Alias type with different initialiser.

[Bastiaan Veelo via Digitalmars-d-learn]

On Monday, 13 February 2017 at 16:40:02 UTC, Daniel Kozak wrote:
> https://dlang.org/phobos/std_typecons.html#.Typedef

Thanks for the pointers. Both Typedef and Proxy create types that 
don't mix with the base type, which I want to the contrary. So I 
guess I'll go with

struct Initial(T, T val)
{
     private T _payload = val;
     alias _payload this;

     static Initial opCall(T v)
     {
         Initial s;
         s._payload = v;
         return s;
     }

     static T init()
     {
         return val;
     }
}

unittest
{
     alias Initial!(int, 1) int1;
     int1 i;
     assert(i == 1);
     int1 ii = 2;
     assert(ii == 2);
     assert(ii.init == 1);
     assert(int1.init == 1);

     void f(int val)
     {
         assert(val == 1);
     }
     f(i);

     int i0;
     assert(i0 == 0);
     i = i0;
     assert(i == 0);
     assert(i.init == 1);
     i0 = ii;
     assert(i0 == 2);
     assert(i0.init == 0);
}