src/vs/editor/contrib/suggest/suggestAlternatives.ts/SuggestAlternatives/_move
class SuggestAlternatives:	private _move(fwd: boolean): void {
		if (!this._model) {
			// nothing to reason about
			return;
		}
		try {
			this._ignore = true;
			this._index = SuggestAlternatives._moveIndex(fwd, this._model, this._index);
			this._acceptNext!({ index: this._index, item: this._model.items[this._index], model: this._model });
		} finally {
			this._ignore = false;
		}
	}