// CodeContracts
// 
// Copyright (c) Microsoft Corporation
// 
// All rights reserved. 
// 
// MIT License
// 
// 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.CodeDom.Compiler;
using System.Collections;
using System.Diagnostics;
#if FxCop
using AttributeList = Microsoft.Cci.AttributeNodeCollection;
using BlockList = Microsoft.Cci.BlockCollection;
using ExpressionList = Microsoft.Cci.ExpressionCollection;
using InterfaceList = Microsoft.Cci.InterfaceCollection;
using MemberList = Microsoft.Cci.MemberCollection;
using NodeList = Microsoft.Cci.NodeCollection;
using ParameterList = Microsoft.Cci.ParameterCollection;
using SecurityAttributeList = Microsoft.Cci.SecurityAttributeCollection;
using StatementList = Microsoft.Cci.StatementCollection;
using TypeNodeList = Microsoft.Cci.TypeNodeCollection;
using Property = Microsoft.Cci.PropertyNode;
using Module = Microsoft.Cci.ModuleNode;
using Return = Microsoft.Cci.ReturnNode;
using Class = Microsoft.Cci.ClassNode;
using Interface = Microsoft.Cci.InterfaceNode;
using Event = Microsoft.Cci.EventNode;
using Throw = Microsoft.Cci.ThrowNode;
#endif
#if CCINamespace
namespace Microsoft.Cci{
#else
namespace System.Compiler{
#endif

  /// <summary>
  /// Base for all classes that process the IR using the visitor pattern.
  /// </summary>
#if !FxCop 
  public 
#endif    
  abstract class Visitor{
    /// <summary>
    /// Switches on node.NodeType to call a visitor method that has been specialized for node.
    /// </summary>
    /// <param name="node">The node to be visited.</param>
    /// <returns> Returns null if node is null. Otherwise returns an updated node (possibly a different object).</returns>
    public abstract Node Visit(Node node);
#if !MinimalReader    
    /// <summary>
    /// Transfers the state from one visitor to another. This enables separate visitor instances to cooperative process a single IR.
    /// </summary>
    public virtual void TransferStateTo(Visitor targetVisitor){
    }
#endif
    public virtual ExpressionList VisitExpressionList(ExpressionList list){
      if (list == null) return null;
      for( int i = 0, n = list.Count; i < n; i++)
        list[i] = (Expression)this.Visit(list[i]);
      return list;
    }
  }

  /// <summary>
  /// Walks an IR, mutuating it into a new form
  /// </summary>   
#if !FxCop
  public
#endif  
  class StandardVisitor: Visitor{
#if !MinimalReader
    public Visitor callingVisitor;
#endif
    protected bool memberListNamesChanged;
    
    public StandardVisitor(){
    }
#if !MinimalReader
    public StandardVisitor(Visitor callingVisitor){
      this.callingVisitor = callingVisitor;
    }
#endif
    public virtual Node VisitUnknownNodeType(Node node){
#if !MinimalReader
      Visitor visitor = this.GetVisitorFor(node);
      if (visitor == null) return node;
      if (this.callingVisitor != null)
        //Allow specialized state (unknown to this visitor) to propagate all the way down to the new visitor
        this.callingVisitor.TransferStateTo(visitor);
      this.TransferStateTo(visitor);
      node = visitor.Visit(node);
      visitor.TransferStateTo(this);
      if (this.callingVisitor != null)
        //Propagate specialized state (unknown to this visitor) all the way up the chain
        visitor.TransferStateTo(this.callingVisitor);
#else
      Debug.Assert(false);
#endif
      return node;
    }
#if !MinimalReader
    public virtual Visitor GetVisitorFor(Node node){
      if (node == null) return null;
      return (Visitor)node.GetVisitorFor(this, this.GetType().Name);
    }
#endif
    public override Node Visit(Node node){
      if (node == null) return null;
      switch (node.NodeType){
#if !MinimalReader && !CodeContracts
        case NodeType.Acquire:
          return this.VisitAcquire((Acquire)node);
#endif
        case NodeType.AddressDereference:
          return this.VisitAddressDereference((AddressDereference)node);
#if !MinimalReader && !CodeContracts
        case NodeType.AliasDefinition :
          return this.VisitAliasDefinition((AliasDefinition)node);
        case NodeType.AnonymousNestedFunction:
          return this.VisitAnonymousNestedFunction((AnonymousNestedFunction)node);
        case NodeType.ApplyToAll :
          return this.VisitApplyToAll((ApplyToAll)node);
#endif
        case NodeType.Arglist :
          return this.VisitExpression((Expression)node);
#if !MinimalReader && !CodeContracts
        case NodeType.ArglistArgumentExpression:
          return this.VisitArglistArgumentExpression((ArglistArgumentExpression)node);
        case NodeType.ArglistExpression:
          return this.VisitArglistExpression((ArglistExpression)node);
#endif
        case NodeType.ArrayType : 
          Debug.Assert(false); return null;
        case NodeType.Assembly : 
          return this.VisitAssembly((AssemblyNode)node);
        case NodeType.AssemblyReference :
          return this.VisitAssemblyReference((AssemblyReference)node);
#if !MinimalReader
        case NodeType.Assertion:
          return this.VisitAssertion((Assertion)node);
        case NodeType.Assumption:
          return this.VisitAssumption((Assumption)node);
        case NodeType.AssignmentExpression:
          return this.VisitAssignmentExpression((AssignmentExpression)node);
#endif
        case NodeType.AssignmentStatement : 
          return this.VisitAssignmentStatement((AssignmentStatement)node);
        case NodeType.Attribute :
          return this.VisitAttributeNode((AttributeNode)node);
#if !MinimalReader && !CodeContracts
        case NodeType.Base :
          return this.VisitBase((Base)node);
#endif
        case NodeType.Block : 
          return this.VisitBlock((Block)node);
#if !MinimalReader
        case NodeType.BlockExpression :
          return this.VisitBlockExpression((BlockExpression)node);
#endif
        case NodeType.Branch :
          return this.VisitBranch((Branch)node);
#if !MinimalReader && !CodeContracts
        case NodeType.Compilation:
          return this.VisitCompilation((Compilation)node);
        case NodeType.CompilationUnit:
          return this.VisitCompilationUnit((CompilationUnit)node);
        case NodeType.CompilationUnitSnippet:
          return this.VisitCompilationUnitSnippet((CompilationUnitSnippet)node);
#endif
#if ExtendedRuntime
        case NodeType.ConstrainedType:
          return this.VisitConstrainedType((ConstrainedType)node);
#endif
#if !MinimalReader && !CodeContracts
        case NodeType.Continue :
          return this.VisitContinue((Continue)node);
        case NodeType.CurrentClosure :
          return this.VisitCurrentClosure((CurrentClosure)node);
#endif
        case NodeType.DebugBreak :
          return node;
        case NodeType.Call :
        case NodeType.Calli :
        case NodeType.Callvirt :
        case NodeType.Jmp :
#if !MinimalReader
        case NodeType.MethodCall :
#endif
          return this.VisitMethodCall((MethodCall)node);
#if !MinimalReader && !CodeContracts
        case NodeType.Catch :
          return this.VisitCatch((Catch)node);
#endif
        case NodeType.Class :
          return this.VisitClass((Class)node);
#if !MinimalReader && !CodeContracts
        case NodeType.CoerceTuple :
          return this.VisitCoerceTuple((CoerceTuple)node);
        case NodeType.CollectionEnumerator :
          return this.VisitCollectionEnumerator((CollectionEnumerator)node);
        case NodeType.Composition :
          return this.VisitComposition((Composition)node);
#endif
        case NodeType.Construct :
          return this.VisitConstruct((Construct)node);
        case NodeType.ConstructArray :
          return this.VisitConstructArray((ConstructArray)node);
#if !MinimalReader && !CodeContracts
        case NodeType.ConstructDelegate :
          return this.VisitConstructDelegate((ConstructDelegate)node);
        case NodeType.ConstructFlexArray :
          return this.VisitConstructFlexArray((ConstructFlexArray)node);
        case NodeType.ConstructIterator :
          return this.VisitConstructIterator((ConstructIterator)node);
        case NodeType.ConstructTuple :
          return this.VisitConstructTuple((ConstructTuple)node);
#endif
        case NodeType.DelegateNode :
          return this.VisitDelegateNode((DelegateNode)node);
#if !MinimalReader && !CodeContracts
        case NodeType.DoWhile:
          return this.VisitDoWhile((DoWhile)node);
#endif
        case NodeType.Dup :
          return this.VisitExpression((Expression)node);
        case NodeType.EndFilter :
          return this.VisitEndFilter((EndFilter)node);
        case NodeType.EndFinally:
          return this.VisitEndFinally((EndFinally)node);
        case NodeType.EnumNode :
          return this.VisitEnumNode((EnumNode)node);
        case NodeType.Event: 
          return this.VisitEvent((Event)node);
#if ExtendedRuntime || CodeContracts
        case NodeType.EnsuresExceptional :
          return this.VisitEnsuresExceptional((EnsuresExceptional)node);
#endif
#if !MinimalReader && !CodeContracts
        case NodeType.Exit :
          return this.VisitExit((Exit)node);
        case NodeType.Read :
        case NodeType.Write :
          return this.VisitExpose((Expose)node);
        case NodeType.ExpressionSnippet:
          return this.VisitExpressionSnippet((ExpressionSnippet)node);
#endif
        case NodeType.ExpressionStatement :
          return this.VisitExpressionStatement((ExpressionStatement)node);
#if !MinimalReader && !CodeContracts
        case NodeType.FaultHandler :
          return this.VisitFaultHandler((FaultHandler)node);
#endif
        case NodeType.Field :
          return this.VisitField((Field)node);
#if !MinimalReader && !CodeContracts
        case NodeType.FieldInitializerBlock:
          return this.VisitFieldInitializerBlock((FieldInitializerBlock)node);
        case NodeType.Finally :
          return this.VisitFinally((Finally)node);
        case NodeType.Filter :
          return this.VisitFilter((Filter)node);
        case NodeType.Fixed:
          return this.VisitFixed((Fixed)node);
        case NodeType.For :
          return this.VisitFor((For)node);
        case NodeType.ForEach :
          return this.VisitForEach((ForEach)node);
        case NodeType.FunctionDeclaration:
          return this.VisitFunctionDeclaration((FunctionDeclaration)node);
        case NodeType.Goto :
          return this.VisitGoto((Goto)node);
        case NodeType.GotoCase:
          return this.VisitGotoCase((GotoCase)node);
#endif
        case NodeType.Identifier :
