interfaces :-(

[John Demme]

Walter Bright wrote:
> 
> "John Demme" <me at teqdruid.com> wrote in message
> news:dqae9p$2bhh$1 at digitaldaemon.com...
>> I'm not sure that I fully understand covariance either, but that's the
>> word
>> that Walter used to say why the following doesn't work.
>>
>> interface I
>> {
>>        I clone();
>> }
>>
>> class A: I
>> {
>>        A clone();
>> }
> 
> It'll work if you rewrite it as:
> 
>  interface I
> {
>        Object clone();
> }
> 
> class A: I
> {
>        A clone();
> }

Fine.  I'll give you a harder example:

interface Map (K,V)
{
        V get (K k);
        Map copy();
}

class HashMap (K,V): Map!(K,V)
{
        V get(K k) {}
        void rehash() {}
        HashMap copy() {}
}

... And I've actually run into this problem.

~John Demme