​​Effekt Language: a research language with effect handlers and lightweight effect polymorphism written in #scala

-Lightweight Effect Polymorphism, No need to understand effect polymorphic functions or annotate them. Explicit effect polymorphism simply does not exist.
-Effect Safety, A type- and effect system that does not get into your way. Rely on a simple, yet powerful effect system that guarantees all effects to be handled.
- Effect Handlers, (Algebraic) effect handlers let you define advanced control-flow structures like generators as user libraries. Those libraries can be seamlessly composed.

https://effekt-lang.github.io/effekt-website/