https://bugs.llvm.org/show_bug.cgi?id=43400
Bug ID: 43400
Summary: template friend is redefinition
Product: clang
Version: trunk
Hardware: PC
OS: Windows NT
Status: NEW
Severity: enhancement
Priority: P
Component: C++
Assignee: unassignedclangb...@nondot.org
Reporter: ca...@carter.net
CC: blitzrak...@gmail.com, dgre...@apple.com,
erik.pilking...@gmail.com, llvm-bugs@lists.llvm.org,
richard-l...@metafoo.co.uk
Created attachment 22540
--> https://bugs.llvm.org/attachment.cgi?id=22540&action=edit
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.
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