RFR: 8344159: Add lint warnings for unnecessary warning suppression [v4]

[Erik Joelsson]

On Wed, 22 Oct 2025 15:21:43 GMT, Archie Cobbs <acobbs at openjdk.org> wrote:

>> This PR adds a new compiler warning for `@SuppressWarnings` annotations that don't actually suppress any warnings.
>> 
>> Summary of code changes:
>> 
>> * Add new warning and associated lint category `"suppression"`
>> * Update `LintMapper` to keep track of which `@SuppressWarnings` suppressions have been validated ¹
>> * Update `Log.warning()` so it validates any current suppression of the warning's lint category in effect.
>> * Add a new `validate` parameter to `Lint.isEnabled()` and `Lint.isSuppressed()` that specifies whether to also validate any current suppression.
>> * Add `Lint.isActive()` to check whether a category is enabled _or_ suppression of the category is being tracked - in other words, whether the warning calculation needs to be performed. Used for non-trivial warning calculations.
>> * Add `-Xlint:-suppression` flags to `*.gmk` build files so the build doesn't break
>> 
>> ¹ The suppression of a lint category is "validated" as soon as it suppresses some warning in that category
>
> Archie Cobbs has updated the pull request with a new target base due to a merge or a rebase. The pull request now contains 133 commits:
> 
>  - Merge branch 'master' into JDK-8344159 to fix conflict.
>  - Merge branch 'master' into JDK-8344159 to fix conflict.
>  - Merge branch 'master' into JDK-8344159 to fix conflicts.
>  - Add clarifying comment.
>  - Merge branch 'master' into JDK-8344159
>  - Change inner class name to avoid shadowing superclass name.
>  - Add a couple of code clarification comments.
>  - Refactor test to avoid requiring changes to TestRunner.
>  - Remove unnecessary -Xlint:-suppression flags.
>  - Minor cleanups.
>  - ... and 123 more: https://git.openjdk.org/jdk/compare/a1be2979...f2b75547

Build changes still look good.

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Marked as reviewed by erikj (Reviewer).

PR Review: https://git.openjdk.org/jdk/pull/25167#pullrequestreview-3396264627