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  <title>is\_\*\_type should imply is_type</title>
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<h1 class="title" style="text-align:center">is_*_type should imply
is_type</h1>
<table style="border:none;float:right">
  <tr>
    <td>Document #:</td>
    <td>P3781R0</td>
  </tr>
  <tr>
    <td>Date:</td>
    <td>2025-07-05</td>
  </tr>
  <tr>
    <td style="vertical-align:top">Project:</td>
    <td>Programming Language C++</td>
  </tr>
  <tr>
    <td style="vertical-align:top">Audience:</td>
    <td>
      Evolution Working Group<br>
      SG20 Education<br>
    </td>
  </tr>
  <tr>
    <td style="vertical-align:top">Reply-to:</td>
    <td>
      Xavier Bonaventura (<a href="https://www.bmwgroup.com/en/innovation/automated-driving.html">BMW</a>)<br><xavier.bonaventura@bmw.de><br>
    </td>
  </tr>
</table>
</header>
<div style="clear:both">
<h1 data-number="1" id="abstract"><span class="header-section-number">1</span> Abstract<a href="#abstract" class="self-link"></a></h1>
<p>This paper is to raise awareness of a potential user confusion by the
fact that a user needs to check for
<code class="sourceCode cpp">is_type</code> before calling
<code class="sourceCode cpp">is_<span class="op">*</span>_type</code>.
As a solution, it proposes to make the call to
<code class="sourceCode cpp">is_type</code> implicit when calling any of
the
<code class="sourceCode cpp">is_<span class="op">*</span>_type</code>
functions.</p>
<h2 data-number="1.1" id="tony-table"><span class="header-section-number">1.1</span> Tony table<a href="#tony-table" class="self-link"></a></h2>
<table>
<thead>
<tr class="header">
<th><div style="text-align:center">
<strong>Before</strong>
</div></th>
<th><div style="text-align:center">
<strong>After</strong>
</div></th>
</tr>
</thead>
<tbody>
<tr class="odd">
<td><div>

<div class="sourceCode" id="cb1"><pre class="sourceCode cpp"><code class="sourceCode cpp"><span id="cb1-1"><a href="#cb1-1" aria-hidden="true" tabindex="-1"></a><span class="kw">static_assert</span><span class="op">(</span>is_class_type<span class="op">(^^</span>Class<span class="op">))</span>;</span>
<span id="cb1-2"><a href="#cb1-2" aria-hidden="true" tabindex="-1"></a><span class="kw">static_assert</span><span class="op">(!</span>is_class_type<span class="op">(^^</span>function<span class="op">))</span>; <span class="co">//Error: Not constexpr</span></span></code></pre></div>

</div></td>
<td><div>

<div class="sourceCode" id="cb2"><pre class="sourceCode cpp"><code class="sourceCode cpp"><span id="cb2-1"><a href="#cb2-1" aria-hidden="true" tabindex="-1"></a><span class="kw">static_assert</span><span class="op">(</span>is_class_type<span class="op">(^^</span>Class<span class="op">))</span>;</span>
<span id="cb2-2"><a href="#cb2-2" aria-hidden="true" tabindex="-1"></a><span class="kw">static_assert</span><span class="op">(!</span>is_class_type<span class="op">(^^</span>function<span class="op">))</span>; <span class="co">//constexpr</span></span></code></pre></div>

</div></td>
</tr>
</tbody>
</table>
<h1 data-number="2" id="motivation"><span class="header-section-number">2</span> Motivation<a href="#motivation" class="self-link"></a></h1>
<h2 data-number="2.1" id="motivating-example"><span class="header-section-number">2.1</span> Motivating example<a href="#motivating-example" class="self-link"></a></h2>
<p>One reflection use case that is expected to be quite common is to
create bindings. Different logic might be needed to create bindings
depending if the entity is a class or a function. A potential naïve
implementation could be as follows:</p>
<div class="sourceCode" id="cb3"><pre class="sourceCode cpp"><code class="sourceCode cpp"><span id="cb3-1"><a href="#cb3-1" aria-hidden="true" tabindex="-1"></a>    <span class="kw">constexpr</span> <span class="kw">auto</span> namespace_info <span class="op">=</span> <span class="op">^^</span>foo;</span>
<span id="cb3-2"><a href="#cb3-2" aria-hidden="true" tabindex="-1"></a>    <span class="cf">for</span> <span class="op">(</span><span class="dt">int</span> i <span class="op">=</span> <span class="dv">0</span>; <span class="kw">auto</span> element <span class="op">:</span> std<span class="op">::</span>meta<span class="op">::</span>members_of<span class="op">(</span>namespace_info, std<span class="op">::</span>meta<span class="op">::</span>access_context<span class="op">::</span>current<span class="op">()))</span></span>
