Support deserialized compilation of the empty program.

pkg/compiler/lib/src/common/resolution.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 dart2js.common.resolution;
 
 import '../common.dart';
 import '../compiler.dart' show Compiler;
 import '../constants/expressions.dart' show ConstantExpression;
 import '../core_types.dart' show CoreTypes;
@@ skipping 164 matching lines @@
     return type == other.type &&
         isConstant == other.isConstant &&
         isEmpty == other.isEmpty;
   }
 
   String toString() {
     return 'ListLiteralUse($type,isConstant:$isConstant,isEmpty:$isEmpty)';
   }
 }
 
+/// Interface for the accessing the front-end analysis.
+abstract class Frontend {

[Siggi Cherem (dart-lang), 2016/04/15 15:42:14]

I ponder about the name here.... "Frontend" makes sense in the context of the
backend, but it might be too broad when all of
parsing/resolution/deserialization is part of a frontend. 

Here are some other ideas:

- "Resolver" (although it feels incorrect, since it might not be the one doing
the resolution when it loads the data from a serialized format).

- "ResolutionProvider"?

If you are not convinced about the latter, we can keep Frontend while we
brainstorm for other ideas.

[Johnni Winther, 2016/04/18 08:05:43]

'ResolutionProvider' is semantically the best but I don't like the 'Provider'
suffix. I don't particularly like 'Frontend' though it is fun to write
'compiler.backend.frontend' ;-)  Let's brainstorm a bit (added a TODO).

+  /// Returns the `ResolvedAst` for the [element].
+  ResolvedAst getResolvedAst(Element element);
+
+  /// Returns the [ResolutionImpact] for [element].
+  ResolutionImpact getResolutionImpact(Element element);
+}
+
 // TODO(johnniwinther): Rename to `Resolver` or `ResolverContext`.
-abstract class Resolution {
+abstract class Resolution extends Frontend {

[Siggi Cherem (dart-lang), 2016/04/15 15:42:14]

it doesn't' really matter, but for some reason this feels like it should be
`implements` rather than `extends`?

[Johnni Winther, 2016/04/18 08:05:43]

Done.

   Parsing get parsing;
   DiagnosticReporter get reporter;
   CoreTypes get coreTypes;
 
   /// If set to `true` resolution caches will not be cleared. Use this only for
   /// testing.
   bool retainCachesForTesting;
 
   void resolveTypedef(TypedefElement typdef);
   void resolveClass(ClassElement cls);
@@ skipping 36 matching lines @@
 }
 
 // TODO(johnniwinther): Rename to `Parser` or `ParsingContext`.
 abstract class Parsing {
   DiagnosticReporter get reporter;
   void parsePatchClass(ClassElement cls);
   measure(f());
   ScannerOptions getScannerOptionsFor(Element element);
   ParserOptions get parserOptions;
 }