Created attachment 29417 [details]
Minimal reproducible testcase

$ g++-snapshot --version
g++-snapshot (Debian 20130209-1) 4.8.0 20130209 (experimental) [trunk revision 195917]

$ cat main.cpp 
struct foo {
    explicit foo(int&&) {}
};

struct bar: private foo {
    using foo::foo;
};

int main()
{
    bar b { 42 };
}

$ g++-snapshot -Wall -std=c++11 main.cpp 
main.cpp: In constructor 'bar::bar(int&&)':
main.cpp:6:16: error: cannot bind 'int' lvalue to 'int&&'
     using foo::foo;
                ^
main.cpp:2:14: error:   initializing argument 1 of 'foo::foo(int&&)'
     explicit foo(int&&) {}
              ^
main.cpp: In function 'int main()':
main.cpp:11:16: note: synthesized method 'bar::bar(int&&)' first required here 
     bar b { 42 };