p->level--);
 return NULL;
 }
- D(fprintf(stderr, "%*c> incorrect_arguments[%d-%d]: %s\n", p->level, ' ', _mark, p->mark, "args ',' args"));
+ D(fprintf(stderr, "%*c> invalid_arguments[%d-%d]: %s\n", p->level, ' ', _mark, p->mark, "args ',' args"));
 Token * _literal;
 expr_ty a;
 expr_ty args_var;
@@ -14578,7 +14578,7 @@ incorrect_arguments_rule(Parser *p)
 (args_var = args_rule(p)) // args
 )
 {
- D(fprintf(stderr, "%*c+ incorrect_arguments[%d-%d]: %s succeeded!\n", p->level, ' ', _mark, p->mark, "args ',' args"));
+ D(fprintf(stderr, "%*c+ invalid_arguments[%d-%d]: %s succeeded!\n", p->level, ' ', _mark, p->mark, "args ',' args"));
 _res = _PyPegen_arguments_parsing_error ( p , a );
 if (_res == NULL && PyErr_Occurred()) {
 p->error_indicator = 1;
@@ -14588,7 +14588,7 @@ incorrect_arguments_rule(Parser *p)
 goto done;
 }
 p->mark = _mark;
- D(fprintf(stderr, "%*c%s incorrect_arguments[%d-%d]: %s failed!\n", p->level, ' ',
+ D(fprintf(stderr, "%*c%s invalid_arguments[%d-%d]: %s failed!\n", p->level, ' ',
 p->error_indicator ? "ERROR!" : "-", _mark, p->mark, "args ',' args"));
 }
 _res = NULL;
diff --git a/Parser/pegen/pegen.c b/Parser/pegen/pegen.c
index a7643fc3a6ad9..78891af825007 100644
--- a/Parser/pegen/pegen.c
+++ b/Parser/pegen/pegen.c
@@ -1101,15 +1101,28 @@ _PyPegen_Parser_New(struct tok_state *tok, int start_rule, int flags,
 p->feature_version = feature_version;
 p->known_err_token = NULL;
 p->level = 0;
+ p->call_invalid_rules = 0;
 
 return p;
 }
 
+static void
+reset_parser_state(Parser *p)
+{
+ for (int i = 0; i < p->fill; i++) {
+ p->tokens[i]->memo = NULL;
+ }
+ p->mark = 0;
+ p->call_invalid_rules = 1;
+}
+
 void *
 _PyPegen_run_parser(Parser *p)
 {
 void *res = _PyPegen_parse(p);
 if (res == NULL) {
+ reset_parser_state(p);
+ _PyPegen_parse(p);
 if (PyErr_Occurred()) {
 return NULL;
 }
diff --git a/Parser/pegen/pegen.h b/Parser/pegen/pegen.h
index bd35d4ff71ae8..2fea84fd22ab4 100644
--- a/Parser/pegen/pegen.h
+++ b/Parser/pegen/pegen.h
@@ -73,6 +73,7 @@ typedef struct {
 growable_comment_array type_ignore_comments;
 Token *known_err_token;
 int level;
+ int call_invalid_rules;
 } Parser;
 
 typedef struct {
diff --git a/Tools/peg_generator/pegen/c_generator.py b/Tools/peg_generator/pegen/c_generator.py
index aee668c3f329a..d0abc12b4026a 100644
--- a/Tools/peg_generator/pegen/c_generator.py
+++ b/Tools/peg_generator/pegen/c_generator.py
@@ -730,7 +730,10 @@ def handle_alt_loop(self, node: Alt, is_gather: bool, rulename: Optional[str]) -
 def visit_Alt(
 self, node: Alt, is_loop: bool, is_gather: bool, rulename: Optional[str]
 ) -> None:
- self.print(f"{{ // {node}")
+ if len(node.items) == 1 and str(node.items[0]).startswith('invalid_'):
+ self.print(f"if (p->call_invalid_rules) {{ // {node}")
+ else:
+ self.print(f"{{ // {node}")
 with self.indent():
 self._check_for_errors()
 node_str = str(node).replace('"', '\\"')

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