On Wednesday, 2 May 2012 at 22:38:36 UTC, Namespace wrote:
Other, shorter example:
[code]
import std.stdio, std.traits;
class A {
int val;
alias val this;
T opCast(T : Object)() {
writeln("FOO");
return to!(T)(this);
}
}
class B : A {
}
T to(T : Object, U : Object)(const U obj) {
return *(cast(T*) &obj);
}
T const_cast(T)(const T obj) {
return cast(T) obj;
}
void main () {
A a = new B();
a.val = 42;
writefln("a.val: %d", a.val);
B* b = cast(B*) &a;
writefln("*b.val: %d", b.val);
B b1 = to!(B)(a);
writefln("b1.val: %d", b1.val);
B b2 = cast(B) a;
writefln("b2.val: %d", b2.val);
const B b3 = cast(B) a;
B b4 = const_cast(b3);
}
[/code]
print:
alias_this_impl.d(24): Error: function
alias_this_impl.A.opCast!(B).opCast () is
not callable using argument types ()
alias_this_impl.d(44): Error: template instance
alias_this_impl.const_cast!(B) e
rror instantiating
I'm not very skillful in such "template" stories. Maybe someone
can help me?
Solved with
T const_cast(T)(const T obj) {
return to!(T)(obj);
}
But i think that there must exist a more nicer way to cast away
const, isn't there?
To cast away "const" with a simple cast to "T" fails (see my post
above), because i have no idea, how i can restrict my opCast. So
i have to convert it again with "to". Do some of you have any
ideas how i can restrict my opCast, so my const_cast doesn't
match it, e.g. with some template magic?
