Revert "First step for modular output in fasta."

pkg/front_end/lib/src/fasta/kernel/kernel_outline_shaker.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.
-
-/// A transformation to create a self-contained modular kernel without
-/// unnecessary references to other libraries.
-library fasta.kernel.kernel_outline_shaker;
-
-import 'package:kernel/ast.dart';
-import 'package:kernel/core_types.dart';
-
-import '../errors.dart' show internalError;
-
-/// Removes from [program] unnecessary libraries, classes, and members.
-///
-/// This applies a simple "tree-shaking" technique: the full body of libraries
-/// whose URI match [isIncluded] is preserved, and so is the outline of the
-/// members and classes which are indicated by [data] (which should
-/// practically include all members and classes transitively visible from the
-/// included libraries).
-///
-/// The intent is that the resulting program has the entire code that is meant
-/// to be included and the minimum required to prevent dangling references and
-/// allow modular program transformations.
-///
-/// Note that the resulting program may include libraries not in [isIncluded],
-/// but those will be marked as external. There should be no method bodies for
-/// any members of those libraries.
-void trimProgram(Program program, RetainedData data, bool isIncluded(Uri uri)) {
-  new KernelOutlineShaker(data, isIncluded).transform(program);
-}
-
-/// Informs about which libraries, classes, and members should be retained by
-/// the [KernelOutlineShaker] when tree-shaking.
-abstract class RetainedData {
-  /// Whether a library should be preserved and mark as external.
-  bool isLibraryUsed(Library library);
-
-  /// Whether a class should be preserved. If a class is preserved, its
-  /// supertypes will be preserved too, but some of it members may not be
-  /// included.
-  bool isClassUsed(Class cls);
-
-  /// Whether a member should be preserved. If so, its enclosing class/library
-  /// will be preserved too.
-  bool isMemberUsed(Member member);
-}
-
-/// A builder of [RetainedData] that recursively marks transitive dependencies.
-///
-/// This builder contains APIs to mark the roots that are needed (e.g.
-/// [markClass] and [markMember]). Note this builder does not determine what
-/// roots to keep, that is done either directly by fasta while it is parsing, or
-/// by using a visitor like the [RootsMarker] below.
-class RetainedDataBuilder extends RetainedData {
-  /// Libraries that contained code that is transitively reachable from the
-  /// included libraries.
-  final Set<Library> libraries = new Set<Library>();
-
-  /// Classes that are transitively reachable from the included libraries.
-  final Set<Class> classes = new Set<Class>();
-
-  /// Members that are transitively reachable from the included libraries.
-  final Set<Member> members = new Set<Member>();
-
-  TypeMarker typeMarker;
-
-  @override
-  bool isLibraryUsed(Library library) => libraries.contains(library);
-
-  @override
-  bool isClassUsed(Class cls) => classes.contains(cls);
-
-  @override
-  bool isMemberUsed(Member m) => members.contains(m);
-
-  RetainedDataBuilder() {
-    typeMarker = new TypeMarker(this);
-  }
-
-  /// Mark a library as used.
-  void markLibrary(Library lib) {
-    libraries.add(lib);
-  }
-
-  /// Mark a class and it's supertypes as used.
-  void markClass(Class cls) {
-    if (cls == null || !classes.add(cls)) return;
-    markLibrary(cls.parent);
-    // TODO(sigmund): retain annotations?
-    // visitList(cls.annotations, this);
-    markSupertype(cls.supertype);
-    markSupertype(cls.mixedInType);
-    cls.implementedTypes.forEach(markSupertype);
-    cls.typeParameters.forEach((t) => t.bound.accept(typeMarker));
-  }
-
-  /// Mark the class and type arguments of [node].
-  void markSupertype(Supertype node) {
-    if (node == null) return;
-    markClass(node.classNode);
-    node.typeArguments.forEach((t) => t.accept(typeMarker));
-  }
-
-  /// Mark a member and types mentioned on its interface.
-  void markMember(Member m) {
-    if (m == null || !members.add(m)) return;
-    markMemberInterface(m);
-    var parent = m.parent;
-    if (parent is Library) {
-      markLibrary(parent);
-    } else if (parent is Class) {
-      markClass(parent);
-    }
-  }
-
-  void markMemberInterface(Member node) {
-    if (node is Field) {
-      node.type.accept(typeMarker);
-    } else if (node is Procedure) {
-      var function = node.function;
-      function.typeParameters.forEach((p) => p.bound.accept(typeMarker));
-      function.positionalParameters.forEach((p) => p.type.accept(typeMarker));
-      function.namedParameters.forEach((p) => p.type.accept(typeMarker));
-      function.returnType.accept(typeMarker);
-    }
-  }
-}
-
-/// A helper visitor used to mark transitive types by the [RetainedDataBuilder].
