pkg/front_end/lib/src/fasta/kernel/kernel_target.dart

// Copyright (c) 2016, 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 fasta.kernel_target;

import 'dart:async' show Future;

import 'package:kernel/ast.dart'
    show
        Arguments,
        Block,
        CanonicalName,
        Class,
        Component,
        Constructor,
        DartType,
        DynamicType,
        EmptyStatement,
        Expression,
        ExpressionStatement,
        Field,
        FieldInitializer,
        FunctionNode,
        Initializer,
        InvalidInitializer,
        Library,
        ListLiteral,
        Name,
        NamedExpression,
        NullLiteral,
        Procedure,
        ProcedureKind,
        RedirectingInitializer,
        Source,
        Statement,
        StringLiteral,
        SuperInitializer,
        Throw,
        TypeParameter,
        VariableDeclaration,
        VariableGet,
        VoidType;

import 'package:kernel/type_algebra.dart' show substitute;

import '../../api_prototype/file_system.dart' show FileSystem;

import '../compiler_context.dart' show CompilerContext;

import '../crash.dart' show withCrashReporting;

import '../dill/dill_target.dart' show DillTarget;

import '../dill/dill_member_builder.dart' show DillMemberBuilder;

import '../messages.dart'
    show
        LocatedMessage,
        messageConstConstructorNonFinalField,
        messageConstConstructorNonFinalFieldCause,
        messageConstConstructorRedirectionToNonConst,
        noLength,
        templateFinalFieldNotInitialized,
        templateFinalFieldNotInitializedByConstructor,
        templateMissingImplementationCause,
        templateSuperclassHasNoDefaultConstructor;

import '../problems.dart' show unhandled;

import '../severity.dart' show Severity;

import '../source/source_class_builder.dart' show SourceClassBuilder;

import '../source/source_loader.dart' show SourceLoader;

import '../target_implementation.dart' show TargetImplementation;

import '../uri_translator.dart' show UriTranslator;

import 'kernel_builder.dart'
    show
        ClassBuilder,
        Declaration,
        InvalidTypeBuilder,
        KernelClassBuilder,
        KernelFieldBuilder,
        KernelLibraryBuilder,
        KernelNamedTypeBuilder,
        KernelProcedureBuilder,
        LibraryBuilder,
        NamedTypeBuilder,
        TypeBuilder,
        TypeDeclarationBuilder,
        TypeVariableBuilder;

import 'metadata_collector.dart' show MetadataCollector;

import 'verifier.dart' show verifyComponent;

class KernelTarget extends TargetImplementation {
  /// The [FileSystem] which should be used to access files.
  final FileSystem fileSystem;

  /// Whether comments should be scanned and parsed.
  final bool includeComments;

  final DillTarget dillTarget;

  /// Shared with [CompilerContext].
  final Map<Uri, Source> uriToSource;

  /// The [MetadataCollector] to write metadata to.
  final MetadataCollector metadataCollector;

  SourceLoader<Library> loader;

  Component component;

  final List<LocatedMessage> errors = <LocatedMessage>[];

  final TypeBuilder dynamicType = new KernelNamedTypeBuilder("dynamic", null);

  final NamedTypeBuilder objectType =
      new KernelNamedTypeBuilder("Object", null);

  final TypeBuilder bottomType = new KernelNamedTypeBuilder("Null", null);

  bool get strongMode => backendTarget.strongMode;

  bool get disableTypeInference => backendTarget.disableTypeInference;

  final bool excludeSource = !CompilerContext.current.options.embedSourceText;

  KernelTarget(this.fileSystem, this.includeComments, DillTarget dillTarget,
      UriTranslator uriTranslator,
      {Map<Uri, Source> uriToSource, MetadataCollector metadataCollector})
      : dillTarget = dillTarget,
        uriToSource = uriToSource ?? CompilerContext.current.uriToSource,
        metadataCollector = metadataCollector,
        super(dillTarget.ticker, uriTranslator, dillTarget.backendTarget) {
    loader = createLoader();
  }

