fixes strong mode assignability

pkg/analyzer/lib/src/generated/resolver.dart

 // Copyright (c) 2014, 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 engine.resolver;
 
 import 'dart:collection';
 
 import 'ast.dart';
 import 'constant.dart';
@@ skipping 15083 matching lines @@
 
   @override
   DartType getLeastUpperBound(
       TypeProvider typeProvider, DartType type1, DartType type2) {
     // TODO(leafp): Implement a strong mode version of this.
     return _specTypeSystem.getLeastUpperBound(typeProvider, type1, type2);
   }
 
   // TODO(leafp): Document the rules in play here
   @override
-  bool isAssignableTo(DartType toType, DartType fromType) {
+  bool isAssignableTo(DartType fromType, DartType toType) {

[Jennifer Messerly, 2015/10/01 22:24:15]

think of it as "fromType isAssignableTo toType"

     // An actual subtype
     if (isSubtypeOf(fromType, toType)) {
       return true;
     }
 
     // Don't allow implicit downcasts between function types
     // and call method objects, as these will almost always fail.
     if ((fromType is FunctionType && _getCallMethodType(toType) != null) ||
         (toType is FunctionType && _getCallMethodType(fromType) != null)) {
       return false;
@@ skipping 834 matching lines @@
     nonFields.add(node);
     return null;
   }
 
   @override
   Object visitNode(AstNode node) => node.accept(TypeResolverVisitor_this);
 
   @override
   Object visitWithClause(WithClause node) => null;
 }