Is there a way to re-use the kotlin serialization feature to deserialize an object from a Map<String,Any?> ? Since I'm using data classes I can't use delegated properties.

can you convert the Any in there to Strings ? then yes you can probably deserialize those but without more info you will not get around making some kind of instanceof check and when/switch statements

My intention is to create the objects from a map already containing the (matching) native types (e.g. a number is already an Int/Double etc.) or other serializable objects. If anything does not match, an exception is fine.

You can use kotlin no-arg plugin, it will generate a synthetic no-arg constructor which should allow Firebase to do its thing.

For future reference: I managed to do what I want by leveraging the automatically created serializers of

@Serializable

objects with a custom

Decoder

. While this is not strictly serialization/deserialization but rather a transform it could be very useful for a variety of further uses. If there is interest, I could clean it up and put it on github