source: branches/2817-BinPackingSpeedup/HeuristicLab.ExtLibs/HeuristicLab.NRefactory/5.5.0/NRefactory.CSharp-5.5.0/Parser/mcs/import.cs

//
// import.cs: System.Reflection conversions
//
// Authors: Marek Safar (marek.safar@gmail.com)
//
// Dual licensed under the terms of the MIT X11 or GNU GPL
//
// Copyright 2009-2011 Novell, Inc
// Copyright 2011-2012 Xamarin, Inc (http://www.xamarin.com)
//

using System;
using System.Runtime.CompilerServices;
using System.Linq;
using System.Collections.Generic;

#if STATIC
using MetaType = IKVM.Reflection.Type;
using IKVM.Reflection;
using IKVM.Reflection.Emit;
#else
using MetaType = System.Type;
using System.Reflection;
using System.Reflection.Emit;
#endif

namespace Mono.CSharp
{
  public abstract class MetadataImporter
  {
    //
    // Dynamic types reader with additional logic to reconstruct a dynamic
    // type using DynamicAttribute values
    //
    protected struct DynamicTypeReader
    {
      static readonly bool[] single_attribute = { true };

      public int Position;
      bool[] flags;

      // There is no common type for CustomAttributeData and we cannot
      // use ICustomAttributeProvider
      object provider;

      //
      // A member provider which can be used to get CustomAttributeData
      //
      public DynamicTypeReader (object provider)
      {
        Position = 0;
        flags = null;
        this.provider = provider;
      }

      //
      // Returns true when object at local position has dynamic attribute flag
      //
      public bool IsDynamicObject ()
      {
        if (provider != null)
          ReadAttribute ();

        return flags != null && Position < flags.Length && flags[Position];
      }

      //
      // Returns true when DynamicAttribute exists
      //
      public bool HasDynamicAttribute ()
      {
        if (provider != null)
          ReadAttribute ();

        return flags != null;
      }

      IList<CustomAttributeData> GetCustomAttributes ()
      {
        var mi = provider as MemberInfo;
        if (mi != null)
          return CustomAttributeData.GetCustomAttributes (mi);

        var pi = provider as ParameterInfo;
        if (pi != null)
          return CustomAttributeData.GetCustomAttributes (pi);

        provider = null;
        return null;
      }

      void ReadAttribute ()
      {
        var cad = GetCustomAttributes ();
        if (cad == null) {
          return;
        }

        if (cad.Count > 0) {
          foreach (var ca in cad) {
            var dt = ca.Constructor.DeclaringType;
            if (dt.Name != "DynamicAttribute" || dt.Namespace != CompilerServicesNamespace)
              continue;

            if (ca.ConstructorArguments.Count == 0) {
              flags = single_attribute;
              break;
            }

            var arg_type = ca.ConstructorArguments[0].ArgumentType;

            if (arg_type.IsArray && MetaType.GetTypeCode (arg_type.GetElementType ()) == TypeCode.Boolean) {
              var carg = (IList<CustomAttributeTypedArgument>) ca.ConstructorArguments[0].Value;
              flags = new bool[carg.Count];
              for (int i = 0; i < flags.Length; ++i) {
                if (MetaType.GetTypeCode (carg[i].ArgumentType) == TypeCode.Boolean)
                  flags[i] = (bool) carg[i].Value;
              }

              break;
            }
          }
        }

        provider = null;
      }
    }

    protected readonly Dictionary<MetaType, TypeSpec> import_cache;
    protected readonly Dictionary<MetaType, TypeSpec> compiled_types;
    protected readonly Dictionary<Assembly, IAssemblyDefinition> assembly_2_definition;
    protected readonly ModuleContainer module;

    public static readonly string CompilerServicesNamespace = "System.Runtime.CompilerServices";

    protected MetadataImporter (ModuleContainer module)
    {
      this.module = module;

      import_cache = new Dictionary<MetaType, TypeSpec> (1024, ReferenceEquality<MetaType>.Default);
      compiled_types = new Dictionary<MetaType, TypeSpec> (40, ReferenceEquality<MetaType>.Default);
      assembly_2_definition = new Dictionary<Assembly, IAssemblyDefinition> (ReferenceEquality<Assembly>.Default);
      IgnorePrivateMembers = true;
    }

    #region Properties

    public ICollection<IAssemblyDefinition> Assemblies {
      get {
        return assembly_2_definition.Values;
      }
    }

    public bool IgnorePrivateMembers { get; set; }

    #endregion

    public abstract void AddCompiledType (TypeBuilder builder, TypeSpec spec);
    protected abstract MemberKind DetermineKindFromBaseType (MetaType baseType);
    protected abstract bool HasVolatileModifier (MetaType[] modifiers);

    public FieldSpec CreateField (FieldInfo fi, TypeSpec declaringType)
    {
      Modifiers mod;
      var fa = fi.Attributes;
      switch (fa & FieldAttributes.FieldAccessMask) {
        case FieldAttributes.Public:
          mod = Modifiers.PUBLIC;
          break;
        case FieldAttributes.Assembly:
          mod = Modifiers.INTERNAL;
          break;
        case FieldAttributes.Family:
          mod = Modifiers.PROTECTED;
          break;
        case FieldAttributes.FamORAssem:
          mod = Modifiers.PROTECTED | Modifiers.INTERNAL;
          break;
        default:
          // Ignore private fields (even for error reporting) to not require extra dependencies
          if ((IgnorePrivateMembers && !declaringType.IsStruct) ||
            HasAttribute (CustomAttributeData.GetCustomAttributes (fi), "CompilerGeneratedAttribute", CompilerServicesNamespace))
            return null;

          mod = Modifiers.PRIVATE;
          break;
      }

      TypeSpec field_type;

      try {
        field_type = ImportType (fi.FieldType, new DynamicTypeReader (fi));

        //
        // Private field has private type which is not fixed buffer
        //
        if (field_type == null)
          return null;
      } catch (Exception e) {
        // TODO: I should construct fake TypeSpec based on TypeRef signature
        // but there is no way to do it with System.Reflection
        throw new InternalErrorException (e, "Cannot import field `{0}.{1}' referenced in assembly `{2}'",
          declaringType.GetSignatureForError (), fi.Name, declaringType.MemberDefinition.DeclaringAssembly);
      }

      var definition = new ImportedMemberDefinition (fi, field_type, this);

      if ((fa & FieldAttributes.Literal) != 0) {
        Constant c = field_type.Kind == MemberKind.MissingType ?
          new NullConstant (InternalType.ErrorType, Location.Null) :
          Constant.CreateConstantFromValue (field_type, fi.GetRawConstantValue (), Location.Null);
        return new ConstSpec (declaringType, definition, field_type, fi, mod, c);
      }

      if ((fa & FieldAttributes.InitOnly) != 0) {
        if (field_type.BuiltinType == BuiltinTypeSpec.Type.Decimal) {
          var dc = ReadDecimalConstant (CustomAttributeData.GetCustomAttributes (fi));
          if (dc != null)
            return new ConstSpec (declaringType, definition, field_type, fi, mod, dc);
        }

        mod |= Modifiers.READONLY;
      } else {
        var req_mod = fi.GetRequiredCustomModifiers ();
        if (req_mod.Length > 0 && HasVolatileModifier (req_mod))
          mod |= Modifiers.VOLATILE;
      }

      if ((fa & FieldAttributes.Static) != 0) {
        mod |= Modifiers.STATIC;
      } else {
        // Fixed buffers cannot be static
        if (declaringType.IsStruct && field_type.IsStruct && field_type.IsNested &&
          HasAttribute (CustomAttributeData.GetCustomAttributes (fi), "FixedBufferAttribute", CompilerServicesNamespace)) {

          // TODO: Sanity check on field_type (only few types are allowed)
          var element_field = CreateField (fi.FieldType.GetField (FixedField.FixedElementName), declaringType);
          return new FixedFieldSpec (module, declaringType, definition, fi, element_field, mod);
        }
      }

      return new FieldSpec (declaringType, definition, field_type, fi, mod);
    }

    public EventSpec CreateEvent (EventInfo ei, TypeSpec declaringType, MethodSpec add, MethodSpec remove)
    {
      add.IsAccessor = true;
      remove.IsAccessor = true;

      if (add.Modifiers != remove.Modifiers)
        throw new NotImplementedException ("Different accessor modifiers " + ei.Name);

      var event_type = ImportType (ei.EventHandlerType, new DynamicTypeReader (ei));
      var definition = new ImportedMemberDefinition (ei, event_type,  this);
      return new EventSpec (declaringType, definition, event_type, add.Modifiers, add, remove);
    }

    TypeParameterSpec[] CreateGenericParameters (MetaType type, TypeSpec declaringType)
    {
      var tparams = type.GetGenericArguments ();

      int parent_owned_count;
      if (type.IsNested) {
        parent_owned_count = type.DeclaringType.GetGenericArguments ().Length;

