Integrated: 8043226: Better diagnostics for non-applicable type annotations

[Liam Miller-Cushon]

On Fri, 10 Nov 2023 01:21:28 GMT, Liam Miller-Cushon <cushon at openjdk.org> wrote:

> Hi,
> 
> Please consider this improvement to diagnostics on inadmissable type annotations.
> 
> [JDK-8057683: clarify error messages trying to annotate scoping](https://bugs.openjdk.org/browse/JDK-8057683) is closely related to JDK-8043226 and I think could be made a duplicate of that bug. [JDK-8057683: improve ordering of errors with type annotations](https://bugs.openjdk.org/browse/JDK-8057683) is also closely related, and this PR partially fixes the issues described in that bug.
> 
> I have some notes on details of the proposed changes below.
> 
> ---
> 
> Currently javac reports 'scoping construct cannot be annotated' diagnostics for type annotations at locations where they are not admissable. 
> 
> As discussed in [JDK-8043226](https://bugs.openjdk.org/browse/JDK-8043226) and [JDK-8057683](https://bugs.openjdk.org/browse/JDK-8057683), the current language is unclear. The 'scoping construct' language was used in JSR-308 discussions but didn't end up in the final specification, JLS §9.7.4 talks about where annotations are 'admissable', and that language is mirrored in JVMS §4.7.20.2.
> 
> This change updates the diagnostics to state that type annotations 'not admissible at this location' and removed the reference to 'scoping constructs'. Additionally, the diagnostic now includes an explanation of a location in the type where annotations would be admissible, to make it easier to understand how to annotate qualified type names.
> 
> Before:
> 
> 
> test/langtools/tools/javac/annotations/typeAnnotations/failures/CantAnnotateScoping.java:38: error: scoping construct cannot be annotated with type-use annotation: @TA
>     @TA Outer.SInner osi;
>              ^
> 
> 
> After:
> 
> 
> test/langtools/tools/javac/annotations/typeAnnotations/failures/CantAnnotateScoping.java:38: error: type annotations are not admissible at this location: @TA
>     @TA Outer.SInner osi;
>              ^
>   (to annotate a qualified type, write Outer. at TA SInner)
> 
> 
> ---
> 
> Attribution currently assumes `@TA java.lang.Object` in `List<@TA java.lang.Object>` will be a type (not a package), and reports a resolution failure when it can't find a class named `java`.
> 
> This change modifies attribution to search for packages as well as types when resolving annotated types, and relies on the subsequent error checking for annotated types to report that type annotations are not admissible at that location.
> 
> This also improves the ordering of the diagnostic in the output, since attribution errors are report before type annotation validation errors in the l...

This pull request has now been integrated.

Changeset: 612b6896
Author:    Liam Miller-Cushon <cushon at openjdk.org>
URL:       https://git.openjdk.org/jdk/commit/612b6896d28cebf61ef024709ff3afb5e3ee0dde
Stats:     290 lines in 17 files changed: 35 ins; 49 del; 206 mod

8043226: Better diagnostics for non-applicable type annotations

Reviewed-by: vromero

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PR: https://git.openjdk.org/jdk/pull/16592