Release 4.3.0 of the Checker Framework

[Suzanne Millstein]

We have released a new version of the Checker Framework.
The Checker Framework lets you create and/or run pluggable type checkers, in order to detect and prevent bugs in your code.

You can find documentation and download links at:
https://CheckerFramework.org/

Changes for Checker Framework version 4.3.0

Version 4.3.0 (2026-10-01)

User-visible changes

The new Modifiability Checker warns when a program might throw UnsupportedOperationException at run time because it calls a mutating method on a collection that does not support the method.

The new wpi2.sh script does whole-program inference, but requires buildfile edits.

Purity Checker:

• Renamed message keys purity.not.deterministic.X, purity.not.sideeffectfree.X, and purity.not.deterministic.not.sideeffectfree.X to purity.X.
• -AcheckPurityAnnotations issues warnings that it missed previously.

The Checker Framework runs under JDK 27 -- that is, it runs on a version 27 JVM.

The Checker Framework runs noticeably faster, due to performance tuning.

The HTML version of the manual has a new look. In addition to the single-page version, there is a multi-page version.

Changes for type system implementers

JavaParserUtil: moved DEFAULT_LANGUAGE_LEVEL, parseCompilationUnit(), parseStubUnit(), and parseExpression() into new class StaticJavaParserUtil.

Renamed AnnotatedTypes.innerMostType() to innermostComponentType().

Removed the unused method
WholeProgramInferenceScenesStorage.updateAnnotationSetInScene().

Methods that used to return (or accept) an IPair now use a record with meaningful component names.

Closed issues

#294, #1170, #1184, #1256, #1440, #1444, #1669, #2090, #2172, #2429, #2448, #2561, #2637, #2704, #2722, #2770, #2896, #2995, #3015, #3025, #3027, #3146, #3281, #3624, #4690, #4708, #4754, #5064, #5201, #6038, #6716, #6741, #6748, #6756, #6768, #6832, #6881, #7023, #7049, #7064, #7311, #7683, #8053, #8054, #8055, #8167, #8168, #8169, #8238, #8261, #8284.