code: private String typaramsString(List<Type> tvars) {
              StringBuilder s = new StringBuilder();
              s.append('<');
              boolean first = true;
              for (Type t : tvars) {
                  if (!first) s.append(", ");
                  first = false;
                  appendTyparamString(((TypeVar)t), s);
              }
              s.append('>');
              return s.toString();
          }
docs: where