Navigate from ClassInfo to TypeInfo

[Fawzi Mohamed]

On 2009-04-16 12:18:31 +0200, davidl <davidl at nospam.org> said:

> 在 Wed, 15 Apr 2009 13:56:20 +0800，Daniel Keep  
> <daniel.keep.lists at gmail.com> 写道:
> 
>> 
>> 
>> davidl wrote:
>>> 在 Wed, 15 Apr 2009 10:14:42 +0800，Jarrett Billingsley
>>> <jarrett.billingsley at gmail.com> 写道:
>>> 
>>>> 2009/4/14 davidl <davidl at nospam.org>:
>>>>> 
>>>>> Send this object to vararg func, and retrieve the TypeInfo there and
>>>>> return?
>>>> 
>>>> No.  The typeinfo passed to vararg functions is also determined at
>>>> compile-time.
>>> 
>>> so it's a bug?
>>> 
>>> I think vararg funcs always want the real typeinfo of the object
>> 
>> No, they get the typeinfo of what they're passed.
>> 
>>> class A {}
>>> class B : A {}
>>> 
>>> void foo(...) {}
>>> 
>>> void bar(A a) { foo(a); }
>>> 
>>> void main()
>>> {
>>>     scope b = new B;
>>>     bar(b);
>>> }
>> 
>> bar cannot possibly know what the "real" TypeInfo of a is.  But that
>> doesn't matter because it's passing an A with A's TypeInfo.  And if foo
>> is maybe interested in Bs, then it can just try to up-cast.
>> 
>>   -- Daniel
> 
> If the caller only sends the object typeinfo, then the vararg typeinfo 
> is  so limited to be valid for primitives. It's definitely useless for 
> classes  cases.

For people interested in runtime introspection tango.core.RuntimeTraits 
might be interesting.

Fawzi