<span id="cb3-3"><a href="#cb3-3" aria-hidden="true" tabindex="-1"></a>    <span class="op">{</span></span>
<span id="cb3-4"><a href="#cb3-4" aria-hidden="true" tabindex="-1"></a>        <span class="cf">if</span> <span class="op">(</span>std<span class="op">::</span>meta<span class="op">::</span>is_class_type<span class="op">(</span>element<span class="op">))</span></span>
<span id="cb3-5"><a href="#cb3-5" aria-hidden="true" tabindex="-1"></a>        <span class="op">{</span></span>
<span id="cb3-6"><a href="#cb3-6" aria-hidden="true" tabindex="-1"></a>            classes<span class="op">[</span>i<span class="op">++]</span> <span class="op">=</span> std<span class="op">::</span>meta<span class="op">::</span>identifier_of<span class="op">(</span>element<span class="op">)</span>;</span>
<span id="cb3-7"><a href="#cb3-7" aria-hidden="true" tabindex="-1"></a>        <span class="op">}</span></span>
<span id="cb3-8"><a href="#cb3-8" aria-hidden="true" tabindex="-1"></a>    <span class="op">}</span></span></code></pre></div>
<p>The problem with this approach is that it will not work because the
call to <code class="sourceCode cpp">is_class_type</code> is not a
constant expression.</p>
<div class="sourceCode" id="cb4"><pre class="sourceCode cpp"><code class="sourceCode cpp"><span id="cb4-1"><a href="#cb4-1" aria-hidden="true" tabindex="-1"></a>    <span class="cf">if</span> <span class="op">(</span>std<span class="op">::</span>meta<span class="op">::</span>is_class_type<span class="op">(</span>element<span class="op">))</span> <span class="co">// ERROR: element is not a constant expression</span></span></code></pre></div>
<p>It is only a constant expression if
<code class="sourceCode cpp">is_type</code> is equal to
<code class="sourceCode cpp"><span class="kw">true</span></code>. The
user would have to change the code in the following way.</p>
<div class="sourceCode" id="cb5"><pre class="sourceCode cpp"><code class="sourceCode cpp"><span id="cb5-1"><a href="#cb5-1" aria-hidden="true" tabindex="-1"></a>    <span class="cf">if</span> <span class="op">(</span>std<span class="op">::</span>meta<span class="op">::</span>is_type<span class="op">(</span>element<span class="op">)</span> <span class="op">&amp;&amp;</span> std<span class="op">::</span>meta<span class="op">::</span>is_class_type<span class="op">(</span>element<span class="op">))</span></span></code></pre></div>
<p>But this might seem redundant.</p>
<h2 data-number="2.2" id="why-such-confusion"><span class="header-section-number">2.2</span> Why such confusion?<a href="#why-such-confusion" class="self-link"></a></h2>
<p>If we take the <code class="sourceCode cpp">is_class_type</code>
function, the design decision to answer is whether it make sense this
question for any entity or only for types. Let’s take a real world
example to answer such question.</p>
<p>If someone points to a lake and asks “Is it opened?” that is a
nonsensical question. What does it mean a lake to be opened? Could it be
closed? But if someone points to a door and asks “Is it an opened?” then
that is a clear yes or no answer. However, if we change the question to
“Is it an opened door?”, then it does not matter if we point to a lake
or to a door, you can always answer yes or no.</p>
<p>Here we have a similar situation. In the moment we decided to name
such functions with
<code class="sourceCode cpp">is_<span class="op">*</span>_type</code>,
they semantically imply the question “Is it a type?”. Because of that,
it seems confusing to have to also ask for
<code class="sourceCode cpp">is_type</code> separately.</p>
<h1 data-number="3" id="proposal"><span class="header-section-number">3</span> Proposal<a href="#proposal" class="self-link"></a></h1>
<p>The proposal is to change the implementation of most <a href="https://wg21.link/meta.reflection.traits">[meta.reflection.traits]</a>
<code class="sourceCode cpp">is_<span class="op">*</span>_type</code>
functions to check for <code class="sourceCode cpp">is_type</code> when
being called instead of not being
<code class="sourceCode cpp"><span class="kw">constexpr</span></code>.
