source: trunk/sources/HeuristicLab.ExtLibs/HeuristicLab.NRefactory/5.5.0/NRefactory.CSharp-5.5.0/Resolver/MemberLookup.cs @ 15532

// Copyright (c) 2010-2013 AlphaSierraPapa for the SharpDevelop Team
// 
// Permission is hereby granted, free of charge, to any person obtaining a copy of this
// software and associated documentation files (the "Software"), to deal in the Software
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// 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
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// DEALINGS IN THE SOFTWARE.

using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.Linq;

using ICSharpCode.NRefactory.Semantics;
using ICSharpCode.NRefactory.TypeSystem;

namespace ICSharpCode.NRefactory.CSharp.Resolver
{
  /// <summary>
  /// Implementation of member lookup (C# 4.0 spec, §7.4).
  /// </summary>
  public class MemberLookup
  {
    #region Static helper methods
    /// <summary>
    /// Gets whether the member is considered to be invocable.
    /// </summary>
    public static bool IsInvocable(IMember member)
    {
      if (member == null)
        throw new ArgumentNullException("member");
      // C# 4.0 spec, §7.4 member lookup
      if (member is IEvent || member is IMethod)
        return true;
      IType returnType = member.ReturnType;
      return returnType.Kind == TypeKind.Dynamic || returnType.Kind == TypeKind.Delegate;
    }
    #endregion
    
    readonly ITypeDefinition currentTypeDefinition;
    readonly IAssembly currentAssembly;
    readonly bool isInEnumMemberInitializer;
    
    public MemberLookup(ITypeDefinition currentTypeDefinition, IAssembly currentAssembly, bool isInEnumMemberInitializer = false)
    {
      this.currentTypeDefinition = currentTypeDefinition;
      this.currentAssembly = currentAssembly;
      this.isInEnumMemberInitializer = isInEnumMemberInitializer;
    }
    
    #region IsAccessible
    /// <summary>
    /// Gets whether access to protected instance members of the target expression is possible.
    /// </summary>
    public bool IsProtectedAccessAllowed(ResolveResult targetResolveResult)
    {
      return targetResolveResult is ThisResolveResult || IsProtectedAccessAllowed(targetResolveResult.Type);
    }
    
    /// <summary>
    /// Gets whether access to protected instance members of the target type is possible.
    /// </summary>
    /// <remarks>
    /// This method does not consider the special case of the 'base' reference. If possible, use the
    /// <c>IsProtectedAccessAllowed(ResolveResult)</c> overload instead.
    /// </remarks>
    public bool IsProtectedAccessAllowed(IType targetType)
    {
      if (targetType.Kind == TypeKind.TypeParameter)
        targetType = ((ITypeParameter)targetType).EffectiveBaseClass;
      ITypeDefinition typeDef = targetType.GetDefinition();
      if (typeDef == null)
        return false;
      for (ITypeDefinition c = currentTypeDefinition; c != null; c = c.DeclaringTypeDefinition) {
        if (typeDef.IsDerivedFrom(c))
          return true;
      }
      return false;
    }
    
    /// <summary>
    /// Gets whether <paramref name="entity"/> is accessible in the current class.
    /// </summary>
    /// <param name="entity">The entity to test</param>
    /// <param name="allowProtectedAccess">
    /// Whether protected access to instance members is allowed.
    /// True if the type of the reference is derived from the current class.
    /// Protected static members may be accessible even if false is passed for this parameter.
    /// </param>
    public bool IsAccessible(IEntity entity, bool allowProtectedAccess)
    {
      if (entity == null)
        throw new ArgumentNullException("entity");
      // C# 4.0 spec, §3.5.2 Accessiblity domains
      switch (entity.Accessibility) {
        case Accessibility.None:
          return false;
        case Accessibility.Private:
          // check for members of outer classes (private members of outer classes can be accessed)
          for (var t = currentTypeDefinition; t != null; t = t.DeclaringTypeDefinition) {
            if (t.Equals(entity.DeclaringTypeDefinition))
              return true;
          }
          return false;
        case Accessibility.Public:
          return true;
        case Accessibility.Protected:
          return IsProtectedAccessible(allowProtectedAccess, entity);
        case Accessibility.Internal:
          return IsInternalAccessible(entity.ParentAssembly);
        case Accessibility.ProtectedOrInternal:
          return IsInternalAccessible(entity.ParentAssembly) || IsProtectedAccessible(allowProtectedAccess, entity);
        case Accessibility.ProtectedAndInternal:
          return IsInternalAccessible(entity.ParentAssembly) && IsProtectedAccessible(allowProtectedAccess, entity);
        default:
          throw new Exception("Invalid value for Accessibility");
      }
    }
    
