Overzealous immutable and classes

[bearophile]

Jonathan M Davis:
> It's not terribly pretty, but apparently no one could come up with a 
> satistfactory way of doing it in the language itself given the syntax for 
> references. So, Rebindable!(T) is the solution.

A helper function can help:

import std.stdio, std.typecons, std.traits;

template isImmutable(T) {
    // I don't know if this works well in all cases
    const bool isImmutable = is(const(T) == T) || is(immutable(T) == T);
}

Rebindable!T rebindable(T)(T obj)
  if ((is(T == class) || is(T == interface) || isArray!T) && isImmutable!T) {
    return Rebindable!T(obj);
}

class Foo { int x, y; }

void main() {
    auto a = rebindable(new immutable(Foo(1, 2)));
    assert(a.sizeof == 4);
    a = new immutable(Foo(3, 4));
}


A template like isImmutable can be useful in Phobos...

Bye,
bearophile