Custom parameters for property setters

My suggestion is allowing you to specify custom parameter types for property setters

Example:

var value: MutableFloat
   set(val: Float) { field = field.apply{setFloat(val)} }

This prevents having to create a function setValue(4f) and instead allows you to do value = 4f This would reduce a lot of the boiler plate from wrapper classes.

I understand this could create confusion about the variable type, however the developer should use it responsibly.

There is a keep, discussing something similar https://github.com/matejdro/KEEP/blob/private_public_property_types/proposals/private_public_property_types.md

You could create var value by MutableFloat(0f), with MutableFloat.getValue(): Float and MutableFloat.setValue(value: Float) methods to make it a proper delegate.