  SourceLoader<Library> createLoader() =>
      new SourceLoader<Library>(fileSystem, includeComments, this);

  void addSourceInformation(
      Uri uri, List<int> lineStarts, List<int> sourceCode) {
    uriToSource[uri] = new Source(lineStarts, sourceCode);
  }

  void read(Uri uri) {
    loader.read(uri, -1);
  }

  @override
  LibraryBuilder createLibraryBuilder(
      Uri uri, Uri fileUri, KernelLibraryBuilder origin) {
    if (dillTarget.isLoaded) {
      var builder = dillTarget.loader.builders[uri];
      if (builder != null) {
        return builder;
      }
    }
    return new KernelLibraryBuilder(uri, fileUri, loader, origin);
  }

  void forEachDirectSupertype(ClassBuilder cls, void f(NamedTypeBuilder type)) {
    TypeBuilder supertype = cls.supertype;
    if (supertype is NamedTypeBuilder) {
      f(supertype);
    } else if (supertype != null) {
      unhandled("${supertype.runtimeType}", "forEachDirectSupertype",
          cls.charOffset, cls.fileUri);
    }
    if (cls.interfaces != null) {
      for (NamedTypeBuilder t in cls.interfaces) {
        f(t);
      }
    }
    if (cls.library.loader == loader &&
        // TODO(ahe): Implement DillClassBuilder.mixedInType and remove the
        // above check.
        cls.mixedInType != null) {
      f(cls.mixedInType);
    }
  }

  void addDirectSupertype(ClassBuilder cls, Set<ClassBuilder> set) {
    if (cls == null) return;
    forEachDirectSupertype(cls, (NamedTypeBuilder type) {
      Declaration declaration = type.declaration;
      if (declaration is ClassBuilder) {
        set.add(declaration);
      }
    });
  }

  /// Returns classes defined in libraries in [loader].
  List<SourceClassBuilder> collectMyClasses() {
    List<SourceClassBuilder> result = <SourceClassBuilder>[];
    loader.builders.forEach((Uri uri, LibraryBuilder library) {
      if (library.loader == loader) {
        library.forEach((String name, Declaration member) {
          if (member is SourceClassBuilder && !member.isPatch) {
            result.add(member);
          }
        });
      }
    });
    return result;
  }

  void breakCycle(ClassBuilder builder) {
    Class cls = builder.target;
    cls.implementedTypes.clear();
    cls.supertype = null;
    cls.mixedInType = null;
    builder.supertype = new KernelNamedTypeBuilder("Object", null)
      ..bind(objectClassBuilder);
    builder.interfaces = null;
    builder.mixedInType = null;
  }

  void handleInputError(LocatedMessage message, {bool isFullComponent}) {
    if (message != null) {
      context.report(message, Severity.error);
      errors.add(message);
    }
    component = erroneousComponent(isFullComponent);
  }

  @override
  Future<Component> buildOutlines({CanonicalName nameRoot}) async {
    if (loader.first == null) return null;
    return withCrashReporting<Component>(
        () async {
          loader.createTypeInferenceEngine();
          await loader.buildOutlines();
          loader.coreLibrary.becomeCoreLibrary(const DynamicType());
          dynamicType.bind(loader.coreLibrary["dynamic"]);
          loader.resolveParts();
          loader.computeLibraryScopes();
          objectType.bind(loader.coreLibrary["Object"]);
          bottomType.bind(loader.coreLibrary["Null"]);
          loader.resolveTypes();
          loader.computeDefaultTypes(
              dynamicType, bottomType, objectClassBuilder);
          List<SourceClassBuilder> myClasses = collectMyClasses();
          loader.checkSemantics(myClasses);
          loader.finishTypeVariables(objectClassBuilder, dynamicType);
          loader.buildComponent();
          installDefaultSupertypes();
          installDefaultConstructors(myClasses);
          loader.resolveConstructors();
          component = link(new List<Library>.from(loader.libraries),
              nameRoot: nameRoot);
          computeCoreTypes();
          loader.computeHierarchy();
          loader.performTopLevelInference(myClasses);
          loader.checkSupertypes(myClasses);
          loader.checkOverrides(myClasses);
          loader.checkAbstractMembers(myClasses);
          loader.addNoSuchMethodForwarders(myClasses);
          return component;
        },
        () => loader?.currentUriForCrashReporting,
        onInputError: (LocatedMessage message) {
          ticker.logMs("Got unrecoverable error");
          handleInputError(message, isFullComponent: false);
          return component;
        });
  }

