pkg/compiler/lib/src/types/map_type_mask.dart

// Copyright (c) 2014, 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 [MapTypeMask] is a [TypeMask] for a specific allocation
 * site of a map (currently only internal Map class) that will get specialized
 * once the [TypeGraphInferrer] phase finds a key and/or value type for it.
 */
class MapTypeMask extends ForwardingTypeMask {
  final TypeMask forwardTo;

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

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

  // The value type of this map.
  final TypeMask valueType;

  // The key type of this map.
  final TypeMask keyType;

  MapTypeMask(this.forwardTo, this.allocationNode, this.allocationElement,
      this.keyType, this.valueType);

  TypeMask nullable() {
    return isNullable
        ? this
        : new MapTypeMask(forwardTo.nullable(), allocationNode,
            allocationElement, keyType, valueType);
  }

  TypeMask nonNullable() {
    return isNullable
        ? new MapTypeMask(forwardTo.nonNullable(), allocationNode,
            allocationElement, keyType, valueType)
        : this;
  }

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

  bool equalsDisregardNull(other) {
    if (other is! MapTypeMask) return false;
    return super.equalsDisregardNull(other) &&
        allocationNode == other.allocationNode &&
        keyType == other.keyType &&
        valueType == other.valueType;
  }

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

  TypeMask union(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.isMap &&
        keyType != null &&
        other.keyType != null &&
        valueType != null &&
        other.valueType != null) {
      TypeMask newKeyType = keyType.union(other.keyType, closedWorld);
      TypeMask newValueType = valueType.union(other.valueType, closedWorld);
      TypeMask newForwardTo = forwardTo.union(other.forwardTo, closedWorld);
      return new MapTypeMask(
          newForwardTo, null, null, newKeyType, newValueType);
    } else if (other.isDictionary) {
      // TODO(johnniwinther): Find another way to check this invariant that
      // doesn't need the compiler.
      assert(other.keyType ==
          new TypeMask.nonNullExact(
              closedWorld.backendClasses.stringImplementation, closedWorld));
      TypeMask newKeyType = keyType.union(other.keyType, closedWorld);
      TypeMask newValueType =
          other.typeMap.values.fold(keyType, (p, n) => p.union(n, closedWorld));
      TypeMask newForwardTo = forwardTo.union(other.forwardTo, closedWorld);
      MapTypeMask newMapTypeMask = new MapTypeMask(
          newForwardTo,
          allocationNode == other.allocationNode ? allocationNode : null,
          allocationElement == other.allocationElement
              ? allocationElement
              : null,
          newKeyType,
          newValueType);
      return newMapTypeMask;
    } else {
      return forwardTo.union(other, closedWorld);
    }
  }

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

  int get hashCode {
    return computeHashCode(
        allocationNode, isNullable, keyType, valueType, forwardTo);
  }

  String toString() {
    return 'Map mask: [$keyType/$valueType] type: $forwardTo';
  }
}