After answering this question I decided to dig deeper in the issue to find a minimal and replicable example with same error.
Let assume I have the following primary template and I would like to specialize it to std::vector as follows:
#include <vector>
#include <iostream>
template<typename T, typename T::value_type v>
struct foo;
template<typename T, T v>
struct foo<std::vector<T>, v> {
static constexpr T value = v;
};
int main() {
std::cout << foo<std::vector<int>, 32>::value << std::endl;
return 0;
}
GCC 7.1.0 won't compile the code above with -std=c++11, -std=c++14 or -std=c++1z neither the experimental GCC 8.0.0 but only with -std=c++11 or -std=c++14. They produce the same error output:
prog.cc:8:12: error: partial specialization 'struct foo<std::vector<T>, v>' is not more specialized than [-fpermissive]
struct foo<std::vector<T>, v> {
^~~~~~~~~~~~~~~~~~~~~~
prog.cc:5:12: note: primary template 'template<class T, typename T::value_type v> struct foo'
struct foo;
^~~
The presented example works well with GCC 6.3.0 and at least with GCC 4.5.4.
Could anyone confirm that this is a compiler bug? Is there any workaround with GCC 7.1.0 to make my example work?