  /// Build the kernel representation of the component loaded by this
  /// target. The component will contain full bodies for the code loaded from
  /// sources, and only references to the code loaded by the [DillTarget],
  /// which may or may not include method bodies (depending on what was loaded
  /// into that target, an outline or a full kernel component).
  ///
  /// If [verify], run the default kernel verification on the resulting
  /// component.
  @override
  Future<Component> buildComponent({bool verify: false}) async {
    if (loader.first == null) return null;
    if (errors.isNotEmpty) {
      handleInputError(null, isFullComponent: true);
      return component;
    }

    return withCrashReporting<Component>(
        () async {
          ticker.logMs("Building component");
          await loader.buildBodies();
          loader.finishDeferredLoadTearoffs();
          loader.finishNoSuchMethodForwarders();
          List<SourceClassBuilder> myClasses = collectMyClasses();
          loader.finishNativeMethods();
          loader.finishPatchMethods();
          finishAllConstructors(myClasses);
          runBuildTransformations();

          if (verify) this.verify();
          if (errors.isNotEmpty) {
            handleInputError(null, isFullComponent: true);
          }
          handleRecoverableErrors(loader.unhandledErrors);
          return component;
        },
        () => loader?.currentUriForCrashReporting,
        onInputError: (LocatedMessage message) {
          ticker.logMs("Got unrecoverable error");
          handleInputError(message, isFullComponent: true);
          return component;
        });
  }

  /// Adds a synthetic field named `#errors` to the main library that contains
  /// [recoverableErrors] formatted.
  ///
  /// If [recoverableErrors] is empty, this method does nothing.
  ///
  /// If there's no main library, this method uses [erroneousComponent] to
  /// replace [component].
  void handleRecoverableErrors(List<LocatedMessage> recoverableErrors) {
    if (recoverableErrors.isEmpty) return;
    KernelLibraryBuilder mainLibrary = loader.first;
    if (mainLibrary == null) {
      component = erroneousComponent(true);
      return;
    }
    List<Expression> expressions = <Expression>[];
    for (LocatedMessage error in recoverableErrors) {
      errors.add(error);
      expressions.add(new StringLiteral(context.format(error, Severity.error)));
    }
    mainLibrary.library.addMember(new Field(new Name("#errors"),
        initializer: new ListLiteral(expressions, isConst: true),
        isConst: true,
        isStatic: true));
  }

  Component erroneousComponent(bool isFullComponent) {
    Uri uri = loader.first?.uri ?? Uri.parse("error:error");
    Uri fileUri = loader.first?.fileUri ?? uri;
    KernelLibraryBuilder library =
        new KernelLibraryBuilder(uri, fileUri, loader, null);
    loader.first = library;
    if (isFullComponent) {
      // If this is an outline, we shouldn't add an executable main
      // method. Similarly considerations apply to separate compilation. It
      // could also make sense to add a way to mark .dill files as having
      // compile-time errors.
      KernelProcedureBuilder mainBuilder = new KernelProcedureBuilder(
          null,
          0,
          null,
          "#main",
          null,
          null,
          ProcedureKind.Method,
          library,
          -1,
          -1,
          -1,
          -1);
      library.addBuilder(mainBuilder.name, mainBuilder, -1);
      mainBuilder.body = new Block(new List<Statement>.from(errors.map(
          (LocatedMessage message) => new ExpressionStatement(new Throw(
              new StringLiteral(context.format(message, Severity.error)))))));
    }

    // Clear libraries to avoid having 'the same' library added in both outline
    // and body building. As loader.libraries is used in the incremental
    // compiler that will causes problems (i.e. it cannot serialize because 2
    // libraries has the same URI).
    loader.libraries.clear();

    loader.libraries.add(library.library);
    library.build(loader.coreLibrary);
    return link(<Library>[library.library]);
  }

