// Copyright (c) AlphaSierraPapa for the SharpDevelop Team
// 
// Permission is hereby granted, free of charge, to any person obtaining a copy of this
// software and associated documentation files (the "Software"), to deal in the Software
// without restriction, including without limitation the rights to use, copy, modify, merge,
// publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons
// to whom the Software is furnished to do so, subject to the following conditions:
// 
// The above copyright notice and this permission notice shall be included in all copies or
// substantial portions of the Software.
// 
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED,
// INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR
// PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE
// FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
// OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
// DEALINGS IN THE SOFTWARE.

using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.Globalization;
using System.IO;
using System.Linq;
using System.Text;

using ICSharpCode.NRefactory.PatternMatching;
using ICSharpCode.NRefactory.TypeSystem;

namespace ICSharpCode.NRefactory.CSharp
{
	/// <summary>
	/// Outputs the AST.
	/// </summary>
	public class OutputVisitor : IAstVisitor<object, object>, IPatternAstVisitor<object, object>
	{
		readonly IOutputFormatter formatter;
		readonly CSharpFormattingOptions policy;
		readonly Stack<AstNode> containerStack = new Stack<AstNode> ();
		readonly Stack<AstNode> positionStack = new Stack<AstNode> ();
		
		/// <summary>
		/// Used to insert the minimal amount of spaces so that the lexer recognizes the tokens that were written.
		/// </summary>
		LastWritten lastWritten;
		
		enum LastWritten
		{
			Whitespace,
			Other,
			KeywordOrIdentifier,
			Plus,
			Minus,
			Ampersand,
			QuestionMark,
			Division
		}
		
		public OutputVisitor (TextWriter textWriter, CSharpFormattingOptions formattingPolicy)
		{
			if (textWriter == null)
				throw new ArgumentNullException ("textWriter");
			if (formattingPolicy == null)
				throw new ArgumentNullException ("formattingPolicy");
			this.formatter = new TextWriterOutputFormatter (textWriter);
			this.policy = formattingPolicy;
		}
		
		public OutputVisitor (IOutputFormatter formatter, CSharpFormattingOptions formattingPolicy)
		{
			if (formatter == null)
				throw new ArgumentNullException ("formatter");
			if (formattingPolicy == null)
				throw new ArgumentNullException ("formattingPolicy");
			this.formatter = formatter;
			this.policy = formattingPolicy;
		}
		
		#region StartNode/EndNode
		public event EventHandler<AstNodeEventArgs> OutputStarted;
		
		protected virtual void OnOutputStarted (AstNodeEventArgs e)
		{
			EventHandler<AstNodeEventArgs> handler = this.OutputStarted;
			if (handler != null)
				handler (this, e);
		}
		
		public event EventHandler<AstNodeEventArgs> OutputFinished;
		
		protected virtual void OnOutputFinished (AstNodeEventArgs e)
		{
			EventHandler<AstNodeEventArgs> handler = this.OutputFinished;
			if (handler != null)
				handler (this, e);
		}
		
		[Serializable]
		public sealed class AstNodeEventArgs : EventArgs
		{
			public AstNode AstNode {
				get;
				private set;
			}
			
			public AstNodeEventArgs (AstNode node)
			{
				this.AstNode = node;
			}
		}
		
		void StartNode (AstNode node)
		{
			// Ensure that nodes are visited in the proper nested order.
			// Jumps to different subtrees are allowed only for the child of a placeholder node.
			Debug.Assert (containerStack.Count == 0 || node.Parent == containerStack.Peek () || containerStack.Peek ().NodeType == NodeType.Pattern);
			if (positionStack.Count > 0)
				WriteSpecialsUpToNode (node);
			containerStack.Push (node);
			positionStack.Push (node.FirstChild);
			OnOutputStarted (new AstNodeEventArgs (node));
			formatter.StartNode (node);
		}
		
		object EndNode (AstNode node)
		{
			Debug.Assert (node == containerStack.Peek ());
			AstNode pos = positionStack.Pop ();
			Debug.Assert (pos == null || pos.Parent == node);
			WriteSpecials (pos, null);
			containerStack.Pop ();
			OnOutputFinished (new AstNodeEventArgs (node));
			formatter.EndNode (node);
			return null;
		}
		#endregion
		
		#region WriteSpecials
		/// <summary>
		/// Writes all specials from start to end (exclusive). Does not touch the positionStack.
		/// </summary>
		void WriteSpecials (AstNode start, AstNode end)
		{
			for (AstNode pos = start; pos != end; pos = pos.NextSibling) {
				if (pos.Role == AstNode.Roles.Comment) {
					pos.AcceptVisitor (this, null);
				}
			}
		}
		
		/// <summary>
		/// Writes all specials between the current position (in the positionStack) and the next
		/// node with the specified role. Advances the current position.
		/// </summary>
		void WriteSpecialsUpToRole (Role role)
		{
			for (AstNode pos = positionStack.Peek(); pos != null; pos = pos.NextSibling) {
				if (pos.Role == role) {
					WriteSpecials (positionStack.Pop (), pos);
					positionStack.Push (pos);
					break;
				}
			}
		}
		
		/// <summary>
		/// Writes all specials between the current position (in the positionStack) and the specified node.
		/// Advances the current position.
		/// </summary>
		void WriteSpecialsUpToNode (AstNode node)
		{
			for (AstNode pos = positionStack.Peek(); pos != null; pos = pos.NextSibling) {
				if (pos == node) {
					WriteSpecials (positionStack.Pop (), pos);
					positionStack.Push (pos);
					break;
				}
			}
		}
		
		void WriteSpecialsUpToRole (Role role, AstNode nextNode)
		{
			// Look for the role between the current position and the nextNode.
			for (AstNode pos = positionStack.Peek(); pos != null && pos != nextNode; pos = pos.NextSibling) {
				if (pos.Role == AstNode.Roles.Comma) {
					WriteSpecials (positionStack.Pop (), pos);
					positionStack.Push (pos);
					break;
				}
			}
		}
		#endregion
		
		#region Comma
		/// <summary>
		/// Writes a comma.
		/// </summary>
		/// <param name="nextNode">The next node after the comma.</param>
		/// <param name="noSpacesAfterComma">When set prevents printing a space after comma.</param>
		void Comma (AstNode nextNode, bool noSpaceAfterComma = false)
		{
			WriteSpecialsUpToRole (AstNode.Roles.Comma, nextNode);
			Space (policy.SpaceBeforeBracketComma); // TODO: Comma policy has changed.
			formatter.WriteToken (",");
			lastWritten = LastWritten.Other;
			Space (!noSpaceAfterComma && policy.SpaceAfterBracketComma); // TODO: Comma policy has changed.
		}
		
		void WriteCommaSeparatedList (IEnumerable<AstNode> list)
		{
			bool isFirst = true;
			foreach (AstNode node in list) {
				if (isFirst) {
					isFirst = false;
				} else {
					Comma (node);
				}
				node.AcceptVisitor (this, null);
			}
		}
		
		void WriteCommaSeparatedListInParenthesis (IEnumerable<AstNode> list, bool spaceWithin)
		{
			LPar ();
			if (list.Any ()) {
				Space (spaceWithin);
				WriteCommaSeparatedList (list);
				Space (spaceWithin);
			}
			RPar ();
		}
		
		#if DOTNET35
		void WriteCommaSeparatedList(IEnumerable<VariableInitializer> list)
		{
			WriteCommaSeparatedList(list.SafeCast<VariableInitializer, AstNode>());
		}
		
		void WriteCommaSeparatedList(IEnumerable<AstType> list)
		{
			WriteCommaSeparatedList(list.SafeCast<AstType, AstNode>());
		}
		
		void WriteCommaSeparatedListInParenthesis(IEnumerable<Expression> list, bool spaceWithin)
		{
			WriteCommaSeparatedListInParenthesis(list.SafeCast<Expression, AstNode>(), spaceWithin);
		}
		
		void WriteCommaSeparatedListInParenthesis(IEnumerable<ParameterDeclaration> list, bool spaceWithin)
		{
			WriteCommaSeparatedListInParenthesis(list.SafeCast<ParameterDeclaration, AstNode>(), spaceWithin);
		}

		#endif

		void WriteCommaSeparatedListInBrackets (IEnumerable<ParameterDeclaration> list, bool spaceWithin)
		{
			WriteToken ("[", AstNode.Roles.LBracket);
			if (list.Any ()) {
				Space (spaceWithin);
				WriteCommaSeparatedList (list.SafeCast<ParameterDeclaration, AstNode> ());
				Space (spaceWithin);
			}
			WriteToken ("]", AstNode.Roles.RBracket);
		}

		void WriteCommaSeparatedListInBrackets (IEnumerable<Expression> list)
		{
			WriteToken ("[", AstNode.Roles.LBracket);
			if (list.Any ()) {
				Space (policy.SpacesWithinBrackets);
				WriteCommaSeparatedList (list.SafeCast<Expression, AstNode> ());
				Space (policy.SpacesWithinBrackets);
			}
			WriteToken ("]", AstNode.Roles.RBracket);
		}
		#endregion
		
		#region Write tokens
		/// <summary>
		/// Writes a keyword, and all specials up to
		/// </summary>
		void WriteKeyword (string keyword, Role<CSharpTokenNode> tokenRole = null)
		{
			WriteSpecialsUpToRole (tokenRole ?? AstNode.Roles.Keyword);
			if (lastWritten == LastWritten.KeywordOrIdentifier)
				formatter.Space ();
			formatter.WriteKeyword (keyword);
			lastWritten = LastWritten.KeywordOrIdentifier;
		}
		
		void WriteIdentifier (string identifier, Role<Identifier> identifierRole = null)
		{
			WriteSpecialsUpToRole (identifierRole ?? AstNode.Roles.Identifier);
			if (IsKeyword (identifier, containerStack.Peek ())) {
				if (lastWritten == LastWritten.KeywordOrIdentifier)
					Space (); // this space is not strictly required, so we call Space()
				formatter.WriteToken ("@");
			} else if (lastWritten == LastWritten.KeywordOrIdentifier) {
				formatter.Space (); // this space is strictly required, so we directly call the formatter
			}
			formatter.WriteIdentifier (identifier);
			lastWritten = LastWritten.KeywordOrIdentifier;
		}
		
		void WriteToken (string token, Role<CSharpTokenNode> tokenRole)
		{
			WriteSpecialsUpToRole (tokenRole);
			// Avoid that two +, - or ? tokens are combined into a ++, -- or ?? token.
			// Note that we don't need to handle tokens like = because there's no valid
			// C# program that contains the single token twice in a row.
			// (for +, - and &, this can happen with unary operators;
			// for ?, this can happen in "a is int? ? b : c" or "a as int? ?? 0";
			// and for /, this can happen with "1/ *ptr" or "1/ //comment".)
			if (lastWritten == LastWritten.Plus && token [0] == '+'
			    || lastWritten == LastWritten.Minus && token [0] == '-'
			    || lastWritten == LastWritten.Ampersand && token [0] == '&'
			    || lastWritten == LastWritten.QuestionMark && token [0] == '?'
			    || lastWritten == LastWritten.Division && token [0] == '*') {
				formatter.Space ();
			}
			formatter.WriteToken (token);
			if (token == "+")
				lastWritten = LastWritten.Plus;
			else if (token == "-")
				lastWritten = LastWritten.Minus;
			else if (token == "&")
				lastWritten = LastWritten.Ampersand;
			else if (token == "?")
				lastWritten = LastWritten.QuestionMark;
			else if (token == "/")
				lastWritten = LastWritten.Division;
			else
				lastWritten = LastWritten.Other;
		}
		
		void LPar ()
		{
			WriteToken ("(", AstNode.Roles.LPar);
		}
		
		void RPar ()
		{
			WriteToken (")", AstNode.Roles.LPar);
		}
		
		/// <summary>
		/// Marks the end of a statement
		/// </summary>
		void Semicolon ()
		{
			Role role = containerStack.Peek ().Role; // get the role of the current node
			if (!(role == ForStatement.InitializerRole || role == ForStatement.IteratorRole || role == UsingStatement.ResourceAcquisitionRole)) {
				WriteToken (";", AstNode.Roles.Semicolon);
				NewLine ();
			}
		}
		
