Simplify the whole SqmFunctionDescriptor hierarchy

And make the various function implementations work in more common ways.

- remove some unnecessary flexibility
- simplify some function descriptors to do their work during render()
- fix generics of QueryLiteral
- fix DerbyConcatEmulation

hibernate-core/src/main/java/org/hibernate/dialect/function/CastFunction.java

@@ -7,27 +7,24 @@
 package org.hibernate.dialect.function;
 
 import org.hibernate.dialect.Dialect;
-import org.hibernate.metamodel.model.domain.AllowableFunctionReturnType;
+import org.hibernate.metamodel.mapping.BasicValuedMapping;
 import org.hibernate.query.CastType;
-import org.hibernate.query.spi.QueryEngine;
-import org.hibernate.query.sqm.function.AbstractSqmFunctionDescriptor;
-import org.hibernate.query.sqm.function.SelfRenderingSqlFunctionExpression;
+import org.hibernate.query.sqm.function.AbstractSqmSelfRenderingFunctionDescriptor;
 import org.hibernate.query.sqm.produce.function.StandardArgumentsValidators;
 import org.hibernate.query.sqm.produce.function.StandardFunctionReturnTypeResolvers;
-import org.hibernate.query.sqm.tree.SqmTypedNode;
-import org.hibernate.query.sqm.tree.expression.SqmCastTarget;
-import org.hibernate.query.sqm.tree.expression.SqmExpression;
-import org.hibernate.type.spi.TypeConfiguration;
+import org.hibernate.query.sqm.produce.function.internal.PatternRenderer;
+import org.hibernate.sql.ast.SqlAstWalker;
+import org.hibernate.sql.ast.spi.SqlAppender;
+import org.hibernate.sql.ast.tree.SqlAstNode;
+import org.hibernate.sql.ast.tree.expression.CastTarget;
+import org.hibernate.sql.ast.tree.expression.Expression;
 
 import java.util.List;
 
-import static org.hibernate.query.sqm.produce.function.StandardFunctionReturnTypeResolvers.useArgType;
-
 /**
  * @author Gavin King
  */
-public class CastFunction
-		extends AbstractSqmFunctionDescriptor {
+public class CastFunction extends AbstractSqmSelfRenderingFunctionDescriptor {
 
 	private Dialect dialect;
 
@@ -41,30 +38,44 @@ public class CastFunction
 	}
 
 	@Override
-	protected <T> SelfRenderingSqlFunctionExpression<T> generateSqmFunctionExpression(
-			List<SqmTypedNode<?>> arguments,
-			AllowableFunctionReturnType<T> impliedResultType,
-			QueryEngine queryEngine,
-			TypeConfiguration typeConfiguration) {
-		SqmCastTarget<?> targetType = (SqmCastTarget<?>) arguments.get(1);
-		SqmExpression<?> arg = (SqmExpression<?>) arguments.get(0);
+	public void render(SqlAppender sqlAppender, List<SqlAstNode> arguments, SqlAstWalker walker) {
+		CastTarget targetType = (CastTarget) arguments.get(1);
+		Expression arg = (Expression) arguments.get(0);
 
-		CastType to = CastType.from( targetType.getType() );
-		CastType from = CastType.from( arg.getNodeType() );
+		CastType to = CastType.from( targetType.getExpressionType().getBasicType() );
+		//TODO: generalize this to things which aren't BasicValuedMappings
+		CastType from = CastType.from( ( (BasicValuedMapping) arg.getExpressionType() ).getBasicType() );
 
-		return queryEngine.getSqmFunctionRegistry()
-				.patternDescriptorBuilder( "cast", dialect.castPattern( from, to ) )
-				.setExactArgumentCount( 2 )
-				.setReturnTypeResolver( useArgType( 2 ) )
-				.descriptor()
-				.generateSqmExpression(
-						arguments,
-						impliedResultType,
-						queryEngine,
-						typeConfiguration
-				);
+		String cast = dialect.castPattern( from, to );
+
+		new PatternRenderer( cast ).render( sqlAppender, arguments, walker );
 	}
 
+//	@Override
+//	protected <T> SelfRenderingSqmFunction<T> generateSqmFunctionExpression(
+//			List<SqmTypedNode<?>> arguments,
+//			AllowableFunctionReturnType<T> impliedResultType,
+//			QueryEngine queryEngine,
+//			TypeConfiguration typeConfiguration) {
+//		SqmCastTarget<?> targetType = (SqmCastTarget<?>) arguments.get(1);
+//		SqmExpression<?> arg = (SqmExpression<?>) arguments.get(0);
+//
+//		CastType to = CastType.from( targetType.getType() );
+//		CastType from = CastType.from( arg.getNodeType() );
+//
+//		return queryEngine.getSqmFunctionRegistry()
+//				.patternDescriptorBuilder( "cast", dialect.castPattern( from, to ) )
+//				.setExactArgumentCount( 2 )
+//				.setReturnTypeResolver( useArgType( 2 ) )
+//				.descriptor()
+//				.generateSqmExpression(
+//						arguments,
+//						impliedResultType,
+//						queryEngine,
+//						typeConfiguration
+//				);
+//	}
+
 	@Override
 	public String getArgumentListSignature() {
 		return "(arg as Type)";

hibernate-core/src/main/java/org/hibernate/dialect/function/CastStrEmulation.java

@@ -9,7 +9,7 @@ package org.hibernate.dialect.function;
 import org.hibernate.metamodel.model.domain.AllowableFunctionReturnType;
 import org.hibernate.query.spi.QueryEngine;
 import org.hibernate.query.sqm.function.AbstractSqmFunctionDescriptor;
-import org.hibernate.query.sqm.function.SelfRenderingSqlFunctionExpression;
+import org.hibernate.query.sqm.function.SelfRenderingSqmFunction;
 import org.hibernate.query.sqm.produce.function.StandardArgumentsValidators;
 import org.hibernate.query.sqm.produce.function.StandardFunctionReturnTypeResolvers;
 import org.hibernate.query.sqm.tree.SqmTypedNode;
@@ -36,7 +36,7 @@ public class CastStrEmulation
 	}
 
 	@Override
-	protected <T> SelfRenderingSqlFunctionExpression<T> generateSqmFunctionExpression(
+	protected <T> SelfRenderingSqmFunction<T> generateSqmFunctionExpression(
 			List<SqmTypedNode<?>> arguments,
 			AllowableFunctionReturnType<T> impliedResultType,
 			QueryEngine queryEngine,

hibernate-core/src/main/java/org/hibernate/dialect/function/CoalesceIfnullEmulation.java

@@ -9,7 +9,7 @@ package org.hibernate.dialect.function;
 import org.hibernate.metamodel.model.domain.AllowableFunctionReturnType;
 import org.hibernate.query.spi.QueryEngine;
 import org.hibernate.query.sqm.function.AbstractSqmFunctionDescriptor;
-import org.hibernate.query.sqm.function.SelfRenderingSqlFunctionExpression;
+import org.hibernate.query.sqm.function.SelfRenderingSqmFunction;
 import org.hibernate.query.sqm.produce.function.StandardArgumentsValidators;
 import org.hibernate.query.sqm.tree.SqmTypedNode;
 import org.hibernate.type.spi.TypeConfiguration;
@@ -30,7 +30,7 @@ public class CoalesceIfnullEmulation
 	}
 
 	@Override
-	protected <T> SelfRenderingSqlFunctionExpression<T> generateSqmFunctionExpression(
+	protected <T> SelfRenderingSqmFunction<T> generateSqmFunctionExpression(
 			List<SqmTypedNode<?>> arguments,
 			AllowableFunctionReturnType<T> impliedResultType,
 			QueryEngine queryEngine,

hibernate-core/src/main/java/org/hibernate/dialect/function/CurrentFunction.java

@@ -6,19 +6,13 @@
  */
 package org.hibernate.dialect.function;
 
-import org.hibernate.metamodel.model.domain.AllowableFunctionReturnType;
-import org.hibernate.query.spi.QueryEngine;
-import org.hibernate.query.sqm.function.AbstractSqmFunctionDescriptor;
-import org.hibernate.query.sqm.function.FunctionRenderingSupport;
-import org.hibernate.query.sqm.function.SelfRenderingSqlFunctionExpression;
+import org.hibernate.query.sqm.function.AbstractSqmSelfRenderingFunctionDescriptor;
 import org.hibernate.query.sqm.produce.function.StandardArgumentsValidators;
 import org.hibernate.query.sqm.produce.function.StandardFunctionReturnTypeResolvers;
-import org.hibernate.query.sqm.tree.SqmTypedNode;
 import org.hibernate.sql.ast.SqlAstWalker;
 import org.hibernate.sql.ast.spi.SqlAppender;
 import org.hibernate.sql.ast.tree.SqlAstNode;
 import org.hibernate.type.BasicType;
-import org.hibernate.type.spi.TypeConfiguration;
 
 import java.util.List;
 
