Error(s):

source_file.cpp: In function ‘int main()’:
source_file.cpp:18:7: error: no matching function for call to ‘B::B()’
     B b;                 // error C2512: 'B': no appropriate default constructor available
       ^
source_file.cpp:11:14: note: candidate: B::B(int)
     using A::A;
              ^
source_file.cpp:11:14: note:   candidate expects 1 argument, 0 provided
source_file.cpp:13:5: note: candidate: B::B(double)
     B(double x) : A() {}
     ^
source_file.cpp:13:5: note:   candidate expects 1 argument, 0 provided
source_file.cpp:9:7: note: candidate: constexpr B::B(const B&)
 class B : public A {
       ^
source_file.cpp:9:7: note:   candidate expects 1 argument, 0 provided
source_file.cpp:9:7: note: candidate: constexpr B::B(B&&)
source_file.cpp:9:7: note:   candidate expects 1 argument, 0 provided