src/vs/workbench/browser/layout.ts/Layout/getVisibleNeighborPart
class Layout:	getVisibleNeighborPart(part: Parts, direction: Direction): Parts | undefined {
		if (!this.workbenchGrid) {
			return undefined;
		}

		if (!this.isVisible(part)) {
			return undefined;
		}

		const neighborViews = this.workbenchGrid.getNeighborViews(this.getPart(part), direction, false);

		if (!neighborViews) {
			return undefined;
		}

		for (const neighborView of neighborViews) {
			const neighborPart =
				[Parts.ACTIVITYBAR_PART, Parts.EDITOR_PART, Parts.PANEL_PART, Parts.SIDEBAR_PART, Parts.STATUSBAR_PART, Parts.TITLEBAR_PART]
					.find(partId => this.getPart(partId) === neighborView && this.isVisible(partId));

			if (neighborPart !== undefined) {
				return neighborPart;
			}
		}

		return undefined;
	}