dart2js cps: Type casts and related changes to type propagation.

pkg/compiler/lib/src/dart_types.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.
 
 library dart_types;
 
 import 'dart:math' show min;
 
 import 'core_types.dart';
 import 'dart2jslib.dart' show Compiler, invariant, Script, Message;
@@ skipping 1214 matching lines @@
                                     TypeVariableType typeVariable,
                                     DartType bound);
 
 /// Basic interface for the Dart type system.
 abstract class DartTypes {
   /// The types defined in 'dart:core'.
   CoreTypes get coreTypes;
 
   /// Returns `true` if [t] is a subtype of [s].
   bool isSubtype(DartType t, DartType s);
+
+  /// Returns `true` if [t] might be a subtype of [s] for some values of
+  /// type variables in [s] and [t].
+  bool isPotentialSubtype(DartType t, DartType s);
 }
 
 class Types implements DartTypes {
   // TODO(johnniwinther): Replace by [CoreTypes].
   final Compiler compiler;
   final MoreSpecificVisitor moreSpecificVisitor;
   final SubtypeVisitor subtypeVisitor;
   final PotentialSubtypeVisitor potentialSubtypeVisitor;
 
   CoreTypes get coreTypes => compiler.coreTypes;
@@ skipping 633 matching lines @@
         }
         namedParameterTypes[index].accept(this, namedParameters[index]);
         needsComma = true;
       }
       sb.write('}');
     }
     sb.write(')');
   }
 }