Re: alias this & cast

[andre via Digitalmars-d-learn]

I am not sure. b is C but everything not in super class B is 
hidden.
Using cast I can cast b to a full C.

The cast "cast(C)b" has the same information about b like the 
cast "cast(A)b": The memory area of b knows compatitibility to C 
and also the alias.

For me, using alias this, the object b has 3 represenations: A, B 
and C. It is a matter of steps.

Kind regards
André

On Thursday, 11 September 2014 at 11:53:30 UTC, Daniel Kozak via 
Digitalmars-d-learn wrote:
V Thu, 11 Sep 2014 11:40:05 +0000
andre via Digitalmars-d-learn 
<digitalmars-d-learn@puremagic.com>
napsáno:

Hi,

I am 80% sure, the failing assertion is correct but please 
have a look.

No it is not

assert(cast(A)cast(C)b); // this is OK

b is B so it does not know about having alias to A;

Second assertion fails.

Kind regards
André

class A{}

class B{}

class C : B
{
        A a;
        alias a this;
        
        this()
        {
                a = new A();
        }
}

void main()
{
        B b = new C();

        // OK
        assert(cast(C)b);
        
        // fails
        assert(cast(A)b);       
}