  /// Creates a component by combining [libraries] with the libraries of
  /// `dillTarget.loader.component`.
  Component link(List<Library> libraries, {CanonicalName nameRoot}) {
    libraries.addAll(dillTarget.loader.libraries);

    Map<Uri, Source> uriToSource = new Map<Uri, Source>();
    void copySource(Uri uri, Source source) {
      uriToSource[uri] =
          excludeSource ? new Source(source.lineStarts, const <int>[]) : source;
    }

    this.uriToSource.forEach(copySource);
    dillTarget.loader.uriToSource.forEach(copySource);

    Component component = CompilerContext.current.options.target
        .configureComponent(new Component(
            nameRoot: nameRoot,
            libraries: libraries,
            uriToSource: uriToSource));
    if (loader.first != null) {
      // TODO(sigmund): do only for full program
      Declaration declaration =
          loader.first.exportScope.lookup("main", -1, null);
      if (declaration is KernelProcedureBuilder) {
        component.mainMethod = declaration.procedure;
      } else if (declaration is DillMemberBuilder) {
        if (declaration.member is Procedure) {
          component.mainMethod = declaration.member;
        }
      }
    }

    if (metadataCollector != null) {
      component.addMetadataRepository(metadataCollector.repository);
    }

    ticker.logMs("Linked component");
    return component;
  }

  void installDefaultSupertypes() {
    Class objectClass = this.objectClass;
    loader.builders.forEach((Uri uri, LibraryBuilder library) {
      if (library.loader == loader) {
        library.forEach((String name, Declaration declaration) {
          while (declaration != null) {
            if (declaration is SourceClassBuilder) {
              Class cls = declaration.target;
              if (cls != objectClass) {
                cls.supertype ??= objectClass.asRawSupertype;
                declaration.supertype ??=
                    new KernelNamedTypeBuilder("Object", null)
                      ..bind(objectClassBuilder);
              }
              if (declaration.isMixinApplication) {
                cls.mixedInType = declaration.mixedInType.buildMixedInType(
                    library, declaration.charOffset, declaration.fileUri);
              }
            }
            declaration = declaration.next;
          }
        });
      }
    });
    ticker.logMs("Installed Object as implicit superclass");
  }

  void installDefaultConstructors(List<SourceClassBuilder> builders) {
    Class objectClass = this.objectClass;
    for (SourceClassBuilder builder in builders) {
      if (builder.target != objectClass) {
        installDefaultConstructor(builder);
      }
    }
    ticker.logMs("Installed default constructors");
  }

  KernelClassBuilder get objectClassBuilder => objectType.declaration;

  Class get objectClass => objectClassBuilder.cls;

  /// If [builder] doesn't have a constructors, install the defaults.
  void installDefaultConstructor(SourceClassBuilder builder) {
    if (builder.isMixinApplication && !builder.isNamedMixinApplication) return;
    // TODO(askesc): Make this check light-weight in the absence of patches.
    if (builder.target.constructors.isNotEmpty) return;
    if (builder.target.redirectingFactoryConstructors.isNotEmpty) return;
    for (Procedure proc in builder.target.procedures) {
      if (proc.isFactory) return;
    }
    if (builder.isPatch) return;

    /// Quotes below are from [Dart Programming Language Specification, 4th
    /// Edition](
    /// https://ecma-international.org/publications/files/ECMA-ST/ECMA-408.pdf):
    if (builder.isNamedMixinApplication) {
      /// >A mixin application of the form S with M; defines a class C with
      /// >superclass S.
      /// >...

