Fix issues in definite assignment analysis.

NRefactory/ICSharpCode.NRefactory.Tests/CSharp/Analysis/DefiniteAssignmentTests.cs

@@ -0,0 +1,132 @@
+// Copyright (c) AlphaSierraPapa for the SharpDevelop Team (for details please see \doc\copyright.txt)
+// This code is distributed under MIT X11 license (for details please see \doc\license.txt)
+
+using System;
+using System.Linq;
+using NUnit.Framework;
+
+namespace ICSharpCode.NRefactory.CSharp.Analysis
+{
+	[TestFixture]
+	public class DefiniteAssignmentTests
+	{
+		[Test]
+		public void TryFinally()
+		{
+			BlockStatement block = new BlockStatement {
+				new TryCatchStatement {
+					TryBlock = new BlockStatement {
+						new GotoStatement("LABEL"),
+						new AssignmentExpression(new IdentifierExpression("i"), new PrimitiveExpression(1))
+					},
+					CatchClauses = {
+						new CatchClause {
+							Body = new BlockStatement {
+								new AssignmentExpression(new IdentifierExpression("i"), new PrimitiveExpression(3))
+							}
+						}
+					},
+					FinallyBlock = new BlockStatement {
+						new AssignmentExpression(new IdentifierExpression("j"), new PrimitiveExpression(5))
+					}
+				},
+				new LabelStatement { Label = "LABEL" },
+				new EmptyStatement()
+			};
+			TryCatchStatement tryCatchStatement = (TryCatchStatement)block.Statements.First();
+			Statement stmt1 = tryCatchStatement.TryBlock.Statements.ElementAt(1);
+			Statement stmt3 = tryCatchStatement.CatchClauses.Single().Body.Statements.Single();
+			Statement stmt5 = tryCatchStatement.FinallyBlock.Statements.Single();
+			LabelStatement label = (LabelStatement)block.Statements.ElementAt(1);
+			
+			DefiniteAssignmentAnalysis da = new DefiniteAssignmentAnalysis(block);
+			da.Analyze("i");
+			Assert.AreEqual(0, da.UnassignedVariableUses.Count);
+			Assert.AreEqual(DefiniteAssignmentStatus.PotentiallyAssigned, da.GetStatusBefore(tryCatchStatement));
+			Assert.AreEqual(DefiniteAssignmentStatus.CodeUnreachable, da.GetStatusBefore(stmt1));
+			Assert.AreEqual(DefiniteAssignmentStatus.CodeUnreachable, da.GetStatusAfter(stmt1));
+			Assert.AreEqual(DefiniteAssignmentStatus.PotentiallyAssigned, da.GetStatusBefore(stmt3));
+			Assert.AreEqual(DefiniteAssignmentStatus.DefinitelyAssigned, da.GetStatusAfter(stmt3));
+			Assert.AreEqual(DefiniteAssignmentStatus.PotentiallyAssigned, da.GetStatusBefore(stmt5));
+			Assert.AreEqual(DefiniteAssignmentStatus.PotentiallyAssigned, da.GetStatusAfter(stmt5));
+			Assert.AreEqual(DefiniteAssignmentStatus.DefinitelyAssigned, da.GetStatusAfter(tryCatchStatement));
+			Assert.AreEqual(DefiniteAssignmentStatus.DefinitelyAssigned, da.GetStatusBefore(label));
+			Assert.AreEqual(DefiniteAssignmentStatus.PotentiallyAssigned, da.GetStatusAfter(label));
+			
+			da.Analyze("j");
+			Assert.AreEqual(0, da.UnassignedVariableUses.Count);
+			Assert.AreEqual(DefiniteAssignmentStatus.PotentiallyAssigned, da.GetStatusBefore(tryCatchStatement));
+			Assert.AreEqual(DefiniteAssignmentStatus.CodeUnreachable, da.GetStatusBefore(stmt1));
+			Assert.AreEqual(DefiniteAssignmentStatus.CodeUnreachable, da.GetStatusAfter(stmt1));
+			Assert.AreEqual(DefiniteAssignmentStatus.PotentiallyAssigned, da.GetStatusBefore(stmt3));
+			Assert.AreEqual(DefiniteAssignmentStatus.PotentiallyAssigned, da.GetStatusAfter(stmt3));
