source: trunk/HeuristicLab.ExtLibs/HeuristicLab.NRefactory/5.5.0/NRefactory.CSharp-5.5.0/Completion/CSharpCompletionEngine.cs @ 17197

// 
// CSharpCompletionEngine.cs
//  
// Author:
//       Mike KrÃŒger <mkrueger@xamarin.com>
// 
// Copyright (c) 2011 Xamarin Inc. (http://xamarin.com)
// 
// 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.Linq;
using System.Text;
using ICSharpCode.NRefactory.Completion;
using ICSharpCode.NRefactory.CSharp.Refactoring;
using ICSharpCode.NRefactory.CSharp.Resolver;
using ICSharpCode.NRefactory.Editor;
using ICSharpCode.NRefactory.Semantics;
using ICSharpCode.NRefactory.TypeSystem;
using ICSharpCode.NRefactory.CSharp.TypeSystem;

namespace ICSharpCode.NRefactory.CSharp.Completion
{
  public enum EditorBrowsableBehavior
  {
    Ignore,
    Normal,
    IncludeAdvanced
  }

  public class CompletionEngineCache
  {
    public List<INamespace>  namespaces;
    public ICompletionData[] importCompletion;
  }

  public class CSharpCompletionEngine : CSharpCompletionEngineBase
  {
    internal ICompletionDataFactory factory;

    #region Additional input properties

    public CSharpFormattingOptions FormattingPolicy { get; set; }

    public string EolMarker { get; set; }

    public string IndentString { get; set; }

    public bool AutomaticallyAddImports { get; set; }

    public bool IncludeKeywordsInCompletionList { get; set; }

    public EditorBrowsableBehavior EditorBrowsableBehavior { get; set; }

    public CompletionEngineCache CompletionEngineCache { get; set; }

    #endregion

    #region Result properties

    public bool AutoCompleteEmptyMatch;
    /// <summary>
    /// The auto complete empty match on curly bracket. (only taken into account when AutoCompleteEmptyMatch is true )
    /// </summary>
    public bool AutoCompleteEmptyMatchOnCurlyBracket = true;
    public bool AutoSelect;
    public string DefaultCompletionString;
    public bool CloseOnSquareBrackets;
    public readonly List<IMethod> PossibleDelegates = new List<IMethod>();

    #endregion

    public CSharpCompletionEngine(IDocument document, ICompletionContextProvider completionContextProvider, ICompletionDataFactory factory, IProjectContent content, CSharpTypeResolveContext ctx) : base(content, completionContextProvider, ctx)
    {
      if (document == null) {
        throw new ArgumentNullException("document");
      }
      if (factory == null) {
        throw new ArgumentNullException("factory");
      }
      this.document = document;
      this.factory = factory;
      // Set defaults for additional input properties
      this.FormattingPolicy = FormattingOptionsFactory.CreateMono();
      this.EolMarker = Environment.NewLine;
      this.IncludeKeywordsInCompletionList = true;
      EditorBrowsableBehavior = EditorBrowsableBehavior.IncludeAdvanced;
      this.IndentString = "\t";
    }

    public bool TryGetCompletionWord(int offset, out int startPos, out int wordLength)
    {
      startPos = wordLength = 0;
      int pos = offset - 1;
      while (pos >= 0) {
        char c = document.GetCharAt(pos);
        if (!char.IsLetterOrDigit(c) && c != '_')
          break;
        pos--;
      }
      if (pos == -1)
        return false;

      pos++;
      startPos = pos;

      while (pos < document.TextLength) {
        char c = document.GetCharAt(pos);
        if (!char.IsLetterOrDigit(c) && c != '_')
          break;
        pos++;
      }
      wordLength = pos - startPos;
      return true;
    }

    public IEnumerable<ICompletionData> GetCompletionData(int offset, bool controlSpace)
    {
      this.AutoCompleteEmptyMatch = true;
      this.AutoSelect = true;
      this.DefaultCompletionString = null;
      SetOffset(offset);
      if (offset > 0) {
        char lastChar = document.GetCharAt(offset - 1);
        bool isComplete = false;
        var result = MagicKeyCompletion(lastChar, controlSpace, out isComplete) ?? Enumerable.Empty<ICompletionData>();
        if (!isComplete && controlSpace && char.IsWhiteSpace(lastChar)) {
          offset -= 2;
          while (offset >= 0 && char.IsWhiteSpace(document.GetCharAt(offset))) {
            offset--;
          }
          if (offset > 0) {
            var nonWsResult = MagicKeyCompletion(
              document.GetCharAt(offset),
              controlSpace,
              out isComplete
            );
            if (nonWsResult != null) {
              var text = new HashSet<string>(result.Select(r => r.CompletionText));
              result = result.Concat(nonWsResult.Where(r => !text.Contains(r.CompletionText)));
            }
          }
        }

        return result;
      }
      return Enumerable.Empty<ICompletionData>();
    }

    /// <summary>
    /// Gets the types that needs to be imported via using or full type name.
    /// </summary>
    public IEnumerable<ICompletionData> GetImportCompletionData(int offset)
    {
      var generalLookup = new MemberLookup(null, Compilation.MainAssembly);
      SetOffset(offset);

      // flatten usings
      var namespaces = new List<INamespace>();
      for (var n = ctx.CurrentUsingScope; n != null; n = n.Parent) {
        namespaces.Add(n.Namespace);
        foreach (var u in n.Usings)
          namespaces.Add(u);
      }

      foreach (var type in Compilation.GetAllTypeDefinitions ()) {
        if (!generalLookup.IsAccessible(type, false))
          continue; 
        if (namespaces.Any(n => n.FullName == type.Namespace))
          continue;
        bool useFullName = false;
        foreach (var ns in namespaces) {
          if (ns.GetTypeDefinition(type.Name, type.TypeParameterCount) != null) {
            useFullName = true;
            break;
          }
        }
        yield return factory.CreateImportCompletionData(type, useFullName, false);
      }
    }

    IEnumerable<string> GenerateNameProposals(AstType type)
    {
      if (type is PrimitiveType) {
        var pt = (PrimitiveType)type;
        switch (pt.Keyword) {
          case "object":
            yield return "o";
            yield return "obj";
            break;
          case "bool":
            yield return "b";
            yield return "pred";
            break;
          case "double":
          case "float":
          case "decimal":
            yield return "d";
            yield return "f";
            yield return "m";
            break;
          default:
            yield return "i";
            yield return "j";
            yield return "k";
            break;
        }
        yield break;
      }
      string name;
      if (type is SimpleType) {
        name = ((SimpleType)type).Identifier;
      } else if (type is MemberType) {
        name = ((MemberType)type).MemberName;
      } else {
        yield break;
      }

      var names = WordParser.BreakWords(name);

      var possibleName = new StringBuilder();
      for (int i = 0; i < names.Count; i++) {
        possibleName.Length = 0;
        for (int j = i; j < names.Count; j++) {
          if (string.IsNullOrEmpty(names [j])) {
            continue;
          }
          if (j == i) { 
            names [j] = Char.ToLower(names [j] [0]) + names [j].Substring(1);
          }
          possibleName.Append(names [j]);
        }
        yield return possibleName.ToString();
      }
    }

    IEnumerable<ICompletionData> HandleMemberReferenceCompletion(ExpressionResult expr)
    {
      if (expr == null)
        return null;

      // do not auto select <number>. (but <number>.<number>.) (0.ToString() is valid)
      if (expr.Node is PrimitiveExpression) {
        var pexpr = (PrimitiveExpression)expr.Node;
        if (!(pexpr.Value is string || pexpr.Value is char) && !pexpr.LiteralValue.Contains('.')) {
          AutoSelect = false;
        }
      }
      var resolveResult = ResolveExpression(expr);

      if (resolveResult == null) {
        return null;
      }
      if (expr.Node is AstType) {

        // check for namespace names
        if (expr.Node.AncestorsAndSelf
          .TakeWhile(n => n is AstType)
          .Any(m => m.Role == NamespaceDeclaration.NamespaceNameRole))
          return null;

        // need to look at paren.parent because of "catch (<Type>.A" expression
        if (expr.Node.Parent != null && expr.Node.Parent.Parent is CatchClause)
          return HandleCatchClauseType(expr);
        return CreateTypeAndNamespaceCompletionData(
          location,
          resolveResult.Result,
          expr.Node,
          resolveResult.Resolver
        );
      }


      return CreateCompletionData(
        location,
        resolveResult.Result,
        expr.Node,
        resolveResult.Resolver
      );
    }

    bool IsInPreprocessorDirective()
    {
      var text = GetMemberTextToCaret().Item1;
      var miniLexer = new MiniLexer(text);
      miniLexer.Parse();
      return miniLexer.IsInPreprocessorDirective;
    }

    IEnumerable<ICompletionData> HandleObjectInitializer(SyntaxTree unit, AstNode n)
    {
      var p = n.Parent;
      while (p != null && !(p is ObjectCreateExpression)) {
        p = p.Parent;
      }
      var parent = n.Parent as ArrayInitializerExpression;
      if (parent == null)
        return null;
      if (parent.IsSingleElement)
        parent = (ArrayInitializerExpression)parent.Parent;
      if (p != null) {
        var contextList = new CompletionDataWrapper(this);
        var initializerResult = ResolveExpression(p);
        IType initializerType = null;

        if (initializerResult.Result is DynamicInvocationResolveResult) {
          var dr = (DynamicInvocationResolveResult)initializerResult.Result;
          var constructor = (dr.Target as MethodGroupResolveResult).Methods.FirstOrDefault();
          if (constructor != null)
            initializerType = constructor.DeclaringType;
        } else {
          initializerType = initializerResult != null ? initializerResult.Result.Type : null;
        }


        if (initializerType != null && initializerType.Kind != TypeKind.Unknown) {
          // check 3 cases:
          // 1) New initalizer { xpr
          // 2) Object initializer { prop = val1, field = val2, xpr
          // 3) Array initializer { new Foo (), a, xpr
          // in case 1 all object/array initializer options should be given - in the others not.

          AstNode prev = null;
          if (parent.Elements.Count > 1) {
            prev = parent.Elements.First();
            if (prev is ArrayInitializerExpression && ((ArrayInitializerExpression)prev).IsSingleElement)
              prev = ((ArrayInitializerExpression)prev).Elements.FirstOrDefault();
          }

          if (prev != null && !(prev is NamedExpression)) {
            AddContextCompletion(contextList, GetState(), n);
            // case 3)
            return contextList.Result;
          }
          var lookup = new MemberLookup(ctx.CurrentTypeDefinition, Compilation.MainAssembly);
          var list = typeof(System.Collections.IList).ToTypeReference().Resolve(Compilation);
          var list1 = typeof(System.Collections.Generic.IList<>).ToTypeReference().Resolve(Compilation);
          bool isProtectedAllowed = ctx.CurrentTypeDefinition != null && initializerType.GetDefinition() != null ? 
            ctx.CurrentTypeDefinition.IsDerivedFrom(initializerType.GetDefinition()) : 
            false;
          foreach (var m in initializerType.GetMembers (m => m.SymbolKind == SymbolKind.Field)) {
            var f = m as IField;
            if (f != null && (f.IsReadOnly || f.IsConst))
              continue;
            if (lookup.IsAccessible(m, isProtectedAllowed)) {
              var data = contextList.AddMember(m);
              if (data != null)
                data.DisplayFlags |= DisplayFlags.NamedArgument;
            }
          }

          foreach (IProperty m in initializerType.GetMembers (m => m.SymbolKind == SymbolKind.Property)) {
            if (m.CanSet && lookup.IsAccessible(m.Setter, isProtectedAllowed)  || 
              m.CanGet && lookup.IsAccessible(m.Getter, isProtectedAllowed) && m.ReturnType.GetDefinition() != null && 
              (m.ReturnType.GetDefinition().IsDerivedFrom(list.GetDefinition()) || m.ReturnType.GetDefinition().IsDerivedFrom(list1.GetDefinition()))) {
              var data = contextList.AddMember(m);
              if (data != null)
                data.DisplayFlags |= DisplayFlags.NamedArgument;
            }
          }

          if (prev != null && (prev is NamedExpression)) {
            // case 2)
            return contextList.Result;
          }

          // case 1)

          // check if the object is a list, if not only provide object initalizers
          if (initializerType.Kind != TypeKind.Array && list != null) {
            var def = initializerType.GetDefinition(); 
            if (def != null && !def.IsDerivedFrom(list.GetDefinition()) && !def.IsDerivedFrom(list1.GetDefinition()))
              return contextList.Result;
          }

          AddContextCompletion(contextList, GetState(), n);
          return contextList.Result;
        }
      }
      return null;
    }

    static readonly DateTime curDate = DateTime.Now;

    IEnumerable<ICompletionData> GenerateNumberFormatitems(bool isFloatingPoint)
    {
      yield return factory.CreateFormatItemCompletionData("D", "decimal", 123);
      yield return factory.CreateFormatItemCompletionData("D5", "decimal", 123);
      yield return factory.CreateFormatItemCompletionData("C", "currency", 123);
      yield return factory.CreateFormatItemCompletionData("C0", "currency", 123);
      yield return factory.CreateFormatItemCompletionData("E", "exponential", 1.23E4);
      yield return factory.CreateFormatItemCompletionData("E2", "exponential", 1.234);
      yield return factory.CreateFormatItemCompletionData("e2", "exponential", 1.234);
      yield return factory.CreateFormatItemCompletionData("F", "fixed-point", 123.45);
      yield return factory.CreateFormatItemCompletionData("F1", "fixed-point", 123.45);
      yield return factory.CreateFormatItemCompletionData("G", "general", 1.23E+56);
      yield return factory.CreateFormatItemCompletionData("g2", "general", 1.23E+56);
      yield return factory.CreateFormatItemCompletionData("N", "number", 12345.68);
      yield return factory.CreateFormatItemCompletionData("N1", "number", 12345.68);
      yield return factory.CreateFormatItemCompletionData("P", "percent", 12.34);
      yield return factory.CreateFormatItemCompletionData("P1", "percent", 12.34);
      yield return factory.CreateFormatItemCompletionData("R", "round-trip", 0.1230000001);
      yield return factory.CreateFormatItemCompletionData("X", "hexadecimal", 1234);
      yield return factory.CreateFormatItemCompletionData("x8", "hexadecimal", 1234);
      yield return factory.CreateFormatItemCompletionData("0000", "custom", 123);
      yield return factory.CreateFormatItemCompletionData("####", "custom", 123);
      yield return factory.CreateFormatItemCompletionData("##.###", "custom", 1.23);
      yield return factory.CreateFormatItemCompletionData("##.000", "custom", 1.23);
      yield return factory.CreateFormatItemCompletionData("## 'items'", "custom", 12);
    }

    IEnumerable<ICompletionData> GenerateDateTimeFormatitems()
    {
      yield return factory.CreateFormatItemCompletionData("D", "long date", curDate);
      yield return factory.CreateFormatItemCompletionData("d", "short date", curDate);
      yield return factory.CreateFormatItemCompletionData("F", "full date long", curDate);
      yield return factory.CreateFormatItemCompletionData("f", "full date short", curDate);
      yield return factory.CreateFormatItemCompletionData("G", "general long", curDate);
      yield return factory.CreateFormatItemCompletionData("g", "general short", curDate);
      yield return factory.CreateFormatItemCompletionData("M", "month", curDate);
      yield return factory.CreateFormatItemCompletionData("O", "ISO 8601", curDate);
      yield return factory.CreateFormatItemCompletionData("R", "RFC 1123", curDate);
      yield return factory.CreateFormatItemCompletionData("s", "sortable", curDate);
      yield return factory.CreateFormatItemCompletionData("T", "long time", curDate);
      yield return factory.CreateFormatItemCompletionData("t", "short time", curDate);
      yield return factory.CreateFormatItemCompletionData("U", "universal full", curDate);
      yield return factory.CreateFormatItemCompletionData("u", "universal sortable", curDate);
      yield return factory.CreateFormatItemCompletionData("Y", "year month", curDate);
      yield return factory.CreateFormatItemCompletionData("yy-MM-dd", "custom", curDate);
      yield return factory.CreateFormatItemCompletionData("yyyy MMMMM dd", "custom", curDate);
      yield return factory.CreateFormatItemCompletionData("yy-MMM-dd ddd", "custom", curDate);
      yield return factory.CreateFormatItemCompletionData("yyyy-M-d dddd", "custom", curDate);
      yield return factory.CreateFormatItemCompletionData("hh:mm:ss t z", "custom", curDate);
      yield return factory.CreateFormatItemCompletionData("hh:mm:ss tt zz", "custom", curDate);
      yield return factory.CreateFormatItemCompletionData("HH:mm:ss tt zz", "custom", curDate);
      yield return factory.CreateFormatItemCompletionData("HH:m:s tt zz", "custom", curDate);

