unimplemented abstract function compiles.

[Jacob Carlborg]

On 2018-08-12 19:29, Eric wrote:
> I thought it would work the same way as an interface (which must be 
> implemented by the direct sub class, otherwise compile error).
> But apparently it's possible to implement an abstract function anywhere 
> in the class hierarchy. That makes it, in this case, impossible to check 
> during compile time.

It will be checked during compile time if the class is referenced during 
compile time. In your example it's not.

The thing is that a library can provide an abstract class which is then 
subclassed and completely implemented by the user of the library. In 
that case you don't want an compile error when you're compiling the 
library but now using the class. One can argue that an abstract class 
always should be marked with "abstract" but that's not currently how the 
language is working.

-- 
/Jacob Carlborg