Strange behavior of g++ w/ concepts

strange_concepts.cpp

#include <stdio.h>
#include <vector>

#define D(v) printf("[%s:%d] %d\n", __PRETTY_FUNCTION__, __LINE__, v)

#if STRANGE_CONCEPTS
template <typename Src, typename Dst>
concept bool VectorSource()
{ return true; }

template <typename T = double >
class MeuTVector
{
    template < VectorSource<MeuTVector> X>
    MeuTVector &operator=(const X &x)
    { return *this; }
};
#endif

struct A {
    int v;
    A(int v): v(v) {}
    A(const A& a) { v = a.v; D(v); }
private:
    A(const A&& a) { v = a.v; D(v); }
    // A(const A&& a) = delete; // the fix
};

struct B: public A {
    using A::A;
};

int main() {
    std::vector<B> vec;
    vec.push_back(B(1));
    return 0;
}

Related to oneapi-src/oneDNN#196