Make Render method virtual for Cast function (#2406)

Author: maca88

src/NHibernate/Dialect/Function/CastFunction.cs

@@ -54,7 +54,7 @@ public bool HasParenthesesIfNoArguments
 			get { return true; }
 		}
 
-		public SqlString Render(IList args, ISessionFactoryImplementor factory)
+		public virtual SqlString Render(IList args, ISessionFactoryImplementor factory)
 		{
 			if (args.Count != 2)
 			{
@@ -87,23 +87,36 @@ public SqlString Render(IList args, ISessionFactoryImplementor factory)
 				throw new QueryException(string.Format("invalid Hibernate type for cast(): type {0} not found", typeName));
 			}
 
-			if (CastingIsRequired(sqlType))
-			{
-				return new SqlString("cast(", args[0], " as ", sqlType, ")");
-			}
-			else
-			{
+			// TODO 6.0: Remove pragma block with its content
+#pragma warning disable 618
+			if (!CastingIsRequired(sqlType))
 				return new SqlString("(", args[0], ")");
-			}
+#pragma warning restore 618
+
+			return Render(args[0], sqlType, factory);
 		}
 
 		#endregion
 
+		// Since v5.3
+		[Obsolete("This method has no usages and will be removed in a future version")]
 		protected virtual bool CastingIsRequired(string sqlType)
 		{
 			return true;
 		}
 
+		/// <summary>
+		/// Renders the SQL fragment representing the SQL cast.
+		/// </summary>
+		/// <param name="expression">The cast argument.</param>
+		/// <param name="sqlType">The SQL type to cast to.</param>
+		/// <param name="factory">The session factory.</param>
+		/// <returns>A SQL fragment.</returns>
+		protected virtual SqlString Render(object expression, string sqlType, ISessionFactoryImplementor factory)
+		{
+			return new SqlString("cast(", expression, " as ", sqlType, ")");
+		}
+
 		#region IFunctionGrammar Members
 
 		bool IFunctionGrammar.IsSeparator(string token)

src/NHibernate/Dialect/Function/TransparentCastFunction.cs

@@ -1,4 +1,7 @@
 using System;
+using System.Collections;
+using NHibernate.Engine;
+using NHibernate.SqlCommand;
 
 namespace NHibernate.Dialect.Function
 {
@@ -8,9 +11,23 @@ namespace NHibernate.Dialect.Function
 	[Serializable]
 	public class TransparentCastFunction : CastFunction
 	{
+		// Since v5.3
+		[Obsolete("This method has no usages and will be removed in a future version")]
 		protected override bool CastingIsRequired(string sqlType)
 		{
 			return false;
 		}
+
+		/// <summary>
+		/// Renders the SQL fragment representing the casted expression without actually casting it.
+		/// </summary>
+		/// <param name="expression">The cast argument.</param>
+		/// <param name="sqlType">The SQL type to cast to, ignored for rendering.</param>
+		/// <param name="factory">The session factory.</param>
+		/// <returns>A SQL fragment.</returns>
+		protected override SqlString Render(object expression, string sqlType, ISessionFactoryImplementor factory)
+		{
+			return new SqlString("(", expression, ")");
+		}
 	}
 }

src/NHibernate/Dialect/SQLiteDialect.cs

@@ -510,6 +510,8 @@ public override bool SupportsForeignKeyConstraintInAlterTable
 		[Serializable]
 		protected class SQLiteCastFunction : CastFunction
 		{
+			// Since v5.3
+			[Obsolete("This method has no usages and will be removed in a future version")]
 			protected override bool CastingIsRequired(string sqlType)
 			{
 				if (StringHelper.ContainsCaseInsensitive(sqlType, "date") ||