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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW --- - enable_if diagnostics don't work well with enable_if_t"
href="http://llvm.org/bugs/show_bug.cgi?id=21125">21125</a>
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<th>Summary</th>
<td>enable_if diagnostics don't work well with enable_if_t
</td>
</tr>
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<th>Product</th>
<td>clang
</td>
</tr>
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<th>Version</th>
<td>trunk
</td>
</tr>
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<th>Hardware</th>
<td>All
</td>
</tr>
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<th>OS</th>
<td>All
</td>
</tr>
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<th>Status</th>
<td>NEW
</td>
</tr>
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<th>Severity</th>
<td>normal
</td>
</tr>
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<th>Priority</th>
<td>P
</td>
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<th>Component</th>
<td>C++1y
</td>
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<th>Assignee</th>
<td>unassignedclangbugs@nondot.org
</td>
</tr>
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<th>Reporter</th>
<td>seth.cantrell@gmail.com
</td>
</tr>
<tr>
<th>CC</th>
<td>llvmbugs@cs.uiuc.edu
</td>
</tr>
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<th>Classification</th>
<td>Unclassified
</td>
</tr></table>
<p>
<div>
<pre>Given a program:
#include <string>
#include <type_traits>
class employee {
std::string name_;
public:
template<typename String,
class = typename
std::enable_if<std::is_assignable<std::decay_t<String>,
decltype(name_)>::value>::type >
void set_name(String &&name) {
name_ = std::forward<String>(name);
}
};
int main() {
employee e;
e.set_name(1);
}
The diagnostics helpfully point directly to the condition that causes the
error:
main.cpp:9:46: note: candidate template ignored: disabled by 'enable_if' [with
String = int]
class = typename
std::enable_if<std::is_assignable<std::decay_t<String>,
decltype(name_)>::value>::type >
^
But when enable_if_t is used, the diagnostic loses this helpful info:
/usr/include/c++/v1/type_traits:225:78: note: candidate template ignored:
disabled by 'enable_if' [with String = int]
template <bool _Bp, class _Tp = void> using enable_if_t = typename
enable_if<_Bp, _Tp>::type;
^</pre>
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