Use BAG for unowned OneToMany and throw an error if @OrderColumn is found on unowned ManyToMany

hibernate-core/src/main/java/org/hibernate/cfg/AnnotationBinder.java

@@ -2377,6 +2377,17 @@ public final class AnnotationBinder {
 			);
 		}
 
+		if ( property.isAnnotationPresent( OrderColumn.class )
+				&& manyToManyAnn != null && !manyToManyAnn.mappedBy().isEmpty() ) {
+			throw new AnnotationException(
+					"Explicit @OrderColumn on inverse side of @ManyToMany is illegal: "
+							+ BinderHelper.getPath(
+							propertyHolder,
+							inferredData
+					)
+			);
+		}
+
 		final IndexColumn indexColumn = IndexColumn.fromAnnotations(
 				property.getAnnotation( OrderColumn.class ),
 				property.getAnnotation( org.hibernate.annotations.IndexColumn.class ),

hibernate-core/src/main/java/org/hibernate/cfg/annotations/CollectionBinder.java

@@ -565,6 +565,11 @@ public abstract class CollectionBinder {
 				// We don't support @OrderColumn on the non-owning side of a many-to-many association.
 				return CollectionClassification.BAG;
 			}
+			OneToMany oneToMany = property.getAnnotation( OneToMany.class );
+			if ( oneToMany != null && ! StringHelper.isEmpty( oneToMany.mappedBy() ) ) {
+				// Unowned to-many mappings are always considered BAG by default
+				return CollectionClassification.BAG;
+			}
 			// otherwise, return the implicit classification for List attributes
 			return buildingContext.getBuildingOptions().getMappingDefaults().getImplicitListClassification();
 		}