    }

    [Flags]
    enum TestEnum
    {
      EnumCaseName = 0,
      Flag1 = 1,
      Flag2 = 2,
      Flags

    }

    IEnumerable<ICompletionData> GenerateEnumFormatitems()
    {
      yield return factory.CreateFormatItemCompletionData("G", "string value", TestEnum.EnumCaseName);
      yield return factory.CreateFormatItemCompletionData("F", "flags value", TestEnum.Flags);
      yield return factory.CreateFormatItemCompletionData("D", "integer value", TestEnum.Flags);
      yield return factory.CreateFormatItemCompletionData("X", "hexadecimal", TestEnum.Flags);
    }

    IEnumerable<ICompletionData> GenerateTimeSpanFormatitems()
    {
      yield return factory.CreateFormatItemCompletionData("c", "invariant", new TimeSpan(0, 1, 23, 456));
      yield return factory.CreateFormatItemCompletionData("G", "general long", new TimeSpan(0, 1, 23, 456));
      yield return factory.CreateFormatItemCompletionData("g", "general short", new TimeSpan(0, 1, 23, 456));
    }

    static Guid defaultGuid = Guid.NewGuid();

    IEnumerable<ICompletionData> GenerateGuidFormatitems()
    {
      yield return factory.CreateFormatItemCompletionData("N", "digits", defaultGuid);
      yield return factory.CreateFormatItemCompletionData("D", "hypens", defaultGuid);
      yield return factory.CreateFormatItemCompletionData("B", "braces", defaultGuid);
      yield return factory.CreateFormatItemCompletionData("P", "parentheses", defaultGuid);
    }

    int GetFormatItemNumber()
    {
      int number = 0;
      var o = offset - 2;
      while (o > 0) {
        char ch = document.GetCharAt(o);
        if (ch == '{')
          return number;
        if (!char.IsDigit(ch))
          break;
        number = number * 10 + ch - '0';
        o--;
      }
      return -1;
    }

    IEnumerable<ICompletionData> HandleStringFormatItems()
    {
      var formatArgument = GetFormatItemNumber();
      if (formatArgument < 0)
        return Enumerable.Empty<ICompletionData>();
      var followUp = new StringBuilder();

      var o = offset;
      while (o < document.TextLength) {
        char ch = document.GetCharAt(o);
        followUp.Append(ch); 
        o++;
        if (ch == ';')
          break;
      }
      var unit = ParseStub(followUp.ToString(), false);

      var invoke = unit.GetNodeAt<InvocationExpression>(location);

      if (invoke != null) {
        var resolveResult = ResolveExpression(new ExpressionResult(invoke, unit));
        var invokeResult = resolveResult.Result as InvocationResolveResult;
        if (invokeResult != null) {
          var arg = formatArgument + 1; // First argument is the format string
          if (arg < invoke.Arguments.Count) {
            var invokeArgument = ResolveExpression(new ExpressionResult(invoke.Arguments.ElementAt(arg), unit));
            if (invokeArgument != null) {
              var provider = GetFormatCompletionData(invokeArgument.Result.Type);
              if (provider != null)
                return provider;
              if (!invokeArgument.Result.Type.IsKnownType(KnownTypeCode.Object))
                return Enumerable.Empty<ICompletionData>();
            }
          }
        }
      }
      return HandleStringFormatItemsFallback();
    }

    IEnumerable<ICompletionData> HandleStringFormatItemsFallback()
    {
      var unit = ParseStub("a}\");", false);

      var invoke = unit.GetNodeAt<InvocationExpression>(location);

      if (invoke == null)
        return Enumerable.Empty<ICompletionData>();

      var resolveResult = ResolveExpression(new ExpressionResult(invoke, unit));
      var invokeResult = resolveResult.Result as CSharpInvocationResolveResult;
      if (invokeResult == null)
        return Enumerable.Empty<ICompletionData>();

      Expression fmtArgumets;
      IList<Expression> args;
      if (FormatStringHelper.TryGetFormattingParameters(invokeResult, invoke, out fmtArgumets, out args, null)) {
        return GenerateNumberFormatitems(false)
          .Concat(GenerateDateTimeFormatitems())
          .Concat(GenerateTimeSpanFormatitems())
          .Concat(GenerateEnumFormatitems())
          .Concat(GenerateGuidFormatitems());
      }
      return Enumerable.Empty<ICompletionData>();

    }

    IEnumerable<ICompletionData> GetFormatCompletionData(IType type)
    {
      if (type.Namespace != "System")
        return null;
      switch (type.Name) {
        case "Int64":
        case "UInt64":
        case "Int32":
        case "UInt32":
        case "Int16":
        case "UInt16":
        case "Byte":
        case "SByte":
          return GenerateNumberFormatitems(false);
        case "Single":
        case "Double":
        case "Decimal":
          return GenerateNumberFormatitems(true);
        case "Enum":
          return GenerateEnumFormatitems();
        case "DateTime":
          return GenerateDateTimeFormatitems();
        case "TimeSpan":
          return GenerateTimeSpanFormatitems();
        case "Guid":
          return GenerateGuidFormatitems();
      }
      return null;
    }

    IEnumerable<ICompletionData> HandleToStringFormatItems()
    {
      var unit = ParseStub("\");", false);

      var invoke = unit.GetNodeAt<InvocationExpression>(location);
      if (invoke == null)
        return Enumerable.Empty<ICompletionData>();

      var resolveResult = ResolveExpression(new ExpressionResult(invoke, unit));
      var invokeResult = resolveResult.Result as InvocationResolveResult;
      if (invokeResult == null)
        return Enumerable.Empty<ICompletionData>();
      if (invokeResult.Member.Name == "ToString")
        return GetFormatCompletionData(invokeResult.Member.DeclaringType) ?? Enumerable.Empty<ICompletionData>();
      return Enumerable.Empty<ICompletionData>();
    }

    IEnumerable<ICompletionData> MagicKeyCompletion(char completionChar, bool controlSpace, out bool isComplete)
    {
      isComplete = false;
      ExpressionResolveResult resolveResult;
      switch (completionChar) {
        // Magic key completion
        case ':':
          var text = GetMemberTextToCaret();
          var lexer = new MiniLexer(text.Item1);
          lexer.Parse();
          if (lexer.IsInSingleComment ||
            lexer.IsInChar ||
            lexer.IsInMultiLineComment ||
            lexer.IsInPreprocessorDirective) {
            return Enumerable.Empty<ICompletionData>();
          }

          if (lexer.IsInString || lexer.IsInVerbatimString)
            return HandleStringFormatItems();
          return HandleMemberReferenceCompletion(GetExpressionBeforeCursor());
        case '"':
          text = GetMemberTextToCaret();
          lexer = new MiniLexer(text.Item1);
          lexer.Parse();
          if (lexer.IsInSingleComment ||
            lexer.IsInChar ||
            lexer.IsInMultiLineComment ||
            lexer.IsInPreprocessorDirective) {
            return Enumerable.Empty<ICompletionData>();
          }

          if (lexer.IsInString || lexer.IsInVerbatimString)
            return HandleToStringFormatItems();
          return Enumerable.Empty<ICompletionData>();
        case '.':
          if (IsInsideCommentStringOrDirective()) {
            return Enumerable.Empty<ICompletionData>();
          }
          return HandleMemberReferenceCompletion(GetExpressionBeforeCursor());
        case '#':
          if (!IsInPreprocessorDirective())
            return null;
          return GetDirectiveCompletionData();
          // XML doc completion
        case '<':
          if (IsInsideDocComment()) {
            return GetXmlDocumentationCompletionData();
          }
          if (controlSpace) {
            return DefaultControlSpaceItems(ref isComplete);
          }
          return null;
        case '>':
          if (!IsInsideDocComment()) {
            if (offset > 2 && document.GetCharAt(offset - 2) == '-' && !IsInsideCommentStringOrDirective()) {
              return HandleMemberReferenceCompletion(GetExpressionBeforeCursor());
            }
            return null;
          }
          return null;

          // Parameter completion
        case '(':
          if (IsInsideCommentStringOrDirective()) {
            return null;
          }
          var invoke = GetInvocationBeforeCursor(true);
          if (invoke == null) {
            if (controlSpace)
              return DefaultControlSpaceItems(ref isComplete, invoke);
            return null;
          }
          if (invoke.Node is TypeOfExpression) {
            return CreateTypeList();
          }
          var invocationResult = ResolveExpression(invoke);
          if (invocationResult == null) {
            return null;
          }
          var methodGroup = invocationResult.Result as MethodGroupResolveResult;
          if (methodGroup != null) {
            return CreateParameterCompletion(
              methodGroup,
              invocationResult.Resolver,
              invoke.Node,
              invoke.Unit,
              0,
              controlSpace
            );
          }

          if (controlSpace) {
            return DefaultControlSpaceItems(ref isComplete, invoke);
          }
          return null;
        case '=':
          return controlSpace ? DefaultControlSpaceItems(ref isComplete) : null;
        case ',':
          int cpos2;
          if (!GetParameterCompletionCommandOffset(out cpos2)) { 
            return null;
          }
          //  completionContext = CompletionWidget.CreateCodeCompletionContext (cpos2);
          //  int currentParameter2 = MethodParameterDataProvider.GetCurrentParameterIndex (CompletionWidget, completionContext) - 1;
          //        return CreateParameterCompletion (CreateResolver (), location, ExpressionContext.MethodBody, provider.Methods, currentParameter); 
          break;

          // Completion on space:
        case ' ':
          int tokenIndex = offset;
          string token = GetPreviousToken(ref tokenIndex, false);
          if (IsInsideCommentStringOrDirective()) {
            return null;
          }
          // check propose name, for context <variable name> <ctrl+space> (but only in control space context)
          //IType isAsType = null;
          var isAsExpression = GetExpressionAt(offset);
          if (controlSpace && isAsExpression != null && isAsExpression.Node is VariableDeclarationStatement && token != "new") {
            var parent = isAsExpression.Node as VariableDeclarationStatement;
            var proposeNameList = new CompletionDataWrapper(this);
            if (parent.Variables.Count != 1)
              return DefaultControlSpaceItems(ref isComplete, isAsExpression, controlSpace);

            foreach (var possibleName in GenerateNameProposals (parent.Type)) {
              if (possibleName.Length > 0) {
                proposeNameList.Result.Add(factory.CreateLiteralCompletionData(possibleName.ToString()));
              }
            }

            AutoSelect = false;
            AutoCompleteEmptyMatch = false;
            isComplete = true;
            return proposeNameList.Result;
          }
          //        int tokenIndex = offset;
          //        string token = GetPreviousToken (ref tokenIndex, false);
          //        if (result.ExpressionContext == ExpressionContext.ObjectInitializer) {
          //          resolver = CreateResolver ();
          //          ExpressionContext exactContext = new NewCSharpExpressionFinder (dom).FindExactContextForObjectInitializer (document, resolver.Unit, Document.FileName, resolver.CallingType);
          //          IReturnType objectInitializer = ((ExpressionContext.TypeExpressionContext)exactContext).UnresolvedType;
          //          if (objectInitializer != null && objectInitializer.ArrayDimensions == 0 && objectInitializer.PointerNestingLevel == 0 && (token == "{" || token == ","))
          //            return CreateCtrlSpaceCompletionData (completionContext, result); 
          //        }
          if (token == "=") {
            int j = tokenIndex;
            string prevToken = GetPreviousToken(ref j, false);
            if (prevToken == "=" || prevToken == "+" || prevToken == "-" || prevToken == "!") {
              token = prevToken + token;
              tokenIndex = j;
            }
          }
          switch (token) {
            case "(":
            case ",":
              int cpos;
              if (!GetParameterCompletionCommandOffset(out cpos)) { 
                break;
              }
              int currentParameter = GetCurrentParameterIndex(cpos - 1, this.offset) - 1;
              if (currentParameter < 0) {
                return null;
              }
              invoke = GetInvocationBeforeCursor(token == "(");
              if (invoke == null) {
                return null;
              }
              invocationResult = ResolveExpression(invoke);
              if (invocationResult == null) {
                return null;
              }
              methodGroup = invocationResult.Result as MethodGroupResolveResult;
              if (methodGroup != null) {
                return CreateParameterCompletion(
                  methodGroup,
                  invocationResult.Resolver,
                  invoke.Node,
                  invoke.Unit,
                  currentParameter,
                  controlSpace);
              }
              return null;
            case "=":
            case "==":
            case "!=":
              GetPreviousToken(ref tokenIndex, false);
              var expressionOrVariableDeclaration = GetExpressionAt(tokenIndex);
              if (expressionOrVariableDeclaration == null) {
                return null;
              }
              resolveResult = ResolveExpression(expressionOrVariableDeclaration);
              if (resolveResult == null) {
                return null;
              }
              if (resolveResult.Result.Type.Kind == TypeKind.Enum) {
                var wrapper = new CompletionDataWrapper(this);
                AddContextCompletion(
                  wrapper,
                  resolveResult.Resolver,
                  expressionOrVariableDeclaration.Node);
                AddEnumMembers(wrapper, resolveResult.Result.Type, resolveResult.Resolver);
                AutoCompleteEmptyMatch = false;
                return wrapper.Result;
              }
              //        
              //          if (resolvedType.FullName == DomReturnType.Bool.FullName) {
              //            CompletionDataList completionList = new ProjectDomCompletionDataList ();
              //            CompletionDataCollector cdc = new CompletionDataCollector (this, dom, completionList, Document.CompilationUnit, resolver.CallingType, location);
              //            completionList.AutoCompleteEmptyMatch = false;
              //            cdc.Add ("true", "md-keyword");
              //            cdc.Add ("false", "md-keyword");
              //            resolver.AddAccessibleCodeCompletionData (result.ExpressionContext, cdc);
              //            return completionList;
              //          }
              //          if (resolvedType.ClassType == ClassType.Delegate && token == "=") {
              //            CompletionDataList completionList = new ProjectDomCompletionDataList ();
              //            string parameterDefinition = AddDelegateHandlers (completionList, resolvedType);
              //            string varName = GetPreviousMemberReferenceExpression (tokenIndex);
              //            completionList.Add (new EventCreationCompletionData (document, varName, resolvedType, null, parameterDefinition, resolver.CallingMember, resolvedType));
              //            
              //            CompletionDataCollector cdc = new CompletionDataCollector (this, dom, completionList, Document.CompilationUnit, resolver.CallingType, location);
              //            resolver.AddAccessibleCodeCompletionData (result.ExpressionContext, cdc);
              //            foreach (var data in completionList) {
              //              if (data is MemberCompletionData) 
              //                ((MemberCompletionData)data).IsDelegateExpected = true;
              //            }
              //            return completionList;
              //          }
              return null;
            case "+=":
            case "-=":
              var curTokenIndex = tokenIndex;
              GetPreviousToken(ref tokenIndex, false);

              expressionOrVariableDeclaration = GetExpressionAt(tokenIndex);
              if (expressionOrVariableDeclaration == null) {
                return null;
              }

              resolveResult = ResolveExpression(expressionOrVariableDeclaration);
              if (resolveResult == null) {
                return null;
              }


              var mrr = resolveResult.Result as MemberResolveResult;
              if (mrr != null) {
                var evt = mrr.Member as IEvent;
                if (evt == null) {
                  return null;
                }
                var delegateType = evt.ReturnType;
                if (delegateType.Kind != TypeKind.Delegate) {
                  return null;
                }

                var wrapper = new CompletionDataWrapper(this);
                if (currentType != null) {
                  //              bool includeProtected = DomType.IncludeProtected (dom, typeFromDatabase, resolver.CallingType);
                  foreach (var method in ctx.CurrentTypeDefinition.Methods) {
                    if (MatchDelegate(delegateType, method) /*                    && method.IsAccessibleFrom (dom, resolver.CallingType, resolver.CallingMember, includeProtected) &&*/) {
                      wrapper.AddMember(method);
                      //                  data.SetText (data.CompletionText + ";");
                    }
                  }
                }
                if (token == "+=") {
                  string parameterDefinition = AddDelegateHandlers(
                    wrapper,
                    delegateType,
                    optDelegateName: GuessEventHandlerMethodName(curTokenIndex, (currentType == null) ? null : currentType.Name)
                  );
                }

                return wrapper.Result;
              }
              return null;
            case ":":
              if (currentMember == null) {
                token = GetPreviousToken(ref tokenIndex, false);
                token = GetPreviousToken(ref tokenIndex, false);
                if (token == "enum")
                  return HandleEnumContext();
                var wrapper = new CompletionDataWrapper(this);
                AddTypesAndNamespaces(
                  wrapper,
                  GetState(),
                  null,
                  t =>  {
                    if (currentType != null && currentType.ReflectionName.Equals(t.ReflectionName))
                      return null;
                    var def = t.GetDefinition();
                    if (def != null && t.Kind != TypeKind.Interface && (def.IsSealed ||def.IsStatic))
                      return null;
                    return t;
                  }
                );
                return wrapper.Result;
              }
              return null;
          }