@@ -26,9 +20,8 @@ import java.util.List;
  * @author Gavin King
  */
 public class CurrentFunction
-		extends AbstractSqmFunctionDescriptor implements FunctionRenderingSupport {
+		extends AbstractSqmSelfRenderingFunctionDescriptor {
 
-	private final String name;
 	private final String sql;
 
 	public CurrentFunction(String name, String sql, BasicType type) {
@@ -37,7 +30,6 @@ public class CurrentFunction
 				StandardArgumentsValidators.NO_ARGS,
 				StandardFunctionReturnTypeResolvers.invariant( type )
 		);
-		this.name = name;
 		this.sql = sql;
 	}
 
@@ -49,22 +41,6 @@ public class CurrentFunction
 		sqlAppender.appendSql(sql);
 	}
 
-	@Override
-	protected <T> SelfRenderingSqlFunctionExpression<T> generateSqmFunctionExpression(
-			List<SqmTypedNode<?>> arguments,
-			AllowableFunctionReturnType<T> impliedResultType,
-			QueryEngine queryEngine,
-			TypeConfiguration typeConfiguration) {
-		return new SelfRenderingSqlFunctionExpression<T>(
-				this, this,
-				arguments,
-				impliedResultType,
-				getReturnTypeResolver(),
-				queryEngine.getCriteriaBuilder(),
-				name
-		);
-	}
-
 	@Override
 	public String getArgumentListSignature() {
 		return "";

hibernate-core/src/main/java/org/hibernate/dialect/function/DB2FormatEmulation.java

@@ -7,21 +7,15 @@
 package org.hibernate.dialect.function;
 
 import org.hibernate.dialect.OracleDialect;
-import org.hibernate.metamodel.model.domain.AllowableFunctionReturnType;
-import org.hibernate.query.spi.QueryEngine;
-import org.hibernate.query.sqm.function.AbstractSqmFunctionDescriptor;
-import org.hibernate.query.sqm.function.FunctionRenderingSupport;
-import org.hibernate.query.sqm.function.SelfRenderingSqlFunctionExpression;
+import org.hibernate.query.sqm.function.AbstractSqmSelfRenderingFunctionDescriptor;
 import org.hibernate.query.sqm.produce.function.StandardArgumentsValidators;
 import org.hibernate.query.sqm.produce.function.StandardFunctionReturnTypeResolvers;
-import org.hibernate.query.sqm.tree.SqmTypedNode;
 import org.hibernate.sql.ast.SqlAstWalker;
 import org.hibernate.sql.ast.spi.SqlAppender;
 import org.hibernate.sql.ast.tree.SqlAstNode;
 import org.hibernate.sql.ast.tree.expression.Expression;
 import org.hibernate.sql.ast.tree.expression.Format;
 import org.hibernate.type.StandardBasicTypes;
-import org.hibernate.type.spi.TypeConfiguration;
 
 import java.util.List;
 
@@ -34,7 +28,7 @@ import java.util.List;
  * @author Gavin King
  */
 public class DB2FormatEmulation
-		extends AbstractSqmFunctionDescriptor implements FunctionRenderingSupport {
+		extends AbstractSqmSelfRenderingFunctionDescriptor {
 
 	public DB2FormatEmulation() {
 		super(
@@ -84,22 +78,6 @@ public class DB2FormatEmulation
 		sqlAppender.appendSql(")");
 	}
 
-	@Override
-	protected <T> SelfRenderingSqlFunctionExpression<T> generateSqmFunctionExpression(
-			List<SqmTypedNode<?>> arguments,
-			AllowableFunctionReturnType<T> impliedResultType,
-			QueryEngine queryEngine,
-			TypeConfiguration typeConfiguration) {
-		return new SelfRenderingSqlFunctionExpression<T>(
-				this, this,
-				arguments,
-				impliedResultType,
-				getReturnTypeResolver(),
-				queryEngine.getCriteriaBuilder(),
-				"format"
-		);
-	}
-
 	@Override
 	public String getArgumentListSignature() {
 		return "(datetime as pattern)";

hibernate-core/src/main/java/org/hibernate/dialect/function/DerbyConcatEmulation.java

@@ -7,12 +7,12 @@
 package org.hibernate.dialect.function;
 
 import org.hibernate.query.sqm.function.AbstractSqmSelfRenderingFunctionDescriptor;
-import org.hibernate.query.sqm.function.FunctionRenderingSupport;
 import org.hibernate.query.sqm.produce.function.StandardArgumentsValidators;
 import org.hibernate.query.sqm.produce.function.StandardFunctionReturnTypeResolvers;
 import org.hibernate.sql.ast.SqlAstWalker;
 import org.hibernate.sql.ast.spi.SqlAppender;
 import org.hibernate.sql.ast.tree.SqlAstNode;
+import org.hibernate.sql.ast.tree.expression.JdbcParameter;
 import org.hibernate.type.StandardBasicTypes;
 
 import java.util.List;
@@ -25,8 +25,7 @@ import java.util.List;
  * @author Christian Beikov
  */
 public class DerbyConcatEmulation
-		extends AbstractSqmSelfRenderingFunctionDescriptor
-		implements FunctionRenderingSupport {
+		extends AbstractSqmSelfRenderingFunctionDescriptor {
 
 	public DerbyConcatEmulation() {
 		super(
@@ -36,11 +35,6 @@ public class DerbyConcatEmulation
 		);
 	}
 
-	@Override
-	public FunctionRenderingSupport getRenderingSupport() {
-		return this;
-	}
-
 	@Override
 	public void render(
 			SqlAppender sqlAppender,
@@ -55,7 +49,7 @@ public class DerbyConcatEmulation
 			if ( i > 0 ) {
 				sqlAppender.appendSql("||");
 			}
-			boolean param = false; //TODO: argument instanceof GenericParameter;
+			boolean param = argument instanceof JdbcParameter;
 			if ( param ) {
 				sqlAppender.appendSql("cast(");
 			}

hibernate-core/src/main/java/org/hibernate/dialect/function/ExtractFunction.java

@@ -13,7 +13,7 @@ import org.hibernate.query.TemporalUnit;
 import org.hibernate.query.spi.QueryEngine;
 import org.hibernate.query.sqm.NodeBuilder;
 import org.hibernate.query.sqm.function.AbstractSqmFunctionDescriptor;
-import org.hibernate.query.sqm.function.SelfRenderingSqlFunctionExpression;
+import org.hibernate.query.sqm.function.SelfRenderingSqmFunction;
 import org.hibernate.query.sqm.produce.function.StandardArgumentsValidators;
 import org.hibernate.query.sqm.produce.function.StandardFunctionReturnTypeResolvers;
 import org.hibernate.query.sqm.tree.SqmTypedNode;
@@ -47,7 +47,7 @@ public class ExtractFunction
 	}
 
 	@Override
-	protected <T> SelfRenderingSqlFunctionExpression generateSqmFunctionExpression(
+	protected <T> SelfRenderingSqmFunction generateSqmFunctionExpression(
 			List<SqmTypedNode<?>> arguments,
 			AllowableFunctionReturnType<T> impliedResultType,
 			QueryEngine queryEngine,
@@ -96,7 +96,7 @@ public class ExtractFunction
 		}
 	}
 
-	private SelfRenderingSqlFunctionExpression<Integer> extractWeek(
+	private SelfRenderingSqmFunction<Integer> extractWeek(
 			SqmExpression<?> expressionToExtract,
 			SqmExtractUnit<?> field,
 			TemporalUnit dayOf,
@@ -160,7 +160,7 @@ public class ExtractFunction
 				);
 	}
 
-	private SelfRenderingSqlFunctionExpression<Long> toLong(
+	private SelfRenderingSqmFunction<Long> toLong(
 			SqmExpression<?> arg,
 			QueryEngine queryEngine,
 			TypeConfiguration typeConfiguration) {
@@ -183,7 +183,7 @@ public class ExtractFunction
 				);
 	}
 
-	private SelfRenderingSqlFunctionExpression<Long> extractNanoseconds(
+	private SelfRenderingSqmFunction<Long> extractNanoseconds(
 			SqmExpression<?> expressionToExtract,
 			QueryEngine queryEngine,
 			TypeConfiguration typeConfiguration) {
@@ -211,7 +211,7 @@ public class ExtractFunction
 		);
 	}
 
-	private SelfRenderingSqlFunctionExpression<ZoneOffset> extractOffsetUsingFormat(
+	private SelfRenderingSqmFunction<ZoneOffset> extractOffsetUsingFormat(
 			SqmExpression<?> expressionToExtract,
 			QueryEngine queryEngine,
 			TypeConfiguration typeConfiguration) {
@@ -235,7 +235,7 @@ public class ExtractFunction
 				);
 	}
 
