Remove old dart2js code.

sdk/lib/_internal/compiler/implementation/compiler.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 dart2js;
-
-/**
- * If true, print a warning for each method that was resolved, but not
- * compiled.
- */
-const bool REPORT_EXCESS_RESOLUTION = false;
-
-/**
- * Contains backend-specific data that is used throughout the compilation of
- * one work item.
- */
-class ItemCompilationContext {
-}
-
-abstract class WorkItem {
-  final ItemCompilationContext compilationContext;
-  /**
-   * Documentation wanted -- johnniwinther
-   *
-   * Invariant: [element] must be a declaration element.
-   */
-  final AstElement element;
-  TreeElements get resolutionTree;
-
-  WorkItem(this.element, this.compilationContext) {
-    assert(invariant(element, element.isDeclaration));
-  }
-
-  void run(Compiler compiler, Enqueuer world);
-}
-
-/// [WorkItem] used exclusively by the [ResolutionEnqueuer].
-class ResolutionWorkItem extends WorkItem {
-  TreeElements resolutionTree;
-
-  ResolutionWorkItem(AstElement element,
-                     ItemCompilationContext compilationContext)
-      : super(element, compilationContext);
-
-  void run(Compiler compiler, ResolutionEnqueuer world) {
-    compiler.analyze(this, world);
-    resolutionTree = element.resolvedAst.elements;
-  }
-
-  bool isAnalyzed() => resolutionTree != null;
-}
-
-// TODO(johnniwinther): Split this class into interface and implementation.
-// TODO(johnniwinther): Move this implementation to the JS backend.
-class CodegenRegistry extends Registry {
-  final Compiler compiler;
-  final TreeElements treeElements;
-
-  CodegenRegistry(this.compiler, this.treeElements);
-
-  bool get isForResolution => false;
-
-  Element get currentElement => treeElements.analyzedElement;
-
-  // TODO(johnniwinther): Remove this getter when [Registry] creates a
-  // dependency node.
-  Setlet<Element> get otherDependencies => treeElements.otherDependencies;
-
-  CodegenEnqueuer get world => compiler.enqueuer.codegen;
-  js_backend.JavaScriptBackend get backend => compiler.backend;
-
-  void registerDependency(Element element) {
-    treeElements.registerDependency(element);
-  }
-
-  void registerInlining(Element inlinedElement, Element context) {
-    if (compiler.dumpInfo) {
-      compiler.dumpInfoTask.registerInlined(inlinedElement, context);
-    }
-  }
-
-  void registerInstantiatedClass(ClassElement element) {
-    world.registerInstantiatedClass(element, this);
-  }
-
-  void registerInstantiatedType(InterfaceType type) {
-    world.registerInstantiatedType(type, this);
-  }
-
-  void registerStaticUse(Element element) {
-    world.registerStaticUse(element);
-  }
-
-  void registerDynamicInvocation(Selector selector) {
-    world.registerDynamicInvocation(selector);
-    compiler.dumpInfoTask.elementUsesSelector(currentElement, selector);
-  }
-
-  void registerDynamicSetter(Selector selector) {
-    world.registerDynamicSetter(selector);
-    compiler.dumpInfoTask.elementUsesSelector(currentElement, selector);
-  }
-
-  void registerDynamicGetter(Selector selector) {
-    world.registerDynamicGetter(selector);
-    compiler.dumpInfoTask.elementUsesSelector(currentElement, selector);
-  }
-
-  void registerGetterForSuperMethod(Element element) {
-    world.registerGetterForSuperMethod(element);
-  }
-
-  void registerFieldGetter(Element element) {
-    world.registerFieldGetter(element);
-  }
-
-  void registerFieldSetter(Element element) {
-    world.registerFieldSetter(element);
-  }
-
-  void registerIsCheck(DartType type) {
-    world.registerIsCheck(type, this);
-    backend.registerIsCheckForCodegen(type, world, this);
-  }
-
-  void registerCompileTimeConstant(ConstantValue constant) {
-    backend.registerCompileTimeConstant(constant, this);
-    backend.constants.addCompileTimeConstantForEmission(constant);
-  }
-
-  void registerTypeVariableBoundsSubtypeCheck(DartType subtype,
-                                              DartType supertype) {
-    backend.registerTypeVariableBoundsSubtypeCheck(subtype, supertype);
-  }
-
-  void registerClosureWithFreeTypeVariables(FunctionElement element) {
-    backend.registerClosureWithFreeTypeVariables(element, world, this);
-  }
-
-  void registerGetOfStaticFunction(FunctionElement element) {
-    world.registerGetOfStaticFunction(element);
-  }
-
-  void registerSelectorUse(Selector selector) {
-    world.registerSelectorUse(selector);
-  }
-
-  void registerFactoryWithTypeArguments() {
-    world.registerFactoryWithTypeArguments(this);
-  }
-
-  void registerConstSymbol(String name) {
-    backend.registerConstSymbol(name, this);
-  }
-
-  void registerSpecializedGetInterceptor(Set<ClassElement> classes) {
-    backend.registerSpecializedGetInterceptor(classes);
-  }
-
-  void registerUseInterceptor() {
-    backend.registerUseInterceptor(world);
-  }
-
-  void registerTypeConstant(ClassElement element) {
-    backend.customElementsAnalysis.registerTypeConstant(element, world);
-  }
-
-  void registerStaticInvocation(Element element) {
-    world.registerStaticUse(element);
-  }
-
-  void registerInstantiation(InterfaceType type) {
-    world.registerInstantiatedType(type, this);
-  }
-}
-
-/// [WorkItem] used exclusively by the [CodegenEnqueuer].
-class CodegenWorkItem extends WorkItem {
-  Registry registry;
-  final TreeElements resolutionTree;
-
-  CodegenWorkItem(AstElement element,
-                  ItemCompilationContext compilationContext)
-      : this.resolutionTree = element.resolvedAst.elements,
-        super(element, compilationContext) {
-    assert(invariant(element, resolutionTree != null,
-        message: 'Resolution tree is null for $element in codegen work item'));
-  }
-
-  void run(Compiler compiler, CodegenEnqueuer world) {
-    if (world.isProcessed(element)) return;
-
-    registry = new CodegenRegistry(compiler, resolutionTree);
-    compiler.codegen(this, world);
-  }
-}
-
-typedef void DeferredAction();
-
-class DeferredTask {
-  final Element element;
-  final DeferredAction action;
-
-  DeferredTask(this.element, this.action);
-}
-
-/// Interface for registration of element dependencies.
-abstract class Registry {
-  // TODO(johnniwinther): Remove this getter when [Registry] creates a
-  // dependency node.
-  Iterable<Element> get otherDependencies;
-
-  void registerDependency(Element element);
-
-  bool get isForResolution;
-
-  void registerStaticInvocation(Element element);
-
-  void registerInstantiation(InterfaceType type);
-
-  void registerGetOfStaticFunction(FunctionElement element);
-}
-
-abstract class Backend {
-  final Compiler compiler;
-
-  Backend(this.compiler);
-
-  /// The [ConstantSystem] used to interpret compile-time constants for this
-  /// backend.
-  ConstantSystem get constantSystem;
-
-  /// The constant environment for the backend interpretation of compile-time
-  /// constants.
-  BackendConstantEnvironment get constants;
-
-  /// The compiler task responsible for the compilation of constants for both
-  /// the frontend and the backend.
-  ConstantCompilerTask get constantCompilerTask;
-
-  /// Backend callback methods for the resolution phase.
-  ResolutionCallbacks get resolutionCallbacks;
-
-  /// Set of classes that need to be considered for reflection although not
-  /// otherwise visible during resolution.
-  Iterable<ClassElement> classesRequiredForReflection = const [];
-
-  // Given a [FunctionElement], return a buffer with the code generated for it
-  // or null if no code was generated.
-  CodeBuffer codeOf(Element element) => null;
-
-  void initializeHelperClasses() {}
-
-  void enqueueHelpers(ResolutionEnqueuer world, Registry registry);
-  void codegen(CodegenWorkItem work);
-
-  // The backend determines the native resolution enqueuer, with a no-op
-  // default, so tools like dart2dart can ignore the native classes.
-  native.NativeEnqueuer nativeResolutionEnqueuer(world) {
-    return new native.NativeEnqueuer();
-  }
-  native.NativeEnqueuer nativeCodegenEnqueuer(world) {
-    return new native.NativeEnqueuer();
-  }
-
-  void assembleProgram();
-  List<CompilerTask> get tasks;
-
-  void onResolutionComplete() {}
-
-  ItemCompilationContext createItemCompilationContext() {
-    return new ItemCompilationContext();
-  }
-
-  bool classNeedsRti(ClassElement cls);
-  bool methodNeedsRti(FunctionElement function);
-
-  /// Called during codegen when [constant] has been used.
-  void registerCompileTimeConstant(ConstantValue constant, Registry registry) {}
-
-  /// Called during resolution when a constant value for [metadata] on
-  /// [annotatedElement] has been evaluated.
-  void registerMetadataConstant(MetadataAnnotation metadata,
-                                Element annotatedElement,
-                                Registry registry) {}
-
-  /// Called during resolution to notify to the backend that a class is
-  /// being instantiated.
-  void registerInstantiatedClass(ClassElement cls,
-                                 Enqueuer enqueuer,
-                                 Registry registry) {}
-
-  /// Register an is check to the backend.
-  void registerIsCheckForCodegen(DartType type,
-                                 Enqueuer enqueuer,
-                                 Registry registry) {}
-
-  /// Register a runtime type variable bound tests between [typeArgument] and
-  /// [bound].
-  void registerTypeVariableBoundsSubtypeCheck(DartType typeArgument,
-                                              DartType bound) {}
-
-  /// Returns `true` if [element] represent the assert function.
