It seems that only `when` and `->`is the new syntax, no? The arrow seems something that could be replaced with `=>`, but anyway, neither seems to be very restrictive with regards to future syntax. (After all they are only defined in a `case` context, so the can be reused for whatever future purpose outside.)

Plus it's a stage1 proposal, meaning it's far from serious.

Could you link the type annotation proposal, I can't find it.