Confirm bug in java.lang.reflect.Proxy wrt static methods in interfaces

[mandy chung]

Your contribution is welcome and I can sponsor it.

Mandy

On 10/2/17 1:44 PM, Eric McCorkle wrote:
> You beat me to it :D
>
> I will see if I can fix it myself (though it's been a some time since I
> committed any changes).
>
> On 10/02/2017 16:39, mandy chung wrote:
>> FYI. I created https://bugs.openjdk.java.net/browse/JDK-8188240 for this
>> issue.
>>
>> Mandy
>>
>> On 10/2/17 1:33 PM, mandy chung wrote:
>>> I believe it is a bug.   To invoke a static method in the proxy
>>> interface, it will have to do "I1.foo()" or "I2.foo()".  It won't
>>> invoke through the proxy object, i.e. it's not interceptible. Even
>>> creating a proxy for I1, the generated proxy class includes an
>>> instance method named "foo" and no static method is generated in the
>>> proxy class.
>>>
>>> Mandy
>>>
>>> On 10/2/17 11:44 AM, Eric McCorkle wrote:
>>>> Hello everyone,
>>>>
>>>> A colleague of mine discovered what seems to be a bug in
>>>> java.lang.reflect.Proxy#newProxyInstance.  I'd like to confirm that this
>>>> is indeed incorrect behavior before I go and fix it.
>>>>
>>>> Consider the following two interfaces:
>>>>
>>>> interface I1 {
>>>>     static I1 foo() {
>>>>       return null;
>>>>     }
>>>> }
>>>>
>>>> interface I2 {
>>>>     static I2 foo() {
>>>>       return null;
>>>>     }
>>>> }
>>>>
>>>> JLS 9.4.1 states that static methods are not inherited in interfaces,
>>>> thus it should be perfectly legal to define some class which inherits I1
>>>> and I2.
>>>>
>>>> The following proxy creation fails:
>>>>
>>>> public class ProxyBug {
>>>>     public static void main(String... args) {
>>>>       I2 i2 =(I2)Proxy.newProxyInstance(
>>>>                    ClassLoader.getSystemClassLoader(),
>>>>                    new Class[] {I1.class, I2.class},
>>>>                    new InvocationHandler() {
>>>>                      @Override
>>>>                      public Object invoke(Object proxy,
>>>>                                           Method method,
>>>>                                           Object[] args)
>>>>                        throws Throwable {
>>>>                        return null;
>>>>                      }
>>>>                    });
>>>>     }
>>>> }
>>>>
>>>> The exception generated is as follows:
>>>>
>>>> Exception in thread "main" java.lang.IllegalArgumentException: methods
>>>> with same signature foo() but incompatible return types: [interface I1,
>>>> interface I2]
>>>>      at sun.misc.ProxyGenerator.checkReturnTypes(ProxyGenerator.java:712)
>>>>      at
>>>> sun.misc.ProxyGenerator.generateClassFile(ProxyGenerator.java:461)
>>>>      at
>>>> sun.misc.ProxyGenerator.generateProxyClass(ProxyGenerator.java:339)
>>>>      at java.lang.reflect.Proxy$ProxyClassFactory.apply(Proxy.java:639)
>>>>      at java.lang.reflect.Proxy$ProxyClassFactory.apply(Proxy.java:557)
>>>>      at java.lang.reflect.WeakCache$Factory.get(WeakCache.java:230)
>>>>      at java.lang.reflect.WeakCache.get(WeakCache.java:127)
>>>>      at java.lang.reflect.Proxy.getProxyClass0(Proxy.java:419)
>>>>      at java.lang.reflect.Proxy.newProxyInstance(Proxy.java:719)
>>>>      at ProxyBug.main(ProxyBug.java:19)
>>>>
>>>> So it would seem that newProxyInstance is incorrectly including static
>>>> methods in its check for incompatible return types.
>>>>
>>>> Can I get someone from core-libs to confirm that this is not intended
>>>> before I file a bug and start on the fix?