Kotlin 1.6.20 has been released. Highlights inclu...

# announcements

[Alina Dolgikh [JB]]

Kotlin 1.6.20 has been released.

Highlights include:
• Prototype of context receivers on JVM
• Definitely non-nullable types
• Performance improvements for JVM, Native, and JS
• Hierarchical structure support for multiplatform projects
Read more in the blog post.

[nkiesel]

I get the warning "type mismatch: value of a nullable type Optional<T> is used where non-nullable type is expected." in my code when compiling with 1.6.20 which I did not get with 1.6.10. Test code which will produce the same warning is:

fun <T> getTest(): Optional<T> { return Optional.empty() }

[nkiesel]

What is the actual issue here and how can I fix my code to avoid this warning? BTW: even fun <T> getEmpty2(): Optional<T> = Optional.empty<T>() produces the same warning, but fun <T> getList2(): List<T> = emptyList<T>() does not

[gildor]

It’s not the best place to report issues

[Alexey Belkov [JB]]

Thank you, I asked about this in https://youtrack.jetbrains.com/issue/KT-36770#focus=Comments-27-5966434.0-0

[denis.zharkov]

The issue is that Optional.empty returns Optional<T & Any> , i.e. its type argument is strictly not nullable and when it’s used as return expression for Optional<T> we’ve got type mismatch

The simplest (and probably the most expected) workaround is adding an upper bound to T

fun <T : Any> getTest(): Optional<T> = Optional.empty<T>()

Another option is using definitely not nullable types

fun <T> getTest(): Optional<T & Any> = Optional.empty<T>()