Linter Demo

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Warnings: 7

File: /home/fstrocco/Dart/dart/benchmark/compiler/lib/src/js_backend/custom_elements_analysis.dart

// Copyright (c) 2013, 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; /** * Support for Custom Elements. * * The support for custom elements the compiler builds a table that maps the * custom element class's [Type] to the interceptor for the class and the * constructor(s) for the class. * * We want the table to contain only the custom element classes used, and we * want to avoid resolving and compiling constructors that are not used since * that may bring in unused code. This class controls the resolution and code * generation to restrict the impact. * * The following line of code requires the generation of the generative * constructor factory function(s) for FancyButton, and their insertion into the * table: * * document.register(FancyButton, 'x-fancy-button'); * * We detect this by 'joining' the classes that are referenced as type literals * with the classes that are custom elements, enabled by detecting the presence * of the table access code used by document.register. * * We have to be more conservative when the type is unknown, e.g. * * document.register(classMirror.reflectedType, tagFromMetadata); * * and * * class Component<T> { * final tag; * Component(this.tag); * void register() => document.register(T, tag); * } * const Component<FancyButton>('x-fancy-button').register(); * * In these cases we conservatively generate all viable entries in the table. */ class CustomElementsAnalysis { final JavaScriptBackend backend; final Compiler compiler; final CustomElementsAnalysisJoin resolutionJoin; final CustomElementsAnalysisJoin codegenJoin; bool fetchedTableAccessorMethod = false; Element tableAccessorMethod; CustomElementsAnalysis(JavaScriptBackend backend) : this.backend = backend, this.compiler = backend.compiler, resolutionJoin = new CustomElementsAnalysisJoin(backend), codegenJoin = new CustomElementsAnalysisJoin(backend) { // TODO(sra): Remove this work-around. We should mark allClassesSelected in // both joins only when we see a construct generating an unknown [Type] but // we can't currently recognize all cases. In particular, the work-around // for the unimplemented `ClassMirror.reflectedType` is not recognizable. // TODO(12607): Match on [ClassMirror.reflectedType] resolutionJoin.allClassesSelected = true; codegenJoin.allClassesSelected = true; } CustomElementsAnalysisJoin joinFor(Enqueuer enqueuer) => enqueuer.isResolutionQueue ? resolutionJoin : codegenJoin; void registerInstantiatedClass(ClassElement classElement, Enqueuer enqueuer) { classElement.ensureResolved(compiler); if (!Elements.isNativeOrExtendsNative(classElement)) return; if (classElement.isMixinApplication) return; if (classElement.isAbstract) return; joinFor(enqueuer).instantiatedClasses.add(classElement); } void registerTypeLiteral(DartType type, Registry registry) { assert(registry.isForResolution); // In codegen we see the TypeConstants instead. if (!registry.isForResolution) return; if (type.isInterfaceType) { // TODO(sra): If we had a flow query from the type literal expression to // the Type argument of the metadata lookup, we could tell if this type // literal is really a demand for the metadata. resolutionJoin.selectedClasses.add(type.element); } else if (type.isTypeVariable) { // This is a type parameter of a parameterized class. // TODO(sra): Is there a way to determine which types are bound to the // parameter? resolutionJoin.allClassesSelected = true; } } void registerTypeConstant(Element element, Enqueuer enqueuer) { assert(element.isClass); assert(!enqueuer.isResolutionQueue); codegenJoin.selectedClasses.add(element); } void registerStaticUse(Element element, Enqueuer enqueuer) { assert(element != null); if (!fetchedTableAccessorMethod) { fetchedTableAccessorMethod = true; tableAccessorMethod = backend.findInterceptor( 'findIndexForNativeSubclassType'); } if (element == tableAccessorMethod) { joinFor(enqueuer).demanded = true; } } void onQueueEmpty(Enqueuer enqueuer) { joinFor(enqueuer).flush(enqueuer); } bool get needsTable => codegenJoin.demanded; bool needsClass(ClassElement classElement) => codegenJoin.activeClasses.contains(classElement); List<Element> constructors(ClassElement classElement) => codegenJoin.computeEscapingConstructors(classElement); } class CustomElementsAnalysisJoin { final JavaScriptBackend backend; Compiler get compiler => backend.compiler; // Classes that are candidates for needing constructors. Classes are moved to // [activeClasses] when we know they need constructors. final instantiatedClasses = new Set<ClassElement>(); // Classes explicitly named. final selectedClasses = new Set<ClassElement>(); // True if we must conservatively include all extension classes. bool allClassesSelected = false; // Did we see a demand for the data? bool demanded = false; // ClassesOutput: classes requiring metadata. final activeClasses = new Set<ClassElement>(); CustomElementsAnalysisJoin(this.backend); void flush(Enqueuer enqueuer) { if (!demanded) return; var newActiveClasses = new Set<ClassElement>(); for (ClassElement classElement in instantiatedClasses) { bool isNative = classElement.isNative; bool isExtension = !isNative && Elements.isNativeOrExtendsNative(classElement); // Generate table entries for native classes that are explicitly named and // extensions that fix our criteria. if ((isNative && selectedClasses.contains(classElement)) || (isExtension && (allClassesSelected || selectedClasses.contains(classElement)))) { newActiveClasses.add(classElement); Iterable<Element> escapingConstructors = computeEscapingConstructors(classElement); escapingConstructors.forEach(enqueuer.registerStaticUse); escapingConstructors .forEach(compiler.globalDependencies.registerDependency); // Force the generaton of the type constant that is the key to an entry // in the generated table. ConstantValue constant = makeTypeConstant(classElement); backend.registerCompileTimeConstant( constant, compiler.globalDependencies); backend.constants.addCompileTimeConstantForEmission(constant); } } activeClasses.addAll(newActiveClasses); instantiatedClasses.removeAll(newActiveClasses); } TypeConstantValue makeTypeConstant(ClassElement element) { DartType elementType = element.rawType; DartType constantType = backend.typeImplementation.rawType; return new TypeConstantValue(elementType, constantType); } List<Element> computeEscapingConstructors(ClassElement classElement) { List<Element> result = <Element>[]; // Only classes that extend native classes have constructors in the table. // We could refine this to classes that extend Element, but that would break // the tests and there is no sane reason to subclass other native classes. if (classElement.isNative) return result; selectGenerativeConstructors(ClassElement enclosing, Element member) { if (member.isGenerativeConstructor) { // Ignore constructors that cannot be called with zero arguments. FunctionElement constructor = member; FunctionSignature parameters = constructor.functionSignature; if (parameters.requiredParameterCount == 0) { result.add(member); } } } classElement.forEachMember(selectGenerativeConstructors, includeBackendMembers: false, includeSuperAndInjectedMembers: false); return result; } }