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8341779: [REDO BACKPORT] type annotations are not visible to javac plugins across compilation boundaries (JDK-8225377)
8340024: In ClassReader, extract a constant for the superclass supertype_index

Reviewed-by: vromero

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This backport pull request has now been updated with issue from the original commit.

At least one of the issues associated with this backport has a resolved CSR for a different version. As this means that this backport may also need a CSR, the csr label is being added to this pull request to signal this potential requirement. The command /csr unneeded can be used to remove the label in case a CSR is not needed.

Webrevs

• 02: Full - Incremental (aaf1c53e)
• 01: Full - Incremental (f4deb606)
• 00: Full (4c03b6ed)

/issue add JDK-8341779

@cushon This issue is referenced in the PR title - it will now be updated.

/issue add JDK-8340024

@cushon
Adding additional issue to issue list: 8340024: In ClassReader, extract a constant for the superclass supertype_index.

/approval JDK-8341779 request for backport. Fixes a bug in javac's implementation of TypeMirror to allow accessing type-use annotations on types loaded from class files.

Risk: The feature will be disabled by default behind an -XD flag, similar to 21u (see JDK-8360406). See also discussion in CSR JDK-8346471.

Testing: Tier 1 tests pass. The changes were backported to 21u and released in 21.0.8. The fix is also present in JDK 22 and newer releases.

Dependencies: If approved, the following related fixes should also be backported: JDK-8337795, JDK-8340024, JDK-8337998, JDK-8354893, JDK-8360406

@cushon
JDK-8341779: The approval request has been created successfully.

/approval JDK-8340024 request for backport. No-risk clean-up change for code hygiene, which also also included in JDK 21 as part of the JDK-8341779 redo, see https://git.openjdk.org/jdk21u-dev/pull/1671.

@cushon
JDK-8340024: The approval request has been created successfully.

Hi @cushon,
do we really need this in 17?
How far is the feature used in 21 by the community given the flag is needed? Is there any adoption?
Why can't users just go to 25 or 21?
It is not very desireable to have kind of hidden features in an update release.

Hi @cushon, do we really need this in 17? How far is the feature used in 21 by the community given the flag is needed? Is there any adoption? Why can't users just go to 25 or 21? It is not very desireable to have kind of hidden features in an update release.

Hi @GoeLin, here's the background I have:

Spring Boot 4 has adopted type use annotations for nullness (see this blog post). The post mentions using -XDaddTypeAnnotationsToSymbol with JDK 21. They also support JDK 17 as a baseline. So there are going to be some users of Spring Boot 4 who upgrade, but stay on JDK 17, and would benefit from the fix.

Another use-case is NullAway, which recommends the -XD flag if it is available, and supports JDK 17.

I appreciate the desire to not have hidden features. At the same time I think having this fix available even behind an -XD flag has some value to the ecosystem. There has been some additional recent usage of type annotations due to the JSpecify annotations, and if Null-Restricted and Nullable Types happens in a future release then we may be in a window where type annotations are most useful. I would like to try to make this fix available to parts of the ecosystem that aren't able to upgrade from 17 to 21 yet.

What do you think?

Hi @cushon
Thanks for the detailed explanation. I will approve it.
Please backport the follow-ups asap, especially the flag switching it off.

Thanks! I will aim to backport the the follow-ups close together with this change.