code: @SuppressWarnings("unchecked")
          public SwitchBlock<T, R> Case(T ca, VFunc0 func) {
                  return Case(ca, (def<R>) $(func));
          }
docs: add a Case block to the expression
  
  @param ca   the object for switch-expression to match
  @param func function to apply when matches
  @return <code>this</code>