public String registerVarName(@NotNull Collection<String> variants) {
    if (variants.isEmpty()) {
      return registerVarName(Collections.singleton("val"));
    }
    for (int idx = 0; ; idx++) {
      for (String variant : variants) {
        String name = idx == 0 ? variant : variant + idx;
        if (!isUsed(name)) {
          myUsedNames.add(name);
          return name;
        }
      }
    }
  }
public String registerVarName(@NotNull Collection<String> variants)