cast at call site problem

[Remi Forax]

On 04/03/2013 12:54 PM, Maurizio Cimadamore wrote:
> On 03/04/13 11:38, Anna Kozlova wrote:
>> What are reasons behind that then?
> Cast conversion rules are very complex - and defining an inference
> process that would satisfy them would make inference a lot more complex.
> It would also increase the surface of backward incompatibilities.

At the same time, this means that
   A a = foo();
can compile but
   A a = (A)foo();
can not compile which is really a bad semantics for a mainstream language.

I don't think there is a choice here,
even if we don't do inference on cast now,
the history shows that we will add this rule in the next release.
So better to that now because we are already introducing backward
compatibility hazard with the introduction of the complex algorithm that
to introduce backward compat. issue twice (between 7 and 8 and
betweeen 8 and 9).

>
> Maurizio

Rémi

>> -----Original Message-----
>> From: lambda-dev-bounces at openjdk.java.net
>> [mailto:lambda-dev-bounces at openjdk.java.net] On Behalf Of Maurizio
>> Cimadamore
>> Sent: Wednesday, April 03, 2013 11:54 AM
>> To: Anna Kozlova
>> Cc: lambda-dev at openjdk.java.net
>> Subject: Re: cast at call site problem
>>
>> On 01/04/13 15:59, Anna Kozlova wrote:
>>> The call foo(Collections.emptySet()); is much more clean I suppose. I
>>> just wonder why the redundant cast leads to compilation error.
>> As per spec EDR, a cast does not pass its type down to the expression being
>> converted. This means that the call to emptySet is typed with an Object
>> target; hence the error. If you remove the cast, the right target is used.
>>
>> Maurizio
>>> Thanks
>>>
>>>     
>>>
>>> From: paulus.benedictus at gmail.com [mailto:paulus.benedictus at gmail.com]
>>> On Behalf Of Paul Benedict
>>> Sent: Monday, April 01, 2013 4:51 PM
>>> To: Anna Kozlova
>>> Cc: lambda-dev at openjdk.java.net
>>> Subject: Re: cast at call site problem
>>>
>>>     
>>>
>>> I believe you want to write this:
>>> foo(Collections.<String>emptySet());
>>>
>>>     
>>>
>>> On Mon, Apr 1, 2013 at 9:48 AM, Anna Kozlova
>>> <Anna.Kozlova at jetbrains.com>
>>> wrote:
>>>
>>> Hello all,
>>>
>>> Is it a bug or is it an intentional behavior:
>>> This code compiles
>>> {code}
>>>        void foo(Set<String> s) {}
>>>
>>>        void bar() {
>>>            foo(Collections.emptySet());
>>>        }
>>> {code}
>>>
>>> but this code doesn't:
>>> {code}
>>>        void foo(Set<String> s) {}
>>>
>>>        void bar() {
>>>            foo((Set<String>)Collections.emptySet());
>>>        }
>>> {code}
>>>
>>> Lambda build 83.
>>>
>>> Thanks
>>> Anna
>>>
>>>
>>>
>>>
>>>     
>>>
>>>
>>>
>>>
>>
>> !DSPAM:35,515bfca371141724266025!
>>
>