src/vs/base/browser/ui/tree/abstractTree.ts/AbstractTree/onRightArrow
class AbstractTree:	private onRightArrow(e: StandardKeyboardEvent): void {
		e.preventDefault();
		e.stopPropagation();

		const nodes = this.view.getFocusedElements();

		if (nodes.length === 0) {
			return;
		}

		const node = nodes[0];
		const location = this.model.getNodeLocation(node);
		const didChange = this.model.setCollapsed(location, false);

		if (!didChange) {
			if (!node.children.some(child => child.visible)) {
				return;
			}

			const [focusedIndex] = this.view.getFocus();
			const firstChildIndex = focusedIndex + 1;

			this.view.reveal(firstChildIndex);
			this.view.setFocus([firstChildIndex]);
		}
	}