Use the runtime for generic subsitution of variable types, return types, parameter types.

runtime/lib/mirrors_impl.dart

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 // VM-specific implementation of the dart:mirrors library.
 
 import "dart:collection";
 
 final emptyList = new UnmodifiableListView([]);
 final emptyMap = new _UnmodifiableMapView({});
@@ skipping 1190 matching lines @@
 
   bool get isPrivate => _n(simpleName).startsWith('_') ||
                         _n(constructorName).startsWith('_');
 
   bool get isTopLevel =>  owner is LibraryMirror;
 
   SourceLocation get location {
     throw new UnimplementedError('MethodMirror.location is not implemented');
   }
 
+  Type get _instantiator => owner is ClassMirror ? owner._reflectedType : null;
+
   TypeMirror _returnType = null;
   TypeMirror get returnType {
     if (_returnType == null) {
       if (isConstructor) {
         _returnType = owner;

[regis, 2013/11/06 19:06:07]

Why don't you instantiate in this case?

       } else {
-        _returnType = reflectType(_MethodMirror_return_type(_reflectee));
+        _returnType = reflectType(
+            _MethodMirror_return_type(_reflectee, _instantiator));
       }
-      _returnType = _returnType._instantiateInContextOf(owner);
     }
     return _returnType;
   }
 
   List<ParameterMirror> _parameters = null;
   List<ParameterMirror> get parameters {
     if (_parameters == null) {
       _parameters = _MethodMirror_parameters(_reflectee);
       _parameters = new UnmodifiableListView(_parameters);
     }
@@ skipping 39 matching lines @@
     } else {
       _simpleName = _s(ownerName + "." + cn);
     }
   }
 
   String toString() => "MethodMirror on '${MirrorSystem.getName(simpleName)}'";
 
   static dynamic _MethodMirror_owner(reflectee)
       native "MethodMirror_owner";
 
-  static dynamic _MethodMirror_return_type(reflectee)
+  static dynamic _MethodMirror_return_type(reflectee, instantiator)
       native "MethodMirror_return_type";
 
   List<ParameterMirror> _MethodMirror_parameters(reflectee)
       native "MethodMirror_parameters";
 
   static String _MethodMirror_source(reflectee)
       native "MethodMirror_source";
 }
 
 class _LocalVariableMirrorImpl extends _LocalDeclarationMirrorImpl
@@ skipping 11 matching lines @@
   final bool isFinal;
 
   bool get isPrivate => _n(simpleName).startsWith('_');
 
   bool get isTopLevel => owner is LibraryMirror;
 
   SourceLocation get location {
     throw new UnimplementedError('VariableMirror.location is not implemented');
   }
 
+  Type get _instantiator => owner is ClassMirror ? owner._reflectedType : null;
+
   TypeMirror _type;
   TypeMirror get type {
     if (_type == null) {
-       _type = reflectType(_VariableMirror_type(_reflectee));
-       _type = _type._instantiateInContextOf(owner);
+       _type = reflectType(_VariableMirror_type(_reflectee, _instantiator));
     }
     return _type;
   }
 
   String toString() => "VariableMirror on '${MirrorSystem.getName(simpleName)}'";
 
-  static _VariableMirror_type(reflectee)
+  static _VariableMirror_type(reflectee, instantiator)
       native "VariableMirror_type";
 }
 
 class _LocalParameterMirrorImpl extends _LocalVariableMirrorImpl
     implements ParameterMirror {
   _LocalParameterMirrorImpl(reflectee,
                             String simpleName,
                             DeclarationMirror owner,
                             this._position,
                             this.isOptional,
@@ skipping 21 matching lines @@
     }
     if (_defaultValue == null) {
       _defaultValue = reflect(_defaultValueReflectee);
     }
     return _defaultValue;
   }
 
   bool get hasDefaultValue => _defaultValueReflectee != null;
 
   List<InstanceMirror> get metadata {
-    if ( _unmirroredMetadata == null) return emptyList;
+    if (_unmirroredMetadata == null) return emptyList;
     return new UnmodifiableListView(_unmirroredMetadata.map(reflect));
   }
 
+  Type get _instantiator {
+    return owner.owner is ClassMirror ? owner.owner._reflectedType : null;
+  }
+
   TypeMirror _type = null;
   TypeMirror get type {
     if (_type == null) {
-      _type = reflectType(_ParameterMirror_type(_reflectee, _position));
-      _type = _type._instantiateInContextOf(owner);
+      _type = reflectType(
+          _ParameterMirror_type(_reflectee, _position, _instantiator));
     }
     return _type;
   }
 
   String toString() => "ParameterMirror on '${_n(simpleName)}'";
 
-  static Type _ParameterMirror_type(_reflectee, _position)
+  static Type _ParameterMirror_type(_reflectee, _position, instantiator)
       native "ParameterMirror_type";
 }
 
 class _SpecialTypeMirrorImpl extends _LocalMirrorImpl
     implements TypeMirror, DeclarationMirror {
   _SpecialTypeMirrorImpl(String name) : simpleName = _s(name);
 
   final bool isPrivate = false;
   final DeclarationMirror owner = null;
   final Symbol simpleName;
@@ skipping 78 matching lines @@
     if (typeMirror == null) {
       typeMirror = makeLocalTypeMirror(key);
       _instanitationCache[key] = typeMirror;
       if (typeMirror is ClassMirror && !typeMirror._isGeneric) {
         _declarationCache[key] = typeMirror;
       }
     }
     return typeMirror;
   }
 }