Move class "extends"/implements/with to a new line when generics take a lot of space

[rrousselGit]

Hello!

Consider the following code I dealt with earlier:

abstract class StreamNotifierProviderBase<
        NotifierT extends AsyncNotifierBase<T>,
        T> extends ProviderWithNotifier<AsyncValue<T>, NotifierT>
    with FutureModifier<T> {
// ...
}

With the way extends and generics are mixed up, this is fairly unreadable.
It's very hard with a quick glance to know what this class extends exactly.

I propose formatting such cases like the with:

abstract class StreamNotifierProviderBase<
        NotifierT extends AsyncNotifierBase<T>,
        T>
    extends ProviderWithNotifier<AsyncValue<T>, NotifierT>
    with FutureModifier<T> {
// ...
}

[munificent]

Yeah, I agree the current formatting is pretty bad. The new in-progress style gives you:

abstract class StreamNotifierProviderBase<
  NotifierT extends AsyncNotifierBase<T>,
  T
> extends ProviderWithNotifier<AsyncValue<T>, NotifierT>
    with FutureModifier<T> {
  // ...
}

Which isn't much better, I think. The rule should probably be that if the class type parameters split, then we force any subsequent clauses to move to their own lines too, like:

abstract class StreamNotifierProviderBase<
      NotifierT extends AsyncNotifierBase<T>,
      T
    >
    extends ProviderWithNotifier<AsyncValue<T>, NotifierT>
    with FutureModifier<T> {
  // ...
}

I don't plan to tweak the formatting in the old style, but I'll leave this issue open to improve how the new style handles this case.