HHH-15435 Improve error when using derived root in context that needs expansion

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

@@ -4122,8 +4122,7 @@ else if ( actualModelPart instanceof EmbeddableValuedModelPart ) {
 					tableGroup
 			);
 		}
-		else {
-			assert actualModelPart instanceof BasicValuedModelPart;
+		else if ( actualModelPart instanceof BasicValuedModelPart ) {
 			final BasicValuedModelPart mapping = (BasicValuedModelPart) actualModelPart;
 			final TableReference tableReference = tableGroup.resolveTableReference(
 					navigablePath.append( actualModelPart.getPartName() ),
@@ -4154,6 +4153,20 @@ else if ( expression instanceof SqlSelectionExpression ) {
 					tableGroup
 			);
 		}
+		else if ( actualModelPart instanceof AnonymousTupleTableGroupProducer ) {
+			throw new SemanticException(
+					"The derived SqmFrom" + ( (AnonymousTupleType<?>) path.getReferencedPathSource() ).getComponentNames() + " can not be used in a context where the expression needs to " +
+							"be expanded to identifying parts, because a derived model part does not have identifying parts. " +
+							"Replace uses of the root with paths instead e.g. `derivedRoot.get(\"alias1\")` or `derivedRoot.alias1`"
+			);
+		}
+		else {
+			throw new SemanticException(
+					"The SqmFrom node [" + path + "] can not be used in a context where the expression needs to " +
+							"be expanded to identifying parts, because the model part [" + actualModelPart +
+							"] does not have identifying parts."
+			);
+		}
 
 		return withTreatRestriction( result, path );
 	}

hibernate-core/src/test/java/org/hibernate/orm/test/query/criteria/DerivedRootExpansionUsageTest.java

@@ -0,0 +1,80 @@
+package org.hibernate.orm.test.query.criteria;
+
+import org.hibernate.query.SemanticException;
+import org.hibernate.query.sqm.tree.SqmCopyContext;
+import org.hibernate.query.sqm.tree.select.SqmQuerySpec;
+import org.hibernate.query.sqm.tree.select.SqmSelectStatement;
+import org.hibernate.query.sqm.tree.select.SqmSubQuery;
+
+import org.hibernate.testing.orm.junit.EntityManagerFactoryScope;
+import org.hibernate.testing.orm.junit.JiraKey;
+import org.hibernate.testing.orm.junit.Jpa;
+import org.junit.jupiter.api.Test;
+
+import jakarta.persistence.Entity;
+import jakarta.persistence.Id;
+import jakarta.persistence.Tuple;
+import jakarta.persistence.criteria.CriteriaBuilder;
+import jakarta.persistence.criteria.CriteriaQuery;
+import jakarta.persistence.criteria.Root;
+import jakarta.persistence.criteria.Subquery;
+import org.assertj.core.api.Assertions;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+@Jpa(
+		annotatedClasses = {
+				DerivedRootExpansionUsageTest.TestEntity.class,
+		}
+)
+public class DerivedRootExpansionUsageTest {
+
+	@Test
+	@JiraKey("HHH-15435")
+	public void test(EntityManagerFactoryScope scope) {
+		scope.inEntityManager(
+				entityManager -> {
+					final CriteriaBuilder cb = entityManager.getCriteriaBuilder();
+
+					final CriteriaQuery<Tuple> query = cb.createQuery( Tuple.class );
+					final Root<TestEntity> from1 = query.from( TestEntity.class );
+					query.where( from1.get( "name" ).isNotNull() );
+
+					final SqmSelectStatement<Long> countQuery = (SqmSelectStatement<Long>) cb.createQuery( Long.class );
+					final Subquery<Tuple> subQuery = countQuery.subquery( Tuple.class );
+
+					final SqmSubQuery<Tuple> sqmSubQuery = (SqmSubQuery<Tuple>) subQuery;
+					final SqmSelectStatement<Tuple> sqmOriginalQuery = (SqmSelectStatement<Tuple>) query;
+					final SqmQuerySpec<Tuple> sqmOriginalQuerySpec = sqmOriginalQuery.getQuerySpec();
+					final SqmQuerySpec<Tuple> sqmSubQuerySpec = sqmOriginalQuerySpec.copy( SqmCopyContext.simpleContext() );
+
+					sqmSubQuery.setQueryPart(sqmSubQuerySpec);
+					Root<TestEntity> subQuerySelectRoot = subQuery.from(TestEntity.class);
+					sqmSubQuery.multiselect(subQuerySelectRoot.get("id").alias("id"));
+
+					var root = countQuery.from(sqmSubQuery);
+					countQuery.select(cb.count(root));
+
+					try {
+						entityManager.createQuery( countQuery ).getSingleResult();
+						Assertions.fail( "Should fail because of `select(cb.count(root))`" );
+					}
+					catch (IllegalArgumentException ex) {
+						assertThat( ex.getCause() ).isInstanceOf( SemanticException.class );
+						assertThat( ex.getCause().getMessage() ).contains( "derivedRoot.get(\"alias1\")` or `derivedRoot.alias1`" );
+					}
+				}
+		);
+	}
+
+	@Entity(name = "TestEntity")
+	public static class TestEntity {
+
+		@Id
+		private Integer id;
+
+		private String name;
+
+	}
+
+}