fix: no member named 'SourceFieldIndex' (#131)

Author: zhjwpku

src/iceberg/avro/avro_data_util.cc

@@ -70,8 +70,7 @@ Status AppendStructToBuilder(const ::avro::NodePtr& avro_node,
     auto* field_builder = struct_builder->field_builder(static_cast<int>(i));
 
     if (field_projection.kind == FieldProjection::Kind::kProjected) {
-      size_t avro_field_index =
-          std::get<FieldProjection::SourceFieldIndex>(field_projection.from);
+      size_t avro_field_index = std::get<size_t>(field_projection.from);
       if (avro_field_index >= avro_record.fieldCount()) {
         return InvalidArgument("Avro field index {} out of bound {}", avro_field_index,
                                avro_record.fieldCount());

src/iceberg/avro/avro_schema_util.cc

@@ -672,7 +672,7 @@ Result<FieldProjection> ProjectList(const ListType& list_type,
 
   // Set the element projection metadata but preserve its children
   element_projection.kind = FieldProjection::Kind::kProjected;
-  element_projection.from = FieldProjection::SourceFieldIndex{0};
+  element_projection.from = size_t{0};
 
   FieldProjection result;
   result.children.emplace_back(std::move(element_projection));