Maybe dumb question, but why is this giving me an ...

# announcements

[Onur]

Maybe dumb question, but why is this giving me an error?

[diesieben07]

Smart casts / type inference is simply not smart enough for that. The compiler cannot determine that filterNot will in fact return a Map with non-null values based on your filter function.

[gildor]

You can vote for this feature
https://youtrack.jetbrains.com/issue/KT-4734

[gildor]

For now you can do just unsafe cast or map key and values using mapNotNull