        //
        // System.Reflection duplicates parent type parameters for each
        // nested type with slightly modified properties (eg. different owner)
        // This just makes things more complicated (think of cloned constraints)
        // therefore we remap any nested type owned by parent using `type_cache'
        // to the single TypeParameterSpec
        //
        if (declaringType != null && parent_owned_count > 0) {
          int read_count = 0;
          while (read_count != parent_owned_count) {
            var tparams_count = declaringType.Arity;
            if (tparams_count != 0) {
              var parent_tp = declaringType.MemberDefinition.TypeParameters;
              read_count += tparams_count;
              for (int i = 0; i < tparams_count; i++) {
                import_cache.Add (tparams[parent_owned_count - read_count + i], parent_tp[i]);
              }
            }

            declaringType = declaringType.DeclaringType;
          }
        }     
      } else {
        parent_owned_count = 0;
      }

      if (tparams.Length - parent_owned_count == 0)
        return null;

      return CreateGenericParameters (parent_owned_count, tparams);
    }

    TypeParameterSpec[] CreateGenericParameters (int first, MetaType[] tparams)
    {
      var tspec = new TypeParameterSpec[tparams.Length - first];
      for (int pos = first; pos < tparams.Length; ++pos) {
        var type = tparams[pos];
        int index = pos - first;

        tspec[index] = (TypeParameterSpec) CreateType (type, new DynamicTypeReader (), false);
      }

      return tspec;
    }

    TypeSpec[] CreateGenericArguments (int first, MetaType[] tparams, DynamicTypeReader dtype)
    {
      ++dtype.Position;

      var tspec = new TypeSpec [tparams.Length - first];
      for (int pos = first; pos < tparams.Length; ++pos) {
        var type = tparams[pos];
        int index = pos - first;

        TypeSpec spec;
        if (type.HasElementType) {
          var element = type.GetElementType ();
          ++dtype.Position;
          spec = ImportType (element, dtype);

          if (!type.IsArray) {
            throw new NotImplementedException ("Unknown element type " + type.ToString ());
          }

          spec = ArrayContainer.MakeType (module, spec, type.GetArrayRank ());
        } else {
          spec = CreateType (type, dtype, true);

          //
          // We treat nested generic types as inflated internally where
          // reflection uses type definition
          //
          // class A<T> {
          //    IFoo<A<T>> foo; // A<T> is definition in this case
          // }
          //
          if (!IsMissingType (type) && type.IsGenericTypeDefinition) {
            var start_pos = spec.DeclaringType == null ? 0 : spec.DeclaringType.MemberDefinition.TypeParametersCount;
            var targs = CreateGenericArguments (start_pos, type.GetGenericArguments (), dtype);
            spec = spec.MakeGenericType (module, targs);
          }
        }

        if (spec == null)
          return null;

        ++dtype.Position;
        tspec[index] = spec;
      }

      return tspec;
    }

    public MethodSpec CreateMethod (MethodBase mb, TypeSpec declaringType)
    {
      Modifiers mod = ReadMethodModifiers (mb, declaringType);
      TypeParameterSpec[] tparams;

      var parameters = CreateParameters (declaringType, mb.GetParameters (), mb);

      if (mb.IsGenericMethod) {
        if (!mb.IsGenericMethodDefinition)
          throw new NotSupportedException ("assert");

        tparams = CreateGenericParameters (0, mb.GetGenericArguments ());
      } else {
        tparams = null;
      }

      MemberKind kind;
      TypeSpec returnType;
      if (mb.MemberType == MemberTypes.Constructor) {
        kind = MemberKind.Constructor;
        returnType = module.Compiler.BuiltinTypes.Void;
      } else {
        //
        // Detect operators and destructors
        //
        string name = mb.Name;
        kind = MemberKind.Method;
        if (tparams == null && !mb.DeclaringType.IsInterface && name.Length > 6) {
          if ((mod & (Modifiers.STATIC | Modifiers.PUBLIC)) == (Modifiers.STATIC | Modifiers.PUBLIC)) {
            if (name[2] == '_' && name[1] == 'p' && name[0] == 'o' && (mb.Attributes & MethodAttributes.SpecialName) != 0) {
              var op_type = Operator.GetType (name);
              if (op_type.HasValue && parameters.Count > 0 && parameters.Count < 3) {
                kind = MemberKind.Operator;
              }
            }
          } else if (parameters.IsEmpty && name == Destructor.MetadataName) {
            kind = MemberKind.Destructor;
            if (declaringType.BuiltinType == BuiltinTypeSpec.Type.Object) {
              mod &= ~Modifiers.OVERRIDE;
              mod |= Modifiers.VIRTUAL;
            }
          }
        }

        var mi = (MethodInfo) mb;
        returnType = ImportType (mi.ReturnType, new DynamicTypeReader (mi.ReturnParameter));

        // Cannot set to OVERRIDE without full hierarchy checks
        // this flag indicates that the method could be override
        // but further validation is needed
        if ((mod & Modifiers.OVERRIDE) != 0) {
          bool is_real_override = false;
          if (kind == MemberKind.Method && declaringType.BaseType != null) {
            var btype = declaringType.BaseType;
            if (IsOverrideMethodBaseTypeAccessible (btype)) {
              var filter = MemberFilter.Method (name, tparams != null ? tparams.Length : 0, parameters, null);
              var candidate = MemberCache.FindMember (btype, filter, BindingRestriction.None);

              //
              // For imported class method do additional validation to be sure that metadata
              // override flag was correct
              // 
              // Difference between protected internal and protected is ok
              //
              const Modifiers conflict_mask = Modifiers.AccessibilityMask & ~Modifiers.INTERNAL;
              if (candidate != null && (candidate.Modifiers & conflict_mask) == (mod & conflict_mask) && !candidate.IsStatic) {
                is_real_override = true;
              }
            }
          }

          if (!is_real_override) {
            mod &= ~Modifiers.OVERRIDE;
            if ((mod & Modifiers.SEALED) != 0)
              mod &= ~Modifiers.SEALED;
            else
              mod |= Modifiers.VIRTUAL;
          }
        } else if (parameters.HasExtensionMethodType) {
          mod |= Modifiers.METHOD_EXTENSION;
        }
      }

      IMethodDefinition definition;
      if (tparams != null) {
        var gmd = new ImportedGenericMethodDefinition ((MethodInfo) mb, returnType, parameters, tparams, this);
        foreach (var tp in gmd.TypeParameters) {
          ImportTypeParameterTypeConstraints (tp, tp.GetMetaInfo ());
        }

        definition = gmd;
      } else {
        definition = new ImportedMethodDefinition (mb, returnType, parameters, this);
      }

      MethodSpec ms = new MethodSpec (kind, declaringType, definition, returnType, parameters, mod);
      if (tparams != null)
        ms.IsGeneric = true;

      return ms;
    }

    bool IsOverrideMethodBaseTypeAccessible (TypeSpec baseType)
    {
      switch (baseType.Modifiers & Modifiers.AccessibilityMask) {
      case Modifiers.PUBLIC:
        return true;
      case Modifiers.INTERNAL:
        //
        // Check whether imported method in base type is accessible from compiled
        // context
        //
        return baseType.MemberDefinition.IsInternalAsPublic (module.DeclaringAssembly);
      case Modifiers.PRIVATE:
        return false;
      default:
        // protected
        // protected internal
        // 
        // Method accessibility checks will be done later based on context
        // where the method is called (CS0122 error will be reported for inaccessible)
        //
        return true;
      }
    }

    //
    // Imports System.Reflection parameters
    //
    AParametersCollection CreateParameters (TypeSpec parent, ParameterInfo[] pi, MethodBase method)
    {
      int varargs = method != null && (method.CallingConvention & CallingConventions.VarArgs) != 0 ? 1 : 0;

      if (pi.Length == 0 && varargs == 0)
        return ParametersCompiled.EmptyReadOnlyParameters;

      TypeSpec[] types = new TypeSpec[pi.Length + varargs];
      IParameterData[] par = new IParameterData[pi.Length + varargs];
      bool is_params = false;
      for (int i = 0; i < pi.Length; i++) {
        ParameterInfo p = pi[i];
        Parameter.Modifier mod = 0;
        Expression default_value = null;
        if (p.ParameterType.IsByRef) {
          if ((p.Attributes & (ParameterAttributes.Out | ParameterAttributes.In)) == ParameterAttributes.Out)
            mod = Parameter.Modifier.OUT;
          else
            mod = Parameter.Modifier.REF;