          var keywordCompletion = HandleKeywordCompletion(tokenIndex, token);
          if (keywordCompletion == null && controlSpace) {
            goto default;
          }
          return keywordCompletion;
          // Automatic completion
        default:
          if (IsInsideCommentStringOrDirective()) {
            tokenIndex = offset;
            token = GetPreviousToken(ref tokenIndex, false);
            if (IsInPreprocessorDirective() && (token.Length == 1 && char.IsLetter(completionChar) || controlSpace)) {
              while (token != null && document.GetCharAt(tokenIndex - 1) != '#') {
                token = GetPreviousToken(ref tokenIndex, false);
              }
              if (token != null)
                return HandleKeywordCompletion(tokenIndex, token);
            }
            return null;
          }
          char prevCh = offset > 2 ? document.GetCharAt(offset - 2) : ';';
          char nextCh = offset < document.TextLength ? document.GetCharAt(offset) : ' ';
          const string allowedChars = ";,.[](){}+-*/%^?:&|~!<>=";

          if ((!Char.IsWhiteSpace(nextCh) && allowedChars.IndexOf(nextCh) < 0) || !(Char.IsWhiteSpace(prevCh) || allowedChars.IndexOf(prevCh) >= 0)) {
            if (!controlSpace)
              return null;
          }

          if (IsInLinqContext(offset)) {
            if (!controlSpace && !(char.IsLetter(completionChar) || completionChar == '_')) {
              return null;
            }
            tokenIndex = offset;
            token = GetPreviousToken(ref tokenIndex, false);
            // token last typed
            if (!char.IsWhiteSpace(completionChar) && !linqKeywords.Contains(token)) {
              token = GetPreviousToken(ref tokenIndex, false);
            }
            // token last typed

            if (linqKeywords.Contains(token)) {
              if (token == "from") {
                // after from no auto code completion.
                return null;
              }
              return DefaultControlSpaceItems(ref isComplete);
            }
            var dataList = new CompletionDataWrapper(this);
            AddKeywords(dataList, linqKeywords);
            return dataList.Result;
          }
          if (currentType != null && currentType.Kind == TypeKind.Enum) {
            if (!char.IsLetter(completionChar))
              return null;
            return HandleEnumContext();
          }
          var contextList = new CompletionDataWrapper(this);
          var identifierStart = GetExpressionAtCursor();
          if (!(char.IsLetter(completionChar) || completionChar == '_') && (!controlSpace || identifierStart == null)) {
            return controlSpace ? HandleAccessorContext() ?? DefaultControlSpaceItems(ref isComplete, identifierStart) : null;
          }

          if (identifierStart != null) {
            if (identifierStart.Node is TypeParameterDeclaration) {
              return null;
            }

            if (identifierStart.Node is MemberReferenceExpression) {
              return HandleMemberReferenceCompletion(
                new ExpressionResult(
                  ((MemberReferenceExpression)identifierStart.Node).Target,
                  identifierStart.Unit
                )
              );
            }

            if (identifierStart.Node is Identifier) {
              if (identifierStart.Node.Parent is GotoStatement)
                return null;

              // May happen in variable names
              return controlSpace ? DefaultControlSpaceItems(ref isComplete, identifierStart) : null;
            }
            if (identifierStart.Node is VariableInitializer && location <= ((VariableInitializer)identifierStart.Node).NameToken.EndLocation) {
              return controlSpace ? HandleAccessorContext() ?? DefaultControlSpaceItems(ref isComplete, identifierStart) : null;
            }
            if (identifierStart.Node is CatchClause) {
              if (((CatchClause)identifierStart.Node).VariableNameToken.IsInside(location)) {
                return null;
              }
            }
            if (identifierStart.Node is AstType && identifierStart.Node.Parent is CatchClause) {
              return HandleCatchClauseType(identifierStart);
            }

            var pDecl = identifierStart.Node as ParameterDeclaration;
            if (pDecl != null && pDecl.Parent is LambdaExpression) {
              return null;
            }
          }


          // Do not pop up completion on identifier identifier (should be handled by keyword completion).
          tokenIndex = offset - 1;
          token = GetPreviousToken(ref tokenIndex, false);
          if (token == "class" || token == "interface" || token == "struct" || token == "enum" || token == "namespace") {
            // after these always follows a name
            return null;
          }
          var keywordresult = HandleKeywordCompletion(tokenIndex, token);
          if (keywordresult != null) {
            return keywordresult;
          }

          if ((!Char.IsWhiteSpace(nextCh) && allowedChars.IndexOf(nextCh) < 0) || !(Char.IsWhiteSpace(prevCh) || allowedChars.IndexOf(prevCh) >= 0)) {
            if (controlSpace)
              return DefaultControlSpaceItems(ref isComplete, identifierStart);
          }

          int prevTokenIndex = tokenIndex;
          var prevToken2 = GetPreviousToken(ref prevTokenIndex, false);
          if (prevToken2 == "delegate") {
            // after these always follows a name
            return null;
          }

          if (identifierStart == null && !string.IsNullOrEmpty(token) && !IsInsideCommentStringOrDirective() && (prevToken2 == ";" || prevToken2 == "{" || prevToken2 == "}")) {
            char last = token [token.Length - 1];
            if (char.IsLetterOrDigit(last) || last == '_' || token == ">") {
              return HandleKeywordCompletion(tokenIndex, token);
            }
          }
          if (identifierStart == null) {
            var accCtx = HandleAccessorContext();
            if (accCtx != null) {
              return accCtx;
            }
            return DefaultControlSpaceItems(ref isComplete, null, controlSpace);
          }
          CSharpResolver csResolver;
          AstNode n = identifierStart.Node;
          if (n.Parent is NamedArgumentExpression)
            n = n.Parent;

          if (n != null && n.Parent is AnonymousTypeCreateExpression) {
            AutoSelect = false;
          }

          // new { b$ } 
          if (n is IdentifierExpression && n.Parent is AnonymousTypeCreateExpression)
            return null;

          // Handle foreach (type name _
          if (n is IdentifierExpression) {
            var prev = n.GetPrevNode() as ForeachStatement;
            while (prev != null && prev.EmbeddedStatement is ForeachStatement)
              prev = (ForeachStatement)prev.EmbeddedStatement;
            if (prev != null && prev.InExpression.IsNull) {
              if (IncludeKeywordsInCompletionList)
                contextList.AddCustom("in");
              return contextList.Result;
            }
          }
          // Handle object/enumerable initialzer expressions: "new O () { P$"
          if (n is IdentifierExpression && n.Parent is ArrayInitializerExpression && !(n.Parent.Parent is ArrayCreateExpression)) {
            var result = HandleObjectInitializer(identifierStart.Unit, n);
            if (result != null)
              return result;
          }

          if (n != null && n.Parent is InvocationExpression ||
            n.Parent is ParenthesizedExpression && n.Parent.Parent is InvocationExpression) {
            if (n.Parent is ParenthesizedExpression)
              n = n.Parent;
            var invokeParent = (InvocationExpression)n.Parent;
            var invokeResult = ResolveExpression(
              invokeParent.Target
            );
            var mgr = invokeResult != null ? invokeResult.Result as MethodGroupResolveResult : null;
            if (mgr != null) {
              int idx = 0;
              foreach (var arg in invokeParent.Arguments) {
                if (arg == n) {
                  break;
                }
                idx++;
              }

              foreach (var method in mgr.Methods) {
                if (idx < method.Parameters.Count && method.Parameters [idx].Type.Kind == TypeKind.Delegate) {
                  AutoSelect = false;
                  AutoCompleteEmptyMatch = false;
                }
                foreach (var p in method.Parameters) {
                  contextList.AddNamedParameterVariable(p);
                }
              }
              idx++;
              foreach (var list in mgr.GetEligibleExtensionMethods (true)) {
                foreach (var method in list) {
                  if (idx < method.Parameters.Count && method.Parameters [idx].Type.Kind == TypeKind.Delegate) {
                    AutoSelect = false;
                    AutoCompleteEmptyMatch = false;
                  }
                }
              }
            }
          }

          if (n != null && n.Parent is ObjectCreateExpression) {
            var invokeResult = ResolveExpression(n.Parent);
            var mgr = invokeResult != null ? invokeResult.Result as ResolveResult : null;
            if (mgr != null) {
              foreach (var constructor in mgr.Type.GetConstructors ()) {
                foreach (var p in constructor.Parameters) {
                  contextList.AddVariable(p);
                }
              }
            }
          }

          if (n is IdentifierExpression) {
            var bop = n.Parent as BinaryOperatorExpression;
            Expression evaluationExpr = null;

            if (bop != null && bop.Right == n && (bop.Operator == BinaryOperatorType.Equality || bop.Operator == BinaryOperatorType.InEquality)) {
              evaluationExpr = bop.Left;
            }
            // check for compare to enum case 
            if (evaluationExpr != null) {
              resolveResult = ResolveExpression(evaluationExpr);
              if (resolveResult != null && resolveResult.Result.Type.Kind == TypeKind.Enum) {
                var wrapper = new CompletionDataWrapper(this);
                AddContextCompletion(
                  wrapper,
                  resolveResult.Resolver,
                  evaluationExpr
                );
                AddEnumMembers(wrapper, resolveResult.Result.Type, resolveResult.Resolver);
                AutoCompleteEmptyMatch = false;
                return wrapper.Result;
              }
            }
          }

          if (n is Identifier && n.Parent is ForeachStatement) {
            if (controlSpace) {
              return DefaultControlSpaceItems(ref isComplete);
            }
            return null;
          }

          if (n is ArrayInitializerExpression) {
            // check for new [] {...} expression -> no need to resolve the type there
            var parent = n.Parent as ArrayCreateExpression;
            if (parent != null && parent.Type.IsNull) {
              return DefaultControlSpaceItems(ref isComplete);
            }

            var initalizerResult = ResolveExpression(n.Parent);

            var concreteNode = identifierStart.Unit.GetNodeAt<IdentifierExpression>(location);
            // check if we're on the right side of an initializer expression
            if (concreteNode != null && concreteNode.Parent != null && concreteNode.Parent.Parent != null && concreteNode.Identifier != "a" && concreteNode.Parent.Parent is NamedExpression) {
              return DefaultControlSpaceItems(ref isComplete);
            }
            if (initalizerResult != null && initalizerResult.Result.Type.Kind != TypeKind.Unknown) { 

              foreach (var property in initalizerResult.Result.Type.GetProperties ()) {
                if (!property.IsPublic) {
                  continue;
                }
                var data = contextList.AddMember(property);
                if (data != null)
                  data.DisplayFlags |= DisplayFlags.NamedArgument;
              }
              foreach (var field in initalizerResult.Result.Type.GetFields ()) {       
                if (!field.IsPublic) {
                  continue;
                }
                var data = contextList.AddMember(field);
                if (data != null)
                  data.DisplayFlags |= DisplayFlags.NamedArgument;
              }
              return contextList.Result;
            }
            return DefaultControlSpaceItems(ref isComplete);
          }

          if (IsAttributeContext(n)) {
            // add attribute targets
            if (currentType == null) {
              contextList.AddCustom("assembly");
              contextList.AddCustom("module");
              contextList.AddCustom("type");
            } else {
              contextList.AddCustom("param");
              contextList.AddCustom("field");
              contextList.AddCustom("property");
              contextList.AddCustom("method");
              contextList.AddCustom("event");
            }
            contextList.AddCustom("return");
          }
          if (n is MemberType) {
            resolveResult = ResolveExpression(
              ((MemberType)n).Target
            );
            return CreateTypeAndNamespaceCompletionData(
              location,
              resolveResult.Result,
              ((MemberType)n).Target,
              resolveResult.Resolver
            );
          }
          if (n != null/*          && !(identifierStart.Item2 is TypeDeclaration)*/) {
            csResolver = new CSharpResolver(ctx);
            var nodes = new List<AstNode>();
            nodes.Add(n);
            if (n.Parent is ICSharpCode.NRefactory.CSharp.Attribute) {
              nodes.Add(n.Parent);
            }
            var astResolver = CompletionContextProvider.GetResolver(csResolver, identifierStart.Unit);
            astResolver.ApplyNavigator(new NodeListResolveVisitorNavigator(nodes));
            try {
              csResolver = astResolver.GetResolverStateBefore(n);
            } catch (Exception) {
              csResolver = GetState();
            }
            // add attribute properties.
            if (n.Parent is ICSharpCode.NRefactory.CSharp.Attribute) {
              var rr = ResolveExpression(n.Parent);
              if (rr != null)
                AddAttributeProperties(contextList, rr.Result);
            }
          } else {
            csResolver = GetState();
          }
          // identifier has already started with the first letter
          offset--;
          AddContextCompletion(
            contextList,
            csResolver,
            identifierStart.Node
          );
          return contextList.Result;
          //        if (stub.Parent is BlockStatement)

          //        result = FindExpression (dom, completionContext, -1);
          //        if (result == null)
          //          return null;
          //         else if (result.ExpressionContext != ExpressionContext.IdentifierExpected) {
          //          triggerWordLength = 1;
          //          bool autoSelect = true;
          //          IType returnType = null;
          //          if ((prevCh == ',' || prevCh == '(') && GetParameterCompletionCommandOffset (out cpos)) {
          //            ctx = CompletionWidget.CreateCodeCompletionContext (cpos);
          //            NRefactoryParameterDataProvider dataProvider = ParameterCompletionCommand (ctx) as NRefactoryParameterDataProvider;
          //            if (dataProvider != null) {
          //              int i = dataProvider.GetCurrentParameterIndex (CompletionWidget, ctx) - 1;
          //              foreach (var method in dataProvider.Methods) {
          //                if (i < method.Parameters.Count) {
          //                  returnType = dom.GetType (method.Parameters [i].ReturnType);
          //                  autoSelect = returnType == null || returnType.ClassType != ClassType.Delegate;
          //                  break;
          //                }
          //              }
          //            }
          //          }
          //          // Bug 677531 - Auto-complete doesn't always highlight generic parameter in method signature
          //          //if (result.ExpressionContext == ExpressionContext.TypeName)
          //          //  autoSelect = false;
          //          CompletionDataList dataList = CreateCtrlSpaceCompletionData (completionContext, result);
          //          AddEnumMembers (dataList, returnType);
          //          dataList.AutoSelect = autoSelect;
          //          return dataList;
          //        } else {
          //          result = FindExpression (dom, completionContext, 0);
          //          tokenIndex = offset;
          //          
          //          // check foreach case, unfortunately the expression finder is too dumb to handle full type names
          //          // should be overworked if the expression finder is replaced with a mcs ast based analyzer.
          //          var possibleForeachToken = GetPreviousToken (ref tokenIndex, false); // starting letter
          //          possibleForeachToken = GetPreviousToken (ref tokenIndex, false); // varname
          //        
          //          // read return types to '(' token
          //          possibleForeachToken = GetPreviousToken (ref tokenIndex, false); // varType
          //          if (possibleForeachToken == ">") {
          //            while (possibleForeachToken != null && possibleForeachToken != "(") {
          //              possibleForeachToken = GetPreviousToken (ref tokenIndex, false);
          //            }
          //          } else {
          //            possibleForeachToken = GetPreviousToken (ref tokenIndex, false); // (
          //            if (possibleForeachToken == ".")
          //              while (possibleForeachToken != null && possibleForeachToken != "(")
          //                possibleForeachToken = GetPreviousToken (ref tokenIndex, false);
          //          }
          //          possibleForeachToken = GetPreviousToken (ref tokenIndex, false); // foreach
          //        
          //          if (possibleForeachToken == "foreach") {
          //            result.ExpressionContext = ExpressionContext.ForeachInToken;
          //          } else {
          //            return null;
          //            //                result.ExpressionContext = ExpressionContext.IdentifierExpected;
          //          }
          //          result.Expression = "";
          //          result.Region = DomRegion.Empty;
          //        
          //          return CreateCtrlSpaceCompletionData (completionContext, result);
          //        }
          //        break;
      }
      return null;

