reference variables don't exist, but can simulate them

[NonNull]

Using gdc (Ubuntu 8.4.0-1ubuntu1~18.04) 8.4.0
Please criticize:

struct refer(T) {
   T* ptr;
   this(ref T x) { ptr = &x; }
   ref T _() { return *ptr; }
   alias _ this;
   string toString() { import std.conv; return to!string(*ptr);  }
}

This will make a reference variable (simulation). [ toString() is 
just for writeln. ]

void main() {
     int i = 100;
     refer!int j = i;
     j = 3;
     writeln(i);
     i = 100;
     writeln(j);
     j += 3;
     writeln(i);
     refer!int k = j;
     writeln(k);
}

And a refer!int can be returned as it is just a value. Returning 
one that contains a pointer to a local variable leads to a 
compilation error.