+			Assert.AreEqual(DefiniteAssignmentStatus.PotentiallyAssigned, da.GetStatusBefore(stmt5));
+			Assert.AreEqual(DefiniteAssignmentStatus.DefinitelyAssigned, da.GetStatusAfter(stmt5));
+			Assert.AreEqual(DefiniteAssignmentStatus.DefinitelyAssigned, da.GetStatusAfter(tryCatchStatement));
+			Assert.AreEqual(DefiniteAssignmentStatus.DefinitelyAssigned, da.GetStatusBefore(label));
+			Assert.AreEqual(DefiniteAssignmentStatus.DefinitelyAssigned, da.GetStatusAfter(label));
+		}
+		
+		[Test]
+		public void ConditionalAnd()
+		{
+			IfElseStatement ifStmt = new IfElseStatement {
+				Condition = new BinaryOperatorExpression {
+					Left = new BinaryOperatorExpression(new IdentifierExpression("x"), BinaryOperatorType.GreaterThan, new PrimitiveExpression(0)),
+					Operator = BinaryOperatorType.ConditionalAnd,
+					Right = new BinaryOperatorExpression {
+						Left = new ParenthesizedExpression {
+							Expression = new AssignmentExpression {
+								Left = new IdentifierExpression("i"),
+								Operator = AssignmentOperatorType.Assign,
+								Right = new IdentifierExpression("y")
+							}
+						},
+						Operator = BinaryOperatorType.GreaterThanOrEqual,
+						Right = new PrimitiveExpression(0)
+					}
+				},
+				TrueStatement = new BlockStatement(),
+				FalseStatement = new BlockStatement()
+			};
+			DefiniteAssignmentAnalysis da = new DefiniteAssignmentAnalysis(ifStmt);
+			da.Analyze("i");
+			Assert.AreEqual(0, da.UnassignedVariableUses.Count);
+			Assert.AreEqual(DefiniteAssignmentStatus.PotentiallyAssigned, da.GetStatusBefore(ifStmt));
+			Assert.AreEqual(DefiniteAssignmentStatus.DefinitelyAssigned, da.GetStatusBefore(ifStmt.TrueStatement));
+			Assert.AreEqual(DefiniteAssignmentStatus.PotentiallyAssigned, da.GetStatusBefore(ifStmt.FalseStatement));
+			Assert.AreEqual(DefiniteAssignmentStatus.PotentiallyAssigned, da.GetStatusAfter(ifStmt));
+		}
+		
+		[Test]
+		public void ConditionalOr()
+		{
+			IfElseStatement ifStmt = new IfElseStatement {
+				Condition = new BinaryOperatorExpression {
+					Left = new BinaryOperatorExpression(new IdentifierExpression("x"), BinaryOperatorType.GreaterThan, new PrimitiveExpression(0)),
+					Operator = BinaryOperatorType.ConditionalOr,
+					Right = new BinaryOperatorExpression {
+						Left = new ParenthesizedExpression {
+							Expression = new AssignmentExpression {
+								Left = new IdentifierExpression("i"),
+								Operator = AssignmentOperatorType.Assign,
+								Right = new IdentifierExpression("y")
+							}
+						},
+						Operator = BinaryOperatorType.GreaterThanOrEqual,
+						Right = new PrimitiveExpression(0)
+					}
+				},
+				TrueStatement = new BlockStatement(),
+				FalseStatement = new BlockStatement()
+			};
+			DefiniteAssignmentAnalysis da = new DefiniteAssignmentAnalysis(ifStmt);
+			da.Analyze("i");
+			Assert.AreEqual(0, da.UnassignedVariableUses.Count);
+			Assert.AreEqual(DefiniteAssignmentStatus.PotentiallyAssigned, da.GetStatusBefore(ifStmt));
+			Assert.AreEqual(DefiniteAssignmentStatus.PotentiallyAssigned, da.GetStatusBefore(ifStmt.TrueStatement));
+			Assert.AreEqual(DefiniteAssignmentStatus.DefinitelyAssigned, da.GetStatusBefore(ifStmt.FalseStatement));
+			Assert.AreEqual(DefiniteAssignmentStatus.PotentiallyAssigned, da.GetStatusAfter(ifStmt));
+		}
+	}
+}

