better support for `switch` cases

[jashmenn]

Say we have the following typescript:

let reducer: Reducer<AppState> =
  (state: AppState, action: Action): AppState => {
  switch (action.type) {
  case 'ADD_MESSAGE':
    return {
      messages: state.messages.concat(
        (<AddMessageAction>action).message
      ),
    };
  case 'DELETE_MESSAGE':
    let idx = (<DeleteMessageAction>action).index;
    return {
      messages: [
        ...state.messages.slice(0, idx),
        ...state.messages.slice(idx + 1, state.messages.length)
      ]
    };
  default:
    return state;
  }
};

What query captures the DELETE_MESSAGE case, upto but not including default?