In case that the provided info type is not a type, they just return
false.</p>
<p>The reason why we should change “most” of them and not all of them,
is because we have some functions that accept multiple info types. For
example, <code class="sourceCode cpp">is_same_type</code> checks if two
types are the same. This implies that you provide two types. What would
it mean the question if one or both are not types?</p>
<p>The functions in <a href="https://wg21.link/meta.reflection.traits">[meta.reflection.traits]</a>
that the name is in the form
<code class="sourceCode cpp">is_<span class="op">*</span>_type</code>
that would be <strong>included in the change</strong> are the following
ones:</p>
<div class="sourceCode" id="cb6"><pre class="sourceCode cpp"><code class="sourceCode cpp"><span id="cb6-1"><a href="#cb6-1" aria-hidden="true" tabindex="-1"></a><span class="co">// associated with [meta.unary.cat], primary type categories</span></span>
<span id="cb6-2"><a href="#cb6-2" aria-hidden="true" tabindex="-1"></a><span class="kw">consteval</span> <span class="dt">bool</span> is_void_type<span class="op">(</span>info type<span class="op">)</span>;</span>
<span id="cb6-3"><a href="#cb6-3" aria-hidden="true" tabindex="-1"></a><span class="kw">consteval</span> <span class="dt">bool</span> is_null_pointer_type<span class="op">(</span>info type<span class="op">)</span>;</span>
<span id="cb6-4"><a href="#cb6-4" aria-hidden="true" tabindex="-1"></a><span class="kw">consteval</span> <span class="dt">bool</span> is_integral_type<span class="op">(</span>info type<span class="op">)</span>;</span>
<span id="cb6-5"><a href="#cb6-5" aria-hidden="true" tabindex="-1"></a><span class="kw">consteval</span> <span class="dt">bool</span> is_floating_point_type<span class="op">(</span>info type<span class="op">)</span>;</span>
<span id="cb6-6"><a href="#cb6-6" aria-hidden="true" tabindex="-1"></a><span class="kw">consteval</span> <span class="dt">bool</span> is_array_type<span class="op">(</span>info type<span class="op">)</span>;</span>
<span id="cb6-7"><a href="#cb6-7" aria-hidden="true" tabindex="-1"></a><span class="kw">consteval</span> <span class="dt">bool</span> is_pointer_type<span class="op">(</span>info type<span class="op">)</span>;</span>
<span id="cb6-8"><a href="#cb6-8" aria-hidden="true" tabindex="-1"></a><span class="kw">consteval</span> <span class="dt">bool</span> is_lvalue_reference_type<span class="op">(</span>info type<span class="op">)</span>;</span>
<span id="cb6-9"><a href="#cb6-9" aria-hidden="true" tabindex="-1"></a><span class="kw">consteval</span> <span class="dt">bool</span> is_rvalue_reference_type<span class="op">(</span>info type<span class="op">)</span>;</span>
<span id="cb6-10"><a href="#cb6-10" aria-hidden="true" tabindex="-1"></a><span class="kw">consteval</span> <span class="dt">bool</span> is_member_object_pointer_type<span class="op">(</span>info type<span class="op">)</span>;</span>
<span id="cb6-11"><a href="#cb6-11" aria-hidden="true" tabindex="-1"></a><span class="kw">consteval</span> <span class="dt">bool</span> is_member_function_pointer_type<span class="op">(</span>info type<span class="op">)</span>;</span>
<span id="cb6-12"><a href="#cb6-12" aria-hidden="true" tabindex="-1"></a><span class="kw">consteval</span> <span class="dt">bool</span> is_enum_type<span class="op">(</span>info type<span class="op">)</span>;</span>
<span id="cb6-13"><a href="#cb6-13" aria-hidden="true" tabindex="-1"></a><span class="kw">consteval</span> <span class="dt">bool</span> is_union_type<span class="op">(</span>info type<span class="op">)</span>;</span>
<span id="cb6-14"><a href="#cb6-14" aria-hidden="true" tabindex="-1"></a><span class="kw">consteval</span> <span class="dt">bool</span> is_class_type<span class="op">(</span>info type<span class="op">)</span>;</span>
<span id="cb6-15"><a href="#cb6-15" aria-hidden="true" tabindex="-1"></a><span class="kw">consteval</span> <span class="dt">bool</span> is_function_type<span class="op">(</span>info type<span class="op">)</span>;</span>
<span id="cb6-16"><a href="#cb6-16" aria-hidden="true" tabindex="-1"></a><span class="kw">consteval</span> <span class="dt">bool</span> is_reflection_type<span class="op">(</span>info type<span class="op">)</span>;</span>
<span id="cb6-17"><a href="#cb6-17" aria-hidden="true" tabindex="-1"></a></span>