-class TypeMarker extends DartTypeVisitor {
-  RetainedDataBuilder data;
-
-  TypeMarker(this.data);
-
-  visitInterfaceType(InterfaceType node) {
-    data.markClass(node.classNode);
-    node.typeArguments.forEach((t) => t.accept(this));
-  }
-
-  visitFunctionType(FunctionType node) {
-    node.typeParameters.forEach((t) => t.bound.accept(this));
-    node.positionalParameters.forEach((t) => t.accept(this));
-    node.namedParameters.forEach((t) => t.type.accept(this));
-    node.returnType.accept(this);
-  }
-
-  visitTypeParameterType(TypeParameterType node) {
-    // Note: node.parameter is marked by marking the enclosing element.
-  }
-
-  visitTypedefType(TypedefType node) {
-    node.typeArguments.forEach((t) => t.accept(this));
-  }
-}
-
-/// Determines the root APIs that need to be retained before running the
-/// tree-shaker.
-///
-/// This is implemented using a visitor that walks through the sources that are
-/// intended to be part of the kernel output.
-// TODO(sigmund): delete. We should collect this information while
-// building kernel without having to run a visitor afterwards.
-class RootsMarker extends RecursiveVisitor {
-  final RetainedDataBuilder data;
-  RootsMarker(this.data);
-
-  void run(Program program, bool isIncluded(Uri uri)) {
-    markRequired(program);
-    data.markMember(program.mainMethod);
-    for (var library in program.libraries) {
-      if (isIncluded(library.importUri)) {
-        library.accept(this);
-      }
-    }
-  }
-
-  /// Marks classes and members that are assumed to exist by fasta or by
-  /// transformers.
-  // TODO(sigmund): consider being more fine-grained and only marking what is
-  // seen and used.
-  void markRequired(Program program) {
-    var coreTypes = new CoreTypes(program);
-    coreTypes.objectClass.members.forEach(data.markMember);
-
-    // These are assumed to be available by fasta:
-    data.markClass(coreTypes.objectClass);
-    data.markClass(coreTypes.nullClass);
-    data.markClass(coreTypes.boolClass);
-    data.markClass(coreTypes.intClass);
-    data.markClass(coreTypes.numClass);
-    data.markClass(coreTypes.doubleClass);
-    data.markClass(coreTypes.stringClass);
-    data.markClass(coreTypes.listClass);
-    data.markClass(coreTypes.mapClass);
-    data.markClass(coreTypes.iterableClass);
-    data.markClass(coreTypes.iteratorClass);
-    data.markClass(coreTypes.futureClass);
-    data.markClass(coreTypes.streamClass);
-    data.markClass(coreTypes.symbolClass);
-    data.markClass(coreTypes.internalSymbolClass);
-    data.markClass(coreTypes.typeClass);
-    data.markClass(coreTypes.functionClass);
-    data.markClass(coreTypes.invocationClass);
-    data.markMember(coreTypes.getMember("dart:_internal", "ExternalName", ""));
-
-    // These are needed by the continuation (async/await) transformer:
-    data.markClass(coreTypes.getClass('dart:core', 'Iterator'));
-    data.markClass(coreTypes.getClass('dart:async', 'Future'));
-    data.markClass(coreTypes.getClass('dart:async', 'FutureOr'));
-    data.markClass(coreTypes.getClass('dart:async', 'Completer'));
-    data.markMember(coreTypes.getMember('dart:async', 'Completer', 'sync'));
-    data.markMember(coreTypes.getMember('dart:core', '_SyncIterable', ''));
-    data.markMember(coreTypes.getMember('dart:async', '_StreamIterator', ''));
-    data.markMember(coreTypes.getMember('dart:async', 'Future', 'microtask'));
-    data.markMember(
-        coreTypes.getMember('dart:async', '_AsyncStarStreamController', ''));
-    data.markMember(coreTypes.getTopLevelMember('dart:core', 'print'));
-    data.markMember(
-        coreTypes.getTopLevelMember('dart:async', '_asyncThenWrapperHelper'));
-    data.markMember(
-        coreTypes.getTopLevelMember('dart:async', '_asyncErrorWrapperHelper'));
-    data.markMember(coreTypes.getTopLevelMember('dart:async', '_awaitHelper'));
-
-    // These are needed by the mixin transformer
-    data.markMember(coreTypes.getMember('dart:core', '_InvocationMirror', ''));
-    data.markMember(coreTypes.getMember('dart:core', 'List', 'from'));
-  }
-
-  visitConstructor(Constructor node) {
-    if (!node.initializers.any((i) => i is SuperInitializer)) {
-      // super() is currently implicit.
