pkg/compiler/lib/src/types/container_type_mask.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 masks;

/// A [ContainerTypeMask] is a [TypeMask] for a specific allocation
/// site of a container (currently only List) that will get specialized
/// once the [TypeGraphInferrer] phase finds an element type for it.
class ContainerTypeMask<T> extends ForwardingTypeMask {
  final TypeMask forwardTo;

  // The [Node] where this type mask was created.
  final T allocationNode;

  // The [Entity] where this type mask was created.
  final MemberEntity allocationElement;

  // The element type of this container.
  final TypeMask elementType;

  // The length of the container.
  final int length;

  ContainerTypeMask(this.forwardTo, this.allocationNode, this.allocationElement,
      this.elementType, this.length);

  TypeMask nullable() {
    return isNullable
        ? this
        : new ContainerTypeMask<T>(forwardTo.nullable(), allocationNode,
            allocationElement, elementType, length);
  }

  TypeMask nonNullable() {
    return isNullable
        ? new ContainerTypeMask<T>(forwardTo.nonNullable(), allocationNode,
            allocationElement, elementType, length)
        : this;
  }

  bool get isContainer => true;
  bool get isExact => true;

  bool equalsDisregardNull(other) {
    if (other is! ContainerTypeMask) return false;
    return super.equalsDisregardNull(other) &&
        allocationNode == other.allocationNode &&
        elementType == other.elementType &&
        length == other.length;
  }

  TypeMask intersection(TypeMask other, ClosedWorld closedWorld) {
    TypeMask forwardIntersection = forwardTo.intersection(other, closedWorld);
    if (forwardIntersection.isEmptyOrNull) return forwardIntersection;
    return forwardIntersection.isNullable ? nullable() : nonNullable();
  }

  TypeMask union(dynamic other, ClosedWorld closedWorld) {
    if (this == other) {
      return this;
    } else if (equalsDisregardNull(other)) {
      return other.isNullable ? other : this;
    } else if (other.isEmptyOrNull) {
      return other.isNullable ? this.nullable() : this;
    } else if (other.isContainer &&
        elementType != null &&
        other.elementType != null) {
      TypeMask newElementType =
          elementType.union(other.elementType, closedWorld);
      int newLength = (length == other.length) ? length : null;
      TypeMask newForwardTo = forwardTo.union(other.forwardTo, closedWorld);
      return new ContainerTypeMask<T>(
          newForwardTo,
          allocationNode == other.allocationNode ? allocationNode : null,
          allocationElement == other.allocationElement
              ? allocationElement
              : null,
          newElementType,
          newLength);
    } else {
      return forwardTo.union(other, closedWorld);
    }
  }

  bool operator ==(other) => super == other;

  int get hashCode {
    return computeHashCode(
        allocationNode, isNullable, elementType, length, forwardTo);
  }

  String toString() {
    return 'Container($forwardTo, element: $elementType, length: $length)';
  }
}