docs: private static boolean canEncode(final CoreCharset charset, final char c, final CharsetEncoder fallback) {
          // todo add more charset tests if impacted by Android's bad perf in canEncode
          switch (charset) {
              case ascii:
                  return c < 0x80;
              case utf:
                  return true; // real is:!(Character.isLowSurrogate(c) || Character.isHighSurrogate(c)); - but already check above
              default:
                  return fallback.canEncode(c);
          }
      }