      /// >Let LM be the library in which M is declared. For each generative
      /// >constructor named qi(Ti1 ai1, . . . , Tiki aiki), i in 1..n of S
      /// >that is accessible to LM , C has an implicitly declared constructor
      /// >named q'i = [C/S]qi of the form q'i(ai1,...,aiki) :
      /// >super(ai1,...,aiki);.
      TypeDeclarationBuilder supertype = builder;
      while (supertype.isMixinApplication) {
        SourceClassBuilder named = supertype;
        TypeBuilder type = named.supertype;
        if (type is NamedTypeBuilder) {
          supertype = type.declaration;
        } else {
          unhandled("${type.runtimeType}", "installDefaultConstructor",
              builder.charOffset, builder.fileUri);
        }
      }
      if (supertype is KernelClassBuilder) {
        Map<TypeParameter, DartType> substitutionMap =
            computeKernelSubstitutionMap(
                builder.getSubstitutionMap(supertype, builder.fileUri,
                    builder.charOffset, dynamicType),
                builder.parent);
        if (supertype.cls.constructors.isEmpty) {
          builder.addSyntheticConstructor(makeDefaultConstructor());
        } else {
          for (Constructor constructor in supertype.cls.constructors) {
            builder.addSyntheticConstructor(makeMixinApplicationConstructor(
                builder.cls.mixin, constructor, substitutionMap));
          }
        }
      } else if (supertype is InvalidTypeBuilder) {
        builder.addSyntheticConstructor(makeDefaultConstructor());
      } else {
        unhandled("${supertype.runtimeType}", "installDefaultConstructor",
            builder.charOffset, builder.fileUri);
      }
    } else {
      /// >Iff no constructor is specified for a class C, it implicitly has a
      /// >default constructor C() : super() {}, unless C is class Object.
      // The superinitializer is installed below in [finishConstructors].
      builder.addSyntheticConstructor(makeDefaultConstructor());
    }
  }

  Map<TypeParameter, DartType> computeKernelSubstitutionMap(
      Map<TypeVariableBuilder, TypeBuilder> substitutionMap,
      LibraryBuilder library) {
    if (substitutionMap == null) return const <TypeParameter, DartType>{};
    Map<TypeParameter, DartType> result = <TypeParameter, DartType>{};
    substitutionMap
        .forEach((TypeVariableBuilder variable, TypeBuilder argument) {
      result[variable.target] = argument.build(library);
    });
    return result;
  }

  Constructor makeMixinApplicationConstructor(Class mixin,
      Constructor constructor, Map<TypeParameter, DartType> substitutionMap) {
    VariableDeclaration copyFormal(VariableDeclaration formal) {
      // TODO(ahe): Handle initializers.
      var copy = new VariableDeclaration(formal.name,
          isFinal: formal.isFinal, isConst: formal.isConst);
      if (formal.type != null) {
        copy.type = substitute(formal.type, substitutionMap);
      }
      return copy;
    }

    List<VariableDeclaration> positionalParameters = <VariableDeclaration>[];
    List<VariableDeclaration> namedParameters = <VariableDeclaration>[];
    List<Expression> positional = <Expression>[];
    List<NamedExpression> named = <NamedExpression>[];
    for (VariableDeclaration formal
        in constructor.function.positionalParameters) {
      positionalParameters.add(copyFormal(formal));
      positional.add(new VariableGet(positionalParameters.last));
    }
    for (VariableDeclaration formal in constructor.function.namedParameters) {
      namedParameters.add(copyFormal(formal));
      named.add(new NamedExpression(
          formal.name, new VariableGet(namedParameters.last)));
    }
    FunctionNode function = new FunctionNode(new EmptyStatement(),
        positionalParameters: positionalParameters,
        namedParameters: namedParameters,
        requiredParameterCount: constructor.function.requiredParameterCount,
        returnType: const VoidType());
    SuperInitializer initializer = new SuperInitializer(
        constructor, new Arguments(positional, named: named));
    return new Constructor(function,
        name: constructor.name,
        initializers: <Initializer>[initializer],
        isSynthetic: true);
  }

  Constructor makeDefaultConstructor() {
    return new Constructor(
        new FunctionNode(new EmptyStatement(), returnType: const VoidType()),
        name: new Name(""),
        isSynthetic: true);
  }

