docs: private static int checkFormalTypeParameters(final String signature, int pos) {
          // FormalTypeParameters:
          // < FormalTypeParameter+ >
  
          pos = checkChar('<', signature, pos);
          pos = checkFormalTypeParameter(signature, pos);
          while (getChar(signature, pos) != '>') {
              pos = checkFormalTypeParameter(signature, pos);
          }
          return pos + 1;
      }