          return this.VisitIdentifier((Identifier)node);
#if !MinimalReader && !CodeContracts
        case NodeType.If :
          return this.VisitIf((If)node);
        case NodeType.ImplicitThis :
          return this.VisitImplicitThis((ImplicitThis)node);
#endif
        case NodeType.Indexer :
          return this.VisitIndexer((Indexer)node);
        case NodeType.InstanceInitializer :
          return this.VisitInstanceInitializer((InstanceInitializer)node);
#if ExtendedRuntime || CodeContracts
        case NodeType.Invariant :
          return this.VisitInvariant((Invariant)node);
#endif
        case NodeType.StaticInitializer :
          return this.VisitStaticInitializer((StaticInitializer)node);
        case NodeType.Method: 
          return this.VisitMethod((Method)node);
#if !MinimalReader && !CodeContracts
        case NodeType.TemplateInstance:
          return this.VisitTemplateInstance((TemplateInstance)node);
        case NodeType.StackAlloc:
          return this.VisitStackAlloc((StackAlloc)node);
#endif
        case NodeType.Interface :
          return this.VisitInterface((Interface)node);
#if !MinimalReader
        case NodeType.LabeledStatement :
          return this.VisitLabeledStatement((LabeledStatement)node);
#endif
        case NodeType.Literal:
          return this.VisitLiteral((Literal)node);
        case NodeType.Local :
          return this.VisitLocal((Local)node);
#if !MinimalReader && !CodeContracts
        case NodeType.LocalDeclaration:
          return this.VisitLocalDeclaration((LocalDeclaration)node);
        case NodeType.LocalDeclarationsStatement:
          return this.VisitLocalDeclarationsStatement((LocalDeclarationsStatement)node);
        case NodeType.Lock :
          return this.VisitLock((Lock)node);
        case NodeType.LRExpression:
          return this.VisitLRExpression((LRExpression)node);
#endif
        case NodeType.MemberBinding :
          return this.VisitMemberBinding((MemberBinding)node);
#if ExtendedRuntime || CodeContracts
        case NodeType.MethodContract :
          return this.VisitMethodContract((MethodContract)node);
#endif
        case NodeType.Module :
          return this.VisitModule((Module)node);
        case NodeType.ModuleReference :
          return this.VisitModuleReference((ModuleReference)node);
#if !MinimalReader && !CodeContracts
        case NodeType.NameBinding :
          return this.VisitNameBinding((NameBinding)node);
#endif
        case NodeType.NamedArgument :
          return this.VisitNamedArgument((NamedArgument)node);
#if !MinimalReader && !CodeContracts
        case NodeType.Namespace :
          return this.VisitNamespace((Namespace)node);
#endif
        case NodeType.Nop :
#if !MinimalReader
        case NodeType.SwitchCaseBottom :
#endif
          return node;
#if ExtendedRuntime || CodeContracts
        case NodeType.EnsuresNormal :
          return this.VisitEnsuresNormal((EnsuresNormal)node);
        case NodeType.OldExpression:
          return this.VisitOldExpression((OldExpression)node);
        case NodeType.ReturnValue:
          return this.VisitReturnValue((ReturnValue)node);
        case NodeType.RequiresOtherwise :
          return this.VisitRequiresOtherwise((RequiresOtherwise)node);
        case NodeType.RequiresPlain :
          return this.VisitRequiresPlain((RequiresPlain)node);
#endif
        case NodeType.OptionalModifier:
        case NodeType.RequiredModifier:
          //TODO: type modifers should only be visited via VisitTypeReference
          return this.VisitTypeModifier((TypeModifier)node);
        case NodeType.Parameter :
          return this.VisitParameter((Parameter)node);
        case NodeType.Pop :
          return this.VisitExpression((Expression)node);
#if !MinimalReader
        case NodeType.PrefixExpression:
          return this.VisitPrefixExpression((PrefixExpression)node);
        case NodeType.PostfixExpression:
          return this.VisitPostfixExpression((PostfixExpression)node);
#endif
        case NodeType.Property: 
          return this.VisitProperty((Property)node);
#if !MinimalReader && !CodeContracts
        case NodeType.Quantifier:
          return this.VisitQuantifier((Quantifier)node);
        case NodeType.Comprehension: 
          return this.VisitComprehension((Comprehension)node);
        case NodeType.ComprehensionBinding: 
          return this.VisitComprehensionBinding((ComprehensionBinding)node);
        case NodeType.QualifiedIdentifer :
          return this.VisitQualifiedIdentifier((QualifiedIdentifier)node);
#endif
        case NodeType.Rethrow :
        case NodeType.Throw :
          return this.VisitThrow((Throw)node);
#if !MinimalReader && !CodeContracts
        case NodeType.RefValueExpression:
          return this.VisitRefValueExpression((RefValueExpression)node);
        case NodeType.RefTypeExpression:
          return this.VisitRefTypeExpression((RefTypeExpression)node);
#endif
        case NodeType.Return:
          return this.VisitReturn((Return)node);
#if !MinimalReader && !CodeContracts
        case NodeType.Repeat:
          return this.VisitRepeat((Repeat)node);
        case NodeType.ResourceUse:
          return this.VisitResourceUse((ResourceUse)node);
#endif
        case NodeType.SecurityAttribute:
          return this.VisitSecurityAttribute((SecurityAttribute)node);
#if !MinimalReader && !CodeContracts
        case NodeType.SetterValue:
          return this.VisitSetterValue((SetterValue)node);
        case NodeType.StatementSnippet:
          return this.VisitStatementSnippet((StatementSnippet)node);
#endif
        case NodeType.Struct :
          return this.VisitStruct((Struct)node);
#if !MinimalReader && !CodeContracts
        case NodeType.Switch :
          return this.VisitSwitch((Switch)node);
        case NodeType.SwitchCase :
          return this.VisitSwitchCase((SwitchCase)node);
#endif
        case NodeType.SwitchInstruction :
          return this.VisitSwitchInstruction((SwitchInstruction)node);
#if !MinimalReader && !CodeContracts
        case NodeType.Typeswitch :
          return this.VisitTypeswitch((Typeswitch)node);
        case NodeType.TypeswitchCase :
          return this.VisitTypeswitchCase((TypeswitchCase)node);
#endif
        case NodeType.This :
          return this.VisitThis((This)node);
#if !MinimalReader && !CodeContracts
        case NodeType.Try :
          return this.VisitTry((Try)node);
#endif
#if ExtendedRuntime || CodeContracts
        case NodeType.TypeContract:
          return this.VisitTypeContract((TypeContract)node);
#endif
#if ExtendedRuntime
        case NodeType.TupleType:
          return this.VisitTupleType((TupleType)node);
        case NodeType.TypeAlias:
          return this.VisitTypeAlias((TypeAlias)node);
        case NodeType.TypeIntersection:
          return this.VisitTypeIntersection((TypeIntersection)node);
#endif
#if !MinimalReader && !CodeContracts
        case NodeType.TypeMemberSnippet:
          return this.VisitTypeMemberSnippet((TypeMemberSnippet)node);
#endif
        case NodeType.ClassParameter:
        case NodeType.TypeParameter:
          return this.VisitTypeParameter((TypeNode)node);
#if ExtendedRuntime
        case NodeType.TypeUnion:
          return this.VisitTypeUnion((TypeUnion)node);
#endif
#if !MinimalReader && !CodeContracts
        case NodeType.TypeReference:
          return this.VisitTypeReference((TypeReference)node);
        case NodeType.UsedNamespace :
          return this.VisitUsedNamespace((UsedNamespace)node);
        case NodeType.VariableDeclaration:
          return this.VisitVariableDeclaration((VariableDeclaration)node);
        case NodeType.While:
          return this.VisitWhile((While)node);
        case NodeType.Yield:
          return this.VisitYield((Yield)node);

        case NodeType.Conditional :
#endif
        case NodeType.Cpblk :
        case NodeType.Initblk :
          return this.VisitTernaryExpression((TernaryExpression)node);

        case NodeType.Add : 
        case NodeType.Add_Ovf : 
        case NodeType.Add_Ovf_Un : 
#if !MinimalReader
        case NodeType.AddEventHandler :
#endif
        case NodeType.And : 
#if !MinimalReader
        case NodeType.As :
#endif
        case NodeType.Box :
        case NodeType.Castclass : 
        case NodeType.Ceq : 
        case NodeType.Cgt : 
        case NodeType.Cgt_Un : 
        case NodeType.Clt : 
        case NodeType.Clt_Un : 
#if !MinimalReader
        case NodeType.Comma :
#endif
        case NodeType.Div : 
        case NodeType.Div_Un : 
        case NodeType.Eq : 
#if !MinimalReader
        case NodeType.ExplicitCoercion :
#endif
        case NodeType.Ge : 
        case NodeType.Gt : 
#if !MinimalReader
        case NodeType.Is : 
        case NodeType.Iff : 
        case NodeType.Implies :
#endif
        case NodeType.Isinst : 
        case NodeType.Ldvirtftn :
        case NodeType.Le : 
#if !MinimalReader
        case NodeType.LogicalAnd :
        case NodeType.LogicalOr :
#endif
        case NodeType.Lt : 
        case NodeType.Mkrefany :
#if !MinimalReader
        case NodeType.Maplet : 
#endif
        case NodeType.Mul : 
        case NodeType.Mul_Ovf : 
        case NodeType.Mul_Ovf_Un : 
        case NodeType.Ne : 
        case NodeType.Or : 
#if !MinimalReader
        case NodeType.NullCoalesingExpression:
        case NodeType.Range :
#endif
        case NodeType.Refanyval :
        case NodeType.Rem : 
        case NodeType.Rem_Un : 
#if !MinimalReader
        case NodeType.RemoveEventHandler :
#endif
        case NodeType.Shl : 
        case NodeType.Shr : 
        case NodeType.Shr_Un : 
        case NodeType.Sub : 
        case NodeType.Sub_Ovf : 
        case NodeType.Sub_Ovf_Un : 
        case NodeType.Unbox : 
        case NodeType.UnboxAny :
        case NodeType.Xor : 
          return this.VisitBinaryExpression((BinaryExpression)node);
        
        case NodeType.AddressOf:
#if !MinimalReader
        case NodeType.OutAddress:
        case NodeType.RefAddress:
#endif
        case NodeType.Ckfinite :
        case NodeType.Conv_I :
        case NodeType.Conv_I1 :
        case NodeType.Conv_I2 :
        case NodeType.Conv_I4 :
        case NodeType.Conv_I8 :
        case NodeType.Conv_Ovf_I :
        case NodeType.Conv_Ovf_I1 :
        case NodeType.Conv_Ovf_I1_Un :
        case NodeType.Conv_Ovf_I2 :
        case NodeType.Conv_Ovf_I2_Un :
        case NodeType.Conv_Ovf_I4 :
        case NodeType.Conv_Ovf_I4_Un :
        case NodeType.Conv_Ovf_I8 :
        case NodeType.Conv_Ovf_I8_Un :
