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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - [Concepts] void f(Constrained decltype(auto)) should be rejected"
href="https://bugs.llvm.org/show_bug.cgi?id=48384">48384</a>
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<th>Summary</th>
<td>[Concepts] void f(Constrained decltype(auto)) should be rejected
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<th>Product</th>
<td>clang
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<th>Version</th>
<td>trunk
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<th>Hardware</th>
<td>All
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<th>OS</th>
<td>All
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<th>Status</th>
<td>NEW
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<th>Severity</th>
<td>normal
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<th>Priority</th>
<td>P
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<th>Component</th>
<td>C++2a
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<th>Assignee</th>
<td>unassignedclangbugs@nondot.org
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<th>Reporter</th>
<td>arthur.j.odwyer@gmail.com
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<th>CC</th>
<td>blitzrakete@gmail.com, erik.pilkington@gmail.com, llvm-bugs@lists.llvm.org, richard-llvm@metafoo.co.uk
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<p>
<div>
<pre>// <a href="https://godbolt.org/z/deh8oT">https://godbolt.org/z/deh8oT</a>
template<class> concept C = true;
void f(C decltype(auto));
Should be ill-formed, according to <a href="http://eel.is/c++draft/dcl.fct#18.sentence-6">http://eel.is/c++draft/dcl.fct#18.sentence-6</a>
, but Clang accepts it.
Clang does know that
void f(decltype(auto));
is ill-formed, but Clang doesn't know that
void f(C decltype(auto));
should also be ill-formed.
----
Incidentally, I'm confused about
template<decltype(auto)> void g();
template<C decltype(auto)> void h();
Clang, GCC, and MSVC all agree that both of those are well-formed, but I don't
know the rationale for accepting _template_ parameters of decltype(auto) type,
given that _function_ parameters of decltype(auto) type are forbidden.
GCC also accepts decltype(auto)& here:
template<decltype(auto)&> void i();</pre>
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