          //
          // Strip reference wrapping
          //
          var el = p.ParameterType.GetElementType ();
          types[i] = ImportType (el, new DynamicTypeReader (p));  // TODO: 1-based positio to be csc compatible
        } else if (i == 0 && method.IsStatic && (parent.Modifiers & Modifiers.METHOD_EXTENSION) != 0 &&
          HasAttribute (CustomAttributeData.GetCustomAttributes (method), "ExtensionAttribute", CompilerServicesNamespace)) {
          mod = Parameter.Modifier.This;
          types[i] = ImportType (p.ParameterType, new DynamicTypeReader (p));
        } else {
          types[i] = ImportType (p.ParameterType, new DynamicTypeReader (p));

          if (i >= pi.Length - 2 && types[i] is ArrayContainer) {
            if (HasAttribute (CustomAttributeData.GetCustomAttributes (p), "ParamArrayAttribute", "System")) {
              mod = Parameter.Modifier.PARAMS;
              is_params = true;
            }
          }

          if (!is_params && p.IsOptional) {
            object value = p.RawDefaultValue;
            var ptype = types[i];
            if ((p.Attributes & ParameterAttributes.HasDefault) != 0 && ptype.Kind != MemberKind.TypeParameter && (value != null || TypeSpec.IsReferenceType (ptype))) {
              if (value == null) {
                default_value = Constant.CreateConstantFromValue (ptype, null, Location.Null);
              } else {
                default_value = ImportParameterConstant (value);

                if (ptype.IsEnum) {
                  default_value = new EnumConstant ((Constant) default_value, ptype);
                }
              }

              var attrs = CustomAttributeData.GetCustomAttributes (p);
              for (int ii = 0; ii < attrs.Count; ++ii) {
                var attr = attrs[ii];
                var dt = attr.Constructor.DeclaringType;
                if (dt.Namespace != CompilerServicesNamespace)
                  continue;

                if (dt.Name == "CallerLineNumberAttribute" && (ptype.BuiltinType == BuiltinTypeSpec.Type.Int || Convert.ImplicitNumericConversionExists (module.Compiler.BuiltinTypes.Int, ptype)))
                  mod |= Parameter.Modifier.CallerLineNumber;
                else if (dt.Name == "CallerFilePathAttribute" && Convert.ImplicitReferenceConversionExists (module.Compiler.BuiltinTypes.String, ptype))
                  mod |= Parameter.Modifier.CallerFilePath;
                else if (dt.Name == "CallerMemberNameAttribute" && Convert.ImplicitReferenceConversionExists (module.Compiler.BuiltinTypes.String, ptype))
                  mod |= Parameter.Modifier.CallerMemberName;
              }
            } else if (value == Missing.Value) {
              default_value = EmptyExpression.MissingValue;
            } else if (value == null) {
              default_value = new DefaultValueExpression (new TypeExpression (ptype, Location.Null), Location.Null);
            } else if (ptype.BuiltinType == BuiltinTypeSpec.Type.Decimal) {
              default_value = ImportParameterConstant (value);
            }
          }
        }

        par[i] = new ParameterData (p.Name, mod, default_value);
      }

      if (varargs != 0) {
        par[par.Length - 1] = new ArglistParameter (Location.Null);
        types[types.Length - 1] = InternalType.Arglist;
      }

      return method != null ?
        new ParametersImported (par, types, varargs != 0, is_params) :
        new ParametersImported (par, types, is_params);
    }

    //
    // Returns null when the property is not valid C# property
    //
    public PropertySpec CreateProperty (PropertyInfo pi, TypeSpec declaringType, MethodSpec get, MethodSpec set)
    {
      Modifiers mod = 0;
      AParametersCollection param = null;
      TypeSpec type = null;
      if (get != null) {
        mod = get.Modifiers;
        param = get.Parameters;
        type = get.ReturnType;
      }

      bool is_valid_property = true;
      if (set != null) {
        if (set.ReturnType.Kind != MemberKind.Void)
          is_valid_property = false;

        var set_param_count = set.Parameters.Count - 1;

        if (set_param_count < 0) {
          set_param_count = 0;
          is_valid_property = false;
        }

        var set_type = set.Parameters.Types[set_param_count];

        if (mod == 0) {
          AParametersCollection set_based_param;

          if (set_param_count == 0) {
            set_based_param = ParametersCompiled.EmptyReadOnlyParameters;
          } else {
            //
            // Create indexer parameters based on setter method parameters (the last parameter has to be removed)
            //
            var data = new IParameterData[set_param_count];
            var types = new TypeSpec[set_param_count];
            Array.Copy (set.Parameters.FixedParameters, data, set_param_count);
            Array.Copy (set.Parameters.Types, types, set_param_count);
            set_based_param = new ParametersImported (data, types, set.Parameters.HasParams);
          }

          mod = set.Modifiers;
          param = set_based_param;
          type = set_type;
        } else {
          if (set_param_count != get.Parameters.Count)
            is_valid_property = false;

          if (get.ReturnType != set_type)
            is_valid_property = false;

          // Possible custom accessor modifiers
          if ((mod & Modifiers.AccessibilityMask) != (set.Modifiers & Modifiers.AccessibilityMask)) {
            var get_acc = mod & Modifiers.AccessibilityMask;
            if (get_acc != Modifiers.PUBLIC) {
              var set_acc = set.Modifiers & Modifiers.AccessibilityMask;
              // If the accessor modifiers are not same, do extra restriction checks
              if (get_acc != set_acc) {
                var get_restr = ModifiersExtensions.IsRestrictedModifier (get_acc, set_acc);
                var set_restr = ModifiersExtensions.IsRestrictedModifier (set_acc, get_acc);
                if (get_restr && set_restr) {
                  is_valid_property = false; // Neither is more restrictive
                }

                if (get_restr) {
                  mod &= ~Modifiers.AccessibilityMask;
                  mod |= set_acc;
                }
              }
            }
          }
        }
      }

      PropertySpec spec = null;
      if (!param.IsEmpty) {
        if (is_valid_property) {
          var index_name = declaringType.MemberDefinition.GetAttributeDefaultMember ();
          if (index_name == null) {
            is_valid_property = false;
          } else {
            if (get != null) {
              if (get.IsStatic)
                is_valid_property = false;
              if (get.Name.IndexOf (index_name, StringComparison.Ordinal) != 4)
                is_valid_property = false;
            }
            if (set != null) {
              if (set.IsStatic)
                is_valid_property = false;
              if (set.Name.IndexOf (index_name, StringComparison.Ordinal) != 4)
                is_valid_property = false;
            }
          }

          if (is_valid_property) {
            spec = new IndexerSpec (declaringType, new ImportedParameterMemberDefinition (pi, type, param, this), type, param, pi, mod);
          } else if (declaringType.MemberDefinition.IsComImport && param.FixedParameters[0].HasDefaultValue) {
            //
            // Enables support for properties with parameters (must have default value) of COM-imported types
            //
            is_valid_property = true;

            for (int i = 0; i < param.FixedParameters.Length; ++i) {
              if (!param.FixedParameters[i].HasDefaultValue) {
                is_valid_property = false;
                break;
              }
            }
          }
        }
      }

      if (spec == null)
        spec = new PropertySpec (MemberKind.Property, declaringType, new ImportedMemberDefinition (pi, type, this), type, pi, mod);

      if (!is_valid_property) {
        spec.IsNotCSharpCompatible = true;
        return spec;
      }

      if (set != null)
        spec.Set = set;
      if (get != null)
        spec.Get = get;

      return spec;
    }

    public TypeSpec CreateType (MetaType type)
    {
      return CreateType (type, new DynamicTypeReader (), true);
    }

    public TypeSpec CreateNestedType (MetaType type, TypeSpec declaringType)
    {
      return CreateType (type, declaringType, new DynamicTypeReader (type), false);
    }

    TypeSpec CreateType (MetaType type, DynamicTypeReader dtype, bool canImportBaseType)
    {
      TypeSpec declaring_type;
      if (type.IsNested && !type.IsGenericParameter)
        declaring_type = CreateType (type.DeclaringType, new DynamicTypeReader (type.DeclaringType), true);
      else
        declaring_type = null;

      return CreateType (type, declaring_type, dtype, canImportBaseType);
    }

    protected TypeSpec CreateType (MetaType type, TypeSpec declaringType, DynamicTypeReader dtype, bool canImportBaseType)
    {
      TypeSpec spec;
      if (import_cache.TryGetValue (type, out spec)) {
        if (spec.BuiltinType == BuiltinTypeSpec.Type.Object) {
          if (dtype.IsDynamicObject ())
            return module.Compiler.BuiltinTypes.Dynamic;

          return spec;
        }

        if (!spec.IsGeneric || type.IsGenericTypeDefinition)
          return spec;

        if (!dtype.HasDynamicAttribute ())
          return spec;

        // We've found same object in the cache but this one has a dynamic custom attribute
        // and it's most likely dynamic version of same type IFoo<object> agains IFoo<dynamic>
        // Do type resolve process again in that case

