src/librustdoc/html/templates/short_item_info.html

{% match self %}
    {% when Self::Deprecation with { message } %}
        <div class="stab deprecated"> {# #}
            <span class="emoji">👎</span> {# #}
            <span>{{message|safe}}</span> {# #}
        </div>
    {% when Self::Unstable with { feature, tracking } %}
        <div class="stab unstable"> {# #}
            <span class="emoji">🔬</span> {# #}
            <span> {# #}
                This is a nightly-only experimental API. ({# #}
                <code>{{feature}}</code>
                {% match tracking %}
                    {% when Some with ((url, num)) %}
                        &nbsp;<a href="{{url}}{{num}}">#{{num}}</a>
                    {% when None %}
                {% endmatch %}
                ) {# #}
            </span> {# #}
        </div>
    {% when Self::Portability with { message } %}
        <div class="stab portability">{{message|safe}}</div>
{% endmatch %}