compiler accepts incompatible method reference for Sam conversion

[Ali Ebrahimi]

Hi Remi,

On 7/13/11, Rémi Forax <forax at univ-mlv.fr> wrote:
> On 07/13/2011 06:01 AM, Ali Ebrahimi wrote:
>
> Hi Ali,
>
> ...
>> MethodHandle mh =
>> MethodHandles.lookup().findStatic(MethodHandleTest.class,
>> "sTest", MethodType.methodType(void.class,int.class,int.class));
>> MethodHandle smh = mh.asSpreader(Object[].class,
>> mh.type().parameterCount());
>>
>> smh.invoke(new Object[]{i,i});<===============crash
>>
>> main cause: mh.asSpreader
>>
>> I don't known this crash appears in jdkb147.
>
> What you want here is to use asCollector, not asSpreader.
> asSpreader requires that the method as already an object array
> and extract the value from it.

May be i'm wrong. but this code picked from MethodHandleProxies class

    public static
    <T> T asInterfaceInstance(final Class<T> intfc, final MethodHandle target) {
        final Method sm = getSingleMethod(intfc);
        if (sm == null)
            throw new IllegalArgumentException("not a single-method
interface: "+intfc.getName());
        MethodType smMT = MethodType.methodType(sm.getReturnType(),
sm.getParameterTypes());
        MethodHandle checkTarget = target.asType(smMT);  // make throw WMT
        checkTarget =
checkTarget.asType(checkTarget.type().changeReturnType(Object.class));
        final MethodHandle vaTarget =
checkTarget.asSpreader(Object[].class, smMT.parameterCount());
        return intfc.cast(Proxy.newProxyInstance(
                intfc.getClassLoader(),
                new Class[]{ intfc, WrapperInstance.class },
                new InvocationHandler() {
                    private Object getArg(String name) {
                        if ((Object)name ==
"getWrapperInstanceTarget")  return target;
                        if ((Object)name == "getWrapperInstanceType")
  return intfc;
                        throw new AssertionError();
                    }
                    public Object invoke(Object proxy, Method method,
Object[] args) throws Throwable {
                        if (method.getDeclaringClass() == WrapperInstance.class)
                            return getArg(method.getName());
                        if (method.equals(sm))
                            return vaTarget.invokeExact(args);
                        if (isObjectMethod(method))
                            return callObjectMethod(this, method, args);
                        throw new InternalError();
                    }
                }));
    }

and this results in this crash:
class MethodHandleTest{
...
public static void sTest(int x,int y){
     //   System.out.println("stest");
    }

  static interface Sam{
        void m(int x,int y);
    }
..
Sam sam = MethodHandleTest#sTest;
        sam.m(1,1);<==========

>
> In your example, the call to mh.asSpreader should return a runtime
> exception,
> I will investigate why it's not the case when I will be at my office :)
>
>> Best Regards,
>> Ali Ebrahimi
>
> regards,
> Rémi
>
>
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> mlvm-dev mailing list
> mlvm-dev at openjdk.java.net
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>
Best Regards,
Ali Ebrahimi