        // TODO: Handle cases where they still unify
      }

      if (IsMissingType (type)) {
        spec = new TypeSpec (MemberKind.MissingType, declaringType, new ImportedTypeDefinition (type, this), type, Modifiers.PUBLIC);
        spec.MemberCache = MemberCache.Empty;
        import_cache.Add (type, spec);
        return spec;
      }

      if (type.IsGenericType && !type.IsGenericTypeDefinition) {
        var type_def = type.GetGenericTypeDefinition ();

        // Generic type definition can also be forwarded
        if (compiled_types.TryGetValue (type_def, out spec))
          return spec;

        var targs = CreateGenericArguments (0, type.GetGenericArguments (), dtype);
        if (targs == null)
          return null;
        if (declaringType == null) {
          // Simple case, no nesting
          spec = CreateType (type_def, null, new DynamicTypeReader (), canImportBaseType);
          spec = spec.MakeGenericType (module, targs);
        } else {
          //
          // Nested type case, converting .NET types like
          // A`1.B`1.C`1<int, long, string> to typespec like
          // A<int>.B<long>.C<string>
          //
          var nested_hierarchy = new List<TypeSpec> ();
          while (declaringType.IsNested) {
            nested_hierarchy.Add (declaringType);
            declaringType = declaringType.DeclaringType;
          }

          int targs_pos = 0;
          if (declaringType.Arity > 0) {
            spec = declaringType.MakeGenericType (module, targs.Skip (targs_pos).Take (declaringType.Arity).ToArray ());
            targs_pos = spec.Arity;
          } else {
            spec = declaringType;
          }

          for (int i = nested_hierarchy.Count; i != 0; --i) {
            var t = nested_hierarchy [i - 1];
            if (t.Kind == MemberKind.MissingType)
              spec = t;
            else
              spec = MemberCache.FindNestedType (spec, t.Name, t.Arity);

            if (t.Arity > 0) {
              spec = spec.MakeGenericType (module, targs.Skip (targs_pos).Take (spec.Arity).ToArray ());
              targs_pos += t.Arity;
            }
          }

          if (spec.Kind == MemberKind.MissingType) {
            spec = new TypeSpec (MemberKind.MissingType, spec, new ImportedTypeDefinition (type_def, this), type_def, Modifiers.PUBLIC);
            spec.MemberCache = MemberCache.Empty;
          } else {
            if ((type_def.Attributes & TypeAttributes.VisibilityMask) == TypeAttributes.NestedPrivate && IgnorePrivateMembers)
              return null;

            string name = type.Name;
            int index = name.IndexOf ('`');
            if (index > 0)
              name = name.Substring (0, index);

            spec = MemberCache.FindNestedType (spec, name, targs.Length - targs_pos);

            if (spec.Arity > 0) {
              spec = spec.MakeGenericType (module, targs.Skip (targs_pos).ToArray ());
            }
          }
        }

        // Don't add generic type with dynamic arguments, they can interfere with same type
        // using object type arguments
        if (!spec.HasDynamicElement) {

          // Add to reading cache to speed up reading
          if (!import_cache.ContainsKey (type))
            import_cache.Add (type, spec);
        }

        return spec;
      }

      Modifiers mod;
      MemberKind kind;

      var ma = type.Attributes;
      switch (ma & TypeAttributes.VisibilityMask) {
      case TypeAttributes.Public:
      case TypeAttributes.NestedPublic:
        mod = Modifiers.PUBLIC;
        break;
      case TypeAttributes.NestedPrivate:
        mod = Modifiers.PRIVATE;
        break;
      case TypeAttributes.NestedFamily:
        mod = Modifiers.PROTECTED;
        break;
      case TypeAttributes.NestedFamORAssem:
        mod = Modifiers.PROTECTED | Modifiers.INTERNAL;
        break;
      default:
        mod = Modifiers.INTERNAL;
        break;
      }

      if ((ma & TypeAttributes.Interface) != 0) {
        kind = MemberKind.Interface;
      } else if (type.IsGenericParameter) {
        kind = MemberKind.TypeParameter;
      } else {
        var base_type = type.BaseType;
        if (base_type == null || (ma & TypeAttributes.Abstract) != 0) {
          kind = MemberKind.Class;
        } else {
          kind = DetermineKindFromBaseType (base_type);
          if (kind == MemberKind.Struct || kind == MemberKind.Delegate) {
            mod |= Modifiers.SEALED;
          }
        }

        if (kind == MemberKind.Class) {
          if ((ma & TypeAttributes.Sealed) != 0) {
            if ((ma & TypeAttributes.Abstract) != 0)
              mod |= Modifiers.STATIC;
            else
              mod |= Modifiers.SEALED;
          } else if ((ma & TypeAttributes.Abstract) != 0) {
            mod |= Modifiers.ABSTRACT;
          }
        }
      }

      var definition = new ImportedTypeDefinition (type, this);
      TypeSpec pt;

      if (kind == MemberKind.Enum) {
        const BindingFlags underlying_member = BindingFlags.DeclaredOnly |
          BindingFlags.Instance |
          BindingFlags.Public | BindingFlags.NonPublic;

        var type_members = type.GetFields (underlying_member);
        foreach (var type_member in type_members) {
          spec = new EnumSpec (declaringType, definition, CreateType (type_member.FieldType), type, mod);
          break;
        }

        if (spec == null)
          kind = MemberKind.Class;

      } else if (kind == MemberKind.TypeParameter) {
        spec = CreateTypeParameter (type, declaringType);
      } else if (type.IsGenericTypeDefinition) {
        definition.TypeParameters = CreateGenericParameters (type, declaringType);
      } else if (compiled_types.TryGetValue (type, out pt)) {
        //
        // Same type was found in inside compiled types. It's
        // either build-in type or forward referenced typed
        // which point into just compiled assembly.
        //
        spec = pt;
        BuiltinTypeSpec bts = pt as BuiltinTypeSpec;
        if (bts != null)
          bts.SetDefinition (definition, type, mod);
      }

      if (spec == null)
        spec = new TypeSpec (kind, declaringType, definition, type, mod);

      import_cache.Add (type, spec);

      if (kind == MemberKind.TypeParameter) {
        if (canImportBaseType)
          ImportTypeParameterTypeConstraints ((TypeParameterSpec) spec, type);

        return spec;
      }

      //
      // Two stage setup as the base type can be inflated declaring type or
      // another nested type inside same declaring type which has not been
      // loaded, therefore we can import a base type of nested types once
      // the types have been imported
      //
      if (canImportBaseType)
        ImportTypeBase (spec, type);

      return spec;
    }

    public IAssemblyDefinition GetAssemblyDefinition (Assembly assembly)
    {
      IAssemblyDefinition found;
      if (!assembly_2_definition.TryGetValue (assembly, out found)) {

        // This can happen in dynamic context only
        var def = new ImportedAssemblyDefinition (assembly);
        assembly_2_definition.Add (assembly, def);
        def.ReadAttributes ();
        found = def;
      }

      return found;
    }

    public void ImportTypeBase (MetaType type)
    {
      TypeSpec spec = import_cache[type];
      if (spec != null)
        ImportTypeBase (spec, type);
    }

    TypeParameterSpec CreateTypeParameter (MetaType type, TypeSpec declaringType)
    {
      Variance variance;
      switch (type.GenericParameterAttributes & GenericParameterAttributes.VarianceMask) {
      case GenericParameterAttributes.Covariant:
        variance = Variance.Covariant;
        break;
      case GenericParameterAttributes.Contravariant:
        variance = Variance.Contravariant;
        break;
      default:
        variance = Variance.None;
        break;
      }

      SpecialConstraint special = SpecialConstraint.None;
      var import_special = type.GenericParameterAttributes & GenericParameterAttributes.SpecialConstraintMask;

      if ((import_special & GenericParameterAttributes.NotNullableValueTypeConstraint) != 0) {
        special |= SpecialConstraint.Struct;
      } else if ((import_special & GenericParameterAttributes.DefaultConstructorConstraint) != 0) {
        special = SpecialConstraint.Constructor;
      }

      if ((import_special & GenericParameterAttributes.ReferenceTypeConstraint) != 0) {
        special |= SpecialConstraint.Class;
      }