  void computeCoreTypes() {
    List<Library> libraries = <Library>[];
    for (String platformLibrary in const [
      "dart:_internal",
      "dart:async",
      "dart:core",
      "dart:mirrors"
    ]) {
      Uri uri = Uri.parse(platformLibrary);
      LibraryBuilder library = loader.builders[uri];
      if (library == null) {
        // TODO(ahe): This is working around a bug in kernel_driver_test or
        // kernel_driver.
        bool found = false;
        for (Library target in dillTarget.loader.libraries) {
          if (target.importUri == uri) {
            libraries.add(target);
            found = true;
            break;
          }
        }
        if (!found && uri.path != "mirrors") {
          // dart:mirrors is optional.
          throw "Can't find $uri";
        }
      } else {
        libraries.add(library.target);
      }
    }
    Component plaformLibraries = CompilerContext.current.options.target
        .configureComponent(new Component());
    // Add libraries directly to prevent that their parents are changed.
    plaformLibraries.libraries.addAll(libraries);
    loader.computeCoreTypes(plaformLibraries);
  }

  void finishAllConstructors(List<SourceClassBuilder> builders) {
    Class objectClass = this.objectClass;
    for (SourceClassBuilder builder in builders) {
      Class cls = builder.target;
      if (cls != objectClass) {
        finishConstructors(builder);
      }
    }
    ticker.logMs("Finished constructors");
  }

  /// Ensure constructors of [cls] have the correct initializers and other
  /// requirements.
  void finishConstructors(SourceClassBuilder builder) {
    if (builder.isPatch) return;
    Class cls = builder.target;

    /// Quotes below are from [Dart Programming Language Specification, 4th
    /// Edition](http://www.ecma-international.org/publications/files/ECMA-ST/ECMA-408.pdf):
    List<Field> uninitializedFields = <Field>[];
    List<Field> nonFinalFields = <Field>[];
    for (Field field in cls.fields) {
      if (field.isInstanceMember && !field.isFinal) {
        nonFinalFields.add(field);
      }
      if (field.initializer == null) {
        uninitializedFields.add(field);
      }
    }
    Map<Constructor, Set<Field>> constructorInitializedFields =
        <Constructor, Set<Field>>{};
    Constructor superTarget;
    for (Constructor constructor in cls.constructors) {
      bool isRedirecting = false;
      for (Initializer initializer in constructor.initializers) {
        if (initializer is RedirectingInitializer) {
          if (constructor.isConst && !initializer.target.isConst) {
            builder.addProblem(messageConstConstructorRedirectionToNonConst,
                initializer.fileOffset, initializer.target.name.name.length);
          }
          isRedirecting = true;
          break;
        }
      }
      if (!isRedirecting) {
        /// >If no superinitializer is provided, an implicit superinitializer
        /// >of the form super() is added at the end of k’s initializer list,
        /// >unless the enclosing class is class Object.
        if (constructor.initializers.isEmpty) {
          superTarget ??= defaultSuperConstructor(cls);
          Initializer initializer;
          if (superTarget == null) {
            builder.addProblem(
                templateSuperclassHasNoDefaultConstructor
                    .withArguments(cls.superclass.name),
                constructor.fileOffset,
                noLength);
            initializer = new InvalidInitializer();
          } else {
            initializer =
                new SuperInitializer(superTarget, new Arguments.empty())
                  ..isSynthetic = true;
          }
          constructor.initializers.add(initializer);
          initializer.parent = constructor;
        }
        if (constructor.function.body == null) {
          /// >If a generative constructor c is not a redirecting constructor
          /// >and no body is provided, then c implicitly has an empty body {}.
          /// We use an empty statement instead.
          constructor.function.body = new EmptyStatement();
          constructor.function.body.parent = constructor.function;
        }

        Set<Field> myInitializedFields = new Set<Field>();
        for (Initializer initializer in constructor.initializers) {
          if (initializer is FieldInitializer) {
            myInitializedFields.add(initializer.field);
          }
        }
        for (VariableDeclaration formal
            in constructor.function.positionalParameters) {
          if (formal.isFieldFormal) {
            Declaration fieldBuilder = builder.scope.local[formal.name] ??
                builder.origin.scope.local[formal.name];
            if (fieldBuilder is KernelFieldBuilder) {
              myInitializedFields.add(fieldBuilder.field);
            }
          }
        }
        constructorInitializedFields[constructor] = myInitializedFields;
        if (constructor.isConst && nonFinalFields.isNotEmpty) {
          builder.addProblem(messageConstConstructorNonFinalField,
              constructor.fileOffset, noLength,
              context: nonFinalFields
                  .map((field) => messageConstConstructorNonFinalFieldCause
                      .withLocation(field.fileUri, field.fileOffset, noLength))
                  .toList());
          nonFinalFields.clear();
        }
      }
    }
    Set<Field> initializedFields;
    constructorInitializedFields
        .forEach((Constructor constructor, Set<Field> fields) {
      if (initializedFields == null) {
        initializedFields = new Set<Field>.from(fields);
      } else {
        initializedFields.addAll(fields);
      }
    });

