Error display for invalid literal is incorrect

[DELOLCAT]

Bug report

Bug description:

If you run

0x9g

Anywhere (I did it in the REPL), the pointer that shows where the error happened is on 9, even though it is valid:

>>> 0x9g
  File "<stdin>", line 1
    0x9g
      ^
SyntaxError: invalid hexadecimal literal

CPython versions tested on:

3.13

Operating systems tested on:

Linux

Linked PRs

• gh-149277: Fix error position for invalid numeric literals #149456

[picnixz]

It should be a known parser issue somewhere (it happens with non-decimal literals) but I can't find the issue again.

[skirpichev]

It happens with decimal literals too:

Python 3.15.0a8+ (heads/main-dirty:39f123c587a, May  2 2026, 18:34:11) [GCC 14.2.0] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> 123f
  File "<python-input-0>", line 1
    123f
      ^
SyntaxError: invalid decimal literal

[skirpichev]

This patch "works for me":

diff --git a/Parser/lexer/lexer.c b/Parser/lexer/lexer.c
index 7f25afec302..dad8d800617 100644
--- a/Parser/lexer/lexer.c
+++ b/Parser/lexer/lexer.c
@@ -352,7 +352,6 @@ verify_end_of_number(struct tok_state *tok, int c, const char *kind) {
     }
     else /* In future releases, only error will remain. */
     if (c < 128 && is_potential_identifier_char(c)) {
-        tok_backup(tok, c);
         _PyTokenizer_syntaxerror(tok, "invalid %s literal", kind);
         return 0;
     }