code: public static <T extends Case1<A>, A> DecomposableMatchBuilder0<T> case1(
        Class<T> clazz, MatchesExact<A> a) {
      List<Matcher<Object>> matchers = Lists.of(ArgumentMatchers.eq(a.t));
      return new DecomposableMatchBuilder0<T>(matchers, new Case1FieldExtractor<>(clazz));
    }
docs: Matches a case class of one element.