-  bool isAssertMethod(Element element) => false;
-
-  /**
-   * Call this to register that an instantiated generic class has a call
-   * method.
-   */
-  void registerCallMethodWithFreeTypeVariables(
-      Element callMethod,
-      Enqueuer enqueuer,
-      Registry registry) {}
-
-  /**
-   * Call this to register that a getter exists for a function on an
-   * instantiated generic class.
-   */
-  void registerClosureWithFreeTypeVariables(
-      Element closure,
-      Enqueuer enqueuer,
-      Registry registry) {}
-
-  /// Call this to register that a member has been closurized.
-  void registerBoundClosure(Enqueuer enqueuer) {}
-
-  /// Call this to register that a static function has been closurized.
-  void registerGetOfStaticFunction(Enqueuer enqueuer) {}
-
-  /**
-   * Call this to register that the [:runtimeType:] property has been accessed.
-   */
-  void registerRuntimeType(Enqueuer enqueuer, Registry registry) {}
-
-  /**
-   * Call this method to enable [noSuchMethod] handling in the
-   * backend.
-   */
-  void enableNoSuchMethod(Element context, Enqueuer enqueuer) {
-    enqueuer.registerInvocation(compiler.noSuchMethodSelector);
-  }
-
-  /// Call this method to enable support for isolates.
-  void enableIsolateSupport(Enqueuer enqueuer) {}
-
-  void registerRequiredType(DartType type, Element enclosingElement) {}
-  void registerClassUsingVariableExpression(ClassElement cls) {}
-
-  void registerConstSymbol(String name, Registry registry) {}
-  void registerNewSymbol(Registry registry) {}
-
-  bool isNullImplementation(ClassElement cls) {
-    return cls == compiler.nullClass;
-  }
-
-  ClassElement get intImplementation => compiler.intClass;
-  ClassElement get doubleImplementation => compiler.doubleClass;
-  ClassElement get numImplementation => compiler.numClass;
-  ClassElement get stringImplementation => compiler.stringClass;
-  ClassElement get listImplementation => compiler.listClass;
-  ClassElement get growableListImplementation => compiler.listClass;
-  ClassElement get fixedListImplementation => compiler.listClass;
-  ClassElement get constListImplementation => compiler.listClass;
-  ClassElement get mapImplementation => compiler.mapClass;
-  ClassElement get constMapImplementation => compiler.mapClass;
-  ClassElement get functionImplementation => compiler.functionClass;
-  ClassElement get typeImplementation => compiler.typeClass;
-  ClassElement get boolImplementation => compiler.boolClass;
-  ClassElement get nullImplementation => compiler.nullClass;
-  ClassElement get uint32Implementation => compiler.intClass;
-  ClassElement get uint31Implementation => compiler.intClass;
-  ClassElement get positiveIntImplementation => compiler.intClass;
-
-  ClassElement defaultSuperclass(ClassElement element) => compiler.objectClass;
-
-  bool isDefaultNoSuchMethodImplementation(Element element) {
-    assert(element.name == Compiler.NO_SUCH_METHOD);
-    ClassElement classElement = element.enclosingClass;
-    return classElement == compiler.objectClass;
-  }
-
-  bool isInterceptorClass(ClassElement element) => false;
-
-  /// Returns `true` if [element] is a foreign element, that is, that the
-  /// backend has specialized handling for the element.
-  bool isForeign(Element element) => false;
-
-  /// Returns `true` if [library] is a backend specific library whose members
-  /// have special treatment, such as being allowed to extends blacklisted
-  /// classes or member being eagerly resolved.
-  bool isBackendLibrary(LibraryElement library) {
-    // TODO(johnnwinther): Remove this when patching is only done by the
-    // JavaScript backend.
-    Uri canonicalUri = library.canonicalUri;
-    if (canonicalUri == js_backend.JavaScriptBackend.DART_JS_HELPER ||
-        canonicalUri == js_backend.JavaScriptBackend.DART_INTERCEPTORS) {
-      return true;
-    }
-    return false;
-  }
-
-  void registerStaticUse(Element element, Enqueuer enqueuer) {}
-
-  /// This method is called immediately after the [LibraryElement] [library] has
-  /// been created.
-  void onLibraryCreated(LibraryElement library) {}
-
-  /// This method is called immediately after the [library] and its parts have
-  /// been scanned.
-  Future onLibraryScanned(LibraryElement library, LibraryLoader loader) {
-    if (library.isPlatformLibrary && !library.isPatched) {
-      // Apply patch, if any.
-      Uri patchUri = compiler.resolvePatchUri(library.canonicalUri.path);
-      if (patchUri != null) {
-        return compiler.patchParser.patchLibrary(loader, patchUri, library);
-      }
-    }
-    if (library.canUseNative) {
-      library.forEachLocalMember((Element element) {
-        if (element.isClass) {
-          checkNativeAnnotation(compiler, element);
-        }
-      });
-    }
-    return new Future.value();
-  }
-
-  /// This method is called when all new libraries loaded through
-  /// [LibraryLoader.loadLibrary] has been loaded and their imports/exports
-  /// have been computed.
-  Future onLibrariesLoaded(Map<Uri, LibraryElement> loadedLibraries) {
-    return new Future.value();
-  }
-
-  /// Called by [MirrorUsageAnalyzerTask] after it has merged all @MirrorsUsed
-  /// annotations. The arguments corresponds to the unions of the corresponding
-  /// fields of the annotations.
-  void registerMirrorUsage(Set<String> symbols,
-                           Set<Element> targets,
-                           Set<Element> metaTargets) {}
-
-  /// Returns true if this element needs reflection information at runtime.
-  bool isAccessibleByReflection(Element element) => true;
-
-  /// Returns true if this element is covered by a mirrorsUsed annotation.
-  ///
-  /// Note that it might still be ok to tree shake the element away if no
-  /// reflection is used in the program (and thus [isTreeShakingDisabled] is
-  /// still false). Therefore _do not_ use this predicate to decide inclusion
-  /// in the tree, use [requiredByMirrorSystem] instead.
-  bool referencedFromMirrorSystem(Element element, [recursive]) => false;
-
-  /// Returns true if this element has to be enqueued due to
-  /// mirror usage. Might be a subset of [referencedFromMirrorSystem] if
-  /// normal tree shaking is still active ([isTreeShakingDisabled] is false).
-  bool requiredByMirrorSystem(Element element) => false;
-
-  /// Returns true if global optimizations such as type inferencing
-  /// can apply to this element. One category of elements that do not
-  /// apply is runtime helpers that the backend calls, but the
-  /// optimizations don't see those calls.
-  bool canBeUsedForGlobalOptimizations(Element element) => true;
-
-  /// Called when [enqueuer]'s queue is empty, but before it is closed.
-  /// This is used, for example, by the JS backend to enqueue additional
-  /// elements needed for reflection. [recentClasses] is a collection of
-  /// all classes seen for the first time by the [enqueuer] since the last call
-  /// to [onQueueEmpty].
-  ///
-  /// A return value of [:true:] indicates that [recentClasses] has been
-  /// processed and its elements do not need to be seen in the next round. When
-  /// [:false:] is returned, [onQueueEmpty] will be called again once the
-  /// resolution queue has drained and [recentClasses] will be a superset of the
-  /// current value.
-  ///
-  /// There is no guarantee that a class is only present once in
-  /// [recentClasses], but every class seen by the [enqueuer] will be present in
-  /// [recentClasses] at least once.
-  bool onQueueEmpty(Enqueuer enqueuer, Iterable<ClassElement> recentClasses) {
-    return true;
-  }
-
-  /// Called after [element] has been resolved.
-  // TODO(johnniwinther): Change [TreeElements] to [Registry] or a dependency
-  // node. [elements] is currently unused by the implementation.
-  void onElementResolved(Element element, TreeElements elements) {}
-
-  // Does this element belong in the output
-  bool shouldOutput(Element element) => true;
-
-  FunctionElement helperForBadMain() => null;
-
-  FunctionElement helperForMissingMain() => null;
-
-  FunctionElement helperForMainArity() => null;
-
-  void forgetElement(Element element) {}
-
-  void registerMainHasArguments(Enqueuer enqueuer) {}
-}
-
-/// Backend callbacks function specific to the resolution phase.
-class ResolutionCallbacks {
-  /// Register that [node] is a call to `assert`.
-  void onAssert(Send node, Registry registry) {}
-
-  /// Called during resolution to notify to the backend that the
-  /// program uses string interpolation.
-  void onStringInterpolation(Registry registry) {}
-
-  /// Called during resolution to notify to the backend that the
-  /// program has a catch statement.
-  void onCatchStatement(Registry registry) {}
-
-  /// Called during resolution to notify to the backend that the
-  /// program explicitly throws an exception.
-  void onThrowExpression(Registry registry) {}
-
-  /// Called during resolution to notify to the backend that the
-  /// program has a global variable with a lazy initializer.
-  void onLazyField(Registry registry) {}
-
-  /// Called during resolution to notify to the backend that the
-  /// program uses a type variable as an expression.
-  void onTypeVariableExpression(Registry registry) {}
-
-  /// Called during resolution to notify to the backend that the
-  /// program uses a type literal.
-  void onTypeLiteral(DartType type, Registry registry) {}
-
-  /// Called during resolution to notify to the backend that the
-  /// program has a catch statement with a stack trace.
-  void onStackTraceInCatch(Registry registry) {}
-
-  /// Register an is check to the backend.
-  void onIsCheck(DartType type, Registry registry) {}
-
-  /// Register an as check to the backend.
-  void onAsCheck(DartType type, Registry registry) {}
-
-  /// Registers that a type variable bounds check might occur at runtime.
-  void onTypeVariableBoundCheck(Registry registry) {}
-
-  /// Register that the application may throw a [NoSuchMethodError].
-  void onThrowNoSuchMethod(Registry registry) {}
-
-  /// Register that the application may throw a [RuntimeError].
