[type-annos-observers] Constraining type annotations to occur just before type

[Srikanth S Adayapalam]

Dear EG,

	We have a request from the Eclipse JDT team that JSR308 should
constrain/require the position of TYPE_USE annotations in declaration
modifiers, so that all TYPE_USE annotations must be placed at the end
of the modifiers list. (Or in other words, where a type annotation features
in a place a declaration annotation aka a SE7 annotation can also feature,
the language should mandate that they be placed immediately preceding
the type which they are annotating.

Example:

package jsr308.bug;

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

@Target(ElementType.TYPE_USE)
@interface NonNull { }

public class Bug {
		 @Deprecated @NonNull String s  = new @NonNull String();
		 @NonNull @Deprecated String s2 = new @NonNull String();  //
disallow
}

The rationale being:

A declaration like "@NonNull @Deprecated String" is hard to understand for
Java programmers. It doesn't make sense to allow the TYPE_USE annotation
to occur anywhere in the modifiers list. Unlike e.g. an ElementType.FIELD
annotation, a TYPE_USE annotation is not a general modifier of the
declaration.
A TYPE_USE annotation always belongs to the following type, so it should
also
be right in front of the type in the source.

The main concern is that from a language point of view, it doesn't make
sense to tear apart the TYPE_USE annotation and the type proper. This
was possible with annotations that abused other ElementTypes to
implement a restricted form of TYPE_USE annotations. But that doesn't
mean it needs to stay this way.

Thanks for considering this,
Srikanth.