As it's requires a PEP, lets yrigger a syntax warning

Author: skirpichev

Lib/test/test_grammar.py

@@ -181,7 +181,9 @@ def test_plain_integers(self):
     def test_attrs_on_hexintegers(self):
         good_meth = [m for m in dir(int) if not m.startswith('_')]
         for m in good_meth:
-            self.assertEqual(eval('0x1.' + m), eval('(0x1).' + m))
+            with self.assertWarns(SyntaxWarning):
+                v = eval('0x1.' + m)
+            self.assertEqual(v, eval('(0x1).' + m))
         self.check_syntax_error('0x1.spam', "invalid hexadecimal literal",
                                 lineno=1, offset=4)
         self.check_syntax_error('0x1.foo', "invalid hexadecimal literal",

Parser/lexer/lexer.c

@@ -793,6 +793,11 @@ tok_get_normal_mode(struct tok_state *tok, tokenizer_mode* current_tok, struct t
                         (c == 'n' && lookahead(tok, "umerator")) ||
                         (c == 'r' && lookahead(tok, "eal")))
                     {
+                        if (_PyTokenizer_parser_warn(tok, PyExc_SyntaxWarning,
+                                                     "invalid float literal"))
+                        {
+                            return 0;
+                        }
                         tok_backup(tok, c);
                         c = '.';
                         goto hexint;