Is a TYPE_USE annotation stored as such in a class file?

[Alex Buckley]

On 2/16/2023 3:18 PM, Laird Nelson wrote:
> On Thu, Feb 16, 2023 at 3:10 PM Alex Buckley <alex.buckley at oracle.com 
> <mailto:alex.buckley at oracle.com>> wrote:
> 
>     Looking at an annotation interface `A`'s @Target meta-annotation
>     absolutely does tell you all the places that the annotation `@A` may
>     appear. Everything about this is checked at compile time -- it has
>     to be deterministic.
> 
>     For example, from `@Target(TYPE_USE)`, you can deduce that `@A` may
>     appear on type uses, on class declarations, on interface declarations,
>     and on type parameter declarations.
> 
> 
> Let me put it a different way: what does annotating my annotation 
> with @Target({ ElementType.TYPE, ElementType.TYPE_PARAMETER, 
> ElementType.TYPE_USE }) accomplish that simply annotating it 
> with @Target({ ElementType.TYPE_USE }) does not?

It communicates intent more fully to a third-party checker system that 
inspects annotations throughout a program and may apply custom rules 
depending on the specified @Target. For example, a TYPE_USE-only 
annotation that appears on a class declaration is legal in the Java 
language, but may raise semantic issues for a checker, which can be 
addressed by adding TYPE to TYPE_USE in the @Target.

Alex