-	private SelfRenderingSqlFunctionExpression<?> extractDateOrTimeUsingCast(
+	private SelfRenderingSqmFunction<?> extractDateOrTimeUsingCast(
 			SqmExpression<?> expressionToExtract,
 			AllowableFunctionReturnType<?> type,
 			QueryEngine queryEngine,

hibernate-core/src/main/java/org/hibernate/dialect/function/InsertSubstringOverlayEmulation.java

@@ -10,7 +10,7 @@ import org.hibernate.metamodel.model.domain.AllowableFunctionReturnType;
 import org.hibernate.query.BinaryArithmeticOperator;
 import org.hibernate.query.spi.QueryEngine;
 import org.hibernate.query.sqm.function.AbstractSqmFunctionDescriptor;
-import org.hibernate.query.sqm.function.SelfRenderingSqlFunctionExpression;
+import org.hibernate.query.sqm.function.SelfRenderingSqmFunction;
 import org.hibernate.query.sqm.function.SqmFunctionDescriptor;
 import org.hibernate.query.sqm.produce.function.StandardArgumentsValidators;
 import org.hibernate.query.sqm.produce.function.StandardFunctionReturnTypeResolvers;
@@ -41,7 +41,7 @@ public class InsertSubstringOverlayEmulation
 	}
 
 	@Override
-	protected <T> SelfRenderingSqlFunctionExpression<T> generateSqmFunctionExpression(
+	protected <T> SelfRenderingSqmFunction<T> generateSqmFunctionExpression(
 			List<SqmTypedNode<?>> arguments,
 			AllowableFunctionReturnType<T> impliedResultType,
 			QueryEngine queryEngine,

hibernate-core/src/main/java/org/hibernate/dialect/function/LocatePositionEmulation.java

@@ -9,7 +9,7 @@ package org.hibernate.dialect.function;
 import org.hibernate.metamodel.model.domain.AllowableFunctionReturnType;
 import org.hibernate.query.spi.QueryEngine;
 import org.hibernate.query.sqm.function.AbstractSqmFunctionDescriptor;
-import org.hibernate.query.sqm.function.SelfRenderingSqlFunctionExpression;
+import org.hibernate.query.sqm.function.SelfRenderingSqmFunction;
 import org.hibernate.query.sqm.produce.function.StandardArgumentsValidators;
 import org.hibernate.query.sqm.produce.function.StandardFunctionReturnTypeResolvers;
 import org.hibernate.query.sqm.tree.SqmTypedNode;
@@ -33,7 +33,7 @@ public class LocatePositionEmulation
 	}
 
 	@Override
-	protected <T> SelfRenderingSqlFunctionExpression<T> generateSqmFunctionExpression(
+	protected <T> SelfRenderingSqmFunction<T> generateSqmFunctionExpression(
 			List<SqmTypedNode<?>> arguments,
 			AllowableFunctionReturnType<T> impliedResultType,
 			QueryEngine queryEngine,

hibernate-core/src/main/java/org/hibernate/dialect/function/LpadRpadPadEmulation.java

@@ -10,7 +10,7 @@ import org.hibernate.metamodel.model.domain.AllowableFunctionReturnType;
 import org.hibernate.query.TrimSpec;
 import org.hibernate.query.spi.QueryEngine;
 import org.hibernate.query.sqm.function.AbstractSqmFunctionDescriptor;
-import org.hibernate.query.sqm.function.SelfRenderingSqlFunctionExpression;
+import org.hibernate.query.sqm.function.SelfRenderingSqmFunction;
 import org.hibernate.query.sqm.produce.function.StandardArgumentsValidators;
 import org.hibernate.query.sqm.produce.function.StandardFunctionReturnTypeResolvers;
 import org.hibernate.query.sqm.tree.SqmTypedNode;
@@ -37,7 +37,7 @@ public class LpadRpadPadEmulation
 	}
 
 	@Override
-	protected <T> SelfRenderingSqlFunctionExpression<T> generateSqmFunctionExpression(
+	protected <T> SelfRenderingSqmFunction<T> generateSqmFunctionExpression(
 			List<SqmTypedNode<?>> arguments,
 			AllowableFunctionReturnType<T> impliedResultType,
 			QueryEngine queryEngine,

hibernate-core/src/main/java/org/hibernate/dialect/function/NvlCoalesceEmulation.java

@@ -9,7 +9,7 @@ package org.hibernate.dialect.function;
 import org.hibernate.metamodel.model.domain.AllowableFunctionReturnType;
 import org.hibernate.query.spi.QueryEngine;
 import org.hibernate.query.sqm.function.AbstractSqmFunctionDescriptor;
-import org.hibernate.query.sqm.function.SelfRenderingSqlFunctionExpression;
+import org.hibernate.query.sqm.function.SelfRenderingSqmFunction;
 import org.hibernate.query.sqm.function.SqmFunctionDescriptor;
 import org.hibernate.query.sqm.produce.function.StandardArgumentsValidators;
 import org.hibernate.query.sqm.produce.function.StandardFunctionReturnTypeResolvers;
@@ -40,17 +40,22 @@ public class NvlCoalesceEmulation
 	}
 
 	@Override
-	protected <T> SelfRenderingSqlFunctionExpression<T> generateSqmFunctionExpression(
+	protected <T> SelfRenderingSqmFunction<T> generateSqmFunctionExpression(
 			List<SqmTypedNode<?>> arguments,
 			AllowableFunctionReturnType<T> impliedResultType,
 			QueryEngine queryEngine,
 			TypeConfiguration typeConfiguration) {
 
-		SqmFunctionDescriptor nvl = queryEngine.getSqmFunctionRegistry().namedDescriptorBuilder("nvl").setExactArgumentCount(2).template();
+		SqmFunctionDescriptor nvl =
+				queryEngine.getSqmFunctionRegistry()
+						.namedDescriptorBuilder("nvl")
+						.setExactArgumentCount(2)
+						.descriptor();
 
 		int pos = arguments.size();
 		SqmExpression<?> result = (SqmExpression<?>) arguments.get( --pos );
-		AllowableFunctionReturnType<?> type = (AllowableFunctionReturnType<?>) result.getNodeType();
+		AllowableFunctionReturnType<?> type =
+				(AllowableFunctionReturnType<?>) result.getNodeType();
 
 		while (pos>0) {
 			SqmExpression<?> next = (SqmExpression<?>) arguments.get( --pos );
@@ -63,7 +68,7 @@ public class NvlCoalesceEmulation
 		}
 
 		//noinspection unchecked
-		return (SelfRenderingSqlFunctionExpression<T>) result;
+		return (SelfRenderingSqmFunction<T>) result;
 	}
 
 }

hibernate-core/src/main/java/org/hibernate/dialect/function/TimestampaddFunction.java

@@ -8,16 +8,13 @@ package org.hibernate.dialect.function;
 
 import org.hibernate.dialect.Dialect;
 import org.hibernate.metamodel.model.domain.AllowableFunctionReturnType;
-import org.hibernate.query.spi.QueryEngine;
-import org.hibernate.query.sqm.function.AbstractSqmFunctionDescriptor;
+import org.hibernate.query.sqm.function.AbstractSqmSelfRenderingFunctionDescriptor;
 import org.hibernate.query.sqm.function.SelfRenderingFunctionSqlAstExpression;
-import org.hibernate.query.sqm.function.SelfRenderingSqlFunctionExpression;
 import org.hibernate.query.sqm.produce.function.StandardArgumentsValidators;
 import org.hibernate.query.sqm.produce.function.StandardFunctionReturnTypeResolvers;
 import org.hibernate.query.sqm.produce.function.internal.PatternRenderer;
-import org.hibernate.query.sqm.tree.SqmTypedNode;
-import org.hibernate.query.sqm.tree.expression.SqmExpression;
-import org.hibernate.query.sqm.tree.expression.SqmExtractUnit;
+import org.hibernate.sql.ast.SqlAstWalker;
+import org.hibernate.sql.ast.spi.SqlAppender;
 import org.hibernate.sql.ast.tree.SqlAstNode;
 import org.hibernate.sql.ast.tree.expression.DurationUnit;
 import org.hibernate.sql.ast.tree.expression.Expression;
@@ -26,14 +23,12 @@ import org.hibernate.type.spi.TypeConfiguration;
 import java.util.List;
 
 import static java.util.Arrays.asList;
-import static org.hibernate.query.sqm.produce.function.StandardFunctionReturnTypeResolvers.useArgType;
-import static org.hibernate.type.spi.TypeConfiguration.isSqlTimestampType;
 
 /**
  * @author Gavin King
  */
 public class TimestampaddFunction
-		extends AbstractSqmFunctionDescriptor {
+		extends AbstractSqmSelfRenderingFunctionDescriptor {
 
 	private Dialect dialect;
 
