RFR: 8280377: MethodHandleProxies does not correctly invoke default methods with varags [v2]

[Johannes Kuhn]

On Mon, 24 Jan 2022 23:03:49 GMT, Mandy Chung <mchung at openjdk.org> wrote:

>> The MethodHandle of a default method should be made as a fixed arity method handle because it is invoked via Proxy's invocation handle with a non-vararg array of arguments.  On the other hand, the `InvocationHandle::invokeDefault` method  was added in Java 16 to invoke a default method of a proxy instance.  This patch simply converts the implementation to call `InvocationHandle::invokeDefault` instead.
>
> Mandy Chung has updated the pull request incrementally with three additional commits since the last revision:
> 
>  - revert MethodHandlesProxiesTest change
>  - Add new regression test
>  - Should not perform access check on the interface as specified

Changes requested by jkuhn (Author).

src/java.base/share/classes/java/lang/invoke/MethodHandleProxies.java line 206:

> 204:                     if (isDefaultMethod(method)) {
> 205:                         // no additional access check is performed
> 206:                         return JLRA.invokeDefault(proxy, method, null, args);

Isn't the argument order `..., args, caller`?

src/java.base/share/classes/java/lang/reflect/ReflectAccess.java line 134:

> 132:             throws Throwable {
> 133:         return Proxy.invokeDefault(proxy, method, args, caller);
> 134:     }

What about other, non-jdk code that wishes to implement a similar thing - make a proxy for an arbitrary interface and handle default methods by invoking them?

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PR: https://git.openjdk.java.net/jdk/pull/7185