public Builder mergeShape(org.box2d.proto.Box2D.PbShape value) {
        if (shapeBuilder_ == null) {
          if (((bitField0_ & 0x00000040) == 0x00000040) &&
              shape_ != org.box2d.proto.Box2D.PbShape.getDefaultInstance()) {
            shape_ =
              org.box2d.proto.Box2D.PbShape.newBuilder(shape_).mergeFrom(value).buildPartial();
          } else {
            shape_ = value;
          }
          onChanged();
        } else {
          shapeBuilder_.mergeFrom(value);
        }
        bitField0_ |= 0x00000040;
        return this;
      }