      TypeParameterSpec spec;
      var def = new ImportedTypeParameterDefinition (type, this);
      if (type.DeclaringMethod != null) {
        spec = new TypeParameterSpec (type.GenericParameterPosition, def, special, variance, type);
      } else {
        spec = new TypeParameterSpec (declaringType, type.GenericParameterPosition, def, special, variance, type);
      }

      return spec;
    }

    //
    // Test for a custom attribute type match. Custom attributes are not really predefined globaly 
    // they can be assembly specific therefore we do check based on names only
    //
    public static bool HasAttribute (IList<CustomAttributeData> attributesData, string attrName, string attrNamespace)
    {
      if (attributesData.Count == 0)
        return false;

      foreach (var attr in attributesData) {
        var dt = attr.Constructor.DeclaringType;
        if (dt.Name == attrName && dt.Namespace == attrNamespace)
          return true;
      }

      return false;
    }

    void ImportTypeBase (TypeSpec spec, MetaType type)
    {
      if (spec.Kind == MemberKind.Interface)
        spec.BaseType = module.Compiler.BuiltinTypes.Object;
      else if (type.BaseType != null) {
        TypeSpec base_type;
        if (!IsMissingType (type.BaseType) && type.BaseType.IsGenericType)
          base_type = CreateType (type.BaseType, new DynamicTypeReader (type), true);
        else
          base_type = CreateType (type.BaseType);

        spec.BaseType = base_type;
      }

      if (spec.MemberDefinition.TypeParametersCount > 0) {
        foreach (var tp in spec.MemberDefinition.TypeParameters) {
          ImportTypeParameterTypeConstraints (tp, tp.GetMetaInfo ());
        }
      }
    }

    protected void ImportTypes (MetaType[] types, Namespace targetNamespace, bool importExtensionTypes)
    {
      Namespace ns = targetNamespace;
      string prev_namespace = null;
      foreach (var t in types) {
        if (t == null)
          continue;

        // Be careful not to trigger full parent type loading
        if (t.MemberType == MemberTypes.NestedType)
          continue;

        if (t.Name[0] == '<')
          continue;

        var it = CreateType (t, null, new DynamicTypeReader (t), true);
        if (it == null)
          continue;

        if (prev_namespace != t.Namespace) {
          ns = t.Namespace == null ? targetNamespace : targetNamespace.GetNamespace (t.Namespace, true);
          prev_namespace = t.Namespace;
        }

        // Cannot rely on assembly level Extension attribute or static modifier because they
        // are not followed by other compilers (e.g. F#).
        if (it.IsClass && it.Arity == 0 && importExtensionTypes &&
          HasAttribute (CustomAttributeData.GetCustomAttributes (t), "ExtensionAttribute", CompilerServicesNamespace)) {
          it.SetExtensionMethodContainer ();
        }

        ns.AddType (module, it);
      }
    }

    void ImportTypeParameterTypeConstraints (TypeParameterSpec spec, MetaType type)
    {
      var constraints = type.GetGenericParameterConstraints ();
      List<TypeSpec> tparams = null;
      foreach (var ct in constraints) {
        if (ct.IsGenericParameter) {
          if (tparams == null)
            tparams = new List<TypeSpec> ();

          tparams.Add (CreateType (ct));
          continue;
        }

        var constraint_type = CreateType (ct);
        if (constraint_type.IsClass) {
          spec.BaseType = constraint_type;
          continue;
        }

        spec.AddInterface (constraint_type);
      }

      if (spec.BaseType == null)
        spec.BaseType = module.Compiler.BuiltinTypes.Object;

      if (tparams != null)
        spec.TypeArguments = tparams.ToArray ();
    }

    Constant ImportParameterConstant (object value)
    {
      //
      // Get type of underlying value as int constant can be used for object
      // parameter type. This is not allowed in C# but other languages can do that
      //
      var types = module.Compiler.BuiltinTypes;
      switch (System.Type.GetTypeCode (value.GetType ())) {
      case TypeCode.Boolean:
        return new BoolConstant (types, (bool) value, Location.Null);
      case TypeCode.Byte:
        return new ByteConstant (types, (byte) value, Location.Null);
      case TypeCode.Char:
        return new CharConstant (types, (char) value, Location.Null);
      case TypeCode.Decimal:
        return new DecimalConstant (types, (decimal) value, Location.Null);
      case TypeCode.Double:
        return new DoubleConstant (types, (double) value, Location.Null);
      case TypeCode.Int16:
        return new ShortConstant (types, (short) value, Location.Null);
      case TypeCode.Int32:
        return new IntConstant (types, (int) value, Location.Null);
      case TypeCode.Int64:
        return new LongConstant (types, (long) value, Location.Null);
      case TypeCode.SByte:
        return new SByteConstant (types, (sbyte) value, Location.Null);
      case TypeCode.Single:
        return new FloatConstant (types, (float) value, Location.Null);
      case TypeCode.String:
        return new StringConstant (types, (string) value, Location.Null);
      case TypeCode.UInt16:
        return new UShortConstant (types, (ushort) value, Location.Null);
      case TypeCode.UInt32:
        return new UIntConstant (types, (uint) value, Location.Null);
      case TypeCode.UInt64:
        return new ULongConstant (types, (ulong) value, Location.Null);
      }

      throw new NotImplementedException (value.GetType ().ToString ());
    }

    public TypeSpec ImportType (MetaType type)
    {
      return ImportType (type, new DynamicTypeReader (type));
    }

    TypeSpec ImportType (MetaType type, DynamicTypeReader dtype)
    {
      if (type.HasElementType) {
        var element = type.GetElementType ();
        ++dtype.Position;
        var spec = ImportType (element, dtype);

        if (type.IsArray)
          return ArrayContainer.MakeType (module, spec, type.GetArrayRank ());
        if (type.IsByRef)
          return ReferenceContainer.MakeType (module, spec);
        if (type.IsPointer)
          return PointerContainer.MakeType (module, spec);

        throw new NotImplementedException ("Unknown element type " + type.ToString ());
      }

      TypeSpec compiled_type;
      if (compiled_types.TryGetValue (type, out compiled_type)) {
        if (compiled_type.BuiltinType == BuiltinTypeSpec.Type.Object && dtype.IsDynamicObject ())
          return module.Compiler.BuiltinTypes.Dynamic;

        return compiled_type;
      }

      return CreateType (type, dtype, true);
    }

    static bool IsMissingType (MetaType type)
    {
#if STATIC
      return type.__IsMissing;
#else
      return false;
#endif
    }

    //
    // Decimal constants cannot be encoded in the constant blob, and thus are marked
    // as IsInitOnly ('readonly' in C# parlance).  We get its value from the 
    // DecimalConstantAttribute metadata.
    //
    Constant ReadDecimalConstant (IList<CustomAttributeData> attrs)
    {
      if (attrs.Count == 0)
        return null;

      foreach (var ca in attrs) {
        var dt = ca.Constructor.DeclaringType;
        if (dt.Name != "DecimalConstantAttribute" || dt.Namespace != CompilerServicesNamespace)
          continue;

        var value = new decimal (
          (int) (uint) ca.ConstructorArguments[4].Value,
          (int) (uint) ca.ConstructorArguments[3].Value,
          (int) (uint) ca.ConstructorArguments[2].Value,
          (byte) ca.ConstructorArguments[1].Value != 0,
          (byte) ca.ConstructorArguments[0].Value);

        return new DecimalConstant (module.Compiler.BuiltinTypes, value, Location.Null);
      }

      return null;
    }

    static Modifiers ReadMethodModifiers (MethodBase mb, TypeSpec declaringType)
    {
      Modifiers mod;
      var ma = mb.Attributes;
      switch (ma & MethodAttributes.MemberAccessMask) {
      case MethodAttributes.Public:
        mod = Modifiers.PUBLIC;
        break;
      case MethodAttributes.Assembly:
        mod = Modifiers.INTERNAL;
        break;
      case MethodAttributes.Family:
        mod = Modifiers.PROTECTED;
        break;
      case MethodAttributes.FamORAssem:
        mod = Modifiers.PROTECTED | Modifiers.INTERNAL;
        break;
      default:
        mod = Modifiers.PRIVATE;
        break;
      }

      if ((ma & MethodAttributes.Static) != 0) {
        mod |= Modifiers.STATIC;
        return mod;
      }
      if ((ma & MethodAttributes.Abstract) != 0 && declaringType.IsClass) {
        mod |= Modifiers.ABSTRACT;
        return mod;
      }

      // It can be sealed and override
      if ((ma & MethodAttributes.Final) != 0)
        mod |= Modifiers.SEALED;

      if ((ma & MethodAttributes.Virtual) != 0) {
        // Not every member can be detected based on MethodAttribute, we
        // set virtual or non-virtual only when we are certain. Further checks
        // to really find out what `virtual' means for this member are done
        // later
        if ((ma & MethodAttributes.NewSlot) != 0) {
          if ((mod & Modifiers.SEALED) != 0) {
            mod &= ~Modifiers.SEALED;
          } else {
            mod |= Modifiers.VIRTUAL;
          }
        } else {
          mod |= Modifiers.OVERRIDE;
        }
      }

      return mod;
    }
  }

  abstract class ImportedDefinition : IMemberDefinition
  {
    protected class AttributesBag
    {
      public static readonly AttributesBag Default = new AttributesBag ();

      public AttributeUsageAttribute AttributeUsage;
      public ObsoleteAttribute Obsolete;
      public string[] Conditionals;
      public string DefaultIndexerName;
      public bool? CLSAttributeValue;
      public TypeSpec CoClass;

      static bool HasMissingType (ConstructorInfo ctor)
      {
#if STATIC
        //
        // Mimic odd csc behaviour where missing type on predefined
        // attributes means the attribute is silently ignored. This can
        // happen with PCL facades
        //
        foreach (var p in ctor.GetParameters ()) {
          if (p.ParameterType.__ContainsMissingType)
            return true;
        }
#endif

        return false;
      }
      
      public static AttributesBag Read (MemberInfo mi, MetadataImporter importer)
      {
        AttributesBag bag = null;
        List<string> conditionals = null;