        case NodeType.Conv_Ovf_I_Un :
        case NodeType.Conv_Ovf_U :
        case NodeType.Conv_Ovf_U1 :
        case NodeType.Conv_Ovf_U1_Un :
        case NodeType.Conv_Ovf_U2 :
        case NodeType.Conv_Ovf_U2_Un :
        case NodeType.Conv_Ovf_U4 :
        case NodeType.Conv_Ovf_U4_Un :
        case NodeType.Conv_Ovf_U8 :
        case NodeType.Conv_Ovf_U8_Un :
        case NodeType.Conv_Ovf_U_Un :
        case NodeType.Conv_R4 :
        case NodeType.Conv_R8 :
        case NodeType.Conv_R_Un :
        case NodeType.Conv_U :
        case NodeType.Conv_U1 :
        case NodeType.Conv_U2 :
        case NodeType.Conv_U4 :
        case NodeType.Conv_U8 :
#if !MinimalReader
        case NodeType.Decrement :
        case NodeType.DefaultValue :
        case NodeType.Increment :
#endif
        case NodeType.Ldftn :
        case NodeType.Ldlen :
        case NodeType.Ldtoken :
        case NodeType.Localloc :
        case NodeType.LogicalNot :
        case NodeType.Neg :
        case NodeType.Not :
#if !MinimalReader
        case NodeType.Parentheses :
#endif
        case NodeType.Refanytype :
        case NodeType.ReadOnlyAddressOf :
        case NodeType.Sizeof :
        case NodeType.SkipCheck :
#if !MinimalReader
        case NodeType.Typeof :
        case NodeType.UnaryPlus :
#endif
          return this.VisitUnaryExpression((UnaryExpression)node);
#if ExtendedRuntime
          // query node types
        case NodeType.QueryAggregate:
          return this.VisitQueryAggregate((QueryAggregate)node);
        case NodeType.QueryAlias:
          return this.VisitQueryAlias((QueryAlias)node);
        case NodeType.QueryAll:
        case NodeType.QueryAny:
          return this.VisitQueryQuantifier((QueryQuantifier)node);
        case NodeType.QueryAxis:
          return this.VisitQueryAxis((QueryAxis)node);
        case NodeType.QueryCommit:
          return this.VisitQueryCommit((QueryCommit)node);
        case NodeType.QueryContext:
          return this.VisitQueryContext((QueryContext)node);
        case NodeType.QueryDelete:
          return this.VisitQueryDelete((QueryDelete)node);
        case NodeType.QueryDifference:
          return this.VisitQueryDifference((QueryDifference)node);
        case NodeType.QueryDistinct:
          return this.VisitQueryDistinct((QueryDistinct)node);
        case NodeType.QueryExists:
          return this.VisitQueryExists((QueryExists)node);
        case NodeType.QueryFilter:
          return this.VisitQueryFilter((QueryFilter)node);
        case NodeType.QueryGeneratedType:
          return this.VisitQueryGeneratedType((QueryGeneratedType)node);
        case NodeType.QueryGroupBy:
          return this.VisitQueryGroupBy((QueryGroupBy)node);
        case NodeType.QueryInsert:
          return this.VisitQueryInsert((QueryInsert)node);
        case NodeType.QueryIntersection:
          return this.VisitQueryIntersection((QueryIntersection)node);
        case NodeType.QueryIterator:
          return this.VisitQueryIterator((QueryIterator)node);
        case NodeType.QueryJoin:
          return this.VisitQueryJoin((QueryJoin)node);
        case NodeType.QueryLimit:
          return this.VisitQueryLimit((QueryLimit)node);
        case NodeType.QueryOrderBy:        
          return this.VisitQueryOrderBy((QueryOrderBy)node);
        case NodeType.QueryOrderItem:
          return this.VisitQueryOrderItem((QueryOrderItem)node);
        case NodeType.QueryPosition:
          return this.VisitQueryPosition((QueryPosition)node);
        case NodeType.QueryProject:
          return this.VisitQueryProject((QueryProject)node);          
        case NodeType.QueryQuantifiedExpression:
          return this.VisitQueryQuantifiedExpression((QueryQuantifiedExpression)node);
        case NodeType.QueryRollback:
          return this.VisitQueryRollback((QueryRollback)node);
        case NodeType.QuerySelect:
          return this.VisitQuerySelect((QuerySelect)node);
        case NodeType.QuerySingleton:
          return this.VisitQuerySingleton((QuerySingleton)node);
        case NodeType.QueryTransact:
          return this.VisitQueryTransact((QueryTransact)node);
        case NodeType.QueryTypeFilter:
          return this.VisitQueryTypeFilter((QueryTypeFilter)node);
        case NodeType.QueryUnion:
          return this.VisitQueryUnion((QueryUnion)node);
        case NodeType.QueryUpdate:
          return this.VisitQueryUpdate((QueryUpdate)node);
        case NodeType.QueryYielder:
          return this.VisitQueryYielder((QueryYielder)node);
#endif
        default:
          return this.VisitUnknownNodeType(node);
      }
    }
    public virtual Expression VisitAddressDereference(AddressDereference addr){
      if (addr == null) return null;
      addr.Address = this.VisitExpression(addr.Address);
      return addr;
    }
#if !MinimalReader && !CodeContracts
    public virtual AliasDefinition VisitAliasDefinition(AliasDefinition aliasDefinition){
      if (aliasDefinition == null) return null;
      aliasDefinition.AliasedType = this.VisitTypeReference(aliasDefinition.AliasedType);
      return aliasDefinition;
    }
    public virtual AliasDefinitionList VisitAliasDefinitionList(AliasDefinitionList aliasDefinitions){
      if (aliasDefinitions == null) return null;
      for (int i = 0, n = aliasDefinitions.Count; i < n; i++)
        aliasDefinitions[i] = this.VisitAliasDefinition(aliasDefinitions[i]);
      return aliasDefinitions;
    }
    public virtual Expression VisitAnonymousNestedFunction(AnonymousNestedFunction func){
      if (func == null) return null;
      func.Parameters = this.VisitParameterList(func.Parameters);
      func.Body = this.VisitBlock(func.Body);
      return func;
    }
    public virtual Expression VisitApplyToAll(ApplyToAll applyToAll){
      if (applyToAll == null) return null;
      applyToAll.Operand1 = this.VisitExpression(applyToAll.Operand1);
      applyToAll.Operand2 = this.VisitExpression(applyToAll.Operand2);
      return applyToAll;
    } 
    public ArrayType VisitArrayType(ArrayType array){
      Debug.Assert(false, "An array type exists only at runtime. It should be referred to, but never visited.");
      return null;
    }
#endif
    public virtual AssemblyNode VisitAssembly(AssemblyNode assembly){
      if (assembly == null) return null;
      this.VisitModule(assembly);
      assembly.ModuleAttributes = this.VisitAttributeList(assembly.ModuleAttributes);
      assembly.SecurityAttributes = this.VisitSecurityAttributeList(assembly.SecurityAttributes);
      return assembly;
    }
    public virtual AssemblyReference VisitAssemblyReference(AssemblyReference assemblyReference){
      return assemblyReference;
    }
#if !MinimalReader
    public virtual Statement VisitAssertion(Assertion assertion){
      if (assertion == null) return null;
      assertion.Condition = this.VisitExpression(assertion.Condition);
      return assertion;
    }
    public virtual Statement VisitAssumption(Assumption assumption){
      if (assumption == null) return null;
      assumption.Condition = this.VisitExpression(assumption.Condition);
      return assumption;
    }
    public virtual Expression VisitAssignmentExpression(AssignmentExpression assignment){
      if (assignment == null) return null;
      assignment.AssignmentStatement = (Statement)this.Visit(assignment.AssignmentStatement);
      return assignment;
    }
#endif    
    public virtual Statement VisitAssignmentStatement(AssignmentStatement assignment){
      if (assignment == null) return null;
      assignment.Target = this.VisitTargetExpression(assignment.Target);
      assignment.Source = this.VisitExpression(assignment.Source);
      return assignment;
    }
    public virtual Expression VisitAttributeConstructor(AttributeNode attribute){
      if (attribute == null) return null;
      return this.VisitExpression(attribute.Constructor);
    }
    public virtual AttributeNode VisitAttributeNode(AttributeNode attribute){
      if (attribute == null) return null;      
      attribute.Constructor = this.VisitAttributeConstructor(attribute);
      attribute.Expressions = this.VisitExpressionList(attribute.Expressions);
      return attribute;
    }
    public virtual AttributeList VisitAttributeList(AttributeList attributes){
      if (attributes == null) return null;
      for (int i = 0, n = attributes.Count; i < n; i++)
        attributes[i] = this.VisitAttributeNode(attributes[i]);
      return attributes;
    }
#if !MinimalReader && !CodeContracts
    public virtual Expression VisitBase(Base Base){
      return Base;
    }
#endif
    public virtual Expression VisitBinaryExpression(BinaryExpression binaryExpression){
      if (binaryExpression == null) return null;
      binaryExpression.Operand1 = this.VisitExpression(binaryExpression.Operand1);
      binaryExpression.Operand2 = this.VisitExpression(binaryExpression.Operand2);
      return binaryExpression;
    }
    public virtual Block VisitBlock(Block block){
      if (block == null) return null;
      block.Statements = this.VisitStatementList(block.Statements);
      return block;
    }
#if !MinimalReader
    public virtual Expression VisitBlockExpression(BlockExpression blockExpression){
      if (blockExpression == null) return null;
      blockExpression.Block = this.VisitBlock(blockExpression.Block);
      return blockExpression;
    }
#endif
    public virtual BlockList VisitBlockList(BlockList blockList){
      if (blockList == null) return null;
      for (int i = 0, n = blockList.Count; i < n; i++)
        blockList[i] = this.VisitBlock(blockList[i]);
      return blockList;
    }
    public virtual Statement VisitBranch(Branch branch){
      if (branch == null) return null;
      branch.Condition = this.VisitExpression(branch.Condition);
      return branch;
    }
#if !MinimalReader && !CodeContracts
    public virtual Statement VisitCatch(Catch Catch){
      if (Catch == null) return null;
      Catch.Variable = this.VisitTargetExpression(Catch.Variable);
      Catch.Type = this.VisitTypeReference(Catch.Type);
      Catch.Block = this.VisitBlock(Catch.Block);
      return Catch;
    }
    public virtual CatchList VisitCatchList(CatchList catchers){
      if (catchers == null) return null;
      for (int i = 0, n = catchers.Count; i < n; i++)
        catchers[i] = (Catch)this.VisitCatch(catchers[i]);
      return catchers;
    }
#endif
    public virtual Class VisitClass(Class Class){
      return (Class)this.VisitTypeNode(Class);
    }
#if !MinimalReader && !CodeContracts