		/// <summary>
		/// Writes a space depending on policy.
		/// </summary>
		void Space (bool addSpace = true)
		{
			if (addSpace) {
				formatter.Space ();
				lastWritten = LastWritten.Whitespace;
			}
		}
		
		void NewLine ()
		{
			formatter.NewLine ();
			lastWritten = LastWritten.Whitespace;
		}
		
		void OpenBrace (BraceStyle style)
		{
			WriteSpecialsUpToRole (AstNode.Roles.LBrace);
			formatter.OpenBrace (style);
			lastWritten = LastWritten.Other;
		}
		
		void CloseBrace (BraceStyle style)
		{
			WriteSpecialsUpToRole (AstNode.Roles.RBrace);
			formatter.CloseBrace (style);
			lastWritten = LastWritten.Other;
		}

		#endregion
		
		#region IsKeyword Test
		static readonly HashSet<string> unconditionalKeywords = new HashSet<string> {
			"abstract", "as", "base", "bool", "break", "byte", "case", "catch",
			"char", "checked", "class", "const", "continue", "decimal", "default", "delegate",
			"do", "double", "else", "enum", "event", "explicit", "extern", "false",
			"finally", "fixed", "float", "for", "foreach", "goto", "if", "implicit",
			"in", "int", "interface", "internal", "is", "lock", "long", "namespace",
			"new", "null", "object", "operator", "out", "override", "params", "private",
			"protected", "public", "readonly", "ref", "return", "sbyte", "sealed", "short",
			"sizeof", "stackalloc", "static", "string", "struct", "switch", "this", "throw",
			"true", "try", "typeof", "uint", "ulong", "unchecked", "unsafe", "ushort",
			"using", "virtual", "void", "volatile", "while"
		};
		static readonly HashSet<string> queryKeywords = new HashSet<string> {
			"from", "where", "join", "on", "equals", "into", "let", "orderby",
			"ascending", "descending", "select", "group", "by"
		};
		
		/// <summary>
		/// Determines whether the specified identifier is a keyword in the given context.
		/// </summary>
		public static bool IsKeyword (string identifier, AstNode context)
		{
			if (unconditionalKeywords.Contains (identifier))
				return true;
			if (context.Ancestors.Any (a => a is QueryExpression)) {
				if (queryKeywords.Contains (identifier))
					return true;
			}
			return false;
		}

		#endregion
		
		#region Write constructs
		void WriteTypeArguments (IEnumerable<AstType> typeArguments)
		{
			if (typeArguments.Any ()) {
				WriteToken ("<", AstNode.Roles.LChevron);
				WriteCommaSeparatedList (typeArguments);
				WriteToken (">", AstNode.Roles.RChevron);
			}
		}
		
		void WriteTypeParameters (IEnumerable<TypeParameterDeclaration> typeParameters)
		{
			if (typeParameters.Any ()) {
				WriteToken ("<", AstNode.Roles.LChevron);
				WriteCommaSeparatedList (typeParameters.SafeCast<TypeParameterDeclaration, AstNode> ());
				WriteToken (">", AstNode.Roles.RChevron);
			}
		}
		
		void WriteModifiers (IEnumerable<CSharpModifierToken> modifierTokens)
		{
			foreach (CSharpModifierToken modifier in modifierTokens) {
				modifier.AcceptVisitor (this, null);
			}
		}
		
		void WriteQualifiedIdentifier (IEnumerable<Identifier> identifiers)
		{
			bool first = true;
			foreach (Identifier ident in identifiers) {
				if (first) {
					first = false;
					if (lastWritten == LastWritten.KeywordOrIdentifier)
						formatter.Space ();
				} else {
					WriteSpecialsUpToRole (AstNode.Roles.Dot, ident);
					formatter.WriteToken (".");
					lastWritten = LastWritten.Other;
				}
				WriteSpecialsUpToNode (ident);
				formatter.WriteIdentifier (ident.Name);
				lastWritten = LastWritten.KeywordOrIdentifier;
			}
		}
		
		void WriteEmbeddedStatement (Statement embeddedStatement)
		{
			if (embeddedStatement.IsNull)
				return;
			BlockStatement block = embeddedStatement as BlockStatement;
			if (block != null)
				VisitBlockStatement (block, null);
			else {
				NewLine ();
				formatter.Indent ();
				embeddedStatement.AcceptVisitor (this, null);
				formatter.Unindent ();
			}
		}
		
		void WriteMethodBody (BlockStatement body)
		{
			if (body.IsNull)
				Semicolon ();
			else
				VisitBlockStatement (body, null);
		}
		
		void WriteAttributes (IEnumerable<AttributeSection> attributes)
		{
			foreach (AttributeSection attr in attributes) {
				attr.AcceptVisitor (this, null);
			}
		}
		
		void WritePrivateImplementationType (AstType privateImplementationType)
		{
			if (!privateImplementationType.IsNull) {
				privateImplementationType.AcceptVisitor (this, null);
				WriteToken (".", AstNode.Roles.Dot);
			}
		}

		#endregion
		
		#region Expressions
		public object VisitAnonymousMethodExpression (AnonymousMethodExpression anonymousMethodExpression, object data)
		{
			StartNode (anonymousMethodExpression);
			WriteKeyword ("delegate");
			if (anonymousMethodExpression.HasParameterList) {
				Space (policy.SpaceBeforeMethodDeclarationParentheses);
				WriteCommaSeparatedListInParenthesis (anonymousMethodExpression.Parameters, policy.SpaceWithinMethodDeclarationParentheses);
			}
			anonymousMethodExpression.Body.AcceptVisitor (this, data);
			return EndNode (anonymousMethodExpression);
		}
		
		public object VisitUndocumentedExpression (UndocumentedExpression undocumentedExpression, object data)
		{
			StartNode (undocumentedExpression);
			switch (undocumentedExpression.UndocumentedExpressionType) {
			case UndocumentedExpressionType.ArgList:
			case UndocumentedExpressionType.ArgListAccess:
				WriteKeyword ("__arglist");
				break;
			case UndocumentedExpressionType.MakeRef:
				WriteKeyword ("__makeref");
				break;
			case UndocumentedExpressionType.RefType:
				WriteKeyword ("__reftype");
				break;
			case UndocumentedExpressionType.RefValue:
				WriteKeyword ("__refvalue");
				break;
			}
			if (undocumentedExpression.Arguments.Count > 0) {
				Space (policy.SpaceBeforeMethodCallParentheses);
				WriteCommaSeparatedListInParenthesis (undocumentedExpression.Arguments, policy.SpaceWithinMethodCallParentheses);
			}
			return EndNode (undocumentedExpression);
		}
		
		public object VisitArrayCreateExpression (ArrayCreateExpression arrayCreateExpression, object data)
		{
			StartNode (arrayCreateExpression);
			WriteKeyword ("new");
			arrayCreateExpression.Type.AcceptVisitor (this, data);
			WriteCommaSeparatedListInBrackets (arrayCreateExpression.Arguments);
			foreach (var specifier in arrayCreateExpression.AdditionalArraySpecifiers)
				specifier.AcceptVisitor (this, data);
			arrayCreateExpression.Initializer.AcceptVisitor (this, data);
			return EndNode (arrayCreateExpression);
		}
		
		public object VisitArrayInitializerExpression (ArrayInitializerExpression arrayInitializerExpression, object data)
		{
			StartNode (arrayInitializerExpression);
			BraceStyle style;
			if (policy.PlaceArrayInitializersOnNewLine == ArrayInitializerPlacement.AlwaysNewLine)
				style = BraceStyle.NextLine;
			else
				style = BraceStyle.EndOfLine;
			OpenBrace (style);
			bool isFirst = true;
			foreach (AstNode node in arrayInitializerExpression.Elements) {
				if (isFirst) {
					isFirst = false;
				} else {
					Comma (node);
					NewLine ();
				}
				node.AcceptVisitor (this, null);
			}
			NewLine ();
			CloseBrace (style);
			return EndNode (arrayInitializerExpression);
		}
		
		public object VisitAsExpression (AsExpression asExpression, object data)
		{
			StartNode (asExpression);
			asExpression.Expression.AcceptVisitor (this, data);
			Space ();
			WriteKeyword ("as");
			Space ();
			asExpression.Type.AcceptVisitor (this, data);
			return EndNode (asExpression);
		}
		
		public object VisitAssignmentExpression (AssignmentExpression assignmentExpression, object data)
		{
			StartNode (assignmentExpression);
			assignmentExpression.Left.AcceptVisitor (this, data);
			Space (policy.SpaceAroundAssignment);
			WriteToken (AssignmentExpression.GetOperatorSymbol (assignmentExpression.Operator), AssignmentExpression.OperatorRole);
			Space (policy.SpaceAroundAssignment);
			assignmentExpression.Right.AcceptVisitor (this, data);
			return EndNode (assignmentExpression);
		}
		
		public object VisitBaseReferenceExpression (BaseReferenceExpression baseReferenceExpression, object data)
		{
			StartNode (baseReferenceExpression);
			WriteKeyword ("base");
			return EndNode (baseReferenceExpression);
		}
		
		public object VisitBinaryOperatorExpression (BinaryOperatorExpression binaryOperatorExpression, object data)
		{
			StartNode (binaryOperatorExpression);
			binaryOperatorExpression.Left.AcceptVisitor (this, data);
			bool spacePolicy;
			switch (binaryOperatorExpression.Operator) {
			case BinaryOperatorType.BitwiseAnd:
			case BinaryOperatorType.BitwiseOr:
			case BinaryOperatorType.ExclusiveOr:
				spacePolicy = policy.SpaceAroundBitwiseOperator;
				break;
			case BinaryOperatorType.ConditionalAnd:
			case BinaryOperatorType.ConditionalOr:
				spacePolicy = policy.SpaceAroundLogicalOperator;
				break;
			case BinaryOperatorType.GreaterThan:
			case BinaryOperatorType.GreaterThanOrEqual:
			case BinaryOperatorType.LessThanOrEqual:
			case BinaryOperatorType.LessThan:
				spacePolicy = policy.SpaceAroundRelationalOperator;
				break;
			case BinaryOperatorType.Equality:
			case BinaryOperatorType.InEquality:
				spacePolicy = policy.SpaceAroundEqualityOperator;
				break;
			case BinaryOperatorType.Add:
			case BinaryOperatorType.Subtract:
				spacePolicy = policy.SpaceAroundAdditiveOperator;
				break;
			case BinaryOperatorType.Multiply:
			case BinaryOperatorType.Divide:
			case BinaryOperatorType.Modulus:
				spacePolicy = policy.SpaceAroundMultiplicativeOperator;
				break;
			case BinaryOperatorType.ShiftLeft:
			case BinaryOperatorType.ShiftRight:
				spacePolicy = policy.SpaceAroundShiftOperator;
				break;
			case BinaryOperatorType.NullCoalescing:
				spacePolicy = true;
				break;
			default:
				throw new NotSupportedException ("Invalid value for BinaryOperatorType");
			}
			Space (spacePolicy);
			WriteToken (BinaryOperatorExpression.GetOperatorSymbol (binaryOperatorExpression.Operator), BinaryOperatorExpression.OperatorRole);
			Space (spacePolicy);
			binaryOperatorExpression.Right.AcceptVisitor (this, data);
			return EndNode (binaryOperatorExpression);
		}
		
