public ImmutableList<String> getInitToAllSet() {
    return bitmaskFields.stream()
        .map(field -> field.name + " = " + cast(field.type, field.allSetBitmask) + ";")
        .collect(toImmutableList());
  }
Returns code to indicate that all tracked properties have received a value. This is needed in
the {@code toBuilder()} constructor, since it assigns to the corresponding fields directly
without going through their setters.
value/src/main/java/com/google/auto/value/processor/BuilderRequiredProperties.java