    bool IsInternalAccessible(IAssembly assembly)
    {
      return assembly != null && currentAssembly != null && assembly.InternalsVisibleTo(currentAssembly);
    }
    
    bool IsProtectedAccessible(bool allowProtectedAccess, IEntity entity)
    {
      // For static members and type definitions, we do not require the qualifying reference
      // to be derived from the current class (allowProtectedAccess).
      if (entity.IsStatic || entity.SymbolKind == SymbolKind.TypeDefinition)
        allowProtectedAccess = true;
      
      for (var t = currentTypeDefinition; t != null; t = t.DeclaringTypeDefinition) {
        if (t.Equals(entity.DeclaringTypeDefinition))
          return true;
        
        // PERF: this might hurt performance as this method is called several times (once for each member)
        // make sure resolving base types is cheap (caches?) or cache within the MemberLookup instance
        if (allowProtectedAccess && t.IsDerivedFrom(entity.DeclaringTypeDefinition))
          return true;
      }
      return false;
    }
    #endregion
    
    #region GetAccessibleMembers
    /// <summary>
    /// Retrieves all members that are accessible and not hidden (by being overridden or shadowed).
    /// Returns both members and nested type definitions. Does not include extension methods.
    /// </summary>
    public IEnumerable<IEntity> GetAccessibleMembers(ResolveResult targetResolveResult)
    {
      if (targetResolveResult == null)
        throw new ArgumentNullException("targetResolveResult");
      
      bool targetIsTypeParameter = targetResolveResult.Type.Kind == TypeKind.TypeParameter;
      bool allowProtectedAccess = IsProtectedAccessAllowed(targetResolveResult);
      
      // maps the member name to the list of lookup groups
      var lookupGroupDict = new Dictionary<string, List<LookupGroup>>();
      
      // This loop will handle base types before derived types.
      // The loop performs three jobs:
      // 1) It marks entries in lookup groups from base classes as removed when those members
      //    are hidden by a derived class.
      // 2) It adds a new lookup group with the members from a declaring type.
      // 3) It replaces virtual members with the overridden version, placing the override in the
      //    lookup group belonging to the base class.
      foreach (IType type in targetResolveResult.Type.GetNonInterfaceBaseTypes()) {
        
        List<IEntity> entities = new List<IEntity>();
        entities.AddRange(type.GetMembers(options: GetMemberOptions.IgnoreInheritedMembers));
        if (!targetIsTypeParameter) {
          var nestedTypes = type.GetNestedTypes(options: GetMemberOptions.IgnoreInheritedMembers | GetMemberOptions.ReturnMemberDefinitions);
          // GetDefinition() might return null if some IType has a strange implementation of GetNestedTypes.
          entities.AddRange(nestedTypes.Select(t => t.GetDefinition()).Where(td => td != null));
        }
        
        foreach (var entityGroup in entities.GroupBy(e => e.Name)) {
          
          List<LookupGroup> lookupGroups = new List<LookupGroup>();
          if (!lookupGroupDict.TryGetValue(entityGroup.Key, out lookupGroups))
            lookupGroupDict.Add(entityGroup.Key, lookupGroups = new List<LookupGroup>());
          
          List<IType> newNestedTypes = null;
          List<IParameterizedMember> newMethods = null;
          IMember newNonMethod = null;
          
          IEnumerable<IType> typeBaseTypes = null;
          
          if (!targetIsTypeParameter) {
            AddNestedTypes(type, entityGroup.OfType<IType>(), 0, lookupGroups, ref typeBaseTypes, ref newNestedTypes);
          }
          AddMembers(type, entityGroup.OfType<IMember>(), allowProtectedAccess, lookupGroups, false, ref typeBaseTypes, ref newMethods, ref newNonMethod);
          
          if (newNestedTypes != null || newMethods != null || newNonMethod != null)
            lookupGroups.Add(new LookupGroup(type, newNestedTypes, newMethods, newNonMethod));
        }
      }
      
      foreach (List<LookupGroup> lookupGroups in lookupGroupDict.Values) {
        // Remove interface members hidden by class members.
        if (targetIsTypeParameter) {
          // This can happen only with type parameters.
          RemoveInterfaceMembersHiddenByClassMembers(lookupGroups);
        }
        