NRefactory/ICSharpCode.NRefactory.Tests/ICSharpCode.NRefactory.Tests.csproj

@@ -59,6 +59,7 @@
     </Reference>
   </ItemGroup>
   <ItemGroup>
+    <Compile Include="CSharp\Analysis\DefiniteAssignmentTests.cs" />
     <Compile Include="CSharp\AstStructureTests.cs" />
     <Compile Include="CSharp\InsertParenthesesVisitorTests.cs" />
     <Compile Include="CSharp\Parser\GeneralScope\DelegateDeclarationTests.cs" />
@@ -162,6 +163,7 @@
     </ProjectReference>
   </ItemGroup>
   <ItemGroup>
+    <Folder Include="CSharp\Analysis" />
     <Folder Include="CSharp\Parser\Expression" />
     <Folder Include="CSharp\Parser\GeneralScope" />
     <Folder Include="CSharp\Parser\TypeMembers" />

NRefactory/ICSharpCode.NRefactory/CSharp/Analysis/ControlFlow.cs

@@ -79,6 +79,7 @@ namespace ICSharpCode.NRefactory.CSharp.Analysis
 		{
 			if (jumpOutOfTryFinally == null)
 				jumpOutOfTryFinally = new List<TryCatchStatement>();
+			jumpOutOfTryFinally.Add(tryFinally);
 		}
 		
 		/// <summary>

NRefactory/ICSharpCode.NRefactory/CSharp/Analysis/DefiniteAssignmentAnalysis.cs

@@ -6,6 +6,7 @@ using System.Collections.Generic;
 using System.Diagnostics;
 using System.Linq;
 using ICSharpCode.NRefactory.CSharp.Resolver;
+using ICSharpCode.NRefactory.Utils;
 
 namespace ICSharpCode.NRefactory.CSharp.Analysis
 {
@@ -19,10 +20,6 @@ namespace ICSharpCode.NRefactory.CSharp.Analysis
 		/// </summary>
 		PotentiallyAssigned,
 		/// <summary>
-		/// The variable is definitely unassigned.
-		/// </summary>
-		DefinitelyUnassigned,
-		/// <summary>
 		/// The variable is definitely assigned.
 		/// </summary>
 		DefinitelyAssigned,
@@ -82,7 +79,16 @@ namespace ICSharpCode.NRefactory.CSharp.Analysis
 			}
 		}
 		
-		public void Analyze(string variable, DefiniteAssignmentStatus initialStatus = DefiniteAssignmentStatus.DefinitelyUnassigned)
+		/// <summary>
+		/// Gets the unassigned usages of the previously analyzed variable.
+		/// </summary>
+		public IList<IdentifierExpression> UnassignedVariableUses {
+			get {
+				return unassignedVariableUses.AsReadOnly();
+			}
+		}
+		
+		public void Analyze(string variable, DefiniteAssignmentStatus initialStatus = DefiniteAssignmentStatus.PotentiallyAssigned)
 		{
 			this.variableName = variable;
 			// Reset the status:
@@ -93,7 +99,7 @@ namespace ICSharpCode.NRefactory.CSharp.Analysis
 					edgeStatus[edge] = DefiniteAssignmentStatus.CodeUnreachable;
 			}
 			
-			ChangeNodeStatus(allNodes[0], DefiniteAssignmentStatus.DefinitelyUnassigned);
+			ChangeNodeStatus(allNodes[0], initialStatus);
 			// Iterate as long as the input status of some nodes is changing:
 			while (nodesWithModifiedInput.Count > 0) {
 				ControlFlowNode node = nodesWithModifiedInput.Dequeue();
@@ -105,6 +111,64 @@ namespace ICSharpCode.NRefactory.CSharp.Analysis
 			}
 		}
 		
