A modern programming language that makes developers happier.

kotlinlang

I believe at the moment the Kotlin compiler is missing a single feature to guarantee pure functions to those that care.
The Kotlin compiler already is able to track effects with `suspend` and `@RestrictsSuspension` which enables users to encode functions that produce effects with `suspend`. This is awesome and is what we've built Arrow Fx upon.
What the Kotlin compiler is currently missing or maybe I failed to find a way is for users to disallow in their code bases function application when functions return `Unit` and they are not inside `suspend`.
With such a feature which could be activated via import, scoped annotations or simple compiler flag the Kotlin compiler would be able to a la carte guarantee function purity which is something not even scalac or other inclined FP langs in the JVM provide.
This would be opt-in and would not affect anyone that does not care about this feature. What are your thoughts on this potential feature. If there is interest I will submit a KEEP after <@UCLPFFZT3> and <@U0B8CNTJ8> submit KEEP-87 this week.