		public object VisitCastExpression (CastExpression castExpression, object data)
		{
			StartNode (castExpression);
			LPar ();
			Space (policy.SpacesWithinCastParentheses);
			castExpression.Type.AcceptVisitor (this, data);
			Space (policy.SpacesWithinCastParentheses);
			RPar ();
			Space (policy.SpaceAfterTypecast);
			castExpression.Expression.AcceptVisitor (this, data);
			return EndNode (castExpression);
		}
		
		public object VisitCheckedExpression (CheckedExpression checkedExpression, object data)
		{
			StartNode (checkedExpression);
			WriteKeyword ("checked");
			LPar ();
			Space (policy.SpacesWithinCheckedExpressionParantheses);
			checkedExpression.Expression.AcceptVisitor (this, data);
			Space (policy.SpacesWithinCheckedExpressionParantheses);
			RPar ();
			return EndNode (checkedExpression);
		}
		
		public object VisitConditionalExpression (ConditionalExpression conditionalExpression, object data)
		{
			StartNode (conditionalExpression);
			conditionalExpression.Condition.AcceptVisitor (this, data);
			
			Space (policy.SpaceBeforeConditionalOperatorCondition);
			WriteToken ("?", ConditionalExpression.QuestionMarkRole);
			Space (policy.SpaceAfterConditionalOperatorCondition);
			
			conditionalExpression.TrueExpression.AcceptVisitor (this, data);
			
			Space (policy.SpaceBeforeConditionalOperatorSeparator);
			WriteToken (":", ConditionalExpression.ColonRole);
			Space (policy.SpaceAfterConditionalOperatorSeparator);
			
			conditionalExpression.FalseExpression.AcceptVisitor (this, data);
			
			return EndNode (conditionalExpression);
		}
		
		public object VisitDefaultValueExpression (DefaultValueExpression defaultValueExpression, object data)
		{
			StartNode (defaultValueExpression);
			
			WriteKeyword ("default");
			LPar ();
			Space (policy.SpacesWithinTypeOfParentheses);
			defaultValueExpression.Type.AcceptVisitor (this, data);
			Space (policy.SpacesWithinTypeOfParentheses);
			RPar ();
			
			return EndNode (defaultValueExpression);
		}
		
		public object VisitDirectionExpression (DirectionExpression directionExpression, object data)
		{
			StartNode (directionExpression);
			
			switch (directionExpression.FieldDirection) {
			case FieldDirection.Out:
				WriteKeyword ("out");
				break;
			case FieldDirection.Ref:
				WriteKeyword ("ref");
				break;
			default:
				throw new NotSupportedException ("Invalid value for FieldDirection");
			}
			Space ();
			directionExpression.Expression.AcceptVisitor (this, data);
			
			return EndNode (directionExpression);
		}
		
		public object VisitIdentifierExpression (IdentifierExpression identifierExpression, object data)
		{
			StartNode (identifierExpression);
			WriteIdentifier (identifierExpression.Identifier);
			WriteTypeArguments (identifierExpression.TypeArguments);
			return EndNode (identifierExpression);
		}
		
		public object VisitIndexerExpression (IndexerExpression indexerExpression, object data)
		{
			StartNode (indexerExpression);
			indexerExpression.Target.AcceptVisitor (this, data);
			Space (policy.SpaceBeforeMethodCallParentheses);
			WriteCommaSeparatedListInBrackets (indexerExpression.Arguments);
			return EndNode (indexerExpression);
		}
		
		public object VisitInvocationExpression (InvocationExpression invocationExpression, object data)
		{
			StartNode (invocationExpression);
			invocationExpression.Target.AcceptVisitor (this, data);
			Space (policy.SpaceBeforeMethodCallParentheses);
			WriteCommaSeparatedListInParenthesis (invocationExpression.Arguments, policy.SpaceWithinMethodCallParentheses);
			return EndNode (invocationExpression);
		}
		
		public object VisitIsExpression (IsExpression isExpression, object data)
		{
			StartNode (isExpression);
			isExpression.Expression.AcceptVisitor (this, data);
			Space ();
			WriteKeyword ("is");
			isExpression.Type.AcceptVisitor (this, data);
			return EndNode (isExpression);
		}
		
		public object VisitLambdaExpression (LambdaExpression lambdaExpression, object data)
		{
			StartNode (lambdaExpression);
			if (LambdaNeedsParenthesis (lambdaExpression)) {
				WriteCommaSeparatedListInParenthesis (lambdaExpression.Parameters, policy.SpaceWithinMethodDeclarationParentheses);
			} else {
				lambdaExpression.Parameters.Single ().AcceptVisitor (this, data);
			}
			Space ();
			WriteToken ("=>", LambdaExpression.ArrowRole);
			Space ();
			lambdaExpression.Body.AcceptVisitor (this, data);
			return EndNode (lambdaExpression);
		}
		
		bool LambdaNeedsParenthesis (LambdaExpression lambdaExpression)
		{
			if (lambdaExpression.Parameters.Count != 1)
				return true;
			var p = lambdaExpression.Parameters.Single ();
			return !(p.Type.IsNull && p.ParameterModifier == ParameterModifier.None);
		}
		
		public object VisitMemberReferenceExpression (MemberReferenceExpression memberReferenceExpression, object data)
		{
			StartNode (memberReferenceExpression);
			memberReferenceExpression.Target.AcceptVisitor (this, data);
			WriteToken (".", MemberReferenceExpression.Roles.Dot);
			WriteIdentifier (memberReferenceExpression.MemberName);
			WriteTypeArguments (memberReferenceExpression.TypeArguments);
			return EndNode (memberReferenceExpression);
		}
		
		public object VisitNamedArgumentExpression (NamedArgumentExpression namedArgumentExpression, object data)
		{
			StartNode (namedArgumentExpression);
			WriteIdentifier (namedArgumentExpression.Identifier);
			if (namedArgumentExpression.Parent is ArrayInitializerExpression) {
				Space();
				WriteToken("=", NamedArgumentExpression.Roles.Assign);
			} else {
				WriteToken(":", NamedArgumentExpression.Roles.Colon);
			}
			Space ();
			namedArgumentExpression.Expression.AcceptVisitor (this, data);
			return EndNode (namedArgumentExpression);
		}
		
		public object VisitNullReferenceExpression (NullReferenceExpression nullReferenceExpression, object data)
		{
			StartNode (nullReferenceExpression);
			WriteKeyword ("null");
			return EndNode (nullReferenceExpression);
		}
		
		public object VisitObjectCreateExpression (ObjectCreateExpression objectCreateExpression, object data)
		{
			StartNode (objectCreateExpression);
			WriteKeyword ("new");
			objectCreateExpression.Type.AcceptVisitor (this, data);
			bool useParenthesis = objectCreateExpression.Arguments.Any() || objectCreateExpression.Initializer.IsNull;
			// also use parenthesis if there is an '(' token and this isn't an anonymous type
			if (!objectCreateExpression.LParToken.IsNull && !objectCreateExpression.Type.IsNull)
				useParenthesis = true;
			if (useParenthesis) {
				Space (policy.SpaceBeforeMethodCallParentheses);
				WriteCommaSeparatedListInParenthesis (objectCreateExpression.Arguments, policy.SpaceWithinMethodCallParentheses);
			}
			objectCreateExpression.Initializer.AcceptVisitor (this, data);
			return EndNode (objectCreateExpression);
		}
		
		public object VisitAnonymousTypeCreateExpression (AnonymousTypeCreateExpression anonymousTypeCreateExpression, object data)
		{
			StartNode (anonymousTypeCreateExpression);
			WriteKeyword ("new");
			Space ();
			LPar ();
			RPar ();
			Space ();
			OpenBrace (policy.AnonymousMethodBraceStyle);
			foreach (AstNode node in anonymousTypeCreateExpression.Initializer) {
				node.AcceptVisitor (this, null);
				if (node.NextSibling != null)
					Comma (node);
				NewLine ();
			}
			CloseBrace (policy.AnonymousMethodBraceStyle);
			return EndNode (anonymousTypeCreateExpression);
		}

		public object VisitParenthesizedExpression (ParenthesizedExpression parenthesizedExpression, object data)
		{
			StartNode (parenthesizedExpression);
			LPar ();
			Space (policy.SpacesWithinParentheses);
			parenthesizedExpression.Expression.AcceptVisitor (this, data);
			Space (policy.SpacesWithinParentheses);
			RPar ();
			return EndNode (parenthesizedExpression);
		}
		
		public object VisitPointerReferenceExpression (PointerReferenceExpression pointerReferenceExpression, object data)
		{
			StartNode (pointerReferenceExpression);
			pointerReferenceExpression.Target.AcceptVisitor (this, data);
			WriteToken ("->", PointerReferenceExpression.ArrowRole);
			WriteIdentifier (pointerReferenceExpression.MemberName);
			WriteTypeArguments (pointerReferenceExpression.TypeArguments);
			return EndNode (pointerReferenceExpression);
		}
		
		public object VisitEmptyExpression (EmptyExpression emptyExpression, object data)
		{
			StartNode (emptyExpression);
			return EndNode (emptyExpression);
		}