    public virtual Expression VisitCoerceTuple(CoerceTuple coerceTuple){
      if (coerceTuple == null) return null;
      coerceTuple.OriginalTuple = this.VisitExpression(coerceTuple.OriginalTuple);
      return this.VisitConstructTuple(coerceTuple);
    }
    public virtual CollectionEnumerator VisitCollectionEnumerator(CollectionEnumerator ce){
      if (ce == null) return null;
      ce.Collection = this.VisitExpression(ce.Collection);
      return ce;
    }
    public virtual Compilation VisitCompilation(Compilation compilation){
      if (compilation == null) return null;
      Module module = compilation.TargetModule;
      if (module != null)
        module.Attributes = this.VisitAttributeList(module.Attributes);
      AssemblyNode assem = module as AssemblyNode;
      if (assem != null)
        assem.ModuleAttributes = this.VisitAttributeList(assem.ModuleAttributes);
      compilation.CompilationUnits = this.VisitCompilationUnitList(compilation.CompilationUnits);
      return compilation;
    }
    public virtual CompilationUnit VisitCompilationUnit(CompilationUnit cUnit){
      if (cUnit == null) return null;
      cUnit.Nodes = this.VisitNodeList(cUnit.Nodes);
      return cUnit;
    }    
    public virtual NodeList VisitNodeList(NodeList nodes){
      if (nodes == null) return null;
      for (int i = 0, n = nodes.Count; i < n; i++)
        nodes[i] = this.Visit(nodes[i]);
      return nodes;
    }
    public virtual CompilationUnitList VisitCompilationUnitList(CompilationUnitList compilationUnits){
      if (compilationUnits == null) return null;
      for (int i = 0, n = compilationUnits.Count; i < n; i++)
        compilationUnits[i] = (CompilationUnit)this.Visit(compilationUnits[i]);
      return compilationUnits;
    }
    public virtual CompilationUnit VisitCompilationUnitSnippet(CompilationUnitSnippet snippet){
      return this.VisitCompilationUnit(snippet);
    }
    public virtual Node VisitComposition(Composition comp){
      if (comp == null) return null;
      if (comp.GetType() == typeof(Composition)){
        comp.Expression = (Expression)this.Visit(comp.Expression);
        return comp;
      }
      return this.VisitUnknownNodeType(comp);
    }
#endif
    public virtual Expression VisitConstruct(Construct cons){
      if (cons == null) return null;
      cons.Constructor = this.VisitExpression(cons.Constructor);
      cons.Operands = this.VisitExpressionList(cons.Operands);
#if !MinimalReader
      cons.Owner = this.VisitExpression(cons.Owner);
#endif
      return cons;
    }
    public virtual Expression VisitConstructArray(ConstructArray consArr){
      if (consArr == null) return null;
      consArr.ElementType = this.VisitTypeReference(consArr.ElementType);
      consArr.Operands = this.VisitExpressionList(consArr.Operands);
#if !MinimalReader
      consArr.Initializers = this.VisitExpressionList(consArr.Initializers);
      consArr.Owner = this.VisitExpression(consArr.Owner);
#endif
      return consArr;
    }
#if !MinimalReader && !CodeContracts
    public virtual Expression VisitConstructDelegate(ConstructDelegate consDelegate){
      if (consDelegate == null) return null;
      consDelegate.DelegateType = this.VisitTypeReference(consDelegate.DelegateType);
      consDelegate.TargetObject = this.VisitExpression(consDelegate.TargetObject);
      return consDelegate;
    }
    public virtual Expression VisitConstructFlexArray(ConstructFlexArray consArr){
      if (consArr == null) return null;
      consArr.ElementType = this.VisitTypeReference(consArr.ElementType);
      consArr.Operands = this.VisitExpressionList(consArr.Operands);
      consArr.Initializers = this.VisitExpressionList(consArr.Initializers);
      return consArr;
    }
    public virtual Expression VisitConstructIterator(ConstructIterator consIterator){
      return consIterator;
    }
    public virtual Expression VisitConstructTuple(ConstructTuple consTuple){
      if (consTuple == null) return null;
      consTuple.Fields = this.VisitFieldList(consTuple.Fields);
      return consTuple;
    } 
#endif
#if ExtendedRuntime
    public virtual TypeNode VisitConstrainedType(ConstrainedType cType){
      if (cType == null) return null;
      cType.UnderlyingType = this.VisitTypeReference(cType.UnderlyingType);
      cType.Constraint = this.VisitExpression(cType.Constraint);
      return cType;
    }
#endif
#if !MinimalReader && !CodeContracts
    public virtual Statement VisitContinue(Continue Continue){
      return Continue;
    }
    public virtual Expression VisitCurrentClosure(CurrentClosure currentClosure){
      return currentClosure;
    }
#endif    
    public virtual DelegateNode VisitDelegateNode(DelegateNode delegateNode){
      if (delegateNode == null) return null;
      delegateNode = (DelegateNode)this.VisitTypeNode(delegateNode);
      if (delegateNode == null) return null;
      delegateNode.Parameters = this.VisitParameterList(delegateNode.Parameters);
      delegateNode.ReturnType = this.VisitTypeReference(delegateNode.ReturnType);
      return delegateNode;
    }
#if !MinimalReader && !CodeContracts
    public virtual Statement VisitDoWhile(DoWhile doWhile){
      if (doWhile == null) return null;
      doWhile.Invariants = this.VisitLoopInvariantList(doWhile.Invariants);
      doWhile.Body = this.VisitBlock(doWhile.Body);
      doWhile.Condition = this.VisitExpression(doWhile.Condition);
      return doWhile;
    }
#endif
    public virtual Statement VisitEndFilter(EndFilter endFilter){
      if (endFilter == null) return null;
      endFilter.Value = this.VisitExpression(endFilter.Value);
      return endFilter;
    }
    public virtual Statement VisitEndFinally(EndFinally endFinally){
      return endFinally;
    }
#if ExtendedRuntime || CodeContracts
    public virtual EnsuresList VisitEnsuresList(EnsuresList Ensures) {
      if (Ensures == null) return null;
      for (int i = 0, n = Ensures.Count; i < n; i++)
        Ensures[i] = (Ensures) this.Visit(Ensures[i]);
      return Ensures;
    }
#endif
    public virtual EnumNode VisitEnumNode(EnumNode enumNode) {
      return (EnumNode)this.VisitTypeNode(enumNode);
    }
    public virtual Event VisitEvent(Event evnt){
      if (evnt == null) return null;
      evnt.Attributes = this.VisitAttributeList(evnt.Attributes);
      evnt.HandlerType = this.VisitTypeReference(evnt.HandlerType);
      return evnt;
    }
#if ExtendedRuntime || CodeContracts
    public virtual EnsuresExceptional VisitEnsuresExceptional(EnsuresExceptional exceptional) {
      if (exceptional == null) return null;
      exceptional.PostCondition = this.VisitExpression(exceptional.PostCondition);
      exceptional.Type = this.VisitTypeReference(exceptional.Type);
      exceptional.Variable = this.VisitExpression(exceptional.Variable);
      exceptional.UserMessage = this.VisitExpression(exceptional.UserMessage);
      return exceptional;
    }
#endif
#if !MinimalReader && !CodeContracts
    public virtual Statement VisitExit(Exit exit) {
      return exit;
    }
    public virtual Statement VisitExpose(Expose @expose){
      if (@expose == null) return null;
      @expose.Instance = this.VisitExpression(@expose.Instance);
      @expose.Body = this.VisitBlock(expose.Body);
      return expose;
    }
#endif

    public virtual Expression VisitExpression(Expression expression){
      if (expression == null) return null;
      switch(expression.NodeType){
        case NodeType.Dup: 
        case NodeType.Arglist:
          return expression;
        case NodeType.Pop:
          UnaryExpression uex = expression as UnaryExpression;
          if (uex != null){
            uex.Operand = this.VisitExpression(uex.Operand);
            return uex;
          }
          return expression;
        default:
          return (Expression)this.Visit(expression);
      }
    }
    public override ExpressionList VisitExpressionList(ExpressionList expressions){
      if (expressions == null) return null;
      for (int i = 0, n = expressions.Count; i < n; i++)
        expressions[i] = this.VisitExpression(expressions[i]);
      return expressions;
    }
#if !MinimalReader && !CodeContracts
    public virtual Expression VisitExpressionSnippet(ExpressionSnippet snippet){
      return snippet;
    }
#endif    
    public virtual Statement VisitExpressionStatement(ExpressionStatement statement){
      if (statement == null) return null;
      statement.Expression = this.VisitExpression(statement.Expression);
      return statement;
    }
#if !MinimalReader
    public virtual Statement VisitFaultHandler(FaultHandler faultHandler){
      if (faultHandler == null) return null;
      faultHandler.Block = this.VisitBlock(faultHandler.Block);
      return faultHandler;
    }
    public virtual FaultHandlerList VisitFaultHandlerList(FaultHandlerList faultHandlers){
      if (faultHandlers == null) return null;
      for (int i = 0, n = faultHandlers.Count; i < n; i++)
        faultHandlers[i] = (FaultHandler)this.VisitFaultHandler(faultHandlers[i]);
      return faultHandlers;
    }
#endif
    public virtual Field VisitField(Field field){
      if (field == null) return null;
      field.Attributes = this.VisitAttributeList(field.Attributes);
      field.Type = this.VisitTypeReference(field.Type);
#if !MinimalReader
      field.Initializer = this.VisitExpression(field.Initializer);
      field.ImplementedInterfaces = this.VisitInterfaceReferenceList(field.ImplementedInterfaces);
#endif
      return field;
    }
#if !MinimalReader && !CodeContracts
    public virtual Block VisitFieldInitializerBlock(FieldInitializerBlock block){
      if (block == null) return null;
      block.Type = this.VisitTypeReference(block.Type);
      return this.VisitBlock(block);
    }
    public virtual FieldList VisitFieldList(FieldList fields){
      if (fields == null) return null;
      for (int i = 0, n = fields.Count; i < n; i++)
        fields[i] = this.VisitField(fields[i]);
      return fields;
    }
    public virtual Statement VisitFilter(Filter filter){
      if (filter == null) return null;
      filter.Expression = this.VisitExpression(filter.Expression);
      filter.Block = this.VisitBlock(filter.Block);
      return filter;
    }
    public virtual FilterList VisitFilterList(FilterList filters){
      if (filters == null) return null;
      for (int i = 0, n = filters.Count; i < n; i++)
        filters[i] = (Filter)this.VisitFilter(filters[i]);
      return filters;
    }
    public virtual Statement VisitFinally(Finally Finally){
      if (Finally == null) return null;
