When using \hl for highlighting, latex always reports an error when encountering a reference, showing that there are fewer or more parentheses

Problems with \ref when using soul for highlighting
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I’ve run across a `}’ that doesn’t seem to match anything.

resolvent resolvent

Enclosing the \ref{x} in { } works. soul then takes it as one element instead of breaking it up, I guess. It seems to me that it reads both \ref and {x} in two steps and sets it together again while adding another set of braces, i.e. the result is \ref{ {x}}. This doesn’t matter much for font commands but \ref takes the inner braces as part of the label name. This causes the warning about the unknown label. The error is caused because \ref is then also expanded by soul inside a { } group, i.e. {\ref}. Don’t ask me why.

Note that you can’t label a \section* because it doesn’t has a number.

\documentclass[10pt]{
    article}
\usepackage[usenames,dvipsnames]{
    color}
\usepackage{
    soul}
%\soulregister{
    \ref}{
    1}
\begin{
    document}

\section{
    x}\label{
    x}

\section{
    y}
\hl{
     Some text.
   Section~{
    \ref{
    x}}.
}
\end{
    document}

What I try is to \ref{x} Add a brace outside and it will become {\ref(x)}