		#region VisitPrimitiveExpression
		public object VisitPrimitiveExpression (PrimitiveExpression primitiveExpression, object data)
		{
			StartNode (primitiveExpression);
			if (!string.IsNullOrEmpty (primitiveExpression.LiteralValue)) {
				formatter.WriteToken (primitiveExpression.LiteralValue);
			} else {
				WritePrimitiveValue (primitiveExpression.Value);
			}
			return EndNode (primitiveExpression);
		}
		
		void WritePrimitiveValue (object val)
		{
			if (val == null) {
				// usually NullReferenceExpression should be used for this, but we'll handle it anyways
				WriteKeyword ("null");
				return;
			}
			
			if (val is bool) {
				if ((bool)val) {
					WriteKeyword ("true");
				} else {
					WriteKeyword ("false");
				}
				return;
			}
			
			if (val is string) {
				formatter.WriteToken ("\"" + ConvertString (val.ToString ()) + "\"");
				lastWritten = LastWritten.Other;
			} else if (val is char) {
				formatter.WriteToken ("'" + ConvertCharLiteral ((char)val) + "'");
				lastWritten = LastWritten.Other;
			} else if (val is decimal) {
				formatter.WriteToken (((decimal)val).ToString (NumberFormatInfo.InvariantInfo) + "m");
				lastWritten = LastWritten.Other;
			} else if (val is float) {
				float f = (float)val;
				if (float.IsInfinity (f) || float.IsNaN (f)) {
					// Strictly speaking, these aren't PrimitiveExpressions;
					// but we still support writing these to make life easier for code generators.
					WriteKeyword ("float");
					WriteToken (".", AstNode.Roles.Dot);
					if (float.IsPositiveInfinity (f))
						WriteIdentifier ("PositiveInfinity");
					else if (float.IsNegativeInfinity (f))
						WriteIdentifier ("NegativeInfinity");
					else
						WriteIdentifier ("NaN");
					return;
				}
				formatter.WriteToken (f.ToString ("R", NumberFormatInfo.InvariantInfo) + "f");
				lastWritten = LastWritten.Other;
			} else if (val is double) {
				double f = (double)val;
				if (double.IsInfinity (f) || double.IsNaN (f)) {
					// Strictly speaking, these aren't PrimitiveExpressions;
					// but we still support writing these to make life easier for code generators.
					WriteKeyword ("double");
					WriteToken (".", AstNode.Roles.Dot);
					if (double.IsPositiveInfinity (f))
						WriteIdentifier ("PositiveInfinity");
					else if (double.IsNegativeInfinity (f))
						WriteIdentifier ("NegativeInfinity");
					else
						WriteIdentifier ("NaN");
					return;
				}
				string number = f.ToString ("R", NumberFormatInfo.InvariantInfo);
				if (number.IndexOf ('.') < 0 && number.IndexOf ('E') < 0)
					number += ".0";
				formatter.WriteToken (number);
				// needs space if identifier follows number; this avoids mistaking the following identifier as type suffix
				lastWritten = LastWritten.KeywordOrIdentifier;
			} else if (val is IFormattable) {
				StringBuilder b = new StringBuilder ();
//				if (primitiveExpression.LiteralFormat == LiteralFormat.HexadecimalNumber) {
//					b.Append("0x");
//					b.Append(((IFormattable)val).ToString("x", NumberFormatInfo.InvariantInfo));
//				} else {
				b.Append (((IFormattable)val).ToString (null, NumberFormatInfo.InvariantInfo));
//				}
				if (val is uint || val is ulong) {
					b.Append ("u");
				}
				if (val is long || val is ulong) {
					b.Append ("L");
				}
				formatter.WriteToken (b.ToString ());
				// needs space if identifier follows number; this avoids mistaking the following identifier as type suffix
				lastWritten = LastWritten.KeywordOrIdentifier;
			} else {
				formatter.WriteToken (val.ToString ());
				lastWritten = LastWritten.Other;
			}
		}
		
		static string ConvertCharLiteral (char ch)
		{
			if (ch == '\'')
				return "\\'";
			return ConvertChar (ch);
		}
		
		/// <summary>
		/// Gets the escape sequence for the specified character.
		/// </summary>
		/// <remarks>This method does not convert ' or ".</remarks>
		public static string ConvertChar(char ch)
		{
			switch (ch) {
			case '\\':
				return "\\\\";
			case '\0':
				return "\\0";
			case '\a':
				return "\\a";
			case '\b':
				return "\\b";
			case '\f':
				return "\\f";
			case '\n':
				return "\\n";
			case '\r':
				return "\\r";
			case '\t':
				return "\\t";
			case '\v':
				return "\\v";
			default:
					if (char.IsControl(ch) || char.IsSurrogate(ch) ||
					    // print all uncommon white spaces as numbers
					    (char.IsWhiteSpace(ch) && ch != ' ')) {
					return "\\u" + ((int)ch).ToString ("x4");
				} else {
					return ch.ToString ();
				}
			}
		}
		
		/// <summary>
		/// Converts special characters to escape sequences within the given string.
		/// </summary>
		public static string ConvertString(string str)
		{
			StringBuilder sb = new StringBuilder ();
			foreach (char ch in str) {
				if (ch == '"')
					sb.Append ("\\\"");
				else
					sb.Append (ConvertChar (ch));
			}
			return sb.ToString ();
		}

		#endregion
		
		public object VisitSizeOfExpression (SizeOfExpression sizeOfExpression, object data)
		{
			StartNode (sizeOfExpression);
			
			WriteKeyword ("sizeof");
			LPar ();
			Space (policy.SpacesWithinSizeOfParentheses);
			sizeOfExpression.Type.AcceptVisitor (this, data);
			Space (policy.SpacesWithinSizeOfParentheses);
			RPar ();
			
			return EndNode (sizeOfExpression);
		}
		
		public object VisitStackAllocExpression (StackAllocExpression stackAllocExpression, object data)
		{
			StartNode (stackAllocExpression);
			WriteKeyword ("stackalloc");
			stackAllocExpression.Type.AcceptVisitor (this, data);
			WriteCommaSeparatedListInBrackets (new[] { stackAllocExpression.CountExpression });
			return EndNode (stackAllocExpression);
		}
		
		public object VisitThisReferenceExpression (ThisReferenceExpression thisReferenceExpression, object data)
		{
			StartNode (thisReferenceExpression);
			WriteKeyword ("this");
			return EndNode (thisReferenceExpression);
		}
		
		public object VisitTypeOfExpression (TypeOfExpression typeOfExpression, object data)
		{
			StartNode (typeOfExpression);
			
			WriteKeyword ("typeof");
			LPar ();
			Space (policy.SpacesWithinTypeOfParentheses);
			typeOfExpression.Type.AcceptVisitor (this, data);
			Space (policy.SpacesWithinTypeOfParentheses);
			RPar ();
			
			return EndNode (typeOfExpression);
		}
		
		public object VisitTypeReferenceExpression (TypeReferenceExpression typeReferenceExpression, object data)
		{
			StartNode (typeReferenceExpression);
			typeReferenceExpression.Type.AcceptVisitor (this, data);
			return EndNode (typeReferenceExpression);
		}
		
		public object VisitUnaryOperatorExpression (UnaryOperatorExpression unaryOperatorExpression, object data)
		{
			StartNode (unaryOperatorExpression);
			UnaryOperatorType opType = unaryOperatorExpression.Operator;
			string opSymbol = UnaryOperatorExpression.GetOperatorSymbol (opType);
			if (!(opType == UnaryOperatorType.PostIncrement || opType == UnaryOperatorType.PostDecrement))
				WriteToken (opSymbol, UnaryOperatorExpression.OperatorRole);
			unaryOperatorExpression.Expression.AcceptVisitor (this, data);
			if (opType == UnaryOperatorType.PostIncrement || opType == UnaryOperatorType.PostDecrement)
				WriteToken (opSymbol, UnaryOperatorExpression.OperatorRole);
			return EndNode (unaryOperatorExpression);
		}
		
		public object VisitUncheckedExpression (UncheckedExpression uncheckedExpression, object data)
		{
			StartNode (uncheckedExpression);
			WriteKeyword ("unchecked");
			LPar ();
			Space (policy.SpacesWithinCheckedExpressionParantheses);
			uncheckedExpression.Expression.AcceptVisitor (this, data);
			Space (policy.SpacesWithinCheckedExpressionParantheses);
			RPar ();
			return EndNode (uncheckedExpression);
		}

		#endregion
		
		#region Query Expressions
		public object VisitQueryExpression (QueryExpression queryExpression, object data)
		{
			StartNode (queryExpression);
			bool indent = !(queryExpression.Parent is QueryContinuationClause);
			if (indent) {
				formatter.Indent();
				NewLine();
			}
			bool first = true;
			foreach (var clause in queryExpression.Clauses) {
				if (first) {
					first = false;
				} else {
					if (!(clause is QueryContinuationClause))
						NewLine ();
				}
				clause.AcceptVisitor (this, data);
			}
			if (indent)
				formatter.Unindent();
			return EndNode (queryExpression);
		}
		
		public object VisitQueryContinuationClause (QueryContinuationClause queryContinuationClause, object data)
		{
			StartNode (queryContinuationClause);
			queryContinuationClause.PrecedingQuery.AcceptVisitor (this, data);
			Space ();
			WriteKeyword ("into", QueryContinuationClause.IntoKeywordRole);
			Space ();
			WriteIdentifier (queryContinuationClause.Identifier);
			return EndNode (queryContinuationClause);
		}
		
		public object VisitQueryFromClause (QueryFromClause queryFromClause, object data)
		{
			StartNode (queryFromClause);
			WriteKeyword ("from", QueryFromClause.FromKeywordRole);
			queryFromClause.Type.AcceptVisitor (this, data);
			Space ();
			WriteIdentifier (queryFromClause.Identifier);
			Space ();
			WriteKeyword ("in", QueryFromClause.InKeywordRole);
			Space ();
			queryFromClause.Expression.AcceptVisitor (this, data);
			return EndNode (queryFromClause);
		}
		
		public object VisitQueryLetClause (QueryLetClause queryLetClause, object data)
		{
			StartNode (queryLetClause);
			WriteKeyword ("let");
			Space ();
			WriteIdentifier (queryLetClause.Identifier);
			Space (policy.SpaceAroundAssignment);
			WriteToken ("=", QueryLetClause.Roles.Assign);
			Space (policy.SpaceAroundAssignment);
			queryLetClause.Expression.AcceptVisitor (this, data);
			return EndNode (queryLetClause);
		}
		
		public object VisitQueryWhereClause (QueryWhereClause queryWhereClause, object data)
		{
			StartNode (queryWhereClause);
			WriteKeyword ("where");
			Space ();
			queryWhereClause.Condition.AcceptVisitor (this, data);
			return EndNode (queryWhereClause);
		}
		
		public object VisitQueryJoinClause (QueryJoinClause queryJoinClause, object data)
		{
			StartNode (queryJoinClause);
			WriteKeyword ("join", QueryJoinClause.JoinKeywordRole);
			queryJoinClause.Type.AcceptVisitor (this, data);
			Space ();
			WriteIdentifier (queryJoinClause.JoinIdentifier, QueryJoinClause.JoinIdentifierRole);
			Space ();
			WriteKeyword ("in", QueryJoinClause.InKeywordRole);
			Space ();
			queryJoinClause.InExpression.AcceptVisitor (this, data);
			Space ();
			WriteKeyword ("on", QueryJoinClause.OnKeywordRole);
			Space ();
			queryJoinClause.OnExpression.AcceptVisitor (this, data);
			Space ();
			WriteKeyword ("equals", QueryJoinClause.EqualsKeywordRole);
			Space ();
			queryJoinClause.EqualsExpression.AcceptVisitor (this, data);
			if (queryJoinClause.IsGroupJoin) {
				Space ();
				WriteKeyword ("into", QueryJoinClause.IntoKeywordRole);
				WriteIdentifier (queryJoinClause.IntoIdentifier, QueryJoinClause.IntoIdentifierRole);
			}
			return EndNode (queryJoinClause);
		}
		
		public object VisitQueryOrderClause (QueryOrderClause queryOrderClause, object data)
		{
			StartNode (queryOrderClause);
			WriteKeyword ("orderby");
			Space ();
			WriteCommaSeparatedList (queryOrderClause.Orderings.SafeCast<QueryOrdering, AstNode> ());
			return EndNode (queryOrderClause);
		}
		
		public object VisitQueryOrdering (QueryOrdering queryOrdering, object data)
		{
			StartNode (queryOrdering);
			queryOrdering.Expression.AcceptVisitor (this, data);
			switch (queryOrdering.Direction) {
			case QueryOrderingDirection.Ascending:
				Space ();
				WriteKeyword ("ascending");
				break;
			case QueryOrderingDirection.Descending:
				Space ();
				WriteKeyword ("descending");
				break;
			}
			return EndNode (queryOrdering);
		}
		
		public object VisitQuerySelectClause (QuerySelectClause querySelectClause, object data)
		{
			StartNode (querySelectClause);
			WriteKeyword ("select");
			Space ();
			querySelectClause.Expression.AcceptVisitor (this, data);
			return EndNode (querySelectClause);
		}
		
		public object VisitQueryGroupClause (QueryGroupClause queryGroupClause, object data)
		{
			StartNode (queryGroupClause);
			WriteKeyword ("group", QueryGroupClause.GroupKeywordRole);
			Space ();
			queryGroupClause.Projection.AcceptVisitor (this, data);
			Space ();
			WriteKeyword ("by", QueryGroupClause.ByKeywordRole);
			Space ();
			queryGroupClause.Key.AcceptVisitor (this, data);
			return EndNode (queryGroupClause);
		}