-  void onThrowRuntimeError(Registry registry) {}
-
-  /// Register that the application may throw an
-  /// [AbstractClassInstantiationError].
-  void onAbstractClassInstantiation(Registry registry) {}
-
-  /// Register that the application may throw a [FallThroughError].
-  void onFallThroughError(Registry registry) {}
-
-  /// Register that a super call will end up calling
-  /// [: super.noSuchMethod :].
-  void onSuperNoSuchMethod(Registry registry) {}
-
-  /// Register that the application creates a constant map.
-  void onConstantMap(Registry registry) {}
-
-  /// Called when resolving the `Symbol` constructor.
-  void onSymbolConstructor(Registry registry) {}
-}
-
-/**
- * Key class used in [TokenMap] in which the hash code for a token is based
- * on the [charOffset].
- */
-class TokenKey {
-  final Token token;
-  TokenKey(this.token);
-  int get hashCode => token.charOffset;
-  operator==(other) => other is TokenKey && token == other.token;
-}
-
-/// Map of tokens and the first associated comment.
-/*
- * This implementation was chosen among several candidates for its space/time
- * efficiency by empirical tests of running dartdoc on dartdoc itself. Time
- * measurements for the use of [Compiler.commentMap]:
- *
- * 1) Using [TokenKey] as key (this class): ~80 msec
- * 2) Using [TokenKey] as key + storing a separate map in each script: ~120 msec
- * 3) Using [Token] as key in a [Map]: ~38000 msec
- * 4) Storing comments is new field in [Token]: ~20 msec
- *    (Abandoned due to the increased memory usage)
- * 5) Storing comments in an [Expando]: ~14000 msec
- * 6) Storing token/comments pairs in a linked list: ~5400 msec
- */
-class TokenMap {
-  Map<TokenKey,Token> comments = new Map<TokenKey,Token>();
-
-  Token operator[] (Token key) {
-    if (key == null) return null;
-    return comments[new TokenKey(key)];
-  }
-
-  void operator[]= (Token key, Token value) {
-    if (key == null) return;
-    comments[new TokenKey(key)] = value;
-  }
-}
-
-abstract class Compiler implements DiagnosticListener {
-  static final Uri DART_CORE = new Uri(scheme: 'dart', path: 'core');
-  static final Uri DART_MIRRORS = new Uri(scheme: 'dart', path: 'mirrors');
-  static final Uri DART_NATIVE_TYPED_DATA =
-      new Uri(scheme: 'dart', path: '_native_typed_data');
-  static final Uri DART_INTERNAL = new Uri(scheme: 'dart', path: '_internal');
-  static final Uri DART_ASYNC = new Uri(scheme: 'dart', path: 'async');
-
-  final Stopwatch totalCompileTime = new Stopwatch();
-  int nextFreeClassId = 0;
-  World world;
-  String assembledCode;
-  Types types;
-
-  final CacheStrategy cacheStrategy;
-
-  /**
-   * Map from token to the first preceeding comment token.
-   */
-  final TokenMap commentMap = new TokenMap();
-
-  /**
-   * Records global dependencies, that is, dependencies that don't
-   * correspond to a particular element.
-   *
-   * We should get rid of this and ensure that all dependencies are
-   * associated with a particular element.
-   */
-  Registry globalDependencies;
-
-  /**
-   * Dependencies that are only included due to mirrors.
-   *
-   * We should get rid of this and ensure that all dependencies are
-   * associated with a particular element.
-   */
-  // TODO(johnniwinther): This should not be a [ResolutionRegistry].
-  final Registry mirrorDependencies =
-      new ResolutionRegistry.internal(null, new TreeElementMapping(null));
-
-  final bool enableMinification;
-
-  /// When `true` emits URIs in the reflection metadata.
-  final bool preserveUris;
-
-  final bool enableTypeAssertions;
-  final bool enableUserAssertions;
-  final bool trustTypeAnnotations;
-  final bool enableConcreteTypeInference;
-  final bool disableTypeInferenceFlag;
-  final bool dumpInfo;
-  final bool useContentSecurityPolicy;
-
-  /**
-   * The maximum size of a concrete type before it widens to dynamic during
-   * concrete type inference.
-   */
-  final int maxConcreteTypeSize;
-  final bool analyzeAllFlag;
-  final bool analyzeOnly;
-
-  /// If true, disable tree-shaking for the main script.
-  final bool analyzeMain;
-
-  /**
-   * If true, skip analysis of method bodies and field initializers. Implies
-   * [analyzeOnly].
-   */
-  final bool analyzeSignaturesOnly;
-  final bool enableNativeLiveTypeAnalysis;
-
-  /**
-   * If true, stop compilation after type inference is complete. Used for
-   * debugging and testing purposes only.
-   */
-  bool stopAfterTypeInference = false;
-
-  /**
-   * If [:true:], comment tokens are collected in [commentMap] during scanning.
-   */
-  final bool preserveComments;
-
-  /**
-   * Is the compiler in verbose mode.
-   */
-  final bool verbose;
-
-  /**
-   * URI of the main source map if the compiler is generating source
-   * maps.
-   */
-  final Uri sourceMapUri;
-
-  /**
-   * URI of the main output if the compiler is generating source maps.
-   */
-  final Uri outputUri;
-
-  /// Emit terse diagnostics without howToFix.
-  final bool terseDiagnostics;
-
-  /// If `true`, warnings and hints not from user code are reported.
-  final bool showPackageWarnings;
-
-  /// `true` if the last diagnostic was filtered, in which case the
-  /// accompanying info message should be filtered as well.
-  bool lastDiagnosticWasFiltered = false;
-
-  /// Map containing information about the warnings and hints that have been
-  /// suppressed for each library.
-  Map<Uri, SuppressionInfo> suppressedWarnings = <Uri, SuppressionInfo>{};
-
-  final bool suppressWarnings;
-
-  /// If `true`, some values are cached for reuse in incremental compilation.
-  /// Incremental compilation is basically calling [run] more than once.
-  final bool hasIncrementalSupport;
-
-  api.CompilerOutputProvider outputProvider;
-
-  bool disableInlining = false;
-
-  /// True if compilation was aborted with a [CompilerCancelledException]. Only
-  /// set after Future retuned by [run] has completed.
-  bool compilerWasCancelled = false;
-
-  List<Uri> librariesToAnalyzeWhenRun;
-
-  Tracer tracer;
-
-  CompilerTask measuredTask;
-  Element _currentElement;
-  LibraryElement coreLibrary;
-
-  LibraryElement mainApp;
-  FunctionElement mainFunction;
-
-  /// Initialized when dart:mirrors is loaded.
-  LibraryElement mirrorsLibrary;
-
-  /// Initialized when dart:typed_data is loaded.
-  LibraryElement typedDataLibrary;
-
-  ClassElement objectClass;
-  ClassElement boolClass;
-  ClassElement numClass;
-  ClassElement intClass;
-  ClassElement doubleClass;
-  ClassElement stringClass;
-  ClassElement functionClass;
-  ClassElement nullClass;
-  ClassElement listClass;
-  ClassElement typeClass;
-  ClassElement mapClass;
-  ClassElement symbolClass;
-  ClassElement stackTraceClass;
-  ClassElement typedDataClass;
-
-  /// The constant for the [proxy] variable defined in dart:core.
-  ConstantValue proxyConstant;
-
-  // TODO(johnniwinther): Move this to the JavaScriptBackend.
-  /// The constant for the [patch] variable defined in dart:_js_helper.
-  ConstantValue patchConstant;
-
-  // TODO(johnniwinther): Move this to the JavaScriptBackend.
-  ClassElement nativeAnnotationClass;
-
-  // Initialized after symbolClass has been resolved.
-  FunctionElement symbolConstructor;
-
-  // Initialized when dart:mirrors is loaded.
-  ClassElement mirrorSystemClass;
-
-  // Initialized when dart:mirrors is loaded.
-  ClassElement mirrorsUsedClass;
-
-  // Initialized after mirrorSystemClass has been resolved.
-  FunctionElement mirrorSystemGetNameFunction;
-
-  // Initialized when dart:_internal is loaded.
-  ClassElement symbolImplementationClass;
-
-  // Initialized when symbolImplementationClass has been resolved.
-  FunctionElement symbolValidatedConstructor;
-
-  // Initialized when mirrorsUsedClass has been resolved.
-  FunctionElement mirrorsUsedConstructor;
-
-  // Initialized when dart:mirrors is loaded.
-  ClassElement deferredLibraryClass;
-
-  /// Document class from dart:mirrors.
-  ClassElement documentClass;
-  Element identicalFunction;
-  Element loadLibraryFunction;
-  Element functionApplyMethod;
-  Element intEnvironment;
-  Element boolEnvironment;
-  Element stringEnvironment;
-
-  fromEnvironment(String name) => null;
-
-  Element get currentElement => _currentElement;
-
-  String tryToString(object) {
-    try {
-      return object.toString();
-    } catch (_) {
-      return '<exception in toString()>';
-    }
-  }
-
-  /**
-   * Perform an operation, [f], returning the return value from [f].  If an
-   * error occurs then report it as having occurred during compilation of
-   * [element].  Can be nested.
-   */
-  withCurrentElement(Element element, f()) {
-    Element old = currentElement;
-    _currentElement = element;
-    try {
-      return f();
-    } on SpannableAssertionFailure catch (ex) {
-      if (!hasCrashed) {
-        reportAssertionFailure(ex);
-        pleaseReportCrash();
-      }
-      hasCrashed = true;
-      rethrow;
-    } on CompilerCancelledException catch (ex) {
-      rethrow;
-    } on StackOverflowError catch (ex) {
-      // We cannot report anything useful in this case, because we
-      // do not have enough stack space.