+		public DefiniteAssignmentStatus GetStatusBefore(Statement statement)
+		{
+			return nodeStatus[beginNodeDict[statement]];
+		}
+		
+		public DefiniteAssignmentStatus GetStatusAfter(Statement statement)
+		{
+			return nodeStatus[endNodeDict[statement]];
+		}
+		
+		/// <summary>
+		/// Exports the CFG. This method is intended to help debugging issues related to definite assignment.
+		/// </summary>
+		public GraphVizGraph ExportGraph()
+		{
+			GraphVizGraph g = new GraphVizGraph();
+			g.Title = "DefiniteAssignment - " + variableName;
+			for (int i = 0; i < allNodes.Count; i++) {
+				string name = nodeStatus[allNodes[i]].ToString() + Environment.NewLine;
+				switch (allNodes[i].Type) {
+					case ControlFlowNodeType.StartNode:
+					case ControlFlowNodeType.BetweenStatements:
+						name += allNodes[i].NextStatement.ToString();
+						break;
+					case ControlFlowNodeType.EndNode:
+						name += "End of " + allNodes[i].PreviousStatement.ToString();
+						break;
+					case ControlFlowNodeType.LoopCondition:
+						name += "Condition in " + allNodes[i].NextStatement.ToString();
+						break;
+					default:
+						name += allNodes[i].Type.ToString();
+						break;
+				}
+				g.AddNode(new GraphVizNode(i) { label = name });
+				foreach (ControlFlowEdge edge in allNodes[i].Outgoing) {
+					GraphVizEdge ge = new GraphVizEdge(i, allNodes.IndexOf(edge.To));
+					if (edgeStatus.Count > 0)
+						ge.label = edgeStatus[edge].ToString();
+					if (edge.IsLeavingTryFinally)
+						ge.style = "dashed";
+					switch (edge.Type) {
+						case ControlFlowEdgeType.ConditionTrue:
+							ge.color = "green";
+							break;
+						case ControlFlowEdgeType.ConditionFalse:
+							ge.color = "red";
+							break;
+						case ControlFlowEdgeType.Jump:
+							ge.color = "blue";
+							break;
+					}
+					g.AddEdge(ge);
+				}
+			}
+			return g;
+		}
+		
 		static DefiniteAssignmentStatus MergeStatus(DefiniteAssignmentStatus a, DefiniteAssignmentStatus b)
 		{
 			// The result will be DefinitelyAssigned if at least one incoming edge is DefinitelyAssigned and all others are unreachable.
@@ -151,9 +215,11 @@ namespace ICSharpCode.NRefactory.CSharp.Analysis
 						TryCatchStatement tryFinally = (TryCatchStatement)node.PreviousStatement.Parent;
 						// Changing the status on a finally block potentially changes the status of all edges leaving that finally block:
 						foreach (ControlFlowEdge edge in allNodes.SelectMany(n => n.Outgoing)) {
-							DefiniteAssignmentStatus s = edgeStatus[edge];
-							if (s == DefiniteAssignmentStatus.DefinitelyUnassigned || s == DefiniteAssignmentStatus.PotentiallyAssigned) {
-								ChangeEdgeStatus(edge, outputStatus);
+							if (edge.IsLeavingTryFinally && edge.TryFinallyStatements.Contains(tryFinally)) {
+								DefiniteAssignmentStatus s = edgeStatus[edge];
+								if (s == DefiniteAssignmentStatus.PotentiallyAssigned) {
+									ChangeEdgeStatus(edge, outputStatus);
+								}
 							}
 						}
 					}
@@ -197,19 +263,18 @@ namespace ICSharpCode.NRefactory.CSharp.Analysis
 			if (oldStatus == newStatus)
 				return;
 			// Ensure that status can change only in one direction:
-			// CodeUnreachable -> PotentiallyAssigned -> Definitely[Un]Assigned
+			// CodeUnreachable -> PotentiallyAssigned -> DefinitelyAssigned
 			// Going against this direction indicates a bug and could cause infinite loops.
-			switch (newStatus) {
+			switch (oldStatus) {
 				case DefiniteAssignmentStatus.PotentiallyAssigned:
-					if (oldStatus != DefiniteAssignmentStatus.CodeUnreachable)
+					if (newStatus != DefiniteAssignmentStatus.DefinitelyAssigned)
 						throw new InvalidOperationException("Invalid state transition");
 					break;
-				case DefiniteAssignmentStatus.DefinitelyUnassigned:
-				case DefiniteAssignmentStatus.DefinitelyAssigned:
-					if (!(oldStatus == DefiniteAssignmentStatus.CodeUnreachable || oldStatus == DefiniteAssignmentStatus.PotentiallyAssigned))
+				case DefiniteAssignmentStatus.CodeUnreachable:
+					if (!(newStatus == DefiniteAssignmentStatus.PotentiallyAssigned || newStatus == DefiniteAssignmentStatus.DefinitelyAssigned))
 						throw new InvalidOperationException("Invalid state transition");
 					break;
-				case DefiniteAssignmentStatus.CodeUnreachable:
+				case DefiniteAssignmentStatus.DefinitelyAssigned:
 					throw new InvalidOperationException("Invalid state transition");
 				default:
 					throw new InvalidOperationException("Invalid value for DefiniteAssignmentStatus");
@@ -449,8 +514,6 @@ namespace ICSharpCode.NRefactory.CSharp.Analysis
 						return DefiniteAssignmentStatus.AssignedAfterTrueExpression;
 					else if (afterLeft == DefiniteAssignmentStatus.AssignedAfterFalseExpression && afterRight == DefiniteAssignmentStatus.AssignedAfterFalseExpression)
 						return DefiniteAssignmentStatus.AssignedAfterFalseExpression;
-					else if (afterRight == DefiniteAssignmentStatus.DefinitelyUnassigned)
-						return afterRight;
 					else
 						return DefiniteAssignmentStatus.PotentiallyAssigned;
 				} else if (binaryOperatorExpression.Operator == BinaryOperatorType.ConditionalOr) {
@@ -477,8 +540,6 @@ namespace ICSharpCode.NRefactory.CSharp.Analysis
 						return DefiniteAssignmentStatus.AssignedAfterFalseExpression;
 					else if (afterLeft == DefiniteAssignmentStatus.AssignedAfterTrueExpression && afterRight == DefiniteAssignmentStatus.AssignedAfterTrueExpression)
 						return DefiniteAssignmentStatus.AssignedAfterTrueExpression;
-					else if (afterRight == DefiniteAssignmentStatus.DefinitelyUnassigned)
-						return DefiniteAssignmentStatus.DefinitelyUnassigned;
 					else
 						return DefiniteAssignmentStatus.PotentiallyAssigned;
 				} else if (binaryOperatorExpression.Operator == BinaryOperatorType.NullCoalescing) {