@@ -47,44 +42,56 @@ public class TimestampaddFunction
 	}
 
 	@Override
-	protected <T> SelfRenderingSqlFunctionExpression<T> generateSqmFunctionExpression(
-			List<SqmTypedNode<?>> arguments,
-			AllowableFunctionReturnType<T> impliedResultType,
-			QueryEngine queryEngine,
-			TypeConfiguration typeConfiguration) {
-		SqmExtractUnit<?> field = (SqmExtractUnit<?>) arguments.get(0);
-		SqmExpression<?> to = (SqmExpression<?>) arguments.get(2);
-		return queryEngine.getSqmFunctionRegistry()
-				.patternDescriptorBuilder(
-						"timestampadd",
-						dialect.timestampaddPattern(
+	public void render(
+			SqlAppender sqlAppender,
+			List<SqlAstNode> arguments,
+			SqlAstWalker walker) {
+
+		DurationUnit field = (DurationUnit) arguments.get(0);
+		Expression to = (Expression) arguments.get(2);
+
+		String pattern = dialect.timestampaddPattern(
 				field.getUnit(),
-								typeConfiguration.isTimestampType( to.getNodeType() )
-						)
-				)
-				.setExactArgumentCount( 3 )
-				.setReturnTypeResolver( useArgType( 3 ) )
-				.descriptor()
-				.generateSqmExpression(
-						arguments,
-						impliedResultType,
-						queryEngine,
-						typeConfiguration
+				TypeConfiguration.isSqlTimestampType( to.getExpressionType() )
 		);
+
+		new PatternRenderer( pattern ).render( sqlAppender, arguments, walker );
 	}
 
+//	@Override
+//	protected <T> SelfRenderingSqlFunctionExpression<T> generateSqmFunctionExpression(
+//			List<SqmTypedNode<?>> arguments,
+//			AllowableFunctionReturnType<T> impliedResultType,
+//			QueryEngine queryEngine,
+//			TypeConfiguration typeConfiguration) {
+//		SqmExtractUnit<?> field = (SqmExtractUnit<?>) arguments.get(0);
+//		SqmExpression<?> to = (SqmExpression<?>) arguments.get(2);
+//		return queryEngine.getSqmFunctionRegistry()
+//				.patternDescriptorBuilder(
+//						"timestampadd",
+//						dialect.timestampaddPattern(
+//								field.getUnit(),
+//								typeConfiguration.isSqlTimestampType( to.getNodeType() )
+//						)
+//				)
+//				.setExactArgumentCount( 3 )
+//				.setReturnTypeResolver( useArgType( 3 ) )
+//				.descriptor()
+//				.generateSqmExpression(
+//						arguments,
+//						impliedResultType,
+//						queryEngine,
+//						typeConfiguration
+//				);
+//	}
+
 	public SelfRenderingFunctionSqlAstExpression expression(
 			AllowableFunctionReturnType<?> impliedResultType,
 			SqlAstNode... sqlAstArguments) {
-		DurationUnit field = (DurationUnit) sqlAstArguments[0];
 		Expression to = (Expression) sqlAstArguments[2];
 		return new SelfRenderingFunctionSqlAstExpression(
-				new PatternRenderer(
-						dialect.timestampaddPattern(
-								field.getUnit(),
-								isSqlTimestampType( to.getExpressionType() )
-						)
-				)::render,
+				(sqlAppender, sqlAstArguments1, walker)
+						-> render(sqlAppender, sqlAstArguments1, walker),
 				asList( sqlAstArguments ),
 				impliedResultType,
 				to.getExpressionType()

hibernate-core/src/main/java/org/hibernate/dialect/function/TimestampdiffFunction.java

@@ -8,16 +8,13 @@ package org.hibernate.dialect.function;
 
 import org.hibernate.dialect.Dialect;
 import org.hibernate.metamodel.model.domain.AllowableFunctionReturnType;
-import org.hibernate.query.spi.QueryEngine;
-import org.hibernate.query.sqm.function.AbstractSqmFunctionDescriptor;
+import org.hibernate.query.sqm.function.AbstractSqmSelfRenderingFunctionDescriptor;
 import org.hibernate.query.sqm.function.SelfRenderingFunctionSqlAstExpression;
-import org.hibernate.query.sqm.function.SelfRenderingSqlFunctionExpression;
 import org.hibernate.query.sqm.produce.function.StandardArgumentsValidators;
 import org.hibernate.query.sqm.produce.function.StandardFunctionReturnTypeResolvers;
 import org.hibernate.query.sqm.produce.function.internal.PatternRenderer;
-import org.hibernate.query.sqm.tree.SqmTypedNode;
-import org.hibernate.query.sqm.tree.expression.SqmExpression;
-import org.hibernate.query.sqm.tree.expression.SqmExtractUnit;
+import org.hibernate.sql.ast.SqlAstWalker;
+import org.hibernate.sql.ast.spi.SqlAppender;
 import org.hibernate.sql.ast.tree.SqlAstNode;
 import org.hibernate.sql.ast.tree.expression.DurationUnit;
 import org.hibernate.sql.ast.tree.expression.Expression;
@@ -27,13 +24,12 @@ import org.hibernate.type.spi.TypeConfiguration;
 import java.util.List;
 
 import static java.util.Arrays.asList;
-import static org.hibernate.type.spi.TypeConfiguration.isSqlTimestampType;
 
 /**
  * @author Gavin King
  */
 public class TimestampdiffFunction
-		extends AbstractSqmFunctionDescriptor {
+		extends AbstractSqmSelfRenderingFunctionDescriptor {
 
 	private Dialect dialect;
 
@@ -47,48 +43,60 @@ public class TimestampdiffFunction
 	}
 
 	@Override
-	protected <T> SelfRenderingSqlFunctionExpression<T> generateSqmFunctionExpression(
-			List<SqmTypedNode<?>> arguments,
-			AllowableFunctionReturnType<T> impliedResultType,
-			QueryEngine queryEngine,
-			TypeConfiguration typeConfiguration) {
-		SqmExtractUnit<?> field = (SqmExtractUnit<?>) arguments.get(0);
-		SqmExpression<?> from = (SqmExpression<?>) arguments.get(1);
-		SqmExpression<?> to = (SqmExpression<?>) arguments.get(2);
-		return queryEngine.getSqmFunctionRegistry()
-				.patternDescriptorBuilder(
-						"timestampdiff",
-						dialect.timestampdiffPattern(
+	public void render(
+			SqlAppender sqlAppender,
+			List<SqlAstNode> arguments,
+			SqlAstWalker walker) {
+
+		DurationUnit field = (DurationUnit) arguments.get(0);
+		Expression from = (Expression) arguments.get(1);
+		Expression to = (Expression) arguments.get(2);
+
+		String pattern = dialect.timestampdiffPattern(
 				field.getUnit(),
-								typeConfiguration.isTimestampType( from.getNodeType() ),
-								typeConfiguration.isTimestampType( to.getNodeType() )
-						)
-				)
-				.setInvariantType( StandardBasicTypes.LONG )
-				.setExactArgumentCount( 3 )
-				.descriptor()
-				.generateSqmExpression(
-						arguments,
-						impliedResultType,
-						queryEngine,
-						typeConfiguration
+				TypeConfiguration.isSqlTimestampType( from.getExpressionType() ),
+				TypeConfiguration.isSqlTimestampType( to.getExpressionType() )
 		);
+
+		new PatternRenderer( pattern ).render( sqlAppender, arguments, walker );
 	}
 
+//	@Override
+//	protected <T> SelfRenderingSqlFunctionExpression<T> generateSqmFunctionExpression(
+//			List<SqmTypedNode<?>> arguments,
+//			AllowableFunctionReturnType<T> impliedResultType,
+//			QueryEngine queryEngine,
+//			TypeConfiguration typeConfiguration) {
+//		SqmExtractUnit<?> field = (SqmExtractUnit<?>) arguments.get(0);
+//		SqmExpression<?> from = (SqmExpression<?>) arguments.get(1);
+//		SqmExpression<?> to = (SqmExpression<?>) arguments.get(2);
+//		return queryEngine.getSqmFunctionRegistry()
+//				.patternDescriptorBuilder(
+//						"timestampdiff",
+//						dialect.timestampdiffPattern(
+//								field.getUnit(),
+//								typeConfiguration.isSqlTimestampType( from.getNodeType() ),
+//								typeConfiguration.isSqlTimestampType( to.getNodeType() )
+//						)
+//				)
+//				.setInvariantType( StandardBasicTypes.LONG )
+//				.setExactArgumentCount( 3 )
+//				.descriptor()
+//				.generateSqmExpression(
+//						arguments,
+//						impliedResultType,
+//						queryEngine,
+//						typeConfiguration
+//				);
+//	}
+
 	public SelfRenderingFunctionSqlAstExpression expression(
 			AllowableFunctionReturnType<?> impliedResultType,
 			SqlAstNode... sqlAstArguments) {
 		DurationUnit field = (DurationUnit) sqlAstArguments[0];
-		Expression from = (Expression) sqlAstArguments[1];
-		Expression to = (Expression) sqlAstArguments[2];
 		return new SelfRenderingFunctionSqlAstExpression(
-				new PatternRenderer(
-						dialect.timestampdiffPattern(
-								field.getUnit(),
-								isSqlTimestampType( from.getExpressionType() ),
-								isSqlTimestampType( to.getExpressionType() )
-						)
-				)::render,
+				(sqlAppender, sqlAstArguments1, walker)
+						-> render(sqlAppender, sqlAstArguments1, walker),
 				asList( sqlAstArguments ),
 				impliedResultType,
 				field.getExpressionType()

