[#1598] engine: Drop unnecessary result structs

Signed-off-by: Dmitrii Stepanov <d.stepanov@yadro.com>

pkg/local_object_storage/engine/delete.go

@@ -24,11 +24,6 @@ type DeletePrm struct {
 	forceRemoval bool
 }
 
-// DeleteRes groups the resulting values of Delete operation.
-type DeleteRes struct{}
-
-var deleteRes = DeleteRes{}
-
 // WithAddress is a Delete option to set the addresses of the objects to delete.
 //
 // Option is required.
@@ -53,7 +48,7 @@ func (p *DeletePrm) WithForceRemoval() {
 // NOTE: Marks any object to be deleted (despite any prohibitions
 // on operations with that object) if WithForceRemoval option has
 // been provided.
-func (e *StorageEngine) Delete(ctx context.Context, prm DeletePrm) (res DeleteRes, err error) {
+func (e *StorageEngine) Delete(ctx context.Context, prm DeletePrm) error {
 	ctx, span := tracing.StartSpanFromContext(ctx, "StorageEngine.Delete",
 		trace.WithAttributes(
 			attribute.String("address", prm.addr.EncodeToString()),
@@ -62,15 +57,12 @@ func (e *StorageEngine) Delete(ctx context.Context, prm DeletePrm) (res DeleteRe
 	defer span.End()
 	defer elapsed("Delete", e.metrics.AddMethodDuration)()
 
-	err = e.execIfNotBlocked(func() error {
-		res, err = e.delete(ctx, prm)
-		return err
+	return e.execIfNotBlocked(func() error {
+		return e.delete(ctx, prm)
 	})
-
-	return
 }
 
-func (e *StorageEngine) delete(ctx context.Context, prm DeletePrm) (DeleteRes, error) {
+func (e *StorageEngine) delete(ctx context.Context, prm DeletePrm) error {
 	var locked struct {
 		is bool
 	}
@@ -128,14 +120,14 @@ func (e *StorageEngine) delete(ctx context.Context, prm DeletePrm) (DeleteRes, e
 	})
 
 	if locked.is {
-		return deleteRes, new(apistatus.ObjectLocked)
+		return new(apistatus.ObjectLocked)
 	}
 
 	if splitInfo != nil {
 		e.deleteChildren(ctx, prm.addr, prm.forceRemoval, splitInfo.SplitID())
 	}
 
-	return deleteRes, nil
+	return nil
 }
 
 func (e *StorageEngine) deleteChildren(ctx context.Context, addr oid.Address, force bool, splitID *objectSDK.SplitID) {