NRefactory/ICSharpCode.NRefactory/CSharp/Ast/DepthFirstAstVisitor.cs

@@ -1,4 +1,4 @@
-// 
+// 
 // IAstVisitor.cs
 //
 // Author:
@@ -52,17 +52,17 @@ namespace ICSharpCode.NRefactory.CSharp
 		
 		public virtual S VisitComment (Comment comment, T data)
 		{
-			return default (S);
+			return VisitChildren (comment, data);
 		}
 		
 		public virtual S VisitIdentifier (Identifier identifier, T data)
 		{
-			return default (S);
+			return VisitChildren (identifier, data);
 		}
 		
 		public virtual S VisitCSharpTokenNode (CSharpTokenNode token, T data)
 		{
-			return default (S);
+			return VisitChildren (token, data);
 		}
 		
 		public virtual S VisitPrimitiveType (PrimitiveType primitiveType, T data)

NRefactory/ICSharpCode.NRefactory/CSharp/Ast/Expressions/Expression.cs

@@ -54,6 +54,8 @@ namespace ICSharpCode.NRefactory.CSharp
 		// Make debugging easier by giving Expressions a ToString() implementation
 		public override string ToString()
 		{
+			if (IsNull)
+				return "Null";
 			StringWriter w = new StringWriter();
 			AcceptVisitor(new OutputVisitor(w, new CSharpFormattingPolicy()), null);
 			return w.ToString();