hibernate-core/src/main/java/org/hibernate/dialect/function/TrimFunction.java

@@ -7,19 +7,18 @@
 package org.hibernate.dialect.function;
 
 import org.hibernate.dialect.Dialect;
-import org.hibernate.metamodel.model.domain.AllowableFunctionReturnType;
 import org.hibernate.query.TrimSpec;
-import org.hibernate.query.spi.QueryEngine;
-import org.hibernate.query.sqm.function.AbstractSqmFunctionDescriptor;
-import org.hibernate.query.sqm.function.SelfRenderingSqlFunctionExpression;
+import org.hibernate.query.sqm.function.AbstractSqmSelfRenderingFunctionDescriptor;
 import org.hibernate.query.sqm.produce.function.StandardArgumentsValidators;
 import org.hibernate.query.sqm.produce.function.StandardFunctionReturnTypeResolvers;
-import org.hibernate.query.sqm.tree.SqmTypedNode;
-import org.hibernate.query.sqm.tree.expression.SqmExpression;
-import org.hibernate.query.sqm.tree.expression.SqmLiteral;
-import org.hibernate.query.sqm.tree.expression.SqmTrimSpecification;
+import org.hibernate.query.sqm.produce.function.internal.PatternRenderer;
+import org.hibernate.sql.ast.SqlAstWalker;
+import org.hibernate.sql.ast.spi.SqlAppender;
+import org.hibernate.sql.ast.tree.SqlAstNode;
+import org.hibernate.sql.ast.tree.expression.Expression;
+import org.hibernate.sql.ast.tree.expression.QueryLiteral;
+import org.hibernate.sql.ast.tree.expression.TrimSpecification;
 import org.hibernate.type.StandardBasicTypes;
-import org.hibernate.type.spi.TypeConfiguration;
 
 import java.util.Collections;
 import java.util.List;
@@ -27,7 +26,7 @@ import java.util.List;
 /**
  * @author Gavin King
  */
-public class TrimFunction extends AbstractSqmFunctionDescriptor {
+public class TrimFunction extends AbstractSqmSelfRenderingFunctionDescriptor {
 
 	private Dialect dialect;
 
@@ -41,30 +40,41 @@ public class TrimFunction extends AbstractSqmFunctionDescriptor {
 	}
 
 	@Override
-	@SuppressWarnings("unchecked")
-	public <T> SelfRenderingSqlFunctionExpression<T> generateSqmFunctionExpression(
-			List<SqmTypedNode<?>> arguments,
-			AllowableFunctionReturnType<T> impliedResultType,
-			QueryEngine queryEngine,
-			TypeConfiguration typeConfiguration) {
-		final TrimSpec specification = ( (SqmTrimSpecification) arguments.get( 0 ) ).getSpecification();
-		final char trimCharacter = ( (SqmLiteral<Character>) arguments.get( 1 ) ).getLiteralValue();
-		final SqmExpression sourceExpr = (SqmExpression) arguments.get( 2 );
+	public void render(SqlAppender sqlAppender, List<SqlAstNode> sqlAstArguments, SqlAstWalker walker) {
+		final TrimSpec specification = ( (TrimSpecification) sqlAstArguments.get( 0 ) ).getSpecification();
+		final Character trimCharacter = ( (QueryLiteral<Character>) sqlAstArguments.get( 1 ) ).getLiteralValue();
+		final Expression sourceExpr = (Expression) sqlAstArguments.get( 2 );
 
 		String trim = dialect.trimPattern( specification, trimCharacter );
-		return queryEngine.getSqmFunctionRegistry()
-				.patternDescriptorBuilder( "trim", trim )
-				.setInvariantType( StandardBasicTypes.STRING )
-				.setExactArgumentCount( 1 )
-				.descriptor() //TODO: we could cache the 6 variations here
-				.generateSqmExpression(
-						Collections.singletonList( sourceExpr ),
-						impliedResultType,
-						queryEngine,
-						typeConfiguration
-				);
+
+		new PatternRenderer( trim ).render( sqlAppender, Collections.singletonList( sourceExpr ), walker );
 	}
 
+//	@Override
+//	@SuppressWarnings("unchecked")
+//	public <T> SelfRenderingSqlFunctionExpression<T> generateSqmFunctionExpression(
+//			List<SqmTypedNode<?>> arguments,
+//			AllowableFunctionReturnType<T> impliedResultType,
+//			QueryEngine queryEngine,
+//			TypeConfiguration typeConfiguration) {
+//		final TrimSpec specification = ( (SqmTrimSpecification) arguments.get( 0 ) ).getSpecification();
+//		final char trimCharacter = ( (SqmLiteral<Character>) arguments.get( 1 ) ).getLiteralValue();
+//		final SqmExpression sourceExpr = (SqmExpression) arguments.get( 2 );
+//
+//		String trim = dialect.trimPattern( specification, trimCharacter );
+//		return queryEngine.getSqmFunctionRegistry()
+//				.patternDescriptorBuilder( "trim", trim )
+//				.setInvariantType( StandardBasicTypes.STRING )
+//				.setExactArgumentCount( 1 )
+//				.descriptor() //TODO: we could cache the 6 variations here
+//				.generateSqmExpression(
+//						Collections.singletonList( sourceExpr ),
+//						impliedResultType,
+//						queryEngine,
+//						typeConfiguration
+//				);
+//	}
+
 	@Override
 	public String getArgumentListSignature() {
 		return "([[{leading|trailing|both} ][arg0 ]from] arg1)";

hibernate-core/src/main/java/org/hibernate/persister/entity/SingleTableEntityPersister.java

@@ -927,7 +927,7 @@ public class SingleTableEntityPersister extends AbstractEntityPersister {
 				ComparisonOperator.EQUAL,
 				new QueryLiteral<>(
 						getDiscriminatorValue(),
-						( (BasicType) getDiscriminatorType() )
+						( (BasicType<?>) getDiscriminatorType() )
 				)
 		);
 	}

hibernate-core/src/main/java/org/hibernate/query/hql/internal/SemanticQueryBuilder.java

@@ -2243,7 +2243,7 @@ public class SemanticQueryBuilder extends HqlParserBaseVisitor implements SqmCre
 		final List<SqmTypedNode<?>> arguments = new ArrayList<>();
 
 		if ( ctx.datetimeField() != null ) {
-			arguments.add( (SqmTypedNode<?>) ctx.datetimeField().accept( this ) );
+			arguments.add( toDurationUnit( (SqmExtractUnit<?>) ctx.datetimeField().accept( this ) ) );
 		}
 
 		for ( int i=0, size=ctx.expression().size(); i<size; i++ ) {

hibernate-core/src/main/java/org/hibernate/query/sqm/function/AbstractSqmFunctionDescriptor.java

@@ -75,9 +75,6 @@ public abstract class AbstractSqmFunctionDescriptor implements SqmFunctionDescri
 	}
 
 	private static SqlAstNode toSqlAstNode(Object arg, SqmToSqlAstConverter walker) {
-//		if (arg instanceof SqmExpressionInterpretation) {
-//			return ( (SqmExpressionInterpretation) arg ).toSqlExpression( walker );
-//		}
 		return (SqlAstNode) arg;
 	}
 
@@ -95,7 +92,7 @@ public abstract class AbstractSqmFunctionDescriptor implements SqmFunctionDescri
 	}
 
 	@Override
-	public final <T> SelfRenderingSqlFunctionExpression<T> generateSqmExpression(
+	public final <T> SelfRenderingSqmFunction<T> generateSqmExpression(
 			List<SqmTypedNode<?>> arguments,
 			AllowableFunctionReturnType<T> impliedResultType,
 			QueryEngine queryEngine,
@@ -110,11 +107,18 @@ public abstract class AbstractSqmFunctionDescriptor implements SqmFunctionDescri
 		);
 	}
 
-	protected abstract <T> SelfRenderingSqlFunctionExpression<T> generateSqmFunctionExpression(
+	/**
+	 * Return an SQM node or subtree representing an invocation of this function
+	 * with the given arguments. This method may be overridden in the case of
+	 * function descriptors that wish to customize creation of the node.
+	 *
+	 * @param arguments the arguments of the function invocation
+	 * @param impliedResultType the function return type as inferred from its usage
+	 */
+	protected abstract <T> SelfRenderingSqmFunction<T> generateSqmFunctionExpression(
 			List<SqmTypedNode<?>> arguments,
 			AllowableFunctionReturnType<T> impliedResultType,
-			QueryEngine queryEngine, TypeConfiguration typeConfiguration);
-
-
+			QueryEngine queryEngine,
+			TypeConfiguration typeConfiguration);
 }
 

hibernate-core/src/main/java/org/hibernate/query/sqm/function/AbstractSqmSelfRenderingFunctionDescriptor.java

