Downwards inference. This adds support to the resolver for downwards

pkg/analyzer/test/src/task/strong/checker_test.dart

 // Copyright (c) 2015, 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.
 
 // TODO(jmesserly): this file needs to be refactored, it's a port from
 // package:dev_compiler's tests
 /// General type checking tests
 library test.src.task.strong.checker_test;
 
 import 'package:unittest/unittest.dart';
@@ skipping 14 matching lines @@
         class SplayTreeMap<K, V> {
           Comparator<K> _comparator;
           _Predicate _validKey;
 
           // Initializing _comparator needs a cast, since K may not always be
           // Comparable.
           // Initializing _validKey shouldn't need a cast.  Currently
           // it requires inference to work because of dartbug.com/23381
           SplayTreeMap([int compare(K key1, K key2),
                         bool isValidKey(potentialKey)]) {
-            : _comparator = /*warning:DownCastComposite*/(compare == null) ? Comparable.compare : compare,
-              _validKey = /*info:InferredType should be pass*/(isValidKey != null) ? isValidKey : ((v) => true);
-              _Predicate<Object> _v = /*warning:DownCastComposite*/(isValidKey != null) ? isValidKey : ((v) => true);
-              _v = /*info:InferredType should be pass*/(isValidKey != null) ? _v : ((v) => true);
+            : _comparator = /*warning:DownCastComposite*/(compare == null)
+                           ? Comparable.compare : compare,
+              _validKey = /*warning:DownCastComposite*/(isValidKey != null)
+                         ? isValidKey : ((v) => true);
+             _Predicate<Object> _v = /*warning:DownCastComposite*/(isValidKey != null)
+                                    ? isValidKey : (/*info:InferredTypeClosure*/(v) => true);
+        // TODO(leafp): Fix unimplemented LUB in analyzer
+        _v = /*warning:DownCastComposite*/(isValidKey != null)
+             ? _v : (/*info:InferredTypeClosure*/(v) => true);
           }
         }
         void main() {
           Object obj = 42;
           dynamic dyn = 42;
           int i = 42;
 
           // Check the boolean conversion of the condition.
           print((/*severe:StaticTypeError*/i) ? false : true);
           print((/*info:DownCastImplicit*/obj) ? false : true);
@@ skipping 2350 matching lines @@
 
         baz1() sync* { yield* (/*info:DynamicCast*/x); }
         Iterable baz2() sync* { yield* (/*info:DynamicCast*/x); }
         Iterable<int> baz3() sync* { yield* (/*warning:DownCastComposite*/x); }
         Iterable<int> baz4() sync* { yield* new Iterable<int>(); }
         Iterable<int> baz5() sync* { yield* (/*info:InferredTypeAllocation*/new Iterable()); }
     '''
     });
   });
 }