On Sun, 27 Dec 2009 19:02:23 -0500, TM <ith...@therefore.iam> wrote:
Hello,
I was dealing with delegates when I found that the const correctness of
the this pointer was 'lost' when accessing a member function of a class
through a temporary delegate.
Here is an example:
class A{
void f () {}
}
const A a = new A;
a.f() //error, this is normal.
auto g = &a.f;
g(); //no error. Is this normal ?
I may be wrong, but it seems to me that as the const property of the
this pointer is linked to the instance of the class (here 'a'), the
delegate 'g' should contain a const pointer to A (because 'a' is const).
More generally, I seems that there is no management of the const
correctness of the frame pointer of a delegate in D2
What about adding the const keyword for delegates, as we do for methods
? The const property of the delegate's frame pointer would be part of
its type.
Example:
void f()
{
int x;
void g() const {
x ++; //would produce an error since the type of g is [void
delegate() const]
}
}
Any thoughts about this ?
This might be a difficult thing to fix, but it definitely *definitely*
needs to be fixed. The problem is that a delegate stores a function
pointer and a context pointer. However, it does not type the context
pointer. For example, if you do this:
import std.stdio;
class A
{
void f() const {}
}
void main()
{
const A a = new A;
a.f();
auto g = &a.f;
writefln("%s", typeof(g).stringof);
}
You will get this:
void delegate()
The this pointer is hidden, and so is it's const decoration. I would
expect to see:
void delegate() const
I'll file a bugzilla request for this.
-Steve
