src/vs/workbench/contrib/debug/browser/watchExpressionsView.ts/WatchExpressionsDragAndDrop/getDragURI
class WatchExpressionsDragAndDrop:	getDragURI(element: IExpression): string | null {
		if (!(element instanceof Expression) || element === this.debugService.getViewModel().getSelectedExpression()) {
			return null;
		}

		return element.getId();
	}