<init>

Instructs the Kotlin compiler to treat annotated Java class as pure implementation of given Kotlin interface. "Pure" means here that each type parameter of class becomes non-platform type argument of that interface.

Example:

class MyList<T> extends AbstractList<T> { ... }

Methods defined in MyList<T> use T as platform, i.e. it's possible to perform unsafe operation in Kotlin:

MyList<Int>().add(null) // compiles

@PurelyImplements("kotlin.collections.MutableList")
class MyPureList<T> extends AbstractList<T> { ... }

Methods defined in MyPureList<T> overriding methods in MutableList use T as non-platform types:

MyPureList<Int>().add(null) // Error
MyPureList<Int?>().add(null) // Ok