Fixes nhibernate#3327

AND/OR below NOT must use result of subsequent NegateNode calls
to create a new result node instead of partially mutating the existing
node to consider functional signature of the NegateNode method

Author: csharper2010

src/NHibernate.Test/NHSpecificTest/GH3327/Entity.cs

@@ -0,0 +1,17 @@
+using System;
+
+namespace NHibernate.Test.NHSpecificTest.GH3327
+{
+	public class Entity
+	{
+		public virtual int Id { get; set; }
+ 		public virtual string Name { get; set; }
+	}
+
+	public class ChildEntity
+	{
+		public virtual int Id { get; set; }
+		public virtual Entity Parent { get; set; }
+		public virtual string Name { get; set; }
+	}
+}

src/NHibernate.Test/NHSpecificTest/GH3327/Fixture.cs

@@ -0,0 +1,63 @@
+using System;
+using NUnit.Framework;
+
+namespace NHibernate.Test.NHSpecificTest.GH3327
+{
+	[TestFixture]
+	public class Fixture : BugTestCase
+	{
+		protected override void OnSetUp()
+		{
+			Sfi.Statistics.IsStatisticsEnabled = true;
+		}
+
+		protected override void OnTearDown()
+		{
+			Sfi.Statistics.IsStatisticsEnabled = false;
+			using (var session = OpenSession())
+			using (var transaction = session.BeginTransaction())
+			{
+				session.CreateQuery("delete from ChildEntity").ExecuteUpdate();
+				session.CreateQuery("delete from Entity").ExecuteUpdate();
+
+				transaction.Commit();
+			}
+		}
+
+		[Test]
+		public void NotIsCorrectlyHandled()
+		{
+			using (var session = OpenSession())
+			using (var t = session.BeginTransaction())
+			{
+				var parent = new Entity { Name = "Parent" };
+				var child = new ChildEntity { Name = "Child", Parent = parent };
+				session.Save(parent);
+				session.Save(child);
+				t.Commit();
+			}
+
+			using (var session = OpenSession())
+			using (var _ = session.BeginTransaction())
+			{
+				var q = session.CreateQuery(
+					@"SELECT COUNT(ROOT.Id)
+					FROM Entity AS ROOT
+					WHERE (
+						EXISTS (FROM ChildEntity AS CHILD WHERE CHILD.Parent = ROOT)
+						AND ROOT.Name = 'Parent'
+					)");
+				Assert.That(q.List()[0], Is.EqualTo(1));
+
+				q = session.CreateQuery(
+					@"SELECT COUNT(ROOT.Id)
+					FROM Entity AS ROOT
+					WHERE NOT (
+						EXISTS (FROM ChildEntity AS CHILD WHERE CHILD.Parent = ROOT)
+						AND ROOT.Name = 'Parent'
+					)");
+				Assert.That(q.List()[0], Is.EqualTo(0));
+			}
+		}
+	}
+}

src/NHibernate.Test/NHSpecificTest/GH3327/Mappings.hbm.xml

@@ -0,0 +1,16 @@
+<?xml version="1.0" encoding="utf-8" ?>
+<hibernate-mapping xmlns="urn:nhibernate-mapping-2.2" assembly="NHibernate.Test"
+                   namespace="NHibernate.Test.NHSpecificTest.GH3327">
+
+  <class name="Entity">
+    <id name="Id" generator="identity" />
+    <property name="Name"/>
+  </class>
+
+  <class name="ChildEntity">
+    <id name="Id" generator="identity" />
+    <one-to-one name="Parent" class="Entity" constrained="true" />
+    <property name="Name"/>
+  </class>
+
+</hibernate-mapping>

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

@@ -212,17 +212,17 @@ public IASTNode NegateNode(IASTNode node)
 			switch (node.Type)
 			{
 				case OR:
-					node.Type = AND;
-					node.Text = "{and}";
-					NegateNode(node.GetChild(0));
-					NegateNode(node.GetChild(1));
-					return node;
+					IASTNode newNode = (IASTNode) TreeAdaptor.Create(AND, "{and}");
+					newNode.AddChildren(
+						NegateNode(node.GetChild(0)),
+						NegateNode(node.GetChild(1)));
+					return newNode;
 				case AND:
-					node.Type = OR;
-					node.Text = "{or}";
-					NegateNode(node.GetChild(0));
-					NegateNode(node.GetChild(1));
-					return node;
+					newNode = (IASTNode) TreeAdaptor.Create(OR, "{or}");
+					newNode.AddChildren(
+						NegateNode(node.GetChild(0)),
+						NegateNode(node.GetChild(1)));
+					return newNode;
 				case EQ:
 					node.Type = NE;
 					node.Text = "{not}" + node.Text;