pkg/compiler/lib/src/inferrer/type_system.dart

// Copyright (c) 2017, 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.

import '../common.dart';
import '../elements/entities.dart';
import '../elements/types.dart';
import '../types/abstract_value_domain.dart';
import '../universe/selector.dart';
import '../world.dart';
import 'type_graph_nodes.dart';

/// Strategy for creating type information from members and parameters and type
/// information for nodes.
abstract class TypeSystemStrategy<T> {
  /// Creates [MemberTypeInformation] for [member].
  MemberTypeInformation createMemberTypeInformation(
      AbstractValueDomain abstractValueDomain, MemberEntity member);

  /// Creates [ParameterTypeInformation] for [parameter].
  ParameterTypeInformation createParameterTypeInformation(
      AbstractValueDomain abstractValueDomain,
      Local parameter,
      TypeSystem<T> types);

  /// Calls [f] for each parameter in [function].
  void forEachParameter(FunctionEntity function, void f(Local parameter));

  /// Returns whether [node] is valid as a general phi node.
  bool checkPhiNode(T node);

  /// Returns whether [node] is valid as a loop phi node.
  bool checkLoopPhiNode(T node);

  /// Returns whether [node] is valid as a list allocation node.
  bool checkListNode(T node);

  /// Returns whether [node] is valid as a map allocation node.
  bool checkMapNode(T node);

  /// Returns whether [cls] is valid as a type mask base class.
  bool checkClassEntity(ClassEntity cls);
}

/**
 * The class [SimpleInferrerVisitor] will use when working on types.
 */
class TypeSystem<T> {
  final JClosedWorld _closedWorld;
  final TypeSystemStrategy<T> strategy;

  /// [parameterTypeInformations] and [memberTypeInformations] ordered by
  /// creation time. This is used as the inference enqueueing order.
  final List<TypeInformation> _orderedTypeInformations = <TypeInformation>[];

  /// [ParameterTypeInformation]s for parameters.
  final Map<Local, TypeInformation> parameterTypeInformations =
      new Map<Local, TypeInformation>();

  /// [MemberTypeInformation]s for members.
  final Map<MemberEntity, TypeInformation> memberTypeInformations =
      new Map<MemberEntity, TypeInformation>();

  /// [ListTypeInformation] for allocated lists.
  final Map<T, TypeInformation> allocatedLists = new Map<T, TypeInformation>();

  /// [MapTypeInformation] for allocated Maps.
  final Map<T, TypeInformation> allocatedMaps = new Map<T, TypeInformation>();

  /// Closures found during the analysis.
  final Set<TypeInformation> allocatedClosures = new Set<TypeInformation>();

  /// Cache of [ConcreteTypeInformation].
  final Map<AbstractValue, TypeInformation> concreteTypes =
      new Map<AbstractValue, TypeInformation>();

  /// List of [TypeInformation]s for calls inside method bodies.
  final List<CallSiteTypeInformation> allocatedCalls =
      <CallSiteTypeInformation>[];

  /// List of [TypeInformation]s allocated inside method bodies (narrowing,
  /// phis, and containers).
  final List<TypeInformation> allocatedTypes = <TypeInformation>[];

  /// [parameterTypeInformations] and [memberTypeInformations] ordered by
  /// creation time. This is used as the inference enqueueing order.
  Iterable<TypeInformation> get orderedTypeInformations =>
      _orderedTypeInformations;

  Iterable<TypeInformation> get allTypes => [
        parameterTypeInformations.values,
        memberTypeInformations.values,
        allocatedLists.values,
        allocatedMaps.values,
        allocatedClosures,
        concreteTypes.values,
        allocatedCalls,
        allocatedTypes
      ].expand((x) => x);

  TypeSystem(this._closedWorld, this.strategy) {
    nonNullEmptyType = getConcreteTypeFor(_abstractValueDomain.emptyType);
  }

  AbstractValueDomain get _abstractValueDomain =>
      _closedWorld.abstractValueDomain;

