Allow the parser to avoid nested processing of invalid rules (GH-31252)

Author: pablogsal

Grammar/python.gram

@@ -1078,6 +1078,7 @@ invalid_kwarg:
         RAISE_SYNTAX_ERROR_KNOWN_RANGE(
             a, b, "expression cannot contain assignment, perhaps you meant \"==\"?") }
 
+# IMPORTANT: Note that the "_without_invalid" suffix causes the rule to not call invalid rules under it
 expression_without_invalid[expr_ty]:
     | a=disjunction 'if' b=disjunction 'else' c=expression { _PyAST_IfExp(b, a, c, EXTRA) }
     | disjunction
@@ -1095,16 +1096,14 @@ invalid_expression:
         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:
+invalid_named_expression(memo):
     | 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 '='?") }
-    | !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 '='?",
+        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 !('='|':=') {
+        RAISE_SYNTAX_ERROR_KNOWN_LOCATION(a, "cannot assign to %s here. Maybe you meant '==' instead of '='?",
                                           _PyPegen_get_expr_name(a)) }
 
 invalid_assignment:

Lib/test/test_exceptions.py

@@ -231,7 +231,7 @@ def testSyntaxErrorOffset(self):
         check('a = « hello » « world »', 1, 5)
         check('[\nfile\nfor str(file)\nin\n[]\n]', 3, 5)
         check('[file for\n str(file) in []]', 2, 2)
-        check("ages = {'Alice'=22, 'Bob'=23}", 1, 16)
+        check("ages = {'Alice'=22, 'Bob'=23}", 1, 9)
         check('match ...:\n    case {**rest, "key": value}:\n        ...', 2, 19)
         check("[a b c d e f]", 1, 2)
         check("for x yfff:", 1, 7)