      Finally.Block = this.VisitBlock(Finally.Block);
      return Finally;
    }
    public virtual Statement VisitFixed(Fixed Fixed){
      if (Fixed == null) return null;
      Fixed.Declarators = (Statement)this.Visit(Fixed.Declarators);
      Fixed.Body = this.VisitBlock(Fixed.Body);
      return Fixed;
    }
    public virtual Statement VisitFor(For For){
      if (For == null) return null;
      For.Initializer = this.VisitStatementList(For.Initializer);
      For.Invariants = this.VisitLoopInvariantList(For.Invariants);
      For.Condition = this.VisitExpression(For.Condition);
      For.Incrementer = this.VisitStatementList(For.Incrementer);
      For.Body = this.VisitBlock(For.Body);
      return For;
    }
    public virtual Statement VisitForEach(ForEach forEach){
      if (forEach == null) return null;
      forEach.TargetVariableType = this.VisitTypeReference(forEach.TargetVariableType);
      forEach.TargetVariable = this.VisitTargetExpression(forEach.TargetVariable);
      forEach.SourceEnumerable = this.VisitExpression(forEach.SourceEnumerable);
      forEach.InductionVariable = this.VisitTargetExpression(forEach.InductionVariable);
      forEach.Invariants = this.VisitLoopInvariantList(forEach.Invariants);
      forEach.Body = this.VisitBlock(forEach.Body);
      return forEach;
    }
    public virtual Statement VisitFunctionDeclaration(FunctionDeclaration functionDeclaration){
      if (functionDeclaration == null) return null;
      functionDeclaration.Parameters = this.VisitParameterList(functionDeclaration.Parameters);
      functionDeclaration.ReturnType = this.VisitTypeReference(functionDeclaration.ReturnType);
      functionDeclaration.Body = this.VisitBlock(functionDeclaration.Body);
      return functionDeclaration;
    }
    public virtual Expression VisitTemplateInstance(TemplateInstance templateInstance){
      if (templateInstance == null) return null;
      templateInstance.Expression = this.VisitExpression(templateInstance.Expression);
      templateInstance.TypeArguments = this.VisitTypeReferenceList(templateInstance.TypeArguments);
      return templateInstance;
    }
    public virtual Expression VisitStackAlloc(StackAlloc alloc){
      if (alloc == null) return null;
      alloc.ElementType = this.VisitTypeReference(alloc.ElementType);
      alloc.NumberOfElements = this.VisitExpression(alloc.NumberOfElements);
      return alloc;
    }
    public virtual Statement VisitGoto(Goto Goto){
      return Goto;
    }
    public virtual Statement VisitGotoCase(GotoCase gotoCase){
      if (gotoCase == null) return null;
      gotoCase.CaseLabel = this.VisitExpression(gotoCase.CaseLabel);
      return gotoCase;
    }
#endif
    public virtual Expression VisitIdentifier(Identifier identifier){
      return identifier;
    }
#if !MinimalReader && !CodeContracts
    public virtual Statement VisitIf(If If){
      if (If == null) return null;
      If.Condition = this.VisitExpression(If.Condition);
      If.TrueBlock = this.VisitBlock(If.TrueBlock);
      If.FalseBlock = this.VisitBlock(If.FalseBlock);
      return If;
    }
    public virtual Expression VisitImplicitThis(ImplicitThis implicitThis){
      return implicitThis;
    }
#endif    
    public virtual Expression VisitIndexer(Indexer indexer){
      if (indexer == null) return null;
      indexer.Object = this.VisitExpression(indexer.Object);
      indexer.Operands = this.VisitExpressionList(indexer.Operands);
      return indexer;
    }
    public virtual Interface VisitInterface(Interface Interface){
      return (Interface)this.VisitTypeNode(Interface);
    }
    public virtual Interface VisitInterfaceReference(Interface Interface){
      return (Interface)this.VisitTypeReference(Interface);
    }
    public virtual InterfaceList VisitInterfaceReferenceList(InterfaceList interfaceReferences){
      if (interfaceReferences == null) return null;
      for (int i = 0, n = interfaceReferences.Count; i < n; i++)
        interfaceReferences[i] = this.VisitInterfaceReference(interfaceReferences[i]);
      return interfaceReferences;
    }
#if ExtendedRuntime || CodeContracts
    public virtual Invariant VisitInvariant(Invariant @invariant){
      if (@invariant == null) return null;
      @invariant.Condition = VisitExpression(@invariant.Condition);
      return @invariant;
    }
    public virtual InvariantList VisitInvariantList(InvariantList invariants){
      if (invariants == null) return null;
      for (int i = 0, n = invariants.Count; i < n; i++)
        invariants[i] = this.VisitInvariant(invariants[i]);
      return invariants;
    }
#endif
#if ExtendedRuntime
    public virtual ModelfieldContract VisitModelfieldContract(ModelfieldContract mfC) {
      if (mfC == null) return null;
      mfC.Witness = this.VisitExpression(mfC.Witness);
      for (int i = 0, n = mfC.SatisfiesList.Count; i < n; i++)
        mfC.SatisfiesList[i] = this.VisitExpression(mfC.SatisfiesList[i]);
      return mfC;
    }
    public virtual ModelfieldContractList VisitModelfieldContractList(ModelfieldContractList mfCs) {
      if (mfCs == null) return null;
      for (int i = 0, n = mfCs.Count; i < n; i++)
        mfCs[i] = this.VisitModelfieldContract(mfCs[i]);
      return mfCs;
    }
#endif
    public virtual InstanceInitializer VisitInstanceInitializer(InstanceInitializer cons){
      return (InstanceInitializer)this.VisitMethod(cons);
    }
#if !MinimalReader
    public virtual Statement VisitLabeledStatement(LabeledStatement lStatement){
      if (lStatement == null) return null;
      lStatement.Statement = (Statement)this.Visit(lStatement.Statement);
      return lStatement;
    }
#endif
    public virtual Expression VisitLiteral(Literal literal){
      return literal;
    }
    public virtual Expression VisitLocal(Local local){
      if (local == null) return null;
      local.Type = this.VisitTypeReference(local.Type);
#if !MinimalReader
      LocalBinding lb = local as LocalBinding;
      if (lb != null) {
        Local loc = this.VisitLocal(lb.BoundLocal) as Local;
        if (loc != null)
          lb.BoundLocal = loc;
      }
#endif
      return local;
    }
#if !MinimalReader && !CodeContracts
    public virtual Statement VisitLocalDeclarationsStatement(LocalDeclarationsStatement localDeclarations){
      if (localDeclarations == null) return null;
      localDeclarations.Type = this.VisitTypeReference(localDeclarations.Type);
      localDeclarations.Declarations = this.VisitLocalDeclarationList(localDeclarations.Declarations);
      return localDeclarations;
    }
    public virtual LocalDeclarationList VisitLocalDeclarationList(LocalDeclarationList localDeclarations){
      if (localDeclarations == null) return null;
      for (int i = 0, n = localDeclarations.Count; i < n; i++)
        localDeclarations[i] = this.VisitLocalDeclaration(localDeclarations[i]);
      return localDeclarations;
    }
    public virtual LocalDeclaration VisitLocalDeclaration(LocalDeclaration localDeclaration){
      if (localDeclaration == null) return null;
      localDeclaration.InitialValue = this.VisitExpression(localDeclaration.InitialValue);
      return localDeclaration;
    }
    public virtual Statement VisitLock(Lock Lock){
      if (Lock == null) return null;
      Lock.Guard = this.VisitExpression(Lock.Guard);
      Lock.Body = this.VisitBlock(Lock.Body);
      return Lock;
    }
    public virtual Expression VisitLRExpression(LRExpression expr){
      if (expr == null) return null;
      expr.Expression = this.VisitExpression(expr.Expression);
      return expr;
    }
#endif    
    public virtual Expression VisitMemberBinding(MemberBinding memberBinding){
      if (memberBinding == null) return null;
      memberBinding.TargetObject = this.VisitExpression(memberBinding.TargetObject);
      return memberBinding;
    }
    public virtual MemberList VisitMemberList(MemberList members){
      this.memberListNamesChanged = false;
      if (members == null) return null;
      for (int i = 0, n = members.Count; i < n; i++) {
        Member oldm = members[i];
        if (oldm != null) {
          Identifier oldId = oldm.Name;
          members[i] = (Member)this.Visit(oldm);
          if (members[i] != null) {
            if (oldId != null && members[i].Name != null && members[i].Name.UniqueIdKey != oldId.UniqueIdKey) {
              this.memberListNamesChanged = true;
            }
          }
        }
      }
      return members;
    }
    public virtual Method VisitMethod(Method method){
      if (method == null) return null;
      method.Attributes = this.VisitAttributeList(method.Attributes);
      method.ReturnAttributes = this.VisitAttributeList(method.ReturnAttributes);
      method.SecurityAttributes = this.VisitSecurityAttributeList(method.SecurityAttributes);
      method.ReturnType = this.VisitTypeReference(method.ReturnType);
#if !MinimalReader && !CodeContracts
      method.ImplementedTypes = this.VisitTypeReferenceList(method.ImplementedTypes);
#endif
      method.Parameters = this.VisitParameterList(method.Parameters);
      if (TargetPlatform.UseGenerics) {
        method.TemplateArguments = this.VisitTypeReferenceList(method.TemplateArguments);
        method.TemplateParameters = this.VisitTypeParameterList(method.TemplateParameters);
      }
#if ExtendedRuntime || CodeContracts
      method.Contract = this.VisitMethodContract(method.Contract);
#endif
      method.Body = this.VisitBlock(method.Body);
      return method;
    }
    public virtual Expression VisitMethodCall(MethodCall call){
      if (call == null) return null;
      call.Callee = this.VisitExpression(call.Callee);
      call.Operands = this.VisitExpressionList(call.Operands);
      call.Constraint = this.VisitTypeReference(call.Constraint);
      return call;
    }
#if !MinimalReader
    public virtual Expression VisitArglistArgumentExpression(ArglistArgumentExpression argexp){
      if (argexp == null) return null;
      argexp.Operands = this.VisitExpressionList(argexp.Operands);
      return argexp;
    }
    public virtual Expression VisitArglistExpression(ArglistExpression argexp){
      if (argexp == null) return null;
      return argexp;
    }
#endif
#if ExtendedRuntime || CodeContracts
    public virtual MethodContract VisitMethodContract(MethodContract contract){
      if (contract == null) return null;
      // don't visit contract.DeclaringMethod
      // don't visit contract.OverriddenMethods
      contract.Requires = this.VisitRequiresList(contract.Requires);
      contract.Ensures = this.VisitEnsuresList(contract.Ensures);