<span id="cb6-18"><a href="#cb6-18" aria-hidden="true" tabindex="-1"></a><span class="co">// associated with [meta.unary.comp], composite type categories</span></span>
<span id="cb6-19"><a href="#cb6-19" aria-hidden="true" tabindex="-1"></a><span class="kw">consteval</span> <span class="dt">bool</span> is_reference_type<span class="op">(</span>info type<span class="op">)</span>;</span>
<span id="cb6-20"><a href="#cb6-20" aria-hidden="true" tabindex="-1"></a><span class="kw">consteval</span> <span class="dt">bool</span> is_arithmetic_type<span class="op">(</span>info type<span class="op">)</span>;</span>
<span id="cb6-21"><a href="#cb6-21" aria-hidden="true" tabindex="-1"></a><span class="kw">consteval</span> <span class="dt">bool</span> is_fundamental_type<span class="op">(</span>info type<span class="op">)</span>;</span>
<span id="cb6-22"><a href="#cb6-22" aria-hidden="true" tabindex="-1"></a><span class="kw">consteval</span> <span class="dt">bool</span> is_object_type<span class="op">(</span>info type<span class="op">)</span>;</span>
<span id="cb6-23"><a href="#cb6-23" aria-hidden="true" tabindex="-1"></a><span class="kw">consteval</span> <span class="dt">bool</span> is_scalar_type<span class="op">(</span>info type<span class="op">)</span>;</span>
<span id="cb6-24"><a href="#cb6-24" aria-hidden="true" tabindex="-1"></a><span class="kw">consteval</span> <span class="dt">bool</span> is_compound_type<span class="op">(</span>info type<span class="op">)</span>;</span>
<span id="cb6-25"><a href="#cb6-25" aria-hidden="true" tabindex="-1"></a><span class="kw">consteval</span> <span class="dt">bool</span> is_member_pointer_type<span class="op">(</span>info type<span class="op">)</span>;</span>
<span id="cb6-26"><a href="#cb6-26" aria-hidden="true" tabindex="-1"></a></span>
<span id="cb6-27"><a href="#cb6-27" aria-hidden="true" tabindex="-1"></a><span class="co">// associated with [meta.unary.prop], type properties</span></span>
<span id="cb6-28"><a href="#cb6-28" aria-hidden="true" tabindex="-1"></a><span class="kw">consteval</span> <span class="dt">bool</span> is_const_type<span class="op">(</span>info type<span class="op">)</span>;</span>
<span id="cb6-29"><a href="#cb6-29" aria-hidden="true" tabindex="-1"></a><span class="kw">consteval</span> <span class="dt">bool</span> is_volatile_type<span class="op">(</span>info type<span class="op">)</span>;</span>
<span id="cb6-30"><a href="#cb6-30" aria-hidden="true" tabindex="-1"></a><span class="kw">consteval</span> <span class="dt">bool</span> is_trivially_copyable_type<span class="op">(</span>info type<span class="op">)</span>;</span>
<span id="cb6-31"><a href="#cb6-31" aria-hidden="true" tabindex="-1"></a><span class="kw">consteval</span> <span class="dt">bool</span> is_trivially_relocatable_type<span class="op">(</span>info type<span class="op">)</span>;</span>
<span id="cb6-32"><a href="#cb6-32" aria-hidden="true" tabindex="-1"></a><span class="kw">consteval</span> <span class="dt">bool</span> is_replaceable_type<span class="op">(</span>info type<span class="op">)</span>;</span>
<span id="cb6-33"><a href="#cb6-33" aria-hidden="true" tabindex="-1"></a><span class="kw">consteval</span> <span class="dt">bool</span> is_standard_layout_type<span class="op">(</span>info type<span class="op">)</span>;</span>
<span id="cb6-34"><a href="#cb6-34" aria-hidden="true" tabindex="-1"></a><span class="kw">consteval</span> <span class="dt">bool</span> is_empty_type<span class="op">(</span>info type<span class="op">)</span>;</span>
<span id="cb6-35"><a href="#cb6-35" aria-hidden="true" tabindex="-1"></a><span class="kw">consteval</span> <span class="dt">bool</span> is_polymorphic_type<span class="op">(</span>info type<span class="op">)</span>;</span>
<span id="cb6-36"><a href="#cb6-36" aria-hidden="true" tabindex="-1"></a><span class="kw">consteval</span> <span class="dt">bool</span> is_abstract_type<span class="op">(</span>info type<span class="op">)</span>;</span>
<span id="cb6-37"><a href="#cb6-37" aria-hidden="true" tabindex="-1"></a><span class="kw">consteval</span> <span class="dt">bool</span> is_final_type<span class="op">(</span>info type<span class="op">)</span>;</span>
<span id="cb6-38"><a href="#cb6-38" aria-hidden="true" tabindex="-1"></a><span class="kw">consteval</span> <span class="dt">bool</span> is_aggregate_type<span class="op">(</span>info type<span class="op">)</span>;</span>
