private static @Nullable PsiExpression getCompleteExpression(PsiExpression qualifier) {
    while (true) {
      if (ExpressionUtils.isImplicitToStringCall(qualifier)) {
        return qualifier;
      }
      final PsiMethodCallExpression call = ExpressionUtils.getCallForQualifier(qualifier);
      if (call == null) return null;
      if (isToStringCall(call)) {
        return call;
      }
      if (!isAppendCall(call)) return null;
      qualifier = call;
    }
  }
private static @Nullable PsiExpression getCompleteExpression(PsiExpression qualifier)