Add positionProvider implementation assertion (#9261)

Signed-off-by: NCongqi Xia <congqi.xia@zilliz.com>

internal/datacoord/datanode_helper.go

@@ -25,6 +25,8 @@ type positionProvider interface {
 	GetVChanPositions(vchans []vchannel, seekFromStartPosition bool) ([]*datapb.VchannelInfo, error)
 }
 
+var _ positionProvider = (*dummyPosProvider)(nil)
+
 type dummyPosProvider struct{}
 
 //GetVChanPositions implements positionProvider

internal/datacoord/server.go

@@ -79,6 +79,9 @@ type RootCoordCreatorFunc func(ctx context.Context, metaRootPath string, etcdEnd
 // makes sure Server implements `DataCoord`
 var _ types.DataCoord = (*Server)(nil)
 
+// makes sure Server implements `positionProvider`
+var _ positionProvider = (*Server)(nil)
+
 // Server implements `types.Datacoord`
 // handles Data Cooridinator related jobs
 type Server struct {