<span id="cb6-39"><a href="#cb6-39" aria-hidden="true" tabindex="-1"></a><span class="kw">consteval</span> <span class="dt">bool</span> is_consteval_only_type<span class="op">(</span>info type<span class="op">)</span>;</span>
<span id="cb6-40"><a href="#cb6-40" aria-hidden="true" tabindex="-1"></a><span class="kw">consteval</span> <span class="dt">bool</span> is_signed_type<span class="op">(</span>info type<span class="op">)</span>;</span>
<span id="cb6-41"><a href="#cb6-41" aria-hidden="true" tabindex="-1"></a><span class="kw">consteval</span> <span class="dt">bool</span> is_unsigned_type<span class="op">(</span>info type<span class="op">)</span>;</span>
<span id="cb6-42"><a href="#cb6-42" aria-hidden="true" tabindex="-1"></a><span class="kw">consteval</span> <span class="dt">bool</span> is_bounded_array_type<span class="op">(</span>info type<span class="op">)</span>;</span>
<span id="cb6-43"><a href="#cb6-43" aria-hidden="true" tabindex="-1"></a><span class="kw">consteval</span> <span class="dt">bool</span> is_unbounded_array_type<span class="op">(</span>info type<span class="op">)</span>;</span>
<span id="cb6-44"><a href="#cb6-44" aria-hidden="true" tabindex="-1"></a><span class="kw">consteval</span> <span class="dt">bool</span> is_scoped_enum_type<span class="op">(</span>info type<span class="op">)</span>;</span>
<span id="cb6-45"><a href="#cb6-45" aria-hidden="true" tabindex="-1"></a></span>
<span id="cb6-46"><a href="#cb6-46" aria-hidden="true" tabindex="-1"></a><span class="kw">template</span> <span class="op">&lt;</span>reflection_range R <span class="op">=</span> initializer_list<span class="op">&lt;</span>info<span class="op">&gt;&gt;</span></span>
<span id="cb6-47"><a href="#cb6-47" aria-hidden="true" tabindex="-1"></a><span class="kw">consteval</span> <span class="dt">bool</span> is_constructible_type<span class="op">(</span>info type, R<span class="op">&amp;&amp;</span> type_args<span class="op">)</span>;</span>
<span id="cb6-48"><a href="#cb6-48" aria-hidden="true" tabindex="-1"></a><span class="kw">consteval</span> <span class="dt">bool</span> is_default_constructible_type<span class="op">(</span>info type<span class="op">)</span>;</span>
<span id="cb6-49"><a href="#cb6-49" aria-hidden="true" tabindex="-1"></a><span class="kw">consteval</span> <span class="dt">bool</span> is_copy_constructible_type<span class="op">(</span>info type<span class="op">)</span>;</span>
<span id="cb6-50"><a href="#cb6-50" aria-hidden="true" tabindex="-1"></a><span class="kw">consteval</span> <span class="dt">bool</span> is_move_constructible_type<span class="op">(</span>info type<span class="op">)</span>;</span>
<span id="cb6-51"><a href="#cb6-51" aria-hidden="true" tabindex="-1"></a></span>
<span id="cb6-52"><a href="#cb6-52" aria-hidden="true" tabindex="-1"></a><span class="kw">consteval</span> <span class="dt">bool</span> is_copy_assignable_type<span class="op">(</span>info type<span class="op">)</span>;</span>
<span id="cb6-53"><a href="#cb6-53" aria-hidden="true" tabindex="-1"></a><span class="kw">consteval</span> <span class="dt">bool</span> is_move_assignable_type<span class="op">(</span>info type<span class="op">)</span>;</span>
<span id="cb6-54"><a href="#cb6-54" aria-hidden="true" tabindex="-1"></a></span>
<span id="cb6-55"><a href="#cb6-55" aria-hidden="true" tabindex="-1"></a><span class="kw">consteval</span> <span class="dt">bool</span> is_swappable_type<span class="op">(</span>info type<span class="op">)</span>;</span>
<span id="cb6-56"><a href="#cb6-56" aria-hidden="true" tabindex="-1"></a></span>
<span id="cb6-57"><a href="#cb6-57" aria-hidden="true" tabindex="-1"></a><span class="kw">consteval</span> <span class="dt">bool</span> is_destructible_type<span class="op">(</span>info type<span class="op">)</span>;</span>
<span id="cb6-58"><a href="#cb6-58" aria-hidden="true" tabindex="-1"></a></span>
<span id="cb6-59"><a href="#cb6-59" aria-hidden="true" tabindex="-1"></a><span class="kw">template</span> <span class="op">&lt;</span>reflection_range R <span class="op">=</span> initializer_list<span class="op">&lt;</span>info<span class="op">&gt;&gt;</span></span>
<span id="cb6-60"><a href="#cb6-60" aria-hidden="true" tabindex="-1"></a><span class="kw">consteval</span> <span class="dt">bool</span> is_trivially_constructible_type<span class="op">(</span>info type, R<span class="op">&amp;&amp;</span> type_args<span class="op">)</span>;</span>
