Mark Scan as an abstract node type, too.

On further review, this one is never instantiated either.

src/include/nodes/plannodes.h

@@ -371,10 +371,14 @@ typedef struct BitmapOr
 /*
  * ==========
  * Scan nodes
+ *
+ * Scan is an abstract type that all relation scan plan types inherit from.
  * ==========
  */
 typedef struct Scan
 {
+	pg_node_attr(abstract)
+
 	Plan		plan;
 	Index		scanrelid;		/* relid is index into the range table */
 } Scan;

src/test/modules/test_oat_hooks/test_oat_hooks.c

@@ -492,9 +492,6 @@ nodetag_to_string(NodeTag tag)
 		case T_BitmapOr:
 			return "BitmapOr";
 			break;
-		case T_Scan:
-			return "Scan";
-			break;
 		case T_SeqScan:
 			return "SeqScan";
 			break;