NRefactory/ICSharpCode.NRefactory/CSharp/Ast/Statements/Statement.cs

@@ -2,6 +2,7 @@
 // This code is distributed under MIT X11 license (for details please see \doc\license.txt)
 
 using System;
+using System.IO;
 
 namespace ICSharpCode.NRefactory.CSharp
 {
@@ -52,5 +53,19 @@ namespace ICSharpCode.NRefactory.CSharp
 		public override NodeType NodeType {
 			get { return NodeType.Statement; }
 		}
+		
+		// Make debugging easier by giving Statements a ToString() implementation
+		public override string ToString()
+		{
+			if (IsNull)
+				return "Null";
+			StringWriter w = new StringWriter();
+			AcceptVisitor(new OutputVisitor(w, new CSharpFormattingPolicy()), null);
+			string text = w.ToString().TrimEnd().Replace("\t", "").Replace(w.NewLine, " ");
+			if (text.Length > 100)
+				return text.Substring(0, 97) + "...";
+			else
+				return text;
+		}
 	}
 }

NRefactory/ICSharpCode.NRefactory/ICSharpCode.NRefactory.csproj

@@ -334,6 +334,7 @@
     <Compile Include="Utils\DotNet35Compat.cs" />
     <Compile Include="Utils\EmptyList.cs" />
     <Compile Include="Utils\ExtensionMethods.cs" />
+    <Compile Include="Utils\GraphVizGraph.cs" />
     <Compile Include="Utils\TreeTraversal.cs" />
     <Compile Include="CSharp\Ast\ComposedType.cs" />
     <Compile Include="CSharp\Ast\Expressions\DirectionExpression.cs" />