  /// Used to group [TypeInformation] nodes by the element that triggered their
  /// creation.
  MemberTypeInformation _currentMember = null;
  MemberTypeInformation get currentMember => _currentMember;

  void withMember(MemberEntity element, void action()) {
    assert(_currentMember == null,
        failedAt(element, "Already constructing graph for $_currentMember."));
    _currentMember = getInferredTypeOfMember(element);
    action();
    _currentMember = null;
  }

  TypeInformation nullTypeCache;
  TypeInformation get nullType {
    if (nullTypeCache != null) return nullTypeCache;
    return nullTypeCache = getConcreteTypeFor(_abstractValueDomain.nullType);
  }

  TypeInformation intTypeCache;
  TypeInformation get intType {
    if (intTypeCache != null) return intTypeCache;
    return intTypeCache = getConcreteTypeFor(_abstractValueDomain.intType);
  }

  TypeInformation uint32TypeCache;
  TypeInformation get uint32Type {
    if (uint32TypeCache != null) return uint32TypeCache;
    return uint32TypeCache =
        getConcreteTypeFor(_abstractValueDomain.uint32Type);
  }

  TypeInformation uint31TypeCache;
  TypeInformation get uint31Type {
    if (uint31TypeCache != null) return uint31TypeCache;
    return uint31TypeCache =
        getConcreteTypeFor(_abstractValueDomain.uint31Type);
  }

  TypeInformation positiveIntTypeCache;
  TypeInformation get positiveIntType {
    if (positiveIntTypeCache != null) return positiveIntTypeCache;
    return positiveIntTypeCache =
        getConcreteTypeFor(_abstractValueDomain.positiveIntType);
  }

  TypeInformation doubleTypeCache;
  TypeInformation get doubleType {
    if (doubleTypeCache != null) return doubleTypeCache;
    return doubleTypeCache =
        getConcreteTypeFor(_abstractValueDomain.doubleType);
  }

  TypeInformation numTypeCache;
  TypeInformation get numType {
    if (numTypeCache != null) return numTypeCache;
    return numTypeCache = getConcreteTypeFor(_abstractValueDomain.numType);
  }

  TypeInformation boolTypeCache;
  TypeInformation get boolType {
    if (boolTypeCache != null) return boolTypeCache;
    return boolTypeCache = getConcreteTypeFor(_abstractValueDomain.boolType);
  }

  TypeInformation functionTypeCache;
  TypeInformation get functionType {
    if (functionTypeCache != null) return functionTypeCache;
    return functionTypeCache =
        getConcreteTypeFor(_abstractValueDomain.functionType);
  }

  TypeInformation listTypeCache;
  TypeInformation get listType {
    if (listTypeCache != null) return listTypeCache;
    return listTypeCache = getConcreteTypeFor(_abstractValueDomain.listType);
  }

  TypeInformation constListTypeCache;
  TypeInformation get constListType {
    if (constListTypeCache != null) return constListTypeCache;
    return constListTypeCache =
        getConcreteTypeFor(_abstractValueDomain.constListType);
  }

  TypeInformation fixedListTypeCache;
  TypeInformation get fixedListType {
    if (fixedListTypeCache != null) return fixedListTypeCache;
    return fixedListTypeCache =
        getConcreteTypeFor(_abstractValueDomain.fixedListType);
  }

  TypeInformation growableListTypeCache;
  TypeInformation get growableListType {
    if (growableListTypeCache != null) return growableListTypeCache;
    return growableListTypeCache =
        getConcreteTypeFor(_abstractValueDomain.growableListType);
  }

  TypeInformation mapTypeCache;
  TypeInformation get mapType {
    if (mapTypeCache != null) return mapTypeCache;
    return mapTypeCache = getConcreteTypeFor(_abstractValueDomain.mapType);
  }

  TypeInformation constMapTypeCache;
  TypeInformation get constMapType {
    if (constMapTypeCache != null) return constMapTypeCache;
    return constMapTypeCache =
        getConcreteTypeFor(_abstractValueDomain.constMapType);
  }

