v1.7.21

Kotlin 1.7.21 is a patch release focused on stability, fixing 12 critical compiler bugs that caused runtime errors in JVM applications, particularly with inline functions, generic types, and nullable values. This release restores binary compatibility broken in 1.7.20 and removes the multiplatform alpha warning, signaling production readiness for cross-platform projects.

Highlights

• Fixed critical JVM compiler bugs causing VerifyError and NoSuchFieldError at runtime
• Resolved binary incompatible ABI change introduced in 1.7.20
• Fixed builder type inference regression affecting variable assignment
• Removed multiplatform (MPP) alpha stability warning for production readiness
• Fixed false positive NO_ELSE_IN_WHEN warnings with sealed classes in incremental compilation
• Improved Kotlin/Native deprecation messaging for freezing API