-      rethrow;
-    } catch (ex) {
-      if (hasCrashed) rethrow;
-      try {
-        unhandledExceptionOnElement(element);
-      } catch (doubleFault) {
-        // Ignoring exceptions in exception handling.
-      }
-      rethrow;
-    } finally {
-      _currentElement = old;
-    }
-  }
-
-  List<CompilerTask> tasks;
-  ScannerTask scanner;
-  DietParserTask dietParser;
-  ParserTask parser;
-  PatchParserTask patchParser;
-  LibraryLoaderTask libraryLoader;
-  ResolverTask resolver;
-  closureMapping.ClosureTask closureToClassMapper;
-  TypeCheckerTask checker;
-  IrBuilderTask irBuilder;
-  ti.TypesTask typesTask;
-  Backend backend;
-
-  GenericTask reuseLibraryTask;
-
-  /// The constant environment for the frontend interpretation of compile-time
-  /// constants.
-  ConstantEnvironment constants;
-
-  EnqueueTask enqueuer;
-  DeferredLoadTask deferredLoadTask;
-  MirrorUsageAnalyzerTask mirrorUsageAnalyzerTask;
-  DumpInfoTask dumpInfoTask;
-  String buildId;
-
-  /// A customizable filter that is applied to enqueued work items.
-  QueueFilter enqueuerFilter = new QueueFilter();
-
-  static const String MAIN = 'main';
-  static const String CALL_OPERATOR_NAME = 'call';
-  static const String NO_SUCH_METHOD = 'noSuchMethod';
-  static const int NO_SUCH_METHOD_ARG_COUNT = 1;
-  static const String CREATE_INVOCATION_MIRROR =
-      'createInvocationMirror';
-
-  static const String RUNTIME_TYPE = 'runtimeType';
-
-  static const String UNDETERMINED_BUILD_ID =
-      "build number could not be determined";
-
-  final Selector iteratorSelector =
-      new Selector.getter('iterator', null);
-  final Selector currentSelector =
-      new Selector.getter('current', null);
-  final Selector moveNextSelector =
-      new Selector.call('moveNext', null, 0);
-  final Selector noSuchMethodSelector = new Selector.call(
-      Compiler.NO_SUCH_METHOD, null, Compiler.NO_SUCH_METHOD_ARG_COUNT);
-  final Selector symbolValidatedConstructorSelector = new Selector.call(
-      'validated', null, 1);
-  final Selector fromEnvironmentSelector = new Selector.callConstructor(
-      'fromEnvironment', null, 2);
-
-  bool enabledNoSuchMethod = false;
-  bool enabledRuntimeType = false;
-  bool enabledFunctionApply = false;
-  bool enabledInvokeOn = false;
-  bool hasIsolateSupport = false;
-
-  Stopwatch progress;
-
-  bool get shouldPrintProgress {
-    return verbose && progress.elapsedMilliseconds > 500;
-  }
-
-  static const int PHASE_SCANNING = 0;
-  static const int PHASE_RESOLVING = 1;
-  static const int PHASE_DONE_RESOLVING = 2;
-  static const int PHASE_COMPILING = 3;
-  int phase;
-
-  bool compilationFailed = false;
-
-  bool hasCrashed = false;
-
-  /// Set by the backend if real reflection is detected in use of dart:mirrors.
-  bool disableTypeInferenceForMirrors = false;
-
-  Compiler({this.enableTypeAssertions: false,
-            this.enableUserAssertions: false,
-            this.trustTypeAnnotations: false,
-            this.enableConcreteTypeInference: false,
-            bool disableTypeInferenceFlag: false,
-            this.maxConcreteTypeSize: 5,
-            this.enableMinification: false,
-            this.preserveUris: false,
-            this.enableNativeLiveTypeAnalysis: false,
-            bool emitJavaScript: true,
-            bool dart2dartMultiFile: false,
-            bool generateSourceMap: true,
-            bool analyzeAllFlag: false,
-            bool analyzeOnly: false,
-            this.analyzeMain: false,
-            bool analyzeSignaturesOnly: false,
-            this.preserveComments: false,
-            this.verbose: false,
-            this.sourceMapUri: null,
-            this.outputUri: null,
-            this.buildId: UNDETERMINED_BUILD_ID,
-            this.terseDiagnostics: false,
-            this.dumpInfo: false,
-            this.showPackageWarnings: false,
-            this.useContentSecurityPolicy: false,
-            this.suppressWarnings: false,
-            bool hasIncrementalSupport: false,
-            api.CompilerOutputProvider outputProvider,
-            List<String> strips: const []})
-      : this.disableTypeInferenceFlag =
-          disableTypeInferenceFlag || !emitJavaScript,
-        this.analyzeOnly =
-            analyzeOnly || analyzeSignaturesOnly || analyzeAllFlag,
-        this.analyzeSignaturesOnly = analyzeSignaturesOnly,
-        this.analyzeAllFlag = analyzeAllFlag,
-        this.hasIncrementalSupport = hasIncrementalSupport,
-        cacheStrategy = new CacheStrategy(hasIncrementalSupport),
-        this.outputProvider = (outputProvider == null)
-            ? NullSink.outputProvider
-            : outputProvider {
-    if (hasIncrementalSupport) {
-      // TODO(ahe): This is too much. Any method from platform and package
-      // libraries can be inlined.
-      disableInlining = true;
-    }
-    world = new World(this);
-    types = new Types(this);
-    tracer = new Tracer(this, this.outputProvider);
-
-    if (verbose) {
-      progress = new Stopwatch()..start();
-    }
-
-    // TODO(johnniwinther): Separate the dependency tracking from the enqueueing
-    // for global dependencies.
-    globalDependencies =
-        new CodegenRegistry(this, new TreeElementMapping(null));
-
-    closureMapping.ClosureNamer closureNamer;
-    if (emitJavaScript) {
-      js_backend.JavaScriptBackend jsBackend =
-          new js_backend.JavaScriptBackend(this, generateSourceMap);
-      closureNamer = jsBackend.namer;
-      backend = jsBackend;
-    } else {
-      closureNamer = new closureMapping.ClosureNamer();
-      backend = new dart_backend.DartBackend(this, strips,
-                                             multiFile: dart2dartMultiFile);
-    }
-
-    tasks = [
-      libraryLoader = new LibraryLoaderTask(this),
-      scanner = new ScannerTask(this),
-      dietParser = new DietParserTask(this),
-      parser = new ParserTask(this),
-      patchParser = new PatchParserTask(this),
-      resolver = new ResolverTask(this, backend.constantCompilerTask),
-      closureToClassMapper = new closureMapping.ClosureTask(this, closureNamer),
-      checker = new TypeCheckerTask(this),
-      irBuilder = new IrBuilderTask(this),
-      typesTask = new ti.TypesTask(this),
-      constants = backend.constantCompilerTask,
-      deferredLoadTask = new DeferredLoadTask(this),
-      mirrorUsageAnalyzerTask = new MirrorUsageAnalyzerTask(this),
-      enqueuer = new EnqueueTask(this),
-      dumpInfoTask = new DumpInfoTask(this),
-      reuseLibraryTask = new GenericTask('Reuse library', this),
-    ];
-
-    tasks.addAll(backend.tasks);
-  }
-
-  Universe get resolverWorld => enqueuer.resolution.universe;
-  Universe get codegenWorld => enqueuer.codegen.universe;
-
-  bool get hasBuildId => buildId != UNDETERMINED_BUILD_ID;
-
-  bool get analyzeAll => analyzeAllFlag || compileAll;
-
-  bool get compileAll => false;
-
-  bool get disableTypeInference => disableTypeInferenceFlag;
-
-  int getNextFreeClassId() => nextFreeClassId++;
-
-  void unimplemented(Spannable spannable, String methodName) {
-    internalError(spannable, "$methodName not implemented.");
-  }
-
-  void internalError(Spannable node, reason) {
-    assembledCode = null; // Compilation failed. Make sure that we
-                          // don't return a bogus result.
-    String message = tryToString(reason);
-    reportDiagnosticInternal(
-        node, MessageKind.GENERIC, {'text': message}, api.Diagnostic.CRASH);
-    throw 'Internal Error: $message';
-  }
-
-  void unhandledExceptionOnElement(Element element) {
-    if (hasCrashed) return;
-    hasCrashed = true;
-    reportDiagnostic(element,
-                     MessageKind.COMPILER_CRASHED.message(),
-                     api.Diagnostic.CRASH);
-    pleaseReportCrash();
-  }
-
-  void pleaseReportCrash() {
-    print(MessageKind.PLEASE_REPORT_THE_CRASH.message({'buildId': buildId}));
-  }
-
-  SourceSpan spanFromSpannable(Spannable node) {
-    // TODO(johnniwinther): Disallow `node == null` ?
-    if (node == null) return null;
-    if (node == CURRENT_ELEMENT_SPANNABLE) {
-      node = currentElement;
-    } else if (node == NO_LOCATION_SPANNABLE) {
-      if (currentElement == null) return null;
-      node = currentElement;
-    }
-    if (node is SourceSpan) {
-      return node;
-    } else if (node is Node) {
-      return spanFromNode(node);
-    } else if (node is Token) {
-      return spanFromTokens(node, node);
-    } else if (node is HInstruction) {
-      return spanFromHInstruction(node);
-    } else if (node is Element) {
-      return spanFromElement(node);
-    } else if (node is MetadataAnnotation) {
-      Uri uri = node.annotatedElement.compilationUnit.script.readableUri;
-      return spanFromTokens(node.beginToken, node.endToken, uri);
-    } else if (node is Local) {
-      Local local = node;
-      return spanFromElement(local.executableContext);
-    } else {
-      throw 'No error location.';
-    }
-  }
-
-  Element _elementFromHInstruction(HInstruction instruction) {
-    return instruction.sourceElement is Element
-        ? instruction.sourceElement : null;
-  }
-
-  /// Finds the approximate [Element] for [node]. [currentElement] is used as
-  /// the default value.
