On Sunday, 21 August 2016 at 19:42:08 UTC, Lodovico Giaretta
wrote:
On Sunday, 21 August 2016 at 19:29:26 UTC, Engine Machine wrote:
[...]
The problem of this code has nothing to do with aliases. They
work correctly. The problem is variable shadowing. In the
following code, Child has two x variables, one of which is only
accessible from a Parent reference, the other only from a Child
reference.
class Parent
{
int x;
}
class Child: Parent
{
int x; // this shadows Parent.x
int y;
}
void main()
{
Child child = new Child();
Parent parent = child;
child.x = child.y = 3;
parent.x = 2;
assert(child.x == 3);
assert((cast(Child)parent).x == 3);
assert((cast(Parent)child).x == 2);
assert(parent is child); // same object (remember that a
class is already a pointer);
assert(&parent != &child); // but there are two different
pointers on the stack (pointing to the same object)
}
You're right. I didn't realize that variables could be shadowed
in classes. Seems dangerous. D doesn't allow shadowing in a
normal context and gives an error so I don't know why it wouldn't
do that in classes. (since it wasn't giving an error I thought it
wasn't shadowing)
