Type equality for values

Maurizio Cimadamore maurizio.cimadamore at oracle.com
Fri Aug 1 18:14:46 UTC 2014


If by 'realizable' you mean non-denotable, then there are several other 
places where inference infers non-denotable types:

<Z> Z choose(Z z1, Z z2) { ... }

choose(1, "");

So I wouldn't be too worried about it at this stage. Of course, in the 
long run this would be bad for the type-specialization story as I don't 
think we want to end up with an instantiated generic method where Z (or 
T in your example) is any.

Maurizio

On 01/08/14 10:10, Paul Govereau wrote:
> The following code is valid for reference types:
>
> class A<T> {
>     int x = 0;
>
>     <T,U> boolean foo(A<T> a, A<U> b) {
>         return (a == b);
>     }
> }
>
> However, I don't think this makes sense for value types. In the case 
> of reference types, the "top" is a realizable type, namely Object; 
> but, for values the "top" is not realizable?
>
> final __ByValue class A<T> {
>     final int x = 0;
>
>     <any T, any U> boolean foo(A<T> a, A<U> b) {
>         return (a == b);  // <<--- type error ??
>     }
> }
>
> Should this be a type error?
>
> Paul



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