@@ -5,6 +5,9 @@ import org.hibernate.query.spi.QueryEngine;
 import org.hibernate.query.sqm.produce.function.ArgumentsValidator;
 import org.hibernate.query.sqm.produce.function.FunctionReturnTypeResolver;
 import org.hibernate.query.sqm.tree.SqmTypedNode;
+import org.hibernate.sql.ast.SqlAstWalker;
+import org.hibernate.sql.ast.spi.SqlAppender;
+import org.hibernate.sql.ast.tree.SqlAstNode;
 import org.hibernate.type.spi.TypeConfiguration;
 
 import java.util.List;
@@ -13,22 +16,22 @@ import java.util.List;
  * @author Gavin King
  */
 public abstract class AbstractSqmSelfRenderingFunctionDescriptor
-		extends AbstractSqmFunctionDescriptor
-		implements SqmSelfRenderingFunctionDescriptor {
+		extends AbstractSqmFunctionDescriptor {
 
 	public AbstractSqmSelfRenderingFunctionDescriptor(String name, ArgumentsValidator argumentsValidator, FunctionReturnTypeResolver returnTypeResolver) {
 		super( name, argumentsValidator, returnTypeResolver );
 	}
 
 	@Override
-	protected <T> SelfRenderingSqlFunctionExpression<T> generateSqmFunctionExpression(
+	protected <T> SelfRenderingSqmFunction<T> generateSqmFunctionExpression(
 			List<SqmTypedNode<?>> arguments,
 			AllowableFunctionReturnType<T> impliedResultType,
 			QueryEngine queryEngine,
 			TypeConfiguration typeConfiguration) {
-		return new SelfRenderingSqlFunctionExpression<T>(
+		return new SelfRenderingSqmFunction<T>(
 				this,
-				getRenderingSupport(),
+				(sqlAppender, sqlAstArguments, walker)
+						-> render(sqlAppender, sqlAstArguments, walker),
 				arguments,
 				impliedResultType,
 				getReturnTypeResolver(),
@@ -37,4 +40,12 @@ public abstract class AbstractSqmSelfRenderingFunctionDescriptor
 		);
 	}
 
+	/**
+	 * Must be overridden by subclasses
+	 */
+	public abstract void render(
+			SqlAppender sqlAppender,
+			List<SqlAstNode> sqlAstArguments,
+			SqlAstWalker walker);
+
 }

hibernate-core/src/main/java/org/hibernate/query/sqm/function/FunctionRenderingSupport.java

@@ -13,8 +13,12 @@ import org.hibernate.sql.ast.tree.SqlAstNode;
 import java.util.List;
 
 /**
- * Support for SqmFunctionTemplates that ultimately want to
- * perform SQL rendering themselves
+ * Support for {@link SqmFunctionDescriptor}s that ultimately want
+ * to perform SQL rendering themselves. This is a protocol passed
+ * from the {@link AbstractSqmSelfRenderingFunctionDescriptor}
+ * along to its {@link SelfRenderingSqmFunction} and ultimately to
+ * the {@link SelfRenderingFunctionSqlAstExpression} which calls it
+ * to finally render SQL.
  *
  * @author Steve Ebersole
  */

hibernate-core/src/main/java/org/hibernate/query/sqm/function/JdbcEscapeFunctionDescriptor.java

@@ -9,16 +9,17 @@ package org.hibernate.query.sqm.function;
 import org.hibernate.metamodel.model.domain.AllowableFunctionReturnType;
 import org.hibernate.query.spi.QueryEngine;
 import org.hibernate.query.sqm.tree.SqmTypedNode;
-import org.hibernate.query.sqm.tree.expression.SqmJdbcFunctionEscapeWrapper;
 import org.hibernate.type.spi.TypeConfiguration;
 
 import java.util.List;
 
 /**
- * Acts as a wrapper to another SqmFunctionTemplate - upon rendering uses the
- * standard JDBC escape sequence (i.e. `{fn blah}`) when rendering the SQL.
+ * Acts as a wrapper to another {@link SqmFunctionDescriptor}, rendering the
+ * standard JDBC escape sequence {@code {fn f(x, y)}} around the invocation
+ * syntax generated by its delegate.
  *
  * @author Steve Ebersole
+ * @author Gavin King
  */
 public class JdbcEscapeFunctionDescriptor
 		extends AbstractSqmFunctionDescriptor {
@@ -30,20 +31,32 @@ public class JdbcEscapeFunctionDescriptor
 	}
 
 	@Override
-	protected <T> SelfRenderingSqlFunctionExpression<T> generateSqmFunctionExpression(
+	protected <T> SelfRenderingSqmFunction<T> generateSqmFunctionExpression(
 			List<SqmTypedNode<?>> arguments,
 			AllowableFunctionReturnType<T> impliedResultType,
 			QueryEngine queryEngine,
 			TypeConfiguration typeConfiguration) {
-		return new SqmJdbcFunctionEscapeWrapper<>(
-				this,
+
+		final SelfRenderingSqmFunction<T> delegate =
 				wrapped.generateSqmExpression(
 						arguments,
 						impliedResultType,
 						queryEngine,
 						typeConfiguration
-				),
-				queryEngine.getCriteriaBuilder()
 				);
+
+		return new SelfRenderingSqmFunction<T>(
+				JdbcEscapeFunctionDescriptor.this,
+				(sqlAppender, sqlAstArguments, walker) -> {
+					sqlAppender.appendSql("{fn ");
+					delegate.getRenderingSupport()
+							.render(sqlAppender, sqlAstArguments, walker);
+					sqlAppender.appendSql("}");
+				},
+				arguments,
+				impliedResultType,
+				getReturnTypeResolver(),
+				queryEngine.getCriteriaBuilder(),
+				getName());
 	}
 }

hibernate-core/src/main/java/org/hibernate/query/sqm/function/MultipatternSqmFunctionDescriptor.java

@@ -56,7 +56,8 @@ public class MultipatternSqmFunctionDescriptor extends AbstractSqmFunctionDescri
 	public MultipatternSqmFunctionDescriptor(
 			String name, SqmFunctionDescriptor[] functions,
 			FunctionReturnTypeResolver type) {
-		super("",
+		super(
+				name,
 				StandardArgumentsValidators.between(
 					first(functions),
 					last(functions)
@@ -67,7 +68,7 @@ public class MultipatternSqmFunctionDescriptor extends AbstractSqmFunctionDescri
 	}
 
 	@Override
-	protected <T> SelfRenderingSqlFunctionExpression<T> generateSqmFunctionExpression(
+	protected <T> SelfRenderingSqmFunction<T> generateSqmFunctionExpression(
 			List<SqmTypedNode<?>> arguments,
 			AllowableFunctionReturnType<T> impliedResultType,
 			QueryEngine queryEngine,

hibernate-core/src/main/java/org/hibernate/query/sqm/function/NamedSqmFunctionDescriptor.java

@@ -25,8 +25,7 @@ import java.util.Locale;
  * @author Steve Ebersole
  */
 public class NamedSqmFunctionDescriptor
-		extends AbstractSqmSelfRenderingFunctionDescriptor
-		implements FunctionRenderingSupport {
+		extends AbstractSqmSelfRenderingFunctionDescriptor {
 	private final String functionName;
 	private final boolean useParenthesesWhenNoArgs;
 	private final String argumentListSignature;
@@ -72,11 +71,6 @@ public class NamedSqmFunctionDescriptor
 		return useParenthesesWhenNoArgs;
 	}
 
-	@Override
-	public FunctionRenderingSupport getRenderingSupport() {
-		return this;
-	}
-
 	@Override
 	public void render(
 			SqlAppender sqlAppender,

hibernate-core/src/main/java/org/hibernate/query/sqm/function/PatternBasedSqmFunctionDescriptor.java

@@ -35,8 +35,7 @@ import java.util.List;
  * @author <a href="mailto:alex@jboss.org">Alexey Loubyansky</a>
  */
 public class PatternBasedSqmFunctionDescriptor
-		extends AbstractSqmSelfRenderingFunctionDescriptor
-		implements FunctionRenderingSupport {
+		extends AbstractSqmSelfRenderingFunctionDescriptor {
 	private final PatternRenderer renderer;
 	private final String argumentListSignature;
 
@@ -66,11 +65,6 @@ public class PatternBasedSqmFunctionDescriptor
 		this.argumentListSignature = argumentListSignature;
 	}
 
