Fix false-negative when overriding method type-parameter bounds

[Suvrat1629]

Fixes #6864

• Added a method-level type-parameter bounds check in BaseTypeVisitor.java: inserted a call to checkTypeParameters() at the start of OverrideChecker.checkOverride() and implemented private boolean checkTypeParameters() to compare corresponding method type variables using the existing testTypevarContainment(...) helper and report failures via FoundRequired.
• Introduced a new diagnostic message key override.typeparam in messages.properties to report incompatible method type-parameter bounds.

[coderabbitai]

📝 Walkthrough

Walkthrough

This pull request addresses a false negative in override checking by introducing type parameter bounds validation. A new test file demonstrates the issue where a subclass overrides a method and modifies type parameter bounds to allow nullable elements. The framework's BaseTypeVisitor is enhanced with a checkTypeParameters method that validates type parameter compatibility between overriding and overridden methods before other override validation checks. A corresponding error message key is added to report incompatible bounds violations. Together, these changes ensure that methods with modified type parameter constraints are flagged during compilation.

🚥 Pre-merge checks | ✅ 2 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 50.00% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (2 passed)

Check name	Status	Explanation
Linked Issues check	✅ Passed	The PR successfully implements type-parameter bounds checking for method overrides [#6864], detecting incompatible type-parameter bounds and preventing false negatives.
Out of Scope Changes check	✅ Passed	All changes are directly scoped to implementing the type-parameter bounds check for method overrides, with no unrelated modifications.

_{✏️ Tip: You can configure your own custom pre-merge checks in the settings.}

✨ Finishing touches

• 📝 Generate docstrings

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Post copyable unit tests in a comment

Tip

🧪 Unit Test Generation v2 is now available!

We have significantly improved our unit test generation capabilities.

To enable: Add this to your .coderabbit.yaml configuration:

reviews:
  finishing_touches:
    unit_tests:
      enabled: true

Try it out by using the @coderabbitai generate unit tests command on your code files or under ✨ Finishing Touches on the walkthrough!

Have feedback? Share your thoughts on our Discord thread!

---

Thanks for using CodeRabbit! It's free for OSS, and your support helps us grow. If you like it, consider giving us a shout-out.

❤️ Share

• X
• Mastodon
• Reddit
• LinkedIn

_{Comment @coderabbitai help to get the list of available commands and usage tips.}

[coderabbitai]

Actionable comments posted: 1

🤖 Fix all issues with AI agents

In
`@framework/src/main/java/org/checkerframework/common/basetype/BaseTypeVisitor.java`:
- Around line 4169-4199: The diagnostic currently passes a zero-based index
(Integer.toString(i)) to checker.reportError; change this to a human-friendly
type-parameter identifier by using the type parameter's name from the
AnnotatedTypeVariable (e.g., obtain the declared name from subVar — e.g.,
subVar's element/simpleName or a getter such as
getName()/getTypeParameterElement().getSimpleName().toString()) and pass that
instead; if the name cannot be retrieved reliably, fall back to a 1-based index
(Integer.toString(i + 1)). Ensure this change is applied where
checkTypeParameters calls checker.reportError for the override.typeparam
message.