    }

    IEnumerable<ICompletionData> HandleCatchClauseType(ExpressionResult identifierStart)
    {
      Func<IType, IType> typePred = delegate (IType type) {
        if (type.GetAllBaseTypes().Any(t => t.ReflectionName == "System.Exception"))
          return type;
        return null;
      };
      if (identifierStart.Node.Parent is CatchClause) {
        var wrapper = new CompletionDataWrapper(this);
        AddTypesAndNamespaces(
          wrapper,
          GetState(),
          identifierStart.Node,
          typePred,
          m => false
        );
        return wrapper.Result;
      }

      var resolveResult = ResolveExpression(identifierStart);
      return CreateCompletionData(
        location,
        resolveResult.Result,
        identifierStart.Node,
        resolveResult.Resolver,
        typePred
      );
    }

    string[] validEnumBaseTypes = {
      "byte",
      "sbyte",
      "short",
      "int",
      "long",
      "ushort",
      "uint",
      "ulong"
    };

    IEnumerable<ICompletionData> HandleEnumContext()
    {
      var syntaxTree = ParseStub("a", false);
      if (syntaxTree == null) {
        return null;
      }

      var curType = syntaxTree.GetNodeAt<TypeDeclaration>(location);
      if (curType == null || curType.ClassType != ClassType.Enum) {
        syntaxTree = ParseStub("a {}", false);
        var node = syntaxTree.GetNodeAt<AstType>(location);
        if (node != null) {
          var wrapper = new CompletionDataWrapper(this);
          AddKeywords(wrapper, validEnumBaseTypes);
          return wrapper.Result;
        }
      }

      var member = syntaxTree.GetNodeAt<EnumMemberDeclaration>(location);
      if (member != null && member.NameToken.EndLocation < location) {
        if (currentMember == null && currentType != null) {
          foreach (var a in currentType.Members)
            if (a.Region.Begin < location && (currentMember == null || a.Region.Begin > currentMember.Region.Begin))
              currentMember = a;
        }
        bool isComplete = false;
        return DefaultControlSpaceItems(ref isComplete);
      }

      var attribute = syntaxTree.GetNodeAt<Attribute>(location);
      if (attribute != null) {
        var contextList = new CompletionDataWrapper(this);
        var astResolver = CompletionContextProvider.GetResolver(GetState(), syntaxTree);
        var csResolver = astResolver.GetResolverStateBefore(attribute);
        AddContextCompletion(
          contextList,
          csResolver,
          attribute
        );
        return contextList.Result;
      }
      return null;
    }

    bool IsInLinqContext(int offset)
    {
      string token;
      while (null != (token = GetPreviousToken(ref offset, true)) && !IsInsideCommentStringOrDirective()) {

        if (token == "from") {
          return !IsInsideCommentStringOrDirective(offset);
        }
        if (token == ";" || token == "{") {
          return false;
        }
      }
      return false;
    }

    IEnumerable<ICompletionData> HandleAccessorContext()
    {
      var unit = ParseStub("get; }", false);
      var node = unit.GetNodeAt(location, cn => !(cn is CSharpTokenNode));
      if (node is Accessor) {
        node = node.Parent;
      }
      var contextList = new CompletionDataWrapper(this);
      if (node is PropertyDeclaration || node is IndexerDeclaration) {
        if (IncludeKeywordsInCompletionList) {
          contextList.AddCustom("get");
          contextList.AddCustom("set");
          AddKeywords(contextList, accessorModifierKeywords);
        }
      } else if (node is CustomEventDeclaration) {
        if (IncludeKeywordsInCompletionList) {
          contextList.AddCustom("add");
          contextList.AddCustom("remove");
        }
      } else {
        return null;
      }

      return contextList.Result;
    }

    class IfVisitor :DepthFirstAstVisitor
    {
      TextLocation loc;
      ICompletionContextProvider completionContextProvider;
      public bool IsValid;

      public IfVisitor(TextLocation loc, ICompletionContextProvider completionContextProvider)
      {
        this.loc = loc;
        this.completionContextProvider = completionContextProvider;

        this.IsValid = true;
      }

      void Check(string argument)
      {
        // TODO: evaluate #if epressions
        if (argument.Any(c => !(char.IsLetterOrDigit(c) || c == '_')))
          return;
        IsValid &= completionContextProvider.ConditionalSymbols.Contains(argument);
      }

      Stack<PreProcessorDirective> ifStack = new Stack<PreProcessorDirective>();

      public override void VisitPreProcessorDirective(PreProcessorDirective preProcessorDirective)
      {
        if (preProcessorDirective.Type == PreProcessorDirectiveType.If) {
          ifStack.Push(preProcessorDirective);
        } else if (preProcessorDirective.Type == PreProcessorDirectiveType.Endif) {
          if (ifStack.Count == 0)
            return;
          var ifDirective = ifStack.Pop();
          if (ifDirective.StartLocation < loc && loc < preProcessorDirective.EndLocation) {
            Check(ifDirective.Argument);
          }

        }

        base.VisitPreProcessorDirective(preProcessorDirective);
      }

      public void End()
      {
        while (ifStack.Count > 0) {
          Check(ifStack.Pop().Argument);
        }
      }
    }

    IEnumerable<ICompletionData> DefaultControlSpaceItems(ref bool isComplete, ExpressionResult xp = null, bool controlSpace = true)
    {
      var wrapper = new CompletionDataWrapper(this);
      if (offset >= document.TextLength) {
        offset = document.TextLength - 1;
      }
      while (offset > 1 && char.IsWhiteSpace(document.GetCharAt(offset))) {
        offset--;
      }
      location = document.GetLocation(offset);

      if (xp == null) {
        xp = GetExpressionAtCursor();
      }
      AstNode node;
      SyntaxTree unit;
      ExpressionResolveResult rr;
      if (xp != null) {
        node = xp.Node;
        rr = ResolveExpression(node);
        unit = xp.Unit;
      } else {
        unit = ParseStub("foo", false);
        node = unit.GetNodeAt(
          location.Line,
          location.Column + 2,
          n => n is Expression || n is AstType || n is NamespaceDeclaration || n is Attribute
        );
        rr = ResolveExpression(node);
      }
      var ifvisitor = new IfVisitor(location, CompletionContextProvider);
      unit.AcceptVisitor(ifvisitor);
      ifvisitor.End();
      if (!ifvisitor.IsValid)
        return null;
      // namespace name case
      var ns = node as NamespaceDeclaration;
      if (ns != null) {
        var last = ns.NamespaceName;
        if (last != null && location < last.EndLocation)
          return null;
      }
      if (node is Identifier && node.Parent is ForeachStatement) {
        var foreachStmt = (ForeachStatement)node.Parent;
        foreach (var possibleName in GenerateNameProposals (foreachStmt.VariableType)) {
          if (possibleName.Length > 0) {
            wrapper.Result.Add(factory.CreateLiteralCompletionData(possibleName.ToString()));
          }
        }

        AutoSelect = false;
        AutoCompleteEmptyMatch = false;
        isComplete = true;
        return wrapper.Result;
      }

      if (node is Identifier && node.Parent is ParameterDeclaration) {
        if (!controlSpace) {
          return null;
        }
        // Try Parameter name case 
        var param = node.Parent as ParameterDeclaration;
        if (param != null) {
          foreach (var possibleName in GenerateNameProposals (param.Type)) {
            if (possibleName.Length > 0) {
              wrapper.Result.Add(factory.CreateLiteralCompletionData(possibleName.ToString()));
            }
          }
          AutoSelect = false;
          AutoCompleteEmptyMatch = false;
          isComplete = true;
          return wrapper.Result;
        }
      }
      var pDecl = node as ParameterDeclaration;
      if (pDecl != null && pDecl.Parent is LambdaExpression) {
        return null;
      }
      /*            if (Unit != null && (node == null || node is TypeDeclaration)) {
        var constructor = Unit.GetNodeAt<ConstructorDeclaration>(
          location.Line,
          location.Column - 3
        );
        if (constructor != null && !constructor.ColonToken.IsNull && constructor.Initializer.IsNull) {
          wrapper.AddCustom("this");
          wrapper.AddCustom("base");
          return wrapper.Result;
        }
      }*/

      var initializer = node != null ? node.Parent as ArrayInitializerExpression : null;
      if (initializer != null) {
        var result = HandleObjectInitializer(unit, initializer);
        if (result != null)
          return result;
      }
      CSharpResolver csResolver = null;
      if (rr != null) {
        csResolver = rr.Resolver;
      }

      if (csResolver == null) {
        if (node != null) {
          csResolver = GetState();
          //var astResolver = new CSharpAstResolver (csResolver, node, xp != null ? xp.Item1 : CSharpUnresolvedFile);

          try {
            //csResolver = astResolver.GetResolverStateBefore (node);
            Console.WriteLine(csResolver.LocalVariables.Count());
          } catch (Exception  e) {
            Console.WriteLine("E!!!" + e);
          }

        } else {
          csResolver = GetState();
        }
      }

      if (node is Attribute) {
        // add attribute properties.
        var astResolver = CompletionContextProvider.GetResolver(csResolver, unit);
        var resolved = astResolver.Resolve(node);
        AddAttributeProperties(wrapper, resolved);
      }


      if (node == null) {
        // try lambda
        unit = ParseStub("foo) => {}", true);
        var pd = unit.GetNodeAt<ParameterDeclaration>(
          location.Line,
          location.Column
        );
        if (pd != null) {
          var astResolver = unit != null ? CompletionContextProvider.GetResolver(GetState(), unit) : null;
          var parameterType = astResolver.Resolve(pd.Type);
          // Type <name> is always a name context -> return null
          if (parameterType != null && !parameterType.IsError)
            return null;
        }
      }

      AddContextCompletion(wrapper, csResolver, node);

      return wrapper.Result;
    }

    static void AddAttributeProperties(CompletionDataWrapper wrapper, ResolveResult resolved)
    {
      if (resolved == null || resolved.Type.Kind == TypeKind.Unknown)
        return;

      foreach (var property in resolved.Type.GetProperties (p => p.Accessibility == Accessibility.Public)) {
        var data = wrapper.AddMember(property);
        if (data != null)
          data.DisplayFlags |= DisplayFlags.NamedArgument;
      }
      foreach (var field in resolved.Type.GetFields (p => p.Accessibility == Accessibility.Public)) {
        var data = wrapper.AddMember(field);
        if (data != null)
          data.DisplayFlags |= DisplayFlags.NamedArgument;
      }
      foreach (var constructor in resolved.Type.GetConstructors (p => p.Accessibility == Accessibility.Public)) {
        foreach (var p in constructor.Parameters) {
          wrapper.AddNamedParameterVariable(p);
        }
      }
    }

    void AddContextCompletion(CompletionDataWrapper wrapper, CSharpResolver state, AstNode node)
    {
      int i = offset - 1;
      var isInGlobalDelegate = node == null && state.CurrentTypeDefinition == null && GetPreviousToken(ref i, true) == "delegate";

      if (state != null && !(node is AstType)) {
        foreach (var variable in state.LocalVariables) {
          if (variable.Region.IsInside(location.Line, location.Column - 1)) {
            continue;
          }
          wrapper.AddVariable(variable);
        }
      }

      if (state.CurrentMember is IParameterizedMember && !(node is AstType)) {
        var param = (IParameterizedMember)state.CurrentMember;
        foreach (var p in param.Parameters) {
          wrapper.AddVariable(p);
        }
      }

      if (state.CurrentMember is IMethod) {
        var method = (IMethod)state.CurrentMember;
        foreach (var p in method.TypeParameters) {
          wrapper.AddTypeParameter(p);
        }
      }

      Func<IType, IType> typePred = null;
      if (IsAttributeContext(node)) {
        var attribute = Compilation.FindType(KnownTypeCode.Attribute);
        typePred = t => t.GetAllBaseTypeDefinitions().Any(bt => bt.Equals(attribute)) ? t : null;
      }
      if (node != null && node.Role == Roles.BaseType) {
        typePred = t => {
          var def = t.GetDefinition();
          if (def != null && t.Kind != TypeKind.Interface && (def.IsSealed || def.IsStatic))
            return null;
          return t;
        };
      }

      if (node != null && !(node is NamespaceDeclaration) || state.CurrentTypeDefinition != null || isInGlobalDelegate) {
        AddTypesAndNamespaces(wrapper, state, node, typePred);

        wrapper.Result.Add(factory.CreateLiteralCompletionData("global"));
      }

      if (!(node is AstType)) {
        if (currentMember != null || node is Expression) {
          AddKeywords(wrapper, statementStartKeywords);
          if (LanguageVersion.Major >= 5)
            AddKeywords(wrapper, new [] { "await" });
          AddKeywords(wrapper, expressionLevelKeywords);
          if (node == null || node is TypeDeclaration)
            AddKeywords(wrapper, typeLevelKeywords);
        } else if (currentType != null) {
          AddKeywords(wrapper, typeLevelKeywords);
        } else {
          if (!isInGlobalDelegate && !(node is Attribute))
            AddKeywords(wrapper, globalLevelKeywords);
        }
        var prop = currentMember as IUnresolvedProperty;
        if (prop != null && prop.Setter != null && prop.Setter.Region.IsInside(location)) {
          wrapper.AddCustom("value");
        } 
        if (currentMember is IUnresolvedEvent) {
          wrapper.AddCustom("value");
        } 

        if (IsInSwitchContext(node)) {
          if (IncludeKeywordsInCompletionList)
            wrapper.AddCustom("case"); 
        }
      } else {
        if (((AstType)node).Parent is ParameterDeclaration) {
          AddKeywords(wrapper, parameterTypePredecessorKeywords);
        }
      }

      if (node != null || state.CurrentTypeDefinition != null || isInGlobalDelegate)
        AddKeywords(wrapper, primitiveTypesKeywords);
      if (currentMember != null && (node is IdentifierExpression || node is SimpleType) && (node.Parent is ExpressionStatement || node.Parent is ForeachStatement || node.Parent is UsingStatement)) {
        if (IncludeKeywordsInCompletionList) {
          wrapper.AddCustom("var");
          wrapper.AddCustom("dynamic");
        }
      } 
      wrapper.Result.AddRange(factory.CreateCodeTemplateCompletionData());
      if (node != null && node.Role == Roles.Argument) {
        var resolved = ResolveExpression(node.Parent);
        var invokeResult = resolved != null ? resolved.Result as CSharpInvocationResolveResult : null;
        if (invokeResult != null) {
          int argNum = 0;
          foreach (var arg in node.Parent.Children.Where (c => c.Role == Roles.Argument)) {
            if (arg == node) {
              break;
            }
            argNum++;
          }
          var param = argNum < invokeResult.Member.Parameters.Count ? invokeResult.Member.Parameters [argNum] : null;
          if (param != null && param.Type.Kind == TypeKind.Enum) {
            AddEnumMembers(wrapper, param.Type, state);
          }
        }
      }

      if (node is Expression) {
        var root = node;
        while (root.Parent != null)
          root = root.Parent;
        var astResolver = CompletionContextProvider.GetResolver(state, root);
        foreach (var type in TypeGuessing.GetValidTypes(astResolver, (Expression)node)) {
          if (type.Kind == TypeKind.Enum) {
            AddEnumMembers(wrapper, type, state);
          } else if (type.Kind == TypeKind.Delegate) {
            AddDelegateHandlers(wrapper, type, false, true);
            AutoSelect = false;
            AutoCompleteEmptyMatch = false;
          }
        }
      }

