Encapsulate implementation details

Author: hazzik

src/NHibernate/Hql/Ast/ANTLR/SqlGenerator.cs

@@ -313,7 +313,7 @@ private void EndFunctionTemplate(IASTNode m)
 		private void OutAggregateFunctionName(IASTNode m)
 		{
 			var aggregateNode = (AggregateNode) m;
-			Out(aggregateNode.SqlFunction?.FunctionName ?? aggregateNode.Text);
+			Out(aggregateNode.SqlFunctionName());
 		}
 
 		private void CommaBetweenParameters(String comma)

src/NHibernate/Hql/Ast/ANTLR/Tree/AggregateNode.cs

@@ -34,9 +34,20 @@ public override IType DataType
 				base.DataType = value;
 			}
 		}
+		
 		public override void SetScalarColumnText(int i)
 		{
 			ColumnHelper.GenerateSingleScalarColumn(ASTFactory, this, i);
 		}
+
+		public string SqlFunctionName()
+		{
+			if (SessionFactoryHelper.FindSQLFunction(Text) is ISQLFunctionExtended sqlFunction)
+			{
+				return sqlFunction.FunctionName;
+			}
+
+			return Text;
+		}
 	}
 }