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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 - template friend is redefinition"
href="https://bugs.llvm.org/show_bug.cgi?id=43400">43400</a>
</td>
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<th>Summary</th>
<td>template friend is redefinition
</td>
</tr>
<tr>
<th>Product</th>
<td>clang
</td>
</tr>
<tr>
<th>Version</th>
<td>trunk
</td>
</tr>
<tr>
<th>Hardware</th>
<td>PC
</td>
</tr>
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<th>OS</th>
<td>Windows NT
</td>
</tr>
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<th>Status</th>
<td>NEW
</td>
</tr>
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<th>Severity</th>
<td>enhancement
</td>
</tr>
<tr>
<th>Priority</th>
<td>P
</td>
</tr>
<tr>
<th>Component</th>
<td>C++
</td>
</tr>
<tr>
<th>Assignee</th>
<td>unassignedclangbugs@nondot.org
</td>
</tr>
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<th>Reporter</th>
<td>Casey@Carter.net
</td>
</tr>
<tr>
<th>CC</th>
<td>blitzrakete@gmail.com, dgregor@apple.com, erik.pilkington@gmail.com, llvm-bugs@lists.llvm.org, richard-llvm@metafoo.co.uk
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<div>
<pre>Created <span class=""><a href="attachment.cgi?id=22540" name="attach_22540" title="Repro">attachment 22540</a> <a href="attachment.cgi?id=22540&action=edit" title="Repro">[details]</a></span>
Repro
Compiling this well-formed program:
template<class>
constexpr bool is_lvalue_reference = false;
template<class T>
constexpr bool is_lvalue_reference<T&> = true;
template<bool> struct int_if_ {};
template<> struct int_if_<true> { using type = int; };
template<bool B> using int_if = typename int_if_<B>::type;
struct Derived;
struct Base {
template<class T>
friend void operator|(T&, Derived const&) = delete;
template<class T, int_if<!is_lvalue_reference<T>> = 0>
friend T operator|(T&& t, Derived const&) {
return static_cast<T&&>(t);
}
};
struct Derived : Base {};
int main() {
struct vector {};
vector v;
v = static_cast<vector&&>(v) | Derived{};
}
produces diagnostics:
repro.cpp(15,17): error: redefinition of 'operator|'
friend void operator|(T&, Derived const&) = delete;
^
repro.cpp(28,34): note: in instantiation of function template
specialization 'operator|<vector>' requested here
v = static_cast<vector&&>(v) | Derived{};
^
repro.cpp(15,17): note: previous definition is here
friend void operator|(T&, Derived const&) = delete;
^
1 error generated.
The problem seems to reproduce on every version of Clang I try, with C++11 or
later.
This doesn't seem to be a duplicate of the other "friend redefinition" bugs
(#35012 and #41523), since it's a template friend of a non-template class, but
I could be mistaken.</pre>
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