<span id="cb6-61"><a href="#cb6-61" aria-hidden="true" tabindex="-1"></a><span class="kw">consteval</span> <span class="dt">bool</span> is_trivially_default_constructible_type<span class="op">(</span>info type<span class="op">)</span>;</span>
<span id="cb6-62"><a href="#cb6-62" aria-hidden="true" tabindex="-1"></a><span class="kw">consteval</span> <span class="dt">bool</span> is_trivially_copy_constructible_type<span class="op">(</span>info type<span class="op">)</span>;</span>
<span id="cb6-63"><a href="#cb6-63" aria-hidden="true" tabindex="-1"></a><span class="kw">consteval</span> <span class="dt">bool</span> is_trivially_move_constructible_type<span class="op">(</span>info type<span class="op">)</span>;</span>
<span id="cb6-64"><a href="#cb6-64" aria-hidden="true" tabindex="-1"></a></span>
<span id="cb6-65"><a href="#cb6-65" aria-hidden="true" tabindex="-1"></a><span class="kw">consteval</span> <span class="dt">bool</span> is_trivially_copy_assignable_type<span class="op">(</span>info type<span class="op">)</span>;</span>
<span id="cb6-66"><a href="#cb6-66" aria-hidden="true" tabindex="-1"></a><span class="kw">consteval</span> <span class="dt">bool</span> is_trivially_move_assignable_type<span class="op">(</span>info type<span class="op">)</span>;</span>
<span id="cb6-67"><a href="#cb6-67" aria-hidden="true" tabindex="-1"></a><span class="kw">consteval</span> <span class="dt">bool</span> is_trivially_destructible_type<span class="op">(</span>info type<span class="op">)</span>;</span>
<span id="cb6-68"><a href="#cb6-68" aria-hidden="true" tabindex="-1"></a></span>
<span id="cb6-69"><a href="#cb6-69" aria-hidden="true" tabindex="-1"></a><span class="kw">template</span> <span class="op">&lt;</span>reflection_range R <span class="op">=</span> initializer_list<span class="op">&lt;</span>info<span class="op">&gt;&gt;</span></span>
<span id="cb6-70"><a href="#cb6-70" aria-hidden="true" tabindex="-1"></a><span class="kw">consteval</span> <span class="dt">bool</span> is_nothrow_constructible_type<span class="op">(</span>info type, R<span class="op">&amp;&amp;</span> type_args<span class="op">)</span>;</span>
<span id="cb6-71"><a href="#cb6-71" aria-hidden="true" tabindex="-1"></a><span class="kw">consteval</span> <span class="dt">bool</span> is_nothrow_default_constructible_type<span class="op">(</span>info type<span class="op">)</span>;</span>
<span id="cb6-72"><a href="#cb6-72" aria-hidden="true" tabindex="-1"></a><span class="kw">consteval</span> <span class="dt">bool</span> is_nothrow_copy_constructible_type<span class="op">(</span>info type<span class="op">)</span>;</span>
<span id="cb6-73"><a href="#cb6-73" aria-hidden="true" tabindex="-1"></a><span class="kw">consteval</span> <span class="dt">bool</span> is_nothrow_move_constructible_type<span class="op">(</span>info type<span class="op">)</span>;</span>
<span id="cb6-74"><a href="#cb6-74" aria-hidden="true" tabindex="-1"></a></span>
<span id="cb6-75"><a href="#cb6-75" aria-hidden="true" tabindex="-1"></a><span class="kw">consteval</span> <span class="dt">bool</span> is_nothrow_copy_assignable_type<span class="op">(</span>info type<span class="op">)</span>;</span>
<span id="cb6-76"><a href="#cb6-76" aria-hidden="true" tabindex="-1"></a><span class="kw">consteval</span> <span class="dt">bool</span> is_nothrow_move_assignable_type<span class="op">(</span>info type<span class="op">)</span>;</span>
<span id="cb6-77"><a href="#cb6-77" aria-hidden="true" tabindex="-1"></a></span>
<span id="cb6-78"><a href="#cb6-78" aria-hidden="true" tabindex="-1"></a><span class="kw">consteval</span> <span class="dt">bool</span> is_nothrow_swappable_type<span class="op">(</span>info type<span class="op">)</span>;</span>
<span id="cb6-79"><a href="#cb6-79" aria-hidden="true" tabindex="-1"></a></span>
<span id="cb6-80"><a href="#cb6-80" aria-hidden="true" tabindex="-1"></a><span class="kw">consteval</span> <span class="dt">bool</span> is_nothrow_destructible_type<span class="op">(</span>info type<span class="op">)</span>;</span>
<span id="cb6-81"><a href="#cb6-81" aria-hidden="true" tabindex="-1"></a><span class="kw">consteval</span> <span class="dt">bool</span> is_nothrow_relocatable_type<span class="op">(</span>info type<span class="op">)</span>;</span>