      contract.AsyncEnsures = this.VisitEnsuresList(contract.AsyncEnsures);
      contract.ModelEnsures = this.VisitEnsuresList(contract.ModelEnsures);
      contract.Modifies = this.VisitExpressionList(contract.Modifies);
      return contract;
    }
#endif
    public virtual Module VisitModule(Module module){
      if (module == null) return null;
      module.Attributes = this.VisitAttributeList(module.Attributes);
      module.Types = this.VisitTypeNodeList(module.Types);
      return module;
    }
    public virtual ModuleReference VisitModuleReference(ModuleReference moduleReference){
      return moduleReference;
    }
#if !MinimalReader && !CodeContracts
    public virtual Expression VisitNameBinding(NameBinding nameBinding){
      return nameBinding;
    }
#endif
    public virtual Expression VisitNamedArgument(NamedArgument namedArgument){
      if (namedArgument == null) return null;
      namedArgument.Value = this.VisitExpression(namedArgument.Value);
      return namedArgument;
    }
#if !MinimalReader && !CodeContracts
    public virtual Namespace VisitNamespace(Namespace nspace){
      if (nspace == null) return null;
      nspace.AliasDefinitions = this.VisitAliasDefinitionList(nspace.AliasDefinitions);
      nspace.UsedNamespaces = this.VisitUsedNamespaceList(nspace.UsedNamespaces);
      nspace.Attributes = this.VisitAttributeList(nspace.Attributes);
      nspace.Types = this.VisitTypeNodeList(nspace.Types);
      nspace.NestedNamespaces = this.VisitNamespaceList(nspace.NestedNamespaces);
      return nspace;
    }
    public virtual NamespaceList VisitNamespaceList(NamespaceList namespaces){
      if (namespaces == null) return null;
      for (int i = 0, n = namespaces.Count; i < n; i++)
        namespaces[i] = this.VisitNamespace(namespaces[i]);
      return namespaces;
    }
#endif
#if ExtendedRuntime || CodeContracts
    public virtual EnsuresNormal VisitEnsuresNormal(EnsuresNormal normal) {
      if (normal == null) return null;
      normal.PostCondition = this.VisitExpression(normal.PostCondition);
      normal.UserMessage = this.VisitExpression(normal.UserMessage);
      return normal;
    }
    public virtual Expression VisitOldExpression (OldExpression oldExpression) {
      if (oldExpression == null) return null;
      oldExpression.expression = this.VisitExpression(oldExpression.expression);
      return oldExpression;
    }
    public virtual Expression VisitReturnValue(ReturnValue returnValue)
    {
      if (returnValue == null) return null;
      returnValue.Type = this.VisitTypeReference(returnValue.Type);
      return returnValue;
    }
    public virtual RequiresOtherwise VisitRequiresOtherwise(RequiresOtherwise otherwise) {
      if (otherwise == null) return null;
      otherwise.Condition = this.VisitExpression(otherwise.Condition);
      otherwise.ThrowException = this.VisitExpression(otherwise.ThrowException);
      otherwise.UserMessage = VisitExpression(otherwise.UserMessage);
      return otherwise;
    }
    public virtual RequiresPlain VisitRequiresPlain(RequiresPlain plain) {
      if (plain == null) return null;
      plain.Condition = this.VisitExpression(plain.Condition);
      plain.UserMessage = this.VisitExpression(plain.UserMessage);
      plain.ExceptionType = this.VisitTypeReference(plain.ExceptionType);
      return plain;
    }
#endif
    public virtual Expression VisitParameter(Parameter parameter){
      if (parameter == null) return null;
      parameter.Attributes = this.VisitAttributeList(parameter.Attributes);
      parameter.Type = this.VisitTypeReference(parameter.Type);
      parameter.DefaultValue = this.VisitExpression(parameter.DefaultValue);
#if !MinimalReader
      ParameterBinding pb = parameter as ParameterBinding;
      if (pb != null) {
        Parameter par = this.VisitParameter(pb.BoundParameter) as Parameter;
        if (par != null)
          pb.BoundParameter = par;
      }
#endif
      return parameter;
    }
    public virtual ParameterList VisitParameterList(ParameterList parameterList){
      if (parameterList == null) return null;
      for (int i = 0, n = parameterList.Count; i < n; i++)
        parameterList[i] = (Parameter)this.VisitParameter(parameterList[i]);
      return parameterList;
    }
#if !MinimalReader
    public virtual Expression VisitPrefixExpression(PrefixExpression pExpr) {
      if (pExpr == null) return null;
      pExpr.Expression = this.VisitExpression(pExpr.Expression);
      return pExpr;
    }
    public virtual Expression VisitPostfixExpression(PostfixExpression pExpr){
      if (pExpr == null) return null;
      pExpr.Expression = this.VisitExpression(pExpr.Expression);
      return pExpr;
    }
#endif    
    public virtual Property VisitProperty(Property property){
      if (property == null) return null;
      property.Attributes = this.VisitAttributeList(property.Attributes);
      property.Parameters = this.VisitParameterList(property.Parameters);
      property.Type = this.VisitTypeReference(property.Type);
      return property;
    }
#if !MinimalReader && !CodeContracts
    public virtual Expression VisitQuantifier(Quantifier quantifier){
      if (quantifier == null) return null;
      quantifier.Comprehension = (Comprehension)this.VisitComprehension(quantifier.Comprehension);
      return quantifier;
    }
    public virtual Expression VisitComprehension(Comprehension comprehension){
      if (comprehension == null) return null;
      comprehension.BindingsAndFilters = this.VisitExpressionList(comprehension.BindingsAndFilters);
      comprehension.Elements = this.VisitExpressionList(comprehension.Elements);
      return comprehension;
    }
    public virtual ComprehensionBinding VisitComprehensionBinding(ComprehensionBinding comprehensionBinding){
      if (comprehensionBinding == null) return null;
      comprehensionBinding.TargetVariableType = this.VisitTypeReference(comprehensionBinding.TargetVariableType);
      comprehensionBinding.TargetVariable = this.VisitTargetExpression(comprehensionBinding.TargetVariable);
      comprehensionBinding.AsTargetVariableType = this.VisitTypeReference(comprehensionBinding.AsTargetVariableType);
      comprehensionBinding.SourceEnumerable = this.VisitExpression(comprehensionBinding.SourceEnumerable);
      return comprehensionBinding;
    }
    public virtual Expression VisitQualifiedIdentifier(QualifiedIdentifier qualifiedIdentifier){
      if (qualifiedIdentifier == null) return null;
      qualifiedIdentifier.Qualifier = this.VisitExpression(qualifiedIdentifier.Qualifier);
      return qualifiedIdentifier;
    }
    public virtual Expression VisitRefValueExpression(RefValueExpression refvalexp) {
      if (refvalexp == null) return null;
      refvalexp.Operand1 = this.VisitExpression(refvalexp.Operand1);
      refvalexp.Operand2 = this.VisitExpression(refvalexp.Operand2);
      return refvalexp;
    }
    public virtual Expression VisitRefTypeExpression(RefTypeExpression reftypexp) {
      if (reftypexp == null) return null;
      reftypexp.Operand = this.VisitExpression(reftypexp.Operand);
      return reftypexp;
    }
    public virtual Statement VisitRepeat(Repeat repeat){
      if (repeat == null) return null;
      repeat.Body = this.VisitBlock(repeat.Body);
      repeat.Condition = this.VisitExpression(repeat.Condition);
      return repeat;
    }
#endif
#if ExtendedRuntime || CodeContracts
    public virtual RequiresList VisitRequiresList(RequiresList Requires) {
      if (Requires == null) return null;
      for (int i = 0, n = Requires.Count; i < n; i++)
        Requires[i] = (Requires) this.Visit(Requires[i]);
      return Requires;
    }
#endif
    public virtual Statement VisitReturn(Return Return) {
      if (Return == null) return null;
      Return.Expression = this.VisitExpression(Return.Expression);
      return Return;
    }
#if !MinimalReader && !CodeContracts
    public virtual Statement VisitAcquire(Acquire @acquire){
      if (@acquire == null) return null;
      @acquire.Target = (Statement)this.Visit(@acquire.Target);
      @acquire.Condition = this.VisitExpression(@acquire.Condition);
      @acquire.ConditionFunction = this.VisitExpression(@acquire.ConditionFunction);
      @acquire.Body = this.VisitBlock(@acquire.Body);
      return @acquire;
    }
    public virtual Statement VisitResourceUse(ResourceUse resourceUse){
      if (resourceUse == null) return null;
      resourceUse.ResourceAcquisition = (Statement)this.Visit(resourceUse.ResourceAcquisition);
      resourceUse.Body = this.VisitBlock(resourceUse.Body);
      return resourceUse;
    }
#endif
    public virtual SecurityAttribute VisitSecurityAttribute(SecurityAttribute attribute){
      return attribute;
    }
    public virtual SecurityAttributeList VisitSecurityAttributeList(SecurityAttributeList attributes){
      if (attributes == null) return null;
      for (int i = 0, n = attributes.Count; i < n; i++)
        attributes[i] = this.VisitSecurityAttribute(attributes[i]);
      return attributes;
    }
 #if !MinimalReader && !CodeContracts
    public virtual Expression VisitSetterValue(SetterValue value){
      return value;
    }
#endif
    public virtual StatementList VisitStatementList(StatementList statements){
      if (statements == null) return null;
      for (int i = 0, n = statements.Count; i < n; i++)
        statements[i] = (Statement)this.Visit(statements[i]);
      return statements;
    }
#if !MinimalReader && !CodeContracts
    public virtual StatementSnippet VisitStatementSnippet(StatementSnippet snippet){
      return snippet;
    }
#endif
    public virtual StaticInitializer VisitStaticInitializer(StaticInitializer cons){
      return (StaticInitializer)this.VisitMethod(cons);
    }
    public virtual Struct VisitStruct(Struct Struct){
      return (Struct)this.VisitTypeNode(Struct);
    }
#if !MinimalReader && !CodeContracts
    public virtual Statement VisitSwitch(Switch Switch){
      if (Switch == null) return null;
      Switch.Expression = this.VisitExpression(Switch.Expression);
      Switch.Cases = this.VisitSwitchCaseList(Switch.Cases);
      return Switch;
    }
    public virtual SwitchCase VisitSwitchCase(SwitchCase switchCase){
      if (switchCase == null) return null;
      switchCase.Label = this.VisitExpression(switchCase.Label);
      switchCase.Body = this.VisitBlock(switchCase.Body);
      return switchCase;
    }
    public virtual SwitchCaseList VisitSwitchCaseList(SwitchCaseList switchCases){
      if (switchCases == null) return null;
