A modern programming language that makes developers happier.

kotlinlang

Thought TL;DR: a way to "mixin" nullability annotations for existing java source code.  Longer discussion: The null-safety features of Kotlin and the java interop is amazing. Except that when calling java code from Kotlin, the nullability information is rarely available. What are people's thoughts on a feature to mixin the nullability information for return types on existing java interfaces/classes? The syntax and scoping needs thought, but could be inspired by the way extensions are declared.