Question

I’m trying to understand the new C++ 11 features; more specifically, the reference qualifiers (one of which) restricts the assignment onto rvalues. But for some reason I can’t get this code to work. The errors I get arise when I assign the A object a to the lvalue x ( a = x ).

prog.cpp:5:47: error: expected initializer before '&' token
prog.cpp: In function 'int main()':
prog.cpp:15:9: error: no match for 'operator=' in 'a = x'
prog.cpp:3:10: note: candidate is: A& A::operator=(const A&)

struct A {

   template <typename T> auto operator = (T) & -> A & {
       return *this;
   }

};

int main() {

   A a;

   int x = 4;

   a = x;

}

The code works when I take the reference qualifier out. What could I be doing wrong?

Answer 1

Seems you’re using GCC. Ref-qualifiers are currently only supported by Clang 3.1+. Your code compiles perfectly fine with that.