cps-ir: Support foreign code.

pkg/compiler/lib/src/types/type_mask.dart

 // 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.
 
 part of types;
 
 /**
  * A type mask represents a set of contained classes, but the
  * operations on it are not guaranteed to be precise and they may
  * yield conservative answers that contain too many classes.
  */
 abstract class TypeMask {
   factory TypeMask(ClassElement base,
                    int kind,
                    bool isNullable,
                    ClassWorld classWorld) {
     return new FlatTypeMask.normalized(
         base, (kind << 1) | (isNullable ? 1 : 0), classWorld);
   }
 
   const factory TypeMask.empty() = FlatTypeMask.empty;
 
   factory TypeMask.exact(ClassElement base, ClassWorld classWorld) {
     assert(invariant(base, classWorld.isInstantiated(base),
-        message: "Cannot create extact type mask for "
-                 "uninstantiated class $base"));
+        message: "Cannot create extact type mask for uninstantiated class "
+          "${base.name}"));
     return new FlatTypeMask.exact(base);
   }
 
   factory TypeMask.exactOrEmpty(ClassElement base, ClassWorld classWorld) {
     if (classWorld.isInstantiated(base)) return new FlatTypeMask.exact(base);
     return const TypeMask.empty();
   }
 
   factory TypeMask.subclass(ClassElement base, ClassWorld classWorld) {
     if (classWorld.hasAnySubclass(base)) {
@@ skipping 224 matching lines @@
    */
   bool canHit(Element element, Selector selector, ClassWorld classWorld);
 
   /**
    * Returns the [element] that is known to always be hit at runtime
    * on this mask. Returns null if there is none.
    */
   // TODO(johnniwinther): Move this method to [World].
   Element locateSingleElement(Selector selector, Compiler compiler);
 }