Kinds of containers

[TheFlyingFiddle via Digitalmars-d]

On Saturday, 24 October 2015 at 09:22:37 UTC, Jacob Carlborg 
wrote:
> Can these be implemented by the user just declaring a regular 
> container as immutable? The implement will recognize if it's 
> declared as immutable and adapt.

How can a type know it's qualifier?

struct Container(T)
{
    //.... access qualifier somehow do stuff with it
}

alias SM  = Container!int;
alias SIM = immutable Container!int;

It was my understanding that S!int only gets instantiated one 
time here? Or does the compiler instantiate (immutable S!int) and 
(S!int)? Or were you thinking of something else?