I don’t see how that’s any worse than what we can do already with ‘val’ variables which is essentially what parameters are.
In any case I wasn’t suggesting that omitting the type in these circumstances should be compulsory, merely optional. If you’re a library writer, then you’d probably want to specify the type even if it was obvious from the default value.
As the rule for an acceptable default value would be the same as for ‘const val’ it would be easy to remember.