      for (int i = 0, n = switchCases.Count; i < n; i++)
        switchCases[i] = this.Visit(switchCases[i]) as SwitchCase;
      return switchCases;
    }
#endif
    public virtual Statement VisitSwitchInstruction(SwitchInstruction switchInstruction){
      if (switchInstruction == null) return null;
      switchInstruction.Expression = this.VisitExpression(switchInstruction.Expression);
      return switchInstruction;
    }
#if !MinimalReader && !CodeContracts
    public virtual Statement VisitTypeswitch(Typeswitch Typeswitch){
      if (Typeswitch == null) return null;
      Typeswitch.Expression = this.VisitExpression(Typeswitch.Expression);
      Typeswitch.Cases = this.VisitTypeswitchCaseList(Typeswitch.Cases);
      return Typeswitch;
    }
    public virtual TypeswitchCase VisitTypeswitchCase(TypeswitchCase typeswitchCase){
      if (typeswitchCase == null) return null;
      typeswitchCase.LabelType = this.VisitTypeReference(typeswitchCase.LabelType);
      typeswitchCase.LabelVariable = this.VisitTargetExpression(typeswitchCase.LabelVariable);
      typeswitchCase.Body = this.VisitBlock(typeswitchCase.Body);
      return typeswitchCase;
    }
    public virtual TypeswitchCaseList VisitTypeswitchCaseList(TypeswitchCaseList typeswitchCases){
      if (typeswitchCases == null) return null;
      for (int i = 0, n = typeswitchCases.Count; i < n; i++)
        typeswitchCases[i] = this.VisitTypeswitchCase(typeswitchCases[i]);
      return typeswitchCases;
    } 
#endif
    public virtual Expression VisitTargetExpression(Expression expression){
      return this.VisitExpression(expression);
    }
    public virtual Expression VisitTernaryExpression(TernaryExpression expression){
      if (expression == null) return null;
      expression.Operand1 = this.VisitExpression(expression.Operand1);
      expression.Operand2 = this.VisitExpression(expression.Operand2);
      expression.Operand3 = this.VisitExpression(expression.Operand3);
      return expression;
    }
    public virtual Expression VisitThis(This This){
      if (This == null) return null;
      This.Type = this.VisitTypeReference(This.Type);
#if !MinimalReader && !CodeContracts
      ThisBinding tb = This as ThisBinding;
      if (tb != null) {
        This boundThis = this.VisitThis(tb.BoundThis) as This;
        if (boundThis != null)
          tb.BoundThis = boundThis;
      }
#endif
      return This;
    }
    public virtual Statement VisitThrow(Throw Throw){
      if (Throw == null) return null;
      Throw.Expression = this.VisitExpression(Throw.Expression);
      return Throw;
    }
#if !MinimalReader && !CodeContracts
    public virtual Statement VisitTry(Try Try){
      if (Try == null) return null;
      Try.TryBlock = this.VisitBlock(Try.TryBlock);
      Try.Catchers = this.VisitCatchList(Try.Catchers);
      Try.Filters = this.VisitFilterList(Try.Filters);
      Try.FaultHandlers = this.VisitFaultHandlerList(Try.FaultHandlers);
      Try.Finally = (Finally)this.VisitFinally(Try.Finally);
      return Try;
    }
#endif
#if ExtendedRuntime    
    public virtual TupleType VisitTupleType(TupleType tuple){
      return (TupleType)this.VisitTypeNode(tuple);
    }
    public virtual TypeAlias VisitTypeAlias(TypeAlias tAlias){
      if (tAlias == null) return null;
      if (tAlias.AliasedType is ConstrainedType)
        //The type alias defines the constrained type, rather than just referencing it
        tAlias.AliasedType = this.VisitConstrainedType((ConstrainedType)tAlias.AliasedType);
      else
        tAlias.AliasedType = this.VisitTypeReference(tAlias.AliasedType);
      return tAlias;
    }

    public virtual TypeIntersection VisitTypeIntersection(TypeIntersection typeIntersection){
      return (TypeIntersection)this.VisitTypeNode(typeIntersection);
    }
#endif
#if ExtendedRuntime || CodeContracts
    public virtual TypeContract VisitTypeContract(TypeContract contract){
      if (contract == null) return null;
      // don't visit contract.DeclaringType
      // don't visit contract.InheritedContracts
      contract.Invariants = this.VisitInvariantList(contract.Invariants);
#if ExtendedRuntime
      contract.ModelfieldContracts = this.VisitModelfieldContractList(contract.ModelfieldContracts);
#endif
      return contract;
    }
#endif
#if !MinimalReader && !CodeContracts
    public virtual TypeMemberSnippet VisitTypeMemberSnippet(TypeMemberSnippet snippet){
      return snippet;
    }
#endif
    public virtual TypeModifier VisitTypeModifier(TypeModifier typeModifier){
      if (typeModifier == null) return null;
      typeModifier.Modifier = this.VisitTypeReference(typeModifier.Modifier);
      typeModifier.ModifiedType = this.VisitTypeReference(typeModifier.ModifiedType);
      return typeModifier;
    }
    public virtual TypeNode VisitTypeNode(TypeNode typeNode){
      if (typeNode == null) return null;
      typeNode.Attributes = this.VisitAttributeList(typeNode.Attributes);
      typeNode.SecurityAttributes = this.VisitSecurityAttributeList(typeNode.SecurityAttributes);
      Class c = typeNode as Class;
      if (c != null) c.BaseClass = (Class)this.VisitTypeReference(c.BaseClass);
      typeNode.Interfaces = this.VisitInterfaceReferenceList(typeNode.Interfaces);
      typeNode.TemplateArguments = this.VisitTypeReferenceList(typeNode.TemplateArguments);
      typeNode.TemplateParameters = this.VisitTypeParameterList(typeNode.TemplateParameters);
      this.VisitMemberList(typeNode.Members);
      if (this.memberListNamesChanged) { typeNode.ClearMemberTable(); }
#if ExtendedRuntime || CodeContracts
      // have to visit this *after* visiting the members since in Normalizer
      // it creates normalized method bodies for the invariant methods and
      // those shouldn't be visited again!!
      // REVIEW!! I don't think the method bodies created in Normalizer are necessarily normalized anymore!!
      typeNode.Contract = this.VisitTypeContract(typeNode.Contract);
#endif
      return typeNode;
    }
    public virtual TypeNodeList VisitTypeNodeList(TypeNodeList types){
      if (types == null) return null;
      for (int i = 0; i < types.Count; i++) //Visiting a type may result in a new type being appended to this list
        types[i] = (TypeNode)this.Visit(types[i]);
      return types;
    }
    public virtual TypeNode VisitTypeParameter(TypeNode typeParameter){
      if (typeParameter == null) return null;
      Class cl = typeParameter as Class;
      if (cl != null) cl.BaseClass = (Class)this.VisitTypeReference(cl.BaseClass);
      typeParameter.Attributes = this.VisitAttributeList(typeParameter.Attributes);
      typeParameter.Interfaces = this.VisitInterfaceReferenceList(typeParameter.Interfaces);
      return typeParameter;
    }
    public virtual TypeNodeList VisitTypeParameterList(TypeNodeList typeParameters){
      if (typeParameters == null) return null;
      for (int i = 0, n = typeParameters.Count; i < n; i++)
        typeParameters[i] = this.VisitTypeParameter(typeParameters[i]);
      return typeParameters;
    }
    public virtual TypeNode VisitTypeReference(TypeNode type){
      return type;
    }
#if !MinimalReader
    public virtual TypeReference VisitTypeReference(TypeReference type){
      return type;
    }
#endif
    public virtual TypeNodeList VisitTypeReferenceList(TypeNodeList typeReferences){
      if (typeReferences == null) return null;
      for (int i = 0, n = typeReferences.Count; i < n; i++)
        typeReferences[i] = this.VisitTypeReference(typeReferences[i]);
      return typeReferences;
    } 
#if ExtendedRuntime 
    public virtual TypeUnion VisitTypeUnion(TypeUnion typeUnion){
      return (TypeUnion)this.VisitTypeNode(typeUnion);
    }
#endif
    public virtual Expression VisitUnaryExpression(UnaryExpression unaryExpression){
      if (unaryExpression == null) return null;
      unaryExpression.Operand = this.VisitExpression(unaryExpression.Operand);
      return unaryExpression;
    }
#if !MinimalReader && !CodeContracts
    public virtual Statement VisitVariableDeclaration(VariableDeclaration variableDeclaration){
      if (variableDeclaration == null) return null;
      variableDeclaration.Type = this.VisitTypeReference(variableDeclaration.Type);
      variableDeclaration.Initializer = this.VisitExpression(variableDeclaration.Initializer);
      return variableDeclaration;
    }
    public virtual UsedNamespace VisitUsedNamespace(UsedNamespace usedNamespace){
      return usedNamespace;
    }
    public virtual UsedNamespaceList VisitUsedNamespaceList(UsedNamespaceList usedNspaces){
      if (usedNspaces == null) return null;
      for (int i = 0, n = usedNspaces.Count; i < n; i++)
        usedNspaces[i] = this.VisitUsedNamespace(usedNspaces[i]);
      return usedNspaces;
    }
    public virtual ExpressionList VisitLoopInvariantList(ExpressionList expressions){
      if (expressions == null) return null;
      for (int i = 0, n = expressions.Count; i < n; i++)
        expressions[i] = this.VisitExpression(expressions[i]);
      return expressions;
    }
    public virtual Statement VisitWhile(While While){
      if (While == null) return null;
      While.Condition = this.VisitExpression(While.Condition);
      While.Invariants = this.VisitLoopInvariantList(While.Invariants);
      While.Body = this.VisitBlock(While.Body);
      return While;
    }
    public virtual Statement VisitYield(Yield Yield){
      if (Yield == null) return null;
      Yield.Expression = this.VisitExpression(Yield.Expression);
      return Yield;
    }
#endif
#if ExtendedRuntime
    // query nodes
    public virtual Node VisitQueryAggregate(QueryAggregate qa){
      if (qa == null) return null;
      qa.Expression = this.VisitExpression(qa.Expression);
      return qa;
    }
    public virtual Node VisitQueryAlias(QueryAlias alias){
      if (alias == null) return null;
      alias.Expression = this.VisitExpression(alias.Expression);
      return alias;
    }
    public virtual Node VisitQueryAxis(QueryAxis axis){
      if (axis == null) return null;
      axis.Source = this.VisitExpression( axis.Source );
      return axis;
    }
    public virtual Node VisitQueryCommit(QueryCommit qc){
      return qc;
    }
    public virtual Node VisitQueryContext(QueryContext context){
      return context;
    }
    public virtual Node VisitQueryDelete(QueryDelete delete){
      if (delete == null) return null;
      delete.Source = this.VisitExpression(delete.Source);
      /*delete.Target =*/ this.VisitExpression(delete.Target); //REVIEW: why should this not be updated?