        // It should not throw any loading exception
        IList<CustomAttributeData> attrs = CustomAttributeData.GetCustomAttributes (mi);

        foreach (var a in attrs) {
          var dt = a.Constructor.DeclaringType;
          string name = dt.Name;
          if (name == "ObsoleteAttribute") {
            if (dt.Namespace != "System")
              continue;

            if (bag == null)
              bag = new AttributesBag ();

            var args = a.ConstructorArguments;

            if (args.Count == 1) {
              bag.Obsolete = new ObsoleteAttribute ((string) args[0].Value);
            } else if (args.Count == 2) {
              bag.Obsolete = new ObsoleteAttribute ((string) args[0].Value, (bool) args[1].Value);
            } else {
              bag.Obsolete = new ObsoleteAttribute ();
            }

            continue;
          }

          if (name == "ConditionalAttribute") {
            if (dt.Namespace != "System.Diagnostics")
              continue;

            if (bag == null)
              bag = new AttributesBag ();

            if (conditionals == null)
              conditionals = new List<string> (2);

            conditionals.Add ((string) a.ConstructorArguments[0].Value);
            continue;
          }

          if (name == "CLSCompliantAttribute") {
            if (dt.Namespace != "System")
              continue;

            if (bag == null)
              bag = new AttributesBag ();

            bag.CLSAttributeValue = (bool) a.ConstructorArguments[0].Value;
            continue;
          }

          // Type only attributes
          if (mi.MemberType == MemberTypes.TypeInfo || mi.MemberType == MemberTypes.NestedType) {
            if (name == "DefaultMemberAttribute") {
              if (dt.Namespace != "System.Reflection")
                continue;

              if (bag == null)
                bag = new AttributesBag ();

              bag.DefaultIndexerName = (string) a.ConstructorArguments[0].Value;
              continue;
            }

            if (name == "AttributeUsageAttribute") {
              if (dt.Namespace != "System")
                continue;

              if (HasMissingType (a.Constructor))
                continue;

              if (bag == null)
                bag = new AttributesBag ();

              bag.AttributeUsage = new AttributeUsageAttribute ((AttributeTargets) a.ConstructorArguments[0].Value);
              foreach (var named in a.NamedArguments) {
                if (named.MemberInfo.Name == "AllowMultiple")
                  bag.AttributeUsage.AllowMultiple = (bool) named.TypedValue.Value;
                else if (named.MemberInfo.Name == "Inherited")
                  bag.AttributeUsage.Inherited = (bool) named.TypedValue.Value;
              }
              continue;
            }

            // Interface only attribute
            if (name == "CoClassAttribute") {
              if (dt.Namespace != "System.Runtime.InteropServices")
                continue;

              if (HasMissingType (a.Constructor))
                continue;

              if (bag == null)
                bag = new AttributesBag ();

              bag.CoClass = importer.ImportType ((MetaType) a.ConstructorArguments[0].Value);
              continue;
            }
          }
        }

        if (bag == null)
          return Default;

        if (conditionals != null)
          bag.Conditionals = conditionals.ToArray ();
        
        return bag;
      }
    }

    protected readonly MemberInfo provider;
    protected AttributesBag cattrs;
    protected readonly MetadataImporter importer;

    protected ImportedDefinition (MemberInfo provider, MetadataImporter importer)
    {
      this.provider = provider;
      this.importer = importer;
    }

    #region Properties

    public bool IsImported {
      get {
        return true;
      }
    }

    public virtual string Name {
      get {
        return provider.Name;
      }
    }

    #endregion

    public string[] ConditionalConditions ()
    {
      if (cattrs == null)
        ReadAttributes ();

      return cattrs.Conditionals;
    }

    public ObsoleteAttribute GetAttributeObsolete ()
    {
      if (cattrs == null)
        ReadAttributes ();

      return cattrs.Obsolete;
    }

    public bool? CLSAttributeValue {
      get {
        if (cattrs == null)
          ReadAttributes ();

        return cattrs.CLSAttributeValue;
      }
    }

    protected void ReadAttributes ()
    {
      cattrs = AttributesBag.Read (provider, importer);
    }

    public void SetIsAssigned ()
    {
      // Unused for imported members
    }

    public void SetIsUsed ()
    {
      // Unused for imported members
    }
  }

  public class ImportedModuleDefinition
  {
    readonly Module module;
    bool cls_compliant;
    
    public ImportedModuleDefinition (Module module)
    {
      this.module = module;
    }

    #region Properties

    public bool IsCLSCompliant {
      get {
        return cls_compliant;
      }
    }

    public string Name {
      get {
        return module.Name;
      }
    }

    #endregion

    public void ReadAttributes ()
    {
      IList<CustomAttributeData> attrs = CustomAttributeData.GetCustomAttributes (module);

      foreach (var a in attrs) {
        var dt = a.Constructor.DeclaringType;
        if (dt.Name == "CLSCompliantAttribute") {
          if (dt.Namespace != "System")
            continue;

          cls_compliant = (bool) a.ConstructorArguments[0].Value;
          continue;
        }
      }
    }

    //
    // Reads assembly attributes which where attached to a special type because
    // module does have assembly manifest
    //
    public List<Attribute> ReadAssemblyAttributes ()
    {
      var t = module.GetType (AssemblyAttributesPlaceholder.GetGeneratedName (Name));
      if (t == null)
        return null;

      var field = t.GetField (AssemblyAttributesPlaceholder.AssemblyFieldName, BindingFlags.NonPublic | BindingFlags.Static);
      if (field == null)
        return null;

      // TODO: implement, the idea is to fabricate specil Attribute class and
      // add it to OptAttributes before resolving the source code attributes
      // Need to build module location as well for correct error reporting

      //var assembly_attributes = CustomAttributeData.GetCustomAttributes (field);
      //var attrs = new List<Attribute> (assembly_attributes.Count);
      //foreach (var a in assembly_attributes)
      //{
      //    var type = metaImporter.ImportType (a.Constructor.DeclaringType);
      //    var ctor = metaImporter.CreateMethod (a.Constructor, type);

      //    foreach (var carg in a.ConstructorArguments) {
      //        carg.Value
      //    }

      //    attrs.Add (new Attribute ("assembly", ctor, null, Location.Null, true));
      //}

      return null;
    }
  }

  public class ImportedAssemblyDefinition : IAssemblyDefinition
  {
    readonly Assembly assembly;
    readonly AssemblyName aname;
    bool cls_compliant;

    List<AssemblyName> internals_visible_to;
    Dictionary<IAssemblyDefinition, AssemblyName> internals_visible_to_cache;

    public ImportedAssemblyDefinition (Assembly assembly)
    {
      this.assembly = assembly;
      this.aname = assembly.GetName ();
    }

    #region Properties

    public Assembly Assembly {
      get {
        return assembly;
      }
    }

    public string FullName {
      get {
        return aname.FullName;
      }
    }

    public bool HasStrongName {
      get {
        return aname.GetPublicKey ().Length != 0;
      }
    }

    public bool IsMissing {
      get {
#if STATIC
        return assembly.__IsMissing;
#else
        return false;
#endif
      }
    }

    public bool IsCLSCompliant {
      get {
        return cls_compliant;
      }
    }

    public string Location {
      get {
        return assembly.Location;
      }
    }

    public string Name {
      get {
        return aname.Name;
      }
    }

    #endregion

    public byte[] GetPublicKeyToken ()
    {
      return aname.GetPublicKeyToken ();
    }

    public AssemblyName GetAssemblyVisibleToName (IAssemblyDefinition assembly)
    {
      return internals_visible_to_cache [assembly];
    }

    public bool IsFriendAssemblyTo (IAssemblyDefinition assembly)
    {
      if (internals_visible_to == null)
        return false;

