Detect and warn on annotations directly on wildcard types

[msridhar]

See https://jspecify.dev/docs/spec/#recognized-type-use. I've seen this issue in real code, and developers may be confused if we just ignore, so I think we should give a warning. We should consider warning on other unrecognized locations for nullness annotations when in JSpecify mode.

Summary by CodeRabbit

Release Notes

• New Features

  • Added detection and reporting for invalid nullness annotations placed on wildcard type arguments in JSpecify mode.

• Tests

  • Added test coverage for wildcard annotation validation.

[msridhar]

This change is part of the following stack:

• Run inference for generic method calls nested inside receivers #1571
  • Improve handling of var-declared local variables #1573
    • Compensate for more annotations inserted by javac #1574
      • Enable test for issue 1500 and add comment #1560
        • Use ground target types when handling lambdas and method refs passed to generic methods #1575
          • Fix for unbounded wildcard passed to @NullUnmarked type variable #1577
            • Detect and warn on annotations directly on wildcard types #1579 ◀

_{Change managed by git-spice.}

[codecov]

Codecov Report

❌ Patch coverage is 83.33333% with 4 lines in your changes missing coverage. Please review.
✅ Project coverage is 88.19%. Comparing base (c183d49) to head (06f6580).

Files with missing lines	Patch %	Lines
...ava/com/uber/nullaway/generics/GenericsChecks.java	78.94%	2 Missing and 2 partials ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##             master    #1579      +/-   ##
============================================
- Coverage     88.20%   88.19%   -0.02%     
- Complexity     2938     2947       +9     
============================================
  Files           104      104              
  Lines          9819     9842      +23     
  Branches       1977     1982       +5     
============================================
+ Hits           8661     8680      +19     
- Misses          558      560       +2     
- Partials        600      602       +2     

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[lazaroclapp]

Makes sense! LGTM!

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Path: .coderabbit.yaml

Review profile: ASSERTIVE

Plan: Pro

Run ID: 69b5308b-848d-4b10-ab45-524e6703159f

📥 Commits

Reviewing files that changed from the base of the PR and between c183d49 and 9e0debd.

📒 Files selected for processing (4)

• nullaway/src/main/java/com/uber/nullaway/ErrorMessage.java
• nullaway/src/main/java/com/uber/nullaway/NullAway.java
• nullaway/src/main/java/com/uber/nullaway/generics/GenericsChecks.java
• nullaway/src/test/java/com/uber/nullaway/jspecify/WildcardTests.java

---

Walkthrough

This PR adds detection and reporting of nullness annotations (@Nullable, @NonNull) placed directly on wildcard type parameters in JSpecify mode, which is not a legal annotation location. A new error message type is defined, core detection logic is implemented in GenericsChecks, integration is wired through NullAway's AnnotatedTypeTreeMatcher interface, and comprehensive tests validate the behavior across valid and invalid wildcard annotation scenarios.

Possibly related PRs

• uber/NullAway#1361: Wildcard test reorganization in the same test suite where the new nullableOnWildcard test is added.
• uber/NullAway#1256: Refactored NullAway ↔ GenericsChecks integration patterns that align with the wiring approach used here.
• uber/NullAway#1558: Overlapping JSpecify wildcard nullness handling in GenericsChecks and WildcardTests.

Suggested reviewers

• lazaroclapp
• yuxincs

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 22.22% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title accurately summarizes the main change: detecting and warning on annotations placed directly on wildcard types, which is the primary focus across all modified files.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

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✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch annotation-on-wildcard

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