		#endregion
		
		#region GeneralScope
		public object VisitAttribute (Attribute attribute, object data)
		{
			StartNode (attribute);
			attribute.Type.AcceptVisitor (this, data);
			Space (policy.SpaceBeforeMethodCallParentheses);
			if (attribute.Arguments.Count != 0 || !attribute.GetChildByRole (AstNode.Roles.LPar).IsNull)
				WriteCommaSeparatedListInParenthesis (attribute.Arguments, policy.SpaceWithinMethodCallParentheses);
			return EndNode (attribute);
		}
		
		public object VisitAttributeSection (AttributeSection attributeSection, object data)
		{
			StartNode (attributeSection);
			WriteToken ("[", AstNode.Roles.LBracket);
			if (!string.IsNullOrEmpty (attributeSection.AttributeTarget)) {
				WriteToken (attributeSection.AttributeTarget, AttributeSection.TargetRole);
				WriteToken (":", AttributeSection.Roles.Colon);
				Space ();
			}
			WriteCommaSeparatedList (attributeSection.Attributes.SafeCast<Attribute, AstNode> ());
			WriteToken ("]", AstNode.Roles.RBracket);
			if (attributeSection.Parent is ParameterDeclaration || attributeSection.Parent is TypeParameterDeclaration)
				Space ();
			else
				NewLine ();
			return EndNode (attributeSection);
		}
		
		public object VisitDelegateDeclaration (DelegateDeclaration delegateDeclaration, object data)
		{
			StartNode (delegateDeclaration);
			WriteAttributes (delegateDeclaration.Attributes);
			WriteModifiers (delegateDeclaration.ModifierTokens);
			WriteKeyword ("delegate");
			delegateDeclaration.ReturnType.AcceptVisitor (this, data);
			Space ();
			WriteIdentifier (delegateDeclaration.Name);
			WriteTypeParameters (delegateDeclaration.TypeParameters);
			Space (policy.SpaceBeforeDelegateDeclarationParentheses);
			WriteCommaSeparatedListInParenthesis (delegateDeclaration.Parameters, policy.SpaceWithinMethodDeclarationParentheses);
			foreach (Constraint constraint in delegateDeclaration.Constraints) {
				constraint.AcceptVisitor (this, data);
			}
			Semicolon ();
			return EndNode (delegateDeclaration);
		}
		
		public object VisitNamespaceDeclaration (NamespaceDeclaration namespaceDeclaration, object data)
		{
			StartNode (namespaceDeclaration);
			WriteKeyword ("namespace");
			WriteQualifiedIdentifier (namespaceDeclaration.Identifiers);
			OpenBrace (policy.NamespaceBraceStyle);
			foreach (var member in namespaceDeclaration.Members)
				member.AcceptVisitor (this, data);
			CloseBrace (policy.NamespaceBraceStyle);
			NewLine ();
			return EndNode (namespaceDeclaration);
		}
		
		public object VisitTypeDeclaration (TypeDeclaration typeDeclaration, object data)
		{
			StartNode (typeDeclaration);
			WriteAttributes (typeDeclaration.Attributes);
			WriteModifiers (typeDeclaration.ModifierTokens);
			BraceStyle braceStyle;
			switch (typeDeclaration.ClassType) {
			case ClassType.Enum:
				WriteKeyword ("enum");
				braceStyle = policy.EnumBraceStyle;
				break;
			case ClassType.Interface:
				WriteKeyword ("interface");
				braceStyle = policy.InterfaceBraceStyle;
				break;
			case ClassType.Struct:
				WriteKeyword ("struct");
				braceStyle = policy.StructBraceStyle;
				break;
			default:
				WriteKeyword ("class");
				braceStyle = policy.ClassBraceStyle;
				break;
			}
			WriteIdentifier (typeDeclaration.Name);
			WriteTypeParameters (typeDeclaration.TypeParameters);
			if (typeDeclaration.BaseTypes.Any ()) {
				Space ();
				WriteToken (":", TypeDeclaration.ColonRole);
				Space ();
				WriteCommaSeparatedList (typeDeclaration.BaseTypes);
			}
			foreach (Constraint constraint in typeDeclaration.Constraints) {
				constraint.AcceptVisitor (this, data);
			}
			OpenBrace (braceStyle);
			if (typeDeclaration.ClassType == ClassType.Enum) {
				bool first = true;
				foreach (var member in typeDeclaration.Members) {
					if (first) {
						first = false;
					} else {
						Comma (member, noSpaceAfterComma: true);
						NewLine ();
					}
					member.AcceptVisitor (this, data);
				}
				NewLine ();
			} else {
				foreach (var member in typeDeclaration.Members) {
					member.AcceptVisitor (this, data);
				}
			}
			CloseBrace (braceStyle);
			NewLine ();
			return EndNode (typeDeclaration);
		}
		
		public object VisitUsingAliasDeclaration (UsingAliasDeclaration usingAliasDeclaration, object data)
		{
			StartNode (usingAliasDeclaration);
			WriteKeyword ("using");
			WriteIdentifier (usingAliasDeclaration.Alias, UsingAliasDeclaration.AliasRole);
			Space (policy.SpaceAroundEqualityOperator);
			WriteToken ("=", AstNode.Roles.Assign);
			Space (policy.SpaceAroundEqualityOperator);
			usingAliasDeclaration.Import.AcceptVisitor (this, data);
			Semicolon ();
			return EndNode (usingAliasDeclaration);
		}
		
		public object VisitUsingDeclaration (UsingDeclaration usingDeclaration, object data)
		{
			StartNode (usingDeclaration);
			WriteKeyword ("using");
			usingDeclaration.Import.AcceptVisitor (this, data);
			Semicolon ();
			return EndNode (usingDeclaration);
		}
		
		public object VisitExternAliasDeclaration (ExternAliasDeclaration externAliasDeclaration, object data)
		{
			StartNode (externAliasDeclaration);
			WriteKeyword ("extern");
			Space ();
			WriteKeyword ("alias");
			Space ();
			externAliasDeclaration.NameToken.AcceptVisitor (this, data);
			Semicolon ();
			return EndNode (externAliasDeclaration);
		}

		#endregion
		
		#region Statements
		public object VisitBlockStatement (BlockStatement blockStatement, object data)
		{
			StartNode (blockStatement);
			BraceStyle style;
			if (blockStatement.Parent is AnonymousMethodExpression || blockStatement.Parent is LambdaExpression) {
				style = policy.AnonymousMethodBraceStyle;
			} else if (blockStatement.Parent is ConstructorDeclaration) {
				style = policy.ConstructorBraceStyle;
			} else if (blockStatement.Parent is DestructorDeclaration) {
				style = policy.DestructorBraceStyle;
			} else if (blockStatement.Parent is MethodDeclaration) {
				style = policy.MethodBraceStyle;
			} else if (blockStatement.Parent is Accessor) {
				if (blockStatement.Parent.Role == PropertyDeclaration.GetterRole)
					style = policy.PropertyGetBraceStyle;
				else if (blockStatement.Parent.Role == PropertyDeclaration.SetterRole)
					style = policy.PropertySetBraceStyle;
				else if (blockStatement.Parent.Role == CustomEventDeclaration.AddAccessorRole)
					style = policy.EventAddBraceStyle;
				else if (blockStatement.Parent.Role == CustomEventDeclaration.RemoveAccessorRole)
					style = policy.EventRemoveBraceStyle;
				else
					throw new NotSupportedException ("Unknown type of accessor");
			} else {
				style = policy.StatementBraceStyle;
			}
			OpenBrace (style);
			foreach (var node in blockStatement.Statements) {
				node.AcceptVisitor (this, data);
			}
			CloseBrace (style);
			NewLine ();
			return EndNode (blockStatement);
		}
		
		public object VisitBreakStatement (BreakStatement breakStatement, object data)
		{
			StartNode (breakStatement);
			WriteKeyword ("break");
			Semicolon ();
			return EndNode (breakStatement);
		}
		
		public object VisitCheckedStatement (CheckedStatement checkedStatement, object data)
		{
			StartNode (checkedStatement);
			WriteKeyword ("checked");
			checkedStatement.Body.AcceptVisitor (this, data);
			return EndNode (checkedStatement);
		}
		
		public object VisitContinueStatement (ContinueStatement continueStatement, object data)
		{
			StartNode (continueStatement);
			WriteKeyword ("continue");
			Semicolon ();
			return EndNode (continueStatement);
		}
		
		public object VisitDoWhileStatement (DoWhileStatement doWhileStatement, object data)
		{
			StartNode (doWhileStatement);
			WriteKeyword ("do", DoWhileStatement.DoKeywordRole);
			WriteEmbeddedStatement (doWhileStatement.EmbeddedStatement);
			WriteKeyword ("while", DoWhileStatement.WhileKeywordRole);
			Space (policy.SpaceBeforeWhileParentheses);
			LPar ();
			Space (policy.SpacesWithinWhileParentheses);
			doWhileStatement.Condition.AcceptVisitor (this, data);
			Space (policy.SpacesWithinWhileParentheses);
			RPar ();
			Semicolon ();
			return EndNode (doWhileStatement);
		}
		
		public object VisitEmptyStatement (EmptyStatement emptyStatement, object data)
		{
			StartNode (emptyStatement);
			Semicolon ();
			return EndNode (emptyStatement);
		}
		
		public object VisitExpressionStatement (ExpressionStatement expressionStatement, object data)
		{
			StartNode (expressionStatement);
			expressionStatement.Expression.AcceptVisitor (this, data);
			Semicolon ();
			return EndNode (expressionStatement);
		}
		
		public object VisitFixedStatement (FixedStatement fixedStatement, object data)
		{
			StartNode (fixedStatement);
			WriteKeyword ("fixed");
			Space (policy.SpaceBeforeUsingParentheses);
			LPar ();
			Space (policy.SpacesWithinUsingParentheses);
			fixedStatement.Type.AcceptVisitor (this, data);
			Space ();
			WriteCommaSeparatedList (fixedStatement.Variables);
			Space (policy.SpacesWithinUsingParentheses);
			RPar ();
			WriteEmbeddedStatement (fixedStatement.EmbeddedStatement);
			return EndNode (fixedStatement);
		}
		
		public object VisitForeachStatement (ForeachStatement foreachStatement, object data)
		{
			StartNode (foreachStatement);
			WriteKeyword ("foreach");
			Space (policy.SpaceBeforeForeachParentheses);
			LPar ();
			Space (policy.SpacesWithinForeachParentheses);
			foreachStatement.VariableType.AcceptVisitor (this, data);
			Space ();
			WriteIdentifier (foreachStatement.VariableName);
			WriteKeyword ("in", ForeachStatement.Roles.InKeyword);
			Space ();
			foreachStatement.InExpression.AcceptVisitor (this, data);
			Space (policy.SpacesWithinForeachParentheses);
			RPar ();
			WriteEmbeddedStatement (foreachStatement.EmbeddedStatement);
			return EndNode (foreachStatement);
		}
		
		public object VisitForStatement (ForStatement forStatement, object data)
		{
			StartNode (forStatement);
			WriteKeyword ("for");
			Space (policy.SpaceBeforeForParentheses);
			LPar ();
			Space (policy.SpacesWithinForParentheses);
			