-      for (var ctor in node.enclosingClass.supertype.classNode.constructors) {
-        if (ctor.name.name == '') data.markMember(ctor);
-      }
-    }
-    node.visitChildren(this);
-  }
-
-  @override
-  visitSuperInitializer(SuperInitializer node) {
-    data.markMember(node.target);
-    node.visitChildren(this);
-  }
-
-  @override
-  visitRedirectingInitializer(RedirectingInitializer node) {
-    data.markMember(node.target);
-    node.visitChildren(this);
-  }
-
-  @override
-  visitConstructorInvocation(ConstructorInvocation node) {
-    data.markMember(node.target);
-    node.visitChildren(this);
-  }
-
-  @override
-  visitStaticInvocation(StaticInvocation node) {
-    data.markMember(node.target);
-    node.visitChildren(this);
-  }
-
-  @override
-  visitDirectMethodInvocation(DirectMethodInvocation node) {
-    if (node.receiver is! ThisExpression) {
-      return internalError('Direct calls are only supported on "this"');
-    }
-    data.markMember(node.target);
-    node.visitChildren(this);
-  }
-
-  @override
-  visitMethodInvocation(MethodInvocation node) {
-    data.markMember(node.interfaceTarget);
-    node.visitChildren(this);
-  }
-
-  @override
-  visitStaticGet(StaticGet node) {
-    data.markMember(node.target);
-    node.visitChildren(this);
-  }
-
-  @override
-  visitStaticSet(StaticSet node) {
-    data.markMember(node.target);
-    node.visitChildren(this);
-  }
-
-  @override
-  visitDirectPropertyGet(DirectPropertyGet node) {
-    data.markMember(node.target);
-    node.visitChildren(this);
-  }
-
-  @override
-  visitDirectPropertySet(DirectPropertySet node) {
-    data.markMember(node.target);
-    node.visitChildren(this);
-  }
-
-  @override
-  visitSuperPropertyGet(SuperPropertyGet node) {
-    data.markMember(node.interfaceTarget);
-    node.visitChildren(this);
-  }
-
-  @override
-  visitSuperPropertySet(SuperPropertySet node) {
-    data.markMember(node.interfaceTarget);
-    node.visitChildren(this);
-  }
-
-  @override
-  visitPropertyGet(PropertyGet node) {
-    data.markMember(node.interfaceTarget);
-    node.visitChildren(this);
-  }
-
-  @override
-  visitPropertySet(PropertySet node) {
-    data.markMember(node.interfaceTarget);
-    node.visitChildren(this);
-  }
-
-  @override
-  visitInterfaceType(InterfaceType node) {
-    data.markClass(node.classNode);
-    node.visitChildren(this);
-  }
-
-  @override
-  visitSupertype(Supertype node) {
-    data.markClass(node.classNode);
-    node.visitChildren(this);
-  }
-
-  @override
-  visitTypedefReference(Typedef node) {
-    return internalError('not implemented');
-  }
-}
-
-/// Transformer that trims everything in the excluded libraries that is not
-/// marked as preserved by the given [RetainedData]. For every member in these
-/// excluded libraries, this transformer also removes function bodies and
-/// initializers.
-class KernelOutlineShaker extends Transformer {
-  final RetainedData data;
-  final Filter isIncluded;
-
-  KernelOutlineShaker(this.data, this.isIncluded);
-
-  void transform(Program program) {
-    var toRemove = new Set<Library>();
-    for (var library in program.libraries) {
-      if (!isIncluded(library.importUri)) {
-        if (!data.isLibraryUsed(library)) {
-          toRemove.add(library);
-        } else {
-          library.isExternal = true;
-          library.transformChildren(this);
-        }
-      }
-    }
-    program.libraries.removeWhere(toRemove.contains);
-  }
-
-  Class visitClass(Class node) {
-    if (!data.isClassUsed(node)) {
-      node.canonicalName?.unbind();
-      return null; // Remove the class.
-    } else {
-      node.transformChildren(this);
-      return node;
-    }
-  }
-
-  Member defaultMember(Member node) {
-    if (!data.isMemberUsed(node)) {
-      node.canonicalName?.unbind();
-      return null;
-    } else {
-      if (node is Procedure) {
-        node.function.body = null;
-      } else if (node is Field) {
-        node.initializer = null;
-      } else if (node is Constructor) {
-        node.initializers.clear();
-        node.function.body = null;
-      }
-      return node;
-    }
-  }
-
-  /// Types appear to be encoded directly, so we have no need to preserve
-  /// typedefs.
-  // TODO(sigmund): revisit if this is not the case, the `inputError` in
-  // [RootsMarker] is meant to detect this.
-  Typedef visitTypedef(Typedef node) => null;
-
-  TreeNode defaultTreeNode(TreeNode node) => node;
-}
-
-typedef bool Filter(Uri uri);