Stream.flatMap signature is not correct

[Remi Forax]

On 12/01/2012 06:55 PM, Remi Forax wrote:
> On 12/01/2012 06:34 PM, Kevin Bourrillion wrote:
>> On Fri, Nov 30, 2012 at 8:44 PM, Remi Forax <forax at univ-mlv.fr 
>> <mailto:forax at univ-mlv.fr>> wrote:
>>
>>     Stream.flatMap is currently specified as:
>>
>>       <R> Stream<R> flatMap(FlatMapper<? super T, ? extends R> mapper);
>>
>>     but should be:
>>       <R> Stream<R> flatMap(FlatMapper<? super T, ? super R> mapper);
>>
>>
>> I don't understand.  If the mapper produces Numbers how can you 
>> return a stream of Integers?
>
> sorry, never send a mail Friday evening.
>
> Rémi
>

BTW, the problem of inference is still present:

Arrays.asList(Object.class, String.class).stream().flatMap(
     (block, clazz) -> { 
Arrays.asStream(clazz.getFields()).forEach(block); });   // doesn'tcompile

Arrays.asList(Object.class, String.class).stream().flatMap(
     (Block<? super Field> block, Class<?> clazz) -> { 
Arrays.asStream(clazz.getFields()).forEach(block); });  // Ok

Also note that it doesn't work with the signature (Block<Field>, 
Class<?>) because Block<Field> is a subtype of Block<? super Field>.
Rémi