			WriteCommaSeparatedList (forStatement.Initializers.SafeCast<Statement, AstNode> ());
			Space (policy.SpaceBeforeForSemicolon);
			WriteToken (";", AstNode.Roles.Semicolon);
			Space (policy.SpaceAfterForSemicolon);
			
			forStatement.Condition.AcceptVisitor (this, data);
			Space (policy.SpaceBeforeForSemicolon);
			WriteToken (";", AstNode.Roles.Semicolon);
			Space (policy.SpaceAfterForSemicolon);
			
			WriteCommaSeparatedList (forStatement.Iterators.SafeCast<Statement, AstNode> ());
			
			Space (policy.SpacesWithinForParentheses);
			RPar ();
			WriteEmbeddedStatement (forStatement.EmbeddedStatement);
			return EndNode (forStatement);
		}
		
		public object VisitGotoCaseStatement (GotoCaseStatement gotoCaseStatement, object data)
		{
			StartNode (gotoCaseStatement);
			WriteKeyword ("goto");
			WriteKeyword ("case", GotoCaseStatement.CaseKeywordRole);
			Space ();
			gotoCaseStatement.LabelExpression.AcceptVisitor (this, data);
			Semicolon ();
			return EndNode (gotoCaseStatement);
		}
		
		public object VisitGotoDefaultStatement (GotoDefaultStatement gotoDefaultStatement, object data)
		{
			StartNode (gotoDefaultStatement);
			WriteKeyword ("goto");
			WriteKeyword ("default", GotoDefaultStatement.DefaultKeywordRole);
			Semicolon ();
			return EndNode (gotoDefaultStatement);
		}
		
		public object VisitGotoStatement (GotoStatement gotoStatement, object data)
		{
			StartNode (gotoStatement);
			WriteKeyword ("goto");
			WriteIdentifier (gotoStatement.Label);
			Semicolon ();
			return EndNode (gotoStatement);
		}
		
		public object VisitIfElseStatement (IfElseStatement ifElseStatement, object data)
		{
			StartNode (ifElseStatement);
			WriteKeyword ("if", IfElseStatement.IfKeywordRole);
			Space (policy.SpaceBeforeIfParentheses);
			LPar ();
			Space (policy.SpacesWithinIfParentheses);
			ifElseStatement.Condition.AcceptVisitor (this, data);
			Space (policy.SpacesWithinIfParentheses);
			RPar ();
			WriteEmbeddedStatement (ifElseStatement.TrueStatement);
			if (!ifElseStatement.FalseStatement.IsNull) {
				WriteKeyword ("else", IfElseStatement.ElseKeywordRole);
				WriteEmbeddedStatement (ifElseStatement.FalseStatement);
			}
			return EndNode (ifElseStatement);
		}
		
		public object VisitLabelStatement (LabelStatement labelStatement, object data)
		{
			StartNode (labelStatement);
			WriteIdentifier (labelStatement.Label);
			WriteToken (":", LabelStatement.Roles.Colon);
			bool foundLabelledStatement = false;
			for (AstNode tmp = labelStatement.NextSibling; tmp != null; tmp = tmp.NextSibling) {
				if (tmp.Role == labelStatement.Role) {
					foundLabelledStatement = true;
				}
			}
			if (!foundLabelledStatement) {
				// introduce an EmptyStatement so that the output becomes syntactically valid
				WriteToken(";", LabelStatement.Roles.Semicolon);
			}
			NewLine ();
			return EndNode (labelStatement);
		}
		
		public object VisitLockStatement (LockStatement lockStatement, object data)
		{
			StartNode (lockStatement);
			WriteKeyword ("lock");
			Space (policy.SpaceBeforeLockParentheses);
			LPar ();
			Space (policy.SpacesWithinLockParentheses);
			lockStatement.Expression.AcceptVisitor (this, data);
			Space (policy.SpacesWithinLockParentheses);
			RPar ();
			WriteEmbeddedStatement (lockStatement.EmbeddedStatement);
			return EndNode (lockStatement);
		}
		
		public object VisitReturnStatement (ReturnStatement returnStatement, object data)
		{
			StartNode (returnStatement);
			WriteKeyword ("return");
			if (!returnStatement.Expression.IsNull) {
				Space ();
				returnStatement.Expression.AcceptVisitor (this, data);
			}
			Semicolon ();
			return EndNode (returnStatement);
		}
		
		public object VisitSwitchStatement (SwitchStatement switchStatement, object data)
		{
			StartNode (switchStatement);
			WriteKeyword ("switch");
			Space (policy.SpaceBeforeSwitchParentheses);
			LPar ();
			Space (policy.SpacesWithinSwitchParentheses);
			switchStatement.Expression.AcceptVisitor (this, data);
			Space (policy.SpacesWithinSwitchParentheses);
			RPar ();
			OpenBrace (policy.StatementBraceStyle);
			if (!policy.IndentSwitchBody)
				formatter.Unindent ();
			
			foreach (var section in switchStatement.SwitchSections)
				section.AcceptVisitor (this, data);
			
			if (!policy.IndentSwitchBody)
				formatter.Indent ();
			CloseBrace (policy.StatementBraceStyle);
			NewLine ();
			return EndNode (switchStatement);
		}
		
		public object VisitSwitchSection (SwitchSection switchSection, object data)
		{
			StartNode (switchSection);
			bool first = true;
			foreach (var label in switchSection.CaseLabels) {
				if (!first)
					NewLine ();
				label.AcceptVisitor (this, data);
				first = false;
			}
			if (policy.IndentCaseBody)
				formatter.Indent ();
			
			foreach (var statement in switchSection.Statements) {
				NewLine ();
				statement.AcceptVisitor (this, data);
			}
			
			if (policy.IndentCaseBody)
				formatter.Unindent ();
			
			return EndNode (switchSection);
		}
		
		public object VisitCaseLabel (CaseLabel caseLabel, object data)
		{
			StartNode (caseLabel);
			if (caseLabel.Expression.IsNull) {
				WriteKeyword ("default");
			} else {
				WriteKeyword ("case");
				Space ();
				caseLabel.Expression.AcceptVisitor (this, data);
			}
			WriteToken (":", CaseLabel.Roles.Colon);
			return EndNode (caseLabel);
		}
		
		public object VisitThrowStatement (ThrowStatement throwStatement, object data)
		{
			StartNode (throwStatement);
			WriteKeyword ("throw");
			if (!throwStatement.Expression.IsNull) {
				Space ();
				throwStatement.Expression.AcceptVisitor (this, data);
			}
			Semicolon ();
			return EndNode (throwStatement);
		}
		
		public object VisitTryCatchStatement (TryCatchStatement tryCatchStatement, object data)
		{
			StartNode (tryCatchStatement);
			WriteKeyword ("try", TryCatchStatement.TryKeywordRole);
			tryCatchStatement.TryBlock.AcceptVisitor (this, data);
			foreach (var catchClause in tryCatchStatement.CatchClauses)
				catchClause.AcceptVisitor (this, data);
			if (!tryCatchStatement.FinallyBlock.IsNull) {
				WriteKeyword ("finally", TryCatchStatement.FinallyKeywordRole);
				tryCatchStatement.FinallyBlock.AcceptVisitor (this, data);
			}
			return EndNode (tryCatchStatement);
		}
		
		public object VisitCatchClause (CatchClause catchClause, object data)
		{
			StartNode (catchClause);
			WriteKeyword ("catch");
			if (!catchClause.Type.IsNull) {
				Space (policy.SpaceBeforeCatchParentheses);
				LPar ();
				Space (policy.SpacesWithinCatchParentheses);
				catchClause.Type.AcceptVisitor (this, data);
				if (!string.IsNullOrEmpty(catchClause.VariableName)) {
					Space ();
					WriteIdentifier (catchClause.VariableName);
				}
				Space (policy.SpacesWithinCatchParentheses);
				RPar ();
			}
			catchClause.Body.AcceptVisitor (this, data);
			return EndNode (catchClause);
		}
		
		public object VisitUncheckedStatement (UncheckedStatement uncheckedStatement, object data)
		{
			StartNode (uncheckedStatement);
			WriteKeyword ("unchecked");
			uncheckedStatement.Body.AcceptVisitor (this, data);
			return EndNode (uncheckedStatement);
		}
		
		public object VisitUnsafeStatement (UnsafeStatement unsafeStatement, object data)
		{
			StartNode (unsafeStatement);
			WriteKeyword ("unsafe");
			unsafeStatement.Body.AcceptVisitor (this, data);
			return EndNode (unsafeStatement);
		}
		
		public object VisitUsingStatement (UsingStatement usingStatement, object data)
		{
			StartNode (usingStatement);
			WriteKeyword ("using");
			Space (policy.SpaceBeforeUsingParentheses);
			LPar ();
			Space (policy.SpacesWithinUsingParentheses);
			
			usingStatement.ResourceAcquisition.AcceptVisitor (this, data);
			
			Space (policy.SpacesWithinUsingParentheses);
			RPar ();
			
			WriteEmbeddedStatement (usingStatement.EmbeddedStatement);
			
			return EndNode (usingStatement);
		}
		
		public object VisitVariableDeclarationStatement (VariableDeclarationStatement variableDeclarationStatement, object data)
		{
			StartNode (variableDeclarationStatement);
			variableDeclarationStatement.Type.AcceptVisitor (this, data);
			Space ();
			WriteCommaSeparatedList (variableDeclarationStatement.Variables);
			Semicolon ();
			return EndNode (variableDeclarationStatement);
		}
		
		public object VisitWhileStatement (WhileStatement whileStatement, object data)
		{
			StartNode (whileStatement);
			WriteKeyword ("while", WhileStatement.WhileKeywordRole);
			Space (policy.SpaceBeforeWhileParentheses);
			LPar ();
			Space (policy.SpacesWithinWhileParentheses);
			whileStatement.Condition.AcceptVisitor (this, data);
			Space (policy.SpacesWithinWhileParentheses);
			RPar ();
			WriteEmbeddedStatement (whileStatement.EmbeddedStatement);
			return EndNode (whileStatement);
		}
		
		public object VisitYieldBreakStatement (YieldBreakStatement yieldBreakStatement, object data)
		{
			StartNode (yieldBreakStatement);
			WriteKeyword ("yield", YieldBreakStatement.YieldKeywordRole);
			WriteKeyword ("break", YieldBreakStatement.BreakKeywordRole);
			Semicolon ();
			return EndNode (yieldBreakStatement);
		}
		
		public object VisitYieldStatement (YieldStatement yieldStatement, object data)
		{
			StartNode (yieldStatement);
			WriteKeyword ("yield", YieldStatement.YieldKeywordRole);
			WriteKeyword ("return", YieldStatement.ReturnKeywordRole);
			Space ();
			yieldStatement.Expression.AcceptVisitor (this, data);
			Semicolon ();
			return EndNode (yieldStatement);
		}

