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

[Eric McCorkle]

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?
>>
>