[fpc-devel] suggestion: virtual method co-variance

[Marco van de Voort]

I recently had to dive a bit into C++ again, and reconnected with a feature
I liked at first sight, the C++ covariance of virtual methods (changing the
return type of a overriden method to a descendant of the original type). 
Googling a bit it seems that some languages(C#) also seem to allow this for
parameters.  (not just return types)

I suddenly wondered why it was never proposed or talked about  for FPC,
since it seems such a nice feature.  Is there something particularly wrong
with it? 

To a certain degree it can be emulated with generics, but that it
requires a generic for every type, and must be prepared in the library code.