		#endregion
		
		#region TypeMembers
		public object VisitAccessor (Accessor accessor, object data)
		{
			StartNode (accessor);
			WriteAttributes (accessor.Attributes);
			WriteModifiers (accessor.ModifierTokens);
			if (accessor.Role == PropertyDeclaration.GetterRole) {
				WriteKeyword ("get");
			} else if (accessor.Role == PropertyDeclaration.SetterRole) {
				WriteKeyword ("set");
			} else if (accessor.Role == CustomEventDeclaration.AddAccessorRole) {
				WriteKeyword ("add");
			} else if (accessor.Role == CustomEventDeclaration.RemoveAccessorRole) {
				WriteKeyword ("remove");
			}
			WriteMethodBody (accessor.Body);
			return EndNode (accessor);
		}
		
		public object VisitConstructorDeclaration (ConstructorDeclaration constructorDeclaration, object data)
		{
			StartNode (constructorDeclaration);
			WriteAttributes (constructorDeclaration.Attributes);
			WriteModifiers (constructorDeclaration.ModifierTokens);
			TypeDeclaration type = constructorDeclaration.Parent as TypeDeclaration;
			WriteIdentifier (type != null ? type.Name : constructorDeclaration.Name);
			Space (policy.SpaceBeforeConstructorDeclarationParentheses);
			WriteCommaSeparatedListInParenthesis (constructorDeclaration.Parameters, policy.SpaceWithinMethodDeclarationParentheses);
			if (!constructorDeclaration.Initializer.IsNull) {
				Space ();
				constructorDeclaration.Initializer.AcceptVisitor (this, data);
			}
			WriteMethodBody (constructorDeclaration.Body);
			return EndNode (constructorDeclaration);
		}
		
		public object VisitConstructorInitializer (ConstructorInitializer constructorInitializer, object data)
		{
			StartNode (constructorInitializer);
			WriteToken (":", ConstructorInitializer.Roles.Colon);
			Space ();
			if (constructorInitializer.ConstructorInitializerType == ConstructorInitializerType.This) {
				WriteKeyword ("this");
			} else {
				WriteKeyword ("base");
			}
			Space (policy.SpaceBeforeMethodCallParentheses);
			WriteCommaSeparatedListInParenthesis (constructorInitializer.Arguments, policy.SpaceWithinMethodCallParentheses);
			return EndNode (constructorInitializer);
		}
		
		public object VisitDestructorDeclaration (DestructorDeclaration destructorDeclaration, object data)
		{
			StartNode (destructorDeclaration);
			WriteAttributes (destructorDeclaration.Attributes);
			WriteModifiers (destructorDeclaration.ModifierTokens);
			WriteToken ("~", DestructorDeclaration.TildeRole);
			TypeDeclaration type = destructorDeclaration.Parent as TypeDeclaration;
			WriteIdentifier (type != null ? type.Name : destructorDeclaration.Name);
			Space (policy.SpaceBeforeConstructorDeclarationParentheses);
			LPar ();
			RPar ();
			WriteMethodBody (destructorDeclaration.Body);
			return EndNode (destructorDeclaration);
		}
		
		public object VisitEnumMemberDeclaration (EnumMemberDeclaration enumMemberDeclaration, object data)
		{
			StartNode (enumMemberDeclaration);
			WriteAttributes (enumMemberDeclaration.Attributes);
			WriteModifiers (enumMemberDeclaration.ModifierTokens);
			WriteIdentifier (enumMemberDeclaration.Name);
			if (!enumMemberDeclaration.Initializer.IsNull) {
				Space (policy.SpaceAroundAssignment);
				WriteToken ("=", EnumMemberDeclaration.Roles.Assign);
				Space (policy.SpaceAroundAssignment);
				enumMemberDeclaration.Initializer.AcceptVisitor (this, data);
			}
			return EndNode (enumMemberDeclaration);
		}
		
		public object VisitEventDeclaration (EventDeclaration eventDeclaration, object data)
		{
			StartNode (eventDeclaration);
			WriteAttributes (eventDeclaration.Attributes);
			WriteModifiers (eventDeclaration.ModifierTokens);
			WriteKeyword ("event");
			eventDeclaration.ReturnType.AcceptVisitor (this, data);
			Space ();
			WriteCommaSeparatedList (eventDeclaration.Variables);
			Semicolon ();
			return EndNode (eventDeclaration);
		}
		
		public object VisitCustomEventDeclaration (CustomEventDeclaration customEventDeclaration, object data)
		{
			StartNode (customEventDeclaration);
			WriteAttributes (customEventDeclaration.Attributes);
			WriteModifiers (customEventDeclaration.ModifierTokens);
			WriteKeyword ("event");
			customEventDeclaration.ReturnType.AcceptVisitor (this, data);
			Space ();
			WritePrivateImplementationType (customEventDeclaration.PrivateImplementationType);
			WriteIdentifier (customEventDeclaration.Name);
			OpenBrace (policy.EventBraceStyle);
			// output add/remove in their original order
			foreach (AstNode node in customEventDeclaration.Children) {
				if (node.Role == CustomEventDeclaration.AddAccessorRole || node.Role == CustomEventDeclaration.RemoveAccessorRole) {
					node.AcceptVisitor (this, data);
				}
			}
			CloseBrace (policy.EventBraceStyle);
			NewLine ();
			return EndNode (customEventDeclaration);
		}
		
		public object VisitFieldDeclaration (FieldDeclaration fieldDeclaration, object data)
		{
			StartNode (fieldDeclaration);
			WriteAttributes (fieldDeclaration.Attributes);
			WriteModifiers (fieldDeclaration.ModifierTokens);
			fieldDeclaration.ReturnType.AcceptVisitor (this, data);
			Space ();
			WriteCommaSeparatedList (fieldDeclaration.Variables);
			Semicolon ();
			return EndNode (fieldDeclaration);
		}
		
		public object VisitFixedFieldDeclaration (FixedFieldDeclaration fixedFieldDeclaration, object data)
		{
			StartNode (fixedFieldDeclaration);
			WriteAttributes (fixedFieldDeclaration.Attributes);
			WriteModifiers (fixedFieldDeclaration.ModifierTokens);
			WriteKeyword ("fixed");
			Space ();
			fixedFieldDeclaration.ReturnType.AcceptVisitor (this, data);
			Space ();
			WriteCommaSeparatedList (fixedFieldDeclaration.Variables);
			Semicolon ();
			return EndNode (fixedFieldDeclaration);
		}
		
		public object VisitFixedVariableInitializer (FixedVariableInitializer fixedVariableInitializer, object data)
		{
			StartNode (fixedVariableInitializer);
			WriteIdentifier (fixedVariableInitializer.Name);
			if (!fixedVariableInitializer.CountExpression.IsNull) {
				WriteToken ("[", AstNode.Roles.LBracket);
				Space (policy.SpacesWithinBrackets);
				fixedVariableInitializer.CountExpression.AcceptVisitor (this, data);
				Space (policy.SpacesWithinBrackets);
				WriteToken ("]", AstNode.Roles.RBracket);
			}
			return EndNode (fixedVariableInitializer);
		}
		
		public object VisitIndexerDeclaration (IndexerDeclaration indexerDeclaration, object data)
		{
			StartNode (indexerDeclaration);
			WriteAttributes (indexerDeclaration.Attributes);
			WriteModifiers (indexerDeclaration.ModifierTokens);
			indexerDeclaration.ReturnType.AcceptVisitor (this, data);
			WritePrivateImplementationType (indexerDeclaration.PrivateImplementationType);
			WriteKeyword ("this");
			Space (policy.SpaceBeforeMethodDeclarationParentheses);
			WriteCommaSeparatedListInBrackets (indexerDeclaration.Parameters, policy.SpaceWithinMethodDeclarationParentheses);
			OpenBrace (policy.PropertyBraceStyle);
			// output get/set in their original order
			foreach (AstNode node in indexerDeclaration.Children) {
				if (node.Role == IndexerDeclaration.GetterRole || node.Role == IndexerDeclaration.SetterRole) {
					node.AcceptVisitor (this, data);
				}
			}
			CloseBrace (policy.PropertyBraceStyle);
			NewLine ();
			return EndNode (indexerDeclaration);
		}
		
		public object VisitMethodDeclaration (MethodDeclaration methodDeclaration, object data)
		{
			StartNode (methodDeclaration);
			WriteAttributes (methodDeclaration.Attributes);
			WriteModifiers (methodDeclaration.ModifierTokens);
			methodDeclaration.ReturnType.AcceptVisitor (this, data);
			Space ();
			WritePrivateImplementationType (methodDeclaration.PrivateImplementationType);
			WriteIdentifier (methodDeclaration.Name);
			WriteTypeParameters (methodDeclaration.TypeParameters);
			Space (policy.SpaceBeforeMethodDeclarationParentheses);
			WriteCommaSeparatedListInParenthesis (methodDeclaration.Parameters, policy.SpaceWithinMethodDeclarationParentheses);
			foreach (Constraint constraint in methodDeclaration.Constraints) {
				constraint.AcceptVisitor (this, data);
			}
			WriteMethodBody (methodDeclaration.Body);
			return EndNode (methodDeclaration);
		}
		
		public object VisitOperatorDeclaration (OperatorDeclaration operatorDeclaration, object data)
		{
			StartNode (operatorDeclaration);
			WriteAttributes (operatorDeclaration.Attributes);
			WriteModifiers (operatorDeclaration.ModifierTokens);
			if (operatorDeclaration.OperatorType == OperatorType.Explicit) {
				WriteKeyword ("explicit", OperatorDeclaration.OperatorTypeRole);
			} else if (operatorDeclaration.OperatorType == OperatorType.Implicit) {
				WriteKeyword ("implicit", OperatorDeclaration.OperatorTypeRole);
			} else {
				operatorDeclaration.ReturnType.AcceptVisitor (this, data);
			}
			WriteKeyword ("operator", OperatorDeclaration.OperatorKeywordRole);
			Space ();
			if (operatorDeclaration.OperatorType == OperatorType.Explicit
			    || operatorDeclaration.OperatorType == OperatorType.Implicit) {
				operatorDeclaration.ReturnType.AcceptVisitor (this, data);
			} else {
				WriteToken (OperatorDeclaration.GetToken (operatorDeclaration.OperatorType), OperatorDeclaration.OperatorTypeRole);
			}
			Space (policy.SpaceBeforeMethodDeclarationParentheses);
			WriteCommaSeparatedListInParenthesis (operatorDeclaration.Parameters, policy.SpaceWithinMethodDeclarationParentheses);
			WriteMethodBody (operatorDeclaration.Body);
			return EndNode (operatorDeclaration);
		}
		
