Review

5

com/google/javascript/rhino/jstype/PrototypeObjectType.java

isSubtype(JSType)

class PrototypeObjectType {
  @Override
  public boolean isSubtype(JSType that) {
    if (JSType.isSubtype(this, that)) {
      return true;
    }

    // Union types
    if (that instanceof UnionType) {
      // The static {@code JSType.isSubtype} check already decomposed
      // union types, so we don't need to check those again.
      return false;
    }

    // record types
    if (that instanceof RecordType) {
      return RecordType.isSubtype(this, (RecordType) that);
    }

    // Interfaces
    // Find all the interfaces implemented by this class and compare each one
    // to the interface instance.
    ObjectType thatObj = that.toObjectType();
    ObjectType thatCtor = thatObj == null ? null : thatObj.getConstructor();
    if (thatCtor != null && thatCtor.isInterface()) {
      Iterable<ObjectType> thisInterfaces = getCtorImplementedInterfaces();
      for (ObjectType thisInterface : thisInterfaces) {
        if (thisInterface.isSubtype(that)) {
          return true;
        }
      }
    }

    // other prototype based objects
    if (that != null) {
      if (isUnknownType() || implicitPrototypeChainIsUnknown()) {
        // If unsure, say 'yes', to avoid spurious warnings.
        // TODO(user): resolve the prototype chain completely in all cases,
        // to avoid guessing.
        return true;
      }
      return this.isImplicitPrototype(thatObj);
    }

    return false;
  }

}