RFR 6388543: improve accuracy of source positions for AnnotationValue param of Messager.printMessage

[Liam Miller-Cushon]

Thanks for the feedback,

On Tue, Jan 3, 2017 at 9:00 PM, Jonathan Gibbons <
jonathan.gibbons at oracle.com> wrote:

> I guess I am slightly surprised by the proposed solution, as regards the
> choice of what it means to find a match. I have always assumed that any
> implementation would iterate over the element values of the annotation,
> looking for a value that is .equals to the given value, for some
> appropriate definition of AnnotationValue.equals.  It does not seem obvious
> to me that you should be searching within the individual element values for
> the match. I am also surprised that you might match for @B + 2; I would
> expect the annotation mirror to only match at the top level.   For example,
> assuming a "first one wins" policy, I would have expected @B + 2 to match
> the second annotation in the pair of annotations `@A(x = {1}, y = @B(2))
> @B(2)`


I thought the proposed approach was consistent with the existing handling
of AnnotationMirror. The overloads of matchAnnoToTree use reference
equality to find a matching AnnotationMirror, which could be either a
top-level or nested annotation on the element. So given `@A(x = {1}, y =
@B(2)) @B(2)`, passing an AnnotationMirror for @B to printMessage(...,
Element, AnnotationMirror) could match either appearance of @B depending on
which instance the argument was.

Is there a definition of AnnotationValue.equals that would be more
appropriate than reference equality? Value equality would be ambiguous for
e.g. `@A(x=1, y=1, z=1)` and @A + 1.

The motivation for supporting array elements was the same one mentioned in
the bug [1], which I've heard repeated elsewhere: for annotations
containing large array initializers it'd be helpful to place the caret at a
specific element instead of the start of the array.

Liam

[1]
https://bugs.openjdk.java.net/browse/JDK-6388543?focusedCommentId=12267020&page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#comment-12267020
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