HHH-16564 introduce BottomType

hibernate-core/src/main/java/org/hibernate/query/sqm/sql/BaseSqmToSqlAstConverter.java

@@ -389,15 +389,13 @@ import org.hibernate.sql.results.graph.internal.ImmutableFetchList;
 import org.hibernate.sql.results.internal.SqlSelectionImpl;
 import org.hibernate.sql.results.internal.StandardEntityGraphTraversalStateImpl;
 import org.hibernate.type.BasicType;
+import org.hibernate.type.BottomType;
 import org.hibernate.type.JavaObjectType;
 import org.hibernate.type.SqlTypes;
-import org.hibernate.type.descriptor.WrapperOptions;
 import org.hibernate.type.descriptor.converter.spi.BasicValueConverter;
-import org.hibernate.type.descriptor.java.AbstractClassJavaType;
 import org.hibernate.type.descriptor.java.JavaType;
 import org.hibernate.type.descriptor.java.JavaTypeHelper;
 import org.hibernate.type.descriptor.jdbc.JdbcTypeIndicators;
-import org.hibernate.type.descriptor.jdbc.NullJdbcType;
 import org.hibernate.type.internal.BasicTypeImpl;
 import org.hibernate.type.spi.TypeConfiguration;
 import org.hibernate.usertype.UserVersionType;
@@ -4876,16 +4874,7 @@ public abstract class BaseSqmToSqlAstConverter<T extends Statement> extends Base
 			final MappingModelExpressible<?> keyExpressible = getKeyExpressible( mappingModelExpressible );
 			if ( keyExpressible == null ) {
 				// treat Void as the bottom type, the class of null
-				return new QueryLiteral<>( null, new JavaObjectType(NullJdbcType.INSTANCE, new AbstractClassJavaType<>(Void.class) {
-					@Override
-					public <X> X unwrap(Object value, Class<X> type, WrapperOptions options) {
-						return null;
-					}
-					@Override
-					public <X> Void wrap(X value, WrapperOptions options) {
-						return null;
-					}
-				} ) );
+				return new QueryLiteral<>( null, BottomType.INSTANCE );
 			}
 
 			final List<Expression> expressions = new ArrayList<>( keyExpressible.getJdbcTypeCount() );

hibernate-core/src/main/java/org/hibernate/query/sqm/tree/expression/Compatibility.java

@@ -57,7 +57,7 @@ public class Compatibility {
 		assert to != null;
 		assert from != null;
 
-		if ( from == Void.class ) {
+		if ( from == Void.class && !to.isPrimitive() ) {
 			// treat Void as the bottom type, the class of null
 			return true;
 		}

hibernate-core/src/main/java/org/hibernate/type/BottomType.java

@@ -0,0 +1,48 @@
+/*
+ * Hibernate, Relational Persistence for Idiomatic Java
+ *
+ * License: GNU Lesser General Public License (LGPL), version 2.1 or later
+ * See the lgpl.txt file in the root directory or http://www.gnu.org/licenses/lgpl-2.1.html
+ */
+package org.hibernate.type;
+
+import org.hibernate.Internal;
+import org.hibernate.type.descriptor.WrapperOptions;
+import org.hibernate.type.descriptor.java.AbstractClassJavaType;
+import org.hibernate.type.descriptor.jdbc.NullJdbcType;
+
+/**
+ * A type that is assignable to every non-primitive type,
+ * that is, the type of {@code null}. Note that this not
+ * a true bottom type, since {@code null} cannot be assigned
+ * to primitive types.
+ * <p>
+ * Since the Java language does not have an explicit bottom
+ * type, we follow the type system developed for the Ceylon
+ * language and treat {@link Void} as the Java bottom type.
+ *
+ * @author Gavin King
+ */
+@Internal
+public class BottomType extends AbstractSingleColumnStandardBasicType<Void> {
+
+	public static final BottomType INSTANCE = new BottomType();
+
+	private BottomType() {
+		super( NullJdbcType.INSTANCE, new AbstractClassJavaType<>(Void.class) {
+			@Override
+			public <X> X unwrap(Void value, Class<X> type, WrapperOptions options) {
+				return null;
+			}
+			@Override
+			public <X> Void wrap(X value, WrapperOptions options) {
+				return null;
+			}
+		} );
+	}
+
+	@Override
+	public String getName() {
+		return "NULL";
+	}
+}