docs: public static void checkClassSignature(final String signature) {
          // ClassSignature:
          // FormalTypeParameters? ClassTypeSignature ClassTypeSignature*
  
          int pos = 0;
          if (getChar(signature, 0) == '<') {
              pos = checkFormalTypeParameters(signature, pos);
          }
          pos = checkClassTypeSignature(signature, pos);
          while (getChar(signature, pos) == 'L') {
              pos = checkClassTypeSignature(signature, pos);
          }
          if (pos != signature.length()) {
              throw new IllegalArgumentException(signature + ": error at index "
                      + pos);
          }
      }