Enable inference in the core libs

lib/src/checker/resolver.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.
 
 /// Encapsulates how to invoke the analyzer resolver and overrides how it
 /// computes types on expressions to use our restricted set of types.
 library dev_compiler.src.checker.resolver;
 
 import 'package:analyzer/analyzer.dart';
 import 'package:analyzer/src/generated/ast.dart';
@@ skipping 105 matching lines @@
 /// overridden members in super classes.
 class LibraryResolverWithInference extends LibraryResolver {
   final ResolverOptions _options;
 
   LibraryResolverWithInference(context, this._options) : super(context);
 
   @override
   void resolveReferencesAndTypes() {
     _resolveVariableReferences();
 
-    // Skip inference in the core libraries (note: resolvedLibraries are the
-    // libraries in the current strongly connected component).
-    if (resolvedLibraries.any((l) => l.librarySource.isInSystemLibrary)) {
-      _resolveReferencesAndTypes(false);
-      return;
-    }
-
     // Run resolution in two stages, skipping method bodies first, so we can run
     // type-inference before we fully analyze methods.
     _resolveReferencesAndTypes(true);
     _runInference();
     _resolveReferencesAndTypes(false);
   }
 
   // Note: this was split from _resolveReferencesAndTypesInLibrary so we do it
   // only once.
   void _resolveVariableReferences() {
@@ skipping 379 matching lines @@
     }
   }
 
   // Review note: no longer need to override visitFunctionExpression, this is
   // handled by the analyzer internally.
   // TODO(vsm): in visitbinaryExpression: check computeStaticReturnType result?
   // TODO(vsm): in visitFunctionDeclaration: Should we ever use the expression
   // type in a (...) => expr or just the written type?
 
 }