    // Run through all fields that aren't initialized by any constructor, and
    // set their initializer to `null`.
    for (Field field in uninitializedFields) {
      if (initializedFields == null || !initializedFields.contains(field)) {
        field.initializer = new NullLiteral()..parent = field;
        if (field.isFinal && cls.constructors.isNotEmpty) {
          builder.library.addProblem(
              templateFinalFieldNotInitialized.withArguments(field.name.name),
              field.fileOffset,
              field.name.name.length,
              field.fileUri);
        }
      }
    }

    // Run through all fields that are initialized by some constructor, and
    // make sure that all other constructors also initialize them.
    constructorInitializedFields
        .forEach((Constructor constructor, Set<Field> fields) {
      for (Field field in initializedFields.difference(fields)) {
        if (field.initializer == null) {
          FieldInitializer initializer =
              new FieldInitializer(field, new NullLiteral())
                ..isSynthetic = true;
          initializer.parent = constructor;
          constructor.initializers.insert(0, initializer);
          if (field.isFinal) {
            builder.library.addProblem(
                templateFinalFieldNotInitializedByConstructor
                    .withArguments(field.name.name),
                constructor.fileOffset,
                constructor.name.name.length,
                constructor.fileUri,
                context: [
                  templateMissingImplementationCause
                      .withArguments(field.name.name)
                      .withLocation(field.fileUri, field.fileOffset,
                          field.name.name.length)
                ]);
          }
        }
      }
    });
  }

  /// Run all transformations that are needed when building a bundle of
  /// libraries for the first time.
  void runBuildTransformations() {
    backendTarget.performModularTransformationsOnLibraries(
        component, loader.coreTypes, loader.hierarchy, loader.libraries,
        logger: (String msg) => ticker.logMs(msg));
  }

  void runProcedureTransformations(Procedure procedure) {
    backendTarget.performTransformationsOnProcedure(
        loader.coreTypes, loader.hierarchy, procedure,
        logger: (String msg) => ticker.logMs(msg));
  }

  void verify() {
    errors.addAll(verifyComponent(component));
    ticker.logMs("Verified component");
  }

  /// Return `true` if the given [library] was built by this [KernelTarget]
  /// from sources, and not loaded from a [DillTarget].
  bool isSourceLibrary(Library library) {
    return loader.libraries.contains(library);
  }

  @override
  void readPatchFiles(KernelLibraryBuilder library) {
    assert(library.uri.scheme == "dart");
    List<Uri> patches = uriTranslator.getDartPatches(library.uri.path);
    if (patches != null) {
      KernelLibraryBuilder first;
      for (Uri patch in patches) {
        if (first == null) {
          first =
              library.loader.read(patch, -1, fileUri: patch, origin: library);
        } else {
          // If there's more than one patch file, it's interpreted as a part of
          // the patch library.
          KernelLibraryBuilder part =
              library.loader.read(patch, -1, fileUri: patch);
          first.parts.add(part);
          part.addPartOf(null, null, "${first.uri}", -1);
        }
      }
    }
  }
}

/// Looks for a constructor call that matches `super()` from a constructor in
/// [cls]. Such a constructor may have optional arguments, but no required
/// arguments.
Constructor defaultSuperConstructor(Class cls) {
  Class superclass = cls.superclass;
  while (superclass != null && superclass.isMixinApplication) {
    superclass = superclass.superclass;
  }
  for (Constructor constructor in superclass.constructors) {
    if (constructor.name.name.isEmpty) {
      return constructor.function.requiredParameterCount == 0
          ? constructor
          : null;
    }
  }
  return null;
}