<span id="cb6-82"><a href="#cb6-82" aria-hidden="true" tabindex="-1"></a></span>
<span id="cb6-83"><a href="#cb6-83" aria-hidden="true" tabindex="-1"></a><span class="kw">consteval</span> <span class="dt">bool</span> is_implicit_lifetime_type<span class="op">(</span>info type<span class="op">)</span>;</span>
<span id="cb6-84"><a href="#cb6-84" aria-hidden="true" tabindex="-1"></a></span>
<span id="cb6-85"><a href="#cb6-85" aria-hidden="true" tabindex="-1"></a><span class="co">// associated with [meta.rel], type relations</span></span>
<span id="cb6-86"><a href="#cb6-86" aria-hidden="true" tabindex="-1"></a><span class="kw">template</span> <span class="op">&lt;</span>reflection_range R <span class="op">=</span> initializer_list<span class="op">&lt;</span>info<span class="op">&gt;&gt;</span></span>
<span id="cb6-87"><a href="#cb6-87" aria-hidden="true" tabindex="-1"></a><span class="kw">consteval</span> <span class="dt">bool</span> is_invocable_type<span class="op">(</span>info type, R<span class="op">&amp;&amp;</span> type_args<span class="op">)</span>;</span>
<span id="cb6-88"><a href="#cb6-88" aria-hidden="true" tabindex="-1"></a></span>
<span id="cb6-89"><a href="#cb6-89" aria-hidden="true" tabindex="-1"></a><span class="kw">template</span> <span class="op">&lt;</span>reflection_range R <span class="op">=</span> initializer_list<span class="op">&lt;</span>info<span class="op">&gt;&gt;</span></span>
<span id="cb6-90"><a href="#cb6-90" aria-hidden="true" tabindex="-1"></a><span class="kw">consteval</span> <span class="dt">bool</span> is_nothrow_invocable_type<span class="op">(</span>info type, R<span class="op">&amp;&amp;</span> type_args<span class="op">)</span>;</span></code></pre></div>
<p>The functions in <a href="https://wg21.link/meta.reflection.traits">[meta.reflection.traits]</a>
that the name is in the form
<code class="sourceCode cpp">is_<span class="op">*</span>_type</code>
that would be <strong>excluded from the change</strong> are the
following ones:</p>
<div class="sourceCode" id="cb7"><pre class="sourceCode cpp"><code class="sourceCode cpp"><span id="cb7-1"><a href="#cb7-1" aria-hidden="true" tabindex="-1"></a><span class="co">// associated with [meta.unary.prop], type properties</span></span>
<span id="cb7-2"><a href="#cb7-2" aria-hidden="true" tabindex="-1"></a><span class="kw">consteval</span> <span class="dt">bool</span> is_assignable_type<span class="op">(</span>info type_dst, info type_src<span class="op">)</span>;</span>
<span id="cb7-3"><a href="#cb7-3" aria-hidden="true" tabindex="-1"></a><span class="kw">consteval</span> <span class="dt">bool</span> is_trivially_assignable_type<span class="op">(</span>info type_dst, info type_src<span class="op">)</span>;</span>
<span id="cb7-4"><a href="#cb7-4" aria-hidden="true" tabindex="-1"></a><span class="kw">consteval</span> <span class="dt">bool</span> is_nothrow_assignable_type<span class="op">(</span>info type_dst, info type_src<span class="op">)</span>;</span>
<span id="cb7-5"><a href="#cb7-5" aria-hidden="true" tabindex="-1"></a></span>
<span id="cb7-6"><a href="#cb7-6" aria-hidden="true" tabindex="-1"></a><span class="kw">consteval</span> <span class="dt">bool</span> is_swappable_with_type<span class="op">(</span>info type_dst, info type_src<span class="op">)</span>;</span>
<span id="cb7-7"><a href="#cb7-7" aria-hidden="true" tabindex="-1"></a><span class="kw">consteval</span> <span class="dt">bool</span> is_nothrow_swappable_with_type<span class="op">(</span>info type_dst, info type_src<span class="op">)</span>;</span>
<span id="cb7-8"><a href="#cb7-8" aria-hidden="true" tabindex="-1"></a></span>
<span id="cb7-9"><a href="#cb7-9" aria-hidden="true" tabindex="-1"></a><span class="co">// associated with [meta.rel], type relations</span></span>
<span id="cb7-10"><a href="#cb7-10" aria-hidden="true" tabindex="-1"></a><span class="kw">consteval</span> <span class="dt">bool</span> is_same_type<span class="op">(</span>info type1, info type2<span class="op">)</span>;</span>
<span id="cb7-11"><a href="#cb7-11" aria-hidden="true" tabindex="-1"></a><span class="kw">consteval</span> <span class="dt">bool</span> is_base_of_type<span class="op">(</span>info type_base, info type_derived<span class="op">)</span>;</span>
