Seems good to me. I’d like to have another name for this method:
+ private static Object invokeCustom(MethodHandle target, Object... args)
throws Throwable {
On Mar 4, 2014, at 12:00 PM, Vladimir Ivanov <vladimir.x.iva...@oracle.com>
wrote:
> http://cr.openjdk.java.net/~vlivanov/8036117/webrev.00/
> https://bugs.openjdk.java.net/browse/JDK-8036117
> 84 lines changed: 74 ins; 3 del; 7 mod
>
> I have to revert a cleanup I did for 8027827.
> MethodHandle.invokeWithArguments (and generic invocation) has unpleasant
> peculiarity in behavior when used with VarargsCollector. So,
> unfortunately, invokeWithArguments is not an option there.
>
> Looking at the API (excerpts from javadoc [1] [2]), the following
> condition doesn't hold in that case:
> "trailing parameter type of the caller is a reference type identical
> to or assignable to the trailing parameter type of the adapter".
>
> Example:
> target.invokeWithArguments((Object[])args)
> =>
> target.invoke((Object)o1,(Object)o2,(Object)o3)
> =/>
> target.invokeExact((Object)o1, (Object)o2, (Object[])o3)
>
> because Object !<: Object[].
>
> The fix is to skip unnecessary conversion when invoking a method handle
> and just do a pairwise type conversion.
>
> Testing: failing test case, nashorn w/ experimental features (octane)
>
> Thanks!
>
> Best regards,
> Vladimir Ivanov
>
> [1] MethodHandle.invokeWithArguments
> "Performs a variable arity invocation, ..., as if via an inexact invoke
> from a call site which mentions only the type Object, and whose arity is
> the length of the argument array."
>
> [2] MethodHandle.asVarargsCollector
> "When called with plain, inexact invoke, if the caller type is the same
> as the adapter, the adapter invokes the target as with invokeExact.
> (This is the normal behavior for invoke when types match.)
>
> Otherwise, if the caller and adapter arity are the same, and the
> trailing parameter type of the caller is a reference type identical to
> or assignable to the trailing parameter type of the adapter, the
> arguments and return values are converted pairwise, as if by asType on a
> fixed arity method handle.
>
> Otherwise, the arities differ, or the adapter's trailing parameter type
> is not assignable from the corresponding caller type. In this case, the
> adapter replaces all trailing arguments from the original trailing
> argument position onward, by a new array of type arrayType, whose
> elements comprise (in order) the replaced arguments."
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