      // Add 'this' keyword for first parameter (extension method case)
      if (node != null && node.Parent is ParameterDeclaration &&
        node.Parent.PrevSibling != null && node.Parent.PrevSibling.Role == Roles.LPar && IncludeKeywordsInCompletionList) {
        wrapper.AddCustom("this");
      }
    }

    static bool IsInSwitchContext(AstNode node)
    {
      var n = node;
      while (n != null && !(n is EntityDeclaration)) {
        if (n is SwitchStatement) {
          return true;
        }
        if (n is BlockStatement) {
          return false;
        }
        n = n.Parent;
      }
      return false;
    }

    static bool ListEquals(List<INamespace> curNamespaces, List<INamespace> oldNamespaces)
    {
      if (oldNamespaces == null || curNamespaces.Count != oldNamespaces.Count)
        return false;
      for (int i = 0; i < curNamespaces.Count; i++) {
        if (curNamespaces [i].FullName != oldNamespaces [i].FullName) {
          return false;
        }
      }
      return true;
    }

    void AddTypesAndNamespaces(CompletionDataWrapper wrapper, CSharpResolver state, AstNode node, Func<IType, IType> typePred = null, Predicate<IMember> memberPred = null, Action<ICompletionData, IType> callback = null, bool onlyAddConstructors = false)
    {
      var lookup = new MemberLookup(ctx.CurrentTypeDefinition, Compilation.MainAssembly);

      if (currentType != null) {
        for (var ct = ctx.CurrentTypeDefinition; ct != null; ct = ct.DeclaringTypeDefinition) {
          foreach (var nestedType in ct.GetNestedTypes ()) {
            if (!lookup.IsAccessible(nestedType.GetDefinition(), true))
              continue;
            if (onlyAddConstructors) {
              if (!nestedType.GetConstructors().Any(c => lookup.IsAccessible(c, true)))
                continue;
            }

            if (typePred == null) {
              if (onlyAddConstructors)
                wrapper.AddConstructors(nestedType, false, IsAttributeContext(node));
              else
                wrapper.AddType(nestedType, false, IsAttributeContext(node));
              continue;
            }

            var type = typePred(nestedType);
            if (type != null) {
              var a2 = onlyAddConstructors ? wrapper.AddConstructors(type, false, IsAttributeContext(node)) : wrapper.AddType(type, false, IsAttributeContext(node));
              if (a2 != null && callback != null) {
                callback(a2, type);
              }
            }
            continue;
          }
        }

        if (this.currentMember != null && !(node is AstType)) {
          var def = ctx.CurrentTypeDefinition;
          if (def == null && currentType != null)
            def = Compilation.MainAssembly.GetTypeDefinition(currentType.FullTypeName);
          if (def != null) {
            bool isProtectedAllowed = true;

            foreach (var member in def.GetMembers (m => currentMember.IsStatic ? m.IsStatic : true)) {
              if (member is IMethod && ((IMethod)member).FullName == "System.Object.Finalize") {
                continue;
              }
              if (member.SymbolKind == SymbolKind.Operator) {
                continue;
              }
              if (member.IsExplicitInterfaceImplementation) {
                continue;
              }
              if (!lookup.IsAccessible(member, isProtectedAllowed)) {
                continue;
              }
              if (memberPred == null || memberPred(member)) {
                wrapper.AddMember(member);
              }
            }
            var declaring = def.DeclaringTypeDefinition;
            while (declaring != null) {
              foreach (var member in declaring.GetMembers (m => m.IsStatic)) {
                if (memberPred == null || memberPred(member)) {
                  wrapper.AddMember(member);
                }
              }
              declaring = declaring.DeclaringTypeDefinition;
            }
          }
        }
        if (ctx.CurrentTypeDefinition != null) {
          foreach (var p in ctx.CurrentTypeDefinition.TypeParameters) {
            wrapper.AddTypeParameter(p);
          }
        }
      }
      var scope = ctx.CurrentUsingScope;

      for (var n = scope; n != null; n = n.Parent) {
        foreach (var pair in n.UsingAliases) {
          wrapper.AddAlias(pair.Key);
        }
        foreach (var alias in n.ExternAliases) {
          wrapper.AddAlias(alias);
        }
        foreach (var u in n.Usings) {
          foreach (var type in u.Types) {
            if (!lookup.IsAccessible(type, false))
              continue;

            IType addType = typePred != null ? typePred(type) : type;

            if (onlyAddConstructors && addType != null) {
              if (!addType.GetConstructors().Any(c => lookup.IsAccessible(c, true)))
                continue;
            }

            if (addType != null) {
              var a = onlyAddConstructors ? wrapper.AddConstructors(addType, false, IsAttributeContext(node)) : wrapper.AddType(addType, false, IsAttributeContext(node));
              if (a != null && callback != null) {
                callback(a, type);
              }
            }
          }
        }

        foreach (var type in n.Namespace.Types) {
          if (!lookup.IsAccessible(type, false))
            continue;
          IType addType = typePred != null ? typePred(type) : type;
          if (onlyAddConstructors && addType != null) {
            if (!addType.GetConstructors().Any(c => lookup.IsAccessible(c, true)))
              continue;
          }

          if (addType != null) {
            var a2 = onlyAddConstructors ? wrapper.AddConstructors(addType, false, IsAttributeContext(node)) : wrapper.AddType(addType, false);
            if (a2 != null && callback != null) {
              callback(a2, type);
            }
          }
        }
      }

      for (var n = scope; n != null; n = n.Parent) {
        foreach (var curNs in n.Namespace.ChildNamespaces) {
          wrapper.AddNamespace(lookup, curNs);
        }
      }

      if (node is AstType && node.Parent is Constraint && IncludeKeywordsInCompletionList) {
        wrapper.AddCustom("new()");
      }

      if (AutomaticallyAddImports) {
        state = GetState();
        ICompletionData[] importData;

        var namespaces = new List<INamespace>();
        for (var n = ctx.CurrentUsingScope; n != null; n = n.Parent) {
          namespaces.Add(n.Namespace);
          foreach (var u in n.Usings)
            namespaces.Add(u);
        }

        if (this.CompletionEngineCache != null && ListEquals(namespaces, CompletionEngineCache.namespaces)) {
          importData = CompletionEngineCache.importCompletion;
        } else {
          // flatten usings
          var importList = new List<ICompletionData>();
          var dict = new Dictionary<string, Dictionary<string, ICompletionData>>();
          foreach (var type in Compilation.GetTopLevelTypeDefinitons ()) {
            if (!lookup.IsAccessible(type, false))
              continue;
            if (namespaces.Any(n => n.FullName == type.Namespace))
              continue;
            bool useFullName = false;
            foreach (var ns in namespaces) {
              if (ns.GetTypeDefinition(type.Name, type.TypeParameterCount) != null) {
                useFullName = true;
                break;
              }
            }

            if (onlyAddConstructors) {
              if (!type.GetConstructors().Any(c => lookup.IsAccessible(c, true)))
                continue;
            }
            var data = factory.CreateImportCompletionData(type, useFullName, onlyAddConstructors);
            Dictionary<string, ICompletionData> createdDict;
            if (!dict.TryGetValue(type.Name, out createdDict)) {
              createdDict = new Dictionary<string, ICompletionData>();
              dict.Add(type.Name, createdDict);
            }
            ICompletionData oldData;
            if (!createdDict.TryGetValue(type.Namespace, out oldData)) {
              importList.Add(data);
              createdDict.Add(type.Namespace, data);
            } else {
              oldData.AddOverload(data); 
            }
          }

          importData = importList.ToArray();
          if (CompletionEngineCache != null) {
            CompletionEngineCache.namespaces = namespaces;
            CompletionEngineCache.importCompletion = importData;
          }
        }
        foreach (var data in importData) {
          wrapper.Result.Add(data);
        }


      }

    }

    IEnumerable<ICompletionData> HandleKeywordCompletion(int wordStart, string word)
    {
      if (IsInsideCommentStringOrDirective()) {
        if (IsInPreprocessorDirective()) {
          if (word == "if" || word == "elif") {
            if (wordStart > 0 && document.GetCharAt(wordStart - 1) == '#') {
              return factory.CreatePreProcessorDefinesCompletionData();
            }
          }
        }
        return null;
      }
      switch (word) {
        case "namespace":
          return null;
        case "using":
          if (currentType != null) {
            return null;
          }
          var wrapper = new CompletionDataWrapper(this);
          AddTypesAndNamespaces(wrapper, GetState(), null, t => null);
          return wrapper.Result;
        case "case":
          return CreateCaseCompletionData(location);
          //        case ",":
          //        case ":":
          //          if (result.ExpressionContext == ExpressionContext.InheritableType) {
          //            IType cls = NRefactoryResolver.GetTypeAtCursor (Document.CompilationUnit, Document.FileName, new TextLocation (completionContext.TriggerLine, completionContext.TriggerLineOffset));
          //            CompletionDataList completionList = new ProjectDomCompletionDataList ();
          //            List<string > namespaceList = GetUsedNamespaces ();
          //            var col = new CSharpTextEditorCompletion.CompletionDataCollector (this, dom, completionList, Document.CompilationUnit, null, location);
          //            bool isInterface = false;
          //            HashSet<string > baseTypeNames = new HashSet<string> ();
          //            if (cls != null) {
          //              baseTypeNames.Add (cls.Name);
          //              if (cls.ClassType == ClassType.Struct)
          //                isInterface = true;
          //            }
          //            int tokenIndex = offset;
          //  
          //            // Search base types " : [Type1, ... ,TypeN,] <Caret>"
          //            string token = null;
          //            do {
          //              token = GetPreviousToken (ref tokenIndex, false);
          //              if (string.IsNullOrEmpty (token))
          //                break;
          //              token = token.Trim ();
          //              if (Char.IsLetterOrDigit (token [0]) || token [0] == '_') {
          //                IType baseType = dom.SearchType (Document.CompilationUnit, cls, result.Region.Start, token);
          //                if (baseType != null) {
          //                  if (baseType.ClassType != ClassType.Interface)
          //                    isInterface = true;
          //                  baseTypeNames.Add (baseType.Name);
          //                }
          //              }
          //            } while (token != ":");
          //            foreach (object o in dom.GetNamespaceContents (namespaceList, true, true)) {
          //              IType type = o as IType;
          //              if (type != null && (type.IsStatic || type.IsSealed || baseTypeNames.Contains (type.Name) || isInterface && type.ClassType != ClassType.Interface)) {
          //                continue;
          //              }
          //              if (o is Namespace && !namespaceList.Any (ns => ns.StartsWith (((Namespace)o).FullName)))
          //                continue;
          //              col.Add (o);
          //            }
          //            // Add inner classes
          //            Stack<IType > innerStack = new Stack<IType> ();
          //            innerStack.Push (cls);
          //            while (innerStack.Count > 0) {
          //              IType curType = innerStack.Pop ();
          //              if (curType == null)
          //                continue;
          //              foreach (IType innerType in curType.InnerTypes) {
          //                if (innerType != cls)
          //                  // don't add the calling class as possible base type
          //                  col.Add (innerType);
          //              }
          //              if (curType.DeclaringType != null)
          //                innerStack.Push (curType.DeclaringType);
          //            }
          //            return completionList;
          //          }
          //          break;
        case "is":
        case "as":
          if (currentType == null) {
            return null;
          }
          IType isAsType = null;
          var isAsExpression = GetExpressionAt(wordStart);
          if (isAsExpression != null) {
            var parent = isAsExpression.Node.Parent;
            if (parent is VariableInitializer) {
              parent = parent.Parent;
            }
            var varDecl = parent as VariableDeclarationStatement;
            if (varDecl != null) {
              ExpressionResolveResult resolved;
              if (varDecl.Type.IsVar()) {
                resolved = null;
              } else {
                resolved = ResolveExpression(parent);
              }
              if (resolved != null) {
                isAsType = resolved.Result.Type;
              }
            }
          }
          var isAsWrapper = new CompletionDataWrapper(this);
          var def = isAsType != null ? isAsType.GetDefinition() : null;
          AddTypesAndNamespaces(
            isAsWrapper,
            GetState(),
            null,
            t => t.GetDefinition() == null || def == null || t.GetDefinition().IsDerivedFrom(def) ? t : null,
            m => false);
          AddKeywords(isAsWrapper, primitiveTypesKeywords);
          return isAsWrapper.Result;
          //          {
          //            CompletionDataList completionList = new ProjectDomCompletionDataList ();
          //            ExpressionResult expressionResult = FindExpression (dom, completionContext, wordStart - document.Caret.Offset);
          //            NRefactoryResolver resolver = CreateResolver ();
          //            ResolveResult resolveResult = resolver.Resolve (expressionResult, new TextLocation (completionContext.TriggerLine, completionContext.TriggerLineOffset));
          //            if (resolveResult != null && resolveResult.ResolvedType != null) {
          //              CompletionDataCollector col = new CompletionDataCollector (this, dom, completionList, Document.CompilationUnit, resolver.CallingType, location);
          //              IType foundType = null;
          //              if (word == "as") {
          //                ExpressionContext exactContext = new NewCSharpExpressionFinder (dom).FindExactContextForAsCompletion (document, Document.CompilationUnit, Document.FileName, resolver.CallingType);
          //                if (exactContext is ExpressionContext.TypeExpressionContext) {
          //                  foundType = resolver.SearchType (((ExpressionContext.TypeExpressionContext)exactContext).Type);
          //                  AddAsCompletionData (col, foundType);
          //                }
          //              }
          //            
          //              if (foundType == null)
          //                foundType = resolver.SearchType (resolveResult.ResolvedType);
          //            
          //              if (foundType != null) {
          //                if (foundType.ClassType == ClassType.Interface)
          //                  foundType = resolver.SearchType (DomReturnType.Object);
          //              
          //                foreach (IType type in dom.GetSubclasses (foundType)) {
          //                  if (type.IsSpecialName || type.Name.StartsWith ("<"))
          //                    continue;
          //                  AddAsCompletionData (col, type);
          //                }
          //              }
          //              List<string > namespaceList = GetUsedNamespaces ();
          //              foreach (object o in dom.GetNamespaceContents (namespaceList, true, true)) {
          //                if (o is IType) {
          //                  IType type = (IType)o;
          //                  if (type.ClassType != ClassType.Interface || type.IsSpecialName || type.Name.StartsWith ("<"))
          //                    continue;
          //  //                if (foundType != null && !dom.GetInheritanceTree (foundType).Any (x => x.FullName == type.FullName))
          //  //                  continue;
          //                  AddAsCompletionData (col, type);
          //                  continue;
          //                }
          //                if (o is Namespace)
          //                  continue;
          //                col.Add (o);
          //              }
          //              return completionList;
          //            }
          //            result.ExpressionContext = ExpressionContext.TypeName;
          //            return CreateCtrlSpaceCompletionData (completionContext, result);
          //          }
        case "override":
          // Look for modifiers, in order to find the beginning of the declaration
          int firstMod = wordStart;
          int i = wordStart;
          for (int n = 0; n < 3; n++) {
            string mod = GetPreviousToken(ref i, true);
            if (mod == "public" || mod == "protected" || mod == "private" || mod == "internal" || mod == "sealed") {
              firstMod = i;
            } else if (mod == "static") {
              // static methods are not overridable
              return null;
            } else {
              break;
            }
          }
          if (!IsLineEmptyUpToEol()) {
            return null;
          }
          if (currentType != null && (currentType.Kind == TypeKind.Class || currentType.Kind == TypeKind.Struct)) {
            string modifiers = document.GetText(firstMod, wordStart - firstMod);
            return GetOverrideCompletionData(currentType, modifiers);
          }
          return null;
        case "partial":
          // Look for modifiers, in order to find the beginning of the declaration
          firstMod = wordStart;
          i = wordStart;
          for (int n = 0; n < 3; n++) {
            string mod = GetPreviousToken(ref i, true);
            if (mod == "public" || mod == "protected" || mod == "private" || mod == "internal" || mod == "sealed") {
              firstMod = i;
            } else if (mod == "static") {
              // static methods are not overridable
              return null;
            } else {
              break;
            }
          }
          if (!IsLineEmptyUpToEol()) {
            return null;
          }
          var state = GetState();

          if (state.CurrentTypeDefinition != null && (state.CurrentTypeDefinition.Kind == TypeKind.Class || state.CurrentTypeDefinition.Kind == TypeKind.Struct)) {
            string modifiers = document.GetText(firstMod, wordStart - firstMod);
            return GetPartialCompletionData(state.CurrentTypeDefinition, modifiers);
          }
          return null;

        case "public":
        case "protected":
        case "private":
        case "internal":
        case "sealed":
        case "static":
          var accessorContext = HandleAccessorContext();
          if (accessorContext != null) {
            return accessorContext;
          }
          return null;
        case "new":
          int j = offset - 4;
          //        string token = GetPreviousToken (ref j, true);

          IType hintType = null;
          var expressionOrVariableDeclaration = GetNewExpressionAt(j);
          if (expressionOrVariableDeclaration == null)
            return null;
          var astResolver = CompletionContextProvider.GetResolver(GetState(), expressionOrVariableDeclaration.Node.Ancestors.FirstOrDefault(n => n is EntityDeclaration || n is SyntaxTree));
          hintType = TypeGuessing.GetValidTypes(
            astResolver,
            expressionOrVariableDeclaration.Node
          ).FirstOrDefault();

          return CreateConstructorCompletionData(hintType);
        case "yield":
          var yieldDataList = new CompletionDataWrapper(this);
          DefaultCompletionString = "return";
          if (IncludeKeywordsInCompletionList) {
            yieldDataList.AddCustom("break");
            yieldDataList.AddCustom("return");
          }
          return yieldDataList.Result;
        case "in":
          var inList = new CompletionDataWrapper(this);

          var expr = GetExpressionAtCursor();
          if (expr == null)
            return null;
          var rr = ResolveExpression(expr);