      AssemblyName is_visible = null;
      if (internals_visible_to_cache == null) {
        internals_visible_to_cache = new Dictionary<IAssemblyDefinition, AssemblyName> ();
      } else {
        if (internals_visible_to_cache.TryGetValue (assembly, out is_visible))
          return is_visible != null;
      }

      var token = assembly.GetPublicKeyToken ();
      if (token != null && token.Length == 0)
        token = null;

      foreach (var internals in internals_visible_to) {
        if (internals.Name != assembly.Name)
          continue;

        if (token == null && assembly is AssemblyDefinition) {
          is_visible = internals;
          break;
        }

        if (!ArrayComparer.IsEqual (token, internals.GetPublicKeyToken ()))
          continue;

        is_visible = internals;
        break;
      }

      internals_visible_to_cache.Add (assembly, is_visible);
      return is_visible != null;
    }

    public void ReadAttributes ()
    {
#if STATIC
      if (assembly.__IsMissing)
        return;
#endif

      IList<CustomAttributeData> attrs = CustomAttributeData.GetCustomAttributes (assembly);

      foreach (var a in attrs) {
        var dt = a.Constructor.DeclaringType;
        var name = dt.Name;
        if (name == "CLSCompliantAttribute") {
          if (dt.Namespace == "System") {
            cls_compliant = (bool) a.ConstructorArguments[0].Value;
          }
          continue;
        }

        if (name == "InternalsVisibleToAttribute") {
          if (dt.Namespace != MetadataImporter.CompilerServicesNamespace)
            continue;

          string s = a.ConstructorArguments[0].Value as string;
          if (s == null)
            continue;

          var an = new AssemblyName (s);
          if (internals_visible_to == null)
            internals_visible_to = new List<AssemblyName> ();

          internals_visible_to.Add (an);
          continue;
        }
      }
    }

    public override string ToString ()
    {
      return FullName;
    }
  }

  class ImportedMemberDefinition : ImportedDefinition
  {
    readonly TypeSpec type;

    public ImportedMemberDefinition (MemberInfo member, TypeSpec type, MetadataImporter importer)
      : base (member, importer)
    {
      this.type = type;
    }

    #region Properties

    public TypeSpec MemberType {
      get {
        return type;
      }
    }

    #endregion
  }

  class ImportedParameterMemberDefinition : ImportedMemberDefinition, IParametersMember
  {
    readonly AParametersCollection parameters;

    protected ImportedParameterMemberDefinition (MethodBase provider, TypeSpec type, AParametersCollection parameters, MetadataImporter importer)
      : base (provider, type, importer)
    {
      this.parameters = parameters;
    }

    public ImportedParameterMemberDefinition (PropertyInfo provider, TypeSpec type, AParametersCollection parameters, MetadataImporter importer)
      : base (provider, type, importer)
    {
      this.parameters = parameters;
    }

    #region Properties

    public AParametersCollection Parameters {
      get {
        return parameters;
      }
    }

    #endregion
  }

  class ImportedMethodDefinition : ImportedParameterMemberDefinition, IMethodDefinition
  {
    public ImportedMethodDefinition (MethodBase provider, TypeSpec type, AParametersCollection parameters, MetadataImporter importer)
      : base (provider, type, parameters, importer)
    {
    }

    MethodBase IMethodDefinition.Metadata {
      get {
        return (MethodBase) provider;
      }
    }
  }

  class ImportedGenericMethodDefinition : ImportedMethodDefinition, IGenericMethodDefinition
  {
    readonly TypeParameterSpec[] tparams;

    public ImportedGenericMethodDefinition (MethodInfo provider, TypeSpec type, AParametersCollection parameters, TypeParameterSpec[] tparams, MetadataImporter importer)
      : base (provider, type, parameters, importer)
    {
      this.tparams = tparams;
    }

    #region Properties

    public TypeParameterSpec[] TypeParameters {
      get {
        return tparams;
      }
    }

    public int TypeParametersCount {
      get {
        return tparams.Length;
      }
    }

    #endregion
  }

  class ImportedTypeDefinition : ImportedDefinition, ITypeDefinition
  {
    TypeParameterSpec[] tparams;
    string name;

    public ImportedTypeDefinition (MetaType type, MetadataImporter importer)
      : base (type, importer)
    {
    }

    #region Properties

    public IAssemblyDefinition DeclaringAssembly {
      get {
        return importer.GetAssemblyDefinition (provider.Module.Assembly);
      }
    }

    bool ITypeDefinition.IsComImport {
      get {
        return ((MetaType) provider).IsImport;
      }
    }


    bool ITypeDefinition.IsPartial {
      get {
        return false;
      }
    }

    bool ITypeDefinition.IsTypeForwarder {
      get {
#if STATIC
        return ((MetaType) provider).__IsTypeForwarder;
#else
        return false;
#endif
      }
    }

    bool ITypeDefinition.IsCyclicTypeForwarder {
      get {
#if STATIC
        return ((MetaType) provider).__IsCyclicTypeForwarder;
#else
        return false;
#endif
      }
    }

    public override string Name {
      get {
        if (name == null) {
          name = base.Name;
          if (tparams != null) {
            int arity_start = name.IndexOf ('`');
            if (arity_start > 0)
              name = name.Substring (0, arity_start);
          }
        }

        return name;
      }
    }

    public string Namespace {
      get {
        return ((MetaType) provider).Namespace;
      }
    }

    public int TypeParametersCount {
      get {
        return tparams == null ? 0 : tparams.Length;
      }
    }

    public TypeParameterSpec[] TypeParameters {
      get {
        return tparams;
      }
      set {
        tparams = value;
      }
    }

    #endregion

    public void DefineInterfaces (TypeSpec spec)
    {
      var type = (MetaType) provider;
      MetaType[] ifaces;
#if STATIC
      ifaces = type.__GetDeclaredInterfaces ();
      if (ifaces.Length != 0) {
        foreach (var iface in ifaces) {
          var it = importer.CreateType (iface);
          if (it == null)
            continue;

          spec.AddInterfaceDefined (it);

          // Unfortunately not all languages expand inherited interfaces
          var bifaces = it.Interfaces;
          if (bifaces != null) {
            foreach (var biface in bifaces) {
              spec.AddInterfaceDefined (biface);
            }
          }
        }
      }
      
      //
      // It's impossible to get declared interfaces only using System.Reflection
      // hence we need to mimic the behavior with ikvm-reflection too to keep
      // our type look-up logic same
      //
      if (spec.BaseType != null) {
        var bifaces = spec.BaseType.Interfaces;
        if (bifaces != null) {
          //
          // Before adding base class interfaces close defined interfaces
          // on type parameter
          //
          var tp = spec as TypeParameterSpec;
          if (tp != null && tp.InterfacesDefined == null) {
            tp.InterfacesDefined = TypeSpec.EmptyTypes;
          }

          foreach (var iface in bifaces)
            spec.AddInterfaceDefined (iface);
        }
      }
#else
      ifaces = type.GetInterfaces ();

      if (ifaces.Length > 0) {
        foreach (var iface in ifaces) {
          spec.AddInterface (importer.CreateType (iface));
        }
      }
#endif

    }

    public static void Error_MissingDependency (IMemberContext ctx, List<MissingTypeSpecReference> missing, Location loc)
    {
      // 
      // Report details about missing type and most likely cause of the problem.
      // csc reports 1683, 1684 as warnings but we report them only when used
      // or referenced from the user core in which case compilation error has to
      // be reported because compiler cannot continue anyway
      //

      var report = ctx.Module.Compiler.Report;

      for (int i = 0; i < missing.Count; ++i) {
        var t = missing [i].Type;

        //
        // Report missing types only once
        //
        if (report.Printer.MissingTypeReported (t.MemberDefinition))
          continue;

        string name = t.GetSignatureForError ();

        var caller = missing[i].Caller;
        if (caller.Kind != MemberKind.MissingType)
          report.SymbolRelatedToPreviousError (caller);

        var definition = t.MemberDefinition;
        if (definition.DeclaringAssembly == ctx.Module.DeclaringAssembly) {
          report.Error (1683, loc,
            "Reference to type `{0}' claims it is defined in this assembly, but it is not defined in source or any added modules",
            name);
        } else if (definition.DeclaringAssembly.IsMissing) {
          if (definition.IsTypeForwarder) {
            report.Error (1070, loc,
              "The type `{0}' has been forwarded to an assembly that is not referenced. Consider adding a reference to assembly `{1}'",
              name, definition.DeclaringAssembly.FullName);
          } else {
            report.Error (12, loc,
              "The type `{0}' is defined in an assembly that is not referenced. Consider adding a reference to assembly `{1}'",
              name, definition.DeclaringAssembly.FullName);
          }
        } else if (definition.IsTypeForwarder) {
          report.Error (731, loc, "The type forwarder for type `{0}' in assembly `{1}' has circular dependency",
            name, definition.DeclaringAssembly.FullName);
        } else {
          report.Error (1684, loc,
            "Reference to type `{0}' claims it is defined assembly `{1}', but it could not be found",
            name, t.MemberDefinition.DeclaringAssembly.FullName);
        }
      }
    }

    public TypeSpec GetAttributeCoClass ()
    {
      if (cattrs == null)
        ReadAttributes ();

