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

[Brian Goetz]

OK, thanks.  Hopefully the new rules will be simpler, as they lean more heavily on subtyping.  


> On Apr 16, 2019, at 10:18 AM, Srikanth <srikanth.adayapalam at oracle.com> wrote:
> 
> 
> This change set just introduces the new notation doing nothing new about inserting casts.
> I will go through the mails discussing this and follow up on a different change set.
> 
> Thanks
> Srikanth
> On 16/04/19 7:32 PM, Brian Goetz wrote:
>>> 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   - The old .box and .val notation is not withdrawn yet and can still be used, but we should really move over to the new syntax as soon as possible.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
>>>>>> 
>