NRefactory/ICSharpCode.NRefactory/Utils/GraphVizGraph.cs

@@ -0,0 +1,204 @@
+// Copyright (c) 2010 AlphaSierraPapa for the SharpDevelop Team (for details please see \doc\copyright.txt)
+// This code is distributed under MIT X11 license (for details please see \doc\license.txt)
+
+using System;
+using System.Collections.Generic;
+using System.Diagnostics;
+using System.Globalization;
+using System.IO;
+using System.Text.RegularExpressions;
+
+namespace ICSharpCode.NRefactory.Utils
+{
+	/// <summary>
+	/// GraphViz graph.
+	/// </summary>
+	public sealed class GraphVizGraph
+	{
+		List<GraphVizNode> nodes = new List<GraphVizNode>();
+		List<GraphVizEdge> edges = new List<GraphVizEdge>();
+		
+		public string rankdir;
+		public string Title;
+		
+		public void AddEdge(GraphVizEdge edge)
+		{
+			edges.Add(edge);
+		}
+		
+		public void AddNode(GraphVizNode node)
+		{
+			nodes.Add(node);
+		}
+		
+		public void Save(string fileName)
+		{
+			using (StreamWriter writer = new StreamWriter(fileName))
+				Save(writer);
+		}
+		
+		public void Show()
+		{
+			Show(null);
+		}
+		
+		public void Show(string name)
+		{
+			if (name == null)
+				name = Title;
+			if (name != null)
+				foreach (char c in Path.GetInvalidFileNameChars())
+					name = name.Replace(c, '-');
+			string fileName = name != null ? Path.Combine(Path.GetTempPath(), name) : Path.GetTempFileName();
+			Save(fileName + ".gv");
+			Process.Start("dot", "\"" + fileName + ".gv\" -Tpng -o \"" + fileName + ".png\"").WaitForExit();
+			Process.Start(fileName + ".png");
+		}
+		
+		static string Escape(string text)
+		{
+			if (Regex.IsMatch(text, @"^[\w\d]+$")) {
+				return text;
+			} else {
+				return "\"" + text.Replace("\\", "\\\\").Replace("\r", "").Replace("\n", "\\n").Replace("\"", "\\\"") + "\"";
+			}
+		}
+		
+		static void WriteGraphAttribute(TextWriter writer, string name, string value)
+		{
+			if (value != null)
+				writer.WriteLine("{0}={1};", name, Escape(value));
+		}
+		
+		internal static void WriteAttribute(TextWriter writer, string name, double? value, ref bool isFirst)
+		{
+			if (value != null) {
+				WriteAttribute(writer, name, value.Value.ToString(CultureInfo.InvariantCulture), ref isFirst);
+			}
+		}
+		
+		internal static void WriteAttribute(TextWriter writer, string name, bool? value, ref bool isFirst)
+		{
+			if (value != null) {
+				WriteAttribute(writer, name, value.Value ? "true" : "false", ref isFirst);
+			}
+		}
+		
+		internal static void WriteAttribute(TextWriter writer, string name, string value, ref bool isFirst)
+		{
+			if (value != null) {
+				if (isFirst)
+					isFirst = false;
+				else
+					writer.Write(',');
+				writer.Write("{0}={1}", name, Escape(value));
+			}
+		}
+		
+		public void Save(TextWriter writer)
+		{
+			if (writer == null)
+				throw new ArgumentNullException("writer");
+			writer.WriteLine("digraph G {");
+			writer.WriteLine("node [fontsize = 16];");
+			WriteGraphAttribute(writer, "rankdir", rankdir);
+			foreach (GraphVizNode node in nodes) {
+				node.Save(writer);
+			}
+			foreach (GraphVizEdge edge in edges) {
+				edge.Save(writer);
+			}
+			writer.WriteLine("}");
+		}
+	}
+	
+	public sealed class GraphVizEdge
+	{
+		public readonly string Source, Target;
+		
+		/// <summary>edge stroke color</summary>
+		public string color;
+		/// <summary>use edge to affect node ranking</summary>
+		public bool? constraint;
+		
+		public string label;
+		
+		public string style;
+		
+		/// <summary>point size of label</summary>
+		public int? fontsize;
+		
+		public GraphVizEdge(string source, string target)
+		{
+			if (source == null)
+				throw new ArgumentNullException("source");
+			if (target == null)
+				throw new ArgumentNullException("target");
+			this.Source = source;
+			this.Target = target;
+		}
+		
+		public GraphVizEdge(int source, int target)
+		{
+			this.Source = source.ToString(CultureInfo.InvariantCulture);
+			this.Target = target.ToString(CultureInfo.InvariantCulture);
+		}
+		
+		public void Save(TextWriter writer)
+		{
+			writer.Write("{0} -> {1} [", Source, Target);
+			bool isFirst = true;
+			GraphVizGraph.WriteAttribute(writer, "label", label, ref isFirst);
+			GraphVizGraph.WriteAttribute(writer, "style", style, ref isFirst);
+			GraphVizGraph.WriteAttribute(writer, "fontsize", fontsize, ref isFirst);
+			GraphVizGraph.WriteAttribute(writer, "color", color, ref isFirst);
+			GraphVizGraph.WriteAttribute(writer, "constraint", constraint, ref isFirst);
+			writer.WriteLine("];");
+		}
+	}
+	
+	public sealed class GraphVizNode
+	{
+		public readonly string ID;
+		public string label;
+		
+		public string labelloc;
+		
+		/// <summary>point size of label</summary>
+		public int? fontsize;
+		
+		/// <summary>minimum height in inches</summary>
+		public double? height;
+		
+		/// <summary>space around label</summary>
+		public string margin;
+		
+		/// <summary>node shape</summary>
+		public string shape;
+		
+		public GraphVizNode(string id)
+		{
+			if (id == null)
+				throw new ArgumentNullException("id");
+			this.ID = id;
+		}
+		
+		public GraphVizNode(int id)
+		{
+			this.ID = id.ToString(CultureInfo.InvariantCulture);
+		}
+		
+		public void Save(TextWriter writer)
+		{
+			writer.Write(ID);
+			writer.Write(" [");
+			bool isFirst = true;
+			GraphVizGraph.WriteAttribute(writer, "label", label, ref isFirst);
+			GraphVizGraph.WriteAttribute(writer, "labelloc", labelloc, ref isFirst);
+			GraphVizGraph.WriteAttribute(writer, "fontsize", fontsize, ref isFirst);
+			GraphVizGraph.WriteAttribute(writer, "margin", margin, ref isFirst);
+			GraphVizGraph.WriteAttribute(writer, "shape", shape, ref isFirst);
+			writer.WriteLine("];");
+		}
+	}
+}