-  Element elementFromSpannable(Spannable node) {
-    Element element;
-    if (node is Element) {
-      element = node;
-    } else if (node is HInstruction) {
-      element = _elementFromHInstruction(node);
-    } else if (node is MetadataAnnotation) {
-      element = node.annotatedElement;
-    }
-    return element != null ? element : currentElement;
-  }
-
-  void log(message) {
-    reportDiagnostic(null,
-        MessageKind.GENERIC.message({'text': '$message'}),
-        api.Diagnostic.VERBOSE_INFO);
-  }
-
-  Future<bool> run(Uri uri) {
-    totalCompileTime.start();
-
-    return new Future.sync(() => runCompiler(uri)).catchError((error) {
-      if (error is CompilerCancelledException) {
-        compilerWasCancelled = true;
-        log('Error: $error');
-        return false;
-      }
-
-      try {
-        if (!hasCrashed) {
-          hasCrashed = true;
-          if (error is SpannableAssertionFailure) {
-            reportAssertionFailure(error);
-          } else {
-            reportDiagnostic(new SourceSpan(uri, 0, 0),
-                             MessageKind.COMPILER_CRASHED.message(),
-                             api.Diagnostic.CRASH);
-          }
-          pleaseReportCrash();
-        }
-      } catch (doubleFault) {
-        // Ignoring exceptions in exception handling.
-      }
-      throw error;
-    }).whenComplete(() {
-      tracer.close();
-      totalCompileTime.stop();
-    }).then((_) {
-      return !compilationFailed;
-    });
-  }
-
-  /// This method is called immediately after the [LibraryElement] [library] has
-  /// been created.
-  ///
-  /// Use this callback method to store references to specific libraries.
-  /// Note that [library] has not been scanned yet, nor has its imports/exports
-  /// been resolved.
-  void onLibraryCreated(LibraryElement library) {
-    Uri uri = library.canonicalUri;
-    if (uri == DART_CORE) {
-      coreLibrary = library;
-    } else if (uri == DART_NATIVE_TYPED_DATA) {
-      typedDataLibrary = library;
-    } else if (uri == DART_MIRRORS) {
-      mirrorsLibrary = library;
-    }
-    backend.onLibraryCreated(library);
-  }
-
-  /// This method is called immediately after the [library] and its parts have
-  /// been scanned.
-  ///
-  /// Use this callback method to store references to specific member declared
-  /// in certain libraries. Note that [library] has not been patched yet, nor
-  /// has its imports/exports been resolved.
-  ///
-  /// Use [loader] to register the creation and scanning of a patch library
-  /// for [library].
-  Future onLibraryScanned(LibraryElement library, LibraryLoader loader) {
-    Uri uri = library.canonicalUri;
-    if (uri == DART_CORE) {
-      initializeCoreClasses();
-      identicalFunction = coreLibrary.find('identical');
-    } else if (uri == DART_INTERNAL) {
-      symbolImplementationClass = findRequiredElement(library, 'Symbol');
-    } else if (uri == DART_MIRRORS) {
-      mirrorSystemClass = findRequiredElement(library, 'MirrorSystem');
-      mirrorsUsedClass = findRequiredElement(library, 'MirrorsUsed');
-    } else if (uri == DART_ASYNC) {
-      deferredLibraryClass = findRequiredElement(library, 'DeferredLibrary');
-    } else if (uri == DART_NATIVE_TYPED_DATA) {
-      typedDataClass = findRequiredElement(library, 'NativeTypedData');
-    } else if (uri == js_backend.JavaScriptBackend.DART_JS_HELPER) {
-      nativeAnnotationClass = findRequiredElement(library, 'Native');
-    }
-    return backend.onLibraryScanned(library, loader);
-  }
-
-  /// This method is called when all new libraries loaded through
-  /// [LibraryLoader.loadLibrary] has been loaded and their imports/exports
-  /// have been computed.
-  ///
-  /// [loadedLibraries] contains the newly loaded libraries.
-  ///
-  /// The method returns a [Future] allowing for the loading of additional
-  /// libraries.
-  Future onLibrariesLoaded(Map<Uri, LibraryElement> loadedLibraries) {
-    return new Future.sync(() {
-      if (!loadedLibraries.containsKey(DART_CORE)) return new Future.value();
-
-      functionClass.ensureResolved(this);
-      functionApplyMethod = functionClass.lookupLocalMember('apply');
-
-      proxyConstant =
-          resolver.constantCompiler.compileConstant(
-              coreLibrary.find('proxy')).value;
-
-      // TODO(johnniwinther): Move this to the JavaScript backend.
-      LibraryElement jsHelperLibrary =
-          loadedLibraries[js_backend.JavaScriptBackend.DART_JS_HELPER];
-      if (jsHelperLibrary != null) {
-        patchConstant = resolver.constantCompiler.compileConstant(
-            jsHelperLibrary.find('patch')).value;
-      }
-
-      if (preserveComments) {
-        return libraryLoader.loadLibrary(DART_MIRRORS)
-            .then((LibraryElement libraryElement) {
-          documentClass = libraryElement.find('Comment');
-        });
-      }
-    }).then((_) => backend.onLibrariesLoaded(loadedLibraries));
-  }
-
-  Element findRequiredElement(LibraryElement library, String name) {
-    var element = library.find(name);
-    if (element == null) {
-      internalError(library,
-          "The library '${library.canonicalUri}' does not contain required "
-          "element: '$name'.");
-      }
-    return element;
-  }
-
-  void onClassResolved(ClassElement cls) {
-    if (mirrorSystemClass == cls) {
-      mirrorSystemGetNameFunction =
-        cls.lookupLocalMember('getName');
-    } else if (symbolClass == cls) {
-      symbolConstructor = cls.constructors.head;
-    } else if (symbolImplementationClass == cls) {
-      symbolValidatedConstructor = symbolImplementationClass.lookupConstructor(
-          symbolValidatedConstructorSelector);
-    } else if (mirrorsUsedClass == cls) {
-      mirrorsUsedConstructor = cls.constructors.head;
-    } else if (intClass == cls) {
-      intEnvironment = intClass.lookupConstructor(fromEnvironmentSelector);
-    } else if (stringClass == cls) {
-      stringEnvironment =
-          stringClass.lookupConstructor(fromEnvironmentSelector);
-    } else if (boolClass == cls) {
-      boolEnvironment = boolClass.lookupConstructor(fromEnvironmentSelector);
-    }
-  }
-
-  void initializeCoreClasses() {
-    final List missingCoreClasses = [];
-    ClassElement lookupCoreClass(String name) {
-      ClassElement result = coreLibrary.find(name);
-      if (result == null) {
-        missingCoreClasses.add(name);
-      }
-      return result;
-    }
-    objectClass = lookupCoreClass('Object');
-    boolClass = lookupCoreClass('bool');
-    numClass = lookupCoreClass('num');
-    intClass = lookupCoreClass('int');
-    doubleClass = lookupCoreClass('double');
-    stringClass = lookupCoreClass('String');
-    functionClass = lookupCoreClass('Function');
-    listClass = lookupCoreClass('List');
-    typeClass = lookupCoreClass('Type');
-    mapClass = lookupCoreClass('Map');
-    nullClass = lookupCoreClass('Null');
-    stackTraceClass = lookupCoreClass('StackTrace');
-    symbolClass = lookupCoreClass('Symbol');
-    if (!missingCoreClasses.isEmpty) {
-      internalError(coreLibrary,
-          'dart:core library does not contain required classes: '
-          '$missingCoreClasses');
-    }
-  }
-
-  Element _unnamedListConstructor;
-  Element get unnamedListConstructor {
-    if (_unnamedListConstructor != null) return _unnamedListConstructor;
-    Selector callConstructor = new Selector.callConstructor(
-        "", listClass.library);
-    return _unnamedListConstructor =
-        listClass.lookupConstructor(callConstructor);
-  }
-
-  Element _filledListConstructor;
-  Element get filledListConstructor {
-    if (_filledListConstructor != null) return _filledListConstructor;
-    Selector callConstructor = new Selector.callConstructor(
-        "filled", listClass.library);
-    return _filledListConstructor =
-        listClass.lookupConstructor(callConstructor);
-  }
-
-  /**
-   * Get an [Uri] pointing to a patch for the dart: library with
-   * the given path. Returns null if there is no patch.
-   */
-  Uri resolvePatchUri(String dartLibraryPath);
-
-  Future runCompiler(Uri uri) {
-    // TODO(ahe): This prevents memory leaks when invoking the compiler
-    // multiple times. Implement a better mechanism where we can store
-    // such caches in the compiler and get access to them through a
-    // suitably maintained static reference to the current compiler.
-    StringToken.canonicalizedSubstrings.clear();
-    Selector.canonicalizedValues.clear();
-    TypedSelector.canonicalizedValues.clear();
-
-    assert(uri != null || analyzeOnly || hasIncrementalSupport);
-    return new Future.sync(() {
-      if (librariesToAnalyzeWhenRun != null) {
-        return Future.forEach(librariesToAnalyzeWhenRun, (libraryUri) {
-          log('Analyzing $libraryUri ($buildId)');
-          return libraryLoader.loadLibrary(libraryUri);
-        });
-      }
-    }).then((_) {
-      if (uri != null) {
-        if (analyzeOnly) {
-          log('Analyzing $uri ($buildId)');
-        } else {
-          log('Compiling $uri ($buildId)');
-        }
-        return libraryLoader.loadLibrary(uri).then((LibraryElement library) {
-          mainApp = library;
-        });
-      }
-    }).then((_) {
-      if (!compilationFailed) {
-        // TODO(johnniwinther): Reenable analysis of programs with load failures
-        // when these are handled as erroneous libraries/compilation units.