          AddContextCompletion(
            inList,
            rr != null ? rr.Resolver : GetState(),
            expr.Node
          );
          return inList.Result;
      }
      return null;
    }

    bool IsLineEmptyUpToEol()
    {
      var line = document.GetLineByNumber(location.Line);
      for (int j = offset; j < line.EndOffset; j++) {
        char ch = document.GetCharAt(j);
        if (!char.IsWhiteSpace(ch)) {
          return false;
        }
      }
      return true;
    }

    string GetLineIndent(int lineNr)
    {
      var line = document.GetLineByNumber(lineNr);
      for (int j = line.Offset; j < line.EndOffset; j++) {
        char ch = document.GetCharAt(j);
        if (!char.IsWhiteSpace(ch)) {
          return document.GetText(line.Offset, j - line.Offset);
        }
      }
      return "";
    }
    //    static CSharpAmbience amb = new CSharpAmbience();
    class Category : CompletionCategory
    {
      public Category(string displayText, string icon) : base(displayText, icon)
      {
      }

      public override int CompareTo(CompletionCategory other)
      {
        return 0;
      }
    }

    IEnumerable<ICompletionData> CreateConstructorCompletionData(IType hintType)
    {
      var wrapper = new CompletionDataWrapper(this);
      var state = GetState();
      Func<IType, IType> pred = null;
      Action<ICompletionData, IType> typeCallback = null;
      var inferredTypesCategory = new Category("Inferred Types", null);
      var derivedTypesCategory = new Category("Derived Types", null);

      if (hintType != null && (hintType.Kind != TypeKind.TypeParameter || IsTypeParameterInScope(hintType))) {
        if (hintType.Kind != TypeKind.Unknown) {
          var lookup = new MemberLookup(
            ctx.CurrentTypeDefinition,
            Compilation.MainAssembly
          );
          typeCallback = (data, t) => {
            //check if type is in inheritance tree.
            if (hintType.GetDefinition() != null &&
              t.GetDefinition() != null &&
              t.GetDefinition().IsDerivedFrom(hintType.GetDefinition())) {
              data.CompletionCategory = derivedTypesCategory;
            }
          };
          pred = t => {
            if (t.Kind == TypeKind.Interface && hintType.Kind != TypeKind.Array) {
              return null;
            }
            // check for valid constructors
            if (t.GetConstructors().Any()) {
              bool isProtectedAllowed = currentType != null ? 
                currentType.Resolve(ctx).GetDefinition().IsDerivedFrom(t.GetDefinition()) : false;
              if (!t.GetConstructors().Any(m => lookup.IsAccessible(m, isProtectedAllowed))) {
                return null;
              }
            }

            // check derived types
            var typeDef = t.GetDefinition();
            var hintDef = hintType.GetDefinition();
            if (typeDef != null && hintDef != null && typeDef.IsDerivedFrom(hintDef)) {
              var newType = wrapper.AddType(t, true);
              if (newType != null) {
                newType.CompletionCategory = inferredTypesCategory;
              }
            }

            // check type inference
            var typeInference = new TypeInference(Compilation);
            typeInference.Algorithm = TypeInferenceAlgorithm.ImprovedReturnAllResults;

            var inferedType = typeInference.FindTypeInBounds(new [] { t }, new [] { hintType });
            if (inferedType != SpecialType.UnknownType) {
              var newType = wrapper.AddType(inferedType, true);
              if (newType != null) {
                newType.CompletionCategory = inferredTypesCategory;
              }
              return null;
            }
            return t;
          };
          if (!(hintType.Kind == TypeKind.Interface && hintType.Kind != TypeKind.Array)) {
            var hint = wrapper.AddType(hintType, true);
            if (hint != null) {
              DefaultCompletionString = hint.DisplayText;
              hint.CompletionCategory = derivedTypesCategory;
            }
          }
          if (hintType is ParameterizedType && hintType.TypeParameterCount == 1 && hintType.FullName == "System.Collections.Generic.IEnumerable") {
            var arg = ((ParameterizedType)hintType).TypeArguments.FirstOrDefault();
            if (arg.Kind != TypeKind.TypeParameter) {
              var array = new ArrayType(ctx.Compilation, arg, 1);
              wrapper.AddType(array, true);
            }
          }
        } else {
          var hint = wrapper.AddType(hintType, true);
          if (hint != null) {
            DefaultCompletionString = hint.DisplayText;
            hint.CompletionCategory = derivedTypesCategory;
          }
        }
      } 
      AddTypesAndNamespaces(wrapper, state, null, pred, m => false, typeCallback, true);
      if (hintType == null || hintType == SpecialType.UnknownType) {
        AddKeywords(wrapper, primitiveTypesKeywords.Where(k => k != "void"));
      }

      CloseOnSquareBrackets = true;
      AutoCompleteEmptyMatch = true;
      AutoCompleteEmptyMatchOnCurlyBracket = false;
      return wrapper.Result;
    }

    bool IsTypeParameterInScope(IType hintType)
    {
      var tp = hintType as ITypeParameter;
      var ownerName = tp.Owner.ReflectionName;
      if (currentMember != null && ownerName == currentMember.ReflectionName)
        return true;
      var ot = currentType;
      while (ot != null) {
        if (ownerName == ot.ReflectionName)
          return true;
        ot = ot.DeclaringTypeDefinition;
      }
      return false;
    }

    IEnumerable<ICompletionData> GetOverrideCompletionData(IUnresolvedTypeDefinition type, string modifiers)
    {
      var wrapper = new CompletionDataWrapper(this);
      var alreadyInserted = new List<IMember>();
      //bool addedVirtuals = false;

      int declarationBegin = offset;
      int j = declarationBegin;
      for (int i = 0; i < 3; i++) {
        switch (GetPreviousToken(ref j, true)) {
          case "public":
          case "protected":
          case "private":
          case "internal":
          case "sealed":
          case "override":
          case "partial":
          case "async":
            declarationBegin = j;
            break;
          case "static":
            return null; // don't add override completion for static members
        }
      }
      AddVirtuals(
        alreadyInserted,
        wrapper,
        modifiers,
        type.Resolve(ctx),
        declarationBegin
      );
      return wrapper.Result;
    }

    IEnumerable<ICompletionData> GetPartialCompletionData(ITypeDefinition type, string modifiers)
    {
      var wrapper = new CompletionDataWrapper(this);
      int declarationBegin = offset;
      int j = declarationBegin;
      for (int i = 0; i < 3; i++) {
        switch (GetPreviousToken(ref j, true)) {
          case "public":
          case "protected":
          case "private":
          case "internal":
          case "sealed":
          case "override":
          case "partial":
          case "async":
            declarationBegin = j;
            break;
          case "static":
            return null; // don't add override completion for static members
        }
      }

      var methods = new List<IUnresolvedMethod>();

      foreach (var part in type.Parts) {
        foreach (var method in part.Methods) {
          if (method.BodyRegion.IsEmpty) {
            if (GetImplementation(type, method) != null) {
              continue;
            }
            methods.Add(method);
          }
        } 
      }

      foreach (var method in methods) {
        wrapper.Add(factory.CreateNewPartialCompletionData(
          declarationBegin,
          method.DeclaringTypeDefinition,
          method
        )
        );
      } 

      return wrapper.Result;
    }

    IMethod GetImplementation(ITypeDefinition type, IUnresolvedMethod method)
    {
      foreach (var cur in type.Methods) {
        if (cur.Name == method.Name && cur.Parameters.Count == method.Parameters.Count && !cur.BodyRegion.IsEmpty) {
          bool equal = true;
          /*          for (int i = 0; i < cur.Parameters.Count; i++) {
            if (!cur.Parameters [i].Type.Equals (method.Parameters [i].Type)) {
              equal = false;
              break;
            }
          }*/
          if (equal) {
            return cur;
          }
        }
      }
      return null;
    }

    protected virtual void AddVirtuals(List<IMember> alreadyInserted, CompletionDataWrapper col, string modifiers, IType curType, int declarationBegin)
    {
      if (curType == null) {
        return;
      }
      foreach (var m in curType.GetMembers ().Reverse ()) {
        if (curType.Kind != TypeKind.Interface && !m.IsOverridable) {
          continue;
        }
        // filter out the "Finalize" methods, because finalizers should be done with destructors.
        if (m is IMethod && m.Name == "Finalize") {
          continue;
        }

        var data = factory.CreateNewOverrideCompletionData(
          declarationBegin,
          currentType,
          m
        );
        // check if the member is already implemented
        bool foundMember = curType.GetMembers().Any(cm => SignatureComparer.Ordinal.Equals(
          cm,
          m
        ) && cm.DeclaringTypeDefinition == curType.GetDefinition()
        );
        if (foundMember) {
          continue;
        }
        if (alreadyInserted.Any(cm => SignatureComparer.Ordinal.Equals(cm, m)))
          continue;
        alreadyInserted.Add(m);
        data.CompletionCategory = col.GetCompletionCategory(m.DeclaringTypeDefinition);
        col.Add(data);
      }
    }

    void AddKeywords(CompletionDataWrapper wrapper, IEnumerable<string> keywords)
    {
      if (!IncludeKeywordsInCompletionList)
        return;
      foreach (string keyword in keywords) {
        if (wrapper.Result.Any(data => data.DisplayText == keyword))
          continue;
        wrapper.AddCustom(keyword);
      }
    }

    public string GuessEventHandlerMethodName(int tokenIndex, string surroundingTypeName)
    {
      var names = new List<string>();
      
      string eventName = GetPreviousToken(ref tokenIndex, false);
      string result = GetPreviousToken(ref tokenIndex, false);
      if (result != ".") {
        if (surroundingTypeName == null) {
          eventName = "Handle" + eventName;
        } else {
          names.Add(surroundingTypeName);
        }
      }
      while (result == ".") {
        result = GetPreviousToken(ref tokenIndex, false);
        if (result == "this") {
          if (names.Count == 0) {
            if (surroundingTypeName == null) {
              eventName = "Handle" + eventName;
            } else {
              names.Add(surroundingTypeName);
            }
          }
        } else if (result != null) {
          string trimmedName = result.Trim();
          if (trimmedName.Length == 0) {
            break;
          }
          names.Insert(0, trimmedName);
        }
        result = GetPreviousToken(ref tokenIndex, false);
      }
      if (!string.IsNullOrEmpty(eventName)) {
        names.Add(eventName);
      }
      result = String.Join("_", names.ToArray());
      foreach (char ch in result) {
        if (!char.IsLetterOrDigit(ch) && ch != '_') {
          result = "";
          break;
        }
      }
      return result;
    }

    bool MatchDelegate(IType delegateType, IMethod method)
    {
      if (method.SymbolKind != SymbolKind.Method)
        return false;
      var delegateMethod = delegateType.GetDelegateInvokeMethod();
      if (delegateMethod == null || delegateMethod.Parameters.Count != method.Parameters.Count) {
        return false;
      }

      for (int i = 0; i < delegateMethod.Parameters.Count; i++) {
        if (!delegateMethod.Parameters [i].Type.Equals(method.Parameters [i].Type)) {
          return false;
        }
      }
      return true;
    }

    string AddDelegateHandlers(CompletionDataWrapper completionList, IType delegateType, bool addSemicolon = true, bool addDefault = true, string optDelegateName = null)
    {
      IMethod delegateMethod = delegateType.GetDelegateInvokeMethod();
      PossibleDelegates.Add(delegateMethod);
      var thisLineIndent = GetLineIndent(location.Line);
      string delegateEndString = EolMarker + thisLineIndent + "}" + (addSemicolon ? ";" : "");
      //bool containsDelegateData = completionList.Result.Any(d => d.DisplayText.StartsWith("delegate("));
      if (addDefault && !completionList.AnonymousDelegateAdded) {
        completionList.AnonymousDelegateAdded = true;
        var oldDelegate = completionList.Result.FirstOrDefault(cd => cd.DisplayText == "delegate");
        if (oldDelegate != null)
          completionList.Result.Remove(oldDelegate);
        completionList.AddCustom(
          "delegate",
          "Creates anonymous delegate.",
          "delegate {" + EolMarker + thisLineIndent + IndentString + "|" + delegateEndString
        ).DisplayFlags |= DisplayFlags.MarkedBold;
        if (LanguageVersion.Major >= 5) {
          completionList.AddCustom(
            "async delegate",
            "Creates anonymous async delegate.",
            "async delegate {" + EolMarker + thisLineIndent + IndentString + "|" + delegateEndString
          ).DisplayFlags |= DisplayFlags.MarkedBold;
        }
      }
      var sb = new StringBuilder("(");
      var sbWithoutTypes = new StringBuilder("(");
      var state = GetState();
      var builder = new TypeSystemAstBuilder(state);

      for (int k = 0; k < delegateMethod.Parameters.Count; k++) {

        if (k > 0) {
          sb.Append(", ");
          sbWithoutTypes.Append(", ");
        }
        var convertedParameter = builder.ConvertParameter(delegateMethod.Parameters [k]);
        if (convertedParameter.ParameterModifier == ParameterModifier.Params)
          convertedParameter.ParameterModifier = ParameterModifier.None;
        sb.Append(convertedParameter.ToString(FormattingPolicy));
        sbWithoutTypes.Append(delegateMethod.Parameters [k].Name);
      }

      sb.Append(")");
      sbWithoutTypes.Append(")");
      var signature = sb.ToString();
      if (!completionList.HasAnonymousDelegateAdded(signature)) {
        completionList.AddAnonymousDelegateAdded(signature);

        completionList.AddCustom(
          "delegate" + signature,
          "Creates anonymous delegate.",
          "delegate" + signature + " {" + EolMarker + thisLineIndent + IndentString + "|" + delegateEndString
        ).DisplayFlags |= DisplayFlags.MarkedBold;
        if (LanguageVersion.Major >= 5) {
          completionList.AddCustom(
            "async delegate" + signature,
            "Creates anonymous async delegate.",
            "async delegate" + signature + " {" + EolMarker + thisLineIndent + IndentString + "|" + delegateEndString
          ).DisplayFlags |= DisplayFlags.MarkedBold;
        }
        if (!completionList.Result.Any(data => data.DisplayText == sb.ToString())) {
          completionList.AddCustom(
            signature,
            "Creates typed lambda expression.",
            signature + " => |" + (addSemicolon ? ";" : "")
          ).DisplayFlags |= DisplayFlags.MarkedBold;
          if (LanguageVersion.Major >= 5) {
            completionList.AddCustom(
              "async " + signature,
              "Creates typed async lambda expression.",
              "async " + signature + " => |" + (addSemicolon ? ";" : "")
            ).DisplayFlags |= DisplayFlags.MarkedBold;
          }

          if (!delegateMethod.Parameters.Any(p => p.IsOut || p.IsRef) && !completionList.Result.Any(data => data.DisplayText == sbWithoutTypes.ToString())) {
            completionList.AddCustom(
              sbWithoutTypes.ToString(),
              "Creates lambda expression.",
              sbWithoutTypes + " => |" + (addSemicolon ? ";" : "")
            ).DisplayFlags |= DisplayFlags.MarkedBold;
            if (LanguageVersion.Major >= 5) {
              completionList.AddCustom(
                "async " + sbWithoutTypes,
                "Creates async lambda expression.",
                "async " + sbWithoutTypes + " => |" + (addSemicolon ? ";" : "")
              ).DisplayFlags |= DisplayFlags.MarkedBold;
            }
          }
        }

      }

      string varName = optDelegateName ?? "Handle" + delegateType.Name;

      var ecd = factory.CreateEventCreationCompletionData(varName, delegateType, null, signature, currentMember, currentType);
      ecd.DisplayFlags |= DisplayFlags.MarkedBold;
      completionList.Add(ecd);

      return sb.ToString();
    }

    bool IsAccessibleFrom(IEntity member, ITypeDefinition calledType, IMember currentMember, bool includeProtected)
    {
      if (currentMember == null) {
        return member.IsStatic || member.IsPublic;
      }
      //      if (currentMember is MonoDevelop.Projects.Dom.BaseResolveResult.BaseMemberDecorator) 
      //        return member.IsPublic | member.IsProtected;
      //    if (member.IsStatic && !IsStatic)
      //      return false;
      if (member.IsPublic || calledType != null && calledType.Kind == TypeKind.Interface && !member.IsProtected) {
        return true;
      }
      if (member.DeclaringTypeDefinition != null) {
        if (member.DeclaringTypeDefinition.Kind == TypeKind.Interface) { 
          return IsAccessibleFrom(
            member.DeclaringTypeDefinition,
            calledType,
            currentMember,
            includeProtected
          );
        }

        if (member.IsProtected && !(member.DeclaringTypeDefinition.IsProtectedOrInternal && !includeProtected)) {
          return includeProtected;
        }
      }
      if (member.IsInternal || member.IsProtectedAndInternal || member.IsProtectedOrInternal) {
        //var type1 = member is ITypeDefinition ? (ITypeDefinition)member : member.DeclaringTypeDefinition;
        //var type2 = currentMember is ITypeDefinition ? (ITypeDefinition)currentMember : currentMember.DeclaringTypeDefinition;
        bool result = true;
        // easy case, projects are the same
        /*        //        if (type1.ProjectContent == type2.ProjectContent) {
        //          result = true; 
        //        } else 
        if (type1.ProjectContent != null) {
          // maybe type2 hasn't project dom set (may occur in some cases), check if the file is in the project
          //TODO !!
          //          result = type1.ProjectContent.Annotation<MonoDevelop.Projects.Project> ().GetProjectFile (type2.Region.FileName) != null;
          result = false;
        } else if (type2.ProjectContent != null) {
          //TODO!!
          //          result = type2.ProjectContent.Annotation<MonoDevelop.Projects.Project> ().GetProjectFile (type1.Region.FileName) != null;
          result = false;
        } else {
          // should never happen !
          result = true;
        }*/
        return member.IsProtectedAndInternal ? includeProtected && result : result;
      }

      if (!(currentMember is IType) && (currentMember.DeclaringTypeDefinition == null || member.DeclaringTypeDefinition == null)) {
        return false;
      }

