HHH-17193 Introduce `Fetch#asFetchParent()` to avoid instanceof checks

hibernate-core/src/main/java/org/hibernate/metamodel/mapping/internal/DiscriminatedAssociationMapping.java

@@ -536,6 +536,11 @@ public class DiscriminatedAssociationMapping implements MappingType, FetchOption
 					getKeyValueFetch().createAssembler( parentAccess, creationState )
 			);
 		}
+
+		@Override
+		public FetchParent asFetchParent() {
+			return this;
+		}
 	}
 
 	private static class AnyResultAssembler<T> implements DomainResultAssembler<T> {

hibernate-core/src/main/java/org/hibernate/sql/results/graph/Fetch.java

@@ -37,6 +37,14 @@ public interface Fetch extends DomainResultGraphNode {
 	 */
 	FetchParent getFetchParent();
 
+	/**
+	 * Utility method to avoid {@code instanceof} checks. Returns this if it's
+	 * an instance of {@link FetchParent}, null otherwise.
+	 */
+	default FetchParent asFetchParent() {
+		return null;
+	}
+
 	/**
 	 * The value mapping being fetched
 	 */

hibernate-core/src/main/java/org/hibernate/sql/results/graph/FetchList.java

@@ -72,7 +72,7 @@ public interface FetchList extends Iterable<Fetch> {
 			if ( fetch instanceof EagerCollectionFetch ) {
 				return true;
 			}
-			else if ( fetch instanceof FetchParent && ( (FetchParent) fetch ).containsCollectionFetches() ) {
+			else if ( fetch.asFetchParent() != null && fetch.asFetchParent().containsCollectionFetches() ) {
 				return true;
 			}
 		}

hibernate-core/src/main/java/org/hibernate/sql/results/graph/collection/internal/EagerCollectionFetch.java

@@ -220,4 +220,9 @@ public class EagerCollectionFetch extends CollectionFetch implements FetchParent
 	public JavaType<?> getResultJavaType() {
 		return getFetchedMapping().getJavaType();
 	}
+
+	@Override
+	public FetchParent asFetchParent() {
+		return this;
+	}
 }

hibernate-core/src/main/java/org/hibernate/sql/results/graph/embeddable/internal/AggregateEmbeddableFetchImpl.java

@@ -170,4 +170,9 @@ public class AggregateEmbeddableFetchImpl extends AbstractFetchParent implements
 
 		return new EmbeddableAssembler( initializer );
 	}
+
+	@Override
+	public FetchParent asFetchParent() {
+		return this;
+	}
 }

hibernate-core/src/main/java/org/hibernate/sql/results/graph/embeddable/internal/EmbeddableFetchImpl.java

@@ -168,4 +168,8 @@ public class EmbeddableFetchImpl extends AbstractFetchParent implements Embeddab
 		return getFetchParent().appliesTo( graphImplementor, metamodel );
 	}
 
+	@Override
+	public FetchParent asFetchParent() {
+		return this;
+	}
 }

hibernate-core/src/main/java/org/hibernate/sql/results/graph/entity/AbstractEntityResultGraphNode.java

@@ -43,13 +43,13 @@ public abstract class AbstractEntityResultGraphNode extends AbstractFetchParent
 		final TableGroup entityTableGroup = creationState.getSqlAstCreationState().getFromClauseAccess()
 				.getTableGroup( navigablePath );
 		final EntityResultGraphNode entityResultGraphNode = (EntityResultGraphNode) fetchParent;
-		final Fetch fetch = creationState.visitIdentifierFetch( entityResultGraphNode );
+		final Fetch idFetch = creationState.visitIdentifierFetch( entityResultGraphNode );
 		if ( navigablePath.getParent() == null && !creationState.forceIdentifierSelection() &&
-				( !( fetch instanceof FetchParent ) || !( (FetchParent) fetch ).containsCollectionFetches() ) ) {
+				( idFetch.asFetchParent() == null || !idFetch.asFetchParent().containsCollectionFetches() ) ) {
 			identifierFetch = null;
 		}
 		else {
-			identifierFetch = fetch;
+			identifierFetch = idFetch;
 		}
 
 		discriminatorFetch = creationState.visitDiscriminatorFetch( entityResultGraphNode );

hibernate-core/src/main/java/org/hibernate/sql/results/graph/entity/EntityFetch.java

@@ -7,6 +7,7 @@
 package org.hibernate.sql.results.graph.entity;
 
 import org.hibernate.sql.results.graph.Fetch;
+import org.hibernate.sql.results.graph.FetchParent;
 
 /**
  * Specialization of Fetch for entity-valued fetches
@@ -19,4 +20,8 @@ public interface EntityFetch extends EntityResultGraphNode, Fetch {
 		return true;
 	}
 
+	@Override
+	default FetchParent asFetchParent() {
+		return this;
+	}
 }