message: Rename OccursInList to OccursInTuple.
  The documentation was inconsistent with the code, and I think OccursInTuple is the more appropriate name.
diff: @@ -33,19 +33,19 @@ namespace internal {
  // First declare the template which always takes two parameters.
  template <typename TestType, typename Tuple>
  -class OccursInList;
  +class OccursInTuple;
  // In the special case where the tuple is empty, the result is false.
  template <typename TestType>
  -class OccursInList<TestType, std::tuple<>> : public std::false_type {};
  +class OccursInTuple<TestType, std::tuple<>> : public std::false_type {};
  // If the list is not empty, the result is true if TestType equals the first in
  // the list, or TestType occurs in the rest of the list.
  template <typename TestType, typename First, typename... List>
  -class OccursInList<TestType, std::tuple<First, List...>>
  +class OccursInTuple<TestType, std::tuple<First, List...>>
  : public absl::disjunction<
  std::is_same<TestType, First>,
  - OccursInList<TestType, typename std::tuple<List...>>> {};
  + OccursInTuple<TestType, typename std::tuple<List...>>> {};
  // The class HasDuplicates. Defines ::value as true in case the given list has
  // a duplicate, false otherwise.
  @@ -61,7 +61,7 @@ class HasDuplicates<> : public std::false_type {};
  template <typename First, typename... List>
  class HasDuplicates<First, List...>
  : public absl::disjunction<
  - OccursInList<First, typename std::tuple<List...>>,
  + OccursInTuple<First, typename std::tuple<List...>>,
  HasDuplicates<List...>> {};
  } // namespace internal
  