Joel suggested in private that if we don't consider reference types as 
dynamic in is_dynamic_type_internal, maybe the corresponding handling of 
reference types in resolve_dynamic_type_internal could be removed too.

I've tried to do this and this still triggers no regression on 
x86_64-linux. It's not surprising actually, since 
resolve_dynamic_type_internal does nothing on a type when 
is_dynamic_type_internal returns false for it.

So here's the updated patch. Thanks Joel for the idea! :-)

-- 
Pierre-Marie de Rodat