hg: valhalla/valhalla: 8221545: [lworld] Preliminary support for alternate denotation of values and boxes

[Brian Goetz]

> 
> This was a request for LW2 - no more boxing. 

Right.  I was wondering whether we got there yet, or whether we’d just change the notation to start.

> We asked for the subtype relationship for both values and for arrays.

For arrays, the covariance rule: T <: U imples T[] <: U[] — should hold uniformly.  No need for special exceptions for value arrays.  Since

    V <: Object
and
    V? <: Object

then both V[] and V?[] are <: Object[].



> 
> For LW2 - we requested explicit checkcasts on attempts to narrow.
> 
> Agreed that there are discussions about where this is all going after LW2 before LW10.
> 
> thanks,
> Karen
> 
>> On Apr 16, 2019, at 9:24 AM, Brian Goetz <brian.goetz at oracle.com> wrote:
>> 
>> Is the conversion from V to V? still considered a boxing conversion, or is it a widening conversion now?  The language we (currently think we) want is 
>> 
>>  V <: V?
>> 
>> In the other direction, we’re still discussing whether the narrowing conversion is implicit or explicit.
>> 
>>> On Apr 16, 2019, at 8:09 AM, Srikanth <srikanth.adayapalam at oracle.com> wrote:
>>> 
>>> Notes:
>>> 
>>>   - This is the initial commit for supporting V? notation as an alternate for V.box
>>>   - The old .box and .val notation is not withdrawn yet and can still be used, but we should really move over to the new syntax as soon as possible.
>>>   - Existing javac tests have been replicated to use the V? syntax.
>>>   - VBC migration related work is not done yet.
>>>   - One issue that showed up in the parser implementation is the ambiguity at the point of seeing ?
>>>      in  v instanceof Type? exp: exp2; I have arranged for this to be processed as a conditional rather
>>>      than as denoting nullability.
>>>   - On a long value type name the ? suffix does not really stand out ATM, but I guess IDE colorcoding can address this issue.
>>>   - There is one failing test in the langtools suite (jdk/jshell/TypeNameTest.java) I will raise a follow up
>>>     ticket to address this.
>>>   - More testing is required and will be undertaken in the coming weeks. I request/encourage testing by the interested parties too.
>>> 
>>> Thanks!
>>> Srikanth
>>> 
>>> On 16/04/19 5:32 PM, srikanth.adayapalam at oracle.com wrote:
>>>> Changeset: bf52db1ad4ea
>>>> Author:    sadayapalam
>>>> Date:      2019-04-16 17:31 +0530
>>>> URL:       http://hg.openjdk.java.net/valhalla/valhalla/rev/bf52db1ad4ea
>>>> 
>>>> 8221545: [lworld] Preliminary support for alternate denotation of values and boxes
>>>> 
>>>> ! src/jdk.compiler/share/classes/com/sun/tools/javac/comp/Attr.java
>>>> ! src/jdk.compiler/share/classes/com/sun/tools/javac/comp/AttrContext.java
>>>> ! src/jdk.compiler/share/classes/com/sun/tools/javac/comp/Resolve.java
>>>> ! src/jdk.compiler/share/classes/com/sun/tools/javac/parser/JavacParser.java
>>>> ! src/jdk.compiler/share/classes/com/sun/tools/javac/tree/JCTree.java
>>>> ! src/jdk.compiler/share/classes/com/sun/tools/javac/tree/TreeCopier.java
>>>> ! test/langtools/tools/javac/valhalla/lworld-values/BogusIncompatibility.java
>>>> + test/langtools/tools/javac/valhalla/lworld-values/BoxValCastTest2.java
>>>> + test/langtools/tools/javac/valhalla/lworld-values/GenericsWithQuestion.java
>>>> + test/langtools/tools/javac/valhalla/lworld-values/GenericsWithQuestion.out
>>>> ! test/langtools/tools/javac/valhalla/lworld-values/InnerClassAttributeValuenessTest.java
>>>> + test/langtools/tools/javac/valhalla/lworld-values/IntercastTest2.java
>>>> + test/langtools/tools/javac/valhalla/lworld-values/LookupOnLoxTest2.java
>>>> ! test/langtools/tools/javac/valhalla/lworld-values/Point.java
>>>> 
>>> 
>> 
>