Points about language support for 292

Rémi Forax forax at univ-mlv.fr
Fri May 1 05:57:54 PDT 2009

Alex Buckley a écrit :
> Neal Gafter wrote:
>> On Thu, Apr 30, 2009 at 3:15 PM, Alex Buckley <Alex.Buckley at sun.com 
>> <mailto:Alex.Buckley at sun.com>> wrote:
>>     Neal: InvokeDynamic IS now a reference type. Regarding <..> to indicate
>>     return type for a dynamic call site, how does C# denote that?
>> It doesn't.  A dynamic invocation, from the point of view of C#, returns 
>> a value of type dynamic.  The hoped-for return type isn't encoded into 
>> the invocation.
> The utility of a Dynamic type is high. The utility of values of Dynamic 
> type is not high, in my view. Coin's support for 292 is limited, and 
> does not include general manipulation of non-Java objects in the Java 
> language. I respect that you believe the time has come for general 
> manipulation of non-C# objects in the C# language.
> Alex
even if I think that language developers should eat their own dog food.

Question: why do we need to use a type InvokeDynamic ?

The invokedynamic instruction is a function call,
so I propose to use a syntax more close to a function call,
something like:

$aDynamicFunction(arg1, arg2)

Now, the problem of the return type.
I propose the following rules:
 - if the dynamic call is the righ part of an assignation, the return type
   is the type of the lhs.
   int value = $aDynamicFunction(param1, param2)         // -> int

- if the dynamic call is prefixed by a cast, the return type is the
  type of the cast (note that this rule doesn't exist for generics)
  (double)$aDynamicFunction(param1, param2)         // -> double

- else the return type is Object.


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