-	@Override
-	public FunctionRenderingSupport getRenderingSupport() {
-		return this;
-	}
-
 	@Override
 	public void render(
 			SqlAppender sqlAppender,

hibernate-core/src/main/java/org/hibernate/query/sqm/function/SelfRenderingFunctionSqlAstExpression.java

@@ -121,7 +121,7 @@ public class SelfRenderingFunctionSqlAstExpression
 			SqlAppender sqlAppender,
 			SqlAstWalker walker,
 			SessionFactoryImplementor sessionFactory) {
-		renderer.render( sqlAppender, sqlAstArguments, walker);
+		renderer.render( sqlAppender, sqlAstArguments, walker );
 	}
 
 	@Override

hibernate-core/src/main/java/org/hibernate/query/sqm/function/SelfRenderingSqmFunction.java

@@ -26,14 +26,14 @@ import static java.util.Collections.emptyList;
 /**
  * @author Steve Ebersole
  */
-public class SelfRenderingSqlFunctionExpression<T> extends SqmFunction<T> {
+public class SelfRenderingSqmFunction<T> extends SqmFunction<T> {
 	private final AllowableFunctionReturnType<T> impliedResultType;
 	private final FunctionReturnTypeResolver returnTypeResolver;
 	private final String name;
 	private final FunctionRenderingSupport renderingSupport;
 	private final List<SqmTypedNode<?>> arguments;
 
-	public SelfRenderingSqlFunctionExpression(
+	public SelfRenderingSqmFunction(
 			SqmFunctionDescriptor descriptor,
 			FunctionRenderingSupport renderingSupport,
 			List<SqmTypedNode<?>> arguments,

hibernate-core/src/main/java/org/hibernate/query/sqm/function/SqmFunctionDescriptor.java

@@ -39,7 +39,7 @@ public interface SqmFunctionDescriptor {
 	 * simplifying the task of writing HQL functions which are
 	 * portable between databases.
 	 */
-	<T> SelfRenderingSqlFunctionExpression<T> generateSqmExpression(
+	<T> SelfRenderingSqmFunction<T> generateSqmExpression(
 			List<SqmTypedNode<?>> arguments,
 			AllowableFunctionReturnType<T> impliedResultType,
 			QueryEngine queryEngine,
@@ -48,7 +48,7 @@ public interface SqmFunctionDescriptor {
 	/**
 	 * Convenience for single argument
 	 */
-	default <T> SelfRenderingSqlFunctionExpression<T> generateSqmExpression(
+	default <T> SelfRenderingSqmFunction<T> generateSqmExpression(
 			SqmTypedNode<?> argument,
 			AllowableFunctionReturnType<T> impliedResultType,
 			QueryEngine queryEngine,
@@ -64,7 +64,7 @@ public interface SqmFunctionDescriptor {
 	/**
 	 * Convenience for no arguments
 	 */
-	default <T> SelfRenderingSqlFunctionExpression<T> generateSqmExpression(
+	default <T> SelfRenderingSqmFunction<T> generateSqmExpression(
 			AllowableFunctionReturnType<T> impliedResultType,
 			QueryEngine queryEngine,
 			TypeConfiguration typeConfiguration) {

hibernate-core/src/main/java/org/hibernate/query/sqm/function/SqmSelfRenderingFunctionDescriptor.java

@@ -1,14 +0,0 @@
-/*
- * 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.query.sqm.function;
-
-/**
- * @author Steve Ebersole
- */
-public interface SqmSelfRenderingFunctionDescriptor extends SqmFunctionDescriptor {
-	FunctionRenderingSupport getRenderingSupport();
-}

hibernate-core/src/main/java/org/hibernate/query/sqm/mutation/internal/idtable/ExecuteWithIdTableHelper.java

@@ -116,7 +116,7 @@ public final class ExecuteWithIdTableHelper {
 					new SqlSelectionImpl(
 							jdbcPosition,
 							jdbcPosition + 1,
-							new QueryLiteral(
+							new QueryLiteral<>(
 									sessionUidAccess.apply( executionContext.getSession() ),
 									StandardBasicTypes.STRING
 							)
@@ -215,7 +215,7 @@ public final class ExecuteWithIdTableHelper {
 									executionContext.getSession().getFactory()
 							),
 							ComparisonOperator.EQUAL,
-							new QueryLiteral(
+							new QueryLiteral<>(
 									sessionUidAccess.apply( executionContext.getSession() ),
 									UUIDCharType.INSTANCE
 							)

hibernate-core/src/main/java/org/hibernate/query/sqm/produce/function/NamedFunctionDescriptorBuilder.java

@@ -10,7 +10,6 @@ import org.hibernate.query.sqm.function.NamedSqmFunctionDescriptor;
 import org.hibernate.query.sqm.function.SqmFunctionDescriptor;
 import org.hibernate.query.sqm.function.SqmFunctionRegistry;
 import org.hibernate.type.BasicType;
-import org.hibernate.type.StandardBasicTypes;
 
 /**
  * @author Steve Ebersole
@@ -72,10 +71,10 @@ public class NamedFunctionDescriptorBuilder {
 	}
 
 	public SqmFunctionDescriptor register() {
-		return registry.register( registrationKey, template() );
+		return registry.register( registrationKey, descriptor() );
 	}
 
-	public SqmFunctionDescriptor template() {
+	public SqmFunctionDescriptor descriptor() {
 		return new NamedSqmFunctionDescriptor(
 				functionName,
 				useParenthesesWhenNoArgs,

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

@@ -859,10 +859,10 @@ public abstract class BaseSqmToSqlAstConverter
 	@Override
 	public Expression visitLiteral(SqmLiteral literal) {
 		if ( literal instanceof SqmLiteralNull ) {
-			return new QueryLiteral( null, (BasicValuedMapping) inferableTypeAccessStack.getCurrent().get() );
+			return new QueryLiteral<>( null, (BasicValuedMapping) inferableTypeAccessStack.getCurrent().get() );
 		}
 
-		return new QueryLiteral(
+		return new QueryLiteral<>(
 				literal.getLiteralValue(),
 				(BasicValuedMapping) SqmMappingModelHelper.resolveMappingModelExpressable(
 						literal,
@@ -1527,8 +1527,8 @@ public abstract class BaseSqmToSqlAstConverter
 
 			boolean durationToRight = TypeConfiguration.isDuration( rightOperand.getNodeType() );
 			TypeConfiguration typeConfiguration = getCreationContext().getDomainModel().getTypeConfiguration();
-			boolean temporalTypeToLeft = typeConfiguration.isTemporalType( leftOperand.getNodeType() );
-			boolean temporalTypeToRight = typeConfiguration.isTemporalType( rightOperand.getNodeType() );
+			boolean temporalTypeToLeft = typeConfiguration.isSqlTemporalType( leftOperand.getNodeType() );
+			boolean temporalTypeToRight = typeConfiguration.isSqlTemporalType( rightOperand.getNodeType() );
 			boolean temporalTypeSomewhereToLeft = adjustedTimestamp != null || temporalTypeToLeft;
 
 			if (temporalTypeToLeft && durationToRight) {
@@ -1684,8 +1684,8 @@ public abstract class BaseSqmToSqlAstConverter
 		Expression right = cleanly(() -> toSqlExpression( expression.getRightHandOperand().accept(this) ));
 
 		TypeConfiguration typeConfiguration = getCreationContext().getDomainModel().getTypeConfiguration();
-		boolean leftTimestamp = typeConfiguration.isTimestampType( expression.getLeftHandOperand().getNodeType() ) ;
-		boolean rightTimestamp = typeConfiguration.isTimestampType( expression.getRightHandOperand().getNodeType() );
+		boolean leftTimestamp = typeConfiguration.isSqlTimestampType( expression.getLeftHandOperand().getNodeType() ) ;
+		boolean rightTimestamp = typeConfiguration.isSqlTimestampType( expression.getRightHandOperand().getNodeType() );
 
 		// when we're dealing with Dates, we use
 		// DAY as the smallest unit, otherwise we
@@ -1819,9 +1819,10 @@ public abstract class BaseSqmToSqlAstConverter
 		return magnitude;
 	}
 
+	@SuppressWarnings("unchecked")
 	static boolean isOne(Expression scale) {
 		return scale instanceof QueryLiteral
-				&& ((QueryLiteral) scale).getLiteralValue().toString().equals("1");
+				&& ((QueryLiteral<Number>) scale).getLiteralValue().longValue() == 1L;
 	}
 
 	@Override
@@ -1954,7 +1955,7 @@ public abstract class BaseSqmToSqlAstConverter
 
 	@Override
 	public Object visitEnumLiteral(SqmEnumLiteral sqmEnumLiteral) {
-		return new QueryLiteral(
+		return new QueryLiteral<>(
 				sqmEnumLiteral.getEnumValue(),
 				(BasicValuedMapping) determineValueMapping( sqmEnumLiteral )
 		);
@@ -1962,7 +1963,7 @@ public abstract class BaseSqmToSqlAstConverter
 
