I love Kotlin, but it lacks unions.

This annotation processor takes a class annotated with @Union and returns a sealed class wrapper around it pretending to be an union

Example:

@Union(String::class,Bar::class,Double::class)
class Foo

Creates a: sealed class FooUnion

Creating a unionized type is as simple as

FooUnion.String(value)
FooUnion.Bar(value)
FooUnion.Double(value)

Getting a value from the union is as simple as calling .value

  val x : FooUnion = retrunsAFooUnion() 
  when(x.value){
    is String -> do()
    is Bar -> a()
    is Double -> thing()
  }

Type erasure happens so sorry about that. There's inline classes, maybe try with those. That's all.

Installing:

    implementation 'com.github.lotuslambda:0.3.3'
    annotationProcessor 'com.github.lotuslambda:unikons:0.3.3'
    kapt 'com.github.lotuslambda:unikons:0.3.3'