code: List<Type> sigToTypeParams() {
          List<Type> tvars = List.nil();
          if (signature[sigp] == '<') {
              sigp++;
              int start = sigp;
              sigEnterPhase = true;
              while (signature[sigp] != '>')
                  tvars = tvars.prepend(sigToTypeParam());
              sigEnterPhase = false;
              sigp = start;
              while (signature[sigp] != '>')
                  sigToTypeParam();
              sigp++;
          }
          return tvars.reverse();
      }
docs: Convert signature to type parameters, where signature is implicit.