-        compileLoadedLibraries();
-      }
-    });
-  }
-
-  void computeMain() {
-    if (mainApp == null) return;
-
-    Element main = mainApp.findExported(MAIN);
-    ErroneousElement errorElement = null;
-    if (main == null) {
-      if (analyzeOnly) {
-        if (!analyzeAll) {
-          errorElement = new ErroneousElementX(
-              MessageKind.CONSIDER_ANALYZE_ALL, {'main': MAIN}, MAIN, mainApp);
-        }
-      } else {
-        // Compilation requires a main method.
-        errorElement = new ErroneousElementX(
-            MessageKind.MISSING_MAIN, {'main': MAIN}, MAIN, mainApp);
-      }
-      mainFunction = backend.helperForMissingMain();
-    } else if (main.isErroneous && main.isSynthesized) {
-      if (main is ErroneousElement) {
-        errorElement = main;
-      } else {
-        internalError(main, 'Problem with $MAIN.');
-      }
-      mainFunction = backend.helperForBadMain();
-    } else if (!main.isFunction) {
-      errorElement = new ErroneousElementX(
-          MessageKind.MAIN_NOT_A_FUNCTION, {'main': MAIN}, MAIN, main);
-      mainFunction = backend.helperForBadMain();
-    } else {
-      mainFunction = main;
-      FunctionSignature parameters = mainFunction.computeSignature(this);
-      if (parameters.requiredParameterCount > 2) {
-        int index = 0;
-        parameters.orderedForEachParameter((Element parameter) {
-          if (index++ < 2) return;
-          errorElement = new ErroneousElementX(
-              MessageKind.MAIN_WITH_EXTRA_PARAMETER, {'main': MAIN}, MAIN,
-              parameter);
-          mainFunction = backend.helperForMainArity();
-          // Don't warn about main not being used:
-          enqueuer.resolution.registerStaticUse(main);
-        });
-      }
-    }
-    if (mainFunction == null) {
-      if (errorElement == null && !analyzeOnly && !analyzeAll) {
-        internalError(mainApp, "Problem with '$MAIN'.");
-      } else {
-        mainFunction = errorElement;
-      }
-    }
-    if (errorElement != null && errorElement.isSynthesized) {
-      reportWarning(
-          errorElement, errorElement.messageKind,
-          errorElement.messageArguments);
-    }
-  }
-
-  /// Performs the compilation when all libraries have been loaded.
-  void compileLoadedLibraries() {
-    computeMain();
-
-    mirrorUsageAnalyzerTask.analyzeUsage(mainApp);
-
-    // In order to see if a library is deferred, we must compute the
-    // compile-time constants that are metadata.  This means adding
-    // something to the resolution queue.  So we cannot wait with
-    // this until after the resolution queue is processed.
-    deferredLoadTask.ensureMetadataResolved(this);
-
-    phase = PHASE_RESOLVING;
-    if (analyzeAll) {
-      libraryLoader.libraries.forEach((LibraryElement library) {
-        log('Enqueuing ${library.canonicalUri}');
-        fullyEnqueueLibrary(library, enqueuer.resolution);
-      });
-    } else if (analyzeMain && mainApp != null) {
-      fullyEnqueueLibrary(mainApp, enqueuer.resolution);
-    }
-    // Elements required by enqueueHelpers are global dependencies
-    // that are not pulled in by a particular element.
-    backend.enqueueHelpers(enqueuer.resolution, globalDependencies);
-    resolveLibraryMetadata();
-    log('Resolving...');
-    processQueue(enqueuer.resolution, mainFunction);
-    enqueuer.resolution.logSummary(log);
-
-    if (compilationFailed) return;
-    if (!showPackageWarnings && !suppressWarnings) {
-      suppressedWarnings.forEach((Uri uri, SuppressionInfo info) {
-        MessageKind kind = MessageKind.HIDDEN_WARNINGS_HINTS;
-        if (info.warnings == 0) {
-          kind = MessageKind.HIDDEN_HINTS;
-        } else if (info.hints == 0) {
-          kind = MessageKind.HIDDEN_WARNINGS;
-        }
-        reportDiagnostic(null,
-            kind.message({'warnings': info.warnings,
-                          'hints': info.hints,
-                          'uri': uri},
-                         terseDiagnostics),
-            api.Diagnostic.HINT);
-      });
-    }
-    if (analyzeOnly) {
-      if (!analyzeAll) {
-        // No point in reporting unused code when [analyzeAll] is true: all
-        // code is artificially used.
-        reportUnusedCode();
-      }
-      return;
-    }
-    assert(mainFunction != null);
-    phase = PHASE_DONE_RESOLVING;
-
-    world.populate();
-    // Compute whole-program-knowledge that the backend needs. (This might
-    // require the information computed in [world.populate].)
-    backend.onResolutionComplete();
-
-    deferredLoadTask.onResolutionComplete(mainFunction);
-
-    log('Building IR...');
-    irBuilder.buildNodes();
-
-    log('Inferring types...');
-    typesTask.onResolutionComplete(mainFunction);
-
-    if (stopAfterTypeInference) return;
-
-    log('Compiling...');
-    phase = PHASE_COMPILING;
-    // TODO(johnniwinther): Move these to [CodegenEnqueuer].
-    if (hasIsolateSupport) {
-      backend.enableIsolateSupport(enqueuer.codegen);
-    }
-    if (enabledNoSuchMethod) {
-      backend.enableNoSuchMethod(null, enqueuer.codegen);
-    }
-    if (compileAll) {
-      libraryLoader.libraries.forEach((LibraryElement library) {
-        fullyEnqueueLibrary(library, enqueuer.codegen);
-      });
-    }
-    processQueue(enqueuer.codegen, mainFunction);
-    enqueuer.codegen.logSummary(log);
-
-    if (compilationFailed) return;
-
-    backend.assembleProgram();
-
-    if (dumpInfo) {
-      dumpInfoTask.dumpInfo();
-    }
-
-    checkQueues();
-
-    if (compilationFailed) {
-      assembledCode = null; // Signals failure.
-    }
-  }
-
-  void fullyEnqueueLibrary(LibraryElement library, Enqueuer world) {
-    void enqueueAll(Element element) {
-      fullyEnqueueTopLevelElement(element, world);
-    }
-    library.implementation.forEachLocalMember(enqueueAll);
-  }
-
-  void fullyEnqueueTopLevelElement(Element element, Enqueuer world) {
-    if (element.isClass) {
-      ClassElement cls = element;
-      cls.ensureResolved(this);
-      cls.forEachLocalMember(enqueuer.resolution.addToWorkList);
-      world.registerInstantiatedClass(element, globalDependencies);
-    } else {
-      world.addToWorkList(element);
-    }
-  }
-
-  // Resolves metadata on library elements.  This is necessary in order to
-  // resolve metadata classes referenced only from metadata on library tags.
-  // TODO(ahe): Figure out how to do this lazily.
-  void resolveLibraryMetadata() {
-    for (LibraryElement library in libraryLoader.libraries) {
-      if (library.metadata != null) {
-        for (MetadataAnnotation metadata in library.metadata) {
-          metadata.ensureResolved(this);
-        }
-      }
-    }
-  }
-
-  void processQueue(Enqueuer world, Element main) {
-    world.nativeEnqueuer.processNativeClasses(libraryLoader.libraries);
-    if (main != null && !main.isErroneous) {
-      FunctionElement mainMethod = main;
-      if (mainMethod.computeSignature(this).parameterCount != 0) {
-        // The first argument could be a list of strings.
-        world.registerInstantiatedClass(
-            backend.listImplementation, globalDependencies);
-        world.registerInstantiatedClass(
-            backend.stringImplementation, globalDependencies);
-
-        backend.registerMainHasArguments(world);
-      }
-      world.addToWorkList(main);
-    }
-    if (verbose) {
-      progress.reset();
-    }
-    world.forEach((WorkItem work) {
-      withCurrentElement(work.element, () => work.run(this, world));
-    });
-    world.queueIsClosed = true;
-    if (compilationFailed) return;
-    assert(world.checkNoEnqueuedInvokedInstanceMethods());
-  }
-
-  /**
-   * Perform various checks of the queues. This includes checking that
-   * the queues are empty (nothing was added after we stopped
-   * processing the queues). Also compute the number of methods that
-   * were resolved, but not compiled (aka excess resolution).
-   */
-  checkQueues() {
-    for (Enqueuer world in [enqueuer.resolution, enqueuer.codegen]) {
-      world.forEach((WorkItem work) {
-        internalError(work.element, "Work list is not empty.");
-      });
-    }
-    if (!REPORT_EXCESS_RESOLUTION) return;
-    var resolved = new Set.from(enqueuer.resolution.resolvedElements);
-    for (Element e in enqueuer.codegen.generatedCode.keys) {
-      resolved.remove(e);
-    }
-    for (Element e in new Set.from(resolved)) {
-      if (e.isClass ||
-          e.isField ||
-          e.isTypeVariable ||
-          e.isTypedef ||
-          identical(e.kind, ElementKind.ABSTRACT_FIELD)) {
-        resolved.remove(e);
-      }
-      if (identical(e.kind, ElementKind.GENERATIVE_CONSTRUCTOR)) {
-        ClassElement enclosingClass = e.enclosingClass;
-        resolved.remove(e);
-
-      }
-      if (backend.isBackendLibrary(e.library)) {
-        resolved.remove(e);
-      }
-    }
-    log('Excess resolution work: ${resolved.length}.');
-    for (Element e in resolved) {
-      reportWarning(e,
-          MessageKind.GENERIC,
-          {'text': 'Warning: $e resolved but not compiled.'});
-    }
-  }
-
-  void analyzeElement(Element element) {
-    assert(invariant(element,
-           element.impliesType ||
-           element.isField ||
-           element.isFunction ||
-           element.isGenerativeConstructor ||
-           element.isGetter ||
-           element.isSetter,
-           message: 'Unexpected element kind: ${element.kind}'));
-    assert(invariant(element, element is AnalyzableElement,
-        message: 'Element $element is not analyzable.'));
-    assert(invariant(element, element.isDeclaration));
-    ResolutionEnqueuer world = enqueuer.resolution;
-    if (world.hasBeenResolved(element)) return;
-    assert(parser != null);
-    Node tree = parser.parse(element);
-    assert(invariant(element, !element.isSynthesized || tree == null));
-    TreeElements elements = resolver.resolve(element);
-    if (elements != null) {
-      if (tree != null && !analyzeSignaturesOnly &&
-          !suppressWarnings) {
-        // Only analyze nodes with a corresponding [TreeElements].
