some progress

scanner.c

@@ -60,22 +60,22 @@ bool scan_eof(scanner_t *s) {
 	return *s->cur == '\0';
 }
 
-bool scan_literal(scanner_t *s, char const *lit) {
+scan_result_t scan_literal(scanner_t *s, char const *lit) {
 	char const *save = s->cur;
 	while (*lit && *lit == *s->cur) {
 		lit++;
 		s->cur++;
 	}
 	if (*lit == '\0') {
-		return true;
+		return (scan_result_t) { .ok = true };
 	}
 	s->cur = save;
-	return false;
+	return scan_error(s, "literal not present");
 }
 
 int scan_repeat_literal(scanner_t *s, char const *lit) {
 	int n_repeats = 0;
-	while (scan_literal(s, lit)) {
+	while (scan_literal(s, lit).ok) {
 		n_repeats++;
 	}
 	return n_repeats;