  TypeInformation stringTypeCache;
  TypeInformation get stringType {
    if (stringTypeCache != null) return stringTypeCache;
    return stringTypeCache =
        getConcreteTypeFor(_abstractValueDomain.stringType);
  }

  TypeInformation typeTypeCache;
  TypeInformation get typeType {
    if (typeTypeCache != null) return typeTypeCache;
    return typeTypeCache = getConcreteTypeFor(_abstractValueDomain.typeType);
  }

  TypeInformation dynamicTypeCache;
  TypeInformation get dynamicType {
    if (dynamicTypeCache != null) return dynamicTypeCache;
    return dynamicTypeCache =
        getConcreteTypeFor(_abstractValueDomain.dynamicType);
  }

  TypeInformation asyncFutureTypeCache;
  // Subtype of Future returned by async methods.
  TypeInformation get asyncFutureType {
    if (asyncFutureTypeCache != null) return asyncFutureTypeCache;
    return asyncFutureTypeCache =
        getConcreteTypeFor(_abstractValueDomain.asyncFutureType);
  }

  TypeInformation syncStarIterableTypeCache;
  TypeInformation get syncStarIterableType {
    if (syncStarIterableTypeCache != null) return syncStarIterableTypeCache;
    return syncStarIterableTypeCache =
        getConcreteTypeFor(_abstractValueDomain.syncStarIterableType);
  }

  TypeInformation asyncStarStreamTypeCache;
  TypeInformation get asyncStarStreamType {
    if (asyncStarStreamTypeCache != null) return asyncStarStreamTypeCache;
    return asyncStarStreamTypeCache =
        getConcreteTypeFor(_abstractValueDomain.asyncStarStreamType);
  }

  TypeInformation nonNullEmptyType;

  TypeInformation stringLiteralType(String value) {
    return new StringLiteralTypeInformation(
        _abstractValueDomain, value, _abstractValueDomain.stringType);
  }

  TypeInformation boolLiteralType(bool value) {
    return new BoolLiteralTypeInformation(
        _abstractValueDomain, value, _abstractValueDomain.boolType);
  }

  /**
   * Returns the least upper bound between [firstType] and
   * [secondType].
   */
  TypeInformation computeLUB(
      TypeInformation firstType, TypeInformation secondType) {
    if (firstType == null) return secondType;
    if (firstType == secondType) return firstType;
    if (firstType == nonNullEmptyType) return secondType;
    if (secondType == nonNullEmptyType) return firstType;
    if (firstType == dynamicType || secondType == dynamicType) {
      return dynamicType;
    }
    return getConcreteTypeFor(
        _abstractValueDomain.union(firstType.type, secondType.type));
  }

  /**
   * Returns `true` if `selector` should be updated to reflect the new
   * `receiverType`.
   */
  bool selectorNeedsUpdate(TypeInformation info, AbstractValue mask) {
    return info.type != mask;
  }

  /**
   * Returns a new receiver type for this [selector] applied to
   * [receiverType].
   *
   * The option [isConditional] is true when [selector] was seen in a
   * conditional send (e.g.  `a?.selector`), in which case the returned type may
   * be null.
   */
  TypeInformation refineReceiver(
      Selector selector, AbstractValue mask, TypeInformation receiver,
      {bool isConditional}) {
    if (_abstractValueDomain.isExact(receiver.type)) return receiver;
    AbstractValue otherType = _closedWorld.computeReceiverType(selector, mask);
    // Conditional sends (a?.b) can still narrow the possible types of `a`,
    // however, we still need to consider that `a` may be null.
    if (isConditional) {
      // Note: we don't check that receiver.type.isNullable here because this is
      // called during the graph construction.
      otherType = _abstractValueDomain.includeNull(otherType);
    }
    // If this is refining to nullable subtype of `Object` just return
    // the receiver. We know the narrowing is useless.
    if (_abstractValueDomain.canBeNull(otherType) &&
        _abstractValueDomain.containsAll(otherType)) {
      return receiver;
    }
    TypeInformation newType =
        new NarrowTypeInformation(_abstractValueDomain, receiver, otherType);
    allocatedTypes.add(newType);
    return newType;
  }

