handle 2.3a correctly

main.c

@@ -2117,7 +2117,7 @@ struct expression* parse(const char* text)
         struct string* message = make_unexpected_token_message(tokenizer);
 
         struct expression* error = new_syntax_error_expression(
-            tokenizer->index + 1, message);
+            tokenizer->start_index + 1, message);
 
         free_expression(root);
 

tests.json

@@ -991,7 +991,7 @@
   },
   "2.3a": {
     "exit": 1,
-    "ftime": 1755487294.3795893,
+    "ftime": 1755487439.1222117,
     "output": "syntax error!\n2.3a\n   \u2191\n   \u2514 unexpected identifier token\n"
   },
   "2.5": {
@@ -1616,7 +1616,7 @@
   },
   "~1": {
     "exit": 0,
-    "ftime": 1755487294.3820662,
+    "ftime": 1755487439.1243694,
     "output": "???"
   },
   "~x": {