Containing annotation type with TYPE_USE target

[Alex Buckley]

Here is a javac bug at the intersection of repeating annotations and 
type annotations.

The following program doesn't compile (JDK8 b116) because javac thinks 
the containing annotation type (FooContainer) is applicable to more 
targets than the repeatable annotation type (Foo):

---
import java.lang.annotation.ElementType;
import java.lang.annotation.Repeatable;
import java.lang.annotation.Target;

@Target({ElementType.TYPE_USE})
@Repeatable(FooContainer.class)
@interface Foo {}

@Target({ElementType.TYPE, ElementType.TYPE_USE})
@interface FooContainer {
   Foo[] value();
}
---

In fact, the program should compile. The kinds of program element where 
FooContainer is applicable - type uses and type declarations - are the 
same kinds where Foo is applicable, which means FooContainer is a 
legitimate containing type for Foo. (TYPE_USE is logically a superset of 
TYPE, so the TYPE target on FooContainer is redundant.)

Here is the relevant text for JLS8 9.6.3 "Repeatable Annotation Types" 
which is aware of the TYPE_USE construct from JSR 308:

---
T is applicable to at least the same kinds of program element as TC 
(§9.6.4.1). Specifically, if the kinds of program element where T is 
applicable are denoted by the set m1, and the kinds of program element 
where TC is applicable are denoted by the set m2, then each kind in m2 
must occur in m1, except that:

- If the kind in m2 is java.lang.annotation.ElementType.ANNOTATION_TYPE, 
then at least
one of java.lang.annotation.ElementType.ANNOTATION_TYPE or
java.lang.annotation.ElementType.TYPE or
java.lang.annotation.ElementType.TYPE_USE must occur in m1.

- If the kind in m2 is java.lang.annotation.ElementType.TYPE,
then at least one of java.lang.annotation.ElementType.TYPE or
java.lang.annotation.ElementType.TYPE_USE must occur in m1.
---

Alex