-        checker.check(elements);
-      }
-      world.registerResolvedElement(element);
-    }
-  }
-
-  void analyze(ResolutionWorkItem work, ResolutionEnqueuer world) {
-    assert(invariant(work.element, identical(world, enqueuer.resolution)));
-    assert(invariant(work.element, !work.isAnalyzed(),
-        message: 'Element ${work.element} has already been analyzed'));
-    if (shouldPrintProgress) {
-      // TODO(ahe): Add structured diagnostics to the compiler API and
-      // use it to separate this from the --verbose option.
-      if (phase == PHASE_RESOLVING) {
-        log('Resolved ${enqueuer.resolution.resolvedElements.length} '
-            'elements.');
-        progress.reset();
-      }
-    }
-    AstElement element = work.element;
-    if (world.hasBeenResolved(element)) return;
-    analyzeElement(element);
-    backend.onElementResolved(element, element.resolvedAst.elements);
-  }
-
-  void codegen(CodegenWorkItem work, CodegenEnqueuer world) {
-    assert(invariant(work.element, identical(world, enqueuer.codegen)));
-    if (shouldPrintProgress) {
-      // TODO(ahe): Add structured diagnostics to the compiler API and
-      // use it to separate this from the --verbose option.
-      log('Compiled ${enqueuer.codegen.generatedCode.length} methods.');
-      progress.reset();
-    }
-    backend.codegen(work);
-  }
-
-  void reportError(Spannable node,
-                   MessageKind messageKind,
-                   [Map arguments = const {}]) {
-    reportDiagnosticInternal(
-        node, messageKind, arguments, api.Diagnostic.ERROR);
-  }
-
-  /**
-   * Reports an error and then aborts the compiler. Avoid using this method.
-   *
-   * In order to support incremental compilation, it is preferable to use
-   * [reportError]. However, care must be taken to leave the compiler in a
-   * consistent state, for example, by creating synthetic erroneous objects.
-   *
-   * If there's absolutely no way to leave the compiler in a consistent state,
-   * calling this method is preferred as it will set [compilerWasCancelled] to
-   * true which alerts the incremental compiler to discard all state and start
-   * a new compiler. Throwing an exception is also better, as this will set
-   * [hasCrashed] which the incremental compiler also listens too (but don't
-   * throw exceptions, it creates a really bad user experience).
-   *
-   * In any case, calling this method is a last resort, as it essentially
-   * breaks the user experience of the incremental compiler. The purpose of the
-   * incremental compiler is to improve developer productivity. Developers
-   * frequently make mistakes, so syntax errors and spelling errors are
-   * considered normal to the incremental compiler.
-   */
-  void reportFatalError(Spannable node, MessageKind messageKind,
-                        [Map arguments = const {}]) {
-    reportError(node, messageKind, arguments);
-    // TODO(ahe): Make this only abort the current method.
-    throw new CompilerCancelledException(
-        'Error: Cannot continue due to previous error.');
-  }
-
-  void reportWarning(Spannable node, MessageKind messageKind,
-                     [Map arguments = const {}]) {
-    reportDiagnosticInternal(
-        node, messageKind, arguments, api.Diagnostic.WARNING);
-  }
-
-  void reportInfo(Spannable node, MessageKind messageKind,
-                  [Map arguments = const {}]) {
-    reportDiagnosticInternal(node, messageKind, arguments, api.Diagnostic.INFO);
-  }
-
-  void reportHint(Spannable node, MessageKind messageKind,
-                  [Map arguments = const {}]) {
-    reportDiagnosticInternal(node, messageKind, arguments, api.Diagnostic.HINT);
-  }
-
-  void reportDiagnosticInternal(Spannable node,
-                                MessageKind messageKind,
-                                Map arguments,
-                                api.Diagnostic kind) {
-    if (!showPackageWarnings && node != NO_LOCATION_SPANNABLE) {
-      switch (kind) {
-      case api.Diagnostic.WARNING:
-      case api.Diagnostic.HINT:
-        Element element = elementFromSpannable(node);
-        if (!inUserCode(element, assumeInUserCode: true)) {
-          Uri uri = getCanonicalUri(element);
-          SuppressionInfo info =
-              suppressedWarnings.putIfAbsent(uri, () => new SuppressionInfo());
-          if (kind == api.Diagnostic.WARNING) {
-            info.warnings++;
-          } else {
-            info.hints++;
-          }
-          lastDiagnosticWasFiltered = true;
-          return;
-        }
-        break;
-      case api.Diagnostic.INFO:
-        if (lastDiagnosticWasFiltered) {
-          return;
-        }
-        break;
-      }
-    }
-    lastDiagnosticWasFiltered = false;
-    reportDiagnostic(
-        node, messageKind.message(arguments, terseDiagnostics), kind);
-  }
-
-  void reportDiagnostic(Spannable span,
-                        Message message,
-                        api.Diagnostic kind);
-
-  void reportAssertionFailure(SpannableAssertionFailure ex) {
-    String message = (ex.message != null) ? tryToString(ex.message)
-                                          : tryToString(ex);
-    SourceSpan span = spanFromSpannable(ex.node);
-    reportDiagnosticInternal(
-        ex.node, MessageKind.GENERIC, {'text': message}, api.Diagnostic.CRASH);
-  }
-
-  SourceSpan spanFromTokens(Token begin, Token end, [Uri uri]) {
-    if (begin == null || end == null) {
-      // TODO(ahe): We can almost always do better. Often it is only
-      // end that is null. Otherwise, we probably know the current
-      // URI.
-      throw 'Cannot find tokens to produce error message.';
-    }
-    if (uri == null && currentElement != null) {
-      uri = currentElement.compilationUnit.script.readableUri;
-    }
-    return SourceSpan.withCharacterOffsets(begin, end,
-      (beginOffset, endOffset) => new SourceSpan(uri, beginOffset, endOffset));
-  }
-
-  SourceSpan spanFromNode(Node node) {
-    return spanFromTokens(node.getBeginToken(), node.getEndToken());
-  }
-
-  SourceSpan spanFromElement(Element element) {
-    while (element != null && element.isSynthesized) {
-      element = element.enclosingElement;
-    }
-    if (element != null &&
-        element.position == null &&
-        !element.isLibrary &&
-        !element.isCompilationUnit) {
-      // Sometimes, the backend fakes up elements that have no
-      // position. So we use the enclosing element instead. It is
-      // not a good error location, but cancel really is "internal
-      // error" or "not implemented yet", so the vicinity is good
-      // enough for now.
-      element = element.enclosingElement;
-      // TODO(ahe): I plan to overhaul this infrastructure anyways.
-    }
-    if (element == null) {
-      element = currentElement;
-    }
-    Token position = element.position;
-    Uri uri = element.compilationUnit.script.readableUri;
-    return (position == null)
-        ? new SourceSpan(uri, 0, 0)
-        : spanFromTokens(position, position, uri);
-  }
-
-  SourceSpan spanFromHInstruction(HInstruction instruction) {
-    Element element = _elementFromHInstruction(instruction);
-    if (element == null) element = currentElement;
-    var position = instruction.sourcePosition;
-    if (position == null) return spanFromElement(element);
-    Token token = position.token;
-    if (token == null) return spanFromElement(element);
-    Uri uri = element.compilationUnit.script.readableUri;
-    return spanFromTokens(token, token, uri);
-  }
-
-  /**
-   * Translates the [resolvedUri] into a readable URI.
-   *
-   * The [importingLibrary] holds the library importing [resolvedUri] or
-   * [:null:] if [resolvedUri] is loaded as the main library. The
-   * [importingLibrary] is used to grant access to internal libraries from
-   * platform libraries and patch libraries.
-   *
-   * If the [resolvedUri] is not accessible from [importingLibrary], this method
-   * is responsible for reporting errors.
-   *
-   * See [LibraryLoader] for terminology on URIs.
-   */
-  Uri translateResolvedUri(LibraryElement importingLibrary,
-                           Uri resolvedUri, Node node) {
-    unimplemented(importingLibrary, 'Compiler.translateResolvedUri');
-    return null;
-  }
-
-  /**
-   * Reads the script specified by the [readableUri].
-   *
-   * See [LibraryLoader] for terminology on URIs.
