 be the decayed form of the `ValueOrError&lt;T, E&gt;` concept matching input type.
</span><span class="c1"></span><span class="k">template</span> <span class="o">&lt;</span><span class="k">class</span><span class="err"> </span><span class="nc">T</span><span class="o">&gt;</span> <span class="k">struct</span> <span class="n">value_or_error</span><span class="o">&lt;</span><span class="n">T</span><span class="p">,</span> <span class="n">U</span><span class="o">&gt;</span>
<span class="p">{</span>
  <span cla