        // Now report the results:
        foreach (LookupGroup lookupGroup in lookupGroups) {
          if (!lookupGroup.MethodsAreHidden) {
            foreach (IMethod method in lookupGroup.Methods) {
              yield return method;
            }
          }
          if (!lookupGroup.NonMethodIsHidden) {
            yield return lookupGroup.NonMethod;
          }
          if (lookupGroup.NestedTypes != null) {
            foreach (IType type in lookupGroup.NestedTypes) {
              ITypeDefinition typeDef = type.GetDefinition();
              if (typeDef != null)
                yield return typeDef;
            }
          }
        }
      }
    }
    #endregion
    
    #region class LookupGroup
    sealed class LookupGroup
    {
      public readonly IType DeclaringType;
      
      // When a nested type is hidden, it is simply removed from the list.
      public List<IType> NestedTypes;
      
      // When members are hidden, they are merely marked as hidden.
      // We still need to store the hidden methods so that the 'override' processing can
      // find them, so that it won't introduce the override as a new method.
      public readonly List<IParameterizedMember> Methods;
      public bool MethodsAreHidden;
      
      public IMember NonMethod;
      public bool NonMethodIsHidden;
      
      public LookupGroup(IType declaringType, List<IType> nestedTypes, List<IParameterizedMember> methods, IMember nonMethod)
      {
        this.DeclaringType = declaringType;
        this.NestedTypes = nestedTypes;
        this.Methods = methods;
        this.NonMethod = nonMethod;
        this.MethodsAreHidden = (methods == null || methods.Count == 0);
        this.NonMethodIsHidden = (nonMethod == null);
      }
      
      public bool AllHidden {
        get {
          if (NestedTypes != null && NestedTypes.Count > 0)
            return false;
          return NonMethodIsHidden && MethodsAreHidden;
        }
      }
    }
    #endregion
    
    #region LookupType
    public ResolveResult LookupType(IType declaringType, string name, IList<IType> typeArguments, bool parameterizeResultType = true)
    {
      if (declaringType == null)
        throw new ArgumentNullException("declaringType");
      if (name == null)
        throw new ArgumentNullException("name");
      if (typeArguments == null)
        throw new ArgumentNullException("typeArguments");
      
      int typeArgumentCount = typeArguments.Count;
      Predicate<ITypeDefinition> filter = delegate (ITypeDefinition d) {
        return InnerTypeParameterCount(d) == typeArgumentCount && d.Name == name && IsAccessible(d, true);
      };
      
      List<LookupGroup> lookupGroups = new List<LookupGroup>();
      if (declaringType.Kind != TypeKind.TypeParameter) {
        foreach (IType type in declaringType.GetNonInterfaceBaseTypes()) {
          List<IType> newNestedTypes = null;
          IEnumerable<IType> typeBaseTypes = null;
          
          IEnumerable<IType> nestedTypes;
          if (parameterizeResultType) {
            nestedTypes = type.GetNestedTypes(typeArguments, filter, GetMemberOptions.IgnoreInheritedMembers);
          } else {
            nestedTypes = type.GetNestedTypes(filter, GetMemberOptions.IgnoreInheritedMembers | GetMemberOptions.ReturnMemberDefinitions);
          }
          AddNestedTypes(type, nestedTypes, typeArgumentCount, lookupGroups, ref typeBaseTypes, ref newNestedTypes);
          
          if (newNestedTypes != null)
            lookupGroups.Add(new LookupGroup(type, newNestedTypes, null, null));
        }
      }
      
      lookupGroups.RemoveAll(g => g.AllHidden);
      Debug.Assert(lookupGroups.All(g => g.NestedTypes != null && g.NestedTypes.Count > 0));
      
      if (lookupGroups.Count == 0) {
        return new UnknownMemberResolveResult(declaringType, name, typeArguments);
      }
      
