Pattern matching for sealed enums

Previously if you wanted to check sealed enums types and use them, you had to do very ugly syntax for actually getting the variant instance:

auto out = tryGet();
when(out) {
    Result.Success -> {
        auto suc = out as Result.Success;
        looks::say("Success! ${suc.out.x}");

Now you don’t have to do all of this:

when(tryGet()) {
    Result.Success suc -> {
        looks::say("Success! ${suc.out.x}");

This is just syntax improvement, doesn’t change the generated code or anything, just helps the developer