Why can't we define re-assignable const reference variable?

[Steven Schveighoffer]

"Sergey Gromov" wrote
> Please, why invent new syntax ?
>
> const(T) t; // mutable ref to const T
> const{T t;} // const ref to const T, because of transitiviness
>
> This syntax even worked in one of the previous compiler versions!

Yes, this is one of the trials of Walter to see if he could get tail-const 
to work.

The problem is if T is not a reference/pointer (such as int).  Now:

const(T) t;
T t;

are equivalent, which is necessary to make that const system work.  To have 
some variable declared as const(T), and then allow assignment to that 
variable is completely inconsistent with the fundamental usage of 
parentheses.  If you have something defined as f(x), the entirety of x 
should be affected by f.  This is why that system was dropped, as it should 
have been.

-Steve