      // inner class 
      var declaringType = currentMember.DeclaringTypeDefinition;
      while (declaringType != null) {
        if (declaringType.ReflectionName == currentMember.DeclaringType.ReflectionName) {
          return true;
        }
        declaringType = declaringType.DeclaringTypeDefinition;
      }


      return currentMember.DeclaringTypeDefinition != null && member.DeclaringTypeDefinition.FullName == currentMember.DeclaringTypeDefinition.FullName;
    }

    static bool IsAttributeContext(AstNode node)
    {
      AstNode n = node;
      while (n is AstType) {
        n = n.Parent;
      }
      return n is Attribute;
    }

    IEnumerable<ICompletionData> CreateTypeAndNamespaceCompletionData(TextLocation location, ResolveResult resolveResult, AstNode resolvedNode, CSharpResolver state)
    {
      if (resolveResult == null || resolveResult.IsError) {
        return null;
      }
      var exprParent = resolvedNode.GetParent<Expression>();
      var unit = exprParent != null ? exprParent.GetParent<SyntaxTree>() : null;

      var astResolver = unit != null ? CompletionContextProvider.GetResolver(state, unit) : null;
      IType hintType = exprParent != null && astResolver != null ? 
        TypeGuessing.GetValidTypes(astResolver, exprParent).FirstOrDefault() :
        null;
      var result = new CompletionDataWrapper(this);
      var lookup = new MemberLookup(
        ctx.CurrentTypeDefinition,
        Compilation.MainAssembly
      );
      if (resolveResult is NamespaceResolveResult) {
        var nr = (NamespaceResolveResult)resolveResult;
        if (!(resolvedNode.Parent is UsingDeclaration || resolvedNode.Parent != null && resolvedNode.Parent.Parent is UsingDeclaration)) {
          foreach (var cl in nr.Namespace.Types) {
            if (hintType != null && hintType.Kind != TypeKind.Array && cl.Kind == TypeKind.Interface) {
              continue;
            }
            if (!lookup.IsAccessible(cl, false))
              continue;
            result.AddType(cl, false, IsAttributeContext(resolvedNode));
          }
        }
        foreach (var ns in nr.Namespace.ChildNamespaces) {
          result.AddNamespace(lookup, ns);
        }
      } else if (resolveResult is TypeResolveResult) {
        var type = resolveResult.Type;
        foreach (var nested in type.GetNestedTypes ()) {
          if (hintType != null && hintType.Kind != TypeKind.Array && nested.Kind == TypeKind.Interface) {
            continue;
          }
          var def = nested.GetDefinition();
          if (def != null && !lookup.IsAccessible(def, false))
            continue;
          result.AddType(nested, false);
        }
      }
      return result.Result;
    }

    IEnumerable<ICompletionData> CreateTypeList()
    {
      foreach (var cl in Compilation.RootNamespace.Types) {
        yield return factory.CreateTypeCompletionData(cl, false, false, false);
      }

      foreach (var ns in Compilation.RootNamespace.ChildNamespaces) {
        yield return factory.CreateNamespaceCompletionData(ns);
      }
    }

    void CreateParameterForInvocation(CompletionDataWrapper result, IMethod method, CSharpResolver state, int parameter, HashSet<string> addedEnums, HashSet<string> addedDelegates)
    {
      if (method.Parameters.Count <= parameter) {
        return;
      }
      var resolvedType = method.Parameters [parameter].Type;
      if (resolvedType.Kind == TypeKind.Enum) {
        if (addedEnums.Contains(resolvedType.ReflectionName)) {
          return;
        }
        addedEnums.Add(resolvedType.ReflectionName);
        AddEnumMembers(result, resolvedType, state);
        return;
      }

      if (resolvedType.Kind == TypeKind.Delegate) {
        if (addedDelegates.Contains(resolvedType.ReflectionName))
          return;
        AddDelegateHandlers(result, resolvedType, false, true, "Handle" + method.Parameters [parameter].Type.Name + method.Parameters [parameter].Name);
      }
    }

    IEnumerable<ICompletionData> CreateParameterCompletion(MethodGroupResolveResult resolveResult, CSharpResolver state, AstNode invocation, SyntaxTree unit, int parameter, bool controlSpace)
    {
      var result = new CompletionDataWrapper(this);
      var addedEnums = new HashSet<string>();
      var addedDelegates = new HashSet<string>();

      foreach (var method in resolveResult.Methods) {
        CreateParameterForInvocation(result, method, state, parameter, addedEnums, addedDelegates);
      }
      foreach (var methods in resolveResult.GetEligibleExtensionMethods (true)) {
        foreach (var method in methods) {
          if (resolveResult.Methods.Contains(method))
            continue;
          CreateParameterForInvocation(result, new ReducedExtensionMethod(method), state, parameter, addedEnums, addedDelegates);
        }
      }

      foreach (var method in resolveResult.Methods) {
        if (parameter < method.Parameters.Count && method.Parameters [parameter].Type.Kind == TypeKind.Delegate) {
          AutoSelect = false;
          AutoCompleteEmptyMatch = false;
        }
        foreach (var p in method.Parameters) {
          result.AddNamedParameterVariable(p);
        }
      }

      if (!controlSpace) {
        if (addedEnums.Count + addedDelegates.Count == 0) {
          return Enumerable.Empty<ICompletionData>();
        }
        AutoCompleteEmptyMatch = false;
        AutoSelect = false;
      }
      AddContextCompletion(result, state, invocation);

      //      resolver.AddAccessibleCodeCompletionData (ExpressionContext.MethodBody, cdc);
      //      if (addedDelegates.Count > 0) {
      //        foreach (var data in result.Result) {
      //          if (data is MemberCompletionData) 
      //            ((MemberCompletionData)data).IsDelegateExpected = true;
      //        }
      //      }
      return result.Result;
    }

    void AddEnumMembers(CompletionDataWrapper completionList, IType resolvedType, CSharpResolver state)
    {
      if (resolvedType.Kind != TypeKind.Enum) {
        return;
      }
      var type = completionList.AddEnumMembers(resolvedType, state);
      if (type != null)
        DefaultCompletionString = type.DisplayText;
    }

    IEnumerable<ICompletionData> CreateCompletionData(TextLocation location, ResolveResult resolveResult, AstNode resolvedNode, CSharpResolver state, Func<IType, IType> typePred = null)
    {
      if (resolveResult == null /*      || resolveResult.IsError*/) {
        return null;
      }

      var lookup = new MemberLookup(
        ctx.CurrentTypeDefinition,
        Compilation.MainAssembly
      );

      if (resolveResult is NamespaceResolveResult) {
        var nr = (NamespaceResolveResult)resolveResult;
        var namespaceContents = new CompletionDataWrapper(this);

        foreach (var cl in nr.Namespace.Types) {
          if (!lookup.IsAccessible(cl, false))
            continue;
          IType addType = typePred != null ? typePred(cl) : cl;
          if (addType != null)
            namespaceContents.AddType(addType, false);
        }

        foreach (var ns in nr.Namespace.ChildNamespaces) {
          namespaceContents.AddNamespace(lookup, ns);
        }
        return namespaceContents.Result;
      }
      IType type = resolveResult.Type;

      if (type.Namespace == "System" && type.Name == "Void")
        return null;

      if (resolvedNode.Parent is PointerReferenceExpression && (type is PointerType)) {
        resolveResult = new OperatorResolveResult(((PointerType)type).ElementType, System.Linq.Expressions.ExpressionType.Extension, resolveResult);
      }

      //var typeDef = resolveResult.Type.GetDefinition();
      var result = new CompletionDataWrapper(this);
      bool includeStaticMembers = false;

      if (resolveResult is LocalResolveResult) {
        if (resolvedNode is IdentifierExpression) {
          var mrr = (LocalResolveResult)resolveResult;
          includeStaticMembers = mrr.Variable.Name == mrr.Type.Name;
        }
      }
      if (resolveResult is TypeResolveResult && type.Kind == TypeKind.Enum) {
        foreach (var field in type.GetFields ()) {
          if (!lookup.IsAccessible(field, false))
            continue;
          result.AddMember(field);
        }
        return result.Result;
      }

      bool isProtectedAllowed = lookup.IsProtectedAccessAllowed(resolveResult);
      bool skipNonStaticMembers = (resolveResult is TypeResolveResult);

      if (resolveResult is MemberResolveResult && resolvedNode is IdentifierExpression) {
        var mrr = (MemberResolveResult)resolveResult;
        includeStaticMembers = mrr.Member.Name == mrr.Type.Name;

        TypeResolveResult trr;
        if (state.IsVariableReferenceWithSameType(
          resolveResult,
          ((IdentifierExpression)resolvedNode).Identifier,
          out trr
        )) {
          if (currentMember != null && mrr.Member.IsStatic ^ currentMember.IsStatic) {
            skipNonStaticMembers = true;

            if (trr.Type.Kind == TypeKind.Enum) {
              foreach (var field in trr.Type.GetFields ()) {
                if (lookup.IsAccessible(field, false))
                  result.AddMember(field);
              }
              return result.Result;
            }
          }
        }
        // ADD Aliases
        var scope = ctx.CurrentUsingScope;

        for (var n = scope; n != null; n = n.Parent) {
          foreach (var pair in n.UsingAliases) {
            if (pair.Key == mrr.Member.Name) {
              foreach (var r in CreateCompletionData (location, pair.Value, resolvedNode, state)) {
                if (r is IEntityCompletionData && ((IEntityCompletionData)r).Entity is IMember) {
                  result.AddMember((IMember)((IEntityCompletionData)r).Entity);
                } else {
                  result.Add(r);
                }
              }
            }
          }
        }       


      }
      if (resolveResult is TypeResolveResult && (resolvedNode is IdentifierExpression || resolvedNode is MemberReferenceExpression)) {
        includeStaticMembers = true;
      }

      //      Console.WriteLine ("type:" + type +"/"+type.GetType ());
      //      Console.WriteLine ("current:" + ctx.CurrentTypeDefinition);
      //      Console.WriteLine ("IS PROT ALLOWED:" + isProtectedAllowed + " static: "+ includeStaticMembers);
      //      Console.WriteLine (resolveResult);
      //      Console.WriteLine ("node:" + resolvedNode);
      //      Console.WriteLine (currentMember !=  null ? currentMember.IsStatic : "currentMember == null");

      if (resolvedNode.Annotation<ObjectCreateExpression>() == null) {
        //tags the created expression as part of an object create expression.
        /*        
        var filteredList = new List<IMember>();
        foreach (var member in type.GetMembers ()) {
          filteredList.Add(member);
        }
        
        foreach (var member in filteredList) {
          //          Console.WriteLine ("add:" + member + "/" + member.IsStatic);
          result.AddMember(member);
        }*/
        foreach (var member in lookup.GetAccessibleMembers (resolveResult)) {
          if (member.SymbolKind == SymbolKind.Indexer || member.SymbolKind == SymbolKind.Operator || member.SymbolKind == SymbolKind.Constructor || member.SymbolKind == SymbolKind.Destructor) {
            continue;
          }
          if (resolvedNode is BaseReferenceExpression && member.IsAbstract) {
            continue;
          }
          if (member is IType) {
            if (resolveResult is TypeResolveResult || includeStaticMembers) {
              if (!lookup.IsAccessible(member, isProtectedAllowed))
                continue;
              result.AddType((IType)member, false);
              continue;
            }
          }
          bool memberIsStatic = member.IsStatic;
          if (!includeStaticMembers && memberIsStatic && !(resolveResult is TypeResolveResult)) {
            //            Console.WriteLine ("skip static member: " + member.FullName);
            continue;
          }

          var field = member as IField;
          if (field != null) {
            memberIsStatic |= field.IsConst;
          }
          if (!memberIsStatic && skipNonStaticMembers) {
            continue;
          }

          if (member is IMethod && ((IMethod)member).FullName == "System.Object.Finalize") {
            continue;
          }
          if (member.SymbolKind == SymbolKind.Operator) {
            continue;
          }

          if (member is IMember) {
            result.AddMember((IMember)member);
          }
        }
      }

      if (!(resolveResult is TypeResolveResult || includeStaticMembers)) {
        foreach (var meths in state.GetExtensionMethods (type)) {
          foreach (var m in meths) {
            if (!lookup.IsAccessible(m, isProtectedAllowed))
              continue;
            result.AddMember(new ReducedExtensionMethod(m));
          }
        }
      }

      //      IEnumerable<object> objects = resolveResult.CreateResolveResult (dom, resolver != null ? resolver.CallingMember : null);
      //      CompletionDataCollector col = new CompletionDataCollector (this, dom, result, Document.CompilationUnit, resolver != null ? resolver.CallingType : null, location);
      //      col.HideExtensionParameter = !resolveResult.StaticResolve;
      //      col.NamePrefix = expressionResult.Expression;
      //      bool showOnlyTypes = expressionResult.Contexts.Any (ctx => ctx == ExpressionContext.InheritableType || ctx == ExpressionContext.Constraints);
      //      if (objects != null) {
      //        foreach (object obj in objects) {
      //          if (expressionResult.ExpressionContext != null && expressionResult.ExpressionContext.FilterEntry (obj))
      //            continue;
      //          if (expressionResult.ExpressionContext == ExpressionContext.NamespaceNameExcepted && !(obj is Namespace))
      //            continue;
      //          if (showOnlyTypes && !(obj is IType))
      //            continue;
      //          CompletionData data = col.Add (obj);
      //          if (data != null && expressionResult.ExpressionContext == ExpressionContext.Attribute && data.CompletionText != null && data.CompletionText.EndsWith ("Attribute")) {
      //            string newText = data.CompletionText.Substring (0, data.CompletionText.Length - "Attribute".Length);
      //            data.SetText (newText);
      //          }
      //        }
      //      }

      return result.Result;
    }

    IEnumerable<ICompletionData> CreateCaseCompletionData(TextLocation location)
    {
      var unit = ParseStub("a: break;");
      if (unit == null) {
        return null;
      }
      var s = unit.GetNodeAt<SwitchStatement>(location);
      if (s == null) {
        return null;
      }

      var offset = document.GetOffset(s.Expression.StartLocation);
      var expr = GetExpressionAt(offset);
      if (expr == null) {
        return null;
      }

      var resolveResult = ResolveExpression(expr);
      if (resolveResult == null || resolveResult.Result.Type.Kind != TypeKind.Enum) { 
        return null;
      }
      var wrapper = new CompletionDataWrapper(this);
      AddEnumMembers(wrapper, resolveResult.Result.Type, resolveResult.Resolver);
      AutoCompleteEmptyMatch = false;
      return wrapper.Result;
    }

    #region Parsing methods

    ExpressionResult GetExpressionBeforeCursor()
    {
      SyntaxTree baseUnit;
      if (currentMember == null) {
        baseUnit = ParseStub("a", false);
        var type = baseUnit.GetNodeAt<MemberType>(location);
        if (type == null) {
          baseUnit = ParseStub("a;", false);
          type = baseUnit.GetNodeAt<MemberType>(location);
        }

        if (type == null) {
          baseUnit = ParseStub("A a;", false);
          type = baseUnit.GetNodeAt<MemberType>(location);
        }
        if (type != null) {
          return new ExpressionResult((AstNode)type.Target, baseUnit);
        }
      }

      baseUnit = ParseStub("ToString()", false);
      var curNode = baseUnit.GetNodeAt(location);
      // hack for local variable declaration missing ';' issue - remove that if it works.
      if (curNode is EntityDeclaration || baseUnit.GetNodeAt<Expression>(location) == null && baseUnit.GetNodeAt<MemberType>(location) == null) {
        baseUnit = ParseStub("a");
        curNode = baseUnit.GetNodeAt(location);
      }

      // Hack for handle object initializer continuation expressions
      if (curNode is EntityDeclaration || baseUnit.GetNodeAt<Expression>(location) == null && baseUnit.GetNodeAt<MemberType>(location) == null) {
        baseUnit = ParseStub("a};");
      }
      var mref = baseUnit.GetNodeAt<MemberReferenceExpression>(location); 
      if (currentMember == null && currentType == null) {
        if (mref != null) {
          return new ExpressionResult((AstNode)mref.Target, baseUnit);
        }
        return null;
      }

