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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - libc++ says my user-defined type has an operator<< during sfinae - libstdc++ works as expected"
href="https://bugs.llvm.org/show_bug.cgi?id=35063">35063</a>
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<th>Summary</th>
<td>libc++ says my user-defined type has an operator<< during sfinae - libstdc++ works as expected
</td>
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<th>Product</th>
<td>libc++
</td>
</tr>
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<th>Version</th>
<td>unspecified
</td>
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<th>Hardware</th>
<td>PC
</td>
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<th>OS</th>
<td>All
</td>
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<th>Status</th>
<td>NEW
</td>
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<th>Severity</th>
<td>normal
</td>
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<th>Priority</th>
<td>P
</td>
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<th>Component</th>
<td>All Bugs
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<th>Assignee</th>
<td>unassignedclangbugs@nondot.org
</td>
</tr>
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<th>Reporter</th>
<td>xaxxon@gmail.com
</td>
</tr>
<tr>
<th>CC</th>
<td>llvm-bugs@lists.llvm.org, mclow.lists@gmail.com
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<p>
<div>
<pre><a href="https://godbolt.org/g/PRfyjH">https://godbolt.org/g/PRfyjH</a>
#include <type_traits>
#include <iostream>
template<typename T, typename = void>
struct has_insertion_operator : std::false_type {};
template<typename T>
struct has_insertion_operator<T,
std::void_t<decltype(
operator<<(std::declval<std::ostream>(),
std::declval<T>()))>
> : std::true_type {};
template<class T>
constexpr bool has_insertion_operator_v = has_insertion_operator<T>::value;
class A{};
static_assert(!has_insertion_operator_v<A>); // <== I expect this to pass, but
it fires on libc++.</pre>
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