      LookupGroup resultGroup = lookupGroups[lookupGroups.Count - 1];
      
      if (resultGroup.NestedTypes.Count > 1 || lookupGroups.Count > 1)
        return new AmbiguousTypeResolveResult(resultGroup.NestedTypes[0]);
      else
        return new TypeResolveResult(resultGroup.NestedTypes[0]);
    }
    
    static int InnerTypeParameterCount(IType type)
    {
      // inner types contain the type parameters of outer types. therefore this count has to been adjusted.
      return type.TypeParameterCount - (type.DeclaringType != null ? type.DeclaringType.TypeParameterCount : 0);
    }
    #endregion
    
    #region Lookup
    /// <summary>
    /// Performs a member lookup.
    /// </summary>
    public ResolveResult Lookup(ResolveResult targetResolveResult, string name, IList<IType> typeArguments, bool isInvocation)
    {
      if (targetResolveResult == null)
        throw new ArgumentNullException("targetResolveResult");
      if (name == null)
        throw new ArgumentNullException("name");
      if (typeArguments == null)
        throw new ArgumentNullException("typeArguments");
      
      bool targetIsTypeParameter = targetResolveResult.Type.Kind == TypeKind.TypeParameter;
      
      bool allowProtectedAccess = IsProtectedAccessAllowed(targetResolveResult);
      Predicate<ITypeDefinition> nestedTypeFilter = delegate(ITypeDefinition entity) {
        return entity.Name == name && IsAccessible(entity, allowProtectedAccess);
      };
      Predicate<IUnresolvedMember> memberFilter = delegate(IUnresolvedMember entity) {
        // NOTE: Atm destructors can be looked up with 'Finalize'
        return entity.SymbolKind != SymbolKind.Indexer &&
               entity.SymbolKind != SymbolKind.Operator && 
               entity.Name == name;
      };
      
      List<LookupGroup> lookupGroups = new List<LookupGroup>();
      // This loop will handle base types before derived types.
      // The loop performs three jobs:
      // 1) It marks entries in lookup groups from base classes as removed when those members
      //    are hidden by a derived class.
      // 2) It adds a new lookup group with the members from a declaring type.
      // 3) It replaces virtual members with the overridden version, placing the override in the
      //    lookup group belonging to the base class.
      foreach (IType type in targetResolveResult.Type.GetNonInterfaceBaseTypes()) {
        
        List<IType> newNestedTypes = null;
        List<IParameterizedMember> newMethods = null;
        IMember newNonMethod = null;
        
        IEnumerable<IType> typeBaseTypes = null;
        
        if (!isInvocation && !targetIsTypeParameter) {
          // Consider nested types only if it's not an invocation.
          // type.GetNestedTypes() is checking the type parameter count for an exact match,
          // so we don't need to do that in our filter.
          var nestedTypes = type.GetNestedTypes(typeArguments, nestedTypeFilter, GetMemberOptions.IgnoreInheritedMembers);
          AddNestedTypes(type, nestedTypes, typeArguments.Count, lookupGroups, ref typeBaseTypes, ref newNestedTypes);
        }
        
        IEnumerable<IMember> members;
        if (typeArguments.Count == 0) {
          // Note: IsInvocable-checking cannot be done as part of the filter;
          // because it must be done after type substitution.
          members = type.GetMembers(memberFilter, GetMemberOptions.IgnoreInheritedMembers);
          if (isInvocation)
            members = members.Where(m => IsInvocable(m));
        } else {
          // No need to check for isInvocation/isInvocable here:
          // we only fetch methods
          members = type.GetMethods(typeArguments, memberFilter, GetMemberOptions.IgnoreInheritedMembers);
        }
        AddMembers(type, members, allowProtectedAccess, lookupGroups, false, ref typeBaseTypes, ref newMethods, ref newNonMethod);
        
        if (newNestedTypes != null || newMethods != null || newNonMethod != null)
          lookupGroups.Add(new LookupGroup(type, newNestedTypes, newMethods, newNonMethod));
      }
      
      // Remove interface members hidden by class members.
      if (targetIsTypeParameter) {
        // This can happen only with type parameters.
        RemoveInterfaceMembersHiddenByClassMembers(lookupGroups);
      }
      
      return CreateResult(targetResolveResult, lookupGroups, name, typeArguments);
    }
    #endregion
    