      //var memberLocation = currentMember != null ? currentMember.Region.Begin : currentType.Region.Begin;
      if (mref == null) {
        var type = baseUnit.GetNodeAt<MemberType>(location); 
        if (type != null) {
          return new ExpressionResult((AstNode)type.Target, baseUnit);
        }

        var pref = baseUnit.GetNodeAt<PointerReferenceExpression>(location); 
        if (pref != null) {
          return new ExpressionResult((AstNode)pref.Target, baseUnit);
        }
      }

      if (mref == null) {
        baseUnit = ParseStub("A a;", false);
        var type = baseUnit.GetNodeAt<MemberType>(location);
        if (type != null) {
          return new ExpressionResult((AstNode)type.Target, baseUnit);
        }
      }

      AstNode expr = null;
      if (mref != null) {
        expr = mref.Target;
      } else {
        Expression tref = baseUnit.GetNodeAt<TypeReferenceExpression>(location); 
        MemberType memberType = tref != null ? ((TypeReferenceExpression)tref).Type as MemberType : null;
        if (memberType == null) {
          memberType = baseUnit.GetNodeAt<MemberType>(location); 
          if (memberType != null) {
            if (memberType.Parent is ObjectCreateExpression) {
              var mt = memberType.Target.Clone();
              memberType.ReplaceWith(mt);
              expr = mt;
              goto exit;
            } else {
              tref = baseUnit.GetNodeAt<Expression>(location); 
              if (tref == null) {
                tref = new TypeReferenceExpression(memberType.Clone());
                memberType.Parent.AddChild(tref, Roles.Expression);
              }
              if (tref is ObjectCreateExpression) {
                expr = memberType.Target.Clone();
                expr.AddAnnotation(new ObjectCreateExpression());
              }
            }
          }
        }

        if (memberType == null) {
          return null;
        }
        if (expr == null) {
          expr = memberType.Target.Clone();
        }
        tref.ReplaceWith(expr);
      }
      exit:
      return new ExpressionResult((AstNode)expr, baseUnit);
    }

    ExpressionResult GetExpressionAtCursor()
    {
      //      TextLocation memberLocation;
      //      if (currentMember != null) {
      //        memberLocation = currentMember.Region.Begin;
      //      } else if (currentType != null) {
      //        memberLocation = currentType.Region.Begin;
      //      } else {
      //        memberLocation = location;
      //      }
      var baseUnit = ParseStub("a");
      var tmpUnit = baseUnit;
      AstNode expr = baseUnit.GetNodeAt(
        location,
        n => n is IdentifierExpression || n is MemberReferenceExpression
      );

      if (expr == null) {
        expr = baseUnit.GetNodeAt<AstType>(location.Line, location.Column - 1);
      }
      if (expr == null)
        expr = baseUnit.GetNodeAt<Identifier>(location.Line, location.Column - 1);
      // try insertStatement
      if (expr == null && baseUnit.GetNodeAt<EmptyStatement>(location.Line, location.Column) != null) {
        tmpUnit = baseUnit = ParseStub("a();", false);
        expr = baseUnit.GetNodeAt<InvocationExpression>(
          location.Line,
          location.Column + 1
        ); 
      }

      if (expr == null) {
        baseUnit = ParseStub("()");
        expr = baseUnit.GetNodeAt<IdentifierExpression>(
          location.Line,
          location.Column - 1
        ); 
        if (expr == null) {
          expr = baseUnit.GetNodeAt<MemberType>(location.Line, location.Column - 1); 
        }
      }

      if (expr == null) {
        baseUnit = ParseStub("a", false);
        expr = baseUnit.GetNodeAt(
          location,
          n => n is IdentifierExpression || n is MemberReferenceExpression || n is CatchClause
        );
      }

      // try statement 
      if (expr == null) {
        expr = tmpUnit.GetNodeAt<SwitchStatement>(
          location.Line,
          location.Column - 1
        ); 
        baseUnit = tmpUnit;
      }

      if (expr == null) {
        var block = tmpUnit.GetNodeAt<BlockStatement>(location); 
        var node = block != null ? block.Statements.LastOrDefault() : null;

        var forStmt = node != null ? node.PrevSibling as ForStatement : null;
        if (forStmt != null && forStmt.EmbeddedStatement.IsNull) {
          expr = forStmt;
          var id = new IdentifierExpression("stub");
          forStmt.EmbeddedStatement = new BlockStatement() { Statements = { new ExpressionStatement(id) } };
          expr = id;
          baseUnit = tmpUnit;
        }
      }

      if (expr == null) {
        var forStmt = tmpUnit.GetNodeAt<ForeachStatement>(
          location.Line,
          location.Column - 3
        ); 
        if (forStmt != null && forStmt.EmbeddedStatement.IsNull) {
          forStmt.VariableNameToken = Identifier.Create("stub");
          expr = forStmt.VariableNameToken;
          baseUnit = tmpUnit;
        }
      }
      if (expr == null) {
        expr = tmpUnit.GetNodeAt<VariableInitializer>(
          location.Line,
          location.Column - 1
        );
        baseUnit = tmpUnit;
      }

      // try parameter declaration type
      if (expr == null) {
        baseUnit = ParseStub(">", false, "{}");
        expr = baseUnit.GetNodeAt<TypeParameterDeclaration>(
          location.Line,
          location.Column - 1
        ); 
      }

      // try parameter declaration method
      if (expr == null) {
        baseUnit = ParseStub("> ()", false, "{}");
        expr = baseUnit.GetNodeAt<TypeParameterDeclaration>(
          location.Line,
          location.Column - 1
        ); 
      }

      // try expression in anonymous type "new { sample = x$" case
      if (expr == null) {
        baseUnit = ParseStub("a", false);
        expr = baseUnit.GetNodeAt<AnonymousTypeCreateExpression>(
          location.Line,
          location.Column
        ); 
        if (expr != null) {
          expr = baseUnit.GetNodeAt<Expression>(location.Line, location.Column) ?? expr;
        } 
        if (expr == null) {
          expr = baseUnit.GetNodeAt<AstType>(location.Line, location.Column);
        } 
      }

      // try lambda 
      if (expr == null) {
        baseUnit = ParseStub("foo) => {}", false);
        expr = baseUnit.GetNodeAt<ParameterDeclaration>(
          location.Line,
          location.Column
        ); 
      }

      if (expr == null)
        return null;
      return new ExpressionResult(expr, baseUnit);
    }

    ExpressionResult GetExpressionAt(int offset)
    {
      var parser = new CSharpParser();
      var text = GetMemberTextToCaret(); 

      int closingBrackets = 0, generatedLines = 0;
      var sb = CreateWrapper("a;", false, "", text.Item1, text.Item2, ref closingBrackets, ref generatedLines);

      var completionUnit = parser.Parse(sb.ToString());
      var offsetLocation = document.GetLocation(offset);
      var loc = new TextLocation(offsetLocation.Line - text.Item2.Line + generatedLines + 1, offsetLocation.Column);

      var expr = completionUnit.GetNodeAt(
        loc,
        n => n is Expression || n is VariableDeclarationStatement
      );
      if (expr == null)
        return null;
      return new ExpressionResult(expr, completionUnit);
    }

    ExpressionResult GetNewExpressionAt(int offset)
    {
      var parser = new CSharpParser();
      var text = GetMemberTextToCaret();
      int closingBrackets = 0, generatedLines = 0;
      var sb = CreateWrapper("a ();", false, "", text.Item1, text.Item2, ref closingBrackets, ref generatedLines);

      var completionUnit = parser.Parse(sb.ToString());
      var offsetLocation = document.GetLocation(offset);
      var loc = new TextLocation(offsetLocation.Line - text.Item2.Line + generatedLines + 1, offsetLocation.Column);

      var expr = completionUnit.GetNodeAt(loc, n => n is Expression);
      if (expr == null) {
        // try without ";"
        sb = CreateWrapper("a ()", false, "", text.Item1, text.Item2, ref closingBrackets, ref generatedLines);
        completionUnit = parser.Parse(sb.ToString());

        expr = completionUnit.GetNodeAt(loc, n => n is Expression);
        if (expr == null) {
          return null;
        }
      }
      return new ExpressionResult(expr, completionUnit);
    }

    #endregion

    #region Helper methods

    string GetPreviousToken(ref int i, bool allowLineChange)
    {
      char c;
      if (i <= 0) {
        return null;
      }

      do {
        c = document.GetCharAt(--i);
      } while (i > 0 && char.IsWhiteSpace(c) && (allowLineChange ? true : c != '\n'));

      if (i == 0) {
        return null;
      }

      if (!char.IsLetterOrDigit(c)) {
        return new string(c, 1);
      }

      int endOffset = i + 1;

      do {
        c = document.GetCharAt(i - 1);
        if (!(char.IsLetterOrDigit(c) || c == '_')) {
          break;
        }

        i--;
      } while (i > 0);

      return document.GetText(i, endOffset - i);
    }

    #endregion

    #region Preprocessor

    IEnumerable<ICompletionData> GetDirectiveCompletionData()
    {
      yield return factory.CreateLiteralCompletionData("if");
      yield return factory.CreateLiteralCompletionData("else");
      yield return factory.CreateLiteralCompletionData("elif");
      yield return factory.CreateLiteralCompletionData("endif");
      yield return factory.CreateLiteralCompletionData("define");
      yield return factory.CreateLiteralCompletionData("undef");
      yield return factory.CreateLiteralCompletionData("warning");
      yield return factory.CreateLiteralCompletionData("error");
      yield return factory.CreateLiteralCompletionData("pragma");
      yield return factory.CreateLiteralCompletionData("line");
      yield return factory.CreateLiteralCompletionData("line hidden");
      yield return factory.CreateLiteralCompletionData("line default");
      yield return factory.CreateLiteralCompletionData("region");
      yield return factory.CreateLiteralCompletionData("endregion");
    }

    #endregion

    #region Xml Comments

    static readonly List<string> commentTags = new List<string>(new string[] {
      "c",
      "code",
      "example",
      "exception",
      "include",
      "list",
      "listheader",
      "item",
      "term",
      "description",
      "para",
      "param",
      "paramref",
      "permission",
      "remarks",
      "returns",
      "see",
      "seealso",
      "summary",
      "value"
    }
    );

    public static IEnumerable<string> CommentTags {
      get {
        return commentTags;
      }
    }

    string GetLastClosingXmlCommentTag()
    {
      var line = document.GetLineByNumber(location.Line);

      restart:
      string lineText = document.GetText(line);
      if (!lineText.Trim().StartsWith("///", StringComparison.Ordinal))
        return null;
      int startIndex = Math.Min(location.Column - 1, lineText.Length - 1) - 1;
      while (startIndex > 0 && lineText [startIndex] != '<') {
        --startIndex;
        if (lineText [startIndex] == '/') {
          // already closed.
          startIndex = -1;
          break;
        }
      }
      if (startIndex < 0 && line.PreviousLine != null) {
        line = line.PreviousLine;
        goto restart;
      }

      if (startIndex >= 0) {
        int endIndex = startIndex;
        while (endIndex + 1 < lineText.Length && lineText [endIndex] != '>' && !char.IsWhiteSpace(lineText [endIndex])) {
          endIndex++;
        }
        string tag = endIndex - startIndex - 1 > 0 ? lineText.Substring(
          startIndex + 1,
          endIndex - startIndex - 1
        ) : null;
        if (!string.IsNullOrEmpty(tag) && commentTags.IndexOf(tag) >= 0) {
          return tag;
        }
      }
      return null;
    }

    IEnumerable<ICompletionData> GetXmlDocumentationCompletionData()
    {
      var closingTag = GetLastClosingXmlCommentTag();
      if (closingTag != null) {
        yield return factory.CreateLiteralCompletionData(
          "/" + closingTag + ">"
        );
      }

      yield return factory.CreateXmlDocCompletionData(
        "c",
        "Set text in a code-like font"
      );
      yield return factory.CreateXmlDocCompletionData(
        "code",
        "Set one or more lines of source code or program output"
      );
      yield return factory.CreateXmlDocCompletionData(
        "example",
        "Indicate an example"
      );
      yield return factory.CreateXmlDocCompletionData(
        "exception",
        "Identifies the exceptions a method can throw",
        "exception cref=\"|\"></exception"
      );
      yield return factory.CreateXmlDocCompletionData(
        "include",
        "Includes comments from a external file",
        "include file=\"|\" path=\"\""
      );
      yield return factory.CreateXmlDocCompletionData(
        "inheritdoc",
        "Inherit documentation from a base class or interface",
        "inheritdoc/"
      );
      yield return factory.CreateXmlDocCompletionData(
        "list",
        "Create a list or table",
        "list type=\"|\""
      );
      yield return factory.CreateXmlDocCompletionData(
        "listheader",
        "Define the heading row"
      );
      yield return factory.CreateXmlDocCompletionData(
        "item",
        "Defines list or table item"
      );

      yield return factory.CreateXmlDocCompletionData("term", "A term to define");
      yield return factory.CreateXmlDocCompletionData(
        "description",
        "Describes a list item"
      );
      yield return factory.CreateXmlDocCompletionData(
        "para",
        "Permit structure to be added to text"
      );

      yield return factory.CreateXmlDocCompletionData(
        "param",
        "Describe a parameter for a method or constructor",
        "param name=\"|\""
      );
      yield return factory.CreateXmlDocCompletionData(
        "paramref",
        "Identify that a word is a parameter name",
        "paramref name=\"|\"/"
      );

      yield return factory.CreateXmlDocCompletionData(
        "permission",
        "Document the security accessibility of a member",
        "permission cref=\"|\""
      );
      yield return factory.CreateXmlDocCompletionData(
        "remarks",
        "Describe a type"
      );
      yield return factory.CreateXmlDocCompletionData(
        "returns",
        "Describe the return value of a method"
      );
      yield return factory.CreateXmlDocCompletionData(
        "see",
        "Specify a link",
        "see cref=\"|\"/"
      );
      yield return factory.CreateXmlDocCompletionData(
        "seealso",
        "Generate a See Also entry",
        "seealso cref=\"|\"/"
      );
      yield return factory.CreateXmlDocCompletionData(
        "summary",
        "Describe a member of a type"
      );
      yield return factory.CreateXmlDocCompletionData(
        "typeparam",
        "Describe a type parameter for a generic type or method"
      );
      yield return factory.CreateXmlDocCompletionData(
        "typeparamref",
        "Identify that a word is a type parameter name"
      );
      yield return factory.CreateXmlDocCompletionData(
        "value",
        "Describe a property"
      );

    }

    #endregion

    #region Keywords

    static string[] expressionLevelKeywords = new string [] {
      "as",
      "is",
      "else",
      "out",
      "ref",
      "null",
      "delegate",
      "default"
    };
    static string[] primitiveTypesKeywords = new string [] {
      "void",
      "object",
      "bool",
      "byte",
      "sbyte",
      "char",
      "short",
      "int",
      "long",
      "ushort",
      "uint",
      "ulong",
      "float",
      "double",
      "decimal",
      "string"
    };
    static string[] statementStartKeywords = new string [] { "base", "new", "sizeof", "this", 
      "true", "false", "typeof", "checked", "unchecked", "from", "break", "checked",
      "unchecked", "const", "continue", "do", "finally", "fixed", "for", "foreach",
      "goto", "if", "lock", "return", "stackalloc", "switch", "throw", "try", "unsafe", 
      "using", "while", "yield",
      "catch"
    };
    static string[] globalLevelKeywords = new string [] {
      "namespace", "using", "extern", "public", "internal", 
      "class", "interface", "struct", "enum", "delegate",
      "abstract", "sealed", "static", "unsafe", "partial"
    };
    static string[] accessorModifierKeywords = new string [] {
      "public", "internal", "protected", "private", "async"
    };
    static string[] typeLevelKeywords = new string [] {
      "public", "internal", "protected", "private", "async",
      "class", "interface", "struct", "enum", "delegate",
      "abstract", "sealed", "static", "unsafe", "partial",
      "const", "event", "extern", "fixed", "new", 
      "operator", "explicit", "implicit", 
      "override", "readonly", "virtual", "volatile"
    };
    static string[] linqKeywords = new string[] {
      "from",
      "where",
      "select",
      "group",
      "into",
      "orderby",
      "join",
      "let",
      "in",
      "on",
      "equals",
      "by",
      "ascending",
      "descending"
    };
    static string[] parameterTypePredecessorKeywords = new string[] {
      "out",
      "ref",
      "params"
    };

    #endregion

  }
}