  /**
   * Returns the intersection between [type] and [annotation].
   * [isNullable] indicates whether the annotation implies a null
   * type.
   */
  TypeInformation narrowType(TypeInformation type, DartType annotation,
      {bool isNullable: true}) {
    if (annotation.treatAsDynamic) return type;
    if (annotation.isVoid) return type;
    AbstractValue otherType;
    if (annotation.isInterfaceType) {
      InterfaceType interface = annotation;
      if (interface.element == _closedWorld.commonElements.objectClass) {
        if (isNullable) {
          return type;
        }
        otherType = _abstractValueDomain.excludeNull(dynamicType.type);
      } else {
        otherType =
            _abstractValueDomain.createNonNullSubtype(interface.element);
      }
    } else if (annotation.isTypedef || annotation.isFunctionType) {
      otherType = functionType.type;
    } else if (annotation.isFutureOr) {
      // TODO(johnniwinther): Support narrowing of FutureOr.
      return type;
    } else {
      assert(annotation.isTypeVariable);
      // TODO(ngeoffray): Narrow to bound.
      return type;
    }
    if (isNullable) {
      otherType = _abstractValueDomain.includeNull(otherType);
    }
    if (_abstractValueDomain.isExact(type.type)) {
      return type;
    } else {
      TypeInformation newType =
          new NarrowTypeInformation(_abstractValueDomain, type, otherType);
      allocatedTypes.add(newType);
      return newType;
    }
  }

  /**
   * Returns the non-nullable type of [type].
   */
  TypeInformation narrowNotNull(TypeInformation type) {
    if (_abstractValueDomain.isExact(type.type)) {
      return type;
    }
    TypeInformation newType = new NarrowTypeInformation(_abstractValueDomain,
        type, _abstractValueDomain.excludeNull(dynamicType.type));
    allocatedTypes.add(newType);
    return newType;
  }

  ParameterTypeInformation getInferredTypeOfParameter(Local parameter) {
    return parameterTypeInformations.putIfAbsent(parameter, () {
      ParameterTypeInformation typeInformation =
          strategy.createParameterTypeInformation(
              _abstractValueDomain, parameter, this);
      _orderedTypeInformations.add(typeInformation);
      return typeInformation;
    });
  }

  MemberTypeInformation getInferredTypeOfMember(MemberEntity member) {
    assert(!member.isAbstract,
        failedAt(member, "Unexpected abstract member $member."));
    return memberTypeInformations.putIfAbsent(member, () {
      MemberTypeInformation typeInformation =
          strategy.createMemberTypeInformation(_abstractValueDomain, member);
      _orderedTypeInformations.add(typeInformation);
      return typeInformation;
    });
  }

  /**
   * Returns the internal inferrer representation for [mask].
   */
  ConcreteTypeInformation getConcreteTypeFor(AbstractValue mask) {
    assert(mask != null);
    return concreteTypes.putIfAbsent(mask, () {
      return new ConcreteTypeInformation(mask);
    });
  }

  String getInferredSignatureOfMethod(FunctionEntity function) {
    ElementTypeInformation info = getInferredTypeOfMember(function);
    var res = "";
    strategy.forEachParameter(function, (Local parameter) {
      TypeInformation type = getInferredTypeOfParameter(parameter);
      res += "${res.isEmpty ? '(' : ', '}${type.type} ${parameter.name}";
    });
    res += ") -> ${info.type}";
    return res;
  }

  TypeInformation nonNullSubtype(ClassEntity cls) {
    assert(strategy.checkClassEntity(cls));
    return getConcreteTypeFor(_abstractValueDomain.createNonNullSubtype(cls));
  }

  TypeInformation nonNullSubclass(ClassEntity cls) {
    assert(strategy.checkClassEntity(cls));
    return getConcreteTypeFor(_abstractValueDomain.createNonNullSubclass(cls));
  }