      return delete;
    }
    public virtual Node VisitQueryDifference(QueryDifference diff){
      if (diff == null) return null;
      diff.LeftSource = this.VisitExpression(diff.LeftSource);
      diff.RightSource = this.VisitExpression(diff.RightSource);
      return diff;
    }
    public virtual Node VisitQueryDistinct(QueryDistinct distinct){
      if (distinct == null) return null;
      distinct.Source = this.VisitExpression(distinct.Source);
      return distinct;
    }
    public virtual Node VisitQueryExists(QueryExists exists){
      if (exists == null) return null;
      exists.Source = this.VisitExpression(exists.Source);
      return exists;
    }
    public virtual Node VisitQueryFilter(QueryFilter filter){
      if (filter == null) return null;
      filter.Source = this.VisitExpression(filter.Source);
      filter.Expression = this.VisitExpression(filter.Expression);
      return filter;
    }
    public virtual Node VisitQueryGroupBy(QueryGroupBy groupby){
      if (groupby == null) return null;
      groupby.Source = this.VisitExpression(groupby.Source);
      groupby.GroupList = this.VisitExpressionList(groupby.GroupList);
      groupby.Having = this.VisitExpression(groupby.Having);
      return groupby;
    }
    public virtual Statement VisitQueryGeneratedType(QueryGeneratedType qgt){
      return qgt;
    }
    public virtual Node VisitQueryInsert(QueryInsert insert){
      if (insert == null) return null;
      insert.Location = this.VisitExpression(insert.Location);
      insert.HintList = this.VisitExpressionList(insert.HintList);
      insert.InsertList = this.VisitExpressionList(insert.InsertList);
      return insert;
    }
    public virtual Node VisitQueryIntersection(QueryIntersection intersection){
      if (intersection == null) return intersection;
      intersection.LeftSource = this.VisitExpression(intersection.LeftSource);
      intersection.RightSource = this.VisitExpression(intersection.RightSource);
      intersection.Type = intersection.LeftSource == null ? null : intersection.LeftSource.Type;
      return intersection;
    }
    public virtual Node VisitQueryIterator(QueryIterator xiterator){
      if (xiterator == null) return xiterator;
      xiterator.Expression = this.VisitExpression(xiterator.Expression);
      xiterator.HintList = this.VisitExpressionList(xiterator.HintList);
      return xiterator;      
    }
    public virtual Node VisitQueryJoin(QueryJoin join){
      if (join == null) return null;
      join.LeftOperand = this.VisitExpression(join.LeftOperand);
      join.RightOperand = this.VisitExpression(join.RightOperand);
      join.JoinExpression = this.VisitExpression(join.JoinExpression);
      return join;
    }
    public virtual Node VisitQueryLimit(QueryLimit limit){
      if (limit == null) return null;
      limit.Source = this.VisitExpression(limit.Source);
      limit.Expression = this.VisitExpression(limit.Expression);
      return limit;
    }
    public virtual Node VisitQueryOrderBy(QueryOrderBy orderby){
      if (orderby == null) return null;
      orderby.Source = this.VisitExpression(orderby.Source);
      orderby.OrderList = this.VisitExpressionList(orderby.OrderList);
      return orderby;
    }
    public virtual Node VisitQueryOrderItem(QueryOrderItem item){
      if (item == null) return null;
      item.Expression = this.VisitExpression(item.Expression);
      return item;
    }
    public virtual Node VisitQueryPosition(QueryPosition position){
      return position;
    }
    public virtual Node VisitQueryProject(QueryProject project){
      if (project == null) return null;
      project.Source = this.VisitExpression(project.Source);
      project.ProjectionList = this.VisitExpressionList(project.ProjectionList);
      return project;
    }
    public virtual Node VisitQueryRollback(QueryRollback qr){
      return qr;
    }
    public virtual Node VisitQueryQuantifier(QueryQuantifier qq){
      if (qq == null) return null;
      qq.Expression = this.VisitExpression(qq.Expression);
      return qq;
    }
    public virtual Node VisitQueryQuantifiedExpression(QueryQuantifiedExpression qqe){
      if (qqe == null) return null;
      qqe.Expression = this.VisitExpression(qqe.Expression);
      return qqe;
    }
    public virtual Node VisitQuerySelect(QuerySelect select){
      if (select == null) return null;
      select.Source = this.VisitExpression(select.Source);
      return select;
    }
    public virtual Node VisitQuerySingleton(QuerySingleton singleton){
      if (singleton == null) return null;
      singleton.Source = this.VisitExpression(singleton.Source);
      return singleton;
    }
    public virtual Node VisitQueryTransact(QueryTransact qt){
      if (qt == null) return null;
      qt.Source = this.VisitExpression(qt.Source);
      qt.Body = this.VisitBlock(qt.Body);
      qt.CommitBody = this.VisitBlock(qt.CommitBody);
      qt.RollbackBody = this.VisitBlock(qt.RollbackBody);
      return qt;
    }
    public virtual Node VisitQueryTypeFilter(QueryTypeFilter filter){
      if (filter == null) return null;
      filter.Source = this.VisitExpression(filter.Source);
      return filter;
    }
    public virtual Node VisitQueryUnion(QueryUnion union){
      if (union == null) return null;
      union.LeftSource = this.VisitExpression(union.LeftSource);
      union.RightSource = this.VisitExpression(union.RightSource);
      return union;
    }
    public virtual Node VisitQueryUpdate(QueryUpdate update){
      if (update == null) return null;
      update.Source = this.VisitExpression(update.Source);
      update.UpdateList = this.VisitExpressionList(update.UpdateList);
      return update;
    }    
    public virtual Node VisitQueryYielder(QueryYielder yielder){
      if (yielder == null) return null;
      yielder.Source = this.VisitExpression(yielder.Source);
      yielder.Target = this.VisitExpression(yielder.Target);
      yielder.Body = this.VisitBlock(yielder.Body);
      return yielder;
    }
#endif
#if !MinimalReader
    /// <summary>
    /// Return a type viewer for the current scope.
    /// [The type viewer acts like the identity function, except for dialects (e.g. Extensible Sing#)
    /// that allow extensions and differing views of types.]
    /// null can be returned to represent an identity-function type viewer.
    /// </summary>
    public virtual TypeViewer TypeViewer {
      get {
        return null;
      }
    }
    /// <summary>
    /// Return the current scope's view of the argument type, by asking the current scope's type viewer.
    /// </summary>
    public virtual TypeNode/*!*/ GetTypeView(TypeNode/*!*/ type) {
      return TypeViewer.GetTypeView(this.TypeViewer, type);
    }
#endif
  }
#if !MinimalReader && !CodeContracts
  /// <summary>
  /// Provides methods for invoking a parser to obtain AST nodes corresponding to various types of code snippets.
  /// </summary>
  public interface IParser{
    /// <summary>
    /// Parses the parser's source document as an entire compilation unit and adds the resulting AST nodes to the
    /// Nodes list of the given CompilationUnit instance.
    /// </summary>
    /// <param name="compilationUnit">The compilation unit whose Nodes list will receive the AST root node(s) that the parser produces.</param>
    void ParseCompilationUnit(CompilationUnit compilationUnit);
    Expression ParseExpression();
    void ParseStatements(StatementList statements);
    void ParseTypeMembers(TypeNode type);
  }
  ///<summary>Provides a way for general purpose code to construct parsers using an standard interface. 
  ///Useful for base classes without complete knowledge of all the different kinds of parsers that might be used in an application.</summary>
  public interface IParserFactory{
    IParser CreateParser(string fileName, int lineNumber, DocumentText text, Module symbolTable, ErrorNodeList errorNodes, CompilerParameters options);
  }
  public class SnippetParser : StandardVisitor{
    public IParserFactory/*!*/ DefaultParserFactory;
    public ErrorNodeList ErrorNodes;
    public Module SymbolTable;
    public StatementList CurrentStatementList;
    public CompilerParameters Options;

    public SnippetParser(IParserFactory/*!*/ defaultParserFactory, Module symbolTable, ErrorNodeList errorNodes, CompilerParameters options) {
      this.DefaultParserFactory = defaultParserFactory;
      this.ErrorNodes = errorNodes;
      this.SymbolTable = symbolTable;
      this.Options = options;
      this.CurrentStatementList = new StatementList(0);
      //^ base();
    }

    public override Node VisitUnknownNodeType(Node node) {
      return node; //Do not look for snippets inside unknown node types
    }
    public override Block VisitBlock(Block block){
      if (block == null) return null;
      StatementList savedStatementList = this.CurrentStatementList;
      try{
        StatementList oldStatements = block.Statements;
        int n = oldStatements == null ? 0 : oldStatements.Count;
        StatementList newStatements = this.CurrentStatementList = block.Statements = new StatementList(n);
        for (int i = 0; i < n; i++) {
          //^ assert oldStatements != null;
          newStatements.Add((Statement)this.Visit(oldStatements[i]));
        }
        return block;
      }finally{
        this.CurrentStatementList = savedStatementList;
      }
    }
    public override CompilationUnit VisitCompilationUnitSnippet(CompilationUnitSnippet snippet){
      if (snippet == null) return null;
      Document doc = snippet.SourceContext.Document;
      if (doc == null) return null;
      string fileName = doc.Name;
      int lineNumber = doc.LineNumber;
      DocumentText sourceText = doc.Text;
      IParserFactory pf = snippet.ParserFactory;
      IParser p;
      if (pf == null)
        p = this.DefaultParserFactory.CreateParser(fileName, lineNumber, sourceText, this.SymbolTable, this.ErrorNodes, this.Options);
      else
        p = pf.CreateParser(fileName, lineNumber, sourceText, this.SymbolTable, this.ErrorNodes, this.Options);
      if (p == null) return null;
      p.ParseCompilationUnit(snippet);
      return snippet;
    }
    public override Expression VisitExpressionSnippet(ExpressionSnippet snippet){
      if (snippet == null) return null;
      Document doc = snippet.SourceContext.Document;
      if (doc == null) return null;
      string fileName = doc.Name;
      int lineNumber = doc.LineNumber;
      DocumentText sourceText = doc.Text;
      IParserFactory pf = snippet.ParserFactory;
      IParser p;
      if (pf == null)
        p = this.DefaultParserFactory.CreateParser(fileName, lineNumber, sourceText, this.SymbolTable, this.ErrorNodes, this.Options);
      else
        p = pf.CreateParser(fileName, lineNumber, sourceText, this.SymbolTable, this.ErrorNodes, this.Options);
      if (p == null) return null;
      return p.ParseExpression();
    }
    public override StatementSnippet VisitStatementSnippet(StatementSnippet snippet){
      if (snippet == null) return null;
      Document doc = snippet.SourceContext.Document;
      if (doc == null) return null;
      string fileName = doc.Name;
      int lineNumber = doc.LineNumber;
      DocumentText sourceText = doc.Text;
      IParserFactory pf = snippet.ParserFactory;
      IParser p;
      if (pf == null)
        p = this.DefaultParserFactory.CreateParser(fileName, lineNumber, sourceText, this.SymbolTable, this.ErrorNodes, this.Options);
      else
        p = pf.CreateParser(fileName, lineNumber, sourceText, this.SymbolTable, this.ErrorNodes, this.Options);
      if (p == null) return null;
      p.ParseStatements(this.CurrentStatementList);
      return null;
    }
    public override TypeMemberSnippet VisitTypeMemberSnippet(TypeMemberSnippet snippet){
      if (snippet == null) return null;
      Document doc = snippet.SourceContext.Document;
      if (doc == null) return null;
      string fileName = doc.Name;
      int lineNumber = doc.LineNumber;
      DocumentText sourceText = doc.Text;
      IParserFactory pf = snippet.ParserFactory;
      IParser p;
      if (pf == null)
        p = this.DefaultParserFactory.CreateParser(fileName, lineNumber, sourceText, this.SymbolTable, this.ErrorNodes, this.Options);
      else
        p = pf.CreateParser(fileName, lineNumber, sourceText, this.SymbolTable, this.ErrorNodes, this.Options);
      if (p == null) return null;
      p.ParseTypeMembers(snippet.DeclaringType);
      return null;
    } 
  }
#endif
}