-0, IMO. I find the laziness benefit of unexplicit casts done for you in a few specific type cases (parameters that accept a single basic type only) a bit doubtful, especially next to the prospect of added compexity in the type system. While there possibly are cases it would be useful to someone, the maintenance / complexity costs of having this festure at least to me seem at a disconnect from the potential value.
(Not like in the order of adding reflection to a language lacking it, for instance, which would probably have merited that added burden.)
