Why do abstract class functions require definitions?

[Jakob Ovrum via Digitalmars-d-learn]

On Friday, 18 September 2015 at 13:18:23 UTC, Jacob Carlborg 
wrote:
> On 2015-09-16 12:36, Marc Schütz wrote:
>
>> Wouldn't the following behaviour be more useful as a default?
>>
>>      abstract class Foo {
>>          void bar1() { }     // non-abstract, obviously
>>          void bar2();        // abstract, because it's in an 
>> abstract class
>>                              // (different from now)
>>          extern void bar3(); // non-abstract, but defined 
>> externally
>>      }
>
> Currently "extern" has the meaning, at least on Windows, that 
> the symbol will be visible outside a dynamic library.

That's `export`.