Minikotlin

4 hours ago

minikotlin is a compiler written from scratch in C that directly outputs WebAssembly GC bytecode, without relying on JVM, LLVM, Binaryen, or Gradle.
It compiles Kotlin source code (.kt files) into a running .wasm module entirely within the browser, with the compiler itself available as a WebAssembly module, eliminating the need for external toolchains.
The compiler supports full Kotlin features including open/override methods, interfaces, data classes, enums, sealed hierarchies with exhaustive when, smart-casting, nullable types with safe calls, generics, extension functions, and coroutines with real suspension via CPS.
Key compilation techniques include mapping each class to a WebAssembly GC struct type for property storage, implementing virtual dispatch via vtables and call_ref, compiling is checks to ref.test for smart-casting, and lowering coroutine suspension points into continuation closures without Asyncify or threads.
The system allows writing, compiling, and running Kotlin projects directly in the browser, with features like coroutineScope managing concurrent launches and delay suspending operations handled through host mechanisms like setTimeout.

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