Support deserialized compilation of the empty program.

pkg/compiler/lib/src/js_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 js_backend;
 
 const VERBOSE_OPTIMIZER_HINTS = false;
 
 class JavaScriptItemCompilationContext extends ItemCompilationContext {
   final Set<HInstruction> boundsChecked = new Set<HInstruction>();
@@ skipping 493 matching lines @@
 
   SourceInformationStrategy sourceInformationStrategy;
 
   JavaScriptBackendSerialization serialization;
 
   final NativeData nativeData = new NativeData();
 
   final BackendHelpers helpers;
   final BackendImpacts impacts;
 
+  JSFrontendAccess _frontend;
+
   JavaScriptBackend(Compiler compiler,
       {bool generateSourceMap: true,
       bool useStartupEmitter: false,
       bool useNewSourceInfo: false})
       : namer = determineNamer(compiler),
         oneShotInterceptors = new Map<jsAst.Name, Selector>(),
         interceptedElements = new Map<String, Set<Element>>(),
         rti = new _RuntimeTypes(compiler),
         rtiEncoder = new _RuntimeTypesEncoder(compiler),
         specializedGetInterceptors = new Map<jsAst.Name, Set<ClassElement>>(),
@@ skipping 14 matching lines @@
     jsInteropAnalysis = new JsInteropAnalysis(this);
 
     noSuchMethodRegistry = new NoSuchMethodRegistry(this);
     constantCompilerTask = new JavaScriptConstantTask(compiler);
     impactTransformer = new JavaScriptImpactTransformer(this);
     patchResolverTask = new PatchResolverTask(compiler);
     functionCompiler = compiler.options.useCpsIr
         ? new CpsFunctionCompiler(compiler, this, sourceInformationStrategy)
         : new SsaFunctionCompiler(this, sourceInformationStrategy);
     serialization = new JavaScriptBackendSerialization(this);
+    _frontend = new JSFrontendAccess(compiler);

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

seems it should be possible to make this an initializer and convert _frontend
into a `final frontend` instead

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

Done.

   }
 
   ConstantSystem get constantSystem => constants.constantSystem;
 
   DiagnosticReporter get reporter => compiler.reporter;
 
   CoreClasses get coreClasses => compiler.coreClasses;
 
   CoreTypes get coreTypes => compiler.coreTypes;
 
@@ skipping 1908 matching lines @@
   @override
   ImpactStrategy createImpactStrategy(
       {bool supportDeferredLoad: true,
       bool supportDumpInfo: true,
       bool supportSerialization: true}) {
     return new JavaScriptImpactStrategy(resolution, compiler.dumpInfoTask,
         supportDeferredLoad: supportDeferredLoad,
         supportDumpInfo: supportDumpInfo,
         supportSerialization: supportSerialization);
   }
+
+  @override
+  Frontend get frontend => _frontend;
+}
+
+class JSFrontendAccess implements Frontend {
+  final Compiler compiler;
+
+  JSFrontendAccess(this.compiler);
+
+  Resolution get resolution => compiler.resolution;
+
+  @override
+  ResolutionImpact getResolutionImpact(Element element) {
+    return resolution.getResolutionImpact(element);
+  }
+
+  @override
+  ResolvedAst getResolvedAst(Element element) {
+    if (element is SynthesizedCallMethodElementX) {
+      return element.resolvedAst;
+    } else if (element is ConstructorBodyElementX) {
+      return element.resolvedAst;
+    } else {
+      assert(invariant(element, resolution.hasResolvedAst(element.declaration),
+          message: 'No ResolvedAst for $element'));
+      return resolution.getResolvedAst(element.declaration);
+    }
+  }
 }
 
 /// Handling of special annotations for tests.
 class Annotations {
   static final Uri PACKAGE_EXPECT =
       new Uri(scheme: 'package', path: 'expect/expect.dart');
 
   final Compiler compiler;
 
   ClassElement expectNoInlineClass;
@@ skipping 490 matching lines @@
 
   @override
   void onImpactUsed(ImpactUseCase impactUse) {
     if (impactUse == DeferredLoadTask.IMPACT_USE && !supportSerialization) {
       // TODO(johnniwinther): Allow emptying when serialization has been
       // performed.
       resolution.emptyCache();
     }
   }
 }