ClassMirror.mixin

runtime/vm/class_finalizer.cc

 // Copyright (c) 2013, 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.
 
 #include "vm/class_finalizer.h"
 
 #include "vm/flags.h"
 #include "vm/heap.h"
 #include "vm/isolate.h"
 #include "vm/longjump.h"
@@ skipping 1279 matching lines @@
     }
   }
 }
 
 
 // Copy the type parameters of the super and mixin classes to the
 // mixin application class. Change type arguments of super type and of
 // interfaces to refer to the respective type parameters of the mixin
 // application class.
 void ClassFinalizer::CloneTypeParameters(const Class& mixapp_class) {
-  ASSERT(mixapp_class.NumTypeParameters() == 0);
+  if (mixapp_class.NumTypeParameters() != 0) {
+    // Mixin applications created by typedef can introduce their own type
+    // paramaters.
+    return;

[regis, 2013/08/20 18:56:37]

I think that returning here is actually correct if the mixapp_class is an alias,
not just if it has no type parameters. Take the following example:
typedef MA = List<int> with Map<int, int>;

There is no need to parameterize MA.
Assumming List<E> and Map<K, V>, we would get MA<E, K, V>, but this is
unnecessary, since mixin sets all type parameters to 'int'.

On the other hand:
typedef MA<K> = List<int> with Map<K, int>;
MA already has one type parameter and nothing needs to change. You can return
too.

In the non-alias case:
class MA<K> extends List<int> with Map<K, int> {}
We create a S&M<E`, K, V>, which is overkill, but correct.
We could optimize this at a later stage an create a simpler S&M<K>.

Bottom line:
You need to detect if the mixapp_class is an alias. One way is to check that its
name does not contain '&'. There may be a more elegant way.

+  }
 
   const AbstractType& super_type =
       AbstractType::Handle(mixapp_class.super_type());
   ASSERT(super_type.IsResolved());
   const Class& super_class = Class::Handle(super_type.type_class());
   const Type& mixin_type = Type::Handle(mixapp_class.mixin());
   const Class& mixin_class = Class::Handle(mixin_type.type_class());
   const int num_super_parameters = super_class.NumTypeParameters();
   const int num_mixin_parameters = mixin_class.NumTypeParameters();
   if ((num_super_parameters + num_mixin_parameters) == 0) {
@@ skipping 997 matching lines @@
   expected_name ^= String::New("_offset");
   ASSERT(String::EqualsIgnoringPrivateKey(name, expected_name));
   field ^= fields_array.At(2);
   ASSERT(field.Offset() == TypedDataView::length_offset());
   name ^= field.name();
   ASSERT(name.Equals("length"));
 #endif
 }
 
 }  // namespace dart