-   */
-  Future<Script> readScript(Spannable node, Uri readableUri) {
-    unimplemented(node, 'Compiler.readScript');
-    return null;
-  }
-
-  Element lookupElementIn(ScopeContainerElement container, String name) {
-    Element element = container.localLookup(name);
-    if (element == null) {
-      throw 'Could not find $name in $container';
-    }
-    return element;
-  }
-
-  bool get isMockCompilation => false;
-
-  Token processAndStripComments(Token currentToken) {
-    Token firstToken = currentToken;
-    Token prevToken;
-    while (currentToken.kind != EOF_TOKEN) {
-      if (identical(currentToken.kind, COMMENT_TOKEN)) {
-        Token firstCommentToken = currentToken;
-        while (identical(currentToken.kind, COMMENT_TOKEN)) {
-          currentToken = currentToken.next;
-        }
-        commentMap[currentToken] = firstCommentToken;
-        if (prevToken == null) {
-          firstToken = currentToken;
-        } else {
-          prevToken.next = currentToken;
-        }
-      }
-      prevToken = currentToken;
-      currentToken = currentToken.next;
-    }
-    return firstToken;
-  }
-
-  void reportUnusedCode() {
-    void checkLive(member) {
-      if (member.isFunction) {
-        if (!enqueuer.resolution.hasBeenResolved(member)) {
-          reportHint(member, MessageKind.UNUSED_METHOD,
-                     {'name': member.name});
-        }
-      } else if (member.isClass) {
-        if (!member.isResolved) {
-          reportHint(member, MessageKind.UNUSED_CLASS,
-                     {'name': member.name});
-        } else {
-          member.forEachLocalMember(checkLive);
-        }
-      } else if (member.isTypedef) {
-        if (!member.isResolved) {
-          reportHint(member, MessageKind.UNUSED_TYPEDEF,
-                     {'name': member.name});
-        }
-      }
-    }
-    libraryLoader.libraries.forEach((LibraryElement library) {
-      // TODO(ahe): Implement better heuristics to discover entry points of
-      // packages and use that to discover unused implementation details in
-      // packages.
-      if (library.isPlatformLibrary || library.isPackageLibrary) return;
-      library.compilationUnits.forEach((unit) {
-        unit.forEachLocalMember(checkLive);
-      });
-    });
-  }
-
-  /// Helper for determining whether the current element is declared within
-  /// 'user code'.
-  ///
-  /// See [inUserCode] for what defines 'user code'.
-  bool currentlyInUserCode() {
-    return inUserCode(currentElement);
-  }
-
-  /// Helper for determining whether [element] is declared within 'user code'.
-  ///
-  /// What constitutes 'user code' is defined by the URI(s) provided by the
-  /// entry point(s) of compilation or analysis:
-  ///
-  /// If an entrypoint URI uses the 'package' scheme then every library from
-  /// that same package is considered to be in user code. For instance, if
-  /// an entry point URI is 'package:foo/bar.dart' then every library whose
-  /// canonical URI starts with 'package:foo/' is in user code.
-  ///
-  /// If an entrypoint URI uses another scheme than 'package' then every library
-  /// with that scheme is in user code. For instance, an entry point URI is
-  /// 'file:///foo.dart' then every library whose canonical URI scheme is
-  /// 'file' is in user code.
-  ///
-  /// If [assumeInUserCode] is `true`, [element] is assumed to be in user code
-  /// if no entrypoints have been set.
-  bool inUserCode(Element element, {bool assumeInUserCode: false}) {
-    List<Uri> entrypoints = <Uri>[];
-    if (mainApp != null) {
-      entrypoints.add(mainApp.canonicalUri);
-    }
-    if (librariesToAnalyzeWhenRun != null) {
-      entrypoints.addAll(librariesToAnalyzeWhenRun);
-    }
-    if (entrypoints.isEmpty && assumeInUserCode) {
-      // Assume in user code since [mainApp] has not been set yet.
-      return true;
-    }
-    if (element == null) return false;
-    Uri libraryUri = element.library.canonicalUri;
-    if (libraryUri.scheme == 'package') {
-      for (Uri uri in entrypoints) {
-        if (uri.scheme != 'package') continue;
-        int slashPos = libraryUri.path.indexOf('/');
-        if (slashPos != -1) {
-          String packageName = libraryUri.path.substring(0, slashPos + 1);
-          if (uri.path.startsWith(packageName)) {
-            return true;
-          }
-        } else {
-          if (libraryUri.path == uri.path) {
-            return true;
-          }
-        }
-      }
-    } else {
-      for (Uri uri in entrypoints) {
-        if (libraryUri.scheme == uri.scheme) return true;
-      }
-    }
-    return false;
-  }
-
-  /// Return a canonical URI for the source of [element].
-  ///
-  /// For a package library with canonical URI 'package:foo/bar/baz.dart' the
-  /// return URI is 'package:foo'. For non-package libraries the returned URI is
-  /// the canonical URI of the library itself.
-  Uri getCanonicalUri(Element element) {
-    if (element == null) return null;
-    Uri libraryUri = element.library.canonicalUri;
-    if (libraryUri.scheme == 'package') {
-      int slashPos = libraryUri.path.indexOf('/');
-      if (slashPos != -1) {
-        String packageName = libraryUri.path.substring(0, slashPos);
-        return new Uri(scheme: 'package', path: packageName);
-      }
-    }
-    return libraryUri;
-  }
-
-  void diagnoseCrashInUserCode(String message, exception, stackTrace) {
-    // Overridden by Compiler in apiimpl.dart.
-  }
-
-  void forgetElement(Element element) {
-    enqueuer.forgetElement(element);
-    if (element is MemberElement) {
-      for (Element closure in element.nestedClosures) {
-        // TODO(ahe): It would be nice to reuse names of nested closures.
-        closureToClassMapper.forgetElement(closure);
-      }
-    }
-    backend.forgetElement(element);
-  }
-}
-
-class CompilerTask {
-  final Compiler compiler;
-  final Stopwatch watch;
-  UserTag profilerTag;
-
-  CompilerTask(Compiler compiler)
-      : this.compiler = compiler,
-        watch = (compiler.verbose) ? new Stopwatch() : null;
-
-  String get name => 'Unknown task';
-  int get timing => (watch != null) ? watch.elapsedMilliseconds : 0;
-
-  int get timingMicroseconds => (watch != null) ? watch.elapsedMicroseconds : 0;
-
-  UserTag getProfilerTag() {
-    if (profilerTag == null) profilerTag = new UserTag(name);
-    return profilerTag;
-  }
-
-  measure(action()) {
-    // In verbose mode when watch != null.
-    if (watch == null) return action();
-    CompilerTask previous = compiler.measuredTask;
-    if (identical(this, previous)) return action();
-    compiler.measuredTask = this;
-    if (previous != null) previous.watch.stop();
-    watch.start();
-    UserTag oldTag = getProfilerTag().makeCurrent();
-    try {
-      return action();
-    } finally {
-      watch.stop();
-      oldTag.makeCurrent();
-      if (previous != null) previous.watch.start();
-      compiler.measuredTask = previous;
-    }
-  }
-
-  measureElement(Element element, action()) {
-    compiler.withCurrentElement(element, () => measure(action));
-  }
-}
-
-class CompilerCancelledException implements Exception {
-  final String reason;
-  CompilerCancelledException(this.reason);
-
-  String toString() {
-    String banner = 'compiler cancelled';
-    return (reason != null) ? '$banner: $reason' : '$banner';
-  }
-}
-
-class SourceSpan implements Spannable {
-  final Uri uri;
-  final int begin;
-  final int end;
-
-  const SourceSpan(this.uri, this.begin, this.end);
-
-  static withCharacterOffsets(Token begin, Token end,
-                     f(int beginOffset, int endOffset)) {
-    final beginOffset = begin.charOffset;
-    final endOffset = end.charOffset + end.charCount;
-
-    // [begin] and [end] might be the same for the same empty token. This
-    // happens for instance when scanning '$$'.
-    assert(endOffset >= beginOffset);
-    return f(beginOffset, endOffset);
-  }
-
-  String toString() => 'SourceSpan($uri, $begin, $end)';
-}
-
-/// Flag that can be used in assertions to assert that a code path is only
-/// executed as part of development.
-///
-/// This flag is automatically set to true if helper methods like, [debugPrint],
-/// [debugWrapPrint], [trace], and [reportHere] are called.
-bool DEBUG_MODE = false;
-
-/// Assert that [DEBUG_MODE] is `true` and provide [message] as part of the
-/// error message.
-assertDebugMode(String message) {
-  assert(invariant(NO_LOCATION_SPANNABLE, DEBUG_MODE,
-      message: 'Debug mode is not enabled: $message'));
-}
-
-/**
- * Throws a [SpannableAssertionFailure] if [condition] is
- * [:false:]. [condition] must be either a [:bool:] or a no-arg
- * function returning a [:bool:].
- *
- * Use this method to provide better information for assertion by calling
- * [invariant] as the argument to an [:assert:] statement:
- *
- *     assert(invariant(position, isValid));
- *
- * [spannable] must be non-null and will be used to provide positional
- * information in the generated error message.
- */
-bool invariant(Spannable spannable, var condition, {var message: null}) {
-  // TODO(johnniwinther): Use [spannable] and [message] to provide better
-  // information on assertion errors.
-  if (spannable == null) {
-    throw new SpannableAssertionFailure(CURRENT_ELEMENT_SPANNABLE,
-        "Spannable was null for invariant. Use CURRENT_ELEMENT_SPANNABLE.");
-  }
-  if (condition is Function){
-    condition = condition();
-  }
-  if (!condition) {
-    if (message is Function) {
-      message = message();
-    }
-    throw new SpannableAssertionFailure(spannable, message);
-  }
-  return true;
-}
-
-/// Returns `true` when [s] is private if used as an identifier.
-bool isPrivateName(String s) => !s.isEmpty && s.codeUnitAt(0) == $_;
-
-/// A sink that drains into /dev/null.
-class NullSink implements EventSink<String> {
-  final String name;
-
-  NullSink(this.name);
-
-  add(String value) {}
-
-  void addError(Object error, [StackTrace stackTrace]) {}
-
-  void close() {}
-
-  toString() => name;
-
-  /// Convenience method for getting an [api.CompilerOutputProvider].
-  static NullSink outputProvider(String name, String extension) {
-    return new NullSink('$name.$extension');
-  }
-}
-
-/// Information about suppressed warnings and hints for a given library.
-class SuppressionInfo {
-  int warnings = 0;
-  int hints = 0;
-}
-
-class GenericTask extends CompilerTask {
-  final String name;
-
-  GenericTask(this.name, Compiler compiler)
-      : super(compiler);
-}