    #region Lookup Indexer
    /// <summary>
    /// Looks up the indexers on the target type.
    /// </summary>
    public IList<MethodListWithDeclaringType> LookupIndexers(ResolveResult targetResolveResult)
    {
      if (targetResolveResult == null)
        throw new ArgumentNullException("targetResolveResult");
      
      IType targetType = targetResolveResult.Type;
      bool allowProtectedAccess = IsProtectedAccessAllowed(targetResolveResult);
      Predicate<IUnresolvedProperty> filter = p => p.IsIndexer;
      
      List<LookupGroup> lookupGroups = new List<LookupGroup>();
      foreach (IType type in targetType.GetNonInterfaceBaseTypes()) {
        List<IParameterizedMember> newMethods = null;
        IMember newNonMethod = null;
        
        IEnumerable<IType> typeBaseTypes = null;
        
        var members = type.GetProperties(filter, GetMemberOptions.IgnoreInheritedMembers);
        AddMembers(type, members, allowProtectedAccess, lookupGroups, true, ref typeBaseTypes, ref newMethods, ref newNonMethod);
        
        if (newMethods != null || newNonMethod != null)
          lookupGroups.Add(new LookupGroup(type, null, newMethods, newNonMethod));
      }
      
      // Remove interface members hidden by class members.
      if (targetType.Kind == TypeKind.TypeParameter) {
        // This can happen only with type parameters.
        RemoveInterfaceMembersHiddenByClassMembers(lookupGroups);
      }
      
      // Remove all hidden groups
      lookupGroups.RemoveAll(g => g.MethodsAreHidden || g.Methods.Count == 0);
      
      MethodListWithDeclaringType[] methodLists = new MethodListWithDeclaringType[lookupGroups.Count];
      for (int i = 0; i < methodLists.Length; i++) {
        methodLists[i] = new MethodListWithDeclaringType(lookupGroups[i].DeclaringType, lookupGroups[i].Methods);
      }
      return methodLists;
    }
    #endregion
    
    #region AddNestedTypes
    /// <summary>
    /// Adds the nested types to 'newNestedTypes' and removes any hidden members from the existing lookup groups.
    /// </summary>
    /// <param name="type">Declaring type of the nested types</param>
    /// <param name="nestedTypes">List of nested types to add.</param>
    /// <param name="typeArgumentCount">The number of type arguments - used for hiding types from the base class</param>
    /// <param name="lookupGroups">List of existing lookup groups</param>
    /// <param name="typeBaseTypes">The base types of 'type' (initialized on demand)</param>
    /// <param name="newNestedTypes">The target list (created on demand).</param>
    void AddNestedTypes(IType type, IEnumerable<IType> nestedTypes, int typeArgumentCount,
                        List<LookupGroup> lookupGroups,
                        ref IEnumerable<IType> typeBaseTypes,
                        ref List<IType> newNestedTypes)
    {
      foreach (IType nestedType in nestedTypes) {
        // Remove all non-types declared in a base type of 'type',
        // and all types with same number of type parameters declared in a base type of 'type'.
        foreach (var lookupGroup in lookupGroups) {
          if (lookupGroup.AllHidden)
            continue; // everything is already hidden
          if (typeBaseTypes == null)
            typeBaseTypes = type.GetNonInterfaceBaseTypes();
          
          if (typeBaseTypes.Contains(lookupGroup.DeclaringType)) {
            lookupGroup.MethodsAreHidden = true;
            lookupGroup.NonMethodIsHidden = true;
            if (lookupGroup.NestedTypes != null)
              lookupGroup.NestedTypes.RemoveAll(t => InnerTypeParameterCount(t) == typeArgumentCount);
          }
        }
        
        // Add the new nested type.
        if (newNestedTypes == null)
          newNestedTypes = new List<IType>();
        newNestedTypes.Add(nestedType);
      }
    }
    #endregion
    
