Implicit conversion from long rvalue reference to int rvalue reference via a conversion operator fails

[Fedr]

This program

long nil = 0;

struct S {
    operator long &&() const { 
        return static_cast<long&&>(nil);
    }
};

int main() { 
    int &&a((S()));
    return a;
}

is accepted by GCC, EDG and MSVC. But not in Clang:

error: no viable conversion from 'S' to 'int'

Online demo: https://gcc.godbolt.org/z/M7W3oYsGz

This is a slightly modified example from https://stackoverflow.com/q/79885636/7325599

[llvmbot]

@llvm/issue-subscribers-clang-frontend

Author: Fedor Chelnokov (Fedr)

Details

This program ```c++ long nil = 0;

struct S {
operator long &&() const {
return static_cast<long&&>(nil);
}
};

int main() {
int &&a((S()));
return a;
}

is accepted by GCC, EDG and MSVC. But not in Clang:

error: no viable conversion from 'S' to 'int'

Online demo: https://gcc.godbolt.org/z/M7W3oYsGz

This is a slightly modified example from https://stackoverflow.com/q/79885636/7325599
</details>