message: VertexMap uses IndexMap.
diff: /*---------------------------------------------------------------------------------------------
  | $Copyright: (c) 2018 Bentley Systems, Incorporated. All rights reserved. $
  *--------------------------------------------------------------------------------------------*/
  -import { SortedArray, Comparable, assert, compareWithTolerance } from "@bentley/bentleyjs-core";
  +import { IndexMap, Comparable, compare, assert, compareWithTolerance } from "@bentley/bentleyjs-core";
  import { Point2d } from "@bentley/geometry-core";
  import { QPoint3d, OctEncodedNormal } from "@bentley/imodeljs-common";
  @@ -63,10 +63,9 @@ export class VertexKey implements Comparable<VertexKey> {
  }
  }
  -function compareVertexKeys(lhs: VertexKey, rhs: VertexKey): number { return lhs.compare(rhs); }
  +export class VertexMap extends IndexMap<VertexKey> {
  + public constructor() { super(compare); }
  -export class VertexMap extends SortedArray<VertexKey> {
  - public constructor() { super(compareVertexKeys); }
  public add(position: QPoint3d, fillColor: number, normal?: OctEncodedNormal, uvParam?: Point2d): number {
  return this.insert(new VertexKey(position, fillColor, normal, uvParam));
  }
  