    #region AddMembers
    /// <summary>
    /// Adds members to 'newMethods'/'newNonMethod'.
    /// Removes any members in the existing lookup groups that were hidden by added members.
    /// Substitutes 'virtual' members in the existing lookup groups for added 'override' members.
    /// </summary>
    /// <param name="type">Declaring type of the members</param>
    /// <param name="members">List of members to add.</param>
    /// <param name="allowProtectedAccess">Whether protected members are accessible</param>
    /// <param name="lookupGroups">List of existing lookup groups</param>
    /// <param name="treatAllParameterizedMembersAsMethods">Whether to treat properties as methods</param>
    /// <param name="typeBaseTypes">The base types of 'type' (initialized on demand)</param>
    /// <param name="newMethods">The target list for methods (created on demand).</param>
    /// <param name="newNonMethod">The target variable for non-method members.</param>
    void AddMembers(IType type, IEnumerable<IMember> members,
                    bool allowProtectedAccess,
                    List<LookupGroup> lookupGroups,
                    bool treatAllParameterizedMembersAsMethods,
                    ref IEnumerable<IType> typeBaseTypes, ref List<IParameterizedMember> newMethods, ref IMember newNonMethod)
    {
      foreach (IMember member in members) {
        if (!IsAccessible(member, allowProtectedAccess))
          continue;
        
        IParameterizedMember method;
        if (treatAllParameterizedMembersAsMethods)
          method = member as IParameterizedMember;
        else
          method = member as IMethod;
        
        bool replacedVirtualMemberWithOverride = false;
        if (member.IsOverride) {
          // Replacing virtual member with override:
          
          // Go backwards so that we find the corresponding virtual member
          // in the most-derived type
          for (int i = lookupGroups.Count - 1; i >= 0 && !replacedVirtualMemberWithOverride; i--) {
            if (typeBaseTypes == null)
              typeBaseTypes = type.GetNonInterfaceBaseTypes();
            
            var lookupGroup = lookupGroups[i];
            if (typeBaseTypes.Contains(lookupGroup.DeclaringType)) {
              if (method != null) {
                // Find the matching method, and replace it with the override
                for (int j = 0; j < lookupGroup.Methods.Count; j++) {
                  if (SignatureComparer.Ordinal.Equals(method, lookupGroup.Methods[j])) {
                    lookupGroup.Methods[j] = method;
                    replacedVirtualMemberWithOverride = true;
                    break;
                  }
                }
              } else {
                // If the member type matches, replace it with the override
                if (lookupGroup.NonMethod != null && lookupGroup.NonMethod.SymbolKind == member.SymbolKind) {
                  lookupGroup.NonMethod = member;
                  replacedVirtualMemberWithOverride = true;
                  break;
                }
              }
            }
          }
        }
        // If the member wasn't an override, or if we didn't find any matching virtual method,
        // proceed to add the member.
        if (!replacedVirtualMemberWithOverride) {
          // Make the member hide other members:
          foreach (var lookupGroup in lookupGroups) {
            if (lookupGroup.AllHidden)
              continue; // everything is already hidden
            if (typeBaseTypes == null)
              typeBaseTypes = type.GetNonInterfaceBaseTypes();
            
            if (typeBaseTypes.Contains(lookupGroup.DeclaringType)) {
              // Methods hide all non-methods; Non-methods hide everything
              lookupGroup.NestedTypes = null;
              lookupGroup.NonMethodIsHidden = true;
              if (method == null) { // !(member is IMethod)
                lookupGroup.MethodsAreHidden = true;
              }
            }
          }
          
          // Add the new member
          if (method != null) {
            if (newMethods == null)
              newMethods = new List<IParameterizedMember>();
            newMethods.Add(method);
          } else {
            newNonMethod = member;
          }
        }
      }
    }
    #endregion
    
