Default Exports and JS Compatibility

Sebastian and Márton host a special, audio-only episode where they discuss everything that’s new and noteworthy in the Kotlin 2.3 release. They touch on new language features like the unused return value checker and explicit backing fields, previously added features that became stable in this release, new APIs for time and UUID handling in the standard library, and improvements across all Kotlin platforms — from Native to Wasm and JS.

Resources:

• What’s new in Kotlin 2.3
• KotlinConf
• Golden Kodee Community Awards

Hosts:

• Sebastian Aigner – Website | Bluesky
• Márton Braun – Website | Bluesky

Timeline:
(0:00) Intro
(1:13) Nested type aliases (stable)
(1:46) Data-flow based exhaustiveness checks (stable)
(3:28) Return statements in expression bodies
(4:19) Unused return value checker (experimental)
(12:57) Explicit backing fields (experimental)
(18:51) Context-sensitive resolution (experimental)
(20:11) Clock and Instant in the standard library (stable)
(21:52) UUID v7 support and better parsing
(26:14) Java 25 bytecode
(26:36) Faster Native release builds
(27:45) Swift Export: enums and varargs
(29:08) C and Objective-C library import (beta)
(30:49) Apple target support changes
(32:15) Fully qualified names in Kotlin/Wasm
(34:10) New exception handling for wasmWasi
(35:32) Suspend function export to JS
(37:51) LongArray export to JS
(38:40) Unified companion object access in JS
(41:05) @JsStatic inside interfaces
(41:43) Default exports in JS
(43:45) Compose stacktraces for minified Android apps
(45:23) Breaking changes 🐜
(46:14) Documentation updates
(47:24) KotlinConf, Golden Kodees Awards
(48:11) Wrap-up