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<base href="https://bugs.llvm.org/">
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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - std::to_address isn't SFINAE friendly"
href="https://bugs.llvm.org/show_bug.cgi?id=44846">44846</a>
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</tr>
<tr>
<th>Summary</th>
<td>std::to_address isn't SFINAE friendly
</td>
</tr>
<tr>
<th>Product</th>
<td>libc++
</td>
</tr>
<tr>
<th>Version</th>
<td>unspecified
</td>
</tr>
<tr>
<th>Hardware</th>
<td>PC
</td>
</tr>
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<th>OS</th>
<td>Linux
</td>
</tr>
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<th>Status</th>
<td>NEW
</td>
</tr>
<tr>
<th>Severity</th>
<td>enhancement
</td>
</tr>
<tr>
<th>Priority</th>
<td>P
</td>
</tr>
<tr>
<th>Component</th>
<td>All Bugs
</td>
</tr>
<tr>
<th>Assignee</th>
<td>unassignedclangbugs@nondot.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>cjdb.ns@gmail.com
</td>
</tr>
<tr>
<th>CC</th>
<td>llvm-bugs@lists.llvm.org, mclow.lists@gmail.com
</td>
</tr></table>
<p>
<div>
<pre>The following example should compile, but causes an instantiation error.
```
#include <memory>
struct dummy {};
struct iterator {
using element_type = dummy;
int* operator->() const;
};
template<typename I>
concept passing = requires(I const& i) {
std::to_address(i);
};
static_assert(not passing<iterator>);
```
Because `std::to_address` has a deduced return type, the concept `passing` must
instantiate `std::to_address`, which means that it ironically causes a hard
error when trying to check if the expression is well-formed (the concept is not
at fault here). Changing `std::to_address` to be SFINAE-friendly will be
necessary to implement `std::contiguous_iterator`.
Related issue: <a class="bz_bug_link
bz_status_RESOLVED bz_closed"
title="RESOLVED INVALID - SFINAE leaks through requires expression requirement"
href="show_bug.cgi?id=44674">https://bugs.llvm.org/show_bug.cgi?id=44674</a></pre>
</div>
</p>
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