  TypeInformation nonNullExact(ClassEntity cls) {
    assert(strategy.checkClassEntity(cls));
    return getConcreteTypeFor(_abstractValueDomain.createNonNullExact(cls));
  }

  TypeInformation nonNullEmpty() {
    return nonNullEmptyType;
  }

  bool isNull(TypeInformation type) {
    return type == nullType;
  }

  TypeInformation allocateList(
      TypeInformation type, T node, MemberEntity enclosing,
      [TypeInformation elementType, int length]) {
    assert(strategy.checkListNode(node));
    ClassEntity typedDataClass = _closedWorld.commonElements.typedDataClass;
    bool isTypedArray = typedDataClass != null &&
        _closedWorld.isInstantiated(typedDataClass) &&
        _abstractValueDomain.isInstanceOfOrNull(type.type, typedDataClass);
    bool isConst = (type.type == _abstractValueDomain.constListType);
    bool isFixed = (type.type == _abstractValueDomain.fixedListType) ||
        isConst ||
        isTypedArray;
    bool isElementInferred = isConst || isTypedArray;

    int inferredLength = isFixed ? length : null;
    AbstractValue elementTypeMask =
        isElementInferred ? elementType.type : dynamicType.type;
    AbstractValue mask = _abstractValueDomain.createContainerValue(
        type.type, node, enclosing, elementTypeMask, inferredLength);
    ElementInContainerTypeInformation element =
        new ElementInContainerTypeInformation(
            _abstractValueDomain, currentMember, elementType);
    element.inferred = isElementInferred;

    allocatedTypes.add(element);
    return allocatedLists[node] = new ListTypeInformation(
        _abstractValueDomain, currentMember, mask, element, length);
  }

  /// Creates a [TypeInformation] object either for the closurization of a
  /// static or top-level method [element] used as a function constant or for
  /// the synthesized 'call' method [element] created for a local function.
  TypeInformation allocateClosure(FunctionEntity element) {
    TypeInformation result = new ClosureTypeInformation(
        _abstractValueDomain, currentMember, element);
    allocatedClosures.add(result);
    return result;
  }

  TypeInformation allocateMap(
      ConcreteTypeInformation type, T node, MemberEntity element,
      [List<TypeInformation> keyTypes, List<TypeInformation> valueTypes]) {
    assert(strategy.checkMapNode(node));
    assert(keyTypes.length == valueTypes.length);
    bool isFixed = (type.type == _abstractValueDomain.constMapType);

    AbstractValue keyType, valueType;
    if (isFixed) {
      keyType = keyTypes.fold(nonNullEmptyType.type,
          (type, info) => _abstractValueDomain.union(type, info.type));
      valueType = valueTypes.fold(nonNullEmptyType.type,
          (type, info) => _abstractValueDomain.union(type, info.type));
    } else {
      keyType = valueType = dynamicType.type;
    }
    AbstractValue mask = _abstractValueDomain.createMapValue(
        type.type, node, element, keyType, valueType);

    TypeInformation keyTypeInfo =
        new KeyInMapTypeInformation(_abstractValueDomain, currentMember, null);
    TypeInformation valueTypeInfo = new ValueInMapTypeInformation(
        _abstractValueDomain, currentMember, null);
    allocatedTypes.add(keyTypeInfo);
    allocatedTypes.add(valueTypeInfo);

    MapTypeInformation map =
        new MapTypeInformation(currentMember, mask, keyTypeInfo, valueTypeInfo);

    for (int i = 0; i < keyTypes.length; ++i) {
      TypeInformation newType = map.addEntryAssignment(
          _abstractValueDomain, keyTypes[i], valueTypes[i], true);
      if (newType != null) allocatedTypes.add(newType);
    }

    // Shortcut: If we already have a first approximation of the key/value type,
    // start propagating it early.
    if (isFixed) map.markAsInferred();

    allocatedMaps[node] = map;
    return map;
  }

  AbstractValue newTypedSelector(TypeInformation info, AbstractValue mask) {
    // Only type the selector if [info] is concrete, because the other
    // kinds of [TypeInformation] have the empty type at this point of
    // analysis.
    return info.isConcrete ? info.type : mask;
  }

