docs: @Override
      public void visitFormalTypeParameter(final String name) {
          if (type == TYPE_SIGNATURE
                  || (state != EMPTY && state != FORMAL && state != BOUND)) {
              throw new IllegalStateException();
          }
          CheckMethodAdapter.checkIdentifier(name, "formal type parameter");
          state = FORMAL;
          if (sv != null) {
              sv.visitFormalTypeParameter(name);
          }
      }