<span id="cb7-12"><a href="#cb7-12" aria-hidden="true" tabindex="-1"></a><span class="kw">consteval</span> <span class="dt">bool</span> is_virtual_base_of_type<span class="op">(</span>info type_base, info type_derived<span class="op">)</span>;</span>
<span id="cb7-13"><a href="#cb7-13" aria-hidden="true" tabindex="-1"></a><span class="kw">consteval</span> <span class="dt">bool</span> is_convertible_type<span class="op">(</span>info type_src, info type_dst<span class="op">)</span>;</span>
<span id="cb7-14"><a href="#cb7-14" aria-hidden="true" tabindex="-1"></a><span class="kw">consteval</span> <span class="dt">bool</span> is_nothrow_convertible_type<span class="op">(</span>info type_src, info type_dst<span class="op">)</span>;</span>
<span id="cb7-15"><a href="#cb7-15" aria-hidden="true" tabindex="-1"></a><span class="kw">consteval</span> <span class="dt">bool</span> is_layout_compatible_type<span class="op">(</span>info type1, info type2<span class="op">)</span>;</span>
<span id="cb7-16"><a href="#cb7-16" aria-hidden="true" tabindex="-1"></a><span class="kw">consteval</span> <span class="dt">bool</span> is_pointer_interconvertible_base_of_type<span class="op">(</span>info type_base, info type_derived<span class="op">)</span>;</span>
<span id="cb7-17"><a href="#cb7-17" aria-hidden="true" tabindex="-1"></a></span>
<span id="cb7-18"><a href="#cb7-18" aria-hidden="true" tabindex="-1"></a><span class="kw">template</span> <span class="op">&lt;</span>reflection_range R <span class="op">=</span> initializer_list<span class="op">&lt;</span>info<span class="op">&gt;&gt;</span></span>
<span id="cb7-19"><a href="#cb7-19" aria-hidden="true" tabindex="-1"></a><span class="kw">consteval</span> <span class="dt">bool</span> is_invocable_r_type<span class="op">(</span>info type_result, info type, R<span class="op">&amp;&amp;</span> type_args<span class="op">)</span>;</span>
<span id="cb7-20"><a href="#cb7-20" aria-hidden="true" tabindex="-1"></a></span>
<span id="cb7-21"><a href="#cb7-21" aria-hidden="true" tabindex="-1"></a><span class="kw">template</span> <span class="op">&lt;</span>reflection_range R <span class="op">=</span> initializer_list<span class="op">&lt;</span>info<span class="op">&gt;&gt;</span></span>
<span id="cb7-22"><a href="#cb7-22" aria-hidden="true" tabindex="-1"></a><span class="kw">consteval</span> <span class="dt">bool</span> is_nothrow_invocable_r_type<span class="op">(</span>info type_result, info type, R<span class="op">&amp;&amp;</span> type_args<span class="op">)</span>;</span></code></pre></div>
<h1 data-number="4" id="potential-polls"><span class="header-section-number">4</span> Potential polls<a href="#potential-polls" class="self-link"></a></h1>
<ol type="1">
<li>The fact that
<code class="sourceCode cpp">is_<span class="op">*</span>_type</code>
functions require an additional check of
<code class="sourceCode cpp">is_type</code> to make them constant
expression might confuse user</li>
</ol>
<table>
<thead>
<tr class="header">
<th><div style="text-align:center">
<strong>SF</strong>
</div></th>
<th><div style="text-align:center">
<strong>F</strong>
</div></th>
<th><div style="text-align:center">
<strong>N</strong>
</div></th>
<th><div style="text-align:center">
<strong>A</strong>
</div></th>
<th><div style="text-align:center">
<strong>SA</strong>
</div></th>
</tr>
</thead>
<tbody>
<tr class="odd">
<td></td>
<td></td>
<td></td>
<td></td>
<td></td>
</tr>
</tbody>
</table>
<ol start="2" type="1">
<li>The author should pursue the direction on making
<code class="sourceCode cpp">is_type</code> implicit when calling
<code class="sourceCode cpp">is_<span class="op">*</span>_type</code>
functions</li>
</ol>
<table>
<thead>
<tr class="header">
<th><div style="text-align:center">
<strong>SF</strong>
</div></th>
<th><div style="text-align:center">
<strong>F</strong>
</div></th>
<th><div style="text-align:center">
<strong>N</strong>
</div></th>
<th><div style="text-align:center">
<strong>A</strong>
</div></th>
<th><div style="text-align:center">
<strong>SA</strong>
</div></th>
</tr>
</thead>
<tbody>
<tr class="odd">
<td></td>
<td></td>
<td></td>
<td></td>
<td></td>
</tr>
</tbody>
</table>
<h1 data-number="5" id="wording"><span class="header-section-number">5</span> Wording<a href="#wording" class="self-link"></a></h1>
<p>To be added in a future revision if the committe agrees that the
current implementation might be confusing and the proposed solution
should be pursued.</p>
</div>
</div>
</body>
</html>
