does cast make an lvalue appear to be an rvalue

[Daniel Davidson]

On Wednesday, 16 October 2013 at 17:16:39 UTC, Dicebot wrote:
>
> It works as it should. Make a mutable copy of t2 and pass it. 
> Or make foo() accept const. I can't imagine a single legitimate 
> use case for destroying type system in a way you want.

How do you propose to make a mutable copy *generically*?

I think a legitimate use would be the following. In the 
construction of S I want to use a T to construct an R. `this(...) 
immutable {}` prevents initialization of R in this case. Maybe 
immutable adorning `this()` should mean it is immutable upon the 
end of the construction, giving the initialization a chance to 
actually initialize. In the example below a better approach would 
be to have:

R createRFromT(ref const(T) t) pure {...}

but with what I'm using from phobos that is not possible.

------------------------------------------------

import std.conv;
import std.stdio;

struct R {
   int[] i;
   string[string] ss;
}

struct T {
   int[] i;
   string[string] ss;
}

struct S {
   R r;
   this(ref const(T) t) immutable {
     createRFromT(t, r);
   }
}

void createRFromT(ref const(T) t, ref R r) {
   //...
}

void main() {
   T t1;
   auto t2 = immutable T();
   auto s = immutable S(t2);
}