  /**
   * Returns a new type that unions [firstInput] and [secondInput].
   */
  TypeInformation allocateDiamondPhi(
      TypeInformation firstInput, TypeInformation secondInput) {
    PhiElementTypeInformation<T> result = new PhiElementTypeInformation<T>(
        _abstractValueDomain, currentMember, null, null,
        isTry: false);
    result.addAssignment(firstInput);
    result.addAssignment(secondInput);
    allocatedTypes.add(result);
    return result;
  }

  PhiElementTypeInformation<T> _addPhi(
      T node, Local variable, TypeInformation inputType, bool isTry) {
    PhiElementTypeInformation<T> result = new PhiElementTypeInformation<T>(
        _abstractValueDomain, currentMember, node, variable,
        isTry: isTry);
    allocatedTypes.add(result);
    result.addAssignment(inputType);
    return result;
  }

  /**
   * Returns a new type for holding the potential types of [element].
   * [inputType] is the first incoming type of the phi.
   */
  PhiElementTypeInformation<T> allocatePhi(
      T node, Local variable, TypeInformation inputType,
      {bool isTry}) {
    assert(strategy.checkPhiNode(node));
    // Check if [inputType] is a phi for a local updated in
    // the try/catch block [node]. If it is, no need to allocate a new
    // phi.
    if (inputType is PhiElementTypeInformation &&
        inputType.branchNode == node &&
        inputType.isTry) {
      return inputType;
    }
    return _addPhi(node, variable, inputType, isTry);
  }

  /**
   * Returns a new type for holding the potential types of [element].
   * [inputType] is the first incoming type of the phi. [allocateLoopPhi]
   * only differs from [allocatePhi] in that it allows the underlying
   * implementation of [TypeSystem] to differentiate Phi nodes due to loops
   * from other merging uses.
   */
  PhiElementTypeInformation<T> allocateLoopPhi(
      T node, Local variable, TypeInformation inputType,
      {bool isTry}) {
    assert(strategy.checkLoopPhiNode(node));
    return _addPhi(node, variable, inputType, isTry);
  }

  /**
   * Simplies the phi representing [element] and of the type
   * [phiType]. For example, if this phi has one incoming input, an
   * implementation of this method could just return that incoming
   * input type.
   */
  TypeInformation simplifyPhi(
      T node, Local variable, PhiElementTypeInformation<T> phiType) {
    assert(phiType.branchNode == node);
    if (phiType.assignments.length == 1) return phiType.assignments.first;
    return phiType;
  }

  /**
   * Adds [newType] as an input of [phiType].
   */
  PhiElementTypeInformation<T> addPhiInput(Local variable,
      PhiElementTypeInformation<T> phiType, TypeInformation newType) {
    phiType.addAssignment(newType);
    return phiType;
  }

  AbstractValue computeTypeMask(Iterable<TypeInformation> assignments) {
    return joinTypeMasks(assignments.map((e) => e.type));
  }

  AbstractValue joinTypeMasks(Iterable<AbstractValue> masks) {
    var dynamicType = _abstractValueDomain.dynamicType;
    // Optimization: we are iterating over masks twice, but because `masks` is a
    // mapped iterable, we save the intermediate results to avoid computing them
    // again.
    var list = [];
    for (AbstractValue mask in masks) {
      // Don't do any work on computing unions if we know that after all that
      // work the result will be `dynamic`.
      // TODO(sigmund): change to `mask == dynamicType` so we can continue to
      // track the non-nullable bit.
      if (_abstractValueDomain.containsAll(mask)) return dynamicType;
      list.add(mask);
    }

    AbstractValue newType = null;
    for (AbstractValue mask in list) {
      newType =
          newType == null ? mask : _abstractValueDomain.union(newType, mask);
      // Likewise - stop early if we already reach dynamic.
      if (_abstractValueDomain.containsAll(newType)) return dynamicType;
    }

    return newType ?? _abstractValueDomain.emptyType;
  }
}