[type-annos-observers] Desugaring of anonymous classes

[Srikanth S Adayapalam]

> From: Alex Buckley <alex.buckley at oracle.com>
> Sent by: type-annotations-spec-experts-bounces at openjdk.java.net
> 
> Mike, Srikanth,
> 
> Returning to this topic, there are two scenarios where I would like your 

> comments:

Hi Alex,

First of all, apologies for the delay in responding.

> 1. Type annotation in 'new' expression for anonymous class
> 
> Consider this code:
> 
>    @Retention(RetentionPolicy.RUNTIME)
>    @Target(ElementType.TYPE_USE)
>    @interface X {}
> 
>    class C { void m() { new @X Foo() {}; } }
> 
> The @X annotation is stored as a target_type=CLASS_EXTENDS structure in 
> the RuntimeVisibleTypeAnnotations attribute of Foo$1.class. That's fine.

I am fine with this behavior, though as there is nothing in the latest
specification that calls for such a behavior, we should make sure to
spell this out, if this is the behavior we want.

> The @X annotation is not stored as a target_type=NEW structure in the 
> RuntimeVisibleTypeAnnotations attribute of m's method_info in C.class. 
> That's an oversight by javac, especially since the first mail in this 
> thread said javac copied type annotations "to the class declaration and 
> to its instantiation (new expression)".

At the moment, eclipse compiler's behavior is the exact opposite of what
you mention as javac's behavior. We emit the annotation with target_type
being NEW but not target_type=CLASS_EXTENDS.

> 2. Declaration annotation for anonymous class in 'new' expression
> 
> Take the code above and change the annotation type's target to be TYPE:
> 
>    @Retention(RetentionPolicy.RUNTIME)
>    @Target(ElementType.TYPE)
>    @interface X {}
> 
>    class C { void m() { new @X Foo() {}; } }
> 
> The @X annotation is stored in the RuntimeVisibleAnnotations structure 
> of Foo$1.class. This is a neat trick, since anonymous class declarations 

> could not be annotated in SE 7, but it is irregular because annotations 
> on declarations traditionally appear as modifiers. If a 'new' expression 


This is more irregular than neat and I would be inclined to suggest that
we pull back such behavior. At the moment again, as you call out there is
nothing in the specification that calls for such a behavior.

Srikanth,