		public object VisitParameterDeclaration (ParameterDeclaration parameterDeclaration, object data)
		{
			StartNode (parameterDeclaration);
			WriteAttributes (parameterDeclaration.Attributes);
			switch (parameterDeclaration.ParameterModifier) {
			case ParameterModifier.Ref:
				WriteKeyword ("ref", ParameterDeclaration.ModifierRole);
				break;
			case ParameterModifier.Out:
				WriteKeyword ("out", ParameterDeclaration.ModifierRole);
				break;
			case ParameterModifier.Params:
				WriteKeyword ("params", ParameterDeclaration.ModifierRole);
				break;
			case ParameterModifier.This:
				WriteKeyword ("this", ParameterDeclaration.ModifierRole);
				break;
			}
			parameterDeclaration.Type.AcceptVisitor (this, data);
			if (!parameterDeclaration.Type.IsNull && !string.IsNullOrEmpty (parameterDeclaration.Name))
				Space ();
			if (!string.IsNullOrEmpty (parameterDeclaration.Name))
				WriteIdentifier (parameterDeclaration.Name);
			if (!parameterDeclaration.DefaultExpression.IsNull) {
				Space (policy.SpaceAroundAssignment);
				WriteToken ("=", ParameterDeclaration.Roles.Assign);
				Space (policy.SpaceAroundAssignment);
				parameterDeclaration.DefaultExpression.AcceptVisitor (this, data);
			}
			return EndNode (parameterDeclaration);
		}
		
		public object VisitPropertyDeclaration (PropertyDeclaration propertyDeclaration, object data)
		{
			StartNode (propertyDeclaration);
			WriteAttributes (propertyDeclaration.Attributes);
			WriteModifiers (propertyDeclaration.ModifierTokens);
			propertyDeclaration.ReturnType.AcceptVisitor (this, data);
			Space ();
			WritePrivateImplementationType (propertyDeclaration.PrivateImplementationType);
			WriteIdentifier (propertyDeclaration.Name);
			OpenBrace (policy.PropertyBraceStyle);
			// output get/set in their original order
			foreach (AstNode node in propertyDeclaration.Children) {
				if (node.Role == IndexerDeclaration.GetterRole || node.Role == IndexerDeclaration.SetterRole) {
					node.AcceptVisitor (this, data);
				}
			}
			CloseBrace (policy.PropertyBraceStyle);
			NewLine ();
			return EndNode (propertyDeclaration);
		}

		#endregion
		
		#region Other nodes
		public object VisitVariableInitializer (VariableInitializer variableInitializer, object data)
		{
			StartNode (variableInitializer);
			WriteIdentifier (variableInitializer.Name);
			if (!variableInitializer.Initializer.IsNull) {
				Space (policy.SpaceAroundAssignment);
				WriteToken ("=", VariableInitializer.Roles.Assign);
				Space (policy.SpaceAroundAssignment);
				variableInitializer.Initializer.AcceptVisitor (this, data);
			}
			return EndNode (variableInitializer);
		}
		
		public object VisitCompilationUnit (CompilationUnit compilationUnit, object data)
		{
			// don't do node tracking as we visit all children directly
			foreach (AstNode node in compilationUnit.Children)
				node.AcceptVisitor (this, data);
			return null;
		}
		
		public object VisitSimpleType (SimpleType simpleType, object data)
		{
			StartNode (simpleType);
			WriteIdentifier (simpleType.Identifier);
			WriteTypeArguments (simpleType.TypeArguments);
			return EndNode (simpleType);
		}
		
		public object VisitMemberType (MemberType memberType, object data)
		{
			StartNode (memberType);
			memberType.Target.AcceptVisitor (this, data);
			if (memberType.IsDoubleColon)
				WriteToken ("::", MemberType.Roles.Dot);
			else
				WriteToken (".", MemberType.Roles.Dot);
			WriteIdentifier (memberType.MemberName);
			WriteTypeArguments (memberType.TypeArguments);
			return EndNode (memberType);
		}
		
		public object VisitComposedType (ComposedType composedType, object data)
		{
			StartNode (composedType);
			composedType.BaseType.AcceptVisitor (this, data);
			if (composedType.HasNullableSpecifier)
				WriteToken ("?", ComposedType.NullableRole);
			for (int i = 0; i < composedType.PointerRank; i++)
				WriteToken ("*", ComposedType.PointerRole);
			foreach (var node in composedType.ArraySpecifiers)
				node.AcceptVisitor (this, data);
			return EndNode (composedType);
		}
		
		public object VisitArraySpecifier (ArraySpecifier arraySpecifier, object data)
		{
			StartNode (arraySpecifier);
			WriteToken ("[", ArraySpecifier.Roles.LBracket);
			foreach (var comma in arraySpecifier.GetChildrenByRole(ArraySpecifier.Roles.Comma)) {
				WriteSpecialsUpToNode (comma);
				formatter.WriteToken (",");
				lastWritten = LastWritten.Other;
			}
			WriteToken ("]", ArraySpecifier.Roles.RBracket);
			return EndNode (arraySpecifier);
		}
		
		public object VisitPrimitiveType (PrimitiveType primitiveType, object data)
		{
			StartNode (primitiveType);
			WriteKeyword (primitiveType.Keyword);
			if (primitiveType.Keyword == "new") {
				// new() constraint
				LPar ();
				RPar ();
			}
			return EndNode (primitiveType);
		}
		
		public object VisitComment (Comment comment, object data)
		{
			if (lastWritten == LastWritten.Division) {
				// When there's a comment starting after a division operator
				// "1.0 / /*comment*/a", then we need to insert a space in front of the comment.
				formatter.Space ();
			}
			formatter.StartNode(comment);
			formatter.WriteComment (comment.CommentType, comment.Content);
			formatter.EndNode(comment);
			lastWritten = LastWritten.Whitespace;
			return null;
		}
		
		public object VisitTypeParameterDeclaration (TypeParameterDeclaration typeParameterDeclaration, object data)
		{
			StartNode (typeParameterDeclaration);
			WriteAttributes (typeParameterDeclaration.Attributes);
			switch (typeParameterDeclaration.Variance) {
			case VarianceModifier.Invariant:
				break;
			case VarianceModifier.Covariant:
				WriteKeyword ("out");
				break;
			case VarianceModifier.Contravariant:
				WriteKeyword ("in");
				break;
			default:
				throw new NotSupportedException ("Invalid value for VarianceModifier");
			}
			WriteIdentifier (typeParameterDeclaration.Name);
			return EndNode (typeParameterDeclaration);
		}
		
		public object VisitConstraint (Constraint constraint, object data)
		{
			StartNode (constraint);
			Space ();
			WriteKeyword ("where");
			WriteIdentifier (constraint.TypeParameter);
			Space ();
			WriteToken (":", Constraint.ColonRole);
			Space ();
			WriteCommaSeparatedList (constraint.BaseTypes);
			return EndNode (constraint);
		}
		
		public object VisitCSharpTokenNode (CSharpTokenNode cSharpTokenNode, object data)
		{
			CSharpModifierToken mod = cSharpTokenNode as CSharpModifierToken;
			if (mod != null) {
				StartNode (mod);
				WriteKeyword (CSharpModifierToken.GetModifierName (mod.Modifier));
				return EndNode (mod);
			} else {
				throw new NotSupportedException ("Should never visit individual tokens");
			}
		}
		
		public object VisitIdentifier (Identifier identifier, object data)
		{
			StartNode (identifier);
			WriteIdentifier (identifier.Name);
			return EndNode (identifier);
		}

		#endregion
		
		#region Pattern Nodes
		public object VisitPatternPlaceholder (AstNode placeholder, PatternMatching.Pattern pattern, object data)
		{
			StartNode (placeholder);
			pattern.AcceptVisitor (this, data);
			return EndNode (placeholder);
		}
		
		object IPatternAstVisitor<object, object>.VisitAnyNode (AnyNode anyNode, object data)
		{
			if (!string.IsNullOrEmpty (anyNode.GroupName)) {
				WriteIdentifier (anyNode.GroupName);
				WriteToken (":", AstNode.Roles.Colon);
			}
			WriteKeyword ("anyNode");
			return null;
		}
		
		object IPatternAstVisitor<object, object>.VisitBackreference (Backreference backreference, object data)
		{
			WriteKeyword ("backreference");
			LPar ();
			WriteIdentifier (backreference.ReferencedGroupName);
			RPar ();
			return null;
		}
		
		object IPatternAstVisitor<object, object>.VisitIdentifierExpressionBackreference (IdentifierExpressionBackreference identifierExpressionBackreference, object data)
		{
			WriteKeyword ("identifierBackreference");
			LPar ();
			WriteIdentifier (identifierExpressionBackreference.ReferencedGroupName);
			RPar ();
			return null;
		}
		
		object IPatternAstVisitor<object, object>.VisitChoice (Choice choice, object data)
		{
			WriteKeyword ("choice");
			Space ();
			LPar ();
			NewLine ();
			formatter.Indent ();
			foreach (INode alternative in choice) {
				VisitNodeInPattern (alternative, data);
				if (alternative != choice.Last ())
					WriteToken (",", AstNode.Roles.Comma);
				NewLine ();
			}
			formatter.Unindent ();
			RPar ();
			return null;
		}
		
		object IPatternAstVisitor<object, object>.VisitNamedNode (NamedNode namedNode, object data)
		{
			if (!string.IsNullOrEmpty (namedNode.GroupName)) {
				WriteIdentifier (namedNode.GroupName);
				WriteToken (":", AstNode.Roles.Colon);
			}
			VisitNodeInPattern (namedNode.ChildNode, data);
			return null;
		}
		
		object IPatternAstVisitor<object, object>.VisitRepeat (Repeat repeat, object data)
		{
			WriteKeyword ("repeat");
			LPar ();
			if (repeat.MinCount != 0 || repeat.MaxCount != int.MaxValue) {
				WriteIdentifier (repeat.MinCount.ToString ());
				WriteToken (",", AstNode.Roles.Comma);
				WriteIdentifier (repeat.MaxCount.ToString ());
				WriteToken (",", AstNode.Roles.Comma);
			}
			VisitNodeInPattern (repeat.ChildNode, data);
			RPar ();
			return null;
		}
		
		object IPatternAstVisitor<object, object>.VisitOptionalNode (OptionalNode optionalNode, object data)
		{
			WriteKeyword ("optional");
			LPar ();
			VisitNodeInPattern (optionalNode.ChildNode, data);
			RPar ();
			return null;
		}
		
		void VisitNodeInPattern (INode childNode, object data)
		{
			AstNode astNode = childNode as AstNode;
			if (astNode != null) {
				astNode.AcceptVisitor (this, data);
			} else {
				Pattern pattern = childNode as Pattern;
				if (pattern != null) {
					pattern.AcceptVisitor (this, data);
				} else {
					throw new InvalidOperationException ("Unknown node type in pattern");
				}
			}
		}
		#endregion
	}
}