message: Add bool and explicit types for merger
diff: @@ -298,6 +298,7 @@ impl IndexMerger {
  FieldType::U64(ref options)
  | FieldType::I64(ref options)
  | FieldType::F64(ref options)
  + | FieldType::Bool(ref options)
  | FieldType::Date(ref options) => match options.get_fastfield_cardinality() {
  Some(Cardinality::SingleValue) => {
  self.write_single_fast_field(field, fast_field_serializer, doc_id_mapping)?;
  @@ -312,7 +313,7 @@ impl IndexMerger {
  self.write_bytes_fast_field(field, fast_field_serializer, doc_id_mapping)?;
  }
  }
  - _ => {
  + FieldType::JsonObject(_) | FieldType::Facet(_) | FieldType::Str(_) => {
  // We don't handle json fast field for the moment
  // They can be implemented using what is done
  // for facets in the future
  