docs: private static int checkTypeArgument(final String signature, int pos) {
          // TypeArgument:
          // * | ( ( + | - )? FieldTypeSignature )
  
          char c = getChar(signature, pos);
          if (c == '*') {
              return pos + 1;
          } else if (c == '+' || c == '-') {
              pos++;
          }
          return checkFieldTypeSignature(signature, pos);
      }