    #region RemoveInterfaceMembersHiddenByClassMembers
    void RemoveInterfaceMembersHiddenByClassMembers(List<LookupGroup> lookupGroups)
    {
      foreach (var classLookupGroup in lookupGroups) {
        if (IsInterfaceOrSystemObject(classLookupGroup.DeclaringType))
          continue;
        // The current lookup groups contains class members that might hide interface members
        bool hasNestedTypes = classLookupGroup.NestedTypes != null && classLookupGroup.NestedTypes.Count > 0;
        if (hasNestedTypes || !classLookupGroup.NonMethodIsHidden) {
          // Hide all members from interface types
          foreach (var interfaceLookupGroup in lookupGroups) {
            if (IsInterfaceOrSystemObject(interfaceLookupGroup.DeclaringType)) {
              interfaceLookupGroup.NestedTypes = null;
              interfaceLookupGroup.NonMethodIsHidden = true;
              interfaceLookupGroup.MethodsAreHidden = true;
            }
          }
        } else if (!classLookupGroup.MethodsAreHidden) {
          foreach (var classMethod in classLookupGroup.Methods) {
            // Hide all non-methods from interface types, and all methods with the same signature
            // as a method in this class type.
            foreach (var interfaceLookupGroup in lookupGroups) {
              if (IsInterfaceOrSystemObject(interfaceLookupGroup.DeclaringType)) {
                interfaceLookupGroup.NestedTypes = null;
                interfaceLookupGroup.NonMethodIsHidden = true;
                if (interfaceLookupGroup.Methods != null && !interfaceLookupGroup.MethodsAreHidden) {
                  // The mapping of virtual to overridden methods is already done,
                  // so we can simply remove the methods from the collection
                  interfaceLookupGroup.Methods.RemoveAll(
                    m => SignatureComparer.Ordinal.Equals(classMethod, m));
                }
              }
            }
          }
        }
      }
    }
    
    static bool IsInterfaceOrSystemObject(IType type)
    {
      // return true if type is an interface or System.Object
      if (type.Kind == TypeKind.Interface)
        return true;
      ITypeDefinition d = type.GetDefinition();
      return d != null && d.KnownTypeCode == KnownTypeCode.Object;
    }
    #endregion
    
    #region CreateResult
    ResolveResult CreateResult(ResolveResult targetResolveResult, List<LookupGroup> lookupGroups, string name, IList<IType> typeArguments)
    {
      // Remove all hidden groups
      lookupGroups.RemoveAll(g => g.AllHidden);
      
      if (lookupGroups.Count == 0) {
        // No members found
        return new UnknownMemberResolveResult(targetResolveResult.Type, name, typeArguments);
      }
      
      if (lookupGroups.Any(g => !g.MethodsAreHidden && g.Methods.Count > 0)) {
        // If there are methods, make a MethodGroupResolveResult.
        // Note that a conflict between a member and a method (possible with multiple interface inheritance)
        // is only a warning, not an error, and the C# compiler will prefer the method group.
        List<MethodListWithDeclaringType> methodLists = new List<MethodListWithDeclaringType>();
        foreach (var lookupGroup in lookupGroups) {
          if (!lookupGroup.MethodsAreHidden && lookupGroup.Methods.Count > 0) {
            var methodListWithDeclType = new MethodListWithDeclaringType(lookupGroup.DeclaringType);
            foreach (var method in lookupGroup.Methods) {
              methodListWithDeclType.Add((IMethod)method);
            }
            methodLists.Add(methodListWithDeclType);
          }
        }
        
        return new MethodGroupResolveResult(targetResolveResult, name, methodLists, typeArguments);
      }
      
      // If there are ambiguities, report the most-derived result (last group)
      LookupGroup resultGroup = lookupGroups[lookupGroups.Count - 1];
      if (resultGroup.NestedTypes != null && resultGroup.NestedTypes.Count > 0) {
        if (resultGroup.NestedTypes.Count > 1 || !resultGroup.NonMethodIsHidden || lookupGroups.Count > 1)
          return new AmbiguousTypeResolveResult(resultGroup.NestedTypes[0]);
        else
          return new TypeResolveResult(resultGroup.NestedTypes[0]);
      }
      
      if (resultGroup.NonMethod.IsStatic && targetResolveResult is ThisResolveResult) {
        targetResolveResult = new TypeResolveResult(targetResolveResult.Type);
      }
      
      if (lookupGroups.Count > 1) {
        return new AmbiguousMemberResolveResult(targetResolveResult, resultGroup.NonMethod);
      } else {
        if (isInEnumMemberInitializer) {
          IField field = resultGroup.NonMethod as IField;
          if (field != null && field.DeclaringTypeDefinition != null && field.DeclaringTypeDefinition.Kind == TypeKind.Enum) {
            return new MemberResolveResult(
              targetResolveResult, field,
              field.DeclaringTypeDefinition.EnumUnderlyingType,
              field.IsConst, field.ConstantValue);
          }
        }
        return new MemberResolveResult(targetResolveResult, resultGroup.NonMethod);
      }
    }
    #endregion
  }
}