Possible compiler bug

[Maurizio Cimadamore]

The problem is that Derived.Inner extends Base.Inner - which is a raw type.

Because of that, Derived.Inner does not inherit 'map' with type 
Map<Integer, Referenced> as you expect, but instead it inherits it raw 
(Map). Hence the error.

To fix, you need to replace the extends clause of Derived.Inner to say  
"extends Base<Derived.Inner>.Inner"

Maurizio

On 22/10/2019 12:11, Stefan Reich wrote:
> Hi, ok, the class relationships in this example are bit convoluted (I 
> have them for a reason in the original source code), but I still don't 
> see why it would fail to compile.
> import java.util.Map;
>
> class Referenced {
> }
>
> class Base<A extends Base.Inner> {
>
>      class Inner {
>          Map<Integer, Referenced>map;
>
>          void bla() {
>              Referenced r =map.get(0);
>          }
>      }
> }
>
> class Derivedextends Base<Derived.Inner> {
>      class Innerextends Base.Inner {
>          void bla() {
>              Referenced r =map.get(0);
>          }
>      }
> }
> The error message is:
>
> Referenced.java:20: error: incompatible types: Object cannot be 
> converted to Referenced
>             Referenced r = map.get(0);
>
> Why does the map suddenly lose its type parameters?
>
> Many greetings,
> Stefan
>
> -- 
> Stefan Reich
> BotCompany.de // Java-based operating systems
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