      return cattrs.CoClass;
    }

    public string GetAttributeDefaultMember ()
    {
      if (cattrs == null)
        ReadAttributes ();

      return cattrs.DefaultIndexerName;
    }

    public AttributeUsageAttribute GetAttributeUsage (PredefinedAttribute pa)
    {
      if (cattrs == null)
        ReadAttributes ();

      return cattrs.AttributeUsage;
    }

    bool ITypeDefinition.IsInternalAsPublic (IAssemblyDefinition assembly)
    {
      var a = importer.GetAssemblyDefinition (provider.Module.Assembly);
      return a == assembly || a.IsFriendAssemblyTo (assembly);
    }

    public void LoadMembers (TypeSpec declaringType, bool onlyTypes, ref MemberCache cache)
    {
      //
      // Not interested in members of nested private types unless the importer needs them
      //
      if (declaringType.IsPrivate && importer.IgnorePrivateMembers) {
        cache = MemberCache.Empty;
        return;
      }

      var loading_type = (MetaType) provider;
      const BindingFlags all_members = BindingFlags.DeclaredOnly |
        BindingFlags.Static | BindingFlags.Instance |
        BindingFlags.Public | BindingFlags.NonPublic;

      const MethodAttributes explicit_impl = MethodAttributes.NewSlot |
          MethodAttributes.Virtual | MethodAttributes.HideBySig |
          MethodAttributes.Final;

      Dictionary<MethodBase, MethodSpec> possible_accessors = null;
      List<EventSpec> imported_events = null;
      EventSpec event_spec;
      MemberSpec imported;
      MethodInfo m;
      MemberInfo[] all;
      try {
        all = loading_type.GetMembers (all_members);
      } catch (Exception e) {
        throw new InternalErrorException (e, "Could not import type `{0}' from `{1}'",
          declaringType.GetSignatureForError (), declaringType.MemberDefinition.DeclaringAssembly.FullName);
      }

      if (cache == null) {
        cache = new MemberCache (all.Length);

        //
        // Do the types first as they can be referenced by the members before
        // they are found or inflated
        //
        foreach (var member in all) {
          if (member.MemberType != MemberTypes.NestedType)
            continue;

          var t = (MetaType) member;

          // Ignore compiler generated types, mostly lambda containers
          if ((t.Attributes & TypeAttributes.VisibilityMask) == TypeAttributes.NestedPrivate && importer.IgnorePrivateMembers)
            continue;

          try {
            imported = importer.CreateNestedType (t, declaringType);
          } catch (Exception e) {
            throw new InternalErrorException (e, "Could not import nested type `{0}' from `{1}'",
              t.FullName, declaringType.MemberDefinition.DeclaringAssembly.FullName);
          }

          cache.AddMemberImported (imported);
        }

        foreach (var member in all) {
          if (member.MemberType != MemberTypes.NestedType)
            continue;

          var t = (MetaType) member;

          if ((t.Attributes & TypeAttributes.VisibilityMask) == TypeAttributes.NestedPrivate && importer.IgnorePrivateMembers)
            continue;

          importer.ImportTypeBase (t);
        }
      }

      //
      // Load base interfaces first to minic behaviour of compiled members
      //
      if (declaringType.IsInterface && declaringType.Interfaces != null) {
        foreach (var iface in declaringType.Interfaces) {
          cache.AddInterface (iface);
        }
      }

      if (!onlyTypes) {
        //
        // The logic here requires methods to be returned first which seems to work for both Mono and .NET
        //
        foreach (var member in all) {
          switch (member.MemberType) {
          case MemberTypes.Constructor:
            if (declaringType.IsInterface)
              continue;

            goto case MemberTypes.Method;
          case MemberTypes.Method:
            MethodBase mb = (MethodBase) member;
            var attrs = mb.Attributes;

            if ((attrs & MethodAttributes.MemberAccessMask) == MethodAttributes.Private) {
              if (importer.IgnorePrivateMembers)
                continue;

              // Ignore explicitly implemented members
              if ((attrs & explicit_impl) == explicit_impl)
                continue;

              // Ignore compiler generated methods
              if (MetadataImporter.HasAttribute (CustomAttributeData.GetCustomAttributes (mb), "CompilerGeneratedAttribute", MetadataImporter.CompilerServicesNamespace))
                continue;
            }

            imported = importer.CreateMethod (mb, declaringType);
            if (imported.Kind == MemberKind.Method && !imported.IsGeneric) {
              if (possible_accessors == null)
                possible_accessors = new Dictionary<MethodBase, MethodSpec> (ReferenceEquality<MethodBase>.Default);

              // There are no metadata rules for accessors, we have to consider any method as possible candidate
              possible_accessors.Add (mb, (MethodSpec) imported);
            }

            break;
          case MemberTypes.Property:
            if (possible_accessors == null)
              continue;

            var p = (PropertyInfo) member;
            //
            // Links possible accessors with property
            //
            MethodSpec get, set;
            m = p.GetGetMethod (true);
            if (m == null || !possible_accessors.TryGetValue (m, out get))
              get = null;

            m = p.GetSetMethod (true);
            if (m == null || !possible_accessors.TryGetValue (m, out set))
              set = null;

            // No accessors registered (e.g. explicit implementation)
            if (get == null && set == null)
              continue;

            try {
              imported = importer.CreateProperty (p, declaringType, get, set);
            } catch (Exception ex) {
              throw new InternalErrorException (ex, "Could not import property `{0}' inside `{1}'",
                p.Name, declaringType.GetSignatureForError ());
            }

            if (imported == null)
              continue;

            break;
          case MemberTypes.Event:
            if (possible_accessors == null)
              continue;

            var e = (EventInfo) member;
            //
            // Links accessors with event
            //
            MethodSpec add, remove;
            m = e.GetAddMethod (true);
            if (m == null || !possible_accessors.TryGetValue (m, out add))
              add = null;

            m = e.GetRemoveMethod (true);
            if (m == null || !possible_accessors.TryGetValue (m, out remove))
              remove = null;

            // Both accessors are required
            if (add == null || remove == null)
              continue;

            event_spec = importer.CreateEvent (e, declaringType, add, remove);
            if (!importer.IgnorePrivateMembers) {
              if (imported_events == null)
                imported_events = new List<EventSpec> ();

              imported_events.Add (event_spec);
            }

            imported = event_spec;
            break;
          case MemberTypes.Field:
            var fi = (FieldInfo) member;

            imported = importer.CreateField (fi, declaringType);
            if (imported == null)
              continue;

            //
            // For dynamic binder event has to be fully restored to allow operations
            // within the type container to work correctly
            //
            if (imported_events != null) {
              // The backing event field should be private but it may not
              int i;
              for (i = 0; i < imported_events.Count; ++i) {
                var ev = imported_events[i];
                if (ev.Name == fi.Name) {
                  ev.BackingField = (FieldSpec) imported;
                  imported_events.RemoveAt (i);
                  i = -1;
                  break;
                }
              }

              if (i < 0)
                continue;
            }

            break;
          case MemberTypes.NestedType:
            // Already in the cache from the first pass
            continue;
          default:
            throw new NotImplementedException (member.ToString ());
          }

          if (imported.IsStatic && declaringType.IsInterface)
            continue;

          cache.AddMemberImported (imported);
        }
      }
    }
  }

  class ImportedTypeParameterDefinition : ImportedDefinition, ITypeDefinition
  {
    public ImportedTypeParameterDefinition (MetaType type, MetadataImporter importer)
      : base (type, importer)
    {
    }

    #region Properties

    public IAssemblyDefinition DeclaringAssembly {
      get {
        throw new NotImplementedException ();
      }
    }

    bool ITypeDefinition.IsComImport {
      get {
        return false;
      }
    }

    bool ITypeDefinition.IsPartial {
      get {
        return false;
      }
    }

    bool ITypeDefinition.IsTypeForwarder {
      get {
        return false;
      }
    }

    bool ITypeDefinition.IsCyclicTypeForwarder {
      get {
        return false;
      }
    }

    public string Namespace {
      get {
        return null;
      }
    }

    public int TypeParametersCount {
      get {
        return 0;
      }
    }

    public TypeParameterSpec[] TypeParameters {
      get {
        return null;
      }
    }

    #endregion

    public TypeSpec GetAttributeCoClass ()
    {
      return null;
    }

    public string GetAttributeDefaultMember ()
    {
      throw new NotSupportedException ();
    }

    public AttributeUsageAttribute GetAttributeUsage (PredefinedAttribute pa)
    {
      throw new NotSupportedException ();
    }

    bool ITypeDefinition.IsInternalAsPublic (IAssemblyDefinition assembly)
    {
      throw new NotImplementedException ();
    }

    public void LoadMembers (TypeSpec declaringType, bool onlyTypes, ref MemberCache cache)
    {
      throw new NotImplementedException ();
    }
  }
}