 	@Override
 	public Object visitFieldLiteral(SqmFieldLiteral sqmFieldLiteral) {
-		return new QueryLiteral(
+		return new QueryLiteral<>(
 				sqmFieldLiteral.getValue(),
 				(BasicValuedMapping) determineValueMapping( sqmFieldLiteral )
 		);

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

@@ -6,7 +6,6 @@
  */
 package org.hibernate.query.sqm.tree.expression;
 
-import org.hibernate.NotYetImplementedFor6Exception;
 import org.hibernate.metamodel.model.domain.AllowableFunctionReturnType;
 import org.hibernate.query.TemporalUnit;
 import org.hibernate.query.sqm.NodeBuilder;

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

@@ -1,53 +0,0 @@
-/*
- * 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.query.sqm.tree.expression;
-
-import org.hibernate.metamodel.model.domain.AllowableFunctionReturnType;
-import org.hibernate.query.sqm.NodeBuilder;
-import org.hibernate.query.sqm.function.SelfRenderingSqlFunctionExpression;
-import org.hibernate.query.sqm.function.SqmFunctionDescriptor;
-
-/**
- * Adds a JDBC function escape (i.e. `{fn <wrapped-function-call>})  around the wrapped function
- *
- * @author Steve Ebersole
- * @author Gavin King
- */
-public class SqmJdbcFunctionEscapeWrapper<T>
-		extends SelfRenderingSqlFunctionExpression<T> {
-	private final SelfRenderingSqlFunctionExpression<?> wrappedSqmFunction;
-
-	public SqmJdbcFunctionEscapeWrapper(
-			SqmFunctionDescriptor fun,
-			SelfRenderingSqlFunctionExpression<T> wrappedSqmFunction,
-			NodeBuilder nodeBuilder) {
-		super(
-				fun,
-				(sqlAppender, sqlAstArguments, walker) -> {
-					sqlAppender.appendSql( "{fn " );
-					wrappedSqmFunction.getRenderingSupport().render(
-							sqlAppender,
-							sqlAstArguments,
-							walker
-					);
-					sqlAppender.appendSql( "}" );
-				},
-				wrappedSqmFunction.getArguments(),
-				(AllowableFunctionReturnType<T>) wrappedSqmFunction.getNodeType(),
-				null, //TODO!!!!!!
-				nodeBuilder,
-				wrappedSqmFunction.getFunctionName()
-		);
-		this.wrappedSqmFunction = wrappedSqmFunction;
-	}
-
-	@Override
-	public String asLoggableText() {
-		return "wrapped-function[ " + wrappedSqmFunction.asLoggableText() + " ]";
-	}
-
-}

hibernate-core/src/main/java/org/hibernate/sql/ast/tree/expression/QueryLiteral.java

@@ -34,16 +34,16 @@ import org.hibernate.type.spi.TypeConfiguration;
  * @author Steve Ebersole
  */
 public class QueryLiteral<T> implements Literal, DomainResultProducer<T> {
-	private final Object value;
+	private final T value;
 	private final BasicValuedMapping type;
 
-	public QueryLiteral(Object value, BasicValuedMapping type) {
+	public QueryLiteral(T value, BasicValuedMapping type) {
 		this.value = value;
 		this.type = type;
 	}
 
 	@Override
-	public Object getLiteralValue() {
+	public T getLiteralValue() {
 		return value;
 	}
 
@@ -98,7 +98,7 @@ public class QueryLiteral<T> implements Literal, DomainResultProducer<T> {
 			JdbcParameterBindings jdbcParameterBindings,
 			ExecutionContext executionContext) throws SQLException {
 		//noinspection unchecked
-		( (BasicType) getExpressionType() ).getJdbcValueBinder().bind(
+		( (BasicType<?>) getExpressionType() ).getJdbcValueBinder().bind(
 				statement,
 				getLiteralValue(),
 				startPosition,

hibernate-core/src/main/java/org/hibernate/type/spi/TypeConfiguration.java

@@ -46,6 +46,7 @@ import org.hibernate.query.sqm.SqmExpressable;
 import org.hibernate.service.ServiceRegistry;
 import org.hibernate.type.BasicType;
 import org.hibernate.type.BasicTypeRegistry;
+import org.hibernate.type.SingleColumnType;
 import org.hibernate.type.StandardBasicTypes;
 import org.hibernate.type.descriptor.java.JavaTypeDescriptor;
 import org.hibernate.type.descriptor.java.spi.JavaTypeDescriptorRegistry;
@@ -473,8 +474,8 @@ public class TypeConfiguration implements SessionFactoryObserver, Serializable {
 			SqmExpressable<?> secondType,
 			boolean isDivision) {
 
-		if ( isTemporalType( firstType ) ) {
-			if ( secondType==null || isTemporalType( secondType ) ) {
+		if ( isSqlTemporalType( firstType ) ) {
+			if ( secondType==null || isSqlTemporalType( secondType ) ) {
 				// special case for subtraction of two dates
 				// or timestamps resulting in a duration
 				return getBasicTypeRegistry().getRegisteredType( Duration.class );
@@ -490,7 +491,7 @@ public class TypeConfiguration implements SessionFactoryObserver, Serializable {
 			// or prefix scalar multiplication of a duration
 			return secondType;
 		}
-		else if ( firstType==null && isTemporalType( secondType ) ) {
+		else if ( firstType==null && isSqlTemporalType( secondType ) ) {
 			// subtraction of a date or timestamp from a
 			// parameter (which doesn't have a type yet)
 			return getBasicTypeRegistry().getRegisteredType( Duration.class );
@@ -613,33 +614,40 @@ public class TypeConfiguration implements SessionFactoryObserver, Serializable {
 		);
 	}
 
-	public boolean isTimestampType(SqmExpressable type) {
+	public boolean isSqlTimestampType(SqmExpressable type) {
 		return type != null
-				&& isTimestampType( type.getExpressableJavaTypeDescriptor().getJdbcRecommendedSqlType( getCurrentBaseSqlTypeIndicators() ) );
-	}
-
-	public static boolean isTimestampType(SqlTypeDescriptor descriptor) {
-		int jdbcTypeCode = descriptor.getJdbcTypeCode();
-		return jdbcTypeCode == Types.TIMESTAMP
-				|| jdbcTypeCode == Types.TIMESTAMP_WITH_TIMEZONE;
+				&& isSqlTimestampType( type.getExpressableJavaTypeDescriptor().getJdbcRecommendedSqlType( getCurrentBaseSqlTypeIndicators() ) );
 	}
 
 	public static boolean isSqlTimestampType(MappingModelExpressable type) {
 		if ( type instanceof BasicValuedMapping ) {
 			return isSqlTimestampType( ( (BasicValuedMapping) type ).getJdbcMapping().getSqlTypeDescriptor() );
 		}
-
+		else if (type instanceof SingleColumnType) {
+			return isSqlTimestampType( ((SingleColumnType) type).sqlType() );
+		}
 		return false;
 	}
 
 	public static boolean isSqlTimestampType(SqlTypeDescriptor descriptor) {
-		int jdbcTypeCode = descriptor.getJdbcTypeCode();
+		return isSqlTimestampType( descriptor.getJdbcTypeCode() );
+	}
+
+	protected static boolean isSqlTimestampType(int jdbcTypeCode) {
 		return jdbcTypeCode == Types.TIMESTAMP
 				|| jdbcTypeCode == Types.TIMESTAMP_WITH_TIMEZONE;
 	}
 
-	public static boolean isTemporalType(SqlTypeDescriptor descriptor) {
-		int jdbcTypeCode = descriptor.getJdbcTypeCode();
+	public static boolean isSqlTemporalType(SqlTypeDescriptor descriptor) {
+		return isSqlTemporalType( descriptor.getJdbcTypeCode() );
+	}
+
+	public boolean isSqlTemporalType(SqmExpressable<?> type) {
+		return type != null
+				&& isSqlTemporalType( type.getExpressableJavaTypeDescriptor().getJdbcRecommendedSqlType( getCurrentBaseSqlTypeIndicators() ) );
+	}
+
+	private static boolean isSqlTemporalType(int jdbcTypeCode) {
 		return jdbcTypeCode == Types.TIMESTAMP
 				|| jdbcTypeCode == Types.TIMESTAMP_WITH_TIMEZONE
 				|| jdbcTypeCode == Types.TIME
@@ -647,10 +655,6 @@ public class TypeConfiguration implements SessionFactoryObserver, Serializable {
 				|| jdbcTypeCode == Types.DATE;
 	}
 
-	public boolean isTemporalType(SqmExpressable<?> type) {
-		return type != null
-				&& isTemporalType( type.getExpressableJavaTypeDescriptor().getJdbcRecommendedSqlType( getCurrentBaseSqlTypeIndicators() ) );
-	}
 
 	public static boolean isJdbcTemporalType(SqmExpressable<?> type) {
 		return matchesJavaType( type, Date.class );