Another example sent to me by a fellow French guy,
final Deque<String> nestedDequeue = new ArrayDeque<>();
nestedDequeue.addFirst("C");
nestedDequeue.addFirst("B");
nestedDequeue.addFirst("A");
final List<String> nestedList = new ArrayList<>();
nestedList.add("D");
nestedList.add("E");
nestedList.add("F");
final List<Collection<String>> list = Stream.of(nestedDequeue,
nestedList).toList();
This one is cool because no 'var' is involved and using
collect(Collectors.toList()) instead of toList() solves the inference problem.
Rémi
----- Original Message -----
> From: "Stuart Marks" <stuart.ma...@oracle.com>
> To: "Remi Forax" <fo...@univ-mlv.fr>
> Cc: "core-libs-dev" <core-libs-...@openjdk.java.net>
> Sent: Tuesday, May 2, 2023 2:44:28 AM
> Subject: Re: The introduction of Sequenced collections is not a source
> compatible change
> Hi Rémi,
>
> Thanks for trying out the latest build!
>
> I'll make sure this gets mentioned in the release note for Sequenced
> Collections.
> We'll also raise this issue when we talk about this feature in the Quality
> Outreach
> program.
>
> s'marks
>
> On 4/29/23 3:46 AM, Remi Forax wrote:
>> I've several repositories that now fails to compile with the latest jdk21,
>> which
>> introduces sequence collections.
>>
>> The introduction of a common supertype to existing collections is *not* a
>> source
>> compatible change because of type inference.
>>
>> Here is a simplified example:
>>
>> public static void m(List<Supplier<? extends Map<String, String>>>
>> factories) {
>> }
>>
>> public static void main(String[] args) {
>> Supplier<LinkedHashMap<String,String>> supplier1 = LinkedHashMap::new;
>> Supplier<SortedMap<String,String>> supplier2 = TreeMap::new;
>> var factories = List.of(supplier1, supplier2);
>> m(factories);
>> }
>>
>>
>> This example compiles fine with Java 20 but report an error with Java 21:
>> SequencedCollectionBug.java:28: error: method m in class
>> SequencedCollectionBug
>> cannot be applied to given types;
>> m(factories);
>> ^
>> required: List<Supplier<? extends Map<String,String>>>
>> found: List<Supplier<? extends SequencedMap<String,String>>>
>> reason: argument mismatch; List<Supplier<? extends
>> SequencedMap<String,String>>>
>> cannot be converted to List<Supplier<? extends Map<String,String>>>
>>
>>
>>
>> Apart from the example above, most of the failures I see are in the unit
>> tests
>> provided to the students, because we are using a lot of 'var' in them so they
>> work whatever the name of the types chosen by the students.
>>
>> Discussing with a colleague, we also believe that this bug is not limited to
>> Java, existing Kotlin codes will also fail to compile due to this bug.
>>
>> Regards,
> > Rémi
