Split World usage into open, inference, and closed world.

pkg/compiler/lib/src/types/union_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 masks;
 
 class UnionTypeMask implements TypeMask {
   final Iterable<FlatTypeMask> disjointMasks;
 
   static const int MAX_UNION_LENGTH = 4;
@@ skipping 200 matching lines @@
    * - [other] may not be a [UnionTypeMask] itself
    * - the cheap test matching against individual members of [disjointMasks]
    *   must have failed.
    */
   bool slowContainsCheck(TypeMask other, ClassWorld classWorld) {
     // Unions should never make it here.
     assert(!other.isUnion);
     // Ensure the cheap test fails.
     assert(!disjointMasks.any((mask) => mask.containsMask(other, classWorld)));
     // If we cover object, we should never get here.
-    assert(!contains(classWorld.objectClass, classWorld));
+    assert(!contains(classWorld.coreClasses.objectClass, classWorld));
     // Likewise, nullness should be covered.
     assert(isNullable || !other.isNullable);
     // The fast test is precise for exact types.
     if (other.isExact) return false;
     // We cannot contain object.
-    if (other.contains(classWorld.objectClass, classWorld)) return false;
+    if (other.contains(classWorld.coreClasses.objectClass, classWorld)) {
+      return false;
+    }
     FlatTypeMask flat = TypeMask.nonForwardingMask(other);
     // Check we cover the base class.
     if (!contains(flat.base, classWorld)) return false;
     // Check for other members.
     Iterable<ClassElement> members;
     if (flat.isSubclass) {
       members = classWorld.strictSubclassesOf(flat.base);
     } else {
       assert(flat.isSubtype);
       members = classWorld.strictSubtypesOf(flat.base);
@@ skipping 134 matching lines @@
   int get hashCode {
     int hashCode = isNullable ? 86 : 43;
     // The order of the masks in [disjointMasks] must not affect the
     // hashCode.
     for (var mask in disjointMasks) {
       hashCode = (hashCode ^ mask.nonNullable().hashCode) & 0x3fffffff;
     }
     return hashCode;
   }
 }