Bug ID: JDK-8006267 InterfaceMethod_ref should allow invokestatic and invokespecial

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JDK 8	Other
8Fixed	hs25Fixed

Per the lambda spec, hotspot now allows interface methods to be static.  
Per the upcoming version (0.6.2) of the lambda spec, these static interface methods are InterfaceMethod_ref.  Currently, classFileParser.cpp disallows invokestatic (and invokespecial) calls to InterfaceMethod_ref.  Thus these methods cannot be called.

Below describes the spec:

...keep the current restrictions on Methodref_info, and the instruction arguments will be expected as follows:

invokevirtual(Methodref_info)
invokeinterface(InterfaceMethoref_info)
invokespecial(Methodref_info or InterfaceMethodref_info)
invokestatic(Methodref_info or InterfaceMethodref_info)

-----
Please find attached a proposed patch to accomplish this.  It is unknown if restrictions will need to be put elsewhere in the VM to compensate for this widening.

It was my understanding that static interface methods are now deferred to Java 9, or at least post Java 8 ?
09-03-2013
None of the above examples include static methods. Those can be declared directly in Java source: ----- interface I { static int m() { return 12; } } class Test { public static void main(String... args) { System.out.println(I.m()); }} ----- Also worth noting that class files generated by something other than javac may generate arbitrary private methods in the interface, invokable via invokespecial. (In contrast, javac only uses them to encode lambdas, I think.)
08-03-2013
And here are two more tests Robert Field and Dan Smith have provided me - for the record class PS implements I { public static void main(String[] args) { System.err.printf("pow: %s\n", (new PS()).thing().f(0.5)); } } interface I { default FI thing() { return (x) -> x * x; } } interface FI { Double f(Double x); } ========== interface Dog { default void bark() { System.out.println("Woof"); } } class Foo implements Dog { public Foo() { Dog.super.bark(); } }
06-03-2013
Example one: private static interface method interface I { default void m() { Runnable r = ()-> { System.out.println("Hello"); }; //the plan is to generate a private static synthetic method for translating this lambda away } } Example two: private instance interface method interface Sup { default void m() { } } interface I extends Sup { default m() { Runnable r = ()-> { Sup.super.m() }; //the plan is to generate a private instance synthetic method for translating this lambda away } }
06-03-2013
It appears that changes also need be made to java.lang.invoke.* classes to facilitate the proposed change. Not sure if this effect was also considered while proposing the change.
21-02-2013
There will need to be a separate bug for the JDK changes. I'm wondering if core reflection also needs to be updated to handle these new kinds of methods?
21-02-2013

Relates :	JDK-8013875 - Incorrect vtable index being set during methodHandle creation for static methods
Relates :	JDK-8014059 - JSR292: Failed to reject invalid class cplmhl00201m28n
Relates :	JDK-8016764 - JVM does not prohibit invokespecial in c.f.v 51.0 that invokes default interface method in c.f.v. 52.0
Relates :	JDK-8011311 - Lambda: Support Private concrete methods in interfaces
Relates :	JDK-8007297 - [pack200] allow opcodes with InterfaceMethodRefs
Relates :	JDK-8008687 - MethodHandle code: allow static and invokespecial calls to interface methods
Relates :	JDK-8016764 - JVM does not prohibit invokespecial in c.f.v 51.0 that invokes default interface method in c.f.v. 52.0
Relates :	JDK-8008689 - test reflective modeling and calling of static methods on interfaces

JDK-8012961 :	Do not restrict static interface methods to be private - Resolved
JDK-8013875 :	Incorrect vtable index being set during methodHandle creation for static methods - Resolved