I've been dealing with this same issue in Rust, and I think there is definitely a middle ground to be had.

In the first example, it's trivial to add uint32 and uint64, and store the result as a uint64. No information is lost at all in that operation. This generalizes to any combination of integral types, where [u]int{x} + [u]int{y} = [u]int{max(x, y)}. It's inexplicable to me why a language wouldn't allow these loss-less operations to be implicit.

The other two operations don't have a clear answer, so it makes perfect sense to require an explicit cast in those cases.