Start work on a non-complete type inferrer. Currently only analyzes return types.

sdk/lib/_internal/compiler/implementation/dart_backend/backend.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.
 
 part of dart_backend;
 
 // TODO(ahe): This class is simply wrong.  This backend should use
 // elements when it can, not AST nodes.  Perhaps a [Map<Element,
 // TreeElements>] is what is needed.
 class ElementAst {
@@ skipping 342 matching lines @@
 
       if (element.isMember()) {
         ClassElement enclosingClass = element.getEnclosingClass();
         assert(enclosingClass.isClass());
         assert(enclosingClass.isTopLevel());
         assert(shouldOutput(enclosingClass));
         addClass(enclosingClass);
         classMembers[enclosingClass].add(element);
         processElement(element, elementAst);
       } else {
-        if (!element.isTopLevel()) {
+        if (element.enclosingElement.isFunction()) {
+          // Closure, nothing to do.
+        } else if (!element.isTopLevel()) {
           compiler.cancel('Cannot process $element', element: element);
+        } else {
+          addTopLevel(element, elementAst);
         }
-        addTopLevel(element, elementAst);
       }
     });
 
     // Add synthesized constructors to classes with no resolved constructors,
     // but which originally had any constructor.  That should prevent
     // those classes from being instantiable with default constructor.
     Identifier synthesizedIdentifier =
         new Identifier(new StringToken(IDENTIFIER_INFO, '', -1));
 
     NextClassElement:
@@ skipping 207 matching lines @@
 }
 
 compareElements(e0, e1) {
   int result = compareBy((e) => e.getLibrary().canonicalUri.toString())(e0, e1);
   if (result != 0) return result;
   return compareBy((e) => e.position().charOffset